Post-translational loss of renal TRPV5 calcium channel expression, Ca(2+) wasting, and bone loss in experimental colitis

Gastroenterology. 2013 Sep;145(3):613-24. doi: 10.1053/j.gastro.2013.06.002. Epub 2013 Jun 5.


Background & aims: Dysregulated Ca(2+) homeostasis likely contributes to the etiology of inflammatory bowel disease-associated loss of bone mineral density. Experimental colitis leads to decreased expression of Klotho, a protein that supports renal Ca(2+) reabsorption by stabilizing the transient receptor potential vanilloid 5 (TRPV5) channel on the apical membrane of distal tubule epithelial cells.

Methods: Colitis was induced in mice via administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) or transfer of CD4(+)interleukin-10(-/-) and CD4(+), CD45RB(hi) T cells. We investigated changes in bone metabolism, renal processing of Ca(2+), and expression of TRPV5.

Results: Mice with colitis had normal serum levels of Ca(2+) and parathormone. Computed tomography analysis showed a decreased density of cortical and trabecular bone, and there was biochemical evidence for reduced bone formation and increased bone resorption. Increased fractional urinary excretion of Ca(2+) was accompanied by reduced levels of TRPV5 protein in distal convoluted tubules, with a concomitant increase in TRPV5 sialylation. In mouse renal intermedullary collecting duct epithelial (mIMCD3) cells transduced with TRPV5 adenovirus, the inflammatory cytokines tumor necrosis factor, interferon-γ, and interleukin-1β reduced levels of TRPV5 on the cell surface, leading to its degradation. Cytomix induced interaction between TRPV5 and UBR4 (Ubiquitin recoginition 4), an E3 ubiquitin ligase; knockdown of UBR4 with small interfering RNAs prevented cytomix-induced degradation of TRPV5. The effects of cytokines on TRPV5 were not observed in cells stably transfected with membrane-bound Klotho; TRPV5 expression was preserved when colitis was induced with TNBS in transgenic mice that overexpressed Klotho or in mice with T-cell transfer colitis injected with soluble recombinant Klotho.

Conclusions: After induction of colitis in mice via TNBS administration or T-cell transfer, tumor necrosis factor and interferon-γ reduced the expression and activity of Klotho, which otherwise would protect TRPV5 from hypersialylation and cytokine-induced TRPV5 endocytosis, UBR4-dependent ubiquitination, degradation, and urinary wasting of Ca(2+).

Keywords: 2,4,6-trinitrobenzenesulfonic acid; ARE; AU-rich elements; BMD; FECa(2+); IBD; IFN; IL; Mouse Model; Osteoporosis; TNBS; TNF; TRPV5; UC; Ub; Ulcerative Colitis; bone mineral density; eGFP; enhanced green flourescent protein; fractional excretion of Ca(2+); inflammatory bowel disease; interferon; interleukin; mIMCD3; mRNA; messenger RNA; mouse renal intermedullary collecting duct epithelial cells; siRNA; small interfering RNA; transient receptor potential vanilloid 5; tumor necrosis factor; ubiquitin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biomarkers / metabolism
  • Bone Density*
  • CD4-Positive T-Lymphocytes / transplantation
  • Calcium / metabolism*
  • Calcium Channels / metabolism*
  • Colitis / chemically induced
  • Colitis / immunology
  • Colitis / metabolism*
  • Glucuronidase / metabolism
  • Interferon-gamma / metabolism
  • Kidney / metabolism*
  • Mice
  • Mice, Transgenic
  • Protein Processing, Post-Translational*
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • TRPV Cation Channels / metabolism*
  • Tomography, X-Ray Computed
  • Trinitrobenzenesulfonic Acid
  • Tumor Necrosis Factor-alpha / metabolism


  • Biomarkers
  • Calcium Channels
  • TRPV Cation Channels
  • Trpv5 protein, mouse
  • Tumor Necrosis Factor-alpha
  • Interferon-gamma
  • Trinitrobenzenesulfonic Acid
  • Glucuronidase
  • klotho protein
  • Calcium