Vitamin D and Intracellular Actions

by Kevin Ahern, PhD

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    Now, vitamin D is unusual in another respect. Vitamin D acts like a hormone as I said and it is in fact a steroid hormone as some people categorize it. However, steroid hormones move across cellular membranes at will. They don’t have to be transported. Vitamin D, however, has a receptor protein on the cell surface that binds to it and brings it into the cell. This is unusual for a steroid hormone. Vitamin D bound to the vitamin D receptor then interacts with a protein inside the cell known as the vitamin D receptor or the VDR. The VDR is similar to the steroid hormone receptors, but in the case of the VDR, the vitamin D is actually brought to it by the vitamin D binding protein on the surface of the cell. Vitamin D-VDR complex then goes into the nucleus and binds to hormone response elements or HREs as they're called in DNA. The effect of this vitamin D-VDR complex binding to these elements causes genes associated with those elements to be expressed and made. So what we can see as happening here is vitamin D is actually affecting gene expression inside of a cell as a result of movement into the cell and ultimately into the nucleus. Vitamin D, of course, control the transcription of specific genes and it does with the process that I have just described to you. What are these genes? Well, the genes are involved in mineral metabolism as we have seen. And they’re also involved in immune functions that help provide for a strong and healthy immune system. This is a different function of vitamin D than what I’ve talked about up to this point. Vitamin D can also interfere with receptor tyrosine kinase signaling. As I’ve talked about in another lecture,...

    About the Lecture

    The lecture Vitamin D and Intracellular Actions by Kevin Ahern, PhD is from the course Vitamins. It contains the following chapters:

    • Vitamin D - Intracellular Actions
    • Calcium Inside the Cell
    • Calcium and Metabolism

    Included Quiz Questions

    1. It interacts with steroid hormone receptors to stimulate transcription.
    2. It favors angiogenesis.
    3. It stimulates receptor tyrosine kinase signaling.
    4. All of the answers are true.
    5. None of the answers are true.
    1. It binds to many proteins as a second messenger.
    2. It is carried by proteins with FG hand structures.
    3. All of the answers are true.
    4. It is soluble with DNA.
    5. None of the answers are true.
    1. It stimulates muscular contraction.
    2. It stimulates glycogen synthesis.
    3. It causes the closing of endoplasmic reticulum channels when bound to calmodulin.
    4. All of the answers are true.
    5. None of the answers are true.

    Author of lecture Vitamin D and Intracellular Actions

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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