Structural and functional analysis of virus factories purified from Rabbit vesivirus-infected Vero cells.

Rabbit vesivirus infection induces membrane modifications and accumulation of vesicular structures in the cytoplasm of infected Vero cells. Crude RaV replication complexes (RCs) have been purified and their structural and functional properties have been characterized. We show that calnexin, an ER-resident protein, RaV non-structural proteins 2AB-, 2C-, 3A-, 3B- and 3CD-like as well as viral RNAs co-localize within membranous structures which are able to replicate the endogenous RNA templates. The purified virus factories protected their viral RNA contents from microccocal nuclease degradation and were inaccessible to exogenously added synthetic transcripts. In addition, we have shown that RCs can be used to investigate uridylylation of native endogenous VPg. In contrast to the observation that the virus factories were inaccessible to RNAs, RCs were accessible to added recombinant VPg which was subsequently nucleotidylylated. Nevertheless no elongation of an RNA chain attached to native or recombinant VPg could be demonstrated.

RTP801 immunoreactivity in retinal ganglion cells and its down-regulation in cultured cells protect them from light and cobalt chloride.

RTP801, a stress-related protein, is activated by adverse environmental conditions and inhibits the activity of mammalian target of rapamycin (mTOR) in promoting oxidative stress-dependent cell death. RTP801 exists both in the mammalian retina and the lens of the eye. Here, we observed RTP801 immunoreactivity in some retinal ganglion cells. Intravitreal injection of cobalt chloride (CoCl2) to mimick hypoxia influenced retinal GFAP (glial fibrillary acidic protein) and heme oxygenase-1 (HO-1) levels, but did not affect RTP801 immunoreactivity or mRNA content relative to GAPDH. However, RTP801 mRNA was elevated when compared with Brn3a mRNA, suggesting that RTP801 is activated in stressed Brn3a retinal ganglion cells. In cultures of RGC-5 cells, RTP801 immunoreactivity was located in the cytoplasm and partly present in the mitochondria. An insult of blue light or CoCl2 increased RTP801 expression, which was accompanied by cell death. However, in cultures where RTP801 mRNA was down-regulated, the negative influence of blue light and CoCl2 was blunted. Rapamycin nullified the CoCl2-induced up-regulation of RTP801 and attenuated cell death. Moreover, rapamycin was non-toxic to RGC-5 cells, even at a high concentration (10µM). The protective effect of rapamycin on RGC-5 cells caused by the inhibition of RTP801 suggests that rapamycin might attenuate retinal ganglion cell death in situ, as in glaucoma.