Prognostic impact of nectin-like molecule-5 (CD155) expression in non-small cell lung cancer.

BACKGROUND: CD155 is a transmembrane protein that inhibits antitumor immune response and represents a predictor of worse prognosis in non-small-cell lung cancer (NSCLC). However, it remains unexplored its association with clinical characteristics and genomic status of Latin American patients. This study characterizes the CD155 expression and its clinical implications in this population. METHODS: Tissue biopsies from 86 patients with locally-advanced or metastatic NSCLC were assessed for CD155 protein expression, ALK rearrangements and EGFR mutations. Cutoff values for high CD155 expression (CD155high) were determined from receiver operating characteristic (ROC) curves according to 2-year survival. It was evaluated its association with clinicopathological features, median progression-free survival (mPFS) and overall survival (mOS). RESULTS: the cutoff score for CD155high was 155 in the entire cohort and in patients without oncogenic alterations, and it was 110 in patients with oncogenic alterations. Eighty-four patients (97.7%) were CD155 positive, of which fifty-six (65.0%) had CD155high. EGFR L858R mutation related to lower CD155 IHC score than exon 19 deletion. Individuals with CD155high showed a shorter mOS (13.0 vs. 30.8 months; HR: 1.96 [95% CI, 1.15-3.35]; p = 0.014). Patients without oncogenic alterations having a CD155high displayed shorter mPFS (1.6 vs. 6.4 months, HR: 2.09 [95% CI, 1.06-4.20]; p = 0.034) and mOS (2.9 vs. 23.1 months; HR: 1.27 [95% CI, 1.07- 4.42]; p = 0.032). Patients with oncogenic alterations having CD155high only showed a trend to shorter mOS (26.3 vs. 52.0 months; HR: 2.39 [95% CI, 0.98-5.83]; p = 0.058). CONCLUSION: CD155high is a predictor of worse outcomes in patients with advanced NSCLC, predominantly among those without oncogenic alterations. CD155 could be a potential biomarker and a molecular target in patients with poor responses to current therapies.

The neonatal Fc receptor (FcRn) is a pan-arterivirus receptor.

Arteriviruses infect a variety of mammalian hosts, but the receptors used by these viruses to enter cells are poorly understood. We identified the neonatal Fc receptor (FcRn) as an important pro-viral host factor via comparative genome-wide CRISPR-knockout screens with multiple arteriviruses. Using a panel of cell lines and divergent arteriviruses, we demonstrate that FcRn is required for the entry step of arterivirus infection and serves as a molecular barrier to arterivirus cross-species infection. We also show that FcRn synergizes with another known arterivirus entry factor, CD163, to mediate arterivirus entry. Overexpression of FcRn and CD163 sensitizes non-permissive cells to infection and enables the culture of fastidious arteriviruses. Treatment of multiple cell lines with a pre-clinical anti-FcRn monoclonal antibody blocked infection and rescued cells from arterivirus-induced death. Altogether, this study identifies FcRn as a novel pan-arterivirus receptor, with implications for arterivirus emergence, cross-species infection, and host-directed pan-arterivirus countermeasure development.

The attachment factors and attachment receptors of human noroviruses.

Human noroviruses (HuNoVs) are the leading etiological agent causing the worldwide outbreaks of acute epidemic non-bacterial gastroenteritis. Histo-blood group antigens (HBGAs) are commonly acknowledged as cellular receptors or co-receptors for HuNoVs. However, certain genotypes of HuNoVs cannot bind with any HBGAs, suggesting potential additional co-factors and attachment receptors have not been identified yet. In addition, food items, such as oysters and lettuce, play an important role in the transmission of HuNoVs. In the past decade, a couple of attachment factors other than HBGAs have been identified and analyzed from foods and microbiomes. Attachment factors exhibit potential as inhibitors of viral binding to receptors on host cells. Therefore, it is imperative to further characterize the attachment factors for HuNoVs present in foods to effectively control the spread of HuNoVs within the food chain. This review summarizes the potential attachment factors/receptors of HuNoVs in humans, foods, and microbiome.

Dysregulation of FLVCR1a-dependent mitochondrial calcium handling in neural progenitors causes congenital hydrocephalus.

Congenital hydrocephalus (CH), occurring in approximately 1/1,000 live births, represents an important clinical challenge due to the limited knowledge of underlying molecular mechanisms. The discovery of novel CH genes is thus essential to shed light on the intricate processes responsible for ventricular dilatation in CH. Here, we identify FLVCR1 (feline leukemia virus subgroup C receptor 1) as a gene responsible for a severe form of CH in humans and mice. Mechanistically, our data reveal that the full-length isoform encoded by the FLVCR1 gene, FLVCR1a, interacts with the IP3R3-VDAC complex located on mitochondria-associated membranes (MAMs) that controls mitochondrial calcium handling. Loss of Flvcr1a in mouse neural progenitor cells (NPCs) affects mitochondrial calcium levels and energy metabolism, leading to defective cortical neurogenesis and brain ventricle enlargement. These data point to defective NPCs calcium handling and metabolic activity as one of the pathogenetic mechanisms driving CH.

Structural characteristics of BtKY72 RBD bound to bat ACE2 reveal multiple key residues affecting ACE2 usage of sarbecoviruses.

Two different sarbecoviruses, severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2, have caused serious challenges to public health. Certain sarbecoviruses utilize angiotensin-converting enzyme 2 (ACE2) as their cellular receptor, whereas some do not, speculatively due to the two deletions in their receptor-binding domain (RBD). However, it remains unclear whether sarbecoviruses with one deletion in the RBD can still bind to ACE2. Here, we showed that two phylogenetically related sarbecoviruses with one deletion, BtKY72 and BM48-31, displayed a different ACE2-usage range. The cryo-electron microscopy structure of BtKY72 RBD bound to bat ACE2 identified a key residue important for the interaction between RBD and ACE2. In addition, we demonstrated that the mutations involving four types of core residues enabled the sarbecoviruses with deletion(s) to bind to human ACE2 (hACE2) and broadened the ACE2 usage of SARS-CoV-2. Our findings help predict the potential hACE2-binding ability to emerge sarbecoviruses and develop pan-sarbecovirus therapeutic agents. IMPORTANCE: Many sarbecoviruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), possess the ability to bind to receptor angiotensin-converting enzyme 2 (ACE2) through their receptor-binding domain (RBD). However, certain sarbecoviruses with deletion(s) in the RBD lack this capability. In this study, we investigated two closely related short-deletion sarbecoviruses, BtKY72 and BM48-31, and revealed that BtKY72 exhibited a broader ACE2-binding spectrum compared to BM48-31. Structural analysis of the BtKY72 RBD-bat ACE2 complex identifies a critical residue at position 493 contributing to these differences. Furthermore, we demonstrated that the mutations involving four core residues in the RBD enabled the sarbecoviruses with deletion(s) to bind to human ACE2 and expanded the ACE2 usage spectra of SARS-CoV-2. These findings offer crucial insights for accurately predicting the potential threat of newly emerging sarbecoviruses to human health.

Increased PVR Expression on Bone Marrow Macrophages May Promote Resistance to TIGIT Blockade in Multiple Myeloma.

PURPOSE: TIGIT blockade in our ex vivo model of bone marrow (BM) reduced the number of malignant plasma cells (PC) in only half of patients with multiple myeloma. Here, we wanted to investigate whether increased expression of TIGIT ligands may inhibit T-cell immune response promoting resistance to TIGIT blockade. EXPERIMENTAL DESIGN: We first characterized the number and phenotype of BM macrophages in different stages of the disease by multiparameter flow cytometry. We assessed the effect of TIGIT ligands on PC survival by performing experiments in the ex vivo BM model and analyzed changes in gene expression by using NanoString technology and real-time PCR. RESULTS: The frequency of BM macrophages was significantly decreased in multiple myeloma, which was accompanied by changes in their immunophenotype. Moreover, we found a higher number of malignant PC in ex vivo BM cells cultured onto the poliovirus receptor (PVR) and nectin-2 compared with control, suggesting that both ligands may support PC survival. In addition, the presence of PVR, but not nectin-2, overcame the therapeutic effect of TIGIT blockade or exogenous IL2. Furthermore, exogenous IL2 increased TIGIT expression on both CD4+ and CD8+ T cells and, indirectly, PVR on BM macrophages. Consistently, PVR reduced the number of cytotoxic T cells and promoted a gene signature with reduced effector molecules. CONCLUSIONS: IL2 induced TIGIT on T cells in the BM, in which increased PVR expression resulted in cytotoxic T-cell inhibition, promoting PC survival and resistance to TIGIT blockade.

Molecular basis for receptor recognition and broad host tropism for merbecovirus MjHKU4r-CoV-1.

A novel pangolin-origin MERS-like coronavirus (CoV), MjHKU4r-CoV-1, was recently identified. It is closely related to bat HKU4-CoV, and is infectious in human organs and transgenic mice. MjHKU4r-CoV-1 uses the dipeptidyl peptidase 4 (DPP4 or CD26) receptor for virus entry and has a broad host tropism. However, the molecular mechanism of its receptor binding and determinants of host range are not yet clear. Herein, we determine the structure of the MjHKU4r-CoV-1 spike (S) protein receptor-binding domain (RBD) complexed with human CD26 (hCD26) to reveal the basis for its receptor binding. Measuring binding capacity toward multiple animal receptors for MjHKU4r-CoV-1, mutagenesis analyses, and homology modeling highlight that residue sites 291, 292, 294, 295, 336, and 344 of CD26 are the crucial host range determinants for MjHKU4r-CoV-1. These results broaden our understanding of this potentially high-risk virus and will help us prepare for possible outbreaks in the future.

Receptor binding and immunogenic properties of the receptor binding domain of influenza D virus hemagglutinin-esterase-fusion protein expressed from Escherichia coli.

The hemagglutinin-esterase-fusion (HEF) protein binds 9-O-acetylated sialic acids-containing glycans on the cell surface and drives influenza D virus (IDV) entry. The HEF is a primary determinant of the exceptional thermal and acid stability observed in IDV infection biology. Here, we expressed and purified the receptor binding domain (RBD) of the IDV HEF protein in Escherichia coli and characterized its receptor binding and antigenic properties. The data from these experiments indicate that (i) the RBD can bind with specificity to turkey red blood cells (RBC), and its binding can be specifically inhibited by IDV antibody; (ii) the RBD efficiently binds to the cell surface of MDCK cells expressing the receptor of IDV; and (iii) anti-RBD antibodies are capable of blocking RBD attachment to MDCK cells as well as of inhibiting the virus from agglutinating RBCs. These observations support the utility of this RBD in future receptor and entry studies of IDV.

Cancer cell plasticity defines response to immunotherapy in cutaneous squamous cell carcinoma.

Immune checkpoint blockade (ICB) approaches have changed the therapeutic landscape for many tumor types. However, half of cutaneous squamous cell carcinoma (cSCC) patients remain unresponsive or develop resistance. Here, we show that, during cSCC progression in male mice, cancer cells acquire epithelial/mesenchymal plasticity and change their immune checkpoint (IC) ligand profile according to their features, dictating the IC pathways involved in immune evasion. Epithelial cancer cells, through the PD-1/PD-L1 pathway, and mesenchymal cancer cells, through the CTLA-4/CD80 and TIGIT/CD155 pathways, differentially block antitumor immune responses and determine the response to ICB therapies. Accordingly, the anti-PD-L1/TIGIT combination is the most effective strategy for blocking the growth of cSCCs that contain both epithelial and mesenchymal cancer cells. The expression of E-cadherin/Vimentin/CD80/CD155 proteins in cSCC, HNSCC and melanoma patient samples predicts response to anti-PD-1/PD-L1 therapy. Collectively, our findings indicate that the selection of ICB therapies should take into account the epithelial/mesenchymal features of cancer cells.

Seasonal human coronaviruses OC43, 229E, and NL63 induce cell surface modulation of entry receptors and display host cell-specific viral replication kinetics.

The emergence of the COVID-19 pandemic prompted an increased interest in seasonal human coronaviruses. OC43, 229E, NL63, and HKU1 are endemic seasonal coronaviruses that cause the common cold and are associated with generally mild respiratory symptoms. In this study, we identified cell lines that exhibited cytopathic effects (CPE) upon infection by three of these coronaviruses and characterized their viral replication kinetics and the effect of infection on host surface receptor expression. We found that NL63 produced CPE in LLC-MK2 cells, while OC43 produced CPE in MRC-5, HCT-8, and WI-38 cell lines, while 229E produced CPE in MRC-5 and WI-38 by day 3 post-infection. We observed a sharp increase in nucleocapsid and spike viral RNA (vRNA) from day 3 to day 5 post-infection for all viruses; however, the abundance and the proportion of vRNA copies measured in the supernatants and cell lysates of infected cells varied considerably depending on the virus-host cell pair. Importantly, we observed modulation of coronavirus entry and attachment receptors upon infection. Infection with 229E and OC43 led to a downregulation of CD13 and GD3, respectively. In contrast, infection with NL63 and OC43 leads to an increase in ACE2 expression. Attempts to block entry of NL63 using either soluble ACE2 or anti-ACE2 monoclonal antibodies demonstrated the potential of these strategies to greatly reduce infection. Overall, our results enable a better understanding of seasonal coronaviruses infection kinetics in permissive cell lines and reveal entry receptor modulation that may have implications in facilitating co-infections with multiple coronaviruses in humans.IMPORTANCESeasonal human coronavirus is an important cause of the common cold associated with generally mild upper respiratory tract infections that can result in respiratory complications for some individuals. There are no vaccines available for these viruses, with only limited antiviral therapeutic options to treat the most severe cases. A better understanding of how these viruses interact with host cells is essential to identify new strategies to prevent infection-related complications. By analyzing viral replication kinetics in different permissive cell lines, we find that cell-dependent host factors influence how viral genes are expressed and virus particles released. We also analyzed entry receptor expression on infected cells and found that these can be up- or down-modulated depending on the infecting coronavirus. Our findings raise concerns over the possibility of infection enhancement upon co-infection by some coronaviruses, which may facilitate genetic recombination and the emergence of new variants and strains.

Changes in the chikungunya virus E1 glycoprotein domain II and hinge influence E2 conformation, infectivity, and virus-receptor interactions.

In a previous study to understand how the chikungunya virus (CHIKV) E1 glycoprotein ß-strand c functions, we identified several attenuating variants at E1 residue V80 and the emergence of second-site mutations in the fusion loop (E1-M88L) and hinge region (E1-N20Y) with the V80 variants in vivo. The emergence of these mutations led us to question how changes in E1 may contribute to CHIKV infection at the molecular level. Here, we use molecular dynamics to understand how changes in the E1 glycoprotein may influence the CHIKV glycoprotein E1-E2 complex. We found that E1 domain II variants lead to E2 conformational changes, allowing us to hypothesize that emerging variants E1-M88L and E1-N20Y could also change E2 conformation and function. We characterized CHIKV E1-M88L and E1-N20Y in vitro and in vivo to understand how these regions of the E1 glycoprotein contribute to host-specific infection. We found that CHIKV E1-N20Y enhanced infectivity in mosquito cells, while the CHIKV E1-M88L variant enhanced infectivity in both BHK-21 and C6/36 cells and led to changes in viral cholesterol-dependence. Moreover, we found that E1-M88L and E1-N20Y changed E2 conformation, heparin binding, and interactions with the receptor Mxra8. Interestingly, the CHIKV E1-M88L variant increased replication in Mxra8-deficient mice compared to WT CHIKV, yet was attenuated in mouse fibroblasts, suggesting that residue E1-M88 may function in a cell-type-dependent entry. Taken together, these studies show that key residues in the CHIKV E1 domain II and hinge region function through changes in E1-E2 dynamics to facilitate cell- and host-dependent entry.IMPORTANCEArboviruses are significant global public health threats, and their continued emergence around the world highlights the need to understand how these viruses replicate at the molecular level. The alphavirus glycoproteins are critical for virus entry in mosquitoes and mammals, yet how these proteins function is not completely understood. Therefore, it is critical to dissect how distinct glycoprotein domains function in vitro and in vivo to address these gaps in our knowledge. Here, we show that changes in the CHIKV E1 domain II and hinge alter E2 conformations leading to changes in virus-receptor and -glycosaminoglycan interactions and cell-specific infection. These results highlight that adaptive changes in E1 can have a major effect on virus attachment and entry, furthering our knowledge of how alphaviruses infect mammals and insects.

Influenza virus uses mGluR2 as an endocytic receptor to enter cells.

Influenza virus infection is initiated by the attachment of the viral haemagglutinin (HA) protein to sialic acid receptors on the host cell surface. Most virus particles enter cells through clathrin-mediated endocytosis (CME). However, it is unclear how viral binding signals are transmitted through the plasma membrane triggering CME. Here we found that metabotropic glutamate receptor subtype 2 (mGluR2) and potassium calcium-activated channel subfamily M alpha 1 (KCa1.1) are involved in the initiation and completion of CME of influenza virus using an siRNA screen approach. Influenza virus HA directly interacted with mGluR2 and used it as an endocytic receptor to initiate CME. mGluR2 interacted and activated KCa1.1, leading to polymerization of F-actin, maturation of clathrin-coated pits and completion of the CME of influenza virus. Importantly, mGluR2-knockout mice were significantly more resistant to different influenza subtypes than the wild type. Therefore, blocking HA and mGluR2 interaction could be a promising host-directed antiviral strategy.

Epistasis mediates the evolution of the receptor binding mode in recent human H3N2 hemagglutinin.

The receptor-binding site of influenza A virus hemagglutinin partially overlaps with major antigenic sites and constantly evolves. In this study, we observe that mutations G186D and D190N in the hemagglutinin receptor-binding site have coevolved in two recent human H3N2 clades. X-ray crystallography results show that these mutations coordinately drive the evolution of the hemagglutinin receptor binding mode. Epistasis between G186D and D190N is further demonstrated by glycan binding and thermostability analyses. Immunization and neutralization experiments using mouse and human samples indicate that the evolution of receptor binding mode is accompanied by a change in antigenicity. Besides, combinatorial mutagenesis reveals that G186D and D190N, along with other natural mutations in recent H3N2 strains, alter the compatibility with a common egg-adaptive mutation in seasonal influenza vaccines. Overall, our findings elucidate the role of epistasis in shaping the recent evolution of human H3N2 hemagglutinin and substantiate the high evolvability of its receptor-binding mode.

H19 influenza A virus exhibits species-specific MHC class II receptor usage.

Avian influenza A virus (IAV) surveillance in Northern California, USA, revealed unique IAV hemagglutinin (HA) genome sequences in cloacal swabs from lesser scaups. We found two closely related HA sequences in the same duck species in 2010 and 2013. Phylogenetic analyses suggest that both sequences belong to the recently discovered H19 subtype, which thus far has remained uncharacterized. We demonstrate that H19 does not bind the canonical IAV receptor sialic acid (Sia). Instead, H19 binds to the major histocompatibility complex class II (MHC class II), which facilitates viral entry. Unlike the broad MHC class II specificity of H17 and H18 from bat IAV, H19 exhibits a species-specific MHC class II usage that suggests a limited host range and zoonotic potential. Using cell lines overexpressing MHC class II, we rescued recombinant H19 IAV. We solved the H19 crystal structure and identified residues within the putative Sia receptor binding site (RBS) that impede Sia-dependent entry.

The H4 subtype of avian influenza virus: a review of its historical evolution, global distribution, adaptive mutations and receptor binding properties.

The H4 subtype of avian influenza virus (AIV) exhibits a wide host range and is commonly found in migratory waterfowl. Recent studies have revealed that the H4N6 AIV can infect guinea pigs via aerosol transmission without prior adaptation. Additionally, the Q226L/G228S substitutions in the receptor-binding site have led to structural changes in globular head of H4 AIV, resulting in a configuration similar to that of pandemic H2N2 and H3N2 human influenza viruses. This article provides an updated review of the historical evolution, global distribution, adaptive mutations, receptor-binding preferences, and host range of H4 AIV. The insights presented herein will help in assessing the potential risk of future H4 AIV epidemics.

Identification of residues in Lassa virus glycoprotein 1 involved in receptor switch.

Lassa virus (LASV) is an enveloped, negative-sense RNA virus that causes Lassa hemorrhagic fever. Successful entry of LASV requires the viral glycoprotein 1 (GP1) to undergo a receptor switch from its primary receptor alpha-dystroglycan (α-DG) to its endosomal receptor lysosome-associated membrane protein 1 (LAMP1). A conserved histidine triad in LASV GP1 has been reported to be responsible for receptor switch. To test the hypothesis that other non-conserved residues also contribute to receptor switch, we constructed a series of mutant LASV GP1 proteins and tested them for binding to LAMP1. Four residues, L84, K88, L107, and H170, were identified as critical for receptor switch. Substituting any of the four residues with the corresponding lymphocytic choriomeningitis virus (LCMV) residue (L84 â€‹N, K88E, L10F, and H170S) reduced the binding affinity of LASV GP1 for LAMP1. Moreover, all mutations caused decreases in glycoprotein precursor (GPC)-mediated membrane fusion at both pH 4.5 and 5.2. The infectivity of pseudotyped viruses bearing either GPCL84N or GPCK88E decreased sharply in multiple cell types, while L107F and H170S had only mild effects on infectivity. Using biolayer light interferometry assay, we found that all four mutants had decreased binding affinity to LAMP1, in the order of binding affinity being L84 â€‹N â€‹> â€‹L107F â€‹> â€‹K88E â€‹> â€‹H170S. The four amino acid loci identified for the first time in this study have important reference significance for the in-depth investigation of the mechanism of receptor switching and immune escape of LASV occurrence and the development of reserve anti-LASV infection drugs.

Pseudotyped virus infection of multiplexed ACE2 libraries reveals SARS-CoV-2 variant shifts in receptor usage.

Pairwise compatibility between virus and host proteins can dictate the outcome of infection. During transmission, both inter- and intraspecies variabilities in receptor protein sequences can impact cell susceptibility. Many viruses possess mutable viral entry proteins and the patterns of host compatibility can shift as the viral protein sequence changes. This combinatorial sequence space between virus and host is poorly understood, as traditional experimental approaches lack the throughput to simultaneously test all possible combinations of protein sequences. Here, we created a pseudotyped virus infection assay where a multiplexed target-cell library of host receptor variants can be assayed simultaneously using a DNA barcode sequencing readout. We applied this assay to test a panel of 30 ACE2 orthologs or human sequence mutants for infectability by the original SARS-CoV-2 spike protein or the Alpha, Beta, Gamma, Delta, and Omicron BA1 variant spikes. We compared these results to an analysis of the structural shifts that occurred for each variant spike's interface with human ACE2. Mutated residues were directly involved in the largest shifts, although there were also widespread indirect effects altering interface structure. The N501Y substitution in spike conferred a large structural shift for interaction with ACE2, which was partially recreated by indirect distal substitutions in Delta, which does not harbor N501Y. The structural shifts from N501Y greatly influenced the set of animal orthologs the variant spike was capable of interacting with. Out of the thirteen non-human orthologs, ten exhibited unique patterns of variant-specific compatibility, demonstrating that spike sequence changes during human transmission can toggle ACE2 compatibility and potential susceptibility of other animal species, and cumulatively increase overall compatibilities as new variants emerge. These experiments provide a blueprint for similar large-scale assessments of protein compatibility during entry by diverse viruses. This dataset demonstrates the complex compatibility relationships that occur between variable interacting host and virus proteins.

Untangling the Evolution of the Receptor-Binding Motif of SARS-CoV-2.

The spike protein determines the host-range specificity of coronaviruses. In particular, the Receptor-Binding Motif in the spike protein from SARS-CoV-2 contains the amino acids involved in molecular recognition of the host Angiotensin Converting Enzyme 2. Therefore, to understand how SARS-CoV-2 acquired its capacity to infect humans it is necessary to reconstruct the evolution of this important motif. Early during the pandemic, it was proposed that the SARS-CoV-2 Receptor-Binding Domain was acquired via recombination with a pangolin infecting coronavirus. This proposal was challenged by an alternative explanation that suggested that the Receptor-Binding Domain from SARS-CoV-2 did not originated via recombination with a coronavirus from a pangolin. Instead, this alternative hypothesis proposed that the Receptor-Binding Motif from the bat coronavirus RaTG13, was acquired via recombination with an unidentified coronavirus. And as a consequence of this event, the Receptor-Binding Domain from the pangolin coronavirus appeared as phylogenetically closer to SARS-CoV-2. Recently, the genomes from coronaviruses from Cambodia (bat_RShST182/200) and Laos (BANAL-20-52/103/247) which are closely related to SARS-CoV-2 were reported. However, no detailed analysis of the evolution of the Receptor-Binding Motif from these coronaviruses was reported. Here we revisit the evolution of the Receptor-Binding Domain and Motif in the light of the novel coronavirus genome sequences. Specifically, we wanted to test whether the above coronaviruses from Cambodia and Laos were the source of the Receptor-Binding Domain from RaTG13. We found that the Receptor-Binding Motif from these coronaviruses is phylogenetically closer to SARS-CoV-2 than to RaTG13. Therefore, the source of the Receptor-Binding Domain from RaTG13 is still unidentified. In accordance with previous studies, our results are consistent with the hypothesis that the Receptor-Binding Motif from SARS-CoV-2 evolved by vertical inheritance from a bat-infecting population of coronaviruses.

GateView: A Multi-Omics Platform for Gene Feature Analysis of Virus Receptors within Human Normal Tissues and Tumors.

Viruses are obligate intracellular parasites that rely on cell surface receptor molecules to complete the first step of invading host cells. The experimental method for virus receptor screening is time-consuming, and receptor molecules have been identified for less than half of known viruses. This study collected known human viruses and their receptor molecules. Through bioinformatics analysis, common characteristics of virus receptor molecules (including sequence, expression, mutation, etc.) were obtained to study why these membrane proteins are more likely to become virus receptors. An in-depth analysis of the cataloged virus receptors revealed several noteworthy findings. Compared to other membrane proteins, human virus receptors generally exhibited higher expression levels and lower sequence conservation. These receptors were found in multiple tissues, with certain tissues and cell types displaying significantly higher expression levels. While most receptor molecules showed noticeable age-related variations in expression across different tissues, only a limited number of them exhibited gender-related differences in specific tissues. Interestingly, in contrast to normal tissues, virus receptors showed significant dysregulation in various types of tumors, particularly those associated with dsRNA and retrovirus receptors. Finally, GateView, a multi-omics platform, was established to analyze the gene features of virus receptors in human normal tissues and tumors. Serving as a valuable resource, it enables the exploration of common patterns among virus receptors and the investigation of virus tropism across different tissues, population preferences, virus pathogenicity, and oncolytic virus mechanisms.

Export of heme by the feline leukemia virus C receptor regulates mitochondrial biogenesis and redox balance in the hematophagous insect Rhodnius prolixus.

Heme is a prosthetic group of proteins involved in vital physiological processes. It participates, for example, in redox reactions crucial for cell metabolism due to the variable oxidation state of its central iron atom. However, excessive heme can be cytotoxic due to its prooxidant properties. Therefore, the control of intracellular heme levels ensures the survival of organisms, especially those that deal with high concentrations of heme during their lives, such as hematophagous insects. The export of heme initially attributed to the feline leukemia virus C receptor (FLVCR) has recently been called into question, following the discovery of choline uptake by the same receptor in mammals. Here, we found that RpFLVCR is a heme exporter in the midgut of the hematophagous insect Rhodnius prolixus, a vector for Chagas disease. Silencing RpFLVCR decreased hemolymphatic heme levels and increased the levels of intracellular dicysteinyl-biliverdin, indicating heme retention inside midgut cells. FLVCR silencing led to increased expression of heme oxygenase (HO), ferritin, and mitoferrin mRNAs while downregulating the iron importers Malvolio 1 and 2. In contrast, HO gene silencing increased FLVCR and Malvolio expression and downregulated ferritin, revealing crosstalk between heme degradation/export and iron transport/storage pathways. Furthermore, RpFLVCR silencing strongly increased oxidant production and lipid peroxidation, reduced cytochrome c oxidase activity, and activated mitochondrial biogenesis, effects not observed in RpHO-silenced insects. These data support FLVCR function as a heme exporter, playing a pivotal role in heme/iron metabolism and maintenance of redox balance, especially in an organism adapted to face extremely high concentrations of heme.