The pigment dispersing factor receptor, member of the class B seven-transmembrane G protein-coupled receptors
The pigment dispersing factor receptor (PDFR) is a G protein-coupled receptor that binds the circadian clock neuropeptide PDF, a functional ortholog of the mammalian vasoactive intestinal peptide (VIP), on the pacemaker neurons. The PDFR is implicated in regulating flight circuit development and in modulating acute flight In Drosophila melanogaster. The PDFR activation stimulates adenylate cyclase, thereby increasing cAMP levels in many different pacemakers, and the receptor signaling has been shown to regulate behavioral circadian rhythms and geotaxis in Drosophila. The PDFR belongs to the B1 subfamily of class B GPCRs, also referred to as secretin-like receptor family, which 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 the B1 subfamily preferentially couple to G proteins of G(s) family, which positively stimulate adenylate cyclase, leading to increased intracellular cAMP formation and calcium influx. They play key roles in hormone homeostasis in mammals and are promising drug targets in various human diseases including diabetes, osteoporosis, obesity, neurodegenerative conditions (Alzhemer's and Parkinson's), cardiovascular disease, migraine, and psychiatric disorders (anxiety, depression).