Methuselah-like subfamily B3, member of the class B family of seven-transmembrane G protein-coupled receptors
The subfamily B3 of class B GPCRs consists of Methuselah (Mth) and its closely related proteins found in bilateria. Mth was originally identified in Drosophila as a GPCR affecting stress resistance and aging. In addition to the seven transmembrane helices, Mth contains an N-terminal extracellular domain involved in ligand binding, and a third intracellular loop (IC3) required for the specificity of G-protein coupling. Drosophila Mth mutants showed an increase in average lifespan by 35% and greater resistance to a variety of stress factors, including starvation, high temperature, and paraquat-induced oxidative toxicity. Moreover, mutations in two endogenous peptide ligands of Methuselah, Stunted A and B, showed an increased in lifespan and resistance to oxidative stress induced by dietary paraquat. These results strongly suggest that the Stunted-Methuselah system plays important roles in stress response and aging.
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