title: Vasodilator-stimulated phosphoprotein (VASP) regulates actin polymerization and contraction in airway smooth muscle by a vinculin-dependent mechanism.
abstract: Vasodilator-stimulated phosphoprotein (VASP) can catalyze actin polymerization by elongating actin filaments. The elongation mechanism involves VASP oligomerization and its binding to profilin, a G-actin chaperone. Actin polymerization is required for tension generation during the contraction of airway smooth muscle (ASM); however, the role of VASP in regulating actin dynamics in ASM is not known. We stimulated ASM cells and tissues with the contractile agonist acetylcholine (ACh) or the adenylyl cyclase activator, forskolin (FSK), a dilatory agent. ACh and FSK stimulated VASP Ser(157) phosphorylation by different kinases. Inhibition of VASP Ser(157) phosphorylation by expression of the mutant VASP S157A in ASM tissues suppressed VASP phosphorylation and membrane localization in response to ACh, and also inhibited contraction and actin polymerization. ACh but not FSK triggered the formation of VASP-VASP complexes as well as VASP-vinculin and VASP-profilin complexes at membrane sites. VASP-VASP complex formation and the interaction of VASP with vinculin and profilin were inhibited by expression of the inactive vinculin mutant, vinculin Y1065F, but VASP phosphorylation and membrane localization were unaffected. We conclude that VASP phosphorylation at Ser(157) mediates its localization at the membrane, but that VASP Ser(157) phosphorylation and membrane localization are not sufficient to activate its actin catalytic activity. The interaction of VASP with activated vinculin at membrane adhesion sites is a necessary prerequisite for VASP-mediated molecular processes necessary for actin polymerization. Our results show that VASP is a critical regulator of actin dynamics and tension generation during the contractile activation of ASM.
authors.affiliation: From the Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120.
authors.forename: Yidi
authors.initials: Y
authors.lastname: Wu
authors.affiliation: From the Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120 sgunst@iupui.edu.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Gunst
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000199:Actins / Q000737:chemistry*; D000818:Animals; D055162:Biocatalysis; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002645:Chickens; D005576:Colforsin / Q000494:pharmacology; D004285:Dogs; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D051304:Profilins / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D021381:Protein Transport / Q000187:drug effects; D014132:Trachea / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism; D016596:Vinculin / Q000737:chemistry / Q000378:metabolism*; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D000199:Actins; D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D010750:Phosphoproteins; D051304:Profilins; D000098662:Vasodilator-Stimulated Phosphoprotein; D016596:Vinculin; D005576:Colforsin; D014443:Tyrosine; D000109:Acetylcholine; D004837:Epinephrine
keywords: Actin; Adhesion; Cytoskeleton; Excitation-contraction Coupling (E-C Coupling); Smooth Muscle