title: JAK2 and SHP2 reciprocally regulate tyrosine phosphorylation and stability of proapoptotic protein ASK1.
abstract: Previously we have shown that tyrosine 718 of ASK1 when phosphorylated is critical for SOCS1 binding and SOCS1-mediated degradation of ASK1. However, the kinase and phosphatase responsible for phosphorylation and dephosphorylation of ASK1 at Tyr-718 are unknown. In this study, we identified JAK2 and SHP2 as a Tyr-718-specific kinase and phosphatase, respectively. Interferon-gamma (IFN-gamma) induced degradation of ASK1 in normal but not in SOCS1-KO endothelial cells (EC). IFN-gamma-induced tyrosine phosphorylation of ASK1 at Tyr-718 was blocked by a JAK2-specific inhibitor. IFN-gamma enhanced the association between JAK2 and ASK1, and the ASK1-JAK2 complex was labile and was stabilized by the proteasomal inhibitor MG132. Furthermore, JAK2, but not JAK1, directly bound to and phosphorylated ASK1 at Tyr-718, leading to an enhanced association of ASK1 with SOCS1 and subsequent ASK1 degradation. Next, we showed that overexpression of the SH2-containing protein-tyrosine phosphatase-2 (SHP2) augmented, whereas a phosphatase-inactive mutant of SHP2 inhibited, TNF-induced ASK1 dephosphorylation. SHP2 associated with ASK1 in response to tumor necrosis factor in EC. An SHP-2 substrate-trapping mutant formed a complex with tyrosine-phosphorylated ASK1, suggesting that ASK1 is a direct SHP2 substrate. Moreover, SHP2 wild type, but not a catalytically inactive mutant, dissociated SOCS1 from ASK1. IFN-gamma-induced ASK1 Tyr(P)-718 was enhanced in mouse EC deficient in SHP2 (SHP2-KO). In contrast, tumor necrosis factor-induced dephosphorylation of ASK1 at Tyr(P)-718 and activation of ASK1-JNK signaling, as well as EC apoptosis, are significantly reduced in SHP2-KO EC. Our data suggest that JAK2-SOCS1 and SHP2 reciprocally regulate ASK1 phosphorylation and stability in response to cytokines.
authors.affiliation: Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Luyang
authors.initials: L
authors.lastname: Yu
authors.affiliation: Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520; Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou 510060, China. Electronic address: wang.min@yale.edu.
authors.forename: Wang
authors.initials: W
authors.lastname: Min
authors.affiliation: Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Yun
authors.initials: Y
authors.lastname: He
authors.affiliation: Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Lingfeng
authors.initials: L
authors.lastname: Qin
authors.affiliation: Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06510.
authors.forename: Anton M
authors.initials: AM
authors.lastname: Bennett
authors.affiliation: Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D042783:Endothelial Cells / Q000201:enzymology*; D004795:Enzyme Stability / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D053614:Janus Kinase 2 / Q000235:genetics / Q000378:metabolism*; D048848:MAP Kinase Kinase Kinase 5 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D009097:Multienzyme Complexes; C108944:SOCS1 protein, human; C491590:Socs1 protein, mouse; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C439524:TNF protein, human; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D048848:MAP Kinase Kinase Kinase 5; C482858:MAP3K5 protein, human; C482859:Map3k5 protein, mouse; C516724:PTPN11 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; C516725:Ptpn11 protein, mouse