DIFFERENTIAL SHEDDING OF THE 2 SUBUNITS OF THE INTERLEUKIN-6 RECEPTOR

cDNAs coding for the two receptor subunits of the interleukin-6 recept or have been stably expressed in Madine Darby canine kidney (MDCK) cel ls. The fate of the IL-6 binding protein (IL-6R) and of the signal tra nsducing protein gp130 was studied independently. Both proteins were p roteolytically cleaved from cells metabolically labeled with [S-35]met hionine/cysteine leading to the release of soluble receptor proteins o f 55 kDa and 100 kDa, respectively. In contrast to the shedding of the IL-6R gp130 was inefficiently released from the cells and the process was not significantly stimulated by the phorbolester PMA. In addition we show that the soluble forms of the IL-6R and gp130 released by tra nsfected cells can form a ternary complexe with interleukin-6 indicati ng that such complexes also may occur in vivo.