Regulation of melatonin 1a receptor signaling and trafficking by asparagine-124

Citation
Cs. Nelson et al., Regulation of melatonin 1a receptor signaling and trafficking by asparagine-124, MOL ENDOCR, 15(8), 2001, pp. 1306-1317
Citations number
61
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Endocrinology, Nutrition & Metabolism
Journal title
MOLECULAR ENDOCRINOLOGY
ISSN journal
0888-8809 → ACNP
Volume
15
Issue
8
Year of publication
2001
Pages
1306 - 1317
Database
ISI
SICI code
0888-8809(200108)15:8<1306:ROM1RS>2.0.ZU;2-W
Abstract
Melatonin is a pineal hormone that regulates seasonal reproduction and has been used to treat circadian rhythm disorders. The melatonin la receptor is a seven- transmembrane domain receptor that signals predominately via pert ussis toxin-sensitive G-proteins. Point mutations were created at residue N 124 in cytoplasmic domain II of the receptor and the mutant receptors were expressed in a neurohormonal cell line. The acidic N124D- and E-substituted receptors had high-affinity I-125-melatonin binding and a subcellular loca lization similar to the neutral N124N wild-type receptor. Melatonin efficac y for the inhibition of cAMP by N124D and E mutations was significantly dec reased. N124D and E mutations strongly compromised melatonin efficacy and p otency for inhibition of K+-Induced intracellular Ca++ fluxes and eliminate d control of spontaneous calcium fluxes. However, these substitutions did n ot appear to affect activation of Kir3 potassium channels. The hydrophobic N124L and N124A or basic N124K mutations failed to bind I-125-melatonin and appeared to aggregate or traffic improperly. N124A and N124K receptors wer e retained in the Golgi. Therefore, mutants at N124 separated into two sets : the first bound I-125-melatonin with high affinity and trafficked normall y, but with reduced inhibitory coupling to adenylyl cyclase and Ca++ channe ls. The second set lacked melatonin binding and exhibited severe traffickin g defects. In summary, asparagine-124 controls melatonin receptor function as evidenced by changes in melatonin binding, control of cAMP levels, and r egulation of ion channel activity. Asparagine-124 also has a unique structu ral effect controlling receptor distribution within the cell.