Steroid hormone receptor

Steroid hormone receptors are generally intracellular (specifically cytoplasmatic) receptors that perform signal transduction for steroid hormones. After binding to the ligand, steroid receptors often form dimers, enter the nucleus and act as transcription factors, augmenting or suppressing transcription of particular genes.

Steroid hormone receptors are found in homodimer forms. They have two Zn-finger domains, one of which binds DNS, the other one connects the molecule to its pair in the homodimer. They also contain a site for ligand binding and a nuclear localization signal.

Such receptors are closely related to chaperones (namely hsp90 and hsp56 ), which are required to maintain their inactive (but receptive) cytoplasmatic conformation.

The hormone response elements of steroid hormone receptors have the structure of a pair of palindrome sequences separated by three nucleotides.

There is some evidence that certain steroid hormone receptors can extend through lipid bilayer membranes at the surface of cells and might be able to interact with hormones that remain outside of cells (Luconi et al 2004).

Steroid hormone receptors can also function outside of the nucleus and couple to cytoplasmic signal transduction proteins such as PI3k and Akt kinase (Aquila et al 2004).

Types:

• Sex hormone receptors (sex hormones)
• Vitamin D receptor (vitamin D)
• Glucocorticoid receptor (glucocorticoids)
• Mineralocorticoid receptor (mineralocorticoids)

References

• Aquila S, Sisci D, Gentile M, Middea E, Catalano S, Carpino A, Rago V, Ando S. Estrogen receptor (ER)alpha and ER beta are both expressed in human ejaculated spermatozoa: evidence of their direct interaction with phosphatidylinositol-3-OH kinase/Akt pathway. J Clin Endocrinol Metab 2004;89:1443-51. PMID 15001646.
• Luconi M, Francavilla F, Porazzi I, Macerola B, Forti G, Baldi E. Human spermatozoa as a model for studying membrane receptors mediating rapid nongenomic effects of progesterone and estrogens. Steroids 2004;69:553-9. PMID 15288769.