Tissue blood flow is regulated by vascular smooth muscle (VSM) contraction, which in turn, is regulated by changes in the levels of cytosolic free calcium (Ca) and the sensitivity of contractile proteins to Ca. This project will focus on mechanisms regulating rhoA kinase (ROK)-dependent Ca sensitivity. However, what is most novel about this project is that an emphasis will be to understand the cell signaling systems activated by Ca itself that cause ROK-induced Ca sensitization. Regulation of Ca sensitivity is a basic mechanism controlling vascular tone, and dysregulation of Ca sensitivity plays a role in hypertension and the """"""""failure"""""""" of smooth muscle to contract in vasodilatory shock. The long-term goal of my laboratory is to investigate subcellular mechanisms regulating VSM Ca sensitivity and tonic force maintenance to provide basic knowledge for the development of novel therapeutic agents to treat selectively vascular contractile disorders. My laboratory has determined that Ca sensitivity can be increased in VSM by a Ca-dependent mechanism. This Ca-dependent Ca sensitization appears to involve activation of ROK and an atypical PKC isotype, PKCzeta, and appears to be dependent on iPLA2 and PI3K activation. The immediate goal of this project is to identify, using physiological, biochemical, pharmacological, cell and molecular, and morphometric methodologies, the molecular mechanisms regulating Ca-dependent Ca sensitivity and tonic force maintenance in a well-characterized arterial contractile system, the KCI-stimulated rabbit FA. The overall goal of this project is to understand regulation of arterial smooth muscle contraction in tissues maintained in as near a physiological state as possible. Whereas this approach has limitations, by applying multiple methodologies to assess spatiotemporal activation of specific signaling molecules proposed to participate in Ca-dependent Ca sensitization, mechanistic conclusions can be drawn regarding cause and effect of discrete steps linking stimulus with contraction in the VSM of intact, functional tissues.
The Specific Aim of this study will be to test the hypothesis that ROK and PKCzeta both mediate KCI- induced Ca sensitization of FA, and that iPLA2 and PI3K are required as upstream activators of ROK and PKCzeta.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Vascular Cell and Molecular Biology Study Section (VCMB)
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Gao, Yunling
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Virginia Commonwealth University
Schools of Medicine
United States
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Speich, John E; Southern, Jordan B; Henderson, Sheree et al. (2012) Adjustable passive stiffness in mouse bladder: regulated by Rho kinase and elevated following partial bladder outlet obstruction. Am J Physiol Renal Physiol 302:F967-76
Bednarek, Melissa L; Speich, John E; Miner, Amy S et al. (2011) Active tension adaptation at a shortened arterial muscle length: inhibition by cytochalasin-D. Am J Physiol Heart Circ Physiol 300:H1166-73
Clelland, Lyndsay J; Browne, Brendan M; Alvarez, Silvina M et al. (2011) Rho-kinase inhibition attenuates calcium-induced contraction in ?-escin but not Triton X-100 permeabilized rabbit femoral artery. J Muscle Res Cell Motil 32:77-88
Alvarez, S M; Miner, A S; Browne, B M et al. (2010) Failure of Bay K 8644 to induce RhoA kinase-dependent calcium sensitization in rabbit blood vessels. Br J Pharmacol 160:1326-37
Almasri, Atheer M; Ratz, Paul H; Bhatia, Hersch et al. (2010) Rhythmic contraction generates adjustable passive stiffness in rabbit detrusor. J Appl Physiol 108:544-53
Almasri, Atheer M; Ratz, Paul H; Speich, John E (2010) Length adaptation of the passive-to-active tension ratio in rabbit detrusor. Ann Biomed Eng 38:2594-605
Ratz, Paul H; Miner, Amy S; Barbour, Suzanne E (2009) Calcium-independent phospholipase A2 participates in KCl-induced calcium sensitization of vascular smooth muscle. Cell Calcium 46:65-72
Ratz, Paul H; Miner, Amy S (2009) Role of protein kinase Czeta and calcium entry in KCl-induced vascular smooth muscle calcium sensitization and feedback control of cellular calcium levels. J Pharmacol Exp Ther 328:399-408
Speich, John E; Almasri, Atheer M; Bhatia, Hersch et al. (2009) Adaptation of the length-active tension relationship in rabbit detrusor. Am J Physiol Renal Physiol 297:F1119-28
Eddinger, Thomas J; Meer, Daniel P; Miner, Amy S et al. (2007) Potent inhibition of arterial smooth muscle tonic contractions by the selective myosin II inhibitor, blebbistatin. J Pharmacol Exp Ther 320:865-70

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