Abstract

Binding of a growth factor (GF) to its specific receptor on the cell surface causes the initiation of a signal transduction cascade which eventually results in mitosis. GF:receptor complexes are removed from the cell surface via receptor‐mediated endocytosis, a process which involves clathrin‐coated pits. After internalization into the endosomal compartment, a significant pool of GFs and GF receptors escape recycling to the cell surface and are sorted to the degradation pathway. The ligandinduced internalization and lysosomal degradation of GF receptors result in the dramatic loss of surface receptors, a phenomenon termed receptor down‐regulation. In this review, we discuss relevant biochemical, morphological and kinetic studies of the mechanism of GF endocytosis, and the possible role of this process in mitogenic signaling by growth factor receptors.