title: Hypercompliant apical membranes of bladder umbrella cells.
abstract: Urinary bladder undergoes dramatic volume changes during filling and voiding cycles. In the bladder the luminal surface of terminally differentiated urothelial umbrella cells is almost completely covered by plaques. These plaques (500 to 1000 nm) are made of a family of proteins called uroplakins that are known to form a tight barrier to prevent leakage of water and solutes. Electron micrographs from previous studies show these plaques to be interconnected by hinge regions to form structures that appear rigid, but these same structures must accommodate large changes in cell shape during voiding and filling cycles. To resolve this paradox, we measured the stiffness of the intact, living urothelial apical membrane and found it to be highly deformable, even more so than the red blood cell membrane. The intermediate cells underlying the umbrella cells do not have uroplakins but their membranes are an order of magnitude stiffer. Using uroplakin knockout mouse models we show that cell compliance is conferred by uroplakins. This hypercompliance may be essential for the maintenance of barrier function under dramatic cell deformation during filling and voiding of the bladder.
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts. Electronic address: jmathai@bidmc.harvard.edu.
authors.forename: John C
authors.initials: JC
authors.lastname: Mathai
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts.
authors.forename: Enhua H
authors.initials: EH
authors.lastname: Zhou
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Weiqun
authors.initials: W
authors.lastname: Yu
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts.
authors.forename: Jae Hun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Cell Biology, New York University, New York, New York.
authors.forename: Ge
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Department of Cell Biology, New York University, New York, New York.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liao
authors.affiliation: Department of Cell Biology, New York University, New York, New York.
authors.forename: Tung-Tien
authors.initials: TT
authors.lastname: Sun
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Fredberg
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Zeidel
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D055595:Mechanical Phenomena; D051379:Mice; D011479:Protamines / Q000494:pharmacology; D001743:Urinary Bladder / Q000166:cytology* / Q000187:drug effects
chemical_list: D000199:Actins; D011479:Protamines