Abstract
Cytokines of the interleukin-6 family utilize the shared cytokine receptor gp130 in the formation of active signalling complexes. Tyrosine-757 (Y757) on this receptor is critical for negative regulation of gp130-mediated signalling. Two signalling regulators, suppressor of cytokine signalling 3 (SOCS3) and Src homology 2 domain-containing tyrosine phosphatase-2 (SHP2), are recruited to Y757 following receptor activation; however, the relative contribution made by each of these in down-regulating gp130 signalling is not known. In the present study, we show the design of a mutant gp130 receptor that can recruit SHP2, but not SOCS3. This receptor maintains the critical Y757 residue, but contains mutations in other surrounding residues which are also important for interactions with the Src homology 2 domains of SOCS3 and SHP2. Cells transfected with a chimaeric receptor containing the SHP2-selective gp130 intracellular domain showed an enhanced response to cytokine stimulation, which was similar to that shown by a chimaeric gp130 receptor mutant carrying a Y757F point mutation that failed to recruit either SOCS3 or SHP2. These results demonstrate that the recruitment of SHP2 alone is not sufficient for Y757-dependent negative regulation of gp130 signalling and that this activity must therefore be dependent on SOCS3.