On the Role of Endocytosis in the Entry of Animal Viruses
In the last ten years an understanding of the molecular mechanisms involved in the entry of animal viruses has begun to emerge. It is now clear that many enveloped (viruses containing a lipid/protein membrane) and non-enveloped (viruses containing a protein shell) viruses need to be exposed to acidic pH for effective entry into a cell (Table 1). These so-called pH-dependent viruses rely on endocytosis for their delivery to acidic endocytic organelles and their penetration can be blocked by reagents, such as weak bases and carboxylic ionophores, that neutralise the pH in cytoplasmic organelles (see Marsh and Helenius 1989). However, a number of other viruses, both enveloped and non-enveloped, are not affected by weak bases or ionophores and it appears that pH is not an important factor in their entry (Choppin and Scheid 1980; McClure et al. 1988; 1990). Consequently these ‘pH-independent’ viruses can potentially penetrate the host cell at the plasma membrane and/or from acidic endocytic organelles.
KeywordsHepatitis Influenza Dine Stomatitis Monensin
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