Peptide modulators of Methuselah, a G protein-coupled receptor associated with extended lifespan

William W. Ja1, Anthony P. West², Pamela J. Bjorkman³, Seymour Benzer, Richard W. Roberts⁴

Mutation in the methuselah (mth) gene results in a 30% increase in average lifespan and enhanced resistance to a variety of stresses, including starvation and hyperoxia. Mth is a G protein-coupled receptor (7 transmembrane structure) with an ~25-kDa, N-terminal ectodomain. Previously, using mRNA display of large random libraries, our laboratory isolated peptides that bind the Mth ectodomain. These peptides demonstrated high affinity to the ectodomain, with dissociation constants from 15 to 60 nM. A low-resolution crystal structure of a Mth ectodomains:peptide complex revealed that the peptide binds at a putative interaction site between the extracellular loops and the ectodomains of Mth. As GPCR signaling is generally transduced through movements of the transmembrane domains, the structural data suggest that the peptides could act as modulators of Mth signaling.

Recently, Cvejic et al. (2004) published the discovery of Stunted, a natural agonist for Mth; a eukaryotic cell line stably expressing Mth was used in a calcium-signaling assay to isolate agonists from fractionated fly lysates. Using this assay, we have determined that a number of our in vitro selected peptides act as antagonists of the Mth signaling by Stunted. The most potent peptides exhibit submicromolar IC50 values. The application of these peptides toward the synthetic extension of Drosophila lifespan is currently being tested.

¹Graduate Student, Chemistry, Caltech

²Postdoctoral Scholar, Bjorkman Lab, Caltech

³Professor of Biology, Caltech

⁴Assistant Professor of Chemistry, Caltech

Reference

Cvejic, S., Zhu, Z., Felice, S.J., Berman, Y. and Huang, X.Y. (2004) Nat. Cell Biol. 6:540-546.