ESPE Abstracts

Congenital adrenal hyperplasia (CAH) is a common disorder of steroid production mainly caused by a mutated CYP21A2 gene, causing 21-hydroxylase deficiency (21OHD). CAH due to 21OHD requires lifelong mineralocorticoid (MC) and glucocorticoid (GC) therapy. But, from the location of the enzyme block in the steroid production and increase of adrenocorticotropic hormone (ACTH) which stimulates the melanocortin type 2 receptor (MC2R) in the adrenal, excessive adrenal androgen production remains a challenging side effect for CAH even under MC and GC treatment. We modeled the interaction of ACTH with MC2R and designed peptides to understand ACTH binding and activation of MC2R. A model of MC2R was made using the recently described structure of MC4R protein. We docked the ACTH into the MC2R structure using AUTODOCK-VINA and performed Molecular dynamics simulations to study the ACTH-MC2R interactions. Details of ACTH binding to MC2R provided hints for the design of better peptides to block ACTH-MC2R interaction. We have analyzed the MC receptors and aligned the sequences of MC1R, MC2R, MC3R, MC4R, and MC5R to study the similarities and differences between these receptors. Sequence analysis identified two specific regions that are distinct for MC2R compared to other MC receptors and are also critical for the binding of ACTH to MC2R. Several rounds of peptide design were performed that use 4, 6, and 8 residues as linear as well as circular peptides for targeting MC2R. A sequence optimization of peptides and ACTH residues was performed to improve the peptide binding to MC2R and to improve peptide stability. Several of our designed peptides competed well with ACTH for binding to MC2R and inhibited the interaction of ACTH with MC2R. Downstream signaling of ACTH binding to MC2R was also inhibited by designed peptides. We have modeled the binding of ACTH to MC2R and designed antibodies that could target the ACTH-MC2R interaction and signaling. A new round of peptide design was made to improve upon our previous attempts to create more specific and tighter binding peptides to MC2R that can be used to block ACTH-MC2R interaction. Further improvements to create potent and stable peptides will further our understanding of ACTH-MC2R interaction as target for treatment of CAH caused by CYP21A2 deficiency.