Design, Optimization, and Structural Characterization of an Apoptosis-Inducing Factor Peptide Targeting Human Cyclophilin A to Inhibit Apoptosis Inducing Factor-Mediated Cell Death

Blocking the interaction between
the apoptosis-inducing factor
(AIF) and cyclophilin A (CypA) by the AIF fragment AIF(370–394)
is protective against glutamate-induced neuronal cell death and brain
injury in mice. Starting from AIF(370–394), we report the generation
of the disulfide-bridged and shorter variant AIF(381–389) and
its structural characterization by nuclear magnetic resonance (NMR)
in the free and CypA-bound state. AIF(381–389) in both the
free and bound states assumes a β-hairpin conformation similar
to that of the fragment in the AIF protein and shows a highly reduced
conformational flexibility. This peptide displays a similar in vitro affinity for CypA, an improved antiapoptotic activity
in cells and an enhanced proteolytic stability compared to the parent
peptide. The NMR-based 3D model of the AIF(381–389)/CypA complex
provides a better understanding of the binding hot spots on both the
peptide and the protein and can be exploited to design AIF/CypA inhibitors
with improved pharmacokinetic and pharmacodynamics features.