Signal Transduction Characteristics of the Corticotropin-Releasing Hormone Receptors in the Feto-Placental Unit

• Published in: The journal of clinical endocrinology and metabolism 2000-05, Vol.85 (5), p.1989-1996
• Main Authors: Karteris, E., Grammatopoulos, D., Randeva, H., Hillhouse, E. W.
• Format: Article
• Language: English
• Subjects: Adenylate Cyclase Toxin; Adenylyl Cyclases - metabolism; Amino Acid Sequence; Binding Sites; Biological and medical sciences; Colforsin - pharmacology; Corticotropin-Releasing Hormone - pharmacology; Cyclic AMP - metabolism; Extraembryonic Membranes - drug effects; Extraembryonic Membranes - physiology; Female; Fundamental and applied biological sciences. Psychology; GTP-Binding Proteins - chemistry; GTP-Binding Proteins - metabolism; Guanosine 5'-O-(3-Thiotriphosphate) - pharmacology; Guanosine Triphosphate - pharmacology; Guanylyl Imidodiphosphate - pharmacology; Hormone metabolism and regulation; Humans; Inositol Phosphates - metabolism; Molecular Sequence Data; Placenta - drug effects; Placenta - physiology; Pregnancy; Pregnancy. Parturition. Lactation; Receptors, Corticotropin-Releasing Hormone - physiology; Signal Transduction - drug effects; Signal Transduction - physiology; Vertebrates: reproduction; Virulence Factors, Bordetella - pharmacology
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jcem.85.5.6590

Placentally derived CRH plays a major role in the mechanisms controlling human pregnancy and parturition. In this study, we sought to investigate the signal transduction mechanisms of CRH Type-1 receptors in the feto-placental unit. To clarify the signal transduction components in placenta and fetal membranes, we investigated the expression of G proteins and adenylate cyclase. Using the nonhydrolysable photoreactive analog [α-32P] GTP-azidoanilide and peptide antisera raised against G proteinα -subunits, we studied coupling of CRH receptors to G proteins in both placental and fetal membranes. Treatment of placental membranes with human CRH (100 nm) increased the labeling of Gq, Go, and Gz but not Gi and Gs. Treatment of fetal membranes with human CRH (100 nm) increased the labeling of Go and Gq but not Gi, Gs, and Gz. These results were supported by experiments that showed that CRH failed to activate adenylate cyclase in these tissues, but induced an increase in inositol phosphates instead. These findings provide new insights into the components of the signal transduction machinery in both fetal and placental membranes and suggest that CRH Type-1 receptors can couple to different G proteins in different tissues. The physiological significance of these observations remains to be elucidated.