Protein Trafficking In and Out of the Golgi Apparatus

Abstract

The Golgi apparatus is one of the major organelles along the exocytotic or secretory pathway that conveys newly synthesized proteins to the cell surface. Proteins travelling through the Golgi undergo a strictly ordered series of glycosylation modifications by enzymes residing in the Golgi's different subcompartments and are sorted to their final destination when they exit the Golgi. Resident Golgi proteins must therefore be able to maintain their location in the face of heavy, surface-directed traffic. Recently, sequences mediating the retention of proteins in different subcompartments of the Golgi have been revealed and it appears that the mechanism of retention for glycosyltransferases may be different from that of a recycling protein that accumulates in the trans-Golgi network. The former relying on sequences in the transmembrane domain and is enhanced by the adjacent cytoplasmic and lumenal domains, as opposed to the latter which requires a tyrosinecontaining cytoplasmic motif that resembles the signal for basolateral targeting and rapid endocytosis.