Investigating the Role of G Protein βγ in Kv7-Dependent Relaxations of the Rat Vasculature

Abstract

Objective— In renal arteries, inhibitors of G protein βγ subunits (Gβγ) reduce Kv7 activity and inhibit Kv7-dependent receptor-mediated vasorelaxations. However, the mechanisms underlying receptor-mediated relaxation are artery specific. Consequently, the aim of this study was to ascertain the role of Gβγ in Kv7-dependent vasorelaxations of the rat vasculature. Approach and Results— Isometric tension recording was performed in isolated rat renal, mesenteric, and cerebral arteries to study isoproterenol and calcitonin gene-related peptide relaxations. Kv7.4 was knocked down via morpholino transfection while inhibition of Gβγ was investigated with gallein and M119K. Proximity ligation assay was performed on isolated myocytes to study the association between Kv7.4 and G protein β subunits or signaling intermediaries. Isoproterenol or calcitonin gene-related peptide–induced relaxations were attenuated by Kv7.4 knockdown in all arteries studied. Inhibition of Gβγ with gallein or M119K had no effect on isoproterenol-mediated relaxations in mesenteric artery but had a marked effect on calcitonin gene-related peptide–induced responses in mesenteric artery and cerebral artery and isoproterenol responses in renal artery. Isoproterenol increased association with Kv7.4 and Rap1a in mesenteric artery which were not sensitive to gallein, whereas in renal artery, isoproterenol increased Kv7.4-AKAP (A-kinase anchoring protein) associations in a gallein-sensitive manner. Conclusions— The Gβγ-Kv7 relationship differs between vessels and is an essential requirement for AKAP, but not Rap–mediated regulation of the channel.