Molecular Signature for Receptor Engagement in the Metabolic Peptide Hormone Amylin

The
pancreatic peptide hormone, amylin, plays a critical role in the control
of appetite, and synergizes with other key metabolic hormones such
as glucagon-like peptide 1 (GLP-1). There is opportunity to develop
potent and long-acting analogues of amylin or hybrids between these
and GLP-1 mimetics for treating obesity. To achieve this, interrogation
of how the 37 amino acid amylin peptide engages with its complex receptor
system is required. We synthesized an extensive library of peptides
to profile the human amylin sequence, determining the role of its
disulfide loop, amidated C-terminus and receptor
“capture” and “activation” regions in
receptor signaling. We profiled four signaling pathways with different
ligands at multiple receptor subtypes, in addition to exploring selectivity
determinants between related receptors. Distinct roles for peptide
subregions in receptor binding and activation were identified, resulting
in peptides with greater activity than the native sequence. Enhanced
peptide activity was preserved in the brainstem, the major biological
target for amylin. Interpretation of our data using full-length active
receptor models supported by molecular dynamics, metadynamics, and
supervised molecular dynamics simulations guided the synthesis of
a potent dual agonist of GLP-1 and amylin receptors. The data offer
new insights into the function of peptide amidation, how allostery
drives peptide–receptor interactions, and provide a valuable
resource for the development of novel amylin agonists for treating
diabetes and obesity.