PT - JOURNAL ARTICLE AU - Deborah Lee AU - Anna Robeva AU - Zhongjian Chen AU - Kenneth P. Minneman TI - Mutational Uncoupling of α<sub>1A</sub>-Adrenergic Receptors from G Proteins Also Uncouples Mitogenic and Transcriptional Responses in PC12 Cells AID - 10.1124/jpet.103.050500 DP - 2003 Aug 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 471--477 VI - 306 IP - 2 4099 - http://jpet.aspetjournals.org/content/306/2/471.short 4100 - http://jpet.aspetjournals.org/content/306/2/471.full SO - J Pharmacol Exp Ther2003 Aug 01; 306 AB - Activation of human α1A-adrenergic receptors in PC12 cells causes many second messenger, mitogenic, and transcriptional responses. We examined the role of G protein activation in these responses by uncoupling the receptor through deletion of the first three amino acids from the third intracellular loop (Δ208–210). Expression levels of retrovirus-transfected wild-type and Δ208–210 α1A-adrenergic receptors in PC12 cells were similar and showed identical binding affinities for antagonists. However, the potency of the agonist norepinephrine was increased 9-fold by the Δ208–210 mutation. In PC12 cells expressing the Δ208–210 construct, calcium and inositol phosphate responses to norepinephrine were essentially abolished. The strong activation of mitogen-activated protein kinase pathways seen upon stimulation of wild-type α1A-adrenergic receptors in PC12 cells was abolished by the Δ208–210 mutation, as was activation of the tyrosine kinase Pyk2. Norepinephrine also activates several transcriptional reporters through α1A-adrenergic receptors in PC12 cells, including reporters for activator protein 1, serum response element, cAMP response element, nuclear factor-κB, nuclear factor of activated T cells, γ-interferon-activated sequence, and signal transducer and activator of transcription. All these transcriptional responses were abolished by the Δ208–210 mutation. Overexpression of Gα16 did not rescue any of these responses. These data suggest that known second messenger, mitogenic, and transcriptional effects of α1A-adrenergic receptors in PC12 cells all require G protein activation. The American Society for Pharmacology and Experimental Therapeutics