G alpha 11 and G alpha q guanine nucleotide regulatory proteins differentially modulate the response to thyrotropin-releasing hormone in Xenopus oocytes.

Xenopus oocytes that express mouse thyrotropin-releasing hormone receptors (TRH-Rs) after injection if RNA transcribed from TRH-R cDNA respond to THR by a depolarizing current. This response is transduced by activation of phosphoinositide-specific phospholipase C and utilizes an as yet unidentified endogenous guanine nucleotide-binding regulatory (G) protein(s). The alpha subunit of G11 and Gq have recently been shown to couple receptors to activation of phospholipase C. To determine whether there are functional differences between these proteins, we have co-expressed the TRH-R with either alpha 11 or alpha q. alpha 11 potentiated the response to TRH (by 61 +/- 16%), while alpha q inhibited the response (by 37 +/- 9%). The changes in amplitudes were accompanied by inverse changes in response latencies. These data show that alpha 11 and alpha q differentially modulate signal transduction in Xenopus oocytes.