Abstract
The extracellular matrix protein nephronectin (Npnt), also called POEM, is considered to play critical roles as an adhesion molecule in development and functions of various tissues, such as the kidneys, liver, and bone. In the present study, we examined the molecular mechanism of Npnt gene expression and found that vitamin D3 (1α,25‐dihydroxyvitamin D3,VD 3) strongly enhanced Npnt mRNA expression in MC3T3‐E1 cells from a mouse osteoblastic cell line. The VD 3‐induced increase in Npnt expression is both time‐ and dose‐dependent and is mediated by the vitamin D receptor (VDR).
Highlights
Nephronectin (Npnt), an extracellular matrix protein, is known to be involved in the development and functions of various tissues [1,2]. This protein, which acts as an adhesion molecule, consists of five epidermal growth factor (EGF)-like domains, an Arg-Gly-Asp (RGD) cell binding motif, and a meprin A5 protein
VD3 regulates the expression of receptor activator of nuclear factor-jb ligand (RANKL), which stimulates bone resorption through osteoclast activation [7]
The biological functions of VD3 are mediated by its binding to the vitamin D receptor (VDR), a nuclear transcription factor that forms a heterodimer with the retinoid X receptor (RXR) and binds to vitamin D responsible elements (VDRE) in regulatory regions that are functionally linked to specific target genes [8,9]
Summary
We initially examined regulation of the expression of Npnt by VD3, as well as by its agonistic analogs EB1089 and calcipotriol, in MC3T3-E1 cells. Treatment with 100 ngÁmLÀ1 of each those reagents for 24 h sharply increased the expression of Npnt mRNA (Fig. 1). In the above described experiments, MC3T3-E1 cells were treated with different concentrations of VD3 for 24 h and we observed a significant increase in Npnt mRNA expression, when the VD3 concentration was greater than 10 ngÁmLÀ1 when compared to the unstimulated control (Fig. 2A). When the cells were treated for at least 12 h, a significant increase in Npnt mRNA expression was seen and occurred in a time-dependent manner, which increased more than up to 15-fold after 24 h (Fig. 2B). On the basis of our results, we propose a model of increased Npnt mRNA expression induced by VD3 through the VDR (Fig. 4). Our results show that VD3 stimulates Npnt gene expression in both time- and dose-dependent manners via the VDR
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