title: PSTPIP is a substrate of PTP-PEST and serves as a scaffold guiding PTP-PEST toward a specific dephosphorylation of WASP.
abstract: PSTPIP is a tyrosine-phosphorylated protein involved in the organization of the cytoskeleton. Its ectopic expression induces filipodial-like membrane extensions in NIH 3T3 cells. We previously observed a defect in cytokinesis and an increase in the tyrosine phosphorylation of PSTPIP in PTP-PEST-deficient fibroblasts. In this article, we demonstrate that PTP-PEST and PSTPIP are found in the same complexes in vivo and that they interact directly through the CTH domain of PTP-PEST and the coiled-coil domain of PSTPIP. We tested pathways that could regulate the tyrosine phosphorylation of PSTPIP. We found that the activation of the epidermal growth factor and platelet-derived growth factor receptors can induce PSTPIP phosphorylation. With the use of the PP2 inhibitor, we demonstrate that Src kinases are not involved in the epidermal growth factor-mediated phosphorylation of PSTPIP. Together with previous results, this suggests that c-Abl is the critical tyrosine kinase downstream of growth factor receptors responsible for PSTPIP phosphorylation. We also demonstrate that PTP-PEST dephosphorylates PSTPIP at tyrosine 344. Importantly, we identified tyrosine 344 as the main phosphorylation site of PSTPIP by performing tryptic phosphopeptide maps. This is an important finding since tyrosine 367 of PSTPIP was also proposed as a candidate phosphorylation site involved in the negative regulation of the association between PSTPIP and WASP. In this respect, we observed that the PSTPIP.WASP complex is stable in vivo and is not affected by the phosphorylation of PSTPIP. Furthermore, we demonstrate that PSTPIP serves as a scaffold protein between PTP-PEST and WASP and allows PTP-PEST to dephosphorylate WASP. This finding suggests a possible mechanism for PTP-PEST to directly modulate actin remodeling through the PSTPIP-WASP interaction.
authors.affiliation: Department of Biochemistry, McGill University, Montréal, Québec H3G 1Y6, Canada. jfcote@burnham.org
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Côté
authors.forename: Ping Lin
authors.initials: PL
authors.lastname: Chung
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Théberge
authors.forename: Maxime
authors.initials: M
authors.lastname: Hallé
authors.forename: Susan
authors.initials: S
authors.lastname: Spencer
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Lasky
authors.forename: Michel L
authors.initials: ML
authors.lastname: Tremblay
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002855:Chromatography, Thin Layer; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D054594:Protein Tyrosine Phosphatase, Non-Receptor Type 12; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism; D051316:Wiskott-Aldrich Syndrome Protein; D018909:src Homology Domains
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D011506:Proteins; C110097:Pstpip1 protein, mouse; C495768:Was protein, mouse; D051316:Wiskott-Aldrich Syndrome Protein; D014443:Tyrosine; D005982:Glutathione Transferase; D015688:Oncogene Protein pp60(v-src); D054594:Protein Tyrosine Phosphatase, Non-Receptor Type 12; D017027:Protein Tyrosine Phosphatases; C516739:Ptpn12 protein, mouse