An LPS-induced TNF-α factor involved in immune response of oyster Crassostrea gigas by regulating haemocytes apoptosis

LPS induced TNF-α Factor (LITAF) is a transcription factor widely involving in activation of Tumor Necrosis Factor (TNF) and other cytokines in the inflammatory response. In the present study, a homologue of LITAF with a conserved LITAF domain was identified from the Pacific oyster Crassostrea gigas. The transcripts of CgLITAF were detectable in all examined tissues with highest expression in hepatopancrease. The immunofluorescence assay and western blot showed that LPS stimulation induced an obvious nucleus translocation of CgLITAF protein in haemocytes. While the mRNA level of CgLITAF changed slightly after LPS stimulation. The siRNA of CgLITAF was injected to inhibit its expression. In the CgLITAF-RNAi group, the apoptotic level of haemocytes decreased observably after LPS stimulation. Consistently, the transcripts of CgTNFs (LOC105343080, LOC105341146), the apoptotic-related molecules including CgBax, CgCytochrome c, CgCaspase9 and CgCaspase3, were significantly suppressed in the CgLITAF-RNAi oysters. While the mRNA expression level of CgBcl was enhanced significantly in the CgLITAF-RNAi oysters. These results indicated that CgLITAF promoted haemocytes apoptosis by regulating the expression of apoptotic-related factors, suggesting its important role in the immune response of oysters.