A specific role of phosphatidylinositol 3-kinase gamma. A regulation of autonomic Ca(2)+ oscillations in cardiac cells.
Purinergic stimulation of cardiomyocytes turns on a Src family tyrosine kinase-dependent pathway that stimulates PLCgamma and generates IP(3), a breakdown product of phosphatidylinositol 4,5-bisphosphate (PIP2). This signaling pathway closely regulates cardiac cell autonomic activity (i.e., spontaneous cell Ca(2+) spiking). PIP2 is phosphorylated on 3' by phosphoinositide 3-kinases (PI3Ks) that belong to a broad family of kinase isoforms. The product of PI3K, phosphatidylinositol 3,4,5-trisphosphate, regulates activity of PLCgamma. PI3Ks have emerged as crucial regulators of many cell functions including cell division, cell migration, cell secretion, and, via PLCgamma, Ca(2+) homeostasis. However, although PI3Kalpha and -beta have been shown to mediate specific cell functions in nonhematopoietic cells, such a role has not been found yet for PI3Kgamma. We report that neonatal rat cardiac cells in culture express PI3Kalpha, -beta, and -gamma. The purinergic agonist predominantly activates PI3Kgamma. Both wortmannin and LY294002 prevent tyrosine phosphorylation, and membrane translocation of PLCgamma as well as IP(3) generation in ATP-stimulated cells. Furthermore, an anti-PI3Kgamma, but not an anti-PI3Kbeta, injected in the cells prevents the effect of ATP on cell Ca(2+) spiking. A dominant negative mutant of PI3Kgamma transfected in the cells also exerts the same action. The effect of ATP was observed on spontaneous Ca(2+) spiking of wild-type but not of PI3Kgamma(2/2) embryonic stem cell-derived cardiomyocytes. ATP activates the Btk tyrosine kinase, Tec, and induces its association with PLCgamma. A dominant negative mutant of Tec blocks the purinergic effect on cell Ca(2+) spiking. Tec is translocated to the T-tubes upon ATP stimulation of cardiac cells. Both an anti-PI3Kgamma antibody and a dominant negative mutant of PI3Kgamma injected or transfected into cells prevent the latter event. We conclude that PI3Kgamma activation is a crucial step in the purinergic regulation of cardiac cell spontaneous Ca(2+) spiking. Our data further suggest that Tec works in concert with a Src family kinase and PI3Kgamma to fully activate PLCgamma in ATP-stimulated cardiac cells. This cluster of kinases provides the cardiomyocyte with a tight regulation of IP(3) generation and thus cardiac autonomic activity.
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The French Institute of Health and Medical Research, CNRS UPR1086 Montpellier 34293, France.
Roche
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Shuichi
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Sasaki
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Crackower
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MA
Penninger
J
J
Mano
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H
Pucéat
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport; D020013:Calcium Signaling / Q000502:physiology*; D058544:Class Ib Phosphatidylinositol 3-Kinase; D004789:Enzyme Activation; D006321:Heart / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism*; D008954:Models, Biological; D009206:Myocardium / Q000166:cytology; D010507:Periodicity; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D051966:Phospholipase C gamma; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
D007527:Isoenzymes; D018129:Phosphatidylinositol Phosphates; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; C060974:phosphatidylinositol 3,4,5-triphosphate; D000255:Adenosine Triphosphate; D019869:Phosphatidylinositol 3-Kinases; C089848:Tec protein-tyrosine kinase; D058544:Class Ib Phosphatidylinositol 3-Kinase; C546765:Pik3cg protein, rat; D011505:Protein-Tyrosine Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma