title: Coupling of c-Src to large conductance voltage- and Ca2+-activated K+ channels as a new mechanism of agonist-induced vasoconstriction.
abstract: The voltage-dependent and Ca(2+)-activated K(+) channel (MaxiK, BK) and the cellular proto-oncogene pp60(c-Src) (c-Src) are abundant proteins in vascular smooth muscle. The role of MaxiK channels as a vasorelaxing force is well established, but their role in vasoconstriction is unclear. Because Src participates in regulating vasoconstriction, we investigated whether c-Src inhibits MaxiK as a mechanism for agonist-induced vasoconstriction. Functional experiments in human and rat show that inhibitors of Src (Lavendustin A, PP2) but not inactive compounds (Lavendustin B, PP3) induce a pronounced relaxation of coronary or aortic smooth muscle precontracted with 5-hydroxytriptamine, phenylephrine, or Angiotensin II. Iberiotoxin, a MaxiK blocker, antagonizes the relaxation induced by Lavendustin A or PP2, indicating that c-Src inhibits the Iberiotoxin-sensitive component, likely MaxiK channels. In agreement, coronary muscle MaxiK currents were enhanced by Lavendustin A. To investigate the molecular mechanism of c-Src action on MaxiK channels, we transiently expressed its alpha subunit, hSlo, with or without c-Src in HEK293T cells. The voltage sensitivity of hSlo was right-shifted by approximately 16 mV. hSlo inhibition by c-Src is due to channel direct phosphorylation because: (i) excised patches exposed to protein tyrosine phosphatase (CD45) resulted in a partial reversal of the inhibitory effect by approximately 10 mV, and (ii) immunoprecipitated hSlo channels were recognized by an anti-phosphotyrosine Ab. Furthermore, coexpression of hSlo and c-Src demonstrate a striking colocalization in HEK293T cells. We propose that MaxiK channels via direct c-Src-dependent phosphorylation play a significant role supporting vasoconstriction after activation of G protein-coupled receptors by vasoactive substances and neurotransmitters.
authors.affiliation: Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095-1778, USA.
authors.forename: Abderrahmane
authors.initials: A
authors.lastname: Alioua
authors.forename: Aman
authors.initials: A
authors.lastname: Mahajan
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Nishimaru
authors.forename: Masoud M
authors.initials: MM
authors.lastname: Zarei
authors.forename: Enrico
authors.initials: E
authors.lastname: Stefani
authors.forename: Ligia
authors.initials: L
authors.lastname: Toro
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D001158:Arteries; D002118:Calcium; D002461:Cell Line, Transformed; D003331:Coronary Vessels; D006801:Humans; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D010636:Phenols / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010766:Phosphorylation; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D000090063:Proto-Oncogene Mas; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D012459:Salicylates / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology; D014661:Vasoconstriction / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000378:metabolism*; D062368:meta-Aminobenzoates
chemical_list: C412373:AG 1879; C494841:KCNMA1 protein, human; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; C000715470:MAS1 protein, human; D010636:Phenols; D024681:Potassium Channels, Calcium-Activated; D000090063:Proto-Oncogene Mas; D011743:Pyrimidines; D012459:Salicylates; D014662:Vasoconstrictor Agents; D062368:meta-Aminobenzoates; D000804:Angiotensin II; C092428:lavendustin B; D010656:Phenylephrine; D012701:Serotonin; C062898:lavendustin A; D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D017493:Leukocyte Common Antigens; D002118:Calcium