Induction of caspase-dependent apoptosis by betanodaviruses GGNNV and demonstration of protein alpha as an apoptosis inducer.
Betanodaviruses, members of the Nodaviridae family, are the causative agents of viral nervous necrosis in fish and infection by which cause high mortality in larvae and juveniles in a wide range of marine fish species in Asia, Europe, Australia, Martinique, and Tahit. Greasy grouper (Epinephelus tauvina) nervous necrosis viruses (GGNNV) were investigated for their apoptotic activity in culture cells. GGNNV infection of sea bass (SB) cells appeared to induce a typical cytopathic effect (CPE), i.e., cytoplasmic vacuolation, thinning, rounding up, detachment of infected cells from the cultured dish, and eventually cell lysis and death. The infected SB cells underwent DNA fragmentation and stained positive in terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) assay, suggesting that GGNNV infection induced apoptosis in SB cells. In addition, GGNNV-infected SB cells showed an increased activity of caspase-8-like proteases (IETDase) and caspase-3-like proteases (IETDase), whereas inhibitor of caspase-8 and caspase-3 reduced GGNNV-induced apoptosis. This suggests that GGNNV may promote apoptosis via the extrinsic pathway in SB cells. Protein alpha, the precursor of GGNNV capsid proteins, was transiently expressed in SB and Cos-7 cells. The DNA fragmentation and TUNEL positive signal were apparent in SB and Cos-7 cells expressing protein alpha, suggesting that protein alpha may serve as an apoptotic inducer in these cells. Moreover, expression of protein alpha resulted in the activation of caspase-3-like proteases in both cells, which could be inhibited by a caspase-3-like protease specific inhibitor DEVD-CHO peptide. These results suggest that fish caspases are important elements in GGNNV-meditated apoptosis.
Guo
Yan Xiang
YX
Temasek Life Sciences Laboratory, The National University of Singapore, 117604 Singapore.
Wei
Ting
T
Dallmann
Klara
K
Kwang
Jimmy
J
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001492:Bass; D019556:COS Cells; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis*; D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D053938:DNA Fragmentation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism; D005399:Fishes; D020287:In Situ Nick-End Labeling; D030381:Nodaviridae / Q000502:physiology*; D010447:Peptide Hydrolases / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
D036022:Capsid Proteins; D004791:Enzyme Inhibitors; D011498:Protein Precursors; D010447:Peptide Hydrolases; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; C108711:DEVDase