title: The agouti-related peptide binds heparan sulfate through segments critical for its orexigenic effects.
abstract: Syndecans potently modulate agouti-related peptide (AgRP) signaling in the central melanocortin system. Through heparan sulfate moieties, syndecans are thought to anchor AgRP near its receptor, enhancing its orexigenic effects. Original work proposed that the N-terminal domain of AgRP facilitates this interaction. However, this is not compatible with evidence that this domain is posttranslationally cleaved. Addressing this long-standing incongruity, we used calorimetry and magnetic resonance to probe interactions of AgRP peptides with glycosaminoglycans, including heparan sulfate. We show that mature, cleaved, C-terminal AgRP, not the N-terminal domain, binds heparan sulfate. NMR shows that the binding site consists of regions distinct from the melanocortin receptor-binding site. Using a library of designed AgRP variants, we find that the strength of the syndecan interaction perfectly tracks orexigenic action. Our data provide compelling evidence that AgRP is a heparan sulfate-binding protein and localizes critical regions in the AgRP structure required for this interaction.
authors.affiliation: From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064.
authors.forename: Rafael
authors.initials: R
authors.lastname: Palomino
authors.affiliation: From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064.
authors.forename: Hsiau-Wei
authors.initials: HW
authors.lastname: Lee
authors.affiliation: From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064 glennm@ucsc.edu.
authors.forename: Glenn L
authors.initials: GL
authors.lastname: Millhauser
mesh_terms: D054369:Agouti-Related Protein / Q000737:chemistry* / Q000378:metabolism; D006497:Heparan Sulfate / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains
chemical_list: D054369:Agouti-Related Protein; D006497:Heparan Sulfate; D010455:Peptides; C515198:AGRP protein, human
keywords: AgRP; G protein-coupled receptor (GPCR); glycosaminoglycan; heparan sulfate; heparin-binding protein; mc4r; neuropeptide; syndecan