Vitamin D acts through a nuclear receptor known as the vitamin D receptor (VDR), which is primarily located in the cell nucleus. When vitamin D is metabolized in the body to its active form, calcitriol (1,25-dihydroxyvitamin D), it binds to the VDR. This vitamin D-VDR complex then acts as a transcription factor, regulating the expression of various genes involved in calcium and phosphorus metabolism, bone health, immune function, and other physiological processes.
The binding of calcitriol to the VDR in the nucleus initiates a cascade of molecular events that ultimately affect gene expression. This regulation of gene transcription by the vitamin D-VDR complex plays a critical role in mediating the biological effects of vitamin D throughout the body.
So, in summary, vitamin D exerts its effects through a nuclear receptor, the vitamin D receptor (VDR), which is located in the cell nucleus.