THE MEMBRANE DISTAL HALF OF GP130 IS RESPONSIBLE FOR THE FORMATION OF A TERNARY COMPLEX WITH IL-6 AND THE IL-6 RECEPTOR

Gp130 is the signal transducing subunit of the interleukin-6 receptor, Signaling is initiated by the complex formation of gp130 with IL-6 bound to the IL-6 receptor (IL-6R), We have subdivided the extracellular domain of gp130 in two parts and expressed the mutant proteins as soluble IgG fusion proteins in COS-7 cells. By studying the formation of the ternary complex we show that the membrane distal half of gp130 which contains a cytokine receptor domain is responsible for the interaction with the IL-6/IL-6R complex, Interestingly this is the same region which is believed to be involved in specific recognition of the related cytokines LIF, OM, and probably also of CNTF and IL-11.