Molecular and functional characterization of GnRH receptors cloned from rat pituitary and a mouse pituitary tumor cell line.

A cDNA for a GnRH receptor (mtGnRH-R) was obtained from a mouse gonadotropic pituitary cell line (alpha T3-1) by expression cloning. This full-length cDNA was subsequently used as a probe to clone a rat pituitary GnRH receptor (rGnRH-R). The two receptors differ by 13 amino acids and are 100% identical to those recently reported. The analysis of the cloned receptors by photoaffinity-labeling followed by SDS-PAGE reveals a major band of approximately 70 kDa. This is in contrast to the native rat pituitary and mouse alpha T3-1 receptors whose major labeled species migrate with an apparent size of approximately 45 kDa. Functional studies reveal that both receptors, when transiently expressed in COSM6 cells, can bind GnRH with high affinity and transduce the stimulation of IP3 accumulation in response to GnRH.