Poster Presentation The 48th Lorne Conference on Protein Structure and Function 2023

Toward a structural understanding of amylin receptor phenotype: implications for therapeutic development for obesity (#334)

Jian-Jun Cao 1 2 , Matthew Belousoff 2 3 , Radostin Danev 4 , Emma dal Maso 1 2 , Rachel Johnson 1 2 , Herman Schreuder 5 , Katrin Lorenz 5 , Andreas Evers 6 , Garima Tiwari 7 , Ziyu Li 5 , Denise Wootten 1 2 , Patrick Sexton 1 2
  1. Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
  2. ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
  3. Monash Institute of Pharmaceutical Sciences, Parkville, VIC, Australia
  4. Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan
  5. Sanofi-Aventis Deutschland GmbH, R&D, Frankfurt am Main, Germany
  6. Merck Healthcare KGaA, Darmstadt, Germany
  7. Janssen Vaccines and Prevention B.V., Leiden, The Netherlands

Amylin receptors respond to a 37-amino acid endocrine peptide, amylin (Amy). Targeting amylin receptors (AMYRs) can reduce body weight with additional benefits to other anti-obesity treatments1. AMYRs are heterodimers of the calcitonin receptor (CTR) and one of three receptor activity-modifying proteins (RAMPs), yielding AMY1R (CTR-RAMP1), AMY2R(CTR-RAMP2) and AMY3R(CTR-RAMP3), respectively.  Expressed alone, CTRs exhibit high potency for human calcitonin (hCT) but a low potency for Amy in functional assays2. In addition, there are dual amylin and calcitonin receptor agonists (DACRAs), having high affinity and potency for both CTR and AMYRs. DACRAs appear to possess a greater potential for metabolic control than selective amylin mimetics, despite the observations that selective activation of CTR by hCT does not elicit weight loss1. 

Our previous work identified a hallmark of AMYR activation by Amy is the formation of a secondary structural motif, termed a “bypass motif” (residues S19-P25) that partly contributes to the selective activation of cAMP responses at AMYRs over CTR. In contrast, CT bound to an AMYR conformation, distinct from that bound to rAmy, which mimicked the conformation of the CT bound CTR3. The different mechanisms of activation of AMYRs by Amy or CT peptides lead to implications for the rational design of selective or non-selective derivatives using CT and Amy template peptides. This study explored the feasibility of tuning the selectivity of Amy analogues by modifying the residues (19-22) located within the bypass motif, resulting in a selective AMYR agonist, San385, as well as a series of non-selective DACRAs, with San45 being an exemplar. We determined the structure and dynamics of San385-bound AMY3R, as well as San45-bound AMY3R and CTR, decoding the structure-activity relationship (SAR) of these peptides. In particular, San45 is conjugated at position 19 with a lipid modification that anchors the peptide at the edge of the receptor bundle and enables an alternate binding mode when bound to the CTR, in addition to the bypass mode of binding to AMY3R. This unique mechanism provides a single intervention strategy through targeted lipid modification to the structure-based design of long-acting, non-selective, Amy-based DACRAs with potential anti-obesity effects.

  1. Zakariassen, H. L.; John, L. M.; Lutz, T. A., Central control of energy balance by amylin and calcitonin receptor agonists and their potential for treatment of metabolic diseases. Basic Clin Pharmacol Toxicol 2020, 127 (3), 163-177.
  2. Udawela, M.; Christopoulos, G.; Morfis, M.; Christopoulos, A.; Ye, S.; Tilakaratne, N.; Sexton, P. M., A critical role for the short intracellular C terminus in receptor activity-modifying protein function. Mol Pharmacol 2006, 70 (5), 1750-60.
  3. Cao, J.; Belousoff, M. J.; Liang, Y.-L.; Johnson, R. M.; Josephs, T. M.; Fletcher, M. M.; Christopoulos, A.; Hay, D. L.; Danev, R.; Wootten, D.; Sexton, P. M., A structural basis for amylin receptor phenotype. Science 2022, 375 (6587), eabm9609.