Hypoxia inhibits myosin phosphatase in pulmonary arterial smooth muscle cells: role of Rho-kinase.
Rho-kinase was recently found to phosphorylate the myosin-binding subunit (MBS) of myosin phosphatase (MP) and to regulate MP activity. Although myosin light chain (MLC) phosphorylation in pulmonary arterial smooth muscle cells (PASMCs) is thought to be the cellular/molecular basis for hypoxic pulmonary vasoconstriction (HPV), very little is known about the role that Rho-kinase/MP plays in HPV. Rat PASMCs were cultured and made hypoxic (PO2 = 23 +/- 2 mm Hg). Cells exposed to normoxia (PO2 approximately 148 mm Hg) served as controls. PASMCs exposed to hypoxia showed a significant increase in MLC and MBS phosphorylation, and a significant decrease in MP activity. Rho-kinase inhibitors (HA1077 or Y-27632) blocked hypoxia-induced MP inactivation and inhibited the hypoxia-induced MLC phosphorylation. Hypoxia was also found to induce stress fiber formation and actin polymerization in cultured PASMCs. In summary, these data show that MP inhibition in PASMCs is linked to activation of Rho-kinase, and that hypoxia inhibits the MP signaling pathway via Rho-kinase.
Wang
Zhiqian
Z
Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 4620, USA. clanner@iupui.edu
Lanner
M Carita
MC
Jin
Najia
N
Swartz
Darl
D
Li
Liang
L
Rhoades
Rodney A
RA
D000818:Animals; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000860:Hypoxia / Q000201:enzymology* / Q000503:physiopathology; D047908:Intracellular Signaling Peptides and Proteins; D008168:Lung / Q000098:blood supply / Q000503:physiopathology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology*; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011651:Pulmonary Artery / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D054460:rho-Associated Kinases
D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D010749:Phosphoprotein Phosphatases; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins