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Updated: Jun 18, 2026

Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation
Published on: January 6, 2016
Structure and function of phosphatidylinositol-3,4 kinase
M Funaki1, H Katagiri, K Inukai
1The Institute for Adult Disease, Asahi Life Foundation 1-9-14, Nishi-Shinjuku, Shinjuku-Ward, Japan.
Phosphatidylinositol (PI)-kinase, crucial for cellular activity, signals through both D-3 and D-4 phosphorylated phosphoinositides. Its catalytic and regulatory subunits exhibit distinct functions and activation pathways.
Area of Science:
- Cellular Biology
- Molecular Signaling
- Enzymology
Background:
- Phosphatidylinositol (PI)-kinase regulates diverse cellular activities.
- The enzyme comprises catalytic (p110alpha, p110beta) and regulatory (p85, p55, p50) subunits.
- Isoform diversity in regulatory subunits influences binding, localization, and activation of the catalytic subunit.
Purpose of the Study:
- To elucidate the distinct functions and activation mechanisms of PI-kinase isoforms.
- To investigate the in vivo phosphorylation patterns of PI-kinase.
- To understand the signaling pathways mediated by PI-kinase.
Main Methods:
- Characterization of PI-kinase subunit interactions.
- Analysis of isoform-specific activation stimuli.
- In vitro and in vivo phosphoinositide phosphorylation assays.
Main Results:
- p110alpha and p110beta, despite binding similarly to p85alpha, possess separate cellular functions and activation triggers.
- In vivo, PI-kinase phosphorylates both D-3 and D-4 positions of phosphoinositides, unlike in vitro findings.
- D-4 phosphorylation occurs with similar or higher efficiency in vivo compared to D-3.
Conclusions:
- PI-kinase isoforms exhibit functional specialization.
- Cellular context dictates PI-kinase phosphorylation site preference.
- PI-kinase signaling involves both D-3 and D-4 phosphoinositide products, expanding known signaling mechanisms.
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