Fig. 6. TRPM7 modulates proton pumping into the lumen of the viral endosome.

a Diagram showing the use of the optogenetic tool Arch3, a light-activated proton pump that can be used to acidify endosomes in the presence of Bafilomycin. Arch3 fused to CD63 is targeted to late endosome/lysosomes. Normally, the endogenous V-ATPase pumps protons to acidify the endosomal lumen and this enables the virus to escape the endosome (left). When cells are treated with V-ATPase inhibitor Bafilomycin (50 nM), the endosome fails to acidify, and the virus stays in the endosomes (middle). But even in the presence of Bafilomycin, light-mediated activation of Arch3 acidifies the endosome and enables the virus to enter the cytosol (right). b Maximum projections of Arch3-CD63 expressing, Ctl (gray) and TRPM7 knockdown (M7KD, blue) SVG-A cells infected with VSV-G. Cells were treated with Bafilomycin (50 nM) and/or exposed to 15 µWatt 488 nm laser (60 seconds). Quantification of cells positive for infection (green) from three independent infections is shown in the right panel. P values determined by one-way ANOVA with Tukey’s multiple comparison analysis. Mean and SEM is plotted. c Maximum projections of Arch3-CD63 expressing Ctl (gray) and M7KD (blue) SVG-A cells infected with VSV-pH mutant with or without Bafilomycin (50 nM) or light stimulation (15 µWatt 488 nm, 60 seconds). Quantification of total cells positive for infection (green) from three independent infections is shown in the right panel. P values determined by one-way ANOVA with Tukey’s multiple comparison analysis. Mean and SEM is plotted.