The role of virion membrane protein endocytosis in the herpesvirus life cycle

Endocytosis of cellular surface membrane proteins is a well-characterized, common occurrence. Internalization of cell surface receptors, often with bo und ligands, aid in global events, such as cellular metabolism, as well as in specific, directed functions, such as the induction of signal transducti on cascades or immune function. Some, but not all, herpesvirus membrane pro teins are internalized from the plasma membrane by a process similar to rec eptor-mediated endocytosis. No known functions, however, have been ascribed to endocytosis of these proteins. In this review, we consider the function of herpesvirus membrane protein endocytosis. We compare and contrast the e ndocytosis and intracellular trafficking of two pseudorabies virus membrane proteins, the type I glycoprotein, gE, and the type II, tail-anchored memb rane protein, Us9, and discuss the possible function of their internalizati on during the virus life cycle. (C) 2000 Elsevier Science B.V. All rights r eserved.