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><li>Sveinbjornsdottir, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+clinical+symptoms+of+Parkinson%27s+disease%5BTitle%5D)+AND+%22J.+Neurochem%22%5BJournal%5D)">The clinical symptoms of Parkinson's disease.</a> J. Neurochem. 139 (Suppl. 1), 318-324 (2016).</li>
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</ol>

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>&lt;strong&gt;Reagents&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Dulbecco&#039;s phosphate-buffered saline (DPBS)</td><td>homemade</td><td></td><td>150 mM NaCl, 8 mM Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;-12H&lt;sub&gt;2&lt;/sub&gt;O, 2.7 mM KCl, 1.5 mM KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4 &lt;/sub&gt;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&#039;s modified Eagle medium&lt;br/&gt; (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 &amp;deg;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&amp;rsquo;,N&amp;rsquo;-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>&amp;beta;-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 &amp;deg;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>&amp;beta;-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>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Antibodies&lt;/strong&gt;</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 &amp;mu;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.&lt;br/&gt; 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 &amp;mu;g/mL for immunoblotting.</td></tr><tr><td>anti-LRRK2 antibody</td><td>Abcam</td><td>ab133518</td><td>Used at 1 &amp;mu;g/mL for immunoblotting.</td></tr><tr><td>anti-&amp;alpha;-tubulin antibody</td><td>Sigma-Aldrich</td><td>T9026</td><td>Used at 1 &amp;mu;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 &amp;mu;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 &amp;mu;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 &amp;mu;g/mL for immunoblotting.</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Inhibitors&lt;/strong&gt;</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 &amp;deg;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 &amp;deg;C</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Plasmids&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Rab10/pcDNA5 FRT TO HA</td><td>Provided by Dr Dario Alessi&lt;br/&gt; (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&amp;ndash;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&amp;ndash;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&amp;ndash;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&amp;ndash;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&amp;ndash;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&amp;ndash;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&amp;ndash;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&amp;ndash;10975 (2013). This plasmid expresses amino-terminally 3xFLAG-tagged I2020T FPD mutant of human LRRK2.</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Equipments&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>CO&lt;sub&gt;2&lt;/sub&gt; 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&amp;ndash;10 &amp;mu;L</td></tr><tr><td>Micropipette P200</td><td>Nichiryo</td><td>00-NPX2-200</td><td>20&amp;ndash;200 &amp;mu;L</td></tr><tr><td>Micropipette P1000</td><td>Nichiryo</td><td>00-NPX2-1000</td><td>100&amp;ndash;1000 &amp;mu;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&amp;ndash;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&amp;ndash;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

15.0K Views.  The University of Tokyo. De huidige studie beschrijft een eenvoudige methode voor het opsporen van endogene niveaus van Rab10 fosforylering door leucine-rijke herhalen 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 ...

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 ...

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; ...

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.

The leucine rich repeat kinase 2 (LRRK2) is the most frequently mutated gene in hereditary Parkinson&#8217; disease (PD) and all pathogenic LRRK2 ...

Identification of Novel CK2 Kinase Substrates Using a Versatile Biochemical Approach

The study of kinase-substrate relationships is essential to gain a complete understanding of the functions of these enzymes and their downstream targets in both physiological and pathological states. CK2 is an evolutionarily conserved serine/threonine kinase with a growing list of hundreds of substrates involved in multiple cellular processes. Due to its pleiotropic properties, identifying and characterizing a comprehensive set of CK2 substrates has been particularly challenging and remains a hurdle in the study of this important enzyme. To address this challenge, we have devised a versatile experimental strategy that enables the targeted enrichment and identification of putative CK2 substrates. This protocol takes advantage of the unique dual co-substrate specificity of CK2 allowing for specific thiophosphorylation of its substrates in a cell or tissue lysate. These substrate proteins are subsequently alkylated, immunoprecipitated, and identified by liquid chromatography/tandem mass spectrometry (LC-MS/MS). We have previously used this approach to successfully identify CK2 substrates from Drosophila ovaries and here we extend the application of this protocol to human glioblastoma cells, illustrating the adaptability of this method to investigate the biological roles of this kinase in various model organisms and experimental systems.

The objective of this protocol is to label, enrich, and identify substrates of protein kinase CK2 from a complex biological sample such as a cell lysate or tissue homogenate. This method leverages unique aspects of CK2 biology for this purpose.

The study of kinase-substrate relationships is essential to gain a complete understanding of the functions of these enzymes and their downstream targets ...

Characterization at the Molecular Level using Robust Biochemical Approaches of a New Kinase Protein

Extensive whole genome sequencing has identified many Open Reading Frames (ORFs) providing many potential proteins. These proteins may have important roles for the cell and may unravel new cellular processes. Among proteins, kinases are major actors as they belong to cell signaling pathways and have the ability to switch on or off many processes crucial to the fate of the cell, such as cell growth, division, differentiation, motility, and death.
In this study, we focused on a new potential kinase protein, LIMK2-1. We demonstrated its existence by Western Blot using a specific antibody. We evaluated its interaction with an upstream regulating protein using coimmunoprecipitation experiments. Coimmunoprecipitation is a very powerful technique able to detect the interaction between two target proteins. It may also be used to detect new partners of a bait protein. The bait protein may be purified either via a tag engineered to its sequence or via an antibody specifically targeting it. These protein complexes may then be separated by SDS-PAGE (Sodium Dodecyl Sulfate PolyAcrylamide Gel) and identified using mass spectrometry. Immunoprecipitated LIMK2-1 was also used to test its kinase activity in vitro by &#947;[32P] ATP labeling. This well-established assay may use many different substrates, and mutated versions of the bait may be used to assess the role of specific residues. The effects of pharmacological agents may also be evaluated since this technique is both highly sensitive and quantitative. Nonetheless, radioactivity handling requires particular caution. Kinase activity may also be assessed with specific antibodies targeting the phospho group of the modified amino acid. These kinds of antibodies are not commercially available for all the phospho modified residues.

We characterized a new kinase protein using robust biochemical approaches: Western Blot analysis with a dedicated specific antibody on different cell lines and tissues, interactions by coimmunoprecipitation experiments, kinase activity detected by Western Blot using a phospho-specific antibody and by &#947;[32P] ATP labeling.

Extensive whole genome sequencing has identified many Open Reading Frames (ORFs) providing many potential proteins. These proteins may have important ...

Assaying the Kinase Activity of LRRK2 in vitro

Leucine Rich Repeat Kinase 2 (LRRK2) is a 2527 amino acid member of the ROCO family of proteins, possessing a complex, multidomain structure including a GTPase domain (termed ROC, for Ras of Complex proteins) and a kinase domain1. The discovery in 2004 of mutations in LRRK2 that cause Parkinson's disease (PD) resulted in LRRK2 being the focus of a huge volume of research into its normal function and how the protein goes awry in the disease state2,3. Initial investigations into the function of LRRK2 focused on its enzymatic activities4-6. Although a clear picture has yet to emerge of a consistent alteration in these due to mutations, data from a number of groups has highlighted the importance of the kinase activity of LRRK2 in cell death linked to mutations7,8. Recent publications have reported inhibitors targeting the kinase activity of LRRK2, providing a key experimental tool9-11. In light of these data, it is likely that the enzymatic properties of LRRK2 afford us an important window into the biology of this protein, although whether they are potential drug targets for Parkinson's is open to debate.
A number of different approaches have been used to assay the kinase activity of LRRK2. Initially, assays were carried out using epitope tagged protein overexpressed in mammalian cell lines and immunoprecipitated, with the assays carried out using this protein immobilised on agarose beads4,5,7. Subsequently, purified recombinant fragments of LRRK2 in solution have also been used, for example a GST tagged fragment purified from insect cells containing residues 970 to 2527 of LRRK212. Recently, Dani&euml;ls et al. reported the isolation of full length LRRK2 in solution from human embryonic kidney cells, however this protein is not widely available13. In contrast, the GST fusion truncated form of LRRK2 is commercially available (from Invitrogen, see table 1 for details), and provides a convenient tool for demonstrating an assay for LRRK2 kinase activity. Several different outputs for LRRK2 kinase activity have been reported. Autophosphorylation of LRRK2 itself, phosphorylation of Myelin Basic Protein (MBP) as a generic kinase substrate and phosphorylation of an artificial substrate - dubbed LRRKtide, based upon phosphorylation of threonine 558 in Moesin - have all been used, as have a series of putative physiological substrates including &alpha;-synuclein, Moesin and 4-EBP14-17. The status of these proteins as substrates for LRRK2 remains unclear, and as such the protocol described below will focus on using MBP as a generic substrate, noting the utility of this system to assay LRRK2 kinase activity directed against a range of potential substrates.

Assaying the Kinase Activity of LRRK2 in vitro

Leucine Rich Repeat Kinase 2 is a large multidomain kinase, mutations in which are the most common genetic cause of Parkinson's disease. Analysis of the kinase activity of this protein has proven to be a crucial tool in understanding the biology and dysfunction of this protein. In this paper, in vitro assaying of the kinase activity of LRRK2 and a selection of its mutants is described, providing an experimental system to examine phosphorylation of putative substrates and potential dysfunction of LRRK2 in disease.

Leucine Rich Repeat Kinase 2 (LRRK2) is a 2527 amino acid member of the ROCO family of proteins, possessing a complex, multidomain structure including a ...

Biology

Metabolic Labeling of Leucine Rich Repeat Kinases 1 and 2 with Radioactive Phosphate

Leucine rich repeat kinases 1 and 2 (LRRK1 and LRRK2) are paralogs which share a similar domain organization, including a serine-threonine kinase domain, a Ras of complex proteins domain (ROC), a C-terminal of ROC domain (COR), and leucine-rich and ankyrin-like repeats at the N-terminus. The precise cellular roles of LRRK1 and LRRK2 have yet to be elucidated, however LRRK1 has been implicated in tyrosine kinase receptor signaling1,2, while LRRK2 is implicated in the pathogenesis of Parkinson's disease3,4. In this report, we present a protocol to label the LRRK1 and LRRK2 proteins in cells with 32P orthophosphate, thereby providing a means to measure the overall phosphorylation levels of these 2 proteins in cells. In brief, affinity tagged LRRK proteins are expressed in HEK293T cells which are exposed to medium containing 32P-orthophosphate. The 32P-orthophosphate is assimilated by the cells after only a few hours of incubation and all molecules in the cell containing phosphates are thereby radioactively labeled. Via the affinity tag (3xflag) the LRRK proteins are isolated from other cellular components by immunoprecipitation. Immunoprecipitates are then separated via SDS-PAGE, blotted to PVDF membranes and analysis of the incorporated phosphates is performed by autoradiography (32P signal) and western detection (protein signal) of the proteins on the blots. The protocol can readily be adapted to monitor phosphorylation of any other protein that can be expressed in cells and isolated by immunoprecipitation.

Leucine rich repeat kinases 1 and 2 (LRRK1 and LRRK2) are multidomain proteins which encode both GTPase and kinase domains and which are phosphorylated in cells. Here, we present a protocol to label LRRK1 and LRRK2 in cells with 32P orthophosphate, thereby providing a means to measure their overall cellular phophorylation levels.

Leucine rich repeat kinases 1 and 2 (LRRK1 and LRRK2) are paralogs which share a similar domain organization, including a serine-threonine kinase domain, ...

A High Resolution Method to Monitor Phosphorylation-dependent Activation of IRF3

The IRF3 transcription factor is critical for the first line of defense against pathogens mainly through interferon &#946; and antiviral gene expression. A detailed analysis of IRF3 activation is essential to understand how pathogens induce or evade the innate antiviral response. Distinct activated forms of IRF3 can be distinguished based on their phosphorylation and monomer vs dimer status. In vivo discrimination between the different activated species of IRF3 can be achieved through the separation of IRF3 phosphorylated forms based on their mobility shifts on SDS-PAGE. Additionally, the levels of IRF3 monomer and dimer can be monitored using non-denaturing electrophoresis. Here, we detail a procedure to reach the highest resolution to gain the most information regarding IRF3 activation status. This is achieved through the combination of a high resolution SDS-PAGE and a native-PAGE coupled to immunoblots using multiple total and phosphospecific antibodies. This experimental strategy constitutes an affordable and sensitive approach to acquire all the necessary information for a complete analysis of the phosphorylation-mediated activation of IRF3.

Here we describe a procedure allowing a detailed analysis of the phosphorylation-dependent activation of the IRF3 transcription factor. This is achieved through the combination of a high resolution SDS-PAGE and a native-PAGE coupled to immunoblots using multiple phosphospecific antibodies.

The IRF3 transcription factor is critical for the first line of defense against pathogens mainly through interferon &#946; and antiviral gene expression. ...

Single-Molecule Pull-Down Assay for Protein Phosphorylation Analysis: A High Throughput Technique to Quantify Protein Phosphorylation in Cell Lysate

Source: Bailey, E. M. et al., <a href="https://www.jove.com/v/63665">An Optimized Single-Molecule Pull-Down Assay for Quantification of Protein Phosphorylation.</a> J. Vis. Exp. (2022)
This video demonstrates a sensitive quantification technique of protein phosphorylation using a single-molecule pull-down assay. The functionalization of polyethylene glycol-biotin and the use of labeled antibodies increases the detection of phosphorylated tyrosine with specificity.

Source: Bailey, E. M. et al., An Optimized Single-Molecule Pull-Down Assay for Quantification of Protein Phosphorylation. J. Vis. Exp. (2022)
This video ...

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

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