title: The transient receptor potential channel TRPV6 is dynamically expressed in bone cells but is not crucial for bone mineralization in mice.
abstract: Bone is the major store for Ca(2+) in the body and plays an important role in Ca(2+) homeostasis. During bone formation and resorption Ca(2+) must be transported to and from bone by osteoblasts and osteoclasts, respectively. However, little is known about the Ca(2+) transport machinery in these bone cells. In this study, we examined the epithelial Ca(2+) channel TRPV6 in bone. TRPV6 mRNA is expressed in human and mouse osteoblast-like cells as well as in peripheral blood mononuclear cell-derived human osteoclasts and murine tibial bone marrow-derived osteoclasts. Also other transcellular Ca(2+) transport genes, calbindin-D(9k) and/or -D(28K), Na(+)/Ca(2+) exchanger 1, and plasma membrane Ca(2+) ATPase (PMCA1b) were expressed in these bone cell types. Immunofluorescence and confocal microscopy on human osteoblasts and osteoclasts and mouse osteoclasts revealed TRPV6 protein at the apical domain and PMCA1b at the osteoidal domain of osteoblasts, whereas in osteoclasts TRPV6 was predominantly found at the bone-facing site. TRPV6 was dynamically expressed in human osteoblasts, showing maximal expression during mineralization of the extracellular matrix. 1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) did not change TRPV6 expression in both mineralizing and non-mineralizing SV-HFO cultures. Lentiviral transduction-mediated overexpression of TRPV6 in these cells did not alter mineralization. Bone microarchitecture and mineralization were unaffected in Trpv6(D541A/D541A) mice in which aspartate 541 in the pore region was replaced with alanine to render TRPV6 channels non-functional. In summary, TRPV6 and other proteins involved in transcellular Ca(2+) transport are dynamically expressed in bone cells, while TRPV6 appears not crucial for bone metabolism and matrix mineralization in mice.
authors: Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands.
authors: Bram C J
authors: BC
authors: van der Eerden
authors: Petra
authors: P
authors: Weissgerber
authors: Nadja
authors: N
authors: Fratzl-Zelman
authors: Jenny
authors: J
authors: Olausson
authors: Joost G J
authors: JG
authors: Hoenderop
authors: Marijke
authors: M
authors: Schreuders-Koedam
authors: Marco
authors: M
authors: Eijken
authors: Paul
authors: P
authors: Roschger
authors: Teun J
authors: TJ
authors: de Vries
authors: Hideki
authors: H
authors: Chiba
authors: Klaus
authors: K
authors: Klaushofer
authors: Veit
authors: V
authors: Flockerzi
authors: René J M
authors: RJ
authors: Bindels
authors: Marc
authors: M
authors: Freichel
authors: Johannes P T M
authors: JP
authors: van Leeuwen
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000166:cytology* / Q000378:metabolism*; D002113:Calcification, Physiologic / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism*; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000378:metabolism; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: C506952:ATP2B1 protein, human; D015220:Calcium Channels; C556012:Pmca1b protein, mouse; D050916:TRPV Cation Channels; C422827:TRPV6 protein, human; C446923:Trpv6 protein, mouse; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium