The progesterone receptor (PR) can also be found in two forms, but these are derived from a single gene. PRA has had 164 amino acids truncated from the N-terminus of PRB, providing a receptor that has different interactions with target genes and associated proteins. PRB mainly mediates the stimulatory actions of progesterone. PRA acts as a transcriptional inhibitor of ER, androgen receptor (AR), glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and PRB.12 These differential actions are believed to be a result of interactions with different coactivators and corepressors. The DNA- and ligand-binding domains for the two receptors are identical.
ANDROGEN, GLUCOCORTICOID, AND MINERALOCORTICOID RECEPTORS
The AR, GR, and MR are present in only a single form. Only one gene and one protein are known for each receptor. Mutant forms of AR16 and GR17 are known, and evidence is mounting that some of these mutant receptors are associated with disease states.
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