The COVID-19 disease is caused by a new strain of the coronavirus
family (SARS-CoV-2), and it has affected at present millions of
people all over the world. The indispensable role of the main
protease (M
pro
) in viral replication and gene
expression makes this enzyme an attractive drug target.
Therefore, inhibition of SARS-CoV-2 M
pro
as a
proposition to halt virus ingression is being pursued by
scientists globally. Here we carried out a study with two
objectives: the first being to perform comparative protein
sequence and 3D structural analysis to understand the effect of
12 point mutations on the active site. Among these, two
mutations, viz., Ser46 and Phe134, were found to cause a
significant change at the active sites of SARS-CoV-2. The Ser46
mutation present at the entrance of the S5 subpocket of
SARS-CoV-2 increases the contribution of other two hydrophilic
residues, while the Phe134 mutation, present in the catalytic
cysteine loop, can cause an increase in catalytic efficiency of
M
pro
by facilitating fast proton transfer from
the Cys145 to His41 residue. It was observed that active site
remained conserved among M
pro
of both SARS-CoVs,
except at the entrance of the S5 subpocket, suggesting
sustenance of substrate specificity. The second objective was to
screen the inhibitory effects of three different data sets
(natural products, coronaviruses main protease inhibitors, and
FDA-approved drugs) using a structure-based virtual screening
approach. A total of 73 hits had a combo score >2.0. Eight
different structural scaffold classes were identified, such as
one/two tetrahydropyran ring(s),
dipeptide/tripeptide/oligopeptide, large (approximately 20
atoms) cyclic peptide, and miscellaneous. The screened hits
showed key interactions with subpockets of the active site.
Further, molecular dynamics studies of selected screened
compounds confirmed their perfect fitting into the subpockets of
the active site. This study suggests promising structures that
can fit into the SARS-CoV-2 M
pro
active site and also
offers direction for further lead optimization and rational drug
design.
The
pathological hallmarks of Alzheimer’s disease (AD) are
manifested as an increase in the level of oxidative stress and aggregation
of the amyloid-β protein. In vitro, in vivo, and in silico experiments were
designed and carried out with multifunctional cholinergic inhibitor,
F24 (EJMC-7a) to explore its neuroprotective effects
in AD models. The neuroprotection ability of F24 was tested in SH-SY5Y
cells, a widely used neuronal cell line. The pretreatment and subsequent
co-treatment of SH-SY5Y cells with different doses of F24 was effective
in rescuing the cells from H2O2 induced neurotoxicity.
F24 treated cells were found to be effective in the reduction of cellular
reactive oxygen species, DNA damage, and Aβ1–42 induced neurotoxicity, which validated its neuroprotective effectiveness.
F24 exhibited efficacy in an in vivo
Drosophila model by rescuing eye phenotypes from degeneration caused by Aβ
toxicity. Further, computational studies were carried out to monitor
the interaction between F24 and Aβ1–42 aggregates.
The computational studies corroborated our in vitro and in vivo studies suggesting Aβ1–42 aggregation modulation ability of F24. The brain entry ability of
F24 was studied in the parallel artificial membrane permeability assay.
Finally, F24 was tested at doses of 1 and 2.5 mg/kg in the Morris
water maze AD model. The neuroprotective properties shown by F24 strongly
suggest that multifunctional features of this molecule provide symptomatic
relief and act as a disease-modifying agent in the treatment of AD.
The results from our experiments strongly indicated that natural template-based
F24 could serve as a lead molecule for further investigation to explore
multifunctional therapeutic agents for AD management.
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