Characterization and functional analysis of GSK3ß from Epinephelus coioides in Singapore grouper iridovirus infection.

ABSTRACT

Glycogen synthase kinase 3ß (GSK3ß), a serine/threonine protein kinase, is a crucial regulator of several signaling pathways and plays a vital role in cell proliferation, growth, apoptosis, and immune responses. However, the role of GSK3ß during viral infection in teleosts remains largely unknown. In the present study, a GSK3ß homologue from Epinephelus coioides (EcGSK3ß) was cloned and characterized. The open reading frame of EcGSK3ß consists of 1323 bp, encoding a 440 amino acid protein, with a predicted molecular mass of 48.23 kDa. Similar to its mammalian counterpart, EcGSK3ß contains an S_TKc domain. EcGSK3ß shares 99.77% homology with the giant grouper (Epinephelus lanceolatus). Quantitative real-time PCR analysis indicated that EcGSK3ß mRNA was broadly expressed in all tested tissues, with abundant expression in the skin, blood, and intestines. Additionally, the expression of EcGSK3ß increased after Singapore grouper iridovirus (SGIV) infection in grouper spleen (GS) cells. Intracellular localization analysis demonstrated that EcGSK3ß is mainly distributed in the cytoplasm. EcGSK3ß overexpression promoted SGIV replication during viral infection in vitro. In contrast, silencing of EcGSK3ß inhibited SGIV replication. EcGSK3ß significantly downregulated the activities of interferon-ß, interferon-sensitive response element, and NF-κB. Taken together, these findings are important for a better understanding of the function of GSK3ß in fish and reveal its involvement in the host response to viral immune challenge.