Zebrafish TDP43 positively regulates p65-mediated apoptotic pathway

TAR DNA-binding protein 43 (TDP43) is a multifunctional RNA/DNA binding protein that serves as a hallmark of neurodegeneration in amyotrophic lateral sclerosis (ALS) and is associated with the inflammatory response related to nuclear factor κB (NF-κB) pathway. However, the relationship between TDP43 and NF-κB is not well known. In this study, zebrafish TDP43 (DrTDP43) can be induced by grass carp reovirus (GCRV) or spring viremia of carp virus (SVCV). DrTDP43 enhances the nuclear factor-kappaB (NF-κB) activity and the expression of p65 and TNFα, as well as promotes the phosphorylation of p65 in response to stimulation of GCRV and SVCV. Further assays indicate that DrTDP43 primarily resides in the nucleus and interacts with p65 via its RRM1. DrTDP43 is required for p65 to induce pro-inflammatory cytokine production (IL-6, IL-10, TNFα, IL-1β). It disrupts mitochondrial membrane potential and exacerbates apoptosis via downregulating Bcl2 and upregulating Bax, caspase3, and eIF2α. Moreover, knockdown of TDP43 decreases the content of reactive oxygen species (ROS) and the number of apoptotic cells in zebrafish larvae, which is attributed to the lower lever of p65 phosphorylation and expression of TNFα, Bax and cleaved-caspase3. In a word, these results establish TDP43 as a critical activator of the NF-κB-mediated apoptotic pathway during antiviral responses, which reveals a previously unrecognized host defense mechanism.