Japanese encephalitis virus (JEV), one of encephalitic flaviviruses, is naturally transmitted by mosquitoes. During
infection, JEV generally enters host cells via receptor-mediated
clathrin-dependent endocytosis that requires the 70 kDa
heat-shock protein (Hsp70). Heat-shock cognate
protein 70 (Hsc70) is one member of the Hsp70 family and is constitutively expressed; thus, it may be expressed under physiological conditions. In C6/36 cells, Hsc70 is upregulated in response to JEV
infection. Since Hsc70 shows no relationship with viruses attaching to the cell surface, it probably does not serve as the receptor according to our results in the present study. In contrast, Hsc70 is evidently associated with virus penetration into the cell and resultant acidification of intracellular vesicles. It suggests that Hsc70 is highly involved in
clathrin-mediated endocytosis, particularly at the late stage of viral entry into host cells. Furthermore, we found that Hsc70 is composed of at least three
isoforms, including B, C and D; of these,
isoform D helps JEV to penetrate C6/36 cells via
clathrin-mediated endocytosis. This study provides relevant evidence that sheds light on the regulatory mechanisms of JEV
infection in host cells, especially on the process of
clathrin-mediated endocytosis.