Stimulation of I_Ca by basal PKA activity is facilitated by caveolin-3 in cardiac ventricular myocytes

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• 作者：Simon Bryant ; Tomomi E. Kimura ; Cherrie H.T. Kong ; Judy J. Watson ; Anabelle Chase ; M. Saadeh Suleiman ; Andrew F. James ; ^{a.james@bristol.ac.uk" class="auth_mail} ; Clive H. Orchard ; ^{clive.orchard@bristol.ac.uk" class="auth_mail}
• 关键词：t-tubules ; Ca ; Phosphorylation ; 尾2-Adrenoceptors
• 刊名：Journal of Molecular and Cellular Cardiology
• 出版年：March, 2014
• 年：2014
• 卷：68
• 期：Complete
• 页码：47-55
• 全文大小：1061 K

文摘

L-type Ca channels (LTCC), which play a key role in cardiac excitation-contraction coupling, are located predominantly at the transverse (t-) tubules in ventricular myocytes. Caveolae and the protein caveolin-3 (Cav-3) are also present at the t-tubules and have been implicated in localizing a number of signaling molecules, including protein kinase A (PKA) and 尾₂-adrenoceptors. The present study investigated whether disruption of Cav-3 binding to its endogenous binding partners influenced LTCC activity. Ventricular myocytes were isolated from male Wistar rats and LTCC current (I_Ca) recorded using the whole-cell patch-clamp technique. Incubation of myocytes with a membrane-permeable peptide representing the scaffolding domain of Cav-3 (C3SD) reduced basal I_Ca amplitude in intact, but not detubulated, myocytes, and attenuated the stimulatory effects of the 尾₂-adrenergic agonist zinterol on I_Ca. The PKA inhibitor H-89 also reduced basal I_Ca; however, the inhibitory effects of C3SD and H-89 on basal I_Ca amplitude were not summative. Under control conditions, myocytes stained with antibody against phosphorylated LTCC (pLTCC) displayed a striated pattern, presumably reflecting localization at the t-tubules. Both C3SD and H-89 reduced pLTCC staining at the z-lines but did not affect staining of total LTCC or Cav-3. These data are consistent with the idea that the effects of C3SD and H-89 share a common pathway, which involves PKA and is maximally inhibited by H-89, and suggest that Cav-3 plays an important role in mediating stimulation of I_Ca at the t-tubules via PKA-induced phosphorylation under basal conditions, and in response to 尾₂-adrenoceptor stimulation.