Expression and signalling characteristics of the corticotrophin-releasing hormone receptors during the implantation phase in the human endometrium

Abstract

Corticotrophin-releasing hormone (CRH) has been identified in several peripheral tissues, including the female reproductive organs. CRH is expressed in the placenta, myometrium, epithelial endometrium and the endometrial stromal cells at all phases of the menstrual cycle. Similarly, CRH receptors are present in pregnant and non-pregnant myometrium, placenta and endometrium. Putative roles of CRH in the endometrium include involvement in implantation, decidualisation and maintenance of pregnancy. In this study we sought to investigate in detail the CRH receptor repertoire expressed in the human endometrium and their signalling characteristics. Using RT-PCR we were able to demonstrate the expression of CRH receptor 1 (CRH-R1 ) and CRH-R2 in the human endometrium. CRH-R1 was present in 40% of endometrial cDNAs examined. No apparent expression of CRH-R2 , CRH-R2 or any other CRH-R1 splice variants was detected. Chemical cross-linking studies with 125 I-ovine CRH revealed that the endometrial CRH receptor has a molecular weight of 45 kDa. Using the non-hydrolysable photoreactive analogue [ -32 P]GTP-azidoanilide and peptide antisera raised against G-protein -subunits, we then studied coupling of endometrial CRH receptors to G proteins. Treatment of endometrial membranes with human CRH (100 nM) increased the labelling of Gq and Gs, but not Gi or Go. These results were supported by experiments in epithelial cells of the non-pregnant human endometrium in the secretory phase which showed that CRH induced increases in both cAMP and inositol trisphosphate levels. These results suggested that CRH may exert multiple effects in the human endometrium via distinct signalling cascades. These events are possibly mediated via different receptor subtypes.

Expression and subcellular localization of CRH and its receptors in human endometrial cancer

“…Similar to previous findings by other groups (Di Blasio et al, 1997, Karteris et al, 2004, we found that CRH-R1 is expressed in the cytoplasm of normal epithelial endometrial cells. Most importantly, CRH-R1 expression was found in a higher percentage of tumors expressing progesterone receptors, indicating that CRH-R1 expression is associated to a more differentiated and less aggressive phenotype.…”

“…Thus, it was interesting to investigate the expression and localization of such receptor subtype in our paradigm. Human endometrial cells were shown to express CRH-R2 under physiological conditions (Karteris et al, 2004); in the present study, we could confirm CRH-R2 expression in normal endometrial tissues surrounding the tumor; moreover, we observed an unprecedented nuclear localization, whose functional meaning remains to be established. Conversely, the expression of CRH-R2 in the tumor cell cytoplasm has been more frequently observed in stage II-IV compared to stage I tumors, thus suggesting that high CRH-R2 might identify poor prognosis tumors.…”

Differential Responses of Corticotropin-Releasing Hormone Receptor Type 1 Variants to Protein Kinase C Phosphorylation

“…The human-specific CRH-R1␤ receptor variant, which is identical to the CRH-R1␣ except for a 29-amino acid insert in the first intracellular loop, interacts with CRH and G s with significantly reduced agonist affinity compared with CRH-R1␣ (Xiong et al, 1995). Like many other splice variants, the CRH-R1␤ mRNA expression exhibits tissue-specific characteristics and has been identified in anterior pituitary, myometrial smooth muscle cells, and endometrium and human umbilical cord blood mast cells (Chen et al, 1993;Grammatopoulos et al, 1998;Slominski et al, 2001;Karteris et al, 2004;Cao et al, 2005) but not in the placenta, adrenal, and synovium (Karteris et al, , 2001McEvoy et al, 2001). The function(s) of CRH-R1␤ and the potential CRH-R1-derived receptor variants is currently unknown.…”

Urocortin expression is downregulated in human endometrial carcinoma

“…In addition, the human endometrium also expresses both CRF-R1 (Di Blasio et al 1997) and CRF-R2 (Karteris et al 2004), and in in vitro experimental models, the activation of the cAMP pathway induced by the binding to CRF-R1 located on endometrial stromal cells demonstrated differentiating activity, since those cells undergo decidualization (Ferrari et al 1995). Furthermore, the activation of CRF-R1 receptor subtype, which is expressed under basal conditions by a tumor cell line derived from the human endometrium, namely adenocarcinoma Ishikawa cells, inhibits tumor cell growth, and proliferation in a dose-and time-dependent manner (Graziani et al 2002).…”