Abstract
Microtubule affinity-regulating kinase (MARK4) plays a key role in Alzheimer’s disease (AD) development as its overexpression is directly linked to increased tau phosphorylation. MARK4 is a potential drug target of AD and is thus its structural features are employed in the development of new therapeutic molecules. Donepezil (DP) and rivastigmine tartrate (RT) are acetylcholinesterase (AChE) inhibitors and are used to treat symptomatic patients of mild to moderate AD. In keeping with the therapeutic implications of DP and RT in AD, we performed binding studies of these drugs with the MARK4. Both DP and RT bound to MARK4 with a binding constant (K) of 107 M−1. The temperature dependency of binding parameters revealed MARK−DP complex to be guided by static mode while MARK−RT complex to be guided by both static and dynamic quenching. Both drugs inhibited MARK4 with IC50 values of 5.3 μM (DP) and 6.74 μM (RT). The evaluation of associated enthalpy change (ΔH) and entropy change (ΔS) implied the complex formation to be driven by hydrogen bonding making it seemingly strong and specific. Isothermal titration calorimetry further advocated a spontaneous binding. In vitro observations were further complemented by the calculation of binding free energy by molecular docking and interactions with the functionally-important residues of the active site pocket of MARK4. This study signifies the implications of AChE inhibitors, RT, and DP in Alzheimer’s therapy targeting MARK4.
Highlights
Cellular functions of the human body are governed by protein phosphorylation and dephosphorylation by protein kinases and phosphatases [1,2]
MARK4 is being used as a drug target for the development of therapeutic molecules in Alzheimer’s therapy
Overexpression of MARK4 is directly linked to the tau hyperphosphorylation which is a key event in Alzheimer’s diseases (AD) pathology highlighting the clinical significance of developing molecules with inhibitory potential against MARK4
Summary
Cellular functions of the human body are governed by protein phosphorylation and dephosphorylation by protein kinases and phosphatases [1,2]. The human genome encodes many protein kinases, among them many are considered as potential targets for drug design and development. Owing to its remarkable role in neurodegenerative disorders, MARK4 presents a novel therapeutic target, and recently many studies have reported MARK4 inhibitors that can be used to treat MARK4-directed diseases. Drug−protein interactions are important to study as the binding of a ligand/inhibitor to protein affects its pharmacokinetics [32]. RT is a carbamate inhibitor of AChE approved by the FDA for the treatment of mild to moderate AD in adults [33] It improves the patient’s condition in all three major domains: cognitive function, global function, and behavior [34]. Post ligand binding to a protein, the structure and functionality are affected making it important to study drug−protein interactions. The binding mechanism and efficacy of DP and RT with MARK4 were investigated by spectroscopic, calorimetric, and cell-free enzyme assay complemented by molecular docking
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