Targeting inhibition of microtubule affinity regulating kinase 4 by Harmaline: Strategy to combat Alzheimer's disease

Abstract

Microtubule-affinity regulating kinase 4 (MARK4) is linked with the development of cancer, diabetes and neurodegenerative diseases. Due to its direct role in the hyperphosphorylation of tau protein, MARK4 is considered as an attractive target to fight Alzheimer's disease (AD) and neuroinflammation. In the present study, we have selected Harmaline (HAR), an alkaloid of Paganum harmala, to investigate its MARK4 inhibitory potential and its binding mechanism. Molecular docking and fluorescence binding studies were carried out to estimate the binding affinity of the HAR with the MARK4. We observed an excellent binding affinity of HAR to the MARK4 (K = 10⁷ M^-1), further complemented by isothermal titration calorimetric measurements. In addition, HAR significantly inhibits the kinase activity of MARK4 (IC₅₀ value of 4.46 μM). Structural investigations suggested that HAR binds to the active site pocket and forms several non-covalent interactions with biologically important residues of MARK4. All-atom molecular dynamics simulation studies further advocated that the MARK4-HAR complex is stabilized throughout the trajectory of 200 ns and causes a little conformational change. All these findings suggest that HAR is a potential MARK4 inhibitor that can be implicated in managing MARK4-associated diseases, including AD.

Keywords: Alzheimer's disease; Drug discovery; Harmaline; Kinase inhibitors; MD simulations; Microtubule affinity regulating kinase 4; Molecular docking.