title: Coordinated regulation of insulin signaling by the protein tyrosine phosphatases PTP1B and TCPTP.
abstract: The protein tyrosine phosphatase PTP1B is a negative regulator of insulin signaling and a therapeutic target for type 2 diabetes. Our previous studies have shown that the closely related tyrosine phosphatase TCPTP might also contribute to the regulation of insulin receptor (IR) signaling in vivo (S. Galic, M. Klingler-Hoffmann, M. T. Fodero-Tavoletti, M. A. Puryer, T. C. Meng, N. K. Tonks, and T. Tiganis, Mol. Cell. Biol. 23:2096-2108, 2003). Here we show that PTP1B and TCPTP function in a coordinated and temporally distinct manner to achieve an overall regulation of IR phosphorylation and signaling. Whereas insulin-induced phosphatidylinositol 3-kinase/Akt signaling was prolonged in both TCPTP-/- and PTP1B-/- immortalized mouse embryo fibroblasts (MEFs), mitogen-activated protein kinase ERK1/2 signaling was elevated only in PTP1B-null MEFs. By using phosphorylation-specific antibodies, we demonstrate that both IR beta-subunit Y1162/Y1163 and Y972 phosphorylation are elevated in PTP1B-/- MEFs, whereas Y972 phosphorylation was elevated and Y1162/Y1163 phosphorylation was sustained in TCPTP-/- MEFs, indicating that PTP1B and TCPTP differentially contribute to the regulation of IR phosphorylation and signaling. Consistent with this, suppression of TCPTP protein levels by RNA interference in PTP1B-/- MEFs resulted in no change in ERK1/2 signaling but caused prolonged Akt activation and Y1162/Y1163 phosphorylation. These results demonstrate that PTP1B and TCPTP are not redundant in insulin signaling and that they act to control both common as well as distinct insulin signaling pathways in the same cell.
authors.affiliation: Department of Biochemistry and Molecular Biology, P.O. Box 13D, Monash University, Victoria 3800, Australia.
authors.forename: Sandra
authors.initials: S
authors.lastname: Galic
authors.forename: Christine
authors.initials: C
authors.lastname: Hauser
authors.forename: Barbara B
authors.initials: BB
authors.lastname: Kahn
authors.forename: Fawaz G
authors.initials: FG
authors.lastname: Haj
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Neel
authors.forename: Nicholas K
authors.initials: NK
authors.lastname: Tonks
authors.forename: Tony
authors.initials: T
authors.lastname: Tiganis
mesh_terms: D000818:Animals; D045163:Antibodies, Phospho-Specific / Q000378:metabolism; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D045163:Antibodies, Phospho-Specific; D048049:Extracellular Signal-Regulated MAP Kinases; D007328:Insulin; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D011972:Receptor, Insulin; C494918:AKT1 protein, human; C516607:PTPN1 protein, human; C516649:PTPN2 protein, human; C516609:Ptpn1 protein, mouse; C516653:Ptpn2 protein, mouse