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.
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.
Karteris
Emmanouil
E
Laboratory of GPCR Pathophysiology Research, Endocrinology and Metabolism, Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom.
Markovic
Danijela
D
Chen
Jing
J
Hillhouse
Edward W
EW
Grammatopoulos
Dimitris K
DK
D002478:Cells, Cultured; D003001:Cloning, Molecular; D004958:Estradiol / Q000494:pharmacology*; D005091:Exons / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007743:Labor, Obstetric / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D009215:Myometrium / Q000737:chemistry / Q000378:metabolism*; D011247:Pregnancy / Q000235:genetics* / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology*; D020033:Protein Isoforms / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D018019:Receptors, Corticotropin-Releasing Hormone / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection; D000099052:CRF Receptor, Type 1
D020033:Protein Isoforms; D018019:Receptors, Corticotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; D000099052:CRF Receptor, Type 1