Peptidyl-Prolyl Isomerases as Promising Targets for Natural Product-Inspired Therapeutics.

[摘要] Peptidyl-prolyl isomerases (PPIases) are a ubiquitously expressed super family of proteins that catalyze the cis/trans isomerization of prolyl bonds. Proline conformation acts as a regulatory switch during folding, activation and/or degradation of ;;clients” that include proteins with roles in cancer and neurodegeneration. PPIase inhibitors, therefore, could be important therapeutics. However, the active site of PPIases is shallow and well conserved between members, challenging selective inhibitor design. Despite this, macrocyclic natural products, including FK506, rapamycin and cyclosporin, bind PPIases with nanomolar or better affinity. These natural products possess an unusual ;;bifunctional” binding mode and bind two separate proteins simultaneously, which is critical for their activity. They exhibit remarkable pharmacological properties, including oral bioavailability, and rapidly accumulate in cells with widespread tissue distribution. Inspired by this mechanism, I synthesized a library of bifunctional molecules that bind both FKBP12 and HIV protease. Like FK506, we envisioned a model where coincident, high-level expression of both targets - as in HIV-infected lymphocytes with high levels of FKBP12 and HIV protease - would drive cyto-selective sequestration. The library possessed varying affinities for each target, retained passive membrane permeability, and had cellular activity. Molecules highly potent for FKBP12 and HIV protease were selectively taken up into relevant cell populations. Treatment with FKBP12 inhibitors limited partitioning of the molecules, while FKBP12 overexpression enhanced it. This suggests that avidity effects drive selective accumulation of bifunctional molecules in cells expressing high levels of both protein partners.We next focused on Pin1, a unique PPIase that binds prolines directly following phosphoserine/threonine residues. The requirement for an electronegative group in the Pin1 active site renders many inhibitors inactive from poor permeability. We hypothesized that the excellent pharmacological properties of FK506 might make it a suitable scaffold for engineering Pin1 inhibitors. However, FK506 has little affinity for Pin1, because it lacks the key electronegative region essential for Pin1 binding. To overcome this, we designed a novel semisynthetic strategy to modify FK506 at a position to improve affinity for Pin1. Installing a sulfamic acid significantly improved the affinity for Pin1 (>100-fold) in vitro. This strategy is designed to yield high-affinity membrane-permeable inhibitors of Pin1.

[发布机构] University of Michigan

[效力级别] Peptidyl-prolyl isomerases (PPIases) as promising drug targets

[关键词] Natural-product inspired therapeutics;Peptidyl-prolyl isomerases (PPIases) as promising drug targets;Enhanced pharmacological properties of bifunctional molecules;Semisynthetic modification of macrolide immunosuppressants;Biological Chemistry;Science;Biological Chemistry