Inhibition of protein phosphatase 2A activity by PI3K? regulates ß-adrenergic receptor function.

Authors:
Vasudevan NT, Mohan ML, Gupta MK, Hussain AK, Naga Prasad SV.
In:
Source: Mol Cell
Publication Date: (2011)
Issue: 41(6): 636-48
Research Area:
Cardiovascular
Basic Research
Cells used in publication:
Cardiomyocyte (R-CM), rat
Species: rat
Tissue Origin: heart
Culture Media:
Abstract
Phosphoinositide 3-kinase ? (PI3K?) is activated by G protein-coupled receptors (GPCRs). We show here that PI3K? inhibits protein phosphatase 2A (PP2A) at the ß-adrenergic receptor (ßAR, a GPCR) complex altering G protein coupling. PI3K? inhibition results in significant increase of ßAR-associated phosphatase activity leading to receptor dephosphorylation and resensitization preserving cardiac function. Mechanistically, PI3K? inhibits PP2A activity at the ßAR complex by phosphorylating an intracellular inhibitor of PP2A (I2PP2A) on serine residues 9 and 93, resulting in enhanced binding to PP2A. Indeed, enhanced phosphorylation of ß2ARs is observed with a phosphomimetic I2PP2A mutant that was completely reversed with a mutant mimicking dephosphorylated state. siRNA depletion of endogenous I2PP2A augments PP2A activity despite active PI3K resulting in ß2AR dephosphorylation and sustained signaling. Our study provides the underpinnings of a PI3K?-mediated regulation of PP2A activity that has significant consequences on receptor function with broad implications in cellular signaling.