A novel spliced variant of the type 1 corticotropin-releasing hormone receptor with a deletion in the seventh transmembrane domain present in the human pregnant term myometrium and fetal membranes

Mol Endocrinol. 1999 Dec;13(12):2189-202. doi: 10.1210/mend.13.12.0391.

Abstract

CRH exerts its actions via activation of specific G protein-coupled receptors, which exist in two types, CRH-R1 and CRH-R2, and arise from different genes with multiple spliced variants. RT-PCR amplification of CRH receptor sequences from human myometrium and fetal membranes yielded cDNAs that encode a novel CRH-R type 1 spliced variant. This variant (CRH-R1d) is present in the human pregnant myometrium at term only, which suggests a physiologically important role at the end of human pregnancy and labor. The amino acid sequence of CRH-R1d is identical to the CRH-R1alpha receptor except that it contains an exon deletion resulting in the absence of 14 amino acids in the predicted seventh transmembrane domain. Binding studies in HEK-293 cells stably expressing the CRH-R1d or CRH-R1alpha receptors revealed that the deletion does not change the binding characteristics of the variant receptor. In contrast, studies on the G protein activation demonstrated that CRH-R1d is not well coupled to the four subtypes of G proteins (G(s), G(i), G(o), G(q)) that CRH-R1alpha can activate. These data suggest that although the deleted segment is not important for CRH binding, it plays a crucial role in CRH receptor signal transduction. Second messenger studies of the variant receptor showed that CRH and CRH-like peptides can stimulate the adenylate cyclase system, with reduced sensitivity and potency by 10-fold compared with the CRH-R1alpha. Furthermore, CRH failed to stimulate inositol trisphosphate production. Coexpression studies between the CRH-R1d or CRH-R1alpha showed that this receptor does not play a role as a dominant negative receptor for CRH.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing*
  • Amino Acid Sequence
  • Base Sequence
  • Cell Line
  • Cell Membrane / chemistry
  • Corticotropin-Releasing Hormone / pharmacology
  • Extraembryonic Membranes / chemistry*
  • Female
  • Gene Deletion*
  • Humans
  • Immunosorbent Techniques
  • Kidney
  • Molecular Sequence Data
  • Myometrium / chemistry*
  • Pregnancy
  • RNA, Messenger / metabolism
  • Receptors, Corticotropin-Releasing Hormone / analysis
  • Receptors, Corticotropin-Releasing Hormone / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transfection

Substances

  • RNA, Messenger
  • Receptors, Corticotropin-Releasing Hormone
  • Corticotropin-Releasing Hormone