RECEPTOR SIGNALING AND THE REGULATION OF ENDOCYTIC MEMBRANE-TRANSPORT

Vesicle-mediated membrane traffic has long been considered to be a con stitutive process that is not burdened by layers of regulation. This c ontrasts with transmembrane signalling systems at the plasma membrane which relay information (i.e. extracellular stimuli) from the cell sur face to the cytoplasm via a myriad of different protein-protein intera ctions and second messenger cascades. An accumulation of recent eviden ce, however, now suggests that signal-transduction pathways also play a critical role in the regulation of protein and membrane trafficking, In particular, the analysis of the signalling pathways initiated by r eceptor tyrosine kinases at the plasma membrane has yielded new insigh ts into the molecular mechanisms of endocytosis. In addition, recent e vidence has suggested potential new roles for two previously character ized vesicle coat proteins in a membrane traffic route that is regulat ed via cell surface receptor signalling.