Abstract
Modulation of voltage-gated L-type Ca2+ channels by phosphoinositide 3-kinase (PI3K) regulates Ca2+ entry and plays a crucial role in vascular excitation-contraction coupling. Angiotensin II (Ang II) activates Ca2+ entry by stimulating L-type Ca2+ channels through Gbeta-sensitive PI3K in portal vein myocytes. Moreover, PI3K and Ca2+ entry activation have been reported to be necessary for receptor tyrosine kinase-coupled and G protein-coupled receptor-induced DNA synthesis in vascular cells. We have previously shown that tyrosine kinase-regulated class Ia and G protein-regulated class Ib PI3Ks are able to modulate vascular L-type Ca2+ channels. PI3Ks display 2 enzymatic activities: a lipid-kinase activity leading to the formation of phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3 or PIP3] and a serine-kinase activity. Here we show that exogenous PIP3 applied into the cell through the patch pipette is able to reproduce the Ca2+ channel-stimulating effect of Ang II and PI3Ks. Moreover, the Ang II-induced PI3K-mediated stimulation of Ca2+ channel and the resulting increase in cytosolic Ca2+ concentration are blocked by the anti-PIP3 antibody. Mutants of PI3K transfected into vascular myocytes also revealed the essential role of the lipid-kinase activity of PI3K in Ang II-induced Ca2+ responses. These results suggest that PIP3 is necessary and sufficient to activate a Ca2+ influx in vascular myocytes stimulated by Ang II.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Androstadienes / pharmacology
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Angiotensin II / pharmacology*
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Animals
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Barium / metabolism
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Calcium / metabolism*
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Calcium Channels, L-Type / drug effects*
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Calcium Channels, L-Type / physiology
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Calmodulin-Binding Proteins / pharmacology
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Cells, Cultured / drug effects
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Cells, Cultured / physiology
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Class Ib Phosphatidylinositol 3-Kinase
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Cytosol / metabolism
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Dihydropyridines / pharmacology
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Enzyme Inhibitors / pharmacology
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Ion Channel Gating / drug effects
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Ion Transport / drug effects
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Isoenzymes / antagonists & inhibitors
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Isoenzymes / genetics
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Isoenzymes / physiology*
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Lipid Metabolism
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Membrane Potentials / drug effects
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Muscle, Smooth, Vascular / cytology*
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Myocytes, Smooth Muscle / drug effects*
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Myocytes, Smooth Muscle / physiology
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Nerve Tissue Proteins / pharmacology
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Neurogranin
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Patch-Clamp Techniques
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Phosphatidylinositol 3-Kinases / genetics
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Phosphatidylinositol 3-Kinases / physiology*
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Phosphatidylinositol Phosphates / antagonists & inhibitors
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Phosphatidylinositol Phosphates / pharmacology*
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Phosphatidylinositol Phosphates / physiology
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Phosphoinositide-3 Kinase Inhibitors
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Phosphorylation / drug effects
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Portal Vein
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Protein Processing, Post-Translational / drug effects
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Rats
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Rats, Wistar
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Recombinant Fusion Proteins / physiology
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Substrate Specificity
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Transfection
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Wortmannin
Substances
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Androstadienes
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Calcium Channels, L-Type
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Calmodulin-Binding Proteins
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Dihydropyridines
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Enzyme Inhibitors
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Isoenzymes
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Nerve Tissue Proteins
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Nrgn protein, rat
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Phosphatidylinositol Phosphates
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Phosphoinositide-3 Kinase Inhibitors
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Recombinant Fusion Proteins
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phosphatidylinositol 3,4,5-triphosphate
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Angiotensin II
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Neurogranin
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Barium
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Class Ib Phosphatidylinositol 3-Kinase
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Pik3cg protein, rat
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oxodipine
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Calcium
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Wortmannin