BIOSYNTHESIS AND HALF-LIFE OF THE INTERLEUKIN-6 RECEPTOR AND ITS SIGNAL TRANSDUCER GP130

Interleukin-6 (IL-6) exerts its action via a receptor complex composed of a ligand-binding subunit (gp80) and a signal transducer (gp130) wh ich both belong to the hematopoietic receptor superfamily. Very little is known about the biosynthesis and the biological half-lives of prot eins of this superfamily. Therefore, we studied the biosynthesis and m aturation of the interleukin-6 receptor and its signaling subunit gp13 0 by pulse chase experiments in stably transfected Madin-Darby canine kidney cells. We found that both proteins are synthesized as precursor s with apparent molecular masses of 67 kDa and 130 kDa, respectively. These receptor forms are processed within 45-60 min into mature protei ns of 82 kDa and 150 kDa containing complex-type oligosaccharides. The signal transducer gp130 shows a similar maturation in human hepatoma cells HepG2. The IL-6 receptor appears at the cell surface 45 min afte r completion of its synthesis in the endoplasmic reticulum. In both ce ll types studied, gp80 and gp130 are rapidly turned over with half-liv es of 2-3 h. These half-lives were unaffected by the presence of the l igand IL-6.