title: β-Arrestin regulation of myosin light chain phosphorylation promotes AT1aR-mediated cell contraction and migration.
abstract: Over the last decade, it has been established that G-protein-coupled receptors (GPCRs) signal not only through canonical G-protein-mediated mechanisms, but also through the ubiquitous cellular scaffolds β-arrestin-1 and β-arrestin-2. Previous studies have implicated β-arrestins as regulators of actin reorganization in response to GPCR stimulation while also being required for membrane protrusion events that accompany cellular motility. One of the most critical events in the active movement of cells is the cyclic phosphorylation and activation of myosin light chain (MLC), which is required for cellular contraction and movement. We have identified the myosin light chain phosphatase Targeting Subunit (MYPT-1) as a binding partner of the β-arrestins and found that β-arrestins play a role in regulating the turnover of phosphorylated myosin light chain. In response to stimulation of the angiotensin Type 1a Receptor (AT1aR), MLC phosphorylation is induced quickly and potently. We have found that β-arrestin-2 facilitates dephosphorylation of MLC, while, in a reciprocal fashion, β-arrestin 1 limits dephosphorylation of MLC. Intriguingly, loss of either β-arrestin-1 or 2 blocks phospho-MLC turnover and causes a decrease in the contraction of cells as monitored by atomic force microscopy (AFM). Furthermore, by employing the β-arrestin biased ligand [Sar(1),Ile(4),Ile(8)]-Ang, we demonstrate that AT1aR-mediated cellular motility involves a β-arrestin dependent component. This suggests that the reciprocal regulation of MLC phosphorylation status by β-arrestins-1 and 2 causes turnover in the phosphorylation status of MLC that is required for cell contractility and subsequent chemotaxic motility.
authors.affiliation: Département de Pharmacologie, Faculté de Médecine et des Sciences de la Santé de l'Université de Sherbrooke, Sherbrooke, Québec, Canada.
authors.forename: Elie
authors.initials: E
authors.lastname: Simard
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Kovacs
authors.forename: William E
authors.initials: WE
authors.lastname: Miller
authors.forename: Jihee
authors.initials: J
authors.lastname: Kim
authors.forename: Michel
authors.initials: M
authors.lastname: Grandbois
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lefkowitz
mesh_terms: D000595:Amino Acid Sequence; D000804:Angiotensin II / Q000494:pharmacology; D019390:Arrestins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism*; D043263:Myosin-Light-Chain Phosphatase / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D025941:Protein Interaction Mapping; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C000605253:ARRB1 protein, human; C000605254:ARRB2 protein, human; D019390:Arrestins; D018994:Myosin Light Chains; D044140:Receptor, Angiotensin, Type 1; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D000804:Angiotensin II; D043263:Myosin-Light-Chain Phosphatase; C490372:PPP1R12A protein, human