title: Prostaglandin E2-Dependent Phosphorylation of RAS Inhibition 1 (RIN1) at Ser 291 and 292 Inhibits Transforming Growth Factor-β-Induced RAS Activation Pathway in Human Synovial Fibroblasts: Role in Cell Migration.
abstract: Prostaglandin E2 (PGE2 )-stimulated G-protein-coupled receptor (GPCR) activation inhibits pro-fibrotic TGFβ-dependent stimulation of human fibroblast to myofibroblast transition (FMT), though the precise molecular mechanisms are not fully understood. In the present study, we describe the PGE2 -dependent suppression and reversal of TGFβ-induced events such as α-sma expression, stress fiber formation, and Ras/Raf/ERK/MAPK pathway-dependent activation of myofibroblast migration. In order to elucidate post-ligand-receptor signaling pathways, we identified a predominant PKA phosphorylation motif profile in human primary fibroblasts after treatment with exogenous PGE2 (EC50 30 nM, Vmax 100 nM), mimicked by the adenyl cyclase activator forskolin (EC50 5 μM, Vmax 10 μM). We used a global phosphoproteomic approach to identify a 2.5-fold difference in PGE2 -induced phosphorylation of proteins containing the PKA motif. Deducing the signaling pathway of our migration data, we identified Ras inhibitor 1 (RIN1) as a substrate, whereby PGE2 induced its phosphorylation at Ser291 and at Ser292 by a 5.4- and 4.8-fold increase, respectively. In a series of transient and stable over expression studies in HEK293T and HeLa cells using wild-type (wt) and mutant RIN1 (Ser291/292Ala) or Ras constructs and siRNA knock-down experiments, we showed that PGE2 -dependent phosphorylation of RIN1 resulted in the abrogation of TGFβ-induced Ras/Raf signaling activation and subsequent downstream blockade of cellular migration, emphasizing the importance of such phosphosites in PGE2 suppression of wound closure. Overexpression experiments in tandem with pull-down assays indicated that specific Ser291/292 phosphorylation of RIN1 favored binding to activated Ras. In principal, understanding PGE2 -GPCR activated signaling pathways mitigating TGFβ-induced fibrosis may lead to more evidence-based treatments against the disease. J. Cell. Physiol. 232: 202-215, 2017. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Renal Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts. cgerarduzzi@bwh.harvard.edu.|Departments of Experimental Medicine, McGill University, Montréal, QC, Canada. cgerarduzzi@bwh.harvard.edu.
authors.forename: Casimiro
authors.initials: C
authors.lastname: Gerarduzzi
authors.affiliation: Departments of Medicine and Experimental Medicine, McGill University, Montréal, QC, Canada.
authors.forename: QingWen
authors.initials: Q
authors.lastname: He
authors.affiliation: Departments of Experimental Medicine, McGill University, Montréal, QC, Canada.
authors.forename: Beibei
authors.initials: B
authors.lastname: Zhai
authors.affiliation: Department of Orthopaedic Surgery, Jewish General Hospital, Montréal, QC, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Antoniou
authors.affiliation: Departments of Medicine and Experimental Medicine, McGill University, Montréal, QC, Canada.
authors.forename: John A
authors.initials: JA
authors.lastname: Di Battista
mesh_terms: D002465:Cell Movement / Q000187:drug effects*; D005576:Colforsin / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C092117:RIN1 protein, human; D016212:Transforming Growth Factor beta; D005576:Colforsin; D018631:ras Proteins; D015232:Dinoprostone