1 Do all metabotropic receptors bind Gproteins 2 What is a m

1. Do all metabotropic receptors bind G-proteins?

2. What is a metabotropic receptor?

3.Why are steroid and thyroid hormone receptors called hormone dependent transcription factors?

4.In which compartment (cytoplasm vs. nucleus) does transcription and translation take place?

5.What activates a steroid receptor?

6.What are 3 things that glucocorticoid receptors are able to do after activation that they couldn’t do before activation?

Solution

1. Yes. All G - protein coupled receptors are considered as metanotropic receptors because these receptors are activated and indirectly linked with ion channels on the plasma membrane of the cell through signal transduction mechanisms.

2. A metabotropic receptor is membrane bound receptor found in eukaryotic cells and is activated through a seconadary messenger.

3. Since, the receptors for steroid and thyroid hormones are located inside target cells, in the cytoplasm or nucleus, and function as ligand-dependent transcription factors. The hormone-receptor complex binds to promoter regions of corresponding genes that stimulate or sometimes inhibit transcription of the genes as per the cellular requirement.

4. Transcription or synthesis of messenger RNA (mRNA) from DNA occurs in the nucleus and the translation or protein synthesis occurs in cytoplasm.

5. Steroid receptor belongs nuclear receptor family. It remains in nucleus or moves to cytoplasm as and when the steroid hormones binds to it and activates it. Thus, steroid receptor activated by the binding of steroid hormone.

6. The glucocorticoid receptor (GR, or GCR) is the receptor to which cortisol and other glucocorticoids bind.The GR is expressed in all cell of the body and is involved in regulatation of genes that control the development, metabolism, and immune response. The glucocorticoid receptor gene is expressed in several forms, and exhibits different (pleiotropic) effects in different parts of the body. When the glucocorticoid receptor binds to glucocorticoids, it activates the regulation of gene transcription. The receptor resides in the cytosol of the cell prior its binding to glucocorticoids. After the receptor is bound to glucocorticoid, the receptor-glucorticoid complex choose to act in either of two paths by regulating the expression of anti-inflammatory proteins in the nucleus through the activated GR complex or represses the expression of pro-inflammatory proteins in the cytosol. This can occur by preventing the translocation of other transcription factors from the cytosol into the nucleus.