PHI-1 interacts with the catalytic subunit of myosin light chain phosphatase to produce a Ca(2+) independent increase in MLC(20) phosphorylation and force in avian smooth muscle |
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Authors: | El-Toukhy Amr Given Allison M Ogut Ozgur Brozovich Frank V |
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Institution: | Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN 55905, USA. |
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Abstract: | In avian smooth muscles, GTPgammaS produces a Rho kinase mediated increase in PHI-1 phosphorylation and force, but whether this correlation is causal is unknown. We examined the effect of phosphorylated PHI-1 (P-PHI-1) on force and myosin light chain (MLC(20)) phosphorylation at a constant Ca(2+)]. P-PHI-1, but not PHI-1, increased MLC(20) phosphorylation and force, and phosphorylation of PHI-1 increased the interaction of PHI-1 with PP1c. Microcystin induced a dose-dependent reduction in the binding of PHI-1 to PP1c. These results suggest PHI-1 inhibits myosin light chain phosphatase by interacting with the active site of PP1c to produce a Ca(2+) independent increase in MLC(20) phosphorylation and force. |
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Keywords: | Ca2+ sensitization Myosin light chain phosphatase PP1c PHI-1 MYPT1 Chicken gizzard |
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