Role of membrane proteins in permeability barrier function: uroplakin ablation elevates urothelial permeability

American Journal of Physiology - Renal Physiology - Tập 283 Số 6 - Trang F1200-F1207 - 2002
Ping Hu1, Susan Meyers2, Feng‐Xia Liang1, Fang‐Ming Deng1, Bechara Kachar3, Mark L. Zeidel2, Tung‐Tien Sun1
1Ronald O. Perelman Department of Dermatology and Departments of Pharmacology and Urology, Kaplan Comprehensive Cancer Center, New York University School of Medicine, New York, New York 10016;
2Departments of Medicine and Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; and
3Laboratory of Cellular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892.

Tóm tắt

Although water, small nonelectrolytes, and gases are freely permeable through most biological membranes, apical membranes of certain barrier epithelia exhibit extremely low permeabilities to these substances. The role of integral membrane proteins in this barrier function has been unclear. To study this problem, we have ablated the mouse gene encoding uroplakin III (UPIII), one of the major protein subunits in urothelial apical membranes, and measured the permeabilities of these membranes. Ablation of the UPIII gene greatly diminishes the amounts of uroplakins on the apical urothelial membrane (Hu P, Deng FM, Liang FX, Hu CM, Auerbach AB, Shapiro E, Wu XR, Kachar B, and Sun TT. J Cell Biol151: 961–972, 2000). Our results indicate that normal mouse urothelium exhibits high transepithelial resistance and low urea and water permeabilities. The UPIII-deficient urothelium exhibits a normal transepithelial resistance (normal 2,024 ± 122, knockout 2,322 ± 114 Ω · cm2; P > 0.5). However, the UPIII-deficient apical membrane has a significantly elevated water permeability (normal 0.91 ± 0.06, knockout 1.83 ± 0.14 cm/s × 10−5; P < 0.05). The urea permeability of the UPIII-deficient membrane also increased, although to a lesser extent (normal 2.22 ± 0.24, knockout 2.93 ± 0.31 cm/s × 10−6; P = 0.12). These results indicate that reduced targeting of uroplakins to the apical membrane does not significantly alter the tight junctional barrier but does double the water permeability. We provide the first demonstration that integral membrane proteins contribute to the apical membrane permeability barrier function of urothelium.

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American Journal of Physiology - Renal Physiology

Tập 283 Số 6

F1200-F1207

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