The HPV16 E5 oncogene inhibits endocytic trafficking

The small hydrophobic E5 protein of Human Papillomavirus type 16 (HPV16) bi nds to the 16-kDa subunit of the V-H+-ATPase, This binding has been suggest ed to interfere with acidification of late endocytic structures. We here us ed video microscopy, ratio imaging and confocal microscopy of living C127 f ibroblasts to study the effects of E5, Various endocytic markers including the pH-sensitive probe DM-NERF coupled to dextran, TransFluoSpheres and TRI TC-concanavalin A, were applied. In ES-transfected cells, none of these mar kers colocalized with the membrane permeable probe Lyso-Tracker Red, which accumulates in acidic, late endocytic structures, or with a green fluoresce nt version of the small GTPase Rab7 labeling late endocytic structures. Imp ortantly, however, late endocytic structures accumulating LysoTracker were still present in the E5-transfected cells. It is therefore concluded that H PV16 E5 perturbs trafficking from early to late endocytic structures rather than acidification.