Uroplakins in urothelial biology, function, and disease.
Urothelium covers the inner surfaces of the renal pelvis, ureter, bladder, and prostatic urethra. Although morphologically similar, the urothelia in these anatomic locations differ in their embryonic origin and lineages of cellular differentiation, as reflected in their different uroplakin content, expandability during micturition, and susceptibility to chemical carcinogens. Previously thought to be an inert tissue forming a passive barrier between the urine and blood, urothelia have recently been shown to have a secretory activity that actively modifies urine composition. Urothelial cells express a number of ion channels, receptors, and ligands, enabling them to receive and send signals and communicate with adjoining cells and their broader environment. The urothelial surface bears specific receptors that not only allow uropathogenic E. coli to attach to and invade the bladder mucosa, but also provide a route by which the bacteria ascend through the ureters to the kidney to cause pyelonephritis. Genetic ablation of one or more uroplakin genes in mice causes severe retrograde vesicoureteral reflux, hydronephrosis, and renal failure, conditions that mirror certain human congenital diseases. Clearly, abnormalities of the lower urinary tract can impact the upper tract, and vice versa, through the urothelial connection. In this review, we highlight recent advances in the field of urothelial biology by focusing on the uroplakins, a group of urothelium-specific and differentiation-dependent integral membrane proteins. We discuss these proteins' biochemistry, structure, assembly, intracellular trafficking, and their emerging roles in urothelial biology, function, and pathological processes. We also call attention to important areas where greater investigative efforts are warranted.
Wu
Xue-Ru
XR
Department of Urology, New York University Langone Medical Center, New York, New York, USA; Department of Pathology, New York University Langone Medical Center, New York, New York, USA; Veterans Affairs New York Harbor Healthcare Systems, Manhattan Campus, New York, New York, USA. Electronic address: xue-ru.wu@med.nyu.edu.
Kong
Xiang-Peng
XP
Department of Biochemistry, New York University Langone Medical Center, New York, New York, USA.
Pellicer
Angel
A
Department of Pathology, New York University Langone Medical Center, New York, New York, USA.
Kreibich
Gert
G
Department of Cell Biology, New York University Langone Medical Center, New York, New York, USA.
Sun
Tung-Tien
TT
Department of Urology, New York University Langone Medical Center, New York, New York, USA; Department of Cell Biology, New York University Langone Medical Center, New York, New York, USA; Department of Dermatology, New York University Langone Medical Center, New York, New York, USA; Department of Pharmacology, New York University Langone Medical Center, New York, New York, USA. Electronic address: sunt01@nyumc.org.