Soft-shelled turtle iridovirus enters cells via cholesterol-dependent, clathrin-mediated endocytosis as well as macropinocytosis
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Ranaviruses are nucleoplasmic large DNA viruses that can cause major economic losses in the aquaculture industry and pose a severe threat to global ecological diversity. The available literature demonstrates that classifiable members of the genus Ranavirus enter cells via multiple and complicated routes. Here, we demonstrated the underlying cellular entry mechanism of soft-shelled turtle iridovirus (STIV) using green fluorescence tagged recombinant virus. Treatment with chlorpromazine, sucrose, ethyl-isopropyl amiloride, chloroquine or bafilomycin A1 all significantly decreased STIV infection, suggesting that STIV uses clathrin-mediated endocytosis and macropinocytosis to enter cells via a pH-dependent pathway. Depletion of cellular cholesterol with methyl-β-cyclodextrin significantly inhibited STIV entry, but neither filipin III nor nystatin did, suggesting that STIV entry was cholesterol dependent but caveola independent. Treatment with dynasore, genistein, ML-7 or cytochalasin D all significantly inhibited STIV infection, indicating that Rac GTPase and myosin II activity were required for the macropinocytosis-like pathway as well as actin polymerization. Our findings suggest that the molecular events involved in STIV entry are not identical to those of other ranavirus isolates. Our results also extend our understanding of the molecular mechanism of iridovirus entry and pathogenesis.
We thank Jianlin Zhang for his help with flow cytometry analysis.
This work was supported by grants from the National Natural Science Foundation of China (31172445), National Key R&D Program of China” (2017YFC1404504), and the Knowledge Innovation Program of the Chinese Academy of Sciences (SQ201014).
Compliance with ethical standards
Conflict of interest
All the authors have no conflict of interest to declare.
This article does not contain any studies with human participants or animals performed by any of the authors.
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