A novel class of GABAA receptor subunit in tissues of the reproductive system.

A novel subunit of the gamma-aminobutyrate, type A (GABAA) receptor family has been identified in human and rat tissues. The subunit displays 30-40% amino acid identity with known family members and represents a distinct subunit class (termed pi). Transcripts of the pi subunit were detected in several human tissues and were particularly abundant in the uterus. The pi subunit protein can assemble with known GABAA receptor subunits and confer unique ligand binding properties to the recombinant receptors in which it combines. Most notably, the presence of the pi subunit alters the sensitivity of recombinant receptors to the endogenous steroid, pregnanolone. Identification of the pi subunit indicates a new target for pharmacological manipulation of GABAA receptors that are located outside of the central nervous system.