UNSPECIFIED. (2004) Protein kinase A-induced negative regulation of the corticotropin-releasing hormone R1 alpha receptor-extracellularly regulated kinase signal transduction pathway: The critical role of Ser(301) for signaling switch and selectivity. MOLECULAR ENDOCRINOLOGY, 18 (3). pp. 624-639. ISSN 0888-8809

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Abstract

Activation of CRH receptors type 1 (CRH-R1) by CRH or urocortin (UCN) leads to stimulation of multiple G proteins with consequent effects on diverse signaling cascades in a tissue-specific manner. In human myometrium and human embryonic kidney (HEK) 293 cells, binding of UCN to CRH-R1alpha receptors activates both the Gs and Gq, leading to activation of the adenylyl cyclase/protein kinase A (PKA) and the phospholipase C/protein kinase C and ERK1/2 signaling pathways, respectively. The overall result of these signals is often unpredictable, as these two signaling pathways can interact in many cellular systems, with either potentiation or inhibition of ERK1/2 activity. In the present studies we investigated potential signaling interactions after stimulation of CRH-R1alpha receptors in human cultured pregnant myometrial cells or HEK293 cells overexpressing recombinant CRH-R1alpha receptors. We found that the adenylyl cyclase/PKA pathway has the capacity to markedly decrease UCN-induced ERK1/2 activation, and that these effects were due in part to the ability of PKA to phosphorylate the CRH-R1alpha at position Ser(301) in the third intracellular loop. Mutant CRH-R1alpha receptors with substitutions at position Ser301, which is the only potential PKA phosphorylation site, were resistant to PKA-dependent phosphorylation and showed altered signaling characteristics, which were dependent upon the amino acid substitution at this position. We conclude that Ser301, which is located in the third intracellular loop of CRH-R1alpha, is critical for efficient coupling of the receptor to G proteins and to second messenger generation. Phosphorylation by PKA prevents maximal coupling of the CRH-R1alpha to Gq-protein, and thereby reduces activation of ERK 1/2.

Item Type:	Journal Article
Subjects:	R Medicine > RC Internal medicine
Journal or Publication Title:	MOLECULAR ENDOCRINOLOGY
Publisher:	ENDOCRINE SOC
ISSN:	0888-8809
Date:	1 March 2004
Volume:	18
Number:	3
Number of Pages:	16
Page Range:	pp. 624-639
Identification Number:	10.1210/me.2003-0365
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/8680

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