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. 2003 Dec;285(6):C1377-85.
doi: 10.1152/ajpcell.00501.2002. Epub 2003 Jul 30.

K+ depolarization induces RhoA kinase translocation to caveolae and Ca2+ sensitization of arterial muscle

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K+ depolarization induces RhoA kinase translocation to caveolae and Ca2+ sensitization of arterial muscle

Nicole H Urban et al. Am J Physiol Cell Physiol. 2003 Dec.
Free article

Abstract

KCl causes smooth muscle contraction by elevating intracellular free Ca2+, whereas receptor stimulation activates an additional mechanism, termed Ca2+ sensitization, that can involve activation of RhoA-associated kinase (ROK) and PKC. However, recent studies support the hypothesis that KCl may also increase Ca2+ sensitivity. Our data showed that the PKC inhibitor GF-109203X did not, whereas the ROK inhibitor Y-27632 did, inhibit KCl-induced tonic (5 min) force and myosin light chain (MLC) phosphorylation in rabbit artery. Y-27632 also inhibited BAY K 8644- and ionomycin-induced MLC phosphorylation and force but did not inhibit KCl-induced Ca2+ entry or peak ( approximately 15 s) force. Moreover, KCl and BAY K 8644 nearly doubled the amount of ROK colocalized to caveolae at 30 s, a time that preceded inhibition of force by Y-27632. Colocalization was not inhibited by Y-27632 but was abolished by nifedipine and the calmodulin blocker trifluoperazine. These data support the hypothesis that KCl caused Ca2+ sensitization via ROK activation. We discuss a novel model for ROK activation involving translocation to caveolae that is dependent on Ca2+ entry and involves Ca2+-calmodulin activation.

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