Apoptosis-inducing factor 1 mediates Vibrio splendidus-induced coelomocyte apoptosis via importin β dependent nuclear translocation in Apostichopus japonicus

As is well known, apoptosis is an important form of immune response and immune regulation, particularly playing a crucial role in combating microbial infections. Apoptosis-inducing factor 1 (AIF-1) is essential for apoptosis to induce chromatin condensation and DNA fragmentation via a caspase-independent pathway. The nuclear translocation of AIF-1 is a key step in apoptosis but the molecular mechanism is still unclear. In this study, the homologous gene of AIF-1, named Aj AIF-1, was cloned and identified in Apostichopus japonicus . The mRNA expression of Aj AIF-1 was significantly increased by 46.63-fold after Vibrio splendidus challenge. Silencing of Aj AIF - 1 was found to significantly inhibit coelomocyte apoptosis because the apoptosis rate of coelomocyte decreased by 0.62-fold lower compared with the control group. Aj AIF-1 was able to promote coelomocyte apoptosis through nuclear translocation under the V. splendidus challenge. Moreover, Aj AIF-1 and Aj importin beta were mainly co-localized around the nucleus in vivo and silencing Aj importin beta significantly inhibited the nuclear translocation of Aj AIF-1 and suppressed coelomocyte apoptosis by 0.64-fold compared with control. In summary, nuclear translocation of Aj AIF-1 will likely mediate coelomocyte apoptosis through an importin beta -dependent pathway in sea cucumber.