Pharmacological profile of phosphatidylinositol 3‐kinases and related phosphatidylinositols mediating endothelinA receptor‐operated native TRPC channels in rabbit coronary artery myocytes

• Published in: British journal of pharmacology 2012-08, Vol.166 (7), p.2161-2175
• Main Authors: Shi, J, Ju, M, Large, WA, Albert, AP
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; canonical transient receptor potential; Cardiovascular disease; Coronary vessels; endothelin; Medical sciences; Muscular system; Pharmacology. Drug treatments; phosphatidylinositol; phosphatidylinositol 3‐kinase; Research Papers; vascular smooth muscle
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.2012.01937.x

BACKGROUND AND PURPOSE EndothelinA (ETA) receptor‐operated canonical transient receptor potential (TRPC) channels mediate Ca2+ influx pathways, which are important in coronary artery function. Biochemical pathways linking ETA receptor stimulation to TRPC channel opening are unknown. We investigated the involvement of phosphatidylinositol 3‐kinases (PI3K) in ETA receptor activation of native heteromeric TRPC1/C5/C6 and TRPC3/C7 channels in rabbit coronary artery vascular smooth muscle cells (VSMCs). EXPERIMENTAL APPROACH A pharmacological profile of PI3K was created by studying the effect of pan‐PI3K, pan‐Class I PI3K and Class I PI3K isoform‐selective inhibitors on ETA receptor‐evoked single TRPC1/C5/C6 and TRPC3/C7 channel activities in cell‐attached patches from rabbit freshly isolated coronary artery VSMCs. The action of phosphatidylinositol 3‐phosphate‐ [PI(3)P], 4‐phosphate‐ [PI(4)P] and 5‐phosphate‐ [PI(5)P] containing molecules involved in PI3K‐mediated reactions were studied in inside‐out patches. Expression of PI3K family members in coronary artery tissue lysates were analysed using quantitative PCR. KEY RESULTS ETA receptor‐operated TRPC1/C5/C6 and TRPC3/C7 channel activities were inhibited by wortmannin. However, ZSTK474 and AS252424 reduced ETA receptor‐evoked TRPC1/C5/C6 channel activity but potentiated TRPC3/C7 channel activity. All the PI(3)P‐, PI(4)P‐ and PI(5)P‐containing molecules tested induced TRPC1/C5/C6 channel activation, whereas only PI(3)P stimulated TRPC3/C7 channels. CONCLUSIONS AND IMPLICATIONS ETA receptor‐operated native TRPC1/C5/C6 and TRPC3/C7 channel activities are likely to be mediated by Class I PI3Kγ and Class II/III PI3K isoforms, respectively. ETA receptor‐evoked and constitutively active PI3Kγ‐mediated pathways inhibit TRPC3/C7 channel activation. PI3K‐mediated pathways are novel regulators of native TRPC channels in VSMCs, and these signalling cascades are potential pharmacological targets for coronary artery disease.