Platelet-derived Growth Factor (PDGF) Regulates Slingshot Phosphatase Activity via Nox1-dependent Auto-dephosphorylation of Serine 834 in Vascular Smooth Muscle Cells

• Type of Material: Article
• Authors: Mithunan Maheswaranathan, Emory University; Hope K. A. Gole, Emory University; Isabel Fernandez, Emory University; Bernard P Lassegue, Emory University; Kathy Griendling, Emory University; Alejandra San Martin Almeyda, Emory University
• Language: English
• Date: 2011-10-14
• Publisher: American Society for Biochemistry and Molecular Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.
• Final Published Version (URL): http://www.jbc.org/content/286/41/35430
• Title of Journal or Parent Work: Journal of Biological Chemistry
• ISSN: 0021-9258
• Volume: 286
• Issue: 41
• Start Page: 35430
• End Page: 35437
• Grant/Funding Information: This work was supported, in whole or in part, by National Institutes of Health Heart, Lung, and Blood Institute Grants HL93115, HL058863, and HL007745.
• Keywords: Vascular Smooth Muscle Cells; Protein Phosphatase; Nox1; Cytoskeleton; Redox Signaling; NADPH Oxidase
• Research Categories: Chemistry, Biochemistry

Abstract

Migration of vascular smooth muscle cells (VSMCs) contributes to vascular pathology. PDGF induces VSMC migration by a Nox1-based NADPH oxidase mediated mechanism. We have previously shown that PDGF-induced migration in VSMCs requires Slingshot-1L (SSH1L) phosphatase activity. In the present work, the mechanism of SSH1L activation by PDGF is further investigated. We identified a 14-3-3 consensus binding motif encompassing Ser-834 in SSH1L that is constitutively phosphorylated. PDGF induces SSH1L auto-dephosphorylation at Ser-834 in wild type (wt), but not in Nox1−/y cells. A SSH1L-S834A phospho-deficient mutant has significantly lower binding capacity for 14-3-3 when compared with the phospho-mimetic SSH1L-S834D mutant, and acts as a constitutively active phosphatase, lacking of PDGF-mediated regulation. Given that Nox1 produces reactive oxygen species, we evaluated their participation in this SSH1L activation mechanism. We found that H2O2 activates SSH1L and this is accompanied by SSH1L/14-3-3 complex disruption and 14-3-3 oxidation in wt, but not in Nox1−/y cells. Together, these data demonstrate that PDGF activates SSH1L in VSMC by a mechanism that involves Nox1-mediated oxidation of 14-3-3 and Ser-834 SSH1L auto-dephosphorylation.