title: Uromodulin upregulates TRPV5 by impairing caveolin-mediated endocytosis.
abstract: Uromodulin (UMOD) is synthesized in the thick ascending limb and secreted into urine as the most abundant protein. Association studies in humans suggest protective effects of UMOD against calcium-containing kidney stones. Mice carrying mutations of Umod found in human UMOD-associated kidney disease (UAKD) and Umod-deficient mice exhibit hypercalciuria. The mechanism for UMOD regulation of urinary Ca(2+) excretion is incompletely understood. We examined if UMOD regulates TRPV5 and TRPV6, channels critical for renal transcellular Ca(2+) reabsorption. Coexpression with UMOD increased whole-cell TRPV5 current density in HEK293 cells. In biotinylation studies, UMOD increased TRPV5 cell-surface abundance. Extracellular application of purified UMOD upregulated TRPV5 current density within physiological relevant concentration ranges. UMOD exerted a similar effect on TRPV6. TRPV5 undergoes constitutive caveolin-mediated endocytosis. UMOD had no effect on TRPV5 in a caveolin-1-deficient cell line. Expression of recombinant caveolin-1 in these cells restored the ability of UMOD to upregulate TRPV5. Secretion of UAKD-mutant UMOD was markedly reduced and coexpression of mutant UMOD with TRPV5 failed to increase its current. Immunofluorescent studies demonstrated lower TRPV5 expression in Umod(-/-) mice compared with wild-type. UMOD upregulates TRPV5 by acting from extracellular and by decreasing endocytosis of TRPV5. The stimulation of Ca(2+) reabsorption via TRPV5 by UMOD may contribute to protection against kidney-stone formation.
authors: Division of Pediatric Nephrology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9063, USA. matthias.wolf@utsouthwestern.edu
authors: Matthias T F
authors: MT
authors: Wolf
authors: Xue-Ru
authors: XR
authors: Wu
authors: Chou-Long
authors: CL
authors: Huang
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004705:Endocytosis; D057809:HEK293 Cells; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D018345:Mice, Knockout; D015398:Signal Transduction; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation; D058949:Uromodulin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D050916:TRPV Cation Channels; C120776:TRPV6 channel; C492240:Trpv5 protein, mouse; C548612:UMOD protein, human; C548613:Umod protein, mouse; D058949:Uromodulin