Rabies virus phosphoprotein P5 binding to BECN1 regulates self-replication by CASP2-mediated autophagy signaling pathway

Background Rabies virus (RABV) is reported to encode five phosphoproteins (P), which are involved in viral genomic replication, axonal transport, oxidative stress, interferon antagonism, and autophagy induction. However, the functions of the different P proteins are poorly understood. Methods Immunofluorescence staining and western blot were performed to detect the autophagy activity, the form of ring-like structure, and the colocalization of BECN1 and P. Coimmunoprecipitation was performed to detect the interaction between P and BECN1. QRT-PCR and TCID50 assay were performed to detect the replication level of RABV. Small interfering RNA was used to detect the autophagy signaling pathway. Results We found that P5 attaches to N-terminal residues 1–139 of BECN1 (beclin1) on the BECN1 ring-like structure through amino acid residues 173–222 of P5. Subsequently, we found that P5-induced autophagosomes did not fuse with lysosomes. Becn1 silencing did not recover P5 overexpression-induced promotion of RABV replication. Mechanistically, RABV protein PΔN82 (P5) induced incomplete autophagy via the CASP2 (caspase2)-mediated signaling pathway Conclusions Our data indicate that P5 binding to the BECN1 ring benefits RABV replication by inducing CASP2 signaling pathway-dependent incomplete autophagy, which provides a potential target for antiviral drugs against RABV.