17 research outputs found
Learning from the Past: Possible Urgent Prevention and Treatment Options for Severe Acute Respiratory Infections Caused by 2019-nCoV
With the current trajectory of the 2019-nCoV outbreak unknown, public
health and medicinal measures will both be needed to contain spreading of the
virus and to optimize patient outcomes. While little is known about the
virus, an examination of the genome sequence shows strong homology with its
more well-studied cousin, SARS-CoV. The spike protein used for host cell
infection shows key nonsynonymous mutations which may hamper efficacy of
previously developed therapeutics but remains a viable target for the
development of biologics and macrocyclic peptides. Other key drug targets,
including RdRp and 3CLpro, share a strikingly high (>95%) homology to
SARS-CoV. Herein, we suggest 4 potential drug candidates (an ACE2-based
peptide, remdesivir, 3CLpro-1 and a novel vinylsulfone protease inhibitor) that
can be used to treat patients suffering with the 2019-nCoV. We also summarize
previous efforts into drugging these targets and hope to help in the
development of broad spectrum anti-coronaviral agents for future epidemics
Expressed Protein Ligation Without Intein
Proteins with a
functionalized C-terminus such as a C-terminal thioester are key to the
synthesis of larger proteins via expressed protein ligation. They are usually
made by recombinant fusion to intein. Although powerful, the intein fusion
approach suffers from premature hydrolysis and low compatibility with denatured
conditions. To totally bypass the involvement of an enzyme for expressed
protein ligation, here we showed that a cysteine in a recombinant protein was
chemically activated by a small molecule cyanylating reagent at its N-side amide for undergoing nucleophilic
acyl substitution with amines including a number of L- and D-amino acids and
hydrazine. The afforded protein hydrazides could be used further for expressed
protein ligation. We demonstrated the versatility of this approach with the
successful synthesis of ubiquitin conjugates, ubiquitin-like protein
conjugates, histone H2A with a posttranslational modification, RNAse H that
actively hydrolyzed RNA, and exenatide that is a commercial therapeutic
peptide. The technique, which is exceedingly simple but highly useful, expands
to a great extent the synthetic capacity of protein chemistry and will
therefore make a large avenue of new research possible
KLF17 empowers TGF-β/Smad signaling by targeting Smad3-dependent pathway to suppress tumor growth and metastasis during cancer progression.
Inhibition of tumor suppressive signaling is linked to cancer progression, metastasis and epithelial-mesenchymal transition (EMT). Transforming growth factor-β1 (TGF-β)/Smad signaling plays an important role in tumor suppression. Kruppel-like-factor 17 (KLF17) is a negative regulator of metastasis and EMT. However, underlying mechanisms leading to tumor suppressive and anti-metastatic function of KLF17 still remains unknown. Here, we show that KLF17 plays an integral role in potentiating TGF-β/Smad signaling via Smad3-dependent pathway to suppress tumor progression. Intriguingly, TGF-β/Smad3 signaling induces KLF17 expression, generating a positive feedback loop. TGF-β/Smad3-KLF17 loop is critical for anti-metastasis and tumor inhibition in cancer cells. Mechanistically, silencing KLF17 reduced Smad3-DNA complex formation on Smad binding element (SBE) and affects the expression of TGF-β/Smad target genes. Moreover, KLF17 alters Smad3 binding pattern on chromatin. KLF17 regulates TGF-β target genes that are Smad3-dependent. Smad3 and KLF17 physically interact with each other via KLF17 responsive elements/SBE region. Intriguingly, TGF-β stimulates the recruitment of KLF17 on chromatin to subsets of metastasis-associated genes. Functionally, depletion of KLF17 enhanced tumorigenic features in cancer cells. KLF17 is critical for full cytostatic function of TGF-β/Smad signaling. Clinically, KLF17 expression significantly decreases during advance HCC. KLF17 shows positive correlation with Smad3 levels in cancer samples. Our data shows that enhance KLF17 activity has important therapeutic implications for targeted-therapies aimed at TGF-β/Smad3 pathway. These findings define novel mechanism by which TGF-β/Smad-KLF17 pathway mutually affect each other during cancer metastasis, provide a new model of regulation of TGF-β/Smad signaling by KLF17 and defines new insights into anti-metastatic function of KLF17
Repurposing Halicin as a potent covalent inhibitor for the SARS-CoV-2 main protease
The rapid spread of COVID-19 has caused a worldwide public health crisis. For prompt and effective development of antivirals for SARS-CoV-2, the pathogen of COVID-19, drug repurposing has been broadly conducted by targeting the main protease (MPro), a key enzyme responsible for the replication of virus inside the host. In this study, we evaluate the inhibition potency of a nitrothiazole-containing drug, halicin, and reveal its reaction and interaction mechanism with MPro. The in vitro potency test shows that halicin inhibits the activity of MPro an IC50 of 181.7 nM. Native mass spectrometry and X-ray crystallography studies clearly indicate that the nitrothiazole fragment of halicin covalently binds to the catalytic cysteine C145 of MPro. Interaction and conformational changes inside the active site of MPro suggest a favorable nucleophilic aromatic substitution reaction mechanism between MPro C145 and halicin, explaining the high inhibition potency of halicin towards MPro
Reversal of the Hofmeister Series: Specific Ion Effects on Peptides
Ion-specific
effects on salting-in and salting-out of proteins,
protein denaturation, as well as enzymatic activity are typically
rationalized in terms of the Hofmeister series. Here, we demonstrate
by means of NMR spectroscopy and molecular dynamics simulations that
the traditional explanation of the Hofmeister ordering of ions in
terms of their bulk hydration properties is inadequate. Using triglycine
as a model system, we show that the Hofmeister series for anions changes
from a direct to a reversed series upon uncapping the N-terminus.
Weakly hydrated anions, such as iodide and thiocyanate, interact with
the peptide bond, while strongly hydrated anions like sulfate are
repelled from it. In contrast, reversed order in interactions of anions
is observed at the positively charged, uncapped N-terminus, and by
analogy, this should also be the case at side chains of positively
charged amino acids. These results demonstrate that the specific chemical
and physical properties of peptides and proteins play a fundamental
role in ion-specific effects. The present study thus provides a molecular
rationalization of Hofmeister ordering for the anions. It also provides
a route for tuning these interactions by titration or mutation of
basic amino acid residues on the protein surface
A Quick Route to Multiple Highly Potent SARS-CoV-2 Main Protease Inhibitors*.
The COVID-19 pathogen, SARS-CoV-2, requires its main protease (SC2MPro ) to digest two of its translated long polypeptides to form a number of mature proteins that are essential for viral replication and pathogenesis. Inhibition of this vital proteolytic process is effective in preventing the virus from replicating in infected cells and therefore provides a potential COVID-19 treatment option. Guided by previous medicinal chemistry studies about SARS-CoV-1 main protease (SC1MPro ), we have designed and synthesized a series of SC2MPro inhibitors that contain β-(S-2-oxopyrrolidin-3-yl)-alaninal (Opal) for the formation of a reversible covalent bond with the SC2MPro active-site cysteine C145. All inhibitors display high potency with Ki values at or below 100 nM. The most potent compound, MPI3, has as a Ki value of 8.3 nM. Crystallographic analyses of SC2MPro bound to seven inhibitors indicated both formation of a covalent bond with C145 and structural rearrangement from the apoenzyme to accommodate the inhibitors. Virus inhibition assays revealed that several inhibitors have high potency in inhibiting the SARS-CoV-2-induced cytopathogenic effect in both Vero E6 and A549/ACE2 cells. Two inhibitors, MPI5 and MPI8, completely prevented the SARS-CoV-2-induced cytopathogenic effect in Vero E6 cells at 2.5-5 μM and A549/ACE2 cells at 0.16-0.31 μM. Their virus inhibition potency is much higher than that of some existing molecules that are under preclinical and clinical investigations for the treatment of COVID-19. Our study indicates that there is a large chemical space that needs to be explored for the development of SC2MPro inhibitors with ultra-high antiviral potency