a.
The trimeric spike (S) protein is a glycoprotein that mediates viral entry by binding to the host ACE2 receptor, is critical for SARS-CoV-2's ability to infect host cells, and is a target of neutralizing antibodies. Inhibition of the spike protein prevents viral attachment, halting infection at the earliest stage.
b.
The receptor binding domain is a specific region of the spike protein that binds ACE2 and is a major target of neutralizing antibodies. Focusing on the precise binding site allows highly specific disruption of viral attachment with reduced potential for off-target effects.
c.
The main protease or M
pro, also known as 3CL
pro or nsp5, is a cysteine protease that cleaves viral polyproteins into functional units needed for replication. Inhibiting M
pro disrupts the SARS-CoV-2 lifecycle within the host cell, preventing the creation of new copies.
d.
RNA-dependent RNA polymerase (RdRp), also called nsp12, is the core enzyme of the viral replicase-transcriptase complex that copies the positive-sense viral RNA genome into negative-sense templates for progeny RNA synthesis. Inhibiting RdRp blocks viral genome replication and transcription.
e.
The papain-like protease (PLpro) has multiple functions including cleaving viral polyproteins and suppressing the host immune response by deubiquitination and deISGylation of host proteins. Inhibiting PLpro may block viral replication and help restore normal immune responses.
f.
The angiotensin converting enzyme 2 (ACE2) protein is a host cell transmembrane protein that serves as the cellular receptor for the SARS-CoV-2 spike protein. ACE2 is expressed on many cell types, including epithelial cells in the lungs, and allows the virus to enter and infect host cells. Inhibition may affect ACE2's physiological function in blood pressure control.
g.
The nucleocapsid (N) protein binds and encapsulates the viral genome by coating the viral RNA. N enables formation and release of infectious virions and plays additional roles in viral replication and pathogenesis. N is also an immunodominant antigen used in diagnostic assays.
h.
Non-structural protein 10 (nsp10) serves as an RNA chaperone and stabilizes conformations of nsp12 and nsp14 in the replicase-transcriptase complex, which synthesizes new viral RNAs. Nsp10 disruption may destabilize replicase-transcriptase complex activity.
i.
The helicase, or nsp13, protein unwinds the double-stranded viral RNA, a crucial step in replication and transcription. Inhibition may prevent viral genome replication and the creation of new virus components.
j.
The interaction between the SARS-CoV-2 spike protein and the human ACE2 receptor is a primary method of viral entry, inhibiting this interaction can prevent the virus from attaching to and entering host cells, halting infection at an early stage.
k.
Transmembrane protease serine 2 (TMPRSS2) is a host cell protease that primes the spike protein, facilitating cellular entry. TMPRSS2 activity helps enable cleavage of the spike protein required for membrane fusion and virus entry. Inhibition may especially protect respiratory epithelial cells, buy may have physiological effects.
l.
Calu-3 is a human lung adenocarcinoma cell line with moderate ACE2 and TMPRSS2 expression and SARS-CoV-2 susceptibility. It provides a model of the human respiratory epithelium, but many not be ideal for modeling early stages of infection due to the moderate expression levels of ACE2 and TMPRSS2.
m.
A549 is a human lung carcinoma cell line with low ACE2 expression and SARS-CoV-2 susceptibility. Viral entry/replication can be studied but the cells may not replicate all aspects of lung infection.
n.
293T is a human embryonic kidney cell line that can be engineered for high ACE2 expression and SARS-CoV-2 susceptibility. 293T cells are easily transfected and support high protein expression.
o.
HEK293-hACE2 is a human embryonic kidney cell line with high ACE2 expression and SARS-CoV-2 susceptibility. Cells have been transfected with a plasmid to express the human ACE2 (hACE2) protein.
p.
293T/hACE2/TMPRSS2 is a human embryonic kidney cell line engineered for high ACE2 and TMPRSS2 expression, which mimics key aspects of human infection. 293T/hACE2/TMPRSS2 cells are very susceptible to SARS-CoV-2 infection.
q.
Vero E6 is an African green monkey kidney cell line with low/no ACE2 expression and high SARS-CoV-2 susceptibility. The cell line is easy to maintain and supports robust viral replication, however the monkey origin may not accurately represent human responses.
r.
SH-SY5Y is a human neuroblastoma cell line that exhibits neuronal phenotypes. It is commonly used as an in vitro model for studying neurotoxicity, neurodegenerative diseases, and neuronal differentiation.
