Abstract
Caveolae are flask-shaped invaginations of the plasma membrane. Caveolae play important roles in the process of viruses entry into host cells, but the roles of caveolae at the late stage of virus infection were not completely understood. Tiger frog virus (TFV) has been isolated from the diseased tadpoles of the frog, Rana tigrina rugulosa, and causes high mortality of tiger frog tadpoles cultured in Southern China. In the present study, the roles of caveolae at the late stage of TFV infection were investigated. We showed that TFV virions were localized with the caveolae at the late stage of infection in HepG2 cells. Disruption of caveolae by methyl-β-cyclodextrin/nystatin or knockdown of caveolin-1 significantly increase the release of TFV. Moreover, the interaction between caveolin-1 and TFV major capsid protein was detected by co-immunoprecipitation. Those results suggested that caveolae restricted TFV release from the HepG2 cells. Caveolae-associated proteins (caveolin-1, caveolin-2, cavin-1, and cavin-2) were selectively incorporated into TFV virions. Different combinations of proteolytic and/or detergent treatments with virions showed that caveolae-associated proteins were located in viral capsid of TFV virons. Taken together, caveolae might be a restriction factor that affects virus release and caveolae-associated proteins were incorporated in TFV virions.
Highlights
Morphology and cell type[15]
Caveolin-1 demonstrated punctuate staining pattern that is mainly localized in the plasma membrane of uninfected HepG2 cells (Fig.1A, Con, red fluorescence), which is consistent with its known localization in clustered caveolae microdomains[33]
The results suggested that tiger frog virus (TFV) colocalize with caveolae started at 60 h postinfection, indicating TFV detected in caveolae represent newly formed viruses but not the ones have entered inside the host cells
Summary
Morphology and cell type[15]. Cavin proteins function primarily as scaffolding and regulate caveolin availability[16]. Caveolae are a subset of lipid rafts, but the roles of caveolae at the late stage of virus infection not completely understood. The first reported complete genome sequence in the genus Ranavirus is tiger frog virus (TFV). TFV is isolated from the infected tadpoles of Rana tigrina rugulosa, causes high mortality rate among tiger frog tadpoles cultured in Southern China[30]. Infectious spleen and kidney necrosis virus (a megalocytivirus) enters mandarin fish fry (MFF-1) cells through a caveolae-dependent endocytic pathway and may colocalize with caveolin-131. The roles of caveolae at the late stage of virus infection are explored, and the major structural proteins of caveolae are identified incorporated into TFV virions
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