Specific cleavage of the fibroblast receptor for platelet‐derived growth factor by an endogenous Ca2+‐dependent thiol protease

Abstract

Previous studies have shown that platelet‐derived growth factor (PDGF) stimulates the phosphorylation of two components in membranes prepared from human fibroblasts in the presence of Ca2+. One of these represents the 185‐kDa PDGF receptor, which undergoes autophosphorylation, and the other has an Mr of 130000. We show in this communication that the 130‐kDa component is derived from the 185‐kDa receptor via proteolysis by an endogeneous Ca2+‐dependent protease, which is dependent on a reduced ‐SH group for its activity. The 130‐kDa fragment contains several of the characteristics of the receptor, such as the PDGF‐binding site and the major autophosphorylation sites. Furthermore, the cleaved receptor retains tyrosine kinase activity. Copyright © 1986, Wiley Blackwell. All rights reserved