Moreover other E5 indirect mechanisms may be hypothesised based on its complex modulation
of cell proteome and membrane lipids and proteins composition [45–47]. Following the infection with a retrovirus construct bearing the HPV-16 E5 sequence, the E5 specific selleck chemicals llc mRNA could be consistently detected in FRM and M14 cells up to thirty days post infection. The E5 viral specific mRNA was expressed at a level comparable with the one of the GAPDH housekeeping reference gene. The E5 expression was well tolerated with almost no cytotoxic effect and no modification of cell morphology. Expectedly, as revealed by experiments with AO, the E5 expression was associated with a relevant modification of the endocellular pH and with a neat re-activation of the tyrosinase enzyme. These data are in favour of the hypothesis that E5 protein does indeed act through an interaction with 16 kDa subunit c of the V0-ATPase sub-complex. In fact, in amelanotic melanomas the most of tyrosinase and of other melanogenic
learn more proteins, instead of being transported to the Golgi and endosomes for further processing and glicosilation, due to the acidic environment, are retained in the ER where they are rapidly degraded by proteasome . Conversely, the maturation of tyrosinase to the enzymatically active form (figure 4b) indicate the elevation of the endocellular pH to a near neutral value following the V-ATPase complex inhibition thus supporting the hypothesis of an interaction of the E5 Dynein with the 16 kDa sub unit c. This interaction could reasonably
occurs in the ER where the 16 kDa V-ATPase subunit is synthesized and where most of E5 is localized. However we could not provide a positive evidence for a direct interaction and, considering the multifaceted cellular effects of E5, other indirect mechanisms may be envisioned. Namely the modifications of membrane lipids compositions and functions [45, 46] and the deep modifications of cell transcriptome , both obtained in HaCaT cells, have the potentials, either alone or in combination, to modulate the proteins and organellar functions without implying any direct physical E5/subunit c interaction. The E5 expressing cells proved able to sustain the melanin deposition and to survive in anchorage independent culture conditions (figure 4c) thus confirming and extending the observation on mouse embryo fibroblasts  and human epithelial HaCaT cells  already reported.