ENDOCYTOSIS OF GROWTH-FACTOR RECEPTORS

Binding of a growth factor (GF) to its specific receptor on the cell s urface causes the initiation of a signal transduction cascade which ev entually results in mitosis. GF:receptor complexes are removed from th e cell surface via receptor-mediated endocytosis, a process which invo lves clathrin-coated pits. After internalization into the endosomal co mpartment, a significant pool of GFs and GF receptors escape recycling to the cell surface and are sorted to the degradation pathway. The li gand-induced 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 biochem ical, morphological and kinetic studies of the mechanism of GF endocyt osis, and the possible role of this process in mitogenic signaling by growth factor receptors.