Urothelial endocytic vesicles recycling and lysosomal degradative pathway regulated by the lipid membrane composition.

GRASSO EJ; CALDERON RO

HISTOCHEMISTRY AND CELL BIOLOGY.

SPRINGER

Lugar: Berlin; Año: 2012

0948-6143

The urothelium, a specialized epithelium that covers the mucosa cell surface of the urinary bladder, undergoes dramatic morphological changes during the micturition cycle that involve a membrane apical traffic. This traffic was first described as a lysosomal pathway, in addition to the known endocytosis/exocytosis membrane recycling. In an attempt to understand the role of membrane lipid composition in those effects, we previously described the lipid-dependet leakage of the endocytosed vesicle content. In this work we demonstrated clear differences in the traffic of both the fluid-probe and the membrane-bound probe in urothelial umbrella cells by using spectrofluorometry and/or confocal and epifluorescence microscopy. Different membrane lipid composition was established by using three diet formulae enriched in oleic acid, linoleic acid and a commercial formula. Between 3 and 5 animals of each dietary treatment were used for each analysis. The decreased endocytosis of both fluid and membrane-bound probes (approx. 32% and 49% lower, respectively) in oleic acid-derived umbrella cells was concomitant with an increased recycling (approx. 4.0 and 3.7 times, respectively) and diminished sorting to the lysosome (approx. 23 % and 37%, respectively) when compared to control umbrella cells. The higher intravesicular pH and the impairment of the lysosomal pathway of OAV (oleic acid-diet derived vesicles) compared to LAV (linoleic acid-diet derived vesicles) and CV (control-diet derived vesicles) correlates with our findings of a lower V-ATPase activity previously reported. We integrated the results obtained in the present and previous work in order to determine the sorting of endocytosed material (fluid and membrane-bound probes) into the different cell compartments. Finally the weighted average effect of the individual alterations on the intracellular distribution was evaluated. The results shown in this work add evidences for the modulatory role of the membrane lipid composition on sorting of the endocytosed material. This suggests that changes on the membrane organization can be one of the underlying mechanism for regulating the endocytosis/exocytosis processes and membrane intracellular trafficking.