NRIP (Nuclear receptor interaction protein), also known as IQWD1 ( IQ motif and WD repeat-containing protein 1), MSTP055, ARCAP or PC326, is an 860 amino acid protein that localizes to the nucleus and contains one IQ domain and seven WD-repeats. Expressed in testis, skeletal muscle, prostate and heart, NRIP functions as a ligand-dependent coactivator of nuclear receptors and specifically enhances the transcriptional activity of AR (androgen receptor) and GR (glucocorticoid receptor). NRIP exists as three isoforms that are produced by alternative splicing events.