Vitamin D receptor is not required for the rapid actions of 1,25-dihydroxyvitamin D3 to increase intracellular calcium and activate protein kinase C in mouse osteoblasts
✍ Scribed by Ramesh K. Wali; Juan Kong; Michael D. Sitrin; Marc Bissonnette; Yan Chun Li
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 190 KB
- Volume
- 88
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Abstract
The rapid, non‐genomic actions of 1,25‐dihydroxyvitamin D~3~ [1,25(OH)~2~D~3~] have been well described, however, the role of the nuclear vitamin D receptor (VDR) in this pathway remains unclear. To address this question, we used VDR(+/+) and VDR(−/−) osteoblasts isolated from wild‐type and VDR null mice to study the increase in intracellular calcium ([Ca^2+^]~i~) and activation of protein kinase C (PKC) induced by 1,25(OH)~2~D~3~. Within 1 min of 1,25(OH)~2~D~3~ (100 nM) treatment, an increase of 58 and 53 nM in [Ca^2+^]~i~ (n = 3) was detected in VDR(+/+) and VDR(−/−) cells, respectively. By 5 min, 1,25(OH)~2~D~3~ caused a 2.1‐ and 1.9‐fold increase (n = 6) in the phosphorylation of PKC substrate peptide acetylated‐MBP~4–14~ in VDR(+/+) and VDR(−/−) osteoblasts. The 1,25(OH)~2~D~3~‐induced phosphorylation was abolished by GF109203X, a general PKC inhibitor, in both cell types, confirming that the secosteroid induced PKC activity. Moreover, 1,25(OH)~2~D~3~ treatment resulted in the same degree of translocation of PKC‐α and PKC‐δ, but not of PKC‐ζ, from cytosol to plasma membrane in both VDR(+/+) and VDR(−/−) cells. These experiments demonstrate that the 1,25(OH)~2~D~3~‐induced rapid increases in [Ca^2+^]~i~ and PKC activity are neither mediated by, nor dependent upon, a functional nuclear VDR in mouse osteoblasts. Thus, VDR is not essential for these rapid actions of 1,25(OH)~2~D~3~ in osteoblasts. © 2003 Wiley‐Liss, Inc.