title: Differential regulation of endoplasmic reticulum stress by protein tyrosine phosphatase 1B and T cell protein tyrosine phosphatase.
abstract: Protein-tyrosine phosphatase 1B (PTP1B) and T cell protein-tyrosine phosphatase (TCPTP) are closely related intracellular phosphatases implicated in the control of glucose homeostasis. PTP1B and TCPTP can function coordinately to regulate protein tyrosine kinase signaling, and PTP1B has been implicated previously in the regulation of endoplasmic reticulum (ER) stress. In this study, we assessed the roles of PTP1B and TCPTP in regulating ER stress in the endocrine pancreas. PTP1B and TCPTP expression was determined in pancreases from chow and high fat fed mice and the impact of PTP1B and TCPTP over- or underexpression on palmitate- or tunicamycin-induced ER stress signaling assessed in MIN6 insulinoma β cells. PTP1B expression was increased, and TCPTP expression decreased in pancreases of mice fed a high fat diet, as well as in MIN6 cells treated with palmitate. PTP1B overexpression or TCPTP knockdown in MIN6 cells mitigated palmitate- or tunicamycin-induced PERK/eIF2α ER stress signaling, whereas PTP1B deficiency enhanced ER stress. Moreover, PTP1B deficiency increased ER stress-induced cell death, whereas TCPTP deficiency protected MIN6 cells from ER stress-induced death. ER stress coincided with the inhibition of Src family kinases (SFKs), which was exacerbated by PTP1B overexpression and largely prevented by TCPTP knockdown. Pharmacological inhibition of SFKs ameliorated the protective effect of TCPTP deficiency on ER stress-induced cell death. These results demonstrate that PTP1B and TCPTP play nonredundant roles in modulating ER stress in pancreatic β cells and suggest that changes in PTP1B and TCPTP expression may serve as an adaptive response for the mitigation of chronic ER stress.
authors.affiliation: Department of Nutrition, University of California, Davis, California 95616, USA.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Bettaieb
authors.forename: Siming
authors.initials: S
authors.lastname: Liu
authors.forename: Yannan
authors.initials: Y
authors.lastname: Xi
authors.forename: Naoto
authors.initials: N
authors.lastname: Nagata
authors.forename: Kosuke
authors.initials: K
authors.lastname: Matsuo
authors.forename: Izumi
authors.initials: I
authors.lastname: Matsuo
authors.forename: Samah
authors.initials: S
authors.lastname: Chahed
authors.forename: Jesse
authors.initials: J
authors.lastname: Bakke
authors.forename: Heike
authors.initials: H
authors.lastname: Keilhack
authors.forename: Tony
authors.initials: T
authors.lastname: Tiganis
authors.forename: Fawaz G
authors.initials: FG
authors.lastname: Haj
mesh_terms: D000818:Animals; D016923:Cell Death; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D050417:Insulin-Secreting Cells / Q000201:enzymology*; D051379:Mice; D019308:Palmitic Acid / Q000494:pharmacology; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000235:genetics / Q000378:metabolism*; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D056811:Unfolded Protein Response / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D019308:Palmitic Acid; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; C516609:Ptpn1 protein, mouse