title: Evidence for an interaction of neuronostatin with the orphan G protein-coupled receptor, GPR107.
abstract: Neuronostatin, derived from the somatostatin preprohormone, is a recently described peptide that is produced by several tissues involved in cardiovascular regulation and metabolism, including the hypothalamus. Injection of  neuronostatin into the lateral cerebroventricle led to a dose-related increase in mean arterial pressure (MAP) in rats. Any attempt to inhibit the production of neuronostatin would alter somatostatin production as well, making determination of the physiological relevance of the peptide's pharmacologic effects by compromise of production approaches impossible. Therefore, we employed an alternative approach to identify and compromise the production of the neuronostatin receptor. Because neuronostatin was shown to signal via a PKA-dependent mechanism, we hypothesized that the neuronostatin receptor was a G protein-coupled receptor (GPCR), in particular, one of the orphan GPCRs for which the ligand is unknown. Therefore, we screened neuronostatin-responsive tissues, including hypothalamus, heart, pancreatic α-cells, and the gastric tumor cell line KATOIII, for expression of orphan GPCRs. Four orphan GPCRs were expressed by all cell types, including GPR56 and GPR107. Knockdown of GPR107, but not GPR56 or GPR146, led to a loss of responsiveness to neuronostatin by KATOIII cells. Rats injected with siRNA directed against GPR107 (2 μg/day for 2 days) into the lateral cerebroventricle did not exhibit an increase in MAP in response to neuronostatin treatment. Rats with compromised GPR107 expression also displayed blunted reactivity in a baroreflex sensitivity test, indicating that GPR107 and neuronostatin may be important regulators of cardiovascular function. Thus, GPR107 is a promising candidate receptor for neuronostatin, and neuronostatin, interacting with GPR107, may play an important role in the central control of cardiovascular function.
authors.affiliation: Department of Pharmacological and Physiological Science, Saint Louis Univ. School of Medicine, 1402 S. Grand Blvd., St. Louis, MO 63104, USA. glcyosten@yahoo.com
authors.forename: Gina L C
authors.initials: GL
authors.lastname: Yosten
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Redlinger
authors.forename: Willis K
authors.initials: WK
authors.lastname: Samson
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D050416:Glucagon-Secreting Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D010446:Peptide Fragments / Q000378:metabolism*; D036361:Peptide Hormones / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D013004:Somatostatin / Q000378:metabolism*; D013274:Stomach Neoplasms / Q000378:metabolism / Q000473:pathology
chemical_list: C521099:GPR107 protein, human; C579288:GPR107 protein, mouse; C579287:GPR107 protein, rat; D010446:Peptide Fragments; D036361:Peptide Hormones; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; C554543:neuronostatin protein, rat; C579289:neuronostatin, human; C543371:neuronostatin, mouse; D013004:Somatostatin