CONICET | Buscador de Institutos y Recursos Humanos

Human Papillomavirus (HPV) E6 oncoproteins have the ability to bind PDZ-domain proteins involved in the organization of cell junctions. Loss of cell polarity is a hallmark for carcinoma development and the regulation of cell polarity depends, in part, of the integrity of cell tight junctions (TJ). For investigating the interference of HPV E6 proteins with TJ structures we analyzed in HPV E6-expressing cells the level and distribution of components of the Par polarity complex, a key element in this kind of junction. By inmunofluorescence assays we observed that the transient or stable expression of high risk HPVs E6 proteins alters the composition of this protein complex at the cell borders. Furthermore, cell polarity also requires the correct distribution of membrane Phosphoinositide (PIP) lipids that, in addition, are involved in signal transduction. It has been demonstrated that some PDZ proteins present in TJ interact with this type of lipids and this PDZ-lipid interaction is relevant for PIP proper distribution. Therefore, we wanted to address if E6-PDZ binding could interfere with PIPs localization and function. For this purpose, we analyzed the differences in PIP distribution in the presence and absence of E6 proteins using a PIP fluorescent biosensor. We have shown that E6 protein expression induces PIPs mislocalization reducing their presence at the cell borders and, moreover, this alteration was not observed for HPV11 E6 protein that has not the ability to bind PDZ domains. Furthermore, cells derived from HPV associated tumours showed a completely altered pattern of PIP localization with a punctuated cytoplasmic distribution. The importance of these findings in cell polarity maintenance and signal transduction pathways will be discussed.