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Quantification of PtdInsP3 molecular species in cells and tissues by mass spectrometry

2011; Nature Portfolio; Volume: 8; Issue: 3 Linguagem: Inglês

10.1038/nmeth.1564

1548-7105

Jonathan Clark, Karen E. Anderson, Véronique Juvin, Trevor Smith, Fredrik Karpe, Michael J.O. Wakelam, Len Stephens, Phillip T. Hawkins,

Pharmacogenetics and Drug Metabolism

By methylating the phosphate groups of PtdIns(3,4,5)P3 researchers can load this lipid more efficiently into a mass spectrometer and thus this lipid can be quantified in the presence of an internal synthetic standard. Class I phosphoinositide-3-kinase (PI3K) isoforms generate the intracellular signaling lipid, phosphatidylinositol(3,4,5)trisphosphate (PtdIns(3,4,5)P3). PtdIns(3,4,5)P3 regulates major aspects of cellular behavior, and the use of both genetic and pharmacological intervention has revealed important isoform-specific roles for PI3Ks in health and disease. Despite this interest, current methods for measuring PtdIns(3,4,5)P3 have major limitations, including insensitivity, reliance on radiolabeling, low throughput and an inability to resolve different fatty-acyl species. We introduce a methodology based on phosphate methylation coupled to high-performance liquid chromatography–mass spectrometry (HPLC-MS) to solve many of these problems and describe an integrated approach to quantify PtdIns(3,4,5)P3 and related phosphoinositides (regio-isomers of PtdInsP and PtdInsP2 are not resolved). This methodology can be used to quantify multiple fatty-acyl species of PtdIns(3,4,5)P3 in unstimulated mouse and human cells (≥105) or tissues (≥0.1 mg) and their increase upon appropriate stimulation.