Regulation of class IA PI3Ks: is there a role for monomeric PI3K subunits?
B Geering1, P R Cutillas, B Vanhaesebroeck
1Ludwig Institute for Cancer Research, London, UK.
Biochemical Society Transactions
|March 21, 2007
Summary
Phosphoinositide 3-kinases (PI3K) activity increases in p85 knockout mice. This study challenges the monomeric p85 model, suggesting alternative mechanisms for PI3K signaling regulation.
Area of Science:
- Molecular Biology
- Cell Signaling
- Biochemistry
Background:
- Class IA PI3Ks comprise p110 catalytic and p85 regulatory subunits.
- p85 stabilizes and inhibits p110 activity under basal conditions.
- Receptor recruitment via p85 SH2 domains activates PI3K and produces PIP(3).
Purpose of the Study:
- To investigate the mechanism behind increased PI3K signaling in p85 knockout (KO) mice.
- To evaluate the role of monomeric p85 in PI3K regulation.
- To explore alternative models for PI3K signaling modulation.
Main Methods:
- Generation and analysis of four independent p85 KO mouse lines.
- Biochemical assays to determine subunit ratios in murine cell lines and tissues.
- Investigation of protein stability and receptor binding interactions.
Main Results:
- PI3K signaling is significantly increased in insulin-sensitive tissues of p85 KO mice.
- Evidence suggests monomeric p85 is unstable and does not necessarily compete with heterodimers.
- A 1:1 ratio of p85 and p110 subunits was observed in various murine samples.
Conclusions:
- The proposed model of monomeric p85 inhibiting PI3K activity in p85 KO mice is unlikely.
- Alternative explanations involving phosphatases acting on PIP(3) may account for the observed PI3K hyperactivation.
- Further research is needed to elucidate the precise regulatory mechanisms of PI3K signaling.
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