title: Protein phosphatase 1 dephosphorylates profilin-1 at Ser-137.
abstract: Profilin-1 (PFN1) plays an important role in the control of actin dynamics, and could represent an important therapeutic target in several diseases. We previously identified PFN1 as a huntingtin aggregation inhibitor, and others have implicated it as a tumor-suppressor. Rho-associated kinase (ROCK) directly phosphorylates PFN1 at Ser-137 to prevent its binding to polyproline sequences. This negatively regulates its anti-aggregation activity. However, the phosphatase that dephosphorylates PFN1 at Ser-137, and thus activates it, is unknown. Using a phospho-specific antibody against Ser-137 of PFN1, we characterized PFN1 dephosphorylation in cultured cells based on immunocytochemistry and a quantitative plate reader-based assay. Both okadaic acid and endothall increased pS137-PFN1 levels at concentrations more consistent with their known IC(50)s for protein phosphatase 1 (PP1) than protein phosphatase 2A (PP2A). Knockdown of the catalytic subunit of PP1 (PP1Cα), but not PP2A (PP2ACα), increased pS137-PFN1 levels. PP1Cα binds PFN1 in cultured cells, and this interaction was increased by a phosphomimetic mutation of PFN1 at Ser-137 (S137D). Together, these data define PP1 as the principal phosphatase for Ser-137 of PFN1, and provide mechanistic insights into PFN1 regulation by phosphorylation.
authors.affiliation: Department of Neurology, School of Medicine, Washington University, St. Louis, Missouri, United States of America. shaoj@neuro.wustl.edu
authors.forename: Jieya
authors.initials: J
authors.lastname: Shao
authors.forename: Marc I
authors.initials: MI
authors.lastname: Diamond
mesh_terms: D000818:Animals; D015153:Blotting, Western; D003998:Dicarboxylic Acids / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D041681:NIH 3T3 Cells; D019319:Okadaic Acid / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D051304:Profilins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012694:Serine / Q000235:genetics / Q000378:metabolism*
chemical_list: D003998:Dicarboxylic Acids; C495738:PFN1 protein, human; D051304:Profilins; C100030:endothall; D019319:Okadaic Acid; D012694:Serine; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2