Gα11 and Gαq guaninine nucleotide regulatory proteins differentially modulate the response to thyrotropin‐releasing hormone in Xenopus oocytes

Abstract

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 transducer by activation of phosphoinositide‐specific phospholipase C and utilizes an as yet unidentified endogenous guanine nucleotide‐binding regulatory (G) protein(s). The α subunit of G₁₁ and G_q 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 α₁₁ or α_q, α₁₁ potentiated the response to TRH (by 61±16%), while α_q inhibited the response (by 37±9%). The changes in amplitudes were accompanied by inverse changes in response latencies. These data show that α₁₁ and α_q differentially modulate signal transduction in Xenopus oocytes.