Name: radiolabeling and quantification of cellular levels of phosphoinositides by high performance liquid chromatography-coupled flow scintillation
Uploaded: 2016-01-06T14:00:01
Description: Watch this Scientific Journal Video about Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation at JoVE.com

C.Y.H. was supported by an Ontario Graduate Scholarship from the Government of Ontario. This article was made possible by funding held by R.J.B. from the Natural Sciences and Engineering Research Council, the Canada Research Chairs Program and Ryerson University.

Obs: Texten nedan beskriver i detalj en metod för att mäta PtdInsPs i jäst. Det ger experimentella detaljer för märkning av jästceller med 3 H- myo-inositol, utvinna och deacylera lipider och en HPLC-elueringsprotokollet att fraktionera och kvantifiera deacylerade PtdInsPs. Observera att märkning, deacylering, upplösning och kvantifiering av PtdInsPs i däggdjursceller kräver optimering och längre HPLC-elueringsprofiler. Dessa uppgifter kan hittas någon annanstans, även om vi diskutera n?...

Den här artikeln detaljer experimentprotokollet som krävs för att kvantifiera cellulära nivåer av PtdnsPs med HPLC kopplade flödes scintillation från jäst. Metodiken möjliggör den metaboliska märkningen av PtdInsPs med 3 H- myo-inositol, följt av lipid bearbetning och utvinning av vattenlösligt 3 H-Gro-InsPs, HPLC-fraktionering och analys. Med denna metod, kan de relativa nivåerna av PtdInsPs i celler under olika betingelser kvantifieras, som visas för PtdIns (3,5) P 2<...

Phosphoinositides (PtdInsPs) are important signaling phospholipids that help regulate a variety of cellular functions, including signal transduction, membrane trafficking and gene expression, which then modulate higher-order cell behavior such as cell division, organelle identity and metabolic activity1-3. There are seven species of PtdInsPs that are derived from the phosphorylation of the 3, 4, and/or 5 positions of the inositol head group of phosphatidylinositol (PtdIns), the parent phospholipid. Importantly, the seven PtdInsPs are unequally distributed and the local concentration of each PtdInsP species can increase or decrease at specific subcellular sites where they bind to a distinct set of protein effectors, which together permits each PtdInsP to control the identity and function of its host membrane3,4. In addition, the levels of each PtdInsP need to be tightly controlled since this can significantly impact the signal intensityproduced by a PtdInsP. The localization and levels of each PtdInsP depends on the targeting and activity of numerous lipid kinases, phosphatases and phospholipases that mediate the synthesis and turnover of each PtdInsP3,4. Hence, misregulation of the PtdInsP regulatory machinery can perturb cell function, leading to diseases such as cancer and degenerative diseases2,5,6. To fully understand the roles and functions of PtdInsPs and their regulatory machinery, both microscopy-based and biochemical-based techniques have been developed to track and quantify PtdInsPs. 
In many cases, PtdInsPs bind to their protein effectors via a specific protein domain7-9. These protein modules often retain their proper fold and lipid recognition properties when expressed separately from the entire protein. This gave rise to PtdInsP probes by fusing a specific PtdInsP-binding protein domain to a fluorescent protein (FP) like green fluorescent protein (GFP) for the subcellular detection of PtdInsPs by microscopy. Indeed, many studies have used FP-fused PtdInsP-binding protein modules to identify the localization and dynamics of specific PtdInsP species by live-cell imaging1,10. For example, the Pleckstrin homology (PH) domain of phospholipase C &#948;1 (PLC&#948;1) fused to GFP specifically recognizes the phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] on the plasma membrane, whereas tandem copies of the FYVE domain of early endosome antigen 1 (EEA1) has been employed to track phosphatidylinositol-3-phosphate (PtdIns3P) on endosomes10-13. Overall, microscopy-based techniques are great to visualize PtdInsP localization and dynamics, but there are several caveats including that PtdInsP-binding domains may also interact with additional factors other than the target PtdInsP species and that they cannot detect changes below cytosolic fluorescence of the FP-probes.
Biochemical techniques including thin-layer chromatography, mass spectrometry and radioisotope labeling can also be used to characterize and quantify the levels of each PtdInsP14-16. These methods require the isolation of lipids for the detection of cellular levels of PtdInsPs. Mass spectrometry can be used to characterize phospholipids from lipid extracts and is invaluable for determining the acyl chain composition of PtdInsPs14,17. However, mass spectrometry is mostly semi-quantitative and it remains difficult to resolve and concurrently quantify PtdInsP species of the same molecular weight14,17. In comparison, radioisotope labeling of PtdInsPs followed by high performance liquid chromatography (HPLC)-coupled flow scintillation is useful for the separation and concurrent quantification of all seven species of PtdInsPs18. The use of HPLC with a strong anion exchange (SAX) column achieves separation based on molecular weight, charge and shape, thus fractionating deacylated PtdInsPs (Gro-InsPs) even of the same molecular weight and charge. Coupling the HPLC eluent to a flow scintillator then generates radioactive-based signal peaks for each Gro-InsPs species relative to the original parent glycerol-inositol (Gro-Ins)18. This ultimately corresponds to relative levels of PtdInsPs in cells.
Radiolabeling of PtdInsPs and HPLC-coupled flow scintillation is a useful tool to investigate the regulation and function of phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P2], a PtdInsP that only constitutes ~0.1-0.3% of PtdIns16,19,20. Synthesis of PtdIns(3,5)P2 is performed by the PtdIns3P 5-kinase called Fab1 in yeast and PIKfyve in mammals21. This reaction is counteracted by a PtdIns(3,5)P2 5-phosphatase called Fig4 in yeast or mFig4/Sac3 in mammals22-24. Interestingly, both PIKfyve/Fab1 and mFig4/Fig4/Sac3 exist in a single complex and are regulated by the scaffolding adaptor protein, Vac14 in yeast or mVac14/ArPIKfyve in mammals25,26. In VAC14-deleted yeast cells, Fab1 does not function efficiently leading to a 90% decrease in PtdIns(3,5)P2 levels27,28. On the other hand, Atg18 is a PtdIns(3,5)P2 effector protein that may control vacuolar fission 29. Atg18 is also a negative regulator of PtdIns(3,5)P2 since the deletion of its gene, ATG18, causes a 10 to 20-fold increase in PtdIns(3,5)P2 levels29,30. Overall, changes in the levels of PtdIns(3,5)P2 severely impacts the function of the yeast vacuole and the mammalian lysosomes, consequently affecting processes such as membrane trafficking, phagosome maturation, autophagy and ion transport 6,19,21,31. 
This article describes the process of radioisotope labeling of PtdInsPs with 3H-myo-inositol in yeast to detect the relative levels of PtdIns(3,5)P2 in wild-type, vac14&#916; and atg18&#916; yeast strains. Using this as an example, the resolving capabilities of HPLC for the separation of individual PtdInsPs as well as the sensitivity of flow scintillation for detection of trace amount of 3H-myo-inositol is shown. We also elaborate on how one might optimize the methodology for labeling and separating 3H-labelled PtdInsPs from mammalian cells, whose samples tend to be more complex since these cells possess all seven PtdInsP species.

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radiolabeling and quantification of cellular levels of phosphoinositides by high performance liquid chromatography-coupled flow scintillation

Phosphoinositides (PtdInsPs) are essential signaling lipids responsible for recruiting specific effectors and conferring organelles with molecular identity and function. Each of the seven PtdInsPs varies in their distribution and abundance, which are tightly regulated by specific kinases and phosphatases. The abundance of PtdInsPs can change abruptly in response to various signaling events or disturbance of the regulatory machinery. To understand how these events lead to changes in the amount of PtdInsPs and their resulting impact, it is important to quantify PtdInsP levels before and after a signaling event or between control and abnormal conditions. However, due to their low abundance and similarity, quantifying the relative amounts of each PtdInsP can be challenging. This article describes a method for quantifying PtdInsP levels by metabolically labeling cells with 3H-myo-inositol, which is incorporated into PtdInsPs. Phospholipids are then precipitated and deacylated. The resulting soluble 3H-glycero-inositides are further extracted, separated by high-performance liquid chromatography (HPLC), and detected by flow scintillation. The labeling and processing of yeast samples is described in detail, as well as the instrumental setup for the HPLC and flow scintillator. Despite losing structural information regarding acyl chain content, this method is sensitive and can be optimized to concurrently quantify all seven PtdInsPs in cells.

Med denna metod, har jäst PtdInsPs metaboliskt märkt med 3 H- myo-inositol. Efter märkning, har fosfolipiderna utfälldes med perklorsyra, följt av fosfolipid deacylering och extraktion av den vattenlösliga Gro-InsPs (Figur 1). I detta skede är det viktigt att kvantifiera det totala radioaktiva signalen associerad med den extraherade Gro-InsPs genom vätskescintillation för att säkerställa tillräcklig signal-brusförhållande för de låg-ab...

Watch this Scientific Journal Video about Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation at JoVE.com

Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation

Fosfoinositider signalerar lipider vars relativa överflöd snabbt ändras som svar på olika stimuli. I den här artikeln beskrivs en metod för att mäta förekomsten av fosfoinositider genom metaboliskt märknings celler med 3 H- myo-inositol, följt av extraktion och deacylering. Extraherade glycero-inositides separeras sedan genom HPLC och kvantifieras av flödes scintillation.

Radiomärkning och kvantifiering av cellulära nivåerna av fosfoinositider från High Performance Liquid Chromatography kopplade Flow Scintillation

Phosphoinositides (PtdInsPs) are essential signaling lipids responsible for recruiting specific effectors and conferring organelles with molecular ...

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En enkel metod för glukosinolater Extraktion och analys med Högtrycks vätskekromatografi (HPLC)

Glucosinolates are a well-studied and highly diverse class of natural plant compounds. They play important roles in plant resistance, rapeseed oil ...

A Convenient Method for Extraction and Analysis with High-Pressure Liquid Chromatography of Catecholamine Neurotransmitters and Their Metabolites

En behändig metod för extraktion och analys med vätskekromatografi högtrycks av katekolamin signalsubstanser och deras metaboliter

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and ...