Identification of critical residues required for suppressor of cytokine signaling-specific regulation of interleukin-4 signaling

• Published in: The Journal of biological chemistry Vol. 275; no. 34; pp. 26500 - 26506
• Main Authors: Haque, S J, Harbor, P C, Williams, B R
• Format: Journal Article
• Language: English
• Published: United States 25-08-2000
• Subjects: Animals; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - physiology; Cells, Cultured; DNA-Binding Proteins; interleukin 4 receptors; Interleukin-4 - physiology; Jak protein; Janus Kinase 1; Mice; Mutagenesis, Site-Directed; Protein-Tyrosine Kinases - metabolism; Proteins - chemistry; Proteins - genetics; Proteins - physiology; Receptors, Interleukin-4 - metabolism; Repressor Proteins; Signal Transduction; SOCS-1 protein; SOCS-3 protein; src Homology Domains; Stat6 protein; STAT6 Transcription Factor; Structure-Activity Relationship; Suppressor of Cytokine Signaling 1 Protein; Suppressor of Cytokine Signaling 3 Protein; Suppressor of Cytokine Signaling Proteins; Trans-Activators - metabolism; Transcription Factors
• ISSN: 0021-9258
• DOI: 10.1074/jbc.275.34.26500

Suppressor of cytokine signaling (SOCS) family proteins were originally identified as cytokine-induced negative regulators of cytokine signaling. We show that SOCS-1 and SOCS-3 inhibit interleukin (IL)-4-dependent signal transducer and activator of transcription 6 (Stat6) activation of and subsequent gene induction. By contrast, SOCS-2 and cytokine-inducible Src homology domain 2 (SH2)-containing protein up-regulate these processes. IL-4 initiates transmembrane signaling through two types of receptor complexes comprising the IL-4Ralpha subunit and the associated Janus kinase 1 (Jak1) as common essential components. We demonstrate that both SOCS-1- and SOCS-3-mediated down-regulation of IL-4 signaling is due to an inhibition of the receptor associated Jak1 activity. The SOCS proteins contain an amino-terminal region of variable length and primary structure, a central SH2 domain, and a carboxyl-terminal conserved motif termed SOCS-box. We show that the SH2 domains of SOCS-2, SOCS-3, and cytokine-inducible SH2-containing protein are functionally redundant in regulating the IL-4-dependent Jak-Stat signaling. The Pre-SH2 domains of SOCS-2 and SOCS-3 confer the specificity of their regulatory function. Importantly, the Pre-SH2 domain of SOCS-3 alone can inhibit IL-4 signaling. The SH2-proximal 25 amino acids of SOCS-3 are sufficient for this inhibition, and the Thr residue at position 24 and the Phe residue at position 25 are individually indispensable for its inhibitory function. Thus, the Thr-Phe motif in the Pre-SH2 domain plays a critical role in SOCS-3-mediated inhibition of the IL-4-dependent Jak-Stat signaling, likely by regulating the mode of SOCS-Jak interaction.