Steroids and intracellular receptors
Steroid hormones are lipids and so can enter the cell by simple diffusion across the plasma membrane. The receptors for this hormone exist either in the cytoplasm or nucleus, which is where the hormone binds to them. When the hormone binds to the receptor, a series of events occurs:
- The receptor is activated due to a conformational changes in the receptor induced by the binding hormone. This activation leads to the receptor being able to bind to DNA.
- Activated receptors bind to the DNA binding domain, which are short specific sequences of DNA which are located in promoters of hormone-responsive genes.
- Transcription from those genes to which the receptor is bound is affected. Most commonly, receptor binding stimulates transcription.
The hormone-receptor complex at the ligand binding domain thus behaves as a transcription factor. Due to steroid hormone's ability to diffuse freely through the lipid bilayer due to being hydrophobic they can have a long lasting effect on a target cell and their signal and remain active from hours - days .
- ↑ 1998, Hormones with Intracellular Receptors, http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/moaction/intracell.html, 22.11.12