The molecular mechanisms of the immune system against pathogens in large yellow croaker (Pseudosciaena crocea) are not well known, despite its economic importance as an aquaculture species. In this investigation, a Rab gene (named as LycRab gene) was obtained from this fish, which exhibited high homology with Rab8 of other species. It was expressed in Escherichia coli, and the specific antibody was raised using the purified fusion protein (GST-LycRab). The LycRab protein, containing characteristic signatures of Rab proteins with 5 GTP-binding domains, had GTP-binding activity. The LycRab gene was ubiquitously expressed in all analyzed tissues as revealed by Western blot, although expression levels varied from tissue to tissue. Real-time PCR revealed that the LycRab gene was up-regulated after immunization with poly I:C, formalin-inactive Gram-negative bacterium Vibrio parahaemolyticus or bacterial lipopolysaccharides (LPS), suggesting that LycRab protein might play an important role in large yellow croaker defense against pathogens infection. This discovery might contribute better understanding to the molecular events involved in fish immune responses.
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