ABSTRACT
Gamma secretase activating protein (GSAP) present in ß-amyloid pathway orchestrates the formation of ß-amyloid plaques by γ-secretase activation and is an emerging therapeutic target for the treatment of Alzheimer's disease. It forms a ternary complex with γ-secretase and APP C-99. However, there are limited reports for the interaction of APP C-99 with GSAP. Here, we report the characterization of purified maltose binding protein (MBP) tagged human GSAP and its interaction with synthetic APP C-99 peptide fragments (712IATVIVITLVMLKKQ727 (712IQ727), 719TLVMLKKKQYTSIHHGVVEVDAAVT743 (719TT743) 734GVVEVDAAVTPEERHLSKMQQNGY757 (734GY757), and 746ERHLSKMQQNGYENPTYKFFEQMQN770 (746EN770)). The results emphasize the selective interaction of peptide (719TT743) with MBP-GSAP with a dissociation constant of 0.136 µM. Further, computational modeling of the GSAP-719TT743 complex finds an optimal bound pose of 719TT743 within an extended groove on the surface of GSAP. The preliminary results highlight the interaction between the two major proteins in the plausible ternary complex: APP C-99-GSAP-γ-secretase. It paves a futuristic path to investigate the GSAP-APP C-99 binding in detail and accentuates the role of GSAP in the ß-amyloid pathway.
Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor/metabolism , Plaque, Amyloid/metabolism , Humans , Molecular Dynamics SimulationABSTRACT
Amyloid beta (Aß) aggregation is the key trait responsible for the pathological devastation caused by Alzheimer's disease (AD). Among the various pathways of multifaceted toxicity exhibited by Aß aggregates in neuronal cells, generation of reactive oxygen species (ROS) by Aß-CuII complex and mitochondrial damage are prominent. Aß interferes with mitochondrial transport channels, causing mitochondrial dysfunction. Herein, we present nontoxic hybrid multifunctional modulators (HMMs, TGR86-88) developed by integrating the structural and functional features of the metal chelating aggregation modulator, clioquinol (Clq), and the antioxidant epigallocatechin gallate (EGCG). Detailed biophysical and docking studies show that TGR86 interacts with Aß and efficiently modulates both metal-dependent and metal-independent Aß aggregation. TGR86 complexes with CuII, arrests its redox cycle, and thereby prevents the generation of ROS. The antioxidant nature of the HMMs effectively prevents DNA damage and protein oxidation. TGR86 rescued PC12 cells from Aß-induced neurotoxicity by preventing the generation of ROS and foiling the interaction of toxic Aß species with mitochondria, thereby averting its damage. These key attributes make TGR86 a potential candidate to develop therapeutics for the multifactorial Aß toxicity in Alzheimer's disease.
