Endothelial Caveolae-TRPV4-SK Channel Interactions in Shear Stress-Mediated Coronary Arteriole Dilation

We have previously reported that shear stress-mediated dilation (SSD) of coronary arterioles is caveolae-dependent. We found that both TRPV4 and SK channels are targeted to the low-buoyant density caveolin-rich membrane fraction in freshly isolated bovine coronary endothelial cells (BCEC) and TRPV4 and SK3 channels are co-immunoprecipitated by anti-caveolin-1 antibody. Isoproterenol (1 µM) enhanced the whole-cell K+ currents in BCEC by 5-fold that are inhibited by apamin (200 nM), an SK channel-specific inhibitor, but not by iberiotoxin (100 nM) or Tram34 (200 nM). Exposure of the BCEC to the TRPV4 activator, GSK1016790A (150 nM) resulted in a 3.5-fold activation of SK currents. Acute exposure of BCEC seeded in a capillary tube to 10 dynes/cm2 of shear stress (SS) resulted in a 4-fold increase in TRPV4 currents that are inhibited by HC067047 (200 nM), a TRPV4-specific inhibitor, and a 3.5-fold increase in SK currents that are inhibited by apamin (200 nM). However, after incubation with HC067047, a TRPV4 specific inhibitor, SK currents could no longer be activated by SS, suggesting SK activation by SS was mediated through TRPV4. In addition, pre-incubation of isolated coronary arterioles with apamin (200 nM) resulted in a significant diminution of SSD while pre-incubation with HC067047 (150 nM) results in vasoconstriction by SS. Exposure of BECE to SS (10 dynes/cm2 12 h) enhanced the production of endothelium-derived vasodilators, NO and PGI2, and facilitated the translocation of TRPV4 to the caveolae. Inhibition of TRPV4 abolished the SS-mediated [Ca2+]i increase in BECE. These novel results indicate that there is a dynamic interaction in the vascular endothelium between caveolae, TRPV4 and SK channels in the modulation of SSD.