Stretch-regulated Exocytosis/Endocytosis in Bladder Umbrella Cells

Steven T. Truschel, Edward Wang, Wily G. Ruiz, Som-Ming Leung, Raul Rojas, John Lavelle, Mark Zeidel, David Stoffer, Gerard Apodaca, Howard Riezman
2002 Molecular Biology of the Cell  
The epithelium of the urinary bladder must maintain a highly impermeable barrier despite large variations in urine volume during bladder filling and voiding. To study how the epithelium accommodates these volume changes, we mounted bladder tissue in modified Ussing chambers and subjected the tissue to mechanical stretch. Stretching the tissue for 5 h resulted in a 50% increase in lumenal surface area (from ϳ2900 to 4300 m 2 ), exocytosis of a population of discoidal vesicles located in the
more » ... l cytoplasm of the superficial umbrella cells, and release of secretory proteins. Surprisingly, stretch also induced endocytosis of apical membrane and 100% of biotinlabeled membrane was internalized within 5 min after stretch. The endocytosed membrane was delivered to lysosomes and degraded by a leupeptin-sensitive pathway. Last, we show that the exocytic events were mediated, in part, by a cyclic adenosine monophosphate, protein kinase A-dependent process. Our results indicate that stretch modulates mucosal surface area by coordinating both exocytosis and endocytosis at the apical membrane of umbrella cells and provide insight into the mechanism of how mechanical forces regulate membrane traffic in nonexcitable cells. Article published online ahead of print. Mol. Biol. Cell 10.1091/ mbc.01-09 -0435. Article and publication date are at www.molbiolcell.org/cgi/
doi:10.1091/mbc.01-09-0435 pmid:11907265 pmcid:PMC99602 fatcat:zgujbngiabhldg5dyiyfs2qbri