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647941 
Journal Article 
Phosphoinositide 3-kinase gamma mediates angiotensin II-induced stimulation of L-type calcium channels in vascular myocytes 
Quignard, JF; Mironneau, J; Carricaburu, V; Fournier, B; Babich, A; Nurnberg, B; Mironneau, C; Macrez, N 
2001 
Yes 
Journal of Biological Chemistry
ISSN: 0021-9258
EISSN: 1083-351X 
276 
35 
32545-32551 
Previous results have shown that in rat portal vein myocytes the betagamma dimer of the G(13) protein transduces the angiotensin II- induced stimulation of calcium channels and increase in intracellular Ca(2+) concentration through activation of phosphoinositide 3-kinase (PI3K). In the present work we determined which class I PI3K isoforms were involved in this regulation. Western blot analysis indicated that rat portal vein myocytes expressed only PI3Kalpha and PI3Kgamma and no other class I PI3K isoforms. In the intracellular presence of an anti- p110gamma antibody infused by the patch clamp pipette, both angiotensin II- and Gbetagamma-mediated stimulation of Ca(2+) channel current were inhibited, whereas intracellular application of an anti-p110alpha antibody had no effect. The anti-PI3Kgamma antibody also inhibited the angiotensin II- and Gbetagamma-induced production of phosphatidylinositol 3,4,5-trisphosphate. In Indo-1 loaded cells, the angiotensin II-induced increase in [Ca(2+)](i) was inhibited by intracellular application of the anti-PI3Kgamma antibody, whereas the anti-PI3Kalpha antibody had no effect. The specificity of the anti- PI3Kgamma antibody used in functional experiments was ascertained by showing that this antibody did not recognize recombinant PI3Kalpha in Western blot experiments. Moreover, anti-PI3Kgamma antibody inhibited the stimulatory effect of intracellularly infused recombinant PI3Kgamma on Ca(2+) channel current without altering the effect of recombinant PI3Kalpha. Our results show that, although both PI3Kgamma and PI3Kalpha are expressed in vascular myocytes, the angiotensin II-induced stimulation of vascular L-type calcium channel and increase of [Ca(2+)](i) involves only the PI3Kgamma isoform. 
1-Phosphatidylinositol 3-Kinase; isolation & purification; metabolism; Angiotensin II; pharmacology; Animal; Antibodies; Barium; Blotting; Western; Calcium; Calcium Channels; L-Type; drug effects; physiology; Cell Membrane; enzymology; In Vitro; Isoenzymes; Kinetics; Membrane Potentials; Microsomes; Muscle; Smooth; Vascular; cytology; Patch-Clamp Techniques; Phorbol 12; 13-Dibutyrate; Portal Vein; Protein Subunits; Rats; Recombinant Proteins; Support; Non-U.S.Gov't