title: Relationship between paxillin and myosin phosphorylation during muscarinic stimulation of smooth muscle.
abstract: The tyrosine phosphorylation of paxillin increases in association with force development during tracheal smooth muscle contraction, suggesting that paxillin plays a role in the contractile activation of smooth muscle [Z. L. Wang, F. M. Pavalko, and S. J. Gunst. Am. J. Physiol. 271 (Cell Physiol. 40): C1594-C1602, 1996]. We compared the Ca2+ sensitivity of the tyrosine phosphorylation of paxillin and myosin light chain (MLC) phosphorylation in tracheal muscle and evaluated whether MLC phosphorylation is necessary to induce paxillin phosphorylation. Ca(2+)-depleted muscle strips were stimulated with 10(-7)-10(-4) M acetylcholine (ACh) in 0,0.05, 0.1, or 0.5 mM extracellular Ca2+. In the absence of extracellular Ca2+, 10(-4) M ACh induced a maximal increase in paxillin phosphorylation without increasing MLC phosphorylation or force. Increases in extracellular Ca2+ concentration did not further increase paxillin phosphorylation. However, during stimulation with 10(-6) M ACh, paxillin phosphorylation increased with increases in extracellular Ca2+ concentration. We conclude that the tyrosine phosphorylation of paxillin can be stimulated by signaling pathways that do not depend on Ca2+ mobilization and that the activation of contractile proteins is not required to elicit paxillin phosphorylation.
authors.affiliation: Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46202, USA.
authors.forename: D
authors.initials: D
authors.lastname: Mehta
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: M F
authors.initials: MF
authors.lastname: Wu
authors.forename: S J
authors.initials: SJ
authors.lastname: Gunst
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004285:Dogs; D009130:Muscle, Smooth / Q000378:metabolism*; D018994:Myosin Light Chains / Q000378:metabolism*; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D014443:Tyrosine / Q000378:metabolism
chemical_list: D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D018994:Myosin Light Chains; D051419:Paxillin; D010750:Phosphoproteins; D014443:Tyrosine; D000109:Acetylcholine; D002118:Calcium