Inhibition of microtubule affinity regulating kinase 4 by an acetylcholinesterase inhibitor, Huperzine A: Computational and experimental approaches

Microtubule affinity regulating kinase 4 (MARK4), 752 amino acids long, belonging to the AMPK superfamily, plays a vital role in regulating microtubules due to its potential to phosphorylate microtubule-associated proteins (MAP's) and thus, MARK4 plays a key role in Alzheimer's disease (AD) pathology. MARK4 is a druggable target for cancer, neurodegenerative diseases, and metabolic disorders. In this study, we have evaluated the MARK4 inhibitory potential of Huperzine A (HpA), an acetylcholinesterase inhibitor (AChEI), a potential AD drug. Molecular docking revealed the key residues governing the MARK4-HpA complex formation. The structural stability and conformational dynamics of the MARK4-HpA complex was assessed by employing Molecular dynamics (MD) simulation. The results suggested that the binding of HpA with MARK4 leads to minimal structural alterations in the native conformation of MARK4, implying the stability of the MARK4-HpA complex. Isothermal titration calorimetry (ITC) studies deciphered that HpA binds to MARK4 spontaneously. Moreover, the kinase assay depicted significant inhibition of MARK by HpA (IC₅₀ = 4.91 μM), implying it to be a potent MARK4 inhibitor that can be implicated in the treatment of MARK4-directed diseases.