Cytoplasmic coat proteins involved in endosome function

AbstractEndosomes are intermediates for a complex series of sorting and transport events that occur during receptor-mediated endocytosis. These involve the recognition of targeting determinants on the cytoplasmic domains of many membrane proteins as well as the formation of specific transport vesicles. Accordingly, endosome function is likely to be governed by the regulated assembly of cytoplasmic coat complexes. We have found that, in vitro, endosomes recruit a characteristic set of cytoplasmic proteins in a GTPγS-stimulated and brefeldin A-sensitive fashion. Among these are members of the COP-1 and ARF families of coat proteins. In addition, endosomes were also found to assemble distinct, clathrin-like coats. Since micro-injection of antibodies to β-COP inhibits the entry of enveloped viruses via the endocytic pathway, it is apparent that the recruitment of COP-I or COP-I-related proteins plays an important role in the function of endosomes in intact cells