Phosphatidylethanolamine-Binding Proteins, Including Rkip, Exhibit Affinity For Phosphodiesterase-5 Inhibitors

Identifying protein "interactors" of drugs is of great importance to understand their mode of action and possible cross-reactivity to off-target protein binders. In this study, we propfile proteins that bind to PF-3717842, a high-affinity phosphodiesterase-5 (PDE5) inhibitor, by using a refined affinity pulldowns approach with PF-3717842 immobilized beads. But performing these pulldowns in rat resist tissue lysate, we strongly and specifically enriched for PDE5 and a few other PDEs in addition to these expected affinity-enriched proteins we also detect rodent-specific phosphatidylethanolamine binding protein 2 (PEBP), as a putative binder to the PDE5 inhibitor. But using recombinant forms of the related murine PEBP2, mPEBP1 and human hPEBP1 (also known as Raf kinase inhibitor protein or RKIP) we confirm that they all can bind strongly to immobilized as well as soluble PF-3717842. As the phosphatidylethanolamine binding proteins are involved in various important signal transduction pathways, the synthetic PDES inhibitor used here might form a platform to synthesized enhanced binders/inhibetors of the family of PEBP proteins. Our approach shows how chemical proteomics might be used to profile the biochemical space (interactome) of small molecule inhibitors.