title: Role of the adapter protein Abi1 in actin-associated signaling and smooth muscle contraction.
abstract: Actin filament polymerization plays a critical role in the regulation of smooth muscle contraction. However, our knowledge regarding modulation of the actin cytoskeleton in smooth muscle just begins to accumulate. In this study, stimulation with acetylcholine (ACh) induced an increase in the association of the adapter protein c-Abl interactor 1 (Abi1) with neuronal Wiskott-Aldrich syndrome protein (N-WASP) (an actin-regulatory protein) in smooth muscle cells/tissues. Furthermore, contractile stimulation activated N-WASP in live smooth muscle cells as evidenced by changes in fluorescence resonance energy transfer efficiency of an N-WASP sensor. Abi1 knockdown by lentivirus-mediated RNAi inhibited N-WASP activation, actin polymerization, and contraction in smooth muscle. However, Abi1 silencing did not affect myosin regulatory light chain phosphorylation at Ser-19 in smooth muscle. In addition, c-Abl tyrosine kinase and Crk-associated substrate (CAS) have been shown to regulate smooth muscle contraction. The interaction of Abi1 with c-Abl and CAS has not been investigated. Here, contractile activation induced formation of a multiprotein complex including c-Abl, CAS, and Abi1. Knockdown of c-Abl and CAS attenuated the activation of Abi1 during contractile activation. More importantly, Abi1 knockdown inhibited c-Abl phosphorylation at Tyr-412 and the interaction of c-Abl with CAS. These results suggest that Abi1 is an important component of the cellular process that regulates N-WASP activation, actin dynamics, and contraction in smooth muscle. Abi1 is activated by the c-Abl-CAS pathway, and Abi1 reciprocally controls the activation of its upstream regulator c-Abl.
authors.affiliation: Center for Cardiovascular Sciences, Albany Medical College, Albany, New York 12208, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Cleary
authors.forename: Ruping
authors.initials: R
authors.lastname: Wang
authors.forename: Dale D
authors.initials: DD
authors.lastname: Tang
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D050719:Crk-Associated Substrate Protein / Q000235:genetics / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D015151:Immunoblotting; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects; D016315:Proto-Oncogene Proteins c-abl / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000235:genetics / Q000378:metabolism
chemical_list: C513733:ABI1 protein, human; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C493841:BCAR1 protein, human; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins; D008164:Luminescent Proteins; D014665:Vasodilator Agents; C495771:WASL protein, human; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D014443:Tyrosine; D016315:Proto-Oncogene Proteins c-abl; D000109:Acetylcholine
keywords: Actin; Actin Cytoskeleton; Adaptor Proteins; Contraction; Excitation-contraction Coupling; Fret; Smooth Muscle