A Novel Class of GABAA Receptor Subunit in Tissues of the Reproductive System*

A novel subunit of the γ-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 π). Transcripts of the π subunit were detected in several human tissues and were particularly abundant in the uterus. The π 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 π subunit alters the sensitivity of recombinant receptors to the endogenous steroid, pregnanolone. Identification of the π subunit indicates a new target for pharmacological manipulation of GABAA receptors that are located outside of the central nervous system.