K+ depolarization induces RhoA kinase translocation to caveolae and Ca2+ sensitization of arterial muscle.
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.
Urban
Nicole H
NH
Dept. of Biochemistry and Pediatrics, School of Medicine, Virginia Commonwealth University, 1101 East Marshall St., PO Box 980614, Richmond, VA 23298-0614, USA.
Berg
Krystina M
KM
Ratz
Paul H
PH
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D021941:Caveolae / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal; D009119:Muscle Contraction / Q000187:drug effects / Q000528:radiation effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009924:Organ Culture Techniques; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D011817:Rabbits; D015398:Signal Transduction / Q000502:physiology*; D054460:rho-Associated Kinases
D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D011188:Potassium; D002118:Calcium