Thyrotropin-releasing hormone receptors -- similarities and differences.
Thyrotropin-releasing hormone (TRH) initiates its effects by interacting with cell-surface membrane receptors. Two G protein-coupled receptors for TRH, TRH receptor type 1 (TRH-R1) and TRH receptor type 2 (TRH-R2), have been cloned from mammals. In this review, we compare TRH-R1 and TRH-R2 with regard to their tIssue distribution, binding affinities for TRH and TRH analogs, basal and activated signaling activities and characteristics of internalization. TRH-R1 and TRH-R2 are distributed differently in the brain and peripheral tIssues, but exhibit indistinguishable binding affinities for TRH and TRH analogs. Although they both can be stimulated by TRH to similar maximal signaling levels, TRH-R2 exhibits higher basal signaling activity and is more rapidly internalized than TRH-R1. These differences in signaling and internalization properties are probably important in the distinct parts that TRH-R1 and TRH-R2 may play in mammalian physiology.
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National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892-1818, USA.
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Gershengorn
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D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000378:metabolism*; D014018:Tissue Distribution
D020033:Protein Isoforms; D018025:Receptors, Thyrotropin-Releasing Hormone; D013973:Thyrotropin-Releasing Hormone; D019204:GTP-Binding Proteins