Human rhinovirus serotype 2 uncoating generates size-selective pores in the endosomal membrane allowing 10-kDa dextran release without gross endosomal damage, unlike adenovirus-induced rupture.
HRV2 uncoating generates size-selective pores in endosomal membranes allowing RNA penetration without gross endosomal damage, unlike adenovirus which causes endosomal rupture.
The effect of virus uncoating on endosome integrity during the early steps in viral infection was investigated. Using fluid-phase uptake of 10- and 70-kDa dextrans labeled with a pH-dependent fluorophore (fluorescein isothiocyanate FITC) and a pH-independent fluorophore (cyanine 5 Cy5), we determined the pHs of labeled compartments in intact HeLa cells by fluorescence-activated cell sorting analysis. Subsequently, the number and pH of fluorescent endosomes in cell homogenates were determined by single-organelle flow analysis. Cointernalization of adenovirus and 70-kDa FITC- and Cy5-labeled dextran (FITC/Cy5-dextran) led to virus-induced endosomal rupture, resulting in the release of the marker from the low-pH environment into the neutral cytosol. Consequently, in the presence of adenovirus, the number of fluorescent endosomes was reduced by 40% compared to that in the control. When human rhinovirus serotype 2 (HRV2) was cointernalized with 10-and 70-kDa FITC/Cy5-dextrans, the 10-kDa dextran was released, whereas the 70-kDa dextran remained within the endosomes, which also maintained their low pH. These data demonstrate that pores are generated in the membrane during HRV2 uncoating and RNA penetration into the cytosol without gross damage of the endosomes; 10-kDa dextran can access the cytosol through these pores. Whereas rhinovirus-mediated pore formation was prevented by the vacuolar ATPase inhibitor bafilomycin A1, adenovirus-mediated endosomal rupture also occurred in the presence of the inhibitor. This finding is in keeping with the low-pH requirement of HRV2 infection; for adenovirus, no pH dependence for endosomal escape was found with this drug.
Brabec et al. (Mon,) conducted a other in Viral infection (Human Rhinovirus Serotype 2 and Adenovirus). Human rhinovirus serotype 2 (HRV2) and Adenovirus vs. Control (no virus) was evaluated on Endosome integrity and number of fluorescent endosomes. Human rhinovirus serotype 2 uncoating generates size-selective pores in the endosomal membrane allowing 10-kDa dextran release without gross endosomal damage, unlike adenovirus-induced rupture.