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SOCS: physiological suppressors of cytokine signaling
1The Walter and Eliza Hall Institute of Medical Research and the Cooperative Research Center for Cellular Growth Factors, Post Office, Royal Melbourne Hospital, Victoria 3050, Australia. krebs@wehi.edu.au
Abstract:
Cytokines regulate cellular behavior by interacting with receptors on the plasma membrane of target cells and activating intracellular signal transduction cascades such as the JAK-STAT pathway. Suppressors of cytokine signaling (SOCS) proteins negatively regulate cytokine signaling. The SOCS family consists of eight proteins: SOCS1-SOCS7 and CIS, each of which contains a central Src-homology 2 (SH2) domain and a C-terminal SOCS box. The expression of CIS, SOCS1, SOCS2 and SOCS3 is induced in response to stimulation by a wide variety of cytokines, and overexpression of these proteins in cell lines results in inhibition of cytokine signaling. Thus, SOCS proteins appear to form part of a classical negative feedback loop. The analysis of mice lacking SOCS1 has revealed that it is critical in the negative regulation of IFN(gamma) signaling and in the differentiation of T cells. Additionally, the analysis of mouse embryos lacking SOCS3 suggests that SOCS3 negatively regulates fetal liver erythropoiesis, probably through its ability to modulate erythropoietin (Epo) signaling. Thus, the use of gene targeting has confirmed that SOCS proteins regulate cytokine signaling in a physiological setting.
Insights
Suppressors of cytokine signaling (SOCS) proteins, like SOCS1 and SOCS3, are crucial negative regulators of cytokine signaling pathways. Gene targeting studies confirm their physiological roles in immune cell differentiation and blood development.
Area of Science:
- Immunology
- Molecular Biology
- Cellular Signaling
Background:
- Cytokines are key regulators of cellular behavior, mediating their effects through cell surface receptors and intracellular pathways like JAK-STAT.
- Suppressors of Cytokine Signaling (SOCS) proteins, including SOCS1-SOCS7 and CIS, act as negative feedback regulators of cytokine signaling.
- SOCS proteins feature a conserved Src-homology 2 (SH2) domain and a SOCS box, and their expression is induced by cytokine stimulation.
Purpose of the Study:
- To investigate the physiological roles of SOCS proteins in regulating cytokine signaling.
- To elucidate the specific functions of SOCS1 and SOCS3 in vivo using gene targeting approaches.
Main Methods:
- Analysis of knockout mice lacking specific SOCS proteins (SOCS1 and SOCS3).
- Assessment of cytokine signaling pathways, including Interferon-gamma (IFN-γ) and Erythropoietin (Epo) signaling.
- Evaluation of cellular processes such as T cell differentiation and erythropoiesis.
Main Results:
- Mice lacking SOCS1 exhibit defects in negative regulation of IFN-γ signaling and T cell differentiation.
- Analysis of SOCS3-deficient embryos indicates a role in negatively regulating fetal liver erythropoiesis via Epo signaling.
- Gene targeting confirmed the essential physiological functions of SOCS proteins in modulating cytokine responses.
Conclusions:
- SOCS proteins are critical negative regulators of cytokine signaling in vivo.
- SOCS1 and SOCS3 play distinct, vital roles in immune and developmental processes, respectively.
- These findings underscore the importance of the SOCS feedback loop in maintaining cellular homeostasis.