The cell biology of receptor-mediated virus entry

Grove, Joe; Marsh, Mark

Physically larger virus particles, including poxviruses, filoviruses, herpesviruses, and the recently described mimiviruses (La Scola et al., 2003) , cannot be accommodated by small endocytic vesicles and instead induce the formation of larger structures such as phagosomes or macropinosomes. Phagocytosis is receptor driven and involves the actin-dependent formation of vesicles, the membrane of which is closely apposed to the surface of the internalized particle (Mercer et al., 2010b) . and lysosomes (involving decreasing luminal pH, increasing levels of active hydrolytic enzymes, and alteration in lipid composition) correlates with movement of endocytic organelles toward the nucleus by microtubule-mediated retrograde translocation. The need for some viruses to be delivered to more perinuclear environments may be particularly important in some cell targets in vivo where cell organization is more elaborate and key for cell function. Neurons are an extreme example in which viruses may be taken into the cell by endocytosis at a peripheral synapse such as a neuromuscular junction but require transport, in some cases many tens of centimeters to the cell body and nucleus. In such cases, viruses can exploit endosomal transport along axons and use the lower pH of late endosomes (approximately pH 5.0) or exposure to acid hydrolases to delay penetration until endosomal or lysosomal delivery to a perinuclear location (Fig. 3 C ; Lozach et al., 2011a) .