1. Mutational analyses of the SOCS proteins suggest a dual domain requirement but distinct mechanisms for inhibition of LIF and IL-6 signal transduction.
- Author
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Nicholson SE, Willson TA, Farley A, Starr R, Zhang JG, Baca M, Alexander WS, Metcalf D, Hilton DJ, and Nicola NA
- Subjects
- Animals, Calcium-Calmodulin-Dependent Protein Kinases antagonists & inhibitors, Carrier Proteins chemistry, Cell Differentiation, Cell Line, Cytokines physiology, JNK Mitogen-Activated Protein Kinases, Leukemia Inhibitory Factor, Mice, Phosphorylation, Proteins chemistry, Proteins genetics, Proteins physiology, Signal Transduction, Suppressor of Cytokine Signaling 1 Protein, Suppressor of Cytokine Signaling 3 Protein, Suppressor of Cytokine Signaling Proteins, Transfection, Tyrosine metabolism, src Homology Domains genetics, Carrier Proteins genetics, Carrier Proteins physiology, DNA-Binding Proteins, Growth Inhibitors physiology, Interleukin-6 physiology, Lymphokines physiology, Mitogen-Activated Protein Kinases, Mutation, Repressor Proteins, Trans-Activators, Transcription Factors
- Abstract
SOCS-1 (suppressor of cytokine signaling-1) is a representative of a family of negative regulators of cytokine signaling (SOCS-1 to SOCS-7 and CIS) characterized by a highly conserved C-terminal SOCS box preceded by an SH2 domain. This study comprehensively examined the ability of several SOCS family members to negatively regulate the gp130 signaling pathway. SOCS-1 and SOCS-3 inhibited both interleukin-6 (IL-6)- and leukemia inhibitory factor (LIF)-induced macrophage differentiation of murine monocytic leukemic M1 cells and LIF induction of a Stat3-responsive reporter construct in 293T fibroblasts. Deletion of amino acids 51-78 in the N-terminal region of SOCS-1 prevented inhibition of LIF signaling. The SOCS-1 and SOCS-3 N-terminal regions were functionally interchangeable, but this did not extend to other SOCS family members. Mutation of SH2 domains abrogated the ability of both SOCS-1 and SOCS-3 to inhibit LIF signal transduction. Unlike SOCS-1, SOCS-3 was unable to inhibit JAK kinase activity in vitro, suggesting that SOCS-1 and SOCS-3 act on the JAK-STAT pathway in different ways. Thus, although inhibition of signaling by SOCS-1 and SOCS-3 requires both the SH2 and N-terminal domains, their mechanisms of action appear to be biochemically different.
- Published
- 1999
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