title: Pharmacological profile of phosphatidylinositol 3-kinases and related phosphatidylinositols mediating endothelin(A)  receptor-operated native TRPC channels in rabbit coronary artery myocytes.
abstract: OBJECTIVE
  Endothelin(A) (ET(A) ) receptor-operated canonical transient receptor potential (TRPC) channels mediate Ca²⁺ influx pathways, which are important in coronary artery function. Biochemical pathways linking ET(A) receptor stimulation to TRPC channel opening are unknown. We investigated the involvement of phosphatidylinositol 3-kinases (PI3K) in ET(A) receptor activation of native heteromeric TRPC1/C5/C6 and TRPC3/C7 channels in rabbit coronary artery vascular smooth muscle cells (VSMCs).
  
  
  METHODS
  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 ET(A) 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.
  
  
  RESULTS
  ET(A) receptor-operated TRPC1/C5/C6 and TRPC3/C7 channel activities were inhibited by wortmannin. However, ZSTK474 and AS252424 reduced ET(A) 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
  ET(A) 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. ET(A) 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.
authors.affiliation: Pharmacology & Cell Physiology, Division of Biomedical Sciences, St. George's, University of London, London, UK.
authors.forename: J
authors.initials: J
authors.lastname: Shi
authors.forename: M
authors.initials: M
authors.lastname: Ju
authors.forename: W A
authors.initials: WA
authors.lastname: Large
authors.forename: A P
authors.initials: AP
authors.lastname: Albert
mesh_terms: D000818:Animals; D003331:Coronary Vessels / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D032383:Myocytes, Cardiac / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010716:Phosphatidylinositols / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011817:Rabbits; D044022:Receptor, Endothelin A / Q000502:physiology*; D045162:Thiazolidinediones / Q000494:pharmacology; D050051:Transient Receptor Potential Channels / Q000502:physiology*; D014227:Triazines / Q000494:pharmacology; D014966:Xanthenes / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D019869:Phosphatidylinositol 3-Kinases; D010716:Phosphatidylinositols; D000081082:Phosphoinositide-3 Kinase Inhibitors; D044022:Receptor, Endothelin A; D045162:Thiazolidinediones; D050051:Transient Receptor Potential Channels; D014227:Triazines; D014966:Xanthenes; C512438:5-(5-(4-fluoro-2-hydroxyphenyl)furan-2-ylmethylene)thiazolidine-2,4-dione; C510150:ZSTK474; C007820:gallein