Inhibitory roles for SHP-1 and SOCS-3 following pituitary proopiomelanocortin induction by leukemia inhibitory factor

• Published in: The Journal of clinical investigation Vol. 104; no. 9; pp. 1277 - 1285
• Main Authors: Bousquet, Corinne, Susini, Christiane, Melmed, Shlomo
• Format: Journal Article
• Language: English
• Published: United States American Society for Clinical Investigation 01.11.1999
• Subjects: Animals; Catalysis; Cell Line; DNA-Binding Proteins - metabolism; Down-Regulation; Growth Inhibitors - pharmacology; Interleukin-6; Intracellular Signaling Peptides and Proteins; Janus Kinase 2; Leukemia Inhibitory Factor; Lymphokines - pharmacology; Mice; Models, Biological; Phosphorylation; Pituitary Gland - metabolism; Pro-Opiomelanocortin - metabolism; Protein Tyrosine Phosphatase, Non-Receptor Type 11; Protein Tyrosine Phosphatase, Non-Receptor Type 6; Protein Tyrosine Phosphatases - metabolism; Protein Tyrosine Phosphatases - physiology; Protein-Tyrosine Kinases - metabolism; Proteins - physiology; Proto-Oncogene Proteins; Repressor Proteins; SH2 Domain-Containing Protein Tyrosine Phosphatases; Signal Transduction; STAT3 Transcription Factor; Suppressor of Cytokine Signaling 3 Protein; Suppressor of Cytokine Signaling Proteins; Time Factors; Trans-Activators - metabolism; Transcription Factors; Transfection
• DOI: 10.1172/JCI7924
• ISSN: 0021-9738

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine that stimulates the hypothalamo-pituitary-adrenal (HPA) axis through JAK-STAT activation. We show here that LIF-induced JAK2 and STAT3 tyrosine phosphorylation is transient, disappearing within 20 and 40 minutes, respectively. LIF activates the SH2 domain-containing tyrosine phosphatase, SHP-1, with maximal stimulation observed at 30 minutes. SHP-1 is constitutively associated with JAK2, and LIF induces recruitment of phosphorylated STAT3 to this complex. Overexpression of wild-type or dominant negative forms of SHP-1 shows decreased or increased LIF-induced proopiomelanocortin (POMC) promoter activity, respectively. LIF-induced JAK2 and STAT3 dephosphorylation is delayed until after 60 minutes in cells that overexpress the mutant SHP-1. In addition, SOCS-3, a negative regulator of LIF signaling, binds to JAK2 after 60 minutes of LIF stimulation, after which the complex is degraded by the proteasome. SOCS-3 overexpression blocks LIF-induced JAK2 tyrosine phosphorylation, confirming a role for SOCS-3 in deactivating JAK2 by direct association. Using SOCS-3 fusion proteins, we also define regions of the SOCS-3 protein that are critical for inhibition of LIF-induced POMC promoter activity. Corticotrophic signaling by LIF is thus subject to 2 forms of negative autoregulation: dephosphorylation of JAK2 and STAT3 by the SHP-1 tyrosine phosphatase, and SOCS-3-dependent inactivation of JAK2.