Different rabies virus (RABV) strains have their own biological characteristics, but little is known about their respective impact on autophagy. Therefore, we evaluated whether attenuated RABV HEP-Flury and wild-type RABV GD-SH-01 strains triggered autophagy. We found that GD-SH-01 infection significantly increased the number of autophagy-like vesicles, the accumulation of enhanced green fluorescent protein (EGFP)-LC3 fluorescence puncta and the conversion of LC3-I to LC3-II, while HEP-Flury was not able to induce this phenomenon. When evaluating autophagic flux, we found that GD-SH-01 infection triggers a complete autophagic response in the human neuroblastoma cell line (SK), while autophagosome fusion with lysosomes was inhibited in a mouse neuroblastoma cell line (NA). In these cells, GD-SH-01 led to apoptosis and mitochondrial dysfunction while triggering autophagy, and apoptosis could be decreased by enhancing autophagy. To further identify the virus constituent causing autophagy, 5 chimeric recombinant viruses carrying single genes of HEP-Flury instead of those of GD-SH-01 were rescued. While the HEP-Flury virus carrying the wild-type matrix protein (M) gene of RABV triggered LC3-I to LC3-II conversion in SK and NA cells, replacement of genes of nucleoprotein (N), phosphoprotein (P) and glycoprotein (G) produced only minor autophagy. But no one single structural protein of GD-SH-01 induced autophagy. Moreover, the AMPK signaling pathway was activated by GD-SH-01 in SK. Therefore, our data provide strong evidence that autophagy is induced by GD-SH-01 and can decrease apoptosis in vitro. Furthermore, the M gene of GD-SH-01 may cooperatively induce autophagy.
Keywords: apoptosis; autophagic flux; autophagosome; autophagy; matrix protein; rabies virus.