3D Structure of Torpedo californica Acetylcholinesterase Complexed with Huprine X at 2.1 Å Resolution:  Kinetic and Molecular Dynamic Correlates^,

Abstract

Huprine X is a novel acetylcholinesterase (AChE) inhibitor, with one of the highest affinities reported for a reversible inhibitor. It is a synthetic hybrid that contains the 4-aminoquinoline substructure of one anti-Alzheimer drug, tacrine, and a carbobicyclic moiety resembling that of another AChE inhibitor, (-)-huperzine A. Cocrystallization of huprine X with Torpedo californica AChE yielded crystals whose 3D structure was determined to 2.1 A resolution. The inhibitor binds to the anionic site and also hinders access to the esteratic site. Its aromatic portion occupies the same binding site as tacrine, stacking between the aromatic rings of Trp84 and Phe330, whereas the carbobicyclic unit occupies the same binding pocket as (-)-huperzine A. Its chlorine substituent was found to lie in a hydrophobic pocket interacting with rings of the aromatic residues Trp432 and Phe330 and with the methyl groups of Met436 and Ile439. Steady-state inhibition data show that huprine X binds to human AChE and Torpedo AChE 28- and 54-fold, respectively, more tightly than tacrine. This difference stems from the fact that the aminoquinoline moiety of huprine X makes interactions similar to those made by tacrine, but additional bonds to the enzyme are made by the huperzine-like substructure and the chlorine atom. Furthermore, both tacrine and huprine X bind more tightly to Torpedo than to human AChE, suggesting that their quinoline substructures interact better with Phe330 than with Tyr337, the corresponding residue in the human AChE structure. Both (-)-huperzine A and huprine X display slow binding properties, but only binding of the former causes a peptide flip of Gly117.

Shogaol–huprine hybrids: Dual antioxidant and anticholinesterase agents with β-amyloid and tau anti-aggregating properties

“…27 Thus, the huprine unit was located in the pocket defined by residues Trp86 and Tyr337 in the CAS, forming a direct hydrogen-bond contact with the carbonyl oxygen of His447. In fact, the binding mode reproduces the main features of the arrangement found for (-)-huprine X, the 9-ethylanalogue of huprine Y, bound to the Torpedo californica AChE (PDB entry 1E66), 28 and for (-)-huprine W, which bears a hydroxyethyl group at position 9, bound to the human enzyme (PDB entry 4BDT). 29 On the other hand, the phenolic ring stacked against Trp286 in the PAS (Fig.…”

Synthesis and Multitarget Biological Profiling of a Novel Family of Rhein Derivatives As Disease-Modifying Anti-Alzheimer Agents

“…94 The orientation of Tyr337 residue was modified to mimic the conformation of the equivalent residue Phe330 in the complex between TcAChE and (-)-huprine X (PDB 1E66). 39 To explore the binding at the PAS, three different AChE models differing in the orientation of Trp286 were built. The side chain of Trp286 was oriented following the three orientations found in X-ray structures deposited in the Protein Data Bank, which can be characterized by dihedral angles  1 (NC  C  C  ) and  2 (C  C  C  C 2 ) close to i) 60 and 80, ii) 120 and +50, and iii) 160 and 120 degrees.…”

“…Herein, we describe the synthesis, biological profiling, and investigation of the mechanism of action of a novel family of multi-target hybrid compounds, which are composed of a unit of rhein attached, through different linkers, to a unit of huprine Y, 4 (Chart 1), a high affinity AChE's CAS inhibitor, developed in our group some years ago. [36][37][38][39] The biological profiling includes i) the in vitro evaluation of the inhibitory activities against hAChE, human butyrylcholinesterase (hBChE), hAChE-induced and self-induced Aβ aggregation, and human…”

1,2,3,4-Tetrahydrobenzo[h][1,6]naphthyridines as a new family of potent peripheral-to-midgorge-site inhibitors of acetylcholinesterase: Synthesis, pharmacological evaluation and mechanistic studies

“…It is worth noting that previous studies strongly support the excellent performance of rDock for predicting the binding mode of a variety of AChE inhibitors to the enzyme gorge [9]. A cavity of radius 17 Å, centered on the structure of a superligand containing huprine X, donepezil and propidium (as found in the X-ray structures 1E66 [34], 1EVE and 1N5R) was used to define the docking volume. Since huprine X and propidium are bound to the catalytic and peripheral binding sites, and donepezil is aligned along the gorge, this definition guarantees the exploration of the binding mode along the whole volume accessible for binding.…”