Mutational uncoupling of alpha(1A)-adrenergic receptors from G proteins also uncouples mitogenic and transcriptional responses in PC12 cells

作者：Lee D; Robeva A; Chen ZJ; Minneman KP^*

来源：Journal of Pharmacology and Experimental Therapeutics, 2003, 306(2): 471-477.

DOI：10.1124/jpet.103.050500

Activation of human alpha(1A)-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 (Delta(208-210)). Expression levels of retrovirus-transfected wild-type and Delta(208-210) alpha(1A)-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 Delta(208-210) mutation. In PC12 cells expressing the Delta(208-210) 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 alpha(1A-)adrenergic receptors in PC12 cells was abolished by the Delta(208-210) mutation, as was activation of the tyrosine kinase Pyk2. Norepinephrine also activates several transcriptional reporters through alpha(1A)-adrenergic receptors in PC12 cells, including reporters for activator protein 1, serum response element, cAMP response element, nuclear factor-kappaB, nuclear factor of activated T cells, gamma-interferon-activated sequence, and signal transducer and activator of transcription. All these transcriptional responses were abolished by the Delta(208-210) mutation. Overexpression of Galpha16 did not rescue any of these responses. These data suggest that known second messenger, mitogenic, and transcriptional effects of alpha(1A)-adrenergic receptors in PC12 cells all require G protein activation.

• 出版日期2003-8