Uncovering the selectivity mechanism of phosphodiesterase 7A/8A inhibitors through computational studies

The expression of phosphodiesterase 7A (PDE7A) and phosphodiesterase 8A (PDE8) genes is integral to human signaling pathways, and the inhibition of PDE7A has been associated with the onset of various diseases, including effects on the immune system and nervous system. The development of PDE7 selective inhibitors can promote research on immune and nervous system diseases, such as multiple sclerosis, chronic inflammation, and autoimmune responses. PDE8A is expressed alongside PDE8B, and its inhibitory mechanism is still unclear. Studying the mechanisms of selective inhibitors against different PDE subtypes is crucial to prevent potential side effects, such as nausea and cardiac toxicity, and the sequence similarity of the two protein subtypes was 55.9%. Therefore, it is necessary to investigate the differences of both subtypes' ligand binding sites. Selective inhibitors of two proteins were chosen to summarize the reason for their selectivity through molecular docking, molecular dynamics simulation, alanine scanning mutagenesis, and MM-GBSA calculation. We found that Phe384^PDE7A, Leu401^PDE7A, Gln413^PDE7A, Tyr419^PDE7A, and Phe416^PDE7A in the active site positively contribute to the selectivity towards PDE7A. Additionally, Asn729^PDE8A, Phe767^PDE8A, Gln778^PDE8A, and Phe781^PDE8A positively contribute to the selectivity towards PDE8A.