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The occurrence of orthosteric and allosteric binding sites is a characteristic common feature of several acetylcholine- binding proteins, like acetylcholinesterase or the nicotinic and muscarinic acetylcholine receptors. These proteins are involved in a number of neurological disorders, such as Alzheimer's disease, and represent important therapeut...
Context in source publication
Context 1
... series of tacrine-derived cholinesterase inhibitors have been synthesized so far, that contain the hydrazide linker Fig. (3) [125]. Using a linker of type K trimethoxy- benzoic or trimethoxyphenylpropionic acid were connected to the tacrine heterocycle by means of -aminoalkyl- carboxylic acids of varying length providing compounds 1 and 2. Extensive inhibition studies on acetyl-and butyryl- cholinesterase from several organisms (Electrophorus elec- tricus, ...
Citations
... A sizeable decline in development of classical agonists and antagonist for medication [1-3] has elicited a drug-hunt to construct and develop allosters in laboratories of academia [4-8] and industry (e.g., Novasite Pharmaceuticals Inc; Addex Pharmaceuticals), including positive and negative allosters as well as ortho-allosters for therapeutic purposes. In doing so, it has become important to simulate and analyse concentration-response data for allosters by models that are as close to the systems mechanistic function as possible. ...
Introduction
Two recent models are in use for analysis of allosteric drug action at receptor sites remote from orthosteric binding sites. One is an allosteric two-state mechanical model derived in 2000 by David Hall. The other is an extended operational model developed in 2007 by Arthur Christopoulos’s group. The models are valid in pharmacology, enzymology, transportology as well as several other fields of biology involving allosteric concentration effects.
Results
I show here that Hall’s model for interactions between an orthoster, an alloster, and a receptive unit is the best choice of model both for simulation and analysis of allosteric concentration-responses at equilibrium or steady-state.
Conclusions
As detailed knowledge of receptors systems becomes available, systems with several pathways and states and/ or more than two binding sites should be analysed by extended forms of the Hall model rather than for instance a Hill type exponentiation of terms as introduced in non-mechanistic (operational) model approaches; yielding semi-quantitative estimates of actual system parameters based on Hill’s unlikely simultaneity model for G protein-coupled receptors.
... Like the PAMs at M 1 mAchRs, allosteric M 1 agonists such as 15 have potential for the treatment of Alzheimer's disease and schizophrenia. Another approach at muscarinic receptors has been the development of hybrid (bitopic or dualsteric) ligands consisting of two parts, one interacting with the orthosteric site, the other one with the allosteric site, connected by a linker ( Disingrini et al., 2006;Valant et al., 2009;Mohr et al., 2010;Elsinghorst et al., 2011). The approach is expected to confer receptor subtype selectivity to an orthosteric ligand. ...
Rhodopsin-like (class A) G protein-coupled receptors (GPCRs) are one of the most important classes of drug targets. The discovery that these GPCRs can be allosterically modulated by small drug molecules has opened up new opportunities in drug development. It will allow the drugability of "difficult targets", such as GPCRs activated by large (glyco)proteins, or by very polar or highly lipophilic physiological agonists. Receptor subtype selectivity should be more easily achievable with allosteric than with orthosteric ligands. Allosteric modulation will allow a broad spectrum of pharmacological effects largely expanding that of orthosteric ligands. Furthermore, allosteric modulators may show an improved safety profile as compared to orthosteric ligands. Only recently, the explicit search for allosteric modulators has been started for only a few rhodopsin-like GPCRs. The first negative allosteric modulators (allosteric antagonists) of chemokine receptors, maraviroc (CCR5 receptor), used in HIV therapy, and plerixafor (CXCR4 receptor) for stem cell mobilization, have been approved as drugs. The development of allosteric modulators for rhodopsin-like GPCRs as novel drugs is still at an early stage; it appears highly promising.
Blockade of A2A adenosine receptors (A2AARs) and inhibition of monoamine oxidase B (MAO-B) in the brain are considered attractive strategies for the treatment of neurodegenerative diseases such as Parkinson's disease (PD). In the present study, benzothiazinones, e.g., 2-(3-chlorophenoxy)-N-(4-oxo-4H-3,1-benzothiazin-2-yl)acetamide (13), were identified as a novel class of potent MAO-B inhibitors (IC50 human MAO-B: 1.63 nM). Benzothiazinones with large substituents in the 2-position, e.g., methoxycinnamoylamino, phenylbutyrylamino, or chlorobenzylpiperazinylbenzamido residues (14, 17, 27, and 28), showed high affinity and selectivity for A2AARs (Ki human A2AAR: 39.5-69.5 nM). By optimizing benzothiazinones for both targets, the first potent, dual-acting A2AAR/MAO-B inhibitors with a nonxanthine structure were developed. The best derivative was N-(4-oxo-4H-3,1-benzothiazin-2-yl)-4-phenylbutanamide (17, Ki human A2A, 39.5 nM; IC50 human MAO-B, 34.9 nM; selective versus other AR subtypes and MAO-A), which inhibited A2AAR-induced cAMP accumulation and showed competitive, reversible MAO-B inhibition. The new compounds may be useful tools for validating the A2AAR/MAO-B dual target approach in PD.
The title compound (II) is easily prepared from salt (I) and coupled with various oxygen-, sulfur-, and nitrogen-containing nucleophiles.
Three types of aromatic-polyamine conjugates (6a-6s) were designed, synthesized and evaluated as potential inhibitors for cholinesterases (ChEs). The results showed that anthraquinone-polyamine conjugates (AQPCs) exhibited the most potent acetylcholinesterase (AChE) inhibitory activity with IC50 values from 1.50 to 11.13 mu M. Anthracene-polyamine conjugates (APCs) showed a surprising selectivity (from 76- to 3125-fold) and were most potent at inhibiting butyrylcholinesterase (BChE), with IC50 values from 0.016 to 0.657 mu M. A Lineweaver-Burk plot and molecular modeling studies indicated that the representative compounds, 6l and 6k, targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of ChEs. Furthermore, APCs did not affect HepG2 cell viability at the concentration of 100 mu M. Consequently, these polyamine conjugates could be thoroughly and systematically studied for the treatment of AD.
Two series of novel pyrazolobenzothiazine-based hybrid compounds were efficiently synthesized starting from saccharin sodium salt. Pyrazolo[4,3-c][1,2]benzothiazine scaffolds were N-arylated by using p-fluorobenzaldehyde, followed by the incorporation of a benzimidazole or similar ring systems by treatment with arylenediamines. These phenylene-connected hybrid compounds were investigated as potential inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Compounds 12d and 12k were the most potent AChE inhibitors with IC50 values of 11 and 13 nM, respectively, while 6j (IC50 = 17 nM) proved to be the most active inhibitor against BuChE with remarkable selectivity for BuChE over AChE. Molecular docking studies were also performed on human AChE and BuChE to suggest possible binding modes in which the inhibitor's extended structure is accommodated along the active site gorge of both enzymes.
Introduction:
The continuous application of organophosphate pesticides in developing countries, in addition to the remaining stock piles of chemical warfare nerve agents and their possible use is a significant threat to the public. Yet, today's options for a treatment of organophosphorus poisonings are still inadequate.
Areas covered:
This article provides a concise overview of current and future research trying to improve both prophylaxis and treatment of organophosphorus intoxications. The authors provide a summary of current oxime therapy and highlight several new concepts to overcome existing gaps. This overview of therapeutic options is accompanied by two sections on cyclodextrins, related compounds and bioscavengers, which may be used for either prophylaxis or treatment. For both groups, the authors review current drug design and screening approaches, the resulting developments and future challenges.
Expert opinion:
While the search for one multipotent oxime has been a fruitless endeavor, combination of multiple oximes with complemental and systemic reactivity appears as a valuable concept. Development of potential scavengers, be it cyclodextrins or bioscavengers, is still hampered by insufficient efficacy of these compounds. Future strategies will aim at improving their catalytic efficacy while minimizing immunogenicity.
