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.
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.
Mesh Terms:
Alternative Splicing, Amino Acid Sequence, Base Sequence, Cell Line, Cell Membrane, Corticotropin-Releasing Hormone, Extraembryonic Membranes, Female, Gene Deletion, Humans, Immunosorbent Techniques, Kidney, Molecular Sequence Data, Myometrium, Pregnancy, RNA, Messenger, Receptors, Corticotropin-Releasing Hormone, Reverse Transcriptase Polymerase Chain Reaction, Transfection
Alternative Splicing, Amino Acid Sequence, Base Sequence, Cell Line, Cell Membrane, Corticotropin-Releasing Hormone, Extraembryonic Membranes, Female, Gene Deletion, Humans, Immunosorbent Techniques, Kidney, Molecular Sequence Data, Myometrium, Pregnancy, RNA, Messenger, Receptors, Corticotropin-Releasing Hormone, Reverse Transcriptase Polymerase Chain Reaction, Transfection
Mol. Endocrinol.
Date: Dec. 01, 1999
PubMed ID: 10598591
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