The subfamily B1 of hormone receptors (secretin-like), member of the class B family seven-transmembrane G protein-coupled receptors
The B1 subfamily of class B GPCRs, also referred to as secretin-like receptor family, includes receptors for polypeptide hormones of 27-141 amino-acid residues such as secretin, glucagon, glucagon-like peptide (GLP), calcitonin gene-related peptide, parathyroid hormone (PTH), and corticotropin-releasing factor. These receptors contain the large N-terminal extracellular domain (ECD), which plays a critical role in hormone recognition by binding to the C-terminal portion of the peptide. On the other hand, the N-terminal segment of the hormone induces receptor activation by interacting with the receptor transmembrane domains and connecting extracellular loops, triggering intracellular signaling pathways. All members of this subfamily preferentially couple to G proteins of G(s) family, which positively stimulate adenylate cyclase, leading to increased intracellular cAMP formation and calcium influx. Moreover, the B1 subfamily receptors play key roles in hormone homeostasis and are promising drug targets in various human diseases including diabetes, osteoporosis, obesity, neurodegenerative conditions (Alzheimer###s and Parkinson's), cardiovascular disease, migraine, and psychiatric disorders (anxiety, depression). Furthermore, the subfamilies B2 and B3 consist of receptors that are capable of interacting with epidermal growth factors (EGF) and the Drosophila melanogaster Methuselah gene product (Mth), respectively. The class B GPCRs have been identified in all the vertebrates, from fishes to mammals, as well as invertebrates including Caenorhabditis elegans and Drosophila melanogaster, but are not present in plants, fungi, or prokaryotes.
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