We thank Dr. Takeshi Iwatsubo (University of Tokyo, Japan) for kindly providing the plasmids encoding 3xFLAG-LRRK2 WT and mutants. We also thank Dr. Dario Alessi (University of Dundee, UK) for kindly providing MLi-2 and the plasmid encoding HA-Rab10. This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number JP17K08265 (G.I.).

<ol>
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Neurochem. 139 (Suppl. 1), 59-74 (2016).</li><li>Pais&#225;n-Ru&#237;z, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cloning+of+the+gene+containing+mutations+that+cause+PARK8-linked+Parkinson's+disease.">Cloning of the gene containing mutations that cause PARK8-linked Parkinson's disease.</a> Neuron. 44 (4), 595-600 (2004).</li><li>Zimprich, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mutations+in+LRRK2+cause+autosomal-dominant+parkinsonism+with+pleomorphic+pathology.">Mutations in LRRK2 cause autosomal-dominant parkinsonism with pleomorphic pathology.</a> Neuron. 44 (4), 601-607 (2004).</li><li>Gilks, W. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+common+LRRK2+mutation+in+idiopathic+Parkinson's+disease.">A common LRRK2 mutation in idiopathic Parkinson's disease.</a> Lancet. 365 (9457), 415-416 (2005).</li><li>Satake, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-wide+association+study+identifies+common+variants+at+four+loci+as+genetic+risk+factors+for+Parkinson's+disease.">Genome-wide association study identifies common variants at four loci as genetic risk factors for Parkinson's disease.</a> Nat. 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The authors have nothing to disclose.

Here, we describe a facile and robust method of detecting Rab10 phosphorylation by LRRK2 at endogenous levels based on the P-tag methodology. Because the currently available antibody against phosphorylated Rab10 works only with overexpressed proteins15, the present method utilizing P-tag SDS-PAGE is the only way to assess endogenous levels of Rab10 phosphorylation. Moreover, the present method allows the estimation of the stoichiometry of Rab10 phosphorylation in cells. Because the P-tag methodolo...

PD is one of the most common neurodegenerative diseases, predominantly affecting dopaminergic neurons in the midbrain, resulting in dysfunction of the motor systems in elderly people1. While most patients develop PD in a sporadic manner, there are families inheriting the disease. Mutations in several genes have been found to be linked with FPD2. One of the causative genes for FPD is LRRK2, in which eight missense mutations (N1437H, R1441C/G/H/S, Y1699C, G2019S, and I2020T) linked to a dominantly inherited FPD called PARK8 have so far been reported3,4,5. Several genome-wide association studies (GWAS) of sporadic PD patients have also identified genomic variations at the LRRK2 locus as a risk factor for PD, suggesting that abnormality in the function of LRRK2 is a common cause of neurodegeneration in both sporadic and PARK8 FPD6,7,8.
LRRK2 is a large protein (2,527 amino acids) consisting of a leucine-rich repeat domain, a GTP-binding Ras of complex proteins (ROC) domain, a C-terminal of ROC (COR) domain, a serine/threonine protein kinase domain, and a WD40 repeat domain9. The eight FPD mutations locate in these functional domains; N1437H and R1441C/G/H/S in the ROC domain, Y1699C in the COR domain, G2019S and I2020T in the kinase domain. Since G2019S mutation, which is the most frequently found mutation in PD patients10,11,12, increases the kinase activity of LRRK2 by 2 - 3 fold in vitro13, it is hypothesized that the abnormal increase in phosphorylation of LRRK2 substrate(s) is toxic to neurons. However, it has been impossible to study whether the phosphorylation of physiologically relevant LRRK2 substrates is altered in familial/sporadic PD patients due to the lack of methods evaluating it in patient derived samples.
Protein phosphorylation is generally detected by immunoblotting or enzyme-linked immunosorbent assay (ELISA) using antibodies specifically recognizing the phosphorylated state of proteins or by mass spectrometric analysis. However, the former strategy sometimes cannot be applied because of the difficulties in creating phosphorylation-specific antibodies. Metabolic labeling of cells with radioactive phosphate is another option to examine physiological levels of phosphorylation when phosphorylation-specific antibodies are not readily available. However, it requires a large amount of radioactive materials and therefore involves some specialized equipment for radioprotection14. Mass spectrometric analysis is more sensitive compared to these immunochemical methods and became popular in analyzing protein phosphorylation. However, the sample preparation is time-consuming, and expensive instruments are required for the analysis.
A subset of the Rab GTPase family including Rab10 and Rab8 was recently reported as direct physiological substrates for LRRK2 based on the result of a large-scale phosphoproteomic analysis15. We then demonstrated that Rab10 phosphorylation was increased by FPD mutations in mouse embryonic fibroblasts and in the lungs of knockin mice16. In this report, we chose to employ a sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE)-based method in which a P-tag molecule is co-polymerized into SDS-PAGE gels (P-tag SDS-PAGE) for detecting the endogenous levels of Rab10 phosphorylation, because a highly sensitive antibody specific for phosphorylated Rab10 was still lacking. We have failed to detect the phosphorylation of endogenous Rab8 due to the poor selectivity of currently available antibodies for total Rab8. Therefore, we decided to focus on the Rab10 phosphorylation. LRRK2 phosphorylates Rab10 at Thr73 locating at the middle of the highly conserved &#34;switch II&#34; region. High conservation of the phosphorylation sites among Rab proteins might be one of the reasons why phosphospecific antibodies recognizing distinct Rab proteins are difficult to make.
The phosphorylation of Rab8A by LRRK2 inhibits the binding of Rabin8, a guanine nucleotide exchange factor (GEF) which activates Rab8A by exchanging the bound GDP with GTP15. Phosphorylation of Rab10 and Rab8A by LRRK2 also inhibits the binding of GDP-dissociation inhibitors (GDIs), which are essential to the activation of Rab proteins by extracting GDP-bound Rab proteins from membranes15. Collectively, it is hypothesized that the phosphorylation of Rab proteins by LRRK2 prevents them from activation although the precise molecular mechanism and physiological consequences of the phosphorylation remain unclear.
P-tag SDS-PAGE was invented by Kinoshita et al. in 2006: In this method, acrylamide was covalently coupled with P-tag, a molecule capturing phosphates with high affinity, which copolymerized into SDS-PAGE gels17. Because the P-tag molecules in a SDS-PAGE gel selectively retard electrophoretic mobility of phosphorylated proteins, P-tag SDS-PAGE can separate phosphorylated proteins from non-phosphorylated ones (Figure 1). If the protein-of-interest is phosphorylated on multiple residues, a ladder of bands corresponding to differentially phosphorylated forms will be observed. In the case of Rab10, we observe only one shifted band, indicating that Rab10 is phosphorylated only at Thr73. The major advantage of P-tag SDS-PAGE over immunoblotting with phosphorylation-specific antibodies is that phosphorylated Rab10 can be detected by immunoblotting with non-phosphorylation-specific antibodies (i.e., recognizing total Rab10) after being transferred on membranes, which is generally more specific, sensitive, and available from commercial/academic sources. Another advantage of using P-tag SDS-PAGE is that one can obtain approximate estimation of the stoichiometry of phosphorylation, which is impossible by immunoblotting with phosphorylation-specific antibodies or by metabolic labeling of cells with radioactive phosphates.
Apart from the use of inexpensive P-tag acrylamide and some minor modifications related to it, the present method for detection of Rab10 phosphorylation by LRRK2 follows a general protocol of immunoblotting. Therefore, it should be straightforward and easily executable in any laboratories where immunoblotting is a usual practice, with any types of samples including purified proteins, cell lysates, and tissue homogenates.

<table>
	<tbody>
		<tr>
			<td>Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate-buffered saline (DPBS)</td>
			<td>homemade</td>
			<td></td>
			<td>150 mM NaCl, 8 mM Na2HPO4-12H2O, 2.7 mM KCl, 1.5 mM KH2PO4 in MilliQ water and sterilized by autoclaving</td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Nacalai Tesque</td>
			<td>31320-34</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Disodium Hydrogenphosphate 12-Water</td>
			<td>Wako</td>
			<td>196-02835</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium chloride</td>
			<td>Wako</td>
			<td>163-03545</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Dihydrogen Phosphate</td>
			<td>Wako</td>
			<td>169-04245</td>
			<td></td>
		</tr>
		<tr>
			<td>2.5% Trypsin (10X)</td>
			<td>Sigma-Aldrich</td>
			<td>T4549</td>
			<td>Dilute 10-fold with sterile DPBS for preparing working solution</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s modified Eagle medium 
			(DMEM)</td>
			<td>Wako</td>
			<td>044-29765</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>BioWest</td>
			<td>S1560</td>
			<td>Heat-inactivated at 56 &#176;C for 30 min</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin (100X)</td>
			<td>Wako</td>
			<td>168-23191</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Wako</td>
			<td>342-01375</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Wako</td>
			<td>198-13765</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylenimine HCl MAX, Linear, Mw 40,000 (PEI MAX 40000)</td>
			<td>PolySciences, Inc.</td>
			<td>24765-1</td>
			<td>Stock solution was prepared in 20 mM HEPES-NaOH pH 7.0 at 1 mg/mL and the pH was then adjusted to 7.0 with NaOH</td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide</td>
			<td>Wako</td>
			<td>045-28335</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris</td>
			<td>STAR</td>
			<td>RSP-THA500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>Wako</td>
			<td>080-01066</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyoxyethylene(10) Octylphenyl Ether</td>
			<td>Wako</td>
			<td>160-24751</td>
			<td>Equivalent to Triton X-100</td>
		</tr>
		<tr>
			<td>Ethylene glycol-bis(2-aminoethylether)-N,N,N&#8217;,N&#8217;-tetraacetic acid (EGTA)</td>
			<td>Wako</td>
			<td>346-01312</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium orthovanadate(V)</td>
			<td>Wako</td>
			<td>198-09752</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium fluoride</td>
			<td>Kanto Chemical</td>
			<td>37174-20</td>
			<td></td>
		</tr>
		<tr>
			<td>&#946;-Glycerophosphoric Acid Disodium Salt Pentahydrate</td>
			<td>Nacalai Tesque</td>
			<td>17103-82</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium pyrophosphate decahydrate</td>
			<td>Kokusan Chemical</td>
			<td>2113899</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcystin-LR</td>
			<td>Wako</td>
			<td>136-12241</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Wako</td>
			<td>196-00015</td>
			<td></td>
		</tr>
		<tr>
			<td>Complete EDTA-free protease inhibitor cocktail</td>
			<td>Roche</td>
			<td>11873580001</td>
			<td>Dissolve one tablet in 1 mL water, which can be stored at -20 &#176;C for a month. Use it at 1:50 dilution for cell lysis</td>
		</tr>
		<tr>
			<td>Pierce Coomassie (Bradford) Protein Assay Kit</td>
			<td>Thermo Fisher Scientific</td>
			<td>23200</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dodecyl sulfate</td>
			<td>Nacalai Tesque</td>
			<td>31607-65</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Wako</td>
			<td>075-00616</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>Wako</td>
			<td>021-02911</td>
			<td></td>
		</tr>
		<tr>
			<td>&#946;-mercaptoethanol</td>
			<td>Kanto Chemical</td>
			<td>25099-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Wako</td>
			<td>056-06967</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Wako</td>
			<td>136-01837</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate-binding tag acrylamide</td>
			<td>Wako</td>
			<td>AAL-107</td>
			<td>P-tag acrylamide</td>
		</tr>
		<tr>
			<td>40% (w/v) acrylamide solution</td>
			<td>Nacalai Tesque</td>
			<td>06119-45</td>
			<td>Acrylamide:Bis = 29:1</td>
		</tr>
		<tr>
			<td>Tetramethylethylenediamine (TEMED)</td>
			<td>Nacalai Tesque</td>
			<td>33401-72</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium persulfate (APS)</td>
			<td>Wako</td>
			<td>016-08021</td>
			<td>10% (w/v) solution was prepared by dissolving the powder of ammonium persulfate in MilliQ water</td>
		</tr>
		<tr>
			<td>2-propanol</td>
			<td>Wako</td>
			<td>166-04831</td>
			<td></td>
		</tr>
		<tr>
			<td>Manganese chloride tetrahydrate</td>
			<td>Sigma-Aldrich</td>
			<td>M3634</td>
			<td></td>
		</tr>
		<tr>
			<td>Precision Plus Protein Prestained Standard</td>
			<td>Bio-Rad</td>
			<td>1610374, 1610373, 1610377</td>
			<td>Molecular weight marker used in the protocol</td>
		</tr>
		<tr>
			<td>WIDE-VIEW Prestained Protein Size Marker III</td>
			<td>Wako</td>
			<td>230-02461</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Nacalai Tesque</td>
			<td>17109-64</td>
			<td></td>
		</tr>
		<tr>
			<td>Amersham Protran NC 0.45</td>
			<td>GE Healthcare</td>
			<td>10600007</td>
			<td>Nitrocellulose membrane</td>
		</tr>
		<tr>
			<td>Durapore Membrane Filter</td>
			<td>EMD Millipore</td>
			<td>GVHP00010</td>
			<td>PVDF membrane</td>
		</tr>
		<tr>
			<td>Filter Papers No.1</td>
			<td>Advantec</td>
			<td>00013600</td>
			<td></td>
		</tr>
		<tr>
			<td>Ponceau S</td>
			<td>Nacalai Tesque</td>
			<td>28322-72</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Wako</td>
			<td>017-00251</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween-20</td>
			<td>Sigma-Aldrich</td>
			<td>P1379</td>
			<td>polyoxyethylenesorbitan monolaurate</td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic acid (EDTA)</td>
			<td>Wako</td>
			<td>345-01865</td>
			<td></td>
		</tr>
		<tr>
			<td>Skim milk powder</td>
			<td>Difco Laboratories</td>
			<td>232100</td>
			<td></td>
		</tr>
		<tr>
			<td>Immunostar</td>
			<td>Wako</td>
			<td>291-55203</td>
			<td>ECL solution (Normal sensitivity)</td>
		</tr>
		<tr>
			<td>Immunostar LD</td>
			<td>Wako</td>
			<td>290-69904</td>
			<td>ECL solution (High sensitivity)</td>
		</tr>
		<tr>
			<td>CBB staining solution</td>
			<td>homemade</td>
			<td></td>
			<td>1 g CBB R-250, 50% (v/v) methanol, 10% (v/v) acetic acid in 1 L of MilliQ water</td>
		</tr>
		<tr>
			<td>CBB R-250</td>
			<td>Wako</td>
			<td>031-17922</td>
			<td></td>
		</tr>
		<tr>
			<td>CBB destaining solution</td>
			<td>homemade</td>
			<td></td>
			<td>12% (v/v) methanol, 7% (v/v) acetic acid in 1 L MilliQ water</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Antibodies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>anti-HA antibody</td>
			<td>Sigma-Aldrich</td>
			<td>11583816001</td>
			<td>Used at 0.2 &#956;g/mL for immunoblotting.</td>
		</tr>
		<tr>
			<td>anti-Rab10 antibody</td>
			<td>Cell Signaling Technology</td>
			<td>#8127</td>
			<td>Used at 1:1000 for immunoblotting. 
			Specificity was confirmed by CRISPR KO in Ito et al., Biochem J, 2016.</td>
		</tr>
		<tr>
			<td>anti-pSer935 antibody</td>
			<td>Abcam</td>
			<td>ab133450</td>
			<td>Used at 1 &#956;g/mL for immunoblotting.</td>
		</tr>
		<tr>
			<td>anti-LRRK2 antibody</td>
			<td>Abcam</td>
			<td>ab133518</td>
			<td>Used at 1 &#956;g/mL for immunoblotting.</td>
		</tr>
		<tr>
			<td>anti-&#945;-tubulin antibody</td>
			<td>Sigma-Aldrich</td>
			<td>T9026</td>
			<td>Used at 1 &#956;g/mL for immunoblotting.</td>
		</tr>
		<tr>
			<td>anti-GAPDH antibody</td>
			<td>Santa-Cruz</td>
			<td>sc-32233</td>
			<td>Used at 0.02 &#956;g/mL for immunoblotting.</td>
		</tr>
		<tr>
			<td>Peroxidase AffiniPure Sheep Anti-Mouse IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>515-035-003</td>
			<td>Used at 0.16 &#956;g/mL for immunoblotting.</td>
		</tr>
		<tr>
			<td>Peroxidase AffiniPure Goat Anti-Rabbit IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>111-035-003</td>
			<td>Used at 0.16 &#956;g/mL for immunoblotting.</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Inhibitors</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>GSK2578215A</td>
			<td>MedChem Express</td>
			<td>HY-13237</td>
			<td>Stock solution was prepared in DMSO at 10 mM and stored at -80 &#176;C</td>
		</tr>
		<tr>
			<td>MLi-2</td>
			<td>Provided by Dr Dario Alessi (University of Dundee)</td>
			<td></td>
			<td>Stock solution was prepared in DMSO at 10 mM and stored at -80 &#176;C</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Plasmids</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rab10/pcDNA5 FRT TO HA</td>
			<td>Provided by Dr Dario Alessi 
			(University of Dundee)</td>
			<td></td>
			<td>This plasmid expresses amino-terminally HA-tagged human Rab10.</td>
		</tr>
		<tr>
			<td>LRRK2 WT/p3xFLAG-CMV-10</td>
			<td>Provided by Dr Takeshi Iwatsubo (University of Tokyo)</td>
			<td></td>
			<td>Ito et al., Biochemistry, 46: 1380&#8211;1388 (2007). This plasmid expresses amino-terminally 3xFLAG-tagged wild-type human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 K1906M/p3xFLAG-CMV-10</td>
			<td>Provided by Dr Takeshi Iwatsubo (University of Tokyo)</td>
			<td></td>
			<td>Ito et al., Biochemistry, 46: 1380&#8211;1388 (2007). This plasmid expresses amino-terminally 3xFLAG-tagged K1906M kinase-inactive mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 N1437H/p3xFLAG-CMV-10</td>
			<td></td>
			<td></td>
			<td>This paper. This plasmid expresses amino-terminally 3xFLAG-tagged N1437H FPD mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 R1441C/p3xFLAG-CMV-10</td>
			<td>Provided by Dr Takeshi Iwatsubo (University of Tokyo)</td>
			<td></td>
			<td>Kamikawaji et al., Biochemistry, 48: 10963&#8211;10975 (2013). This plasmid expresses amino-terminally 3xFLAG-tagged R1441C FPD mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 R1441G/p3xFLAG-CMV-10</td>
			<td>Provided by Dr Takeshi Iwatsubo (University of Tokyo)</td>
			<td></td>
			<td>Kamikawaji et al., Biochemistry, 48: 10963&#8211;10975 (2013). This plasmid expresses amino-terminally 3xFLAG-tagged R1441G FPD mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 R1441H/p3xFLAG-CMV-10</td>
			<td>Provided by Dr Takeshi Iwatsubo (University of Tokyo)</td>
			<td></td>
			<td>Kamikawaji et al., Biochemistry, 48: 10963&#8211;10975 (2013). This plasmid expresses amino-terminally 3xFLAG-tagged R1441H FPD mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 R1441S/p3xFLAG-CMV-10</td>
			<td></td>
			<td></td>
			<td>This paper. This plasmid expresses amino-terminally 3xFLAG-tagged R1441S FPD mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 Y1699C/p3xFLAG-CMV-10</td>
			<td>Provided by Dr Takeshi Iwatsubo (University of Tokyo)</td>
			<td></td>
			<td>Kamikawaji et al., Biochemistry, 48: 10963&#8211;10975 (2013). This plasmid expresses amino-terminally 3xFLAG-tagged Y1699C FPD mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 G2019S/p3xFLAG-CMV-10</td>
			<td>Provided by Dr Takeshi Iwatsubo (University of Tokyo)</td>
			<td></td>
			<td>Kamikawaji et al., Biochemistry, 48: 10963&#8211;10975 (2013). This plasmid expresses amino-terminally 3xFLAG-tagged G2019S FPD mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>LRRK2 I2020T/p3xFLAG-CMV-10</td>
			<td>Provided by Dr Takeshi Iwatsubo (University of Tokyo)</td>
			<td></td>
			<td>Kamikawaji et al., Biochemistry, 48: 10963&#8211;10975 (2013). This plasmid expresses amino-terminally 3xFLAG-tagged I2020T FPD mutant of human LRRK2.</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Equipments</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 incubator</td>
			<td>Thermo Fisher Scientific</td>
			<td>Forma Series II 3110 Water-Jacketed</td>
			<td></td>
		</tr>
		<tr>
			<td>Auto Pipette</td>
			<td>Drummond</td>
			<td>Pipet-Aid PA-400</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipette P10</td>
			<td>Nichiryo</td>
			<td>00-NPX2-10</td>
			<td>0.5&#8211;10 &#956;L</td>
		</tr>
		<tr>
			<td>Micropipette P200</td>
			<td>Nichiryo</td>
			<td>00-NPX2-200</td>
			<td>20&#8211;200 &#956;L</td>
		</tr>
		<tr>
			<td>Micropipette P1000</td>
			<td>Nichiryo</td>
			<td>00-NPX2-1000</td>
			<td>100&#8211;1000 &#956;L</td>
		</tr>
		<tr>
			<td>Tips for micropipette P10</td>
			<td>STAR</td>
			<td>RST-481LCRST</td>
			<td>Sterile</td>
		</tr>
		<tr>
			<td>Tips for micropipette P200</td>
			<td>FUKAEKASEI</td>
			<td>1201-705YS</td>
			<td>Sterile</td>
		</tr>
		<tr>
			<td>Tips for micropipette P1000</td>
			<td>STAR</td>
			<td>RST-4810BRST</td>
			<td>Sterile</td>
		</tr>
		<tr>
			<td>5 mL disporsable pipette</td>
			<td>Greiner</td>
			<td>606180</td>
			<td>Sterile</td>
		</tr>
		<tr>
			<td>10 mL disporsable pipette</td>
			<td>Greiner</td>
			<td>607180</td>
			<td>Sterile</td>
		</tr>
		<tr>
			<td>25 mL disporsable pipette</td>
			<td>Falcon</td>
			<td>357535</td>
			<td>Sterile</td>
		</tr>
		<tr>
			<td>Hematocytometer</td>
			<td>Sunlead Glass</td>
			<td>A126</td>
			<td>Improved Neubeuer</td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Olympus</td>
			<td>CKX53</td>
			<td></td>
		</tr>
		<tr>
			<td>10 cm dishes</td>
			<td>Falcon</td>
			<td>353003</td>
			<td>For tissue culture</td>
		</tr>
		<tr>
			<td>6-well plates</td>
			<td>AGC Techno Glass</td>
			<td>3810-006</td>
			<td>For tissue culture</td>
		</tr>
		<tr>
			<td>Vortex mixer</td>
			<td>Scientific Industries</td>
			<td>Vortex-Genie 2</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell scrapers</td>
			<td>Sumitomo Bakelite</td>
			<td>MS-93100</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 mL tubes</td>
			<td>STAR</td>
			<td>RSV-MTT1.5</td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL tubes</td>
			<td>AGC Techno Glass</td>
			<td>2323-015</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL tubes</td>
			<td>AGC Techno Glass</td>
			<td>2343-050</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuges</td>
			<td>TOMY</td>
			<td>MX-307</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well plates</td>
			<td>Greiner</td>
			<td>655061</td>
			<td>Not for tissue culture</td>
		</tr>
		<tr>
			<td>Plate reader</td>
			<td>Molecular Devices</td>
			<td>SpectraMax M2e</td>
			<td></td>
		</tr>
		<tr>
			<td>SDS&#8211;PAGE tanks</td>
			<td>Nihon Eido</td>
			<td>NA-1010</td>
			<td></td>
		</tr>
		<tr>
			<td>Transfer tanks</td>
			<td>Nihon Eido</td>
			<td>NA-1510B</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel plates (notched)</td>
			<td>Nihon Eido</td>
			<td>NA-1000-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel plates (plain)</td>
			<td>Nihon Eido</td>
			<td>NA-1000-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Silicon spacers</td>
			<td>Nihon Eido</td>
			<td>NA-1000-16</td>
			<td></td>
		</tr>
		<tr>
			<td>17-well combs</td>
			<td>Nihon Eido</td>
			<td>Custom made</td>
			<td></td>
		</tr>
		<tr>
			<td>Binder clips</td>
			<td>Nihon Eido</td>
			<td>NA-1000-15</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL syringe</td>
			<td>Terumo</td>
			<td>SS-05SZ</td>
			<td></td>
		</tr>
		<tr>
			<td>21G</td>
			<td>Terumo</td>
			<td>NN-2138R</td>
			<td></td>
		</tr>
		<tr>
			<td>Power Station 1000 VC</td>
			<td>ATTO</td>
			<td>AE-8450</td>
			<td>Power supply for SDS&#8211;PAGE and transfer</td>
		</tr>
		<tr>
			<td>Large weighing boats</td>
			<td>Ina Optika</td>
			<td>AS-DL</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic containers</td>
			<td>AS ONE</td>
			<td>PS CASE No.4</td>
			<td>10 x 80 x 50 mm</td>
		</tr>
		<tr>
			<td>Rocking shaker</td>
			<td>Titech</td>
			<td>NR-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Styrene foam box</td>
			<td>generic</td>
			<td></td>
			<td>The internal dimensions should fit one transfer tank (200 x 250 x 250 mm).</td>
		</tr>
		<tr>
			<td>ImageQuant LAS-4000</td>
			<td>GE Healthcare</td>
			<td></td>
			<td>An imager equipped with a cooled CCD camera for detection of ECL</td>
		</tr>
	</tbody>
</table>

rab10 phosphorylation detection by lrrk2 activity using sds-page with a phosphate-binding tag

Mutations in leucine-rich repeat kinase 2 (LRRK2) have been shown to be linked with familial Parkinson&#39;s disease (FPD). Since abnormal activation of the kinase activity of LRRK2 has been implicated in the pathogenesis of PD, it is essential to establish a method to evaluate the physiological levels of the kinase activity of LRRK2. Recent studies revealed that LRRK2 phosphorylates members of the Rab GTPase family, including Rab10, under physiological conditions. Although the phosphorylation of endogenous Rab10 by LRRK2 in cultured cells could be detected by mass spectrometry, it has been difficult to detect it by immunoblotting due to the poor sensitivity of currently available phosphorylation-specific antibodies for Rab10. Here, we describe a simple method of detecting the endogenous levels of Rab10 phosphorylation by LRRK2 based on immunoblotting utilizing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) combined with a phosphate-binding tag (P-tag), which is N-(5-(2-aminoethylcarbamoyl)pyridin-2-ylmetyl)-N,N&#39;,N&#39;-tris(pyridin-2-yl-methyl)-1,3-diaminopropan-2-ol. The present protocol not only provides an example of the methodology utilizing the P-tag but also enables the assessment of how mutations as well as inhibitor treatment/administration or any other factors alter the downstream signaling of LRRK2 in cells and tissues.

Overexpression System: Phosphorylation of HA-Rab10 by 3&#215;FLAG-LRRK2 in HEK293 Cells:
HEK293 cells were transfected with 0.266 &#181;g of HA-Rab10 wild-type and 1.066 &#181;g of 3&#215;FLAG-LRRK2 (wild-type, kinase-inactive mutant (K1906M), or FPD mutants). Rab10 phosphorylation was examined by P-tag SDS-PAGE followed by immunoblotting using an anti-HA antibody (Figure 2). 10 &#181;g of proteins wer...

Watch this Scientific Journal Video about Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag at JoVE.com

Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag

The present study describes a simple method of detecting endogenous levels of Rab10 phosphorylation by leucine-rich repeat kinase 2.

Mutations in leucine-rich repeat kinase 2 (LRRK2) have been shown to be linked with familial Parkinson&#39;s disease (FPD). Since abnormal activation of ...

rab10-phosphorylation-detection-lrrk2-activity-using-sds-page-with

Research

JoVE Journal

Biochemistry

14.8K Views.  The University of Tokyo. The present study describes a simple method of detecting endogenous levels of Rab10 phosphorylation by leucine-rich repeat kinase 2.

Video: Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag

Highly Sensitive and Rapid Fluorescence Detection with a Portable FRET Analyzer

Recent improvements in F&#246;rster resonance energy transfer (FRET) sensors have enabled their use to detect various small molecules including ions and amino acids. However, the innate weak signal intensity of FRET sensors is a major challenge that prevents their application in various fields and makes the use of expensive, high-end fluorometers necessary. Previously, we built a cost-effective, high-performance FRET analyzer that can specifically measure the ratio of two emission wavelength bands (530 and 480 nm) to achieve high detection sensitivity. More recently, it was discovered that FRET sensors with bacterial periplasmic binding proteins detect ligands with maximum sensitivity in the critical temperature range of 50 - 55 &#176;C. This report describes a protocol for assessing sugar content in commercially-available beverage samples using our portable FRET analyzer with a temperature-specific FRET sensor. Our results showed that the additional preheating process of the FRET sensor significantly increases the FRET ratio signal, to enable more accurate measurement of sugar content. The custom-made FRET analyzer and sensor were successfully applied to quantify the sugar content in three types of commercial beverages. We anticipate that further size reduction and performance enhancement of the equipment will facilitate the use of hand-held analyzers in environments where high-end equipment is not available.

This protocol describes the rapid and highly sensitive quantification of F&#246;rster resonance energy transfer (FRET) sensor data using a custom-made portable FRET analyzer. The device was used to detect maltose within a critical temperature range that maximizes detection sensitivity, enabling practical and efficient assessment of sugar content.

Recent improvements in F&#246;rster resonance energy transfer (FRET) sensors have enabled their use to detect various small molecules including ions and ...

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo

Bacteria are frequently exposed to environmental changes, such as alterations in pH, temperature, redox status, light exposure or mechanical force. Many of these conditions cause protein unfolding in the cell and have detrimental impact on the survival of the organism. A group of unrelated, stress-specific molecular chaperones have been shown to play essential roles in the survival of these stress conditions. While fully folded and chaperone-inactive before stress, these proteins rapidly unfold and become chaperone-active under specific stress conditions. Once activated, these conditionally disordered chaperones bind to a large number of different aggregation-prone proteins, prevent their aggregation and either directly or indirectly facilitate protein refolding upon return to non-stress conditions. The primary approach for gaining a more detailed understanding about the mechanism of their activation and client recognition involves the purification and subsequent characterization of these proteins using in vitro chaperone assays. Follow-up in vivo stress assays are absolutely essential to independently confirm the obtained in vitro results.
This protocol describes in vitro and in vivo methods to characterize the chaperone activity of E. coli HdeB, an acid-activated chaperone. Light scattering measurements were used as a convenient read-out for HdeB&#39;s capacity to prevent acid-induced aggregation of an established model client protein, MDH, in vitro. Analytical ultracentrifugation experiments were applied to reveal complex formation between HdeB and its client protein LDH, to shed light into the fate of client proteins upon their return to non-stress conditions. Enzymatic activity assays of the client proteins were conducted to monitor the effects of HdeB on pH-induced client inactivation and reactivation. Finally, survival studies were used to monitor the influence of HdeB&#39;s chaperone function in vivo.

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo

This study describes biophysical, biochemical and molecular techniques to characterize the chaperone activity of Escherichia coli HdeB under acidic pH conditions. These methods have been successfully applied for other acid-protective chaperones such as HdeA and can be modified to work for other chaperones and stress conditions.

Bacteria are frequently exposed to environmental changes, such as alterations in pH, temperature, redox status, light exposure or mechanical force. Many ...

Assaying Protein Kinase Activity with Radiolabeled ATP

Protein kinases are able to govern large-scale cellular changes in response to complex arrays of stimuli, and much effort has been directed at uncovering allosteric details of their regulation. Kinases comprise signaling networks whose defects are often hallmarks of multiple forms of cancer and related diseases, making an assay platform amenable to manipulation of upstream regulatory factors and validation of reaction requirements critical in the search for improved therapeutics. Here, we describe a basic kinase assay that can be easily adapted to suit specific experimental questions including but not limited to testing the effects of biochemical and pharmacological agents, genetic manipulations such as mutation and deletion, as well as cell culture conditions and treatments to probe cell signaling mechanisms. This assay utilizes radiolabeled [&#947;-32P] ATP, which allows for quantitative comparisons and clear visualization of results, and can be modified for use with immunoprecipitated or recombinant kinase, specific or typified substrates, all over a wide range of reaction conditions.

Protein kinases are highly evolved signaling enzymes and scaffolds that are critical for inter- and intracellular signal transduction. We present a protocol for measuring kinase activity through the use of radiolabeled adenosine triphosphate ([&#947;-32P] ATP), a reliable method to aid in elucidation of cellular signaling regulation.

Protein kinases are able to govern large-scale cellular changes in response to complex arrays of stimuli, and much effort has been directed at uncovering ...

Oligopeptide Competition Assay for Phosphorylation Site Determination

Protein phosphorylation at specific sites determines its conformation and interaction with other molecules. Thus, protein phosphorylation affects biological functions and characteristics of the cell. Currently, the most common method for discovering phosphorylation sites is by liquid chromatography/mass spectrometry (LC/MS) analysis, a rapid and sensitive method. However, relatively labile phosphate moieties are often released from phosphopeptides during the fragmentation step, which often yields false-negative signals. In such cases, a traditional in vitro kinase assay using site-directed mutants would be more accurate, but this method is laborious and time-consuming. Therefore, an alternative method using peptide competition may be advantageous. The consensus recognition motif of 5&#39; adenosine monophosphate-activated protein kinase (AMPK) has been established1 and was validated using a positional scanning peptide library assay2. Thus, AMPK phosphorylation sites for a novel substrate could be predicted and confirmed by the peptide competition assays. In this report, we describe the detailed steps and procedures for the in vitro oligopeptide-competing kinase assay by illustrating AMPK-mediated nuclear factor erythroid 2-related factor 2 (Nrf2) phosphorylation. To authenticate the phosphorylation site, we carried out a sequential in vitro kinase assay using a site-specific mutant. Overall, the peptide competition assay provides a method to screen multiple potential phosphorylation sites and to identify sites for validation by the phosphorylation site mutants.

Peptide competition assays are widely used in a variety of molecular and immunological experiments. This paper describes a detailed method for an in vitro oligopeptide-competing kinase assay and the associated validation procedures, which may be useful to find specific phosphorylation sites.

Protein phosphorylation at specific sites determines its conformation and interaction with other molecules. Thus, protein phosphorylation affects ...

DNA Polymerase Activity Assay Using Near-infrared Fluorescent Labeled DNA Visualized by Acrylamide Gel Electrophoresis

For any enzyme, robust, quantitative methods are required for characterization of both native and engineered enzymes. For DNA polymerases, DNA synthesis can be characterized using an in vitro DNA synthesis assay followed by polyacrylamide gel electrophoresis. The goal of this assay is to quantify synthesis of both natural DNA and modified DNA (M-DNA). These approaches are particularly useful for resolving oligonucleotides with single nucleotide resolution, enabling observation of individual steps during enzymatic oligonucleotide synthesis. These methods have been applied to the evaluation of an array of biochemical and biophysical properties such as the measurement of steady-state rate constants of individual steps of DNA synthesis, the error rate of DNA synthesis, and DNA binding affinity. By using modified components including, but not limited to, modified nucleoside triphosphates (NTP), M-DNA, and/or mutant DNA polymerases, the relative utility of substrate-DNA polymerase pairs can be effectively evaluated. Here, we detail the assay itself, including the changes that must be made to accommodate nontraditional primer DNA labeling strategies such as near-infrared fluorescently labeled DNA. Additionally, we have detailed crucial technical steps for acrylamide gel pouring and running, which can often be technically challenging.

This protocol describes the characterization of DNA polymerase synthesis of modified DNA through observation of changes to near-infrared fluorescently labeled DNA using gel electrophoresis and gel imaging. Acrylamide gels are used for high resolution imaging of the separation of short nucleic acids, which migrate at different rates depending on size.

For any enzyme, robust, quantitative methods are required for characterization of both native and engineered enzymes. For DNA polymerases, DNA synthesis ...

Detection of Small GTPase Prenylation and GTP Binding Using Membrane Fractionation and  GTPase-linked Immunosorbent Assay

The Rho GTPase family belongs to the Ras superfamily and includes approximately 20 members in humans. Rho GTPases are important in the regulation of diverse cellular functions, including cytoskeletal dynamics, cell motility, cell polarity, axonal guidance, vesicular trafficking, and cell cycle control. Changes in Rho GTPase signaling play an essential regulatory role in many pathological conditions, such as&#160;cancer, central nervous system diseases, and immune system-dependent diseases. The posttranslational modification of Rho GTPases (i.e., prenylation by mevalonate pathway intermediates) and GTP binding are key factors which affect the activation of this protein. In this paper, two essential and simple methods are provided to detect a broad range of Rho GTPase prenylation and GTP binding activities. Details of the technical procedures that have been used are explained step by step in this manuscript.

Here we describe a protocol to investigate the prenylation and guanosine-5'-triphosphate (GTP)-loading of Rho GTPase. This protocol consists of two detailed methods, namely membrane fractionation and a GTPase-linked immunosorbent assay. The protocol can be used for measuring the prenylation and GTP loading of different other small GTPases.

The Rho GTPase family belongs to the Ras superfamily and includes approximately 20 members in humans. Rho GTPases are important in the regulation of ...

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Cyclin-dependent kinase 1 (Cdk1) is a master controller for the cell cycle in all eukaryotes and phosphorylates an estimated 8 - 13% of the proteome; however, the number of identified targets for Cdk1, particularly in human cells is still low. The identification of Cdk1-specific phosphorylation sites is important, as they provide mechanistic insights into how Cdk1 controls the cell cycle. Cell cycle regulation is critical for faithful chromosome segregation, and defects in this complicated process lead to chromosomal aberrations and cancer.
Here, we describe an in vitro kinase assay that is used to identify Cdk1-specific phosphorylation sites. In this assay, a purified protein is phosphorylated in vitro by commercially available human Cdk1/cyclin B. Successful phosphorylation is confirmed by SDS-PAGE, and phosphorylation sites are subsequently identified by mass spectrometry. We also describe purification protocols that yield highly pure and homogeneous protein preparations suitable for the kinase assay, and a binding assay for the functional verification of the identified phosphorylation sites, which probes the interaction between a classical nuclear localization signal (cNLS) and its nuclear transport receptor karyopherin &#945;. To aid with experimental design, we review approaches for the prediction of Cdk1-specific phosphorylation sites from protein sequences. Together these protocols present a very powerful approach that yields Cdk1-specific phosphorylation sites and enables mechanistic studies into how Cdk1 controls the cell cycle. Since this method relies on purified proteins, it can be applied to any model organism and yields reliable results, especially when combined with cell functional studies.

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Cyclin-dependent kinase 1 (Cdk1) is activated in the G2 phase of the cell cycle and regulates many cellular pathways. Here, we present a protocol for an in vitro kinase assay with Cdk1, which allows the identification of Cdk1-specific phosphorylation sites for establishing cellular targets of this important kinase.

Cyclin-dependent kinase 1 (Cdk1) is a master controller for the cell cycle in all eukaryotes and phosphorylates an estimated 8 - 13% of the proteome; ...

Detection of Phospholipase C Activity in the Brain Homogenate from the Honeybee

The honeybee is a model organism for evaluating complex behaviors and higher brain function, such as learning, memory, and division of labor. The mushroom body (MB) is a higher brain center proposed to be the neural substrate of complex honeybee behaviors. Although previous studies identified genes and proteins that are differentially expressed in the MBs and other brain regions, the activities of the proteins in each region are not yet fully understood. To reveal the functions of these proteins in the brain, pharmacologic analysis is a feasible approach, but it is first necessary to confirm that pharmacologic manipulations indeed alter the protein activity in these brain regions.
We previously identified a higher expression of genes encoding phospholipase C (PLC) in the MBs than in other brain regions, and pharmacologically assessed the involvement of PLC in honeybee behavior. In that study, we biochemically tested two pharmacologic agents and confirmed that they decreased PLC activity in the MBs and other brain regions. Here, we present a detailed description of how to detect PLC activity in honeybee brain homogenate. In this assay system, homogenates derived from different brain regions are reacted with a synthetic fluorogenic substrate, and fluorescence resulting from PLC activity is quantified and compared between brain regions. We also describe our evaluation of the inhibitory effects of certain drugs on PLC activity using the same system. Although this system is likely affected by other endogenous fluorescence compounds and/or the absorbance of the assay components and tissues, the measurement of PLC activity using this system is safer and easier than that using the traditional assay, which requires radiolabeled substrates. The simple procedure and manipulations allow us to examine PLC activity in the brains and other tissues of honeybees involved in different social tasks.

To test the inhibitory effects of pharmacologic agents on phospholipase C (PLC) in different regions of the honeybee brain, we present a biochemical assay to measure PLC activity in those regions. This assay could be useful for comparing PLC activity among tissues, as well as among bees exhibiting different behaviors.

The honeybee is a model organism for evaluating complex behaviors and higher brain function, such as learning, memory, and division of labor. The mushroom ...

Affinity Purification of Chloroplast Translocon Protein Complexes Using the TAP Tag

Chloroplast biogenesis requires the import of thousands of nucleus-encoded proteins into the plastid. The import of these proteins depends on the translocon at the outer (TOC) and inner (TIC) chloroplast membranes. The TOC and TIC complexes are multimeric and probably contain yet unknown components. One of the main goals in the field is to establish the complete inventory of TOC and TIC components. For the isolation of TOC-TIC complexes and the identification of new components, the preprotein receptor TOC159 has been modified N-terminally by the addition of the tandem affinity purification (TAP) tag resulting in TAP-TOC159. The TAP-tag is designed for two sequential affinity purification steps (hence "tandem affinity"). The TAP-tag used in these studies consists of a N-terminal IgG-binding domain derived from Staphylococcus aureus Protein A (ProtA) followed by a calmodulin-binding peptide (CBP). Between these two affinity tags, a tobacco etch virus (TEV) protease cleavage site has been included. Therefore, TEV protease can be used for gentle elution of TOC159-containing complexes after binding to IgG beads. In the protocol presented here, the second Calmodulin-affinity purification step was omitted. The purification protocol starts with the preparation and solubilization of total cellular membranes. After the detergent-treatment, the solubilized membrane proteins are incubated with IgG beads for the immunoisolation of TAP-TOC159-containing complexes. Upon binding and extensive washing, TAP-TOC159 containing complexes are cleaved and released from the IgG beads using the TEV protease whereby the S. aureus IgG-binding domain is removed. Western blotting of the isolated TOC159-containing complexes can be used to confirm the presence of known or suspected TOC and TIC proteins. More importantly, the TOC159-containing complexes have been used successfully to identify new components of the TOC and TIC complexes by mass spectrometry. The protocol that we present potentially allows the efficient isolation of any membrane-bound protein complex to be used for the identification of yet unknown components by mass spectrometry.

We here present a proven and tested protocol for the purification of chloroplast protein import complexes (TOC-TIC complex) using the TAP-tag. The one-step affinity-isolation protocol can potentially be applied to any protein and be used to identify new interaction partners by mass spectrometry.

Chloroplast biogenesis requires the import of thousands of nucleus-encoded proteins into the plastid. The import of these proteins depends on the ...

Human Peripheral Blood Neutrophil Isolation for Interrogating the Parkinson's Associated LRRK2 Kinase Pathway by Assessing Rab10 Phosphorylation

The leucine rich repeat kinase 2 (LRRK2) is the most frequently mutated gene in hereditary Parkinson&#8217; disease (PD) and all pathogenic LRRK2 mutations result in hyperactivation of its kinase function. Here, we describe an easy and robust assay to quantify LRRK2 kinase pathway activity in human peripheral blood neutrophils by measuring LRRK2-controlled phosphorylation of one of its physiological substrates, Rab10 at threonine 73. The immunoblotting analysis described requires a fully selective and phosphospecific antibody that recognizes the Rab10 Thr73 epitope phosphorylated by LRRK2, such as the MJFF-pRab10 rabbit monoclonal antibody. It uses human peripheral blood neutrophils, because peripheral blood is easily accessible and neutrophils are an abundant and homogenous constituent. Importantly, neutrophils express relatively high levels of both LRRK2 and Rab10. A potential drawback of neutrophils is their high intrinsic serine protease activity, which necessitates the use of very potent protease inhibitors such as the organophosphorus neurotoxin diisopropylfluorophosphate (DIFP) as part of the lysis buffer. Nevertheless, neutrophils are a valuable resource for research into LRRK2 kinase pathway activity in vivo and should be considered for inclusion into PD biorepository collections.

Mutations in the leucine rich repeat kinase 2 gene (LRRK2) cause hereditary Parkinson&#8217;s disease. We have developed an easy and robust method for assessing LRRK2-controlled phosphorylation of Rab10 in human peripheral blood neutrophils. This may help identify individuals with increased LRRK2 kinase pathway activity.