GPRnna14 and related proteins, member of the class A family of seven-transmembrane G protein-coupled receptors
This group includes the orphan G-protein coupled receptor GPRnna14 found in body louse (Pediculus humanus humanus) as well as its closely related proteins of unknown function. These receptors are members of the class A rhodopsin-like G-protein coupled receptors. As an obligatory parasite of humans, the body louse is an important vector for human diseases, including epidemic typhus, relapsing fever, and trench fever. GPRnna14 shares significant sequence similarity with the members of the neurotensin receptor family. All GPCRs have a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A general feature of GPCR signaling is agonist-induced conformational changes in the receptors, leading to activation of the heterotrimeric G proteins, which consist of the guanine nucleotide-binding G-alpha subunit and the dimeric G-beta-gamma subunits. The activated G proteins then bind to and activate numerous downstream effector proteins, which generate second messengers that mediate a broad range of cellular and physiological processes.