M. Huber et al., Elevated endosomal pH in HeLa cells overexpressing mutant dynamin can affect infection by pH-sensitive viruses, TRAFFIC, 2(10), 2001, pp. 727-736
Many viruses gain access to the cell via the endosomal route and require lo
w endosomal pH for infectivity. The GTPase dynamin is essential for clathri
n-dependent endocytosis, and in HeLa cells overexpressing the nonfunctional
dynamin(K44A) mutant the formation of clathrin-coated vesicles is halted.
HRV2, a human minor group rhinovirus, is internalized by members of the low
-density lipoprotein receptor family in a clathrin-independent manner. The
low endosomal pH then leads to conversion of the capsid to C-antigen, which
is required for release (uncoating) and transfer of the viral RNA into the
cytosol and de novo synthesis of infectious virus. We here demonstrate tha
t overexpression of dynamin(K44A) reduces this antigenic conversion and res
ults in diminished viral synthesis. In contrast, lysosomal degradation is u
naffected. The kinetics of the formation of C-antigen in vitro and in vivo
suggest that the pH in endosomes is elevated by about 0.4 units upon overex
pression of dynamin(K44A). As a consequence, HRV2 uncoating is diminished e
arly after internalization but attains control levels upon prolonged intern
alization. Thus, overexpression of dynamin(K44A), in addition to traffickin
g defects, results in an elevated endosomal pH and thereby affects virus in
fection and most likely endosomal sorting and processing.