Caveolin-3 is required for regulation of transient outward potassium current by angiotensin II in mouse atrial myocytes

Angiotensin II (AngII) is a key mediator of the renin-angiotensin system and plays an important role in the regulation of cardiac electrophysiology by affecting various cardiac ion currents, including transient outward potassium current, I-to. AngII receptors and molecular components of I-to, Kv(4)(.2) and K(v)4.3 channels, have been linked to caveolae structures. However, their functional interaction and the importance of such proximity within 50- to 100-nm caveolar nanodomains remain unknown. To address this, we studied the mechanisms of I-to regulation by AngII in atrial myocytes of wild-type (WT) and cardiac-specific caveolin-3 (Cav3) conditional knockout (Cav3KO) mice. We showed that in WT atrial myocytes, a short-term (2 h) treatment with AngII (5 mu M) significantly reduced I-to density. This effect was prevented 1) by a 30-min pretreatment with a selective antagonist of AngII receptor 1 (Ang1R) losartan (2 mu M) or 2) by a selective inhibition of protein kinase C (PKC) by BIM1 (10 mu M). The effect of AngII on I-to was completely abolished in Cav3-KO mice, with no change in a baseline I-to current density. In WT atria, Ang1Rs co-localized with Cav3, and the expression of Ang1Rs was significantly decreased in Cav3KO in comparison with WT mice, whereas no change in K(v)4.2 and K(v)4.3 protein expression was observed. Overall, our findings demonstrate that Cav3 is involved in the regulation of Ang1R expression and is required for the modulation of I-to by AngII in mouse atrial myocytes. NEW & NOTEWORTHY Angiotensin II receptor 1 is associated with caveolae and caveolar scaffolding protein caveolin-3 in mouse atrial myocytes that is required for the regulation of I-to by angiotensin II. Downregulation of caveolae/caveolin-3 disrupts this regulation and may be implicated in pathophysiological atrial remodeling.

Automated summary

This study reveals the association of Angiotensin II receptor 1 with caveolae and caveolar scaffolding protein caveolin-3 in mouse atrial myocytes, which is essential for the regulation of I-to by Angiotensin II. Downregulation of caveolae/caveolin-3 disrupts this regulation and may be implicated in pathophysiological atrial remodeling.