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Endocrinology. 2010 Oct;151(10):4959-68. doi: 10.1210/en.2010-0622. Epub 2010 Aug 11.

Identification of a novel corticotropin-releasing hormone type 1beta-like receptor variant lacking Exon 13 in human pregnant myometrium regulated by estradiol-17beta and progesterone.

Author information

1
Laboratory of GPCR Pathophysiology Research, Endocrinology and Metabolism, Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom.

Abstract

Two types of CRH receptors mediate the diverse biological functions of CRH and CRH-related peptides. The type 1 CRH-R (CRH-R1) is extensively targeted by pre-mRNA splicing mechanisms that give rise to multiple mRNA splice variants. RT-PCR amplification of CRH-R1 sequences from human myometrium yielded cDNAs that encode a novel CRH-R1 splice variant with structural characteristics identical with CRH-R1β except a 14-amino acid deletion in the seventh transmembrane domain characteristic of the CRH-R1d. Transient expression of the hybrid CRH-R1 variant (CRH-R1β/d) in human embryonic kidney 293 cells revealed primarily intracellular expression, although some plasma membrane protein expression was also detectable. CRH bound to CRH-R1β/d with affinity comparable with the CRH-R1β; however, it was unable to stimulate adenylyl cyclase or other second messengers. Using a semiquantitative RT-PCR assay, CRH-R1β/d mRNA transcript was detected in human pregnant, but not nonpregnant, myometrium as early as 31 wk of gestation. Furthermore, in human pregnant myometrial cells, the relative expression of CRH-R1β and CRH-R1β/d mRNA appeared to be regulated by steroids; CRH-R1β/d mRNA expression was increased by estradiol-17β, whereas CRH-R1β mRNA levels were increased by progesterone. Progesterone also substantially increased CRH-R1α mRNA levels and cellular responsiveness to CRH as determined by increased agonist binding and cAMP production as well as resistance to CRH-R heterologous desensitization by phorbol esters. These results provide novel evidence for distinct patterns of CRH-R1 splicing and identify specific steroid-mediated regulation of CRH-R1 variant expression, which might be important for modulating CRH actions during human pregnancy and labour.

PMID:
20702571
DOI:
10.1210/en.2010-0622
[Indexed for MEDLINE]

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