Structure-based rational design of high-affinity JAZF1 variants peptides to target the testicular orphan nuclear receptor 4 and pro-opiomelanocortin axis in Cushing's disease.

The regulation of pro-opiomelanocortin (Pomc) expression by the testicular orphan receptor 4 (TR4) constitutes a critical mechanism underlying the pathogenesis of Cushing's disease (CD). Although the endogenous repressor juxtaposed with another zinc finger gene 1 (JAZF1) inhibits TR4 activity, its relatively low binding affinity (KD = 2246 nM) limits its therapeutic potential. In this study, we employed an iterative structure-based lead optimization strategy to enhance the JAZF1 scaffold. Utilizing Discovery Studio for virtual screening, we conducted successive rounds of in silico saturation mutagenesis, ranging from single point to multi-site combinatorial substitutions, which were subsequently validated through incremental experimental binding assays. This recursive optimization process led to the identification of two triple-mutant JAZF1 peptides (V56L/A68Y/A69R and D67L/A68Y/A69R) exhibiting more than a 2,200-fold enhancement in TR4 binding affinity. These engineered peptides, along with high-affinity small molecules such as nilotinib (KD = 4.83 nM), effectively downregulated Pomc expression and inhibited proliferation of AtT-20 tumor cells. Taken together, these findings suggest that the JAZF1-TR4-Pomc axis may serve as a potential therapeutic target for modulating adrenocorticotropic hormone (ACTH) hypersecretion in CD.