Human Melatonin Receptor 1B (MTNR1B) Protein

Background

MTNR1B, also known as MT2, is a G protein-coupled receptor for melatonin, expressed in the retina, pancreas, and central nervous system. Like MTNR1A, MTNR1B inhibits adenylate cyclase activity through Gi proteins, reducing cAMP levels and modulating circadian rhythms, sleep regulation, and metabolic processes. MTNR1B plays a critical role in glucose metabolism by regulating insulin secretion in pancreatic β-cells, where melatonin signaling affects insulin release and glucose homeostasis. Genetic variants in MTNR1B have been strongly associated with an increased risk of type 2 diabetes, highlighting its role in impaired glucose tolerance and β-cell dysfunction. In the retina, MTNR1B helps regulate photoreceptor sensitivity and circadian rhythms, contributing to visual function. Dysregulation of MTNR1B signaling has been linked to sleep disturbances, metabolic disorders, and impaired glucose regulation. MTNR1B is being explored as a therapeutic target for managing type 2 diabetes, circadian rhythm disorders, and sleep-related conditions, emphasizing its dual role in metabolic and circadian regulation.