Aberrant localization of ezrin correlates with salivary acini disorganization in Sjögren’s Syndrome

Objectives. To analyse whether the alterations in the structure and organization of microvilli in salivary acinar cells from SS patients are linked to changes in the expression and/or cellular localization of ezrin. Methods. Salivary gland (SG) acini from controls and SS patients were used to evaluate ezrin expression by western blot and localization of total and activated (phospho-Thr567) ezrin by IF and EM. Results. In acini from control labial SGs, ezrin was located predominantly at the apical pole and to a lesser extent at the basal region of these cells. Conversely, in acini extracts from SS patients, ezrin showed significantly elevated levels, which were accompanied with localization mostly at the basal region. Moreover, F-actin maintained its distribution in both the apical region and basolateral cortex; however, it was also observed in the acinar cytoplasm. Phospho-ezrin (active form) was located exclusively at the apical pole of acinar cells from control subjects and abundantly located at the basal cytoplasm in SS samples. These results were confirmed by immunogold studies. Conclusions. The decrease of ezrin and phospho-ezrin at the apical pole and the cytoplasmic redistribution of F-actin suggest an altered interaction between the F-actin-cytoskeleton and plasma membrane in SS patient acini, which may explain the microvilli disorganization. These alterations could eventually contribute to SG hyposecretion in SS patients.Supported by grants (to M.-J.G., S.A. and C.M.) FONDECYT-CHILE 1080006, 1050192. P.P. and M.B. were supported by PhD fellowships granted by Conicyt, Mecesup-Postgrade University of Chile 99-03