Urothelial endocytic vesicle recycling and lysosomal degradative pathway regulated by lipid membrane composition

Abstract

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-dependent 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 compositions were established by using three diet formulae enriched in oleic acid, linoleic acid and a commercial formula. Between three and five animals for each dietary treatment were used for each analysis. The decreased endocytosis of both fluid and membrane-bound probes (approximately 32 and 49 % lower, respectively) in oleic acid-derived umbrella cells was concomitant with an increased recycling (approximately 4.0 and 3.7 times, respectively) and diminished sorting to the lysosome (approximately 23 and 37 %, respectively) when compared with the control umbrella cells. The higher intravesicular pH and the impairment of the lysosomal pathway of oleic acid diet-derived vesicles compared to linoleic acid diet-derived vesicles and control diet-derived vesicles correlate with our findings of a lower V-ATPase activity previously reported. We integrated the results obtained in the present and previous work 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 in the membrane organization can be one of the underlying mechanisms for regulating the endocytosis/exocytosis processes and membrane intracellular trafficking.

The urothelium of a hibernator: the American black bear

“…; Burton et al. ; Grasso and Calderon , ; Khandelwal et al. ) and Grasso has described endosomal release of fluid contents into cytosol (Grasso and Calderon ).…”

“…; Ulluwishewa et al. ), membrane solute transporters (Ma and Eaton ; Dopico and Bukiya ), and even endocytic vessel formation and permeability (Grasso and Calderon , ). For hibernating bears dietary fat has special importance and significance.…”

“…), the structural array and size of uroplakin proteins comprising the urothelial plaques (Calderon and Grasso ) the thickness and ultrastructural asymmetry of the apical and vesicular membranes (Kalinec et al. ), the pathways and rates of endocytic recycling from apical membranes (Grasso and Calderon ), and the permeability of endocytic vessels obtained from rat umbrella cell apical membranes (Grasso and Calderon ). Finally, investigators have demonstrated in small hibernating mammals that the composition of dietary fats during fall hyperphagia influences the fatty acid composition of tissue depot fats and cellular membranes as well as patterns of hibernation and torpor (Aloia and Raison ; Geiser et al.…”

Properties of the Urothelium that Establish the Blood–Urine Barrier and Their Implications for Drug Delivery

“…Furthermore, endocytosis, vesicle recycling, and lysosomal degradation are also influenced by lipid membrane composition. Compared to controls, oleic acid-derived superficial UCs have been shown to display decreased endocytosis of fluid and membrane-bound probes by 32% and 49%, respectively (Grasso and Calderon 2013). In addition to altered intracellular vesicle trafficking, endocytosed vesicles are capable of releasing their content, and the lipid membrane composition can affect the degree of leakage into the cytoplasm (Grasso and Calderon 2009).…”

Regulation of the orexigenic neuropeptide, enkephalin, by PPARδ and fatty acids in neurons of the hypothalamus and forebrain

“…Whereas PA in both hypothalamic and forebrain neurons fails to stimulate protein levels of PPARd despite an increase in mRNA, OA stimulates both protein and mRNA levels of PPARd in forebrain neurons. While this higher level of PPARd protein activity may then inhibit the expression of ENK, its failure to completely reverse the OA-induced increase in ENK protein may be because of other effects of this fatty acid on regulatory processes, such as a decrease in protein exocytosis and degradation (Kudo et al 2006;Grasso and Calderon 2013). It may also reflect other proteins besides PPARd, such as the transcription enhancer factor-1 and Yes-associated protein, which are affected by a HFD and positively or negatively regulate ENK expression and levels (Poon et al 2013).…”