Membrane Actions of Vitamin D Metabolites 1α,25(OH)2D 3 and 24R,25(OH)2D3 Are Retained in Growth Plate Cartilage Cells from Vitamin D Receptor Knockout Mice

Barbara D. Boyan, V. L. Sylvia, N. McKinney, Z. Schwartz

Research output: Contribution to journalArticle

65 Scopus citations

Abstract

1α,25(OH)2D3 regulates rat growth plate chondrocytes via nuclear vitamin D receptor (1,25-nVDR) and membrane VDR (1,25-mVDR) mechanisms. To assess the relationship between the receptors, we examined the membrane response to 1α,25(OH)2D3 in costochondral cartilage cells from wild type VDR(+/+) and VDR(-/-) mice, the latter lacking the 1,25-nVDR and exhibiting type II rickets and alopecia. Methods were developed for isolation and culture of cells from the resting zone (RC) and growth zone (GC, prehypertrophic and upper hypertrophic zones) of the costochondral cartilages from wild type and homozygous knockout mice. 1α,25(OH)2D3 had no effect on [ 3H]-thymidine incorporation in VDR(-/-) GC cells, but it increased [3H]-thymidine incorporation in VDR(+/+) cells. Proteoglycan production was increased in cultures of both VDR(-/-) and VDR(+/+) cells, based on [35S]-sulfate incorporation. These effects were partially blocked by chelerythrine, which is a specific inhibitor of protein kinase C (PKC), indicating that PKC-signaling was involved. 1α,25(OH)2D 3 caused a 10-fold increase in PKC specific activity in VDR(-/-), and VDR(+/+) GC cells as early as 1 min, supporting this hypothesis. In contrast, 1α,25(OH)2D3 had no effect on PKC activity in RC cells isolated from VDR(-/-) or VDR(+/+) mice and neither 1β,25(OH)2D3 nor 24R,25(OH)2D3 affected PKC in GC cells from these mice. Phospholipase C (PLC) activity was also increased within 1 min in GC chondrocyte cultures treated with 1α,25(OH)2D3. As noted previously for rat growth plate chondrocytes, 1α,25(OH)2D3 mediated its increases in PKC and PLC activities in the VDR(-/-) GC cells through activation of phospholipase A2 (PLA2). These responses to 1α,25(OH)2D3 were blocked by antibodies to 1,25-MARRS, which is a [3H]-1,25(OH)2D3 binding protein identified in chick enterocytes. 24R,25(OH)2D 3 regulated PKC in VDR(-/-) and VDR(+/+) RC cells. Wild type RC cells responded to 24R,25(OH)2D3 with an increase in PKC, whereas treatment of RC cells from mice lacking a functional 1,25-nVDR caused a time-dependent decrease in PKC between 6 and 9 min. 24R,25(OH)2D 3 dependent PKC was mediated by phospholipase D, but not by PLC, as noted previously for rat RC cells treated with 24R,25(OH)2D 3. These results provide definitive evidence that there are two distinct receptors to 1α,25(OH)2D3. 1α,25(OH)2D3-dependent regulation of DNA synthesis in GC cells requires the 1,25-nVDR, although other physiological responses to the vitamin D metabolite, such as proteoglycan sulfation, involve regulation via the 1,25-mVDR.

Original languageEnglish (US)
Pages (from-to)1207-1223
Number of pages17
JournalJournal of Cellular Biochemistry
Volume90
Issue number6
DOIs
StatePublished - Dec 15 2003

Keywords

  • 1α,25(OH)D
  • 24R,25(OH)D
  • Growth plate chondrocytes
  • Membrane receptors
  • Rapid actions of steroid hormones
  • VDR knockout mice
  • Vitamin D metabolites

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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