Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 229

Following attachment to one or more receptors, virus particles have to enter the cells. Many animal viruses enter cells by the same pathways by which cells take up macromolecules. The plasma membrane, the limiting membrane of the cell, permits nutrient molecules to enter and waste molecules to leave, thereby ensuring an appropriate internal environment. Water, gases, and small hydrophobic molecules such as ethanol can freely traverse the lipid bilayer, but most metabolites and ions cannot. These essential components enter the cell by multiple transport processes (Fig. 5.10). Obviously, receptors play a role is this process, as they can localize at specific membrane domains prior to or after virus particle attachment and can also mediate signaling that facilitates virus particle up-take by processes normally employed to allow molecules to enter the cell. Disruption of cellular membranes is a necessary step in virus entry and distinguishes enveloped from nonenveloped viruses. For the former, membrane fusion is an integral step of entry, whereas nonenveloped viruses use alternative mechanisms described in later sections. Typically, entry and intracellular transport are tightly linked, though this section will focus on how viruses enter cells.