Biology subjects

Chan, M.

Publications and source records attributed to Chan, M..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

TBK1 and IKKϵ protect target cells from IFNγ-mediated T cell killing via an inflammatory apoptotic mechanism

Cytotoxic T cells produce interferon gamma (IFN{gamma}), which plays a critical role in anti-microbial and anti-tumor responses. However, it is not clear whether T cell-derived IFN{gamma} directly kills infected and tumor target cells, and how this may be regulated. Here, we report that target cell expression of the kinases TBK1 and IKK{varepsilon} regulate IFN{gamma} cytotoxicity by suppressing the ability of T cell-derived IFN{gamma} to kill target cells. In tumor targets lacking TBK1 and IKK{varepsilon}, IFN{gamma} induces expression of TNFR1 and the Z-nucleic acid sensor, ZBP1, to trigger RIPK1-dependent apoptosis, largely in a target cell-autonomous manner. Unexpectedly, IFN{gamma}, which is not known to signal to NF{kappa}B, induces hyperactivation of NF{kappa}B in TBK1 and IKK{varepsilon} double-deficient cells. TBK1 and IKK{varepsilon} suppress IKK/{beta} activity and in their absence, IFN{gamma} induces elevated NF{kappa}B-dependent expression of inflammatory chemokines and cytokines. Apoptosis is thought to be non-inflammatory, but our observations demonstrate that IFN{gamma} can induce an inflammatory form of apoptosis, and this is suppressed by TBK1 and IKK{varepsilon}. The two kinases provide a critical connection between innate and adaptive immunological responses by regulating three key responses: (1) phosphorylation of IRF3/7 to induce type I IFN; (2) inhibition of RIPK1-dependent death; and (3) inhibition of NF{kappa}B-dependent inflammation. We propose that these kinases evolved these functions such that their inhibition by pathogens attempting to block type I IFN expression would enable IFN{gamma} to trigger apoptosis accompanied by an alternative inflammatory response. Our findings show that loss of TBK1 and IKK{varepsilon} in target cells sensitizes them to inflammatory apoptosis induced by T cell-derived IFN{gamma}. Short SummaryIn the absence of TBK1 and IKK{varepsilon}, target cells are killed by T cells in an IFN{gamma}-dependent manner. In TBK1 and IKK{varepsilon}-deficient cells, IFN{gamma} induces RIPK1-dependent death, as well as hyper-induction of NF{kappa}B-dependent inflammatory genes. This suggests that any inhibition of TBK1/IKK{varepsilon} to block type I IFN expression will result in the demise of the cell accompanied by an alternate inflammatory program. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/606693v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1606b75org.highwire.dtl.DTLVardef@12eebc0org.highwire.dtl.DTLVardef@177c033org.highwire.dtl.DTLVardef@eb5819_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

Gut Microbiome Perturbation Affected Conjugative Transfer of Antimicrobial Resistance Genes

The global spread of antimicrobial resistance genes (ARGs) poses a significant threat to public health. While antibiotics effectively treat bacterial infections, they can also induce gut dysbiosis, the severity of which varies depending on the specific antibiotic treatment used. However, it remains unclear how gut dysbiosis affects the mobility and dynamics of ARGs. To address this, mice were pre-treated with streptomycin, ampicillin, or sulfamethazine, and then orally inoculated with Salmonella enterica serovar Typhimurium and S. Heidelberg carrying a multi-drug resistance IncA/C plasmid. The streptomycin pre- treatment caused severe microbiome perturbation, promoting high-density colonization of S. Heidelberg and S. Typhimurium, and enabling IncA/C transfer from S. Heidelberg to S. Typhimurium and a commensal Escherichia coli. The ampicillin pre-treatment induced moderate microbiome perturbation, supporting only S. Heidelberg colonization and IncA/C transfer to commensal E. coli. The sulfamethazine pre-treatment led to mild microbiome perturbation, favoring neither Salmonella spp. colonization nor conjugative plasmid transfer. The degree of gut dysbiosis also influenced the enrichment or depletion of ARGs associated with mobile plasmids or core commensal bacteria, respectively. These findings underscore the significance of pre-existing gut dysbiosis induced by various antibiotic treatments on ARG dissemination and may inform prudent antibiotic use practices.

microbiology↗

bioRxiv2024

Integrative Co-Registration of Elemental Imag-ing and Histopathology for Enhanced Spatial Multimodal Analysis of Tissue Sections through TRACE

SummaryElemental imaging provides detailed profiling of metal bioaccumulation, offering more precision than bulk analysis by targeting specific tissue areas. However, accurately identifying comparable tissue regions from elemental maps is challenging, requiring the integration of hematoxylin and eosin (H&E) slides for effective comparison. Facilitating the streamlined co-registration of Whole Slide Images (WSI) and elemental maps, TRACE enhances the analysis of tissue regions and elemental abundance in various pathological conditions. Through an interactive containerized web application, TRACE features real-time annotation editing, advanced statistical tools, and data export, supporting comprehensive spatial analysis. Notably, it allows for comparison of elemental abundances across annotated tissue structures and enables integration with other spatial data types through WSI co-registration. Availability and ImplementationAvailable on the following platforms- GitHub: jlevy44/trace_app, PyPI: trace_app, Docker: joshualevy44/trace_app, Singularity: joshualevy44/trace_app. Contactjoshua.levy@cshs.org Supplementary informationSupplementary data are available.

bioinformatics↗

bioRxiv2023

Pulmonary Ventilation Analysis Using 1H Ultra-Short Echo Time (UTE) Lung MRI: A Reproducibility Study

PurposeTo evaluate methods for quantification of pulmonary ventilation with ultrashort echo time (UTE) MRI. MethodsWe performed a reproducibility study, acquiring two free-breathing 1H UTE lung MRIs on the same day for six healthy volunteers. The 1) 3D + t cyclic b-spline and 2) symmetric image normalization (SyN) methods for image registration were applied after respiratory phase-resolved image reconstruction. Ventilation maps were calculated using 1) Jacobian determinant of the deformation fields minus one, termed regional ventilation, and 2) intensity percentage difference between the registered and fixed image, termed specific ventilation. We compared the reproducibility of all four method combinations via statistical analysis. ResultsSplit violin plots and Bland-Altman plots are shown for whole lungs and lung sections. The cyclic b-spline registration and Jacobian determinant regional ventilation quantification provide total ventilation volumes that match the segmentation tidal volume, smooth and uniform ventilation maps. The cyclic b-spline registration and specific ventilation combination yields the smallest standard deviation in the Bland-Altman plot. ConclusionCyclic registration performs better than SyN for respiratory phase-resolved 1H UTE MRI ventilation quantification. Regional ventilation correlates better with segmentation lung volume, while specific ventilation is more reproducible.

bioengineering↗

bioRxiv2023

KinCytE- a Kinase to Cytokine Explorer to Identify Molecular Regulators and Potential Therapeutic Opportunities

Cytokines and chemokines are secreted proteins that regulate various biological processes, such as inflammation, immune response, and cell differentiation. Therefore, disruption of signaling pathways involving these proteins has been linked to a range of diseases, including cancer. However, targeting individual cytokines, chemokines, or their receptors is challenging due to their regulatory redundancy and incomplete understanding of their signaling networks. To transform these difficult-to-drug targets into a pharmacologically manageable class, we developed a web-based platform called KinCytE. This platform was designed to link the effects of kinase inhibitors, a well-established class of drugs, with cytokine and chemokine release and signaling networks. The resulting KinCytE platform enables users to investigate protein kinases that regulate specific cytokines or chemokines, generate a ranked list of FDA-approved kinase inhibitors that affect cytokine/chemokine activity, and explore and visualize cytokine signaling network thus facilitating drugging this challenging target class. KinCytE is freely accessible via https://atlas.fredhutch.org/kincyte.

systems biology↗

bioRxiv2023

Deficits in neural encoding of speech in preterm infants

Preterm children show developmental cognitive and language deficits that can be subtle and sometimes undetectable until later in life. Studies of brain development in children who are born preterm have largely focused on vascular and gross anatomical characteristics rather than pathophysiological processes that may contribute to these developmental deficits. Neural encoding of speech as reflected in EEG recordings is predictive of future language development and could provide insights into those pathophysiological processes. We recorded EEG from 45 preterm ([≤] 34 weeks of gestation) and 45 full-term ([≥] 38 weeks) Chinese-learning infants 0 to 12 months of (corrected) age during natural sleep. Each child listened to three speech stimuli that differed in lexically meaningful pitch (2 native and 1 non-native speech categories). EEG measures associated with synchronization and gross power of the frequency following response (FFR) were examined. ANCOVAs revealed no main effect of stimulus nativeness but main effects of age, consistent with earlier studies. A main effect of prematurity also emerged, with synchronization measures showing stronger group differences than power. By detailing differences in FFR measures related to synchronization and power, this study brings us closer to identifying the pathophysiological pathway to often subtle language problems experienced by preterm children.

neuroscience↗

bioRxiv2023

CDK7 is a Novel Therapeutic Vulnerability in Fibrolamellar Carcinoma

Fibrolamellar carcinoma (FLC) is a rare and lethal cancer that afflicts young individuals. The tumor arises in the background of a healthy liver, and patients typically present with advanced cancer at the time of diagnosis. Unfortunately, for these patients with advanced or recurrent cancer, no proven systemic therapies exist resulting in only 30-45% of patients surviving to 5 years. Investigations into the molecular underpinning of FLC have revealed a unique gene fusion between heat shock protein 40 (DNAJB1) and the catalytic subunit alpha of protein kinase A (PRKACA), leading to the formation of an oncoprotein (DNAJ-PKAc) that retains kinase activity and is a proven tumor-causing event in FLC. To uncover potential therapeutic targets, we engineered an FLC cell line by introducing the DNAJB1-PRKACA oncogene rearrangement into human hepatocellular cells using CRISPR/Cas9. We identified aberrant cell cycle progression, and follow-up molecular analysis revealed evidence of enhanced cyclin dependent kinase 7 (CDK7) activation in the DNAJB1-PRKACA expressing FLC cells. These findings were confirmed in human samples of FLC. In turn, targeting CDK7 with selective inhibitors demonstrated efficacy in several patient-derived models of FLC, with minimal toxicity to normal liver. Collectively, this work uncovers a novel candidate therapeutic vulnerability in FLC.

cancer biology↗

bioRxiv2023

A generic binding pocket for small molecule IKs activators at the extracellular inter-subunit interface of KCNQ1 and KCNE1 channel complexes

The cardiac IKs ion channel comprises KCNQ1, calmodulin, and KCNE1 in a dodecameric complex which provides a repolarizing current reserve at higher heart rates and protects from arrhythmia syndromes that cause fainting and sudden death. Pharmacological activators of IKs are therefore of interest both scientifically and therapeutically for treatment of IKs loss-of-function disorders. One group of chemical activators are only active in the presence of the accessory KCNE1 subunit and here we investigate this phenomenon using molecular modeling techniques and mutagenesis scanning in mammalian cells. A generalized activator binding pocket is formed extracellularly by KCNE1, the domain-swapped S1 helices of one KCNQ1 subunit and the pore/turret region made up of two other KCNQ1 subunits. A few residues, including K41, A44 and Y46 in KCNE1, W323 in the KCNQ1 pore, and Y148 in the KCNQ1 S1 domain, appear critical for the binding of structurally diverse molecules, but in addition, molecular modeling studies suggest that induced fit by structurally different molecules underlies the generalized nature of the binding pocket. Activation of IKs is enhanced by stabilization of the KCNQ1-S1/KCNE1/pore complex, which ultimately slows deactivation of the current, and promotes outward current summation at higher pulse rates. Our results provide a mechanistic explanation of enhanced IKscurrents by these activator compounds and provide a map for future design of more potent therapeutically useful molecules.

pharmacology and toxicology↗

bioRxiv2022

The rVSV-EBOV vaccine provides limited cross-protection against Sudan virus in guinea pigs

Recombinant vesicular stomatitis viruses (rVSVs) engineered to express heterologous viral glycoproteins have proven to be remarkably effective vaccines. Indeed, rVSV-EBOV, which expresses the Ebola virus (EBOV) glycoprotein, recently received clinical approval in the United States and Europe for its ability to prevent EBOV disease. Analogous rVSV vaccines expressing the glycoproteins of different human-pathogenic filoviruses have also been developed and shown to be effective in pre-clinical evaluations, yet these vaccine candidates have not progressed far beyond research laboratories. As the current outbreak of Sudan virus (SUDV) intensifies in Uganda, the need for proven countermeasures is rendered even more acute. Here we demonstrate that an rVSV-based vaccine expressing the SUDV glycoprotein (rVSV-SUDV) generates a potent humoral immune response that completely protects guinea pigs from SUDV disease and death. Although the cross-protection generated by rVSV vaccines for different filoviruses is thought to be limited, we wondered whether rVSV-EBOV might also provide protection against SUDV, which is closely related to EBOV. Surprisingly, nearly 60% of guinea pigs that were vaccinated with rVSV-EBOV and challenged with SUDV survived, suggesting that rVSV-EBOV offers limited protection against SUDV, at least in the guinea pig model. These results were confirmed by a back-challenge experiment in which animals that had been vaccinated with rVSV-EBOV and survived EBOV challenge were inoculated with SUDV and survived. Whether these data are applicable to the efficacy of rVSV-EBOV in humans is unknown, and they should therefore be interpreted cautiously. Nevertheless, this study confirms the potency of the rVSV-SUDV vaccine, and it highlights the potential for rVSV-EBOV to elicit a cross-protective immune response.

microbiology↗

bioRxiv2022

Sphingosine kinases promote Ebola virus infection and can be targeted to inhibit filoviruses, coronaviruses, and arenaviruses using late endocytic trafficking to enter cells

Entry of enveloped viruses in host cells requires the fusion of the viral and host cell membranes, a process that is facilitated by viral fusion proteins protruding from the viral envelope. For fusion, viral fusion proteins need to be triggered by host factors and for some viruses, such as Ebola virus (EBOV) and Lassa fever virus, this event occurs inside endosomes and/or lysosomes. Consequently, these late-penetrating viruses must be internalized and delivered to entry-conducive intracellular vesicles. Because endocytosis and vesicular trafficking are tightly regulated cellular processes, late penetrating viruses also depend on specific host factors, such as signaling molecules, for efficient viral delivery to the site of fusion, suggesting that these could be targeted for antiviral therapy. In this study, we investigated a role for sphingosine kinases (SKs) in viral entry and found that chemical inhibition of sphingosine kinase 1 (SK1) and/or SK2 and knockdown of SK1 or SK2, inhibited entry of EBOV into host cells. Mechanistically, inhibition of SK1 and/or SK2 prevented EBOV from reaching late-endosomes and lysosomes that are positive for the EBOV receptor, Niemann Pick C1 (NPC1). Furthermore, we present evidence that suggests the trafficking defect caused by SK1/2 inhibition occurs independently of S1P signaling through cell-surface S1PRs. Lastly, we found that chemical inhibition of SKs prevents entry of other late-penetrating viruses, including arenaviruses and coronaviruses, in addition to inhibiting infection by replication competent EBOV and SARS-CoV-2 in Huh7.5 cells. In sum, our results highlight an important role played by SKs in endocytic trafficking which can be targeted to inhibit entry of late-penetrating viruses. SK inhibitors could serve as a starting point for the development of broad-spectrum antiviral therapeutics.

microbiology↗

bioRxiv2022

The Effects of N-linked Glycosylation on SLC6 Transporters

Membrane transporters of the solute carrier 6 (SLC6) family mediate various physiological processes by facilitating the translocation of amino acids, neurotransmitters, and other metabolites. In the human body, these transporters are tightly controlled through various post-translational modifications with implications on protein expression, stability, membrane trafficking, and dynamics. While N-linked glycosylation is a universal regulatory mechanism among eukaryotes, the exact molecular mechanism of how glycosylation affects the SLC6 transporter family. It is generally believed that glycans influence transporter stability and membrane trafficking, however, the role of glycosylation on transporter dynamics remains inconsistent, with differing conclusions among individual transporters across the SLC6 family. In this study, we collected over 1 millisecond of aggregated all-atom molecular dynamics (MD) simulation data to identify the impact of N-glycans of four human SLC6 transporters: the serotonin transporter, dopamine transporter, glycine transporter, and neutral amino acid transporter B0AT1. We designed our computational study by first simulating all possible combination of a glycan attached to each glycosylation sites followed by investigating the effect of larger, oligo-N-linked glycans to each transporter. Our simulations reveal that glycosylation does not significantly affect transporter structure, but alters the dynamics of the glycosylated extracellular loop. The structural consequences of glycosylation on the loop dynamics are further emphasized in the presence of larger glycan molecules. However, no apparent trend in ligand stability or movement of gating helices was observed. In all, the simulations suggest that glycosylation does not consistently affect transporter structure and dynamics among the collective SLC6 family and should be characterized at a per-transporter level to further elucidate the underlining mechanisms of in vivo regulation.

biophysics↗

bioRxiv2022

Trans-interaction of risk loci 6p24.1 and 10q11.21 is associated with endothelial damage in coronary artery disease

Background and AimsSingle nucleotide polymorphism rs6903956 has been identified as one of the genetic risk factors for coronary artery disease (CAD). However, rs6903956 lies in a non-coding locus on chromosome 6p24.1. We aim to interrogate the molecular basis of 6p24.1 containing rs6903956 risk alleles in endothelial disease biology. Methods and ResultsWe generated induced pluripotent stem cells (iPSCs) from CAD patients (AA risk genotype at rs6903956) and normal controls (GG non-risk genotype at rs6903956). CRIPSR-Cas9-based deletions ({Delta}63-89bp) on 6p24.1, including both rs6903956 and a short tandem repeat variant rs140361069 in linkage disequilibrium, were performed to generate isogenic iPSC-derived endothelial cells. Edited CAD endothelial cells, with removal of A risk alleles, exhibited a global transcriptional downregulation of pathways relating to abnormal vascular physiology and activated endothelial processes. A CXC chemokine ligand on chromosome 10q11.21, CXCL12, was uncovered as a potential effector gene in CAD endothelial cells. Underlying this effect was the preferential inter-chromosomal interaction of 6p24.1 risk locus to a weak promoter of CXCL12, confirmed by chromatin conformation capture assays on our iPSC-derived endothelial cells. Functionally, risk genotypes AA/ AG at rs6903956 were associated significantly with elevated levels of circulating damaged endothelial cells in CAD patients. Circulating endothelial cells isolated from patients with risk genotypes AA/ AG were also found to have 10 folds higher CXCL12 transcript copies/ cell than those with non-risk genotype GG. ConclusionOur study reveals the trans-acting impact of 6p24.1 with another CAD locus on 10q11.21 and is associated with intensified endothelial injury.

molecular biology↗

bioRxiv2022

An S1 subunit vaccine and combination adjuvant (COVAC-1) elicits robust protection against SARS-CoV-2 challenge in African green monkeys

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent responsible for the ongoing global pandemic. With over 500 million cases and more than 6 million deaths reported globally, the need for access to effective vaccines is clear. An ideal SARS-CoV-2 vaccine will prevent pathology in the lungs and prevent virus replication in the upper respiratory tract, thus reducing transmission. Here, we assessed the efficacy of an adjuvanted SARS-CoV-2 S1 subunit vaccine, called COVAC-1, in an African green monkey (AGM) model. AGMs immunized and boosted with COVAC-1 were protected from SARS-CoV-2 challenge compared to unvaccinated controls based on reduced pathology and reduced viral RNA levels and infectious virus in the respiratory tract. Both neutralizing antibodies and antibodies capable of mediating antibody-dependent cell-mediated cytotoxicity (ADCC) were observed in vaccinated animals prior to the challenge. COVAC-1 induced effective protection, including in the upper respiratory tract, thus supporting further development and utility for determining the mechanism that confers this protection. AUTHOR SUMMARYVaccines that can prevent the onward transmission of SARS-CoV-2 and prevent disease are highly desirable. Whether this can be accomplished without mucosal immunization by a parenterally administered subunit vaccine is not well established. Here we demonstrate that following two vaccinations, a protein subunit vaccine containing the S1 portion of the SARS-CoV-2 spike glycoprotein and the novel adjuvant TriAdj significantly reduces the amount of virus in the lungs and also mediates rapid clearance of the virus from the upper respiratory tract. Further support of the effectiveness of COVAC-1 was the observation of reduced pathology in the lungs and viral RNA being largely absent from tissues, blood, and rectal swabs. Thus COVAC-1 appears promising at mediating protection in both the upper and lower respiratory tract and may be capable of reducing subsequent transmission of SARS-CoV-2. Further investigation into the mechanism of protection in the upper respiratory tract and the initial immune response that supports this would be warranted.

microbiology↗

bioRxiv2022

Molecular Mechanism of Substrate Transport and Dynamics of the Cyanobacterial Bicarbonate Transporter BicA

Cyanobacteria are responsible for up to 80% of aquatic carbon dioxide fixation and have evolved specialized carbon concentrating mechanism to increase photosynthetic yield. As such, cyanobacteria are attractive targets for synthetic biology and engineering approaches to address the demands of global energy security, food production, and climate change for an increasing worlds population. The bicarbonate transporter BicA is a sodium-dependent, low-affinity, high-flux bicarbonate symporter expressed in the plasma membrane of cyanobacteria. Despite extensive biochemical characterization of BicA, including the resolution of the BicA crystal structure, the dynamic understanding of the bicarbonate transport mechanism remains elusive. To this end, we have collected over 1 ms of all-atom molecular dynamics simulation data of the BicA dimer to elucidate the structural rearrangements involved in the substrate transport process. We further characterized the energetics of the cooperativity between BicA protomers and investigated potential mutations that are shown to decrease the free energy barrier of conformational transitions. In all, our study illuminates a detailed mechanistic understanding of the conformational dynamics of bicarbonate transporters and provide atomistic insights to engineering these transporters for enhanced photosynthetic production.

biophysics↗

bioRxiv2022

Olverembatinib inhibits SARS-CoV-2-Omicron variant-mediated cytokine release

The Omicron variant has become dominant in the U.S. and around the world. This variant is found to be 2-fold more infectious than the Delta variant, posing a significant threat of severe cases and death. We and others have recently reported that the N-terminus domain (NTD) of the SARS-CoV-2 of various variants is responsible for inducing cytokine release in human PBMCs. Here, we demonstrate that the NTD of the Omicron variant remains highly effective at inducing cytokine release in human PBMCs. Furthermore, we show that Ponatinib and a novel compound, Olverembatinib, are potent Omicron NTD-mediated cytokine release inhibitors. Target profiling revealed that Olverembatinib blocks most of the previously identified kinases responsible for cytokine release. Together, we propose that Ponatinib and Olverembatinib may represent an attractive therapeutic option for treating moderate to severe COVID-19 cases. HIGHLIGHTSO_LIThe N-terminus domain (NTD) of the SARS-CoV-2 Omicron variant strongly induces multiple inflammatory molecules in PBMCs, unaffected by the mutations observed in the NTD. C_LIO_LIThe cytokine release mediated by the Omicron variant is comparable to the Delta variant. C_LIO_LIOlverembatinib, a clinical-stage multi-kinase inhibitor, potently inhibits Omicron NTD-mediated cytokine release. C_LIO_LIOlverembatinib could relieve severe symptoms associated with COVID-19 Omicron and Delta variants. C_LI

immunology↗

bioRxiv2021

Machine learning guided design of high affinity ACE2 decoys for SARS-CoV-2 neutralization

A potential therapeutic candidate for neutralizing SARS-CoV-2 infection is engineering high-affinity soluble ACE2 decoy proteins to compete for binding of the viral spike (S) protein. Previously, a deep mutational scan of ACE2 was performed and has led to the identification of a triple mutant ACE2 variant, named ACE22.v.2.4, that exhibits nanomolar affinity binding to the RBD domain of S. Using a recently developed transfer learning algorithm, TLmutation, we sought to identified other ACE2 variants, namely double mutants, that may exhibit similar binding affinity with decreased mutational load. Upon training a TLmutation model on the effects of single mutations, we identified several ACE2 double mutants that bind to RBD with tighter affinity as compared to the wild type, most notably, L79V;N90D that binds RBD with similar affinity to ACE22.v.2.4. The successful experimental validation of the double mutants demonstrated the use transfer and supervised learning approaches for engineering protein-protein interactions and identifying high affinity ACE2 peptides for targeting SARS-CoV-2.

biophysics↗

bioRxiv2021

Engineered High-Affinity ACE2 Peptide Mitigates ARDS and Death Induced by Multiple SARS-CoV-2 Variants

Vaccine hesitancy and continuing emergence of SARS-CoV-2 variants of concern that may escape vaccine-induced immune responses highlight the urgent need for effective COVID-19 therapeutics. Monoclonal antibodies used in the clinic have varying efficacies against distinct SARS-CoV-2 variants; thus, there is considerable interest in engineered ACE2 peptides with augmented binding affinities for SARS-CoV-2 Spike protein. These could have therapeutic benefit against multiple viral variants. Using molecular dynamics simulations, we show how three amino acid substitutions in an engineered soluble ACE2 peptide (sACE22.v2.4-IgG1) markedly increase affinity for the SARS-CoV-2 Spike (S) protein. We demonstrate high binding affinity to S protein of the early SARS-CoV-2 WA-1/2020 isolate and also to multiple variants of concern: B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), and B.1.617.2 (Delta) SARS-CoV-2 variants. In humanized K18-hACE2 mice, prophylactic and therapeutic administration of sACE22.v2.4-IgG1 peptide prevented acute lung vascular endothelial injury and lung edema (essential features of ARDS) and significantly improved survival after infection by SARS-CoV-2 WA-1/2020 as well as P.1 variant of concern. These studies demonstrate for the first time broad efficacy in vivo of an ACE2 decoy peptide against multiple SARS-CoV-2 variants and point to its therapeutic potential.

pharmacology and toxicology↗

bioRxiv2021

Structural rearrangement of the intracellular gate of the serotonin transporter induced by Thr276 phosphorylation

The reuptake of the neurotransmitter serotonin from the synaptic cleft by the serotonin transporter, SERT, is essential for proper neurological signaling. Biochemical studies have shown Thr276 of transmembrane helix 5 is a site of PKG-mediated SERT phosphorylation, which has been proposed to shifts the SERT conformational equlibira to promote inward-facing states, thus enhancing 5HT transport. Recent structural and simulation studies have provided insights into the conformation transitions during substrate transport but have not shed light on SERT regulation via post-translational modifications. Using molecular dynamics simulations and Markov state models, we investigate how Thr276 phosphorylation impacts the SERT mechanism and its role in enhancing transporter stability and function. Our simulations show that Thr276 phosphorylation alters the hydrogen-bonding network involving residues on transmembrane helix 5. This in turn decreases the free energy barriers for SERT to transition to the inward-facing state, thus facilitating 5HT transport. The results provide atomistic insights into in vivo SERT regulation and can be extended to other pharmacologically important transporters in the solute carrier superfamily.

biophysics↗