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Circulation
Year: 2009  |  Volume: 120  |  Issue: 4  |  Page No.: 318 - 325

Loss of Cardiac Phosphoinositide 3-Kinase p110{alpha} Results in Contractile Dysfunction

Z Lu, Y. P Jiang, W Wang, X. H Xu, R. T Mathias, E Entcheva, L. M Ballou, I. S Cohen and R. Z. Lin    

Abstract:

Background— Phosphoinositide 3-kinase (PI3K) p110 plays a key role in insulin action and tumorigenesis. Myocyte contraction is initiated by an inward Ca2+ current (ICa,L) through the voltage-dependent L-type Ca2+ channel (LTCC). The aim of this study was to evaluate whether p110 also controls cardiac contractility by regulating the LTCC.

Methods and Results— Genetic ablation of p110 (also known as Pik3ca), but not p110β (also known as Pik3cb), in cardiac myocytes of adult mice reduced ICa,L and blocked insulin signaling in the heart. p110-null myocytes had a reduced number of LTCCs on the cell surface and a contractile defect that decreased cardiac function in vivo. Similarly, pharmacological inhibition of p110 decreased ICa,L and contractility in canine myocytes. Inhibition of p110β did not reduce ICa,L.

Conclusions— PI3K p110 but not p110β regulates the LTCC in cardiac myocytes. Decreased signaling to p110 reduces the number of LTCCs on the cell surface and thus attenuates ICa,L and contractility.

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