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Downstream sequences influence the choice between a naturally occurring noncanonical and closely positioned upstream canonical heptameric fusion motif during bovine coronavirus subgenomic mRNA synthesis.

Mechanisms leading to subgenomic mRNA (sgmRNA) synthesis in coronaviruses are poorly understood but are known to involve a heptameric signaling motif, originally called the intergenic sequence. The intergenic sequence is the presumed crossover region (fusion site) for RNA-dependent RNA polymerase (RdRp) during discontinuous transcription, a process leading to sgmRNAs that are both 5' and 3' coterminal. In the bovine coronavirus, the major fusion site for synthesis of mRNA 5 (GGUAGAC) does not conform to the canonical motif (UC[U,C]AAAC) at three positions (underlined), yet it lies just 14 nucleotides downstream from such a sequence (UCCAAAC). The infrequently used canonical sequence, by computer prediction, is buried within the stem of a stable hairpin (-17.2 kcal/mol). Here we document the existence of this stem by enzyme probing and examine its influence and that of neighboring sequences on the unusual choice of fusion sites by analyzing transcripts made in vivo from mutated defective interfering RNA constructs. We learned that (i) mutations that were predicted to unfold the stem-loop in various ways did not switch RdRp crossover to the upstream canonical site, (ii) a totally nonconforming downstream motif resulted in no measurable transcription from either site, (iii) the canonical upstream site does not function ectopically to lend competence to the downstream noncanonical site, and (iv) altering flanking sequences downstream of the downstream noncanonical motif in ways that diminish sequence similarity with the virus genome 5' end caused a dramatic switch to the upstream canonical site. These results show that sequence elements downstream of the noncanonical site can dramatically influence the choice of fusion sites for synthesis of mRNA 5 and are interpreted as being most consistent with a mechanism of similarity-assisted RdRp strand switching during minus-strand synthesis.

Animals↗

Secondary structure of the 3' terminus of hepatitis C virus minus-strand RNA.

The 3'-terminal ends of both the positive and negative strands of the hepatitis C virus (HCV) RNA, the latter being the replicative intermediate, are most likely the initiation sites for replication by the viral RNA-dependent RNA polymerase, NS5B. The structural features of the very conserved 3' plus [(+)] strand untranslated region [3' (+) UTR] are well established (K. J. Blight and C. M. Rice, J. Virol. 71:7345-7352, 1997). However, little information is available concerning the 3' end of the minus [(-)] strand RNA. In the present work, we used chemical and enzymatic probing to investigate the conformation of that region, which is complementary to the 5' (+) UTR and the first 74 nucleotides of the HCV polyprotein coding sequence. By combining our experimental data with computer predictions, we have derived a secondary-structure model of this region. In our model, the last 220 nucleotides, where initiation of the (+) strand RNA synthesis presumably takes place, fold into five stable stem-loops, forming domain I. Domain I is linked to an overall less stable structure, named domain II, containing the sequences complementary to the pseudoknot of the internal ribosomal entry site in the 5' (+) UTR. Our results show that, even though the (-) strand 3'-terminal region has the antisense sequence of the 5' (+) UTR, it does not fold into its mirror image. Interestingly, comparison of the replication initiation sites on both strands reveals common structural features that may play key functions in the replication process.

Base Sequence↗

Topology of the membrane-associated hepatitis C virus protein NS4B.

Hepatitis C virus (HCV) belongs to the Hepacivirus genus in the Flaviviridae family. Among the least known viral proteins in this family is the nonstructural protein NS4B, which has been suggested to be a part of the replication complex. Hydrophobicity plots indicate a common profile among the NS4B proteins from different members of the Flaviviridae family, suggesting a common function. In order to gain a deeper understanding of the nature of HCV NS4B, we have determined localization and topology of this protein by using recombinant HCV NS4B constructs. The protein localized to the endoplasmic reticulum (ER), but also induced a pattern of cytoplasmic foci positive for markers of the ER. Computer predictions of the membrane topology of NS4B suggested that it has four transmembrane segments. The N and C termini were anticipated to be localized in the cytoplasm, because they are processed by the cytoplasmic NS3 protein. By introducing glycosylation sites at various positions in HCV NS4B, we show that the C terminus is cytoplasmic and the loop around residue 161 is lumenal as predicted. Surprisingly, the N-terminal tail was translocated into the lumen in a considerable fraction of the NS4B molecules, most likely by a posttranslational process. Interestingly, NS4B proteins of the yellow fever and dengue viruses also have their N termini located in the ER lumen due to an N-terminal signal peptide not found in NS4B of HCV. A shared topology achieved in two different ways supports the notion of a common function for NS4B in FLAVIVIRIDAE:

Cell Membrane↗

Potential selection of LMP1 variants in nasopharyngeal carcinoma.

Seven distinct sequence variants of the Epstein-Barr virus latent membrane protein 1 (LMP1) have been identified by distinguishing amino acid changes in the carboxy-terminal domain. In this study the transmembrane domains are shown to segregate identically with the distinct carboxy-terminal amino acid sequences. Since strains of LMP1 have been shown to differ in abundance between blood and throat washes, nasopharyngeal carcinomas (NPCs) from areas of endemicity and nonendemicity with matching blood were analyzed by using a heteroduplex tracking assay to distinguish LMP1 variants. Striking differences were found between the compartments with the Ch1 strain prevalent in the NPCs from areas of endemicity and nonendemicity and the B958 strain prevalent in the blood of the endemic samples, whereas multiple strains of LMP1 were prevalent in the blood of the nonendemic samples. The possible selection against the B958 strain appearing in the tumor was highly significant (P < 0.0001). Sequence analysis of the full-length LMP1 variants revealed changes in many of the known and computer-predicted HLA-restricted epitopes with changes in key positions in multiple, potential epitopes for the specific HLA of the patients. These amino acid substitutions at key positions in the LMP1 epitopes may result in a reduced cytotoxic-T-lymphocyte response. These data indicate that strains with specific variants of LMP1 are more likely to be found in NPC. The predominance of specific LMP1 variants in NPC could reflect differences in the biologic or molecular properties of the distinct forms of LMP1 or possible immune selection.

Amino Acid Sequence↗

Differentiation-induced internal translation of c-sis mRNA: analysis of the cis elements and their differentiation-linked binding to the hnRNP C protein.

In previous reports we showed that the long 5' untranslated region (5' UTR) of c-sis, the gene encoding the B chain of platelet-derived growth factor, has translational modulating activity due to its differentiation-activated internal ribosomal entry site (D-IRES). Here we show that the 5' UTR contains three regions with a computer-predicted Y-shaped structure upstream of an AUG codon, each of which can confer some degree of internal translation by itself. In nondifferentiated cells, the entire 5' UTR is required for maximal basal IRES activity. The elements required for the differentiation-sensing ability (i.e., D-IRES) were mapped to a 630-nucleotide fragment within the central portion of the 5' UTR. Even though the region responsible for IRES activation is smaller, the full-length 5' UTR is capable of mediating the maximal translation efficiency in differentiated cells, since only the entire 5' UTR is able to confer the maximal basal IRES activity. Interestingly, a 43-kDa protein, identified as hnRNP C, binds in a differentiation-induced manner to the differentiation-sensing region. Using UV cross-linking experiments, we show that while hnRNP C is mainly a nuclear protein, its binding activity to the D-IRES is mostly nuclear in nondifferentiated cells, whereas in differentiated cells such binding activity is associated with the ribosomal fraction. Since the c-sis 5' UTR is a translational modulator in response to cellular changes, it seems that the large number of cross-talking structural entities and the interactions with regulated trans-acting factors are important for the strength of modulation in response to cellular changes. These characteristics may constitute the major difference between strong IRESs, such as those seen in some viruses, and IRESs that serve as translational modulators in response to developmental signals, such as that of c-sis.

5' Untranslated Regions↗

Automatic annotation of genomic regulatory sequences by searching for composite clusters.

A new method was developed for revealing of composite clusters of cis-elements in promoters of eukaryotic genes that are functionally related or coexpressed. A software system "ClusterScan" have been created that enables: (i) to train system on representative samples of promoters to reveal cis-elements that tend to cluster, (ii) to train system on a number of samples of functionally related promoters to identify functionally coupled transcription factors; (iii) to provide tools for searching of this clusters in genomic sequences to identify and functionally characterize regulatory regions in genome. A number of training samples of different functional and structural groups of promoters were analysed. Search for composite clusters in human chromosomes 21 and 22 reveals a number of interesting examples. Finally, a decision tree system was constructed to classify promoters of several functionally related gene groups. The decision tree system enables to identify new promoters and computationally predict their possible function.

Animals↗

Kinetics of CO2 excretion and intravascular pH disequilibria during carbonic anhydrase inhibition.

Inhibition of carbonic anhydrase (CA) activity (activity in red blood cells and activity available on capillary endothelium) results in decrements in CO2 excretion (VCO2) and plasma-erythrocyte CO2-HCO(-3)-H+ disequilibrium as blood travels around the circulation. To investigate the kinetics of changes in blood PCO2 and pH during progressive CA inhibition, we used our previously detailed mathematical model of capillary gas exchange to analyze experimental data of VCO2 and blood-gas/pH parameters obtained from anesthetized, paralyzed, and mechanically ventilated dogs after treatment with acetazolamide (Actz, 0-100 mg/kg i.v.). Arterial and mixed venous blood samples were collected via indwelling femoral and pulmonary arterial catheters, respectively. Cardiac output was measured by thermodilution. End-tidal PCO2, as a measure of alveolar PCO2, was obtained from continuous records of airway PCO2 above the carina. Experimental results were analyzed with the aid of a mathematical model of lung and tissue-gas exchange. Progressive CA inhibition was associated with stepwise increments in the equilibrated mixed venous-alveolar PCO2 gradient (9, 19, and 26 Torr at 5, 20, and 100 mg/kg Actz, respectively). The maximum decrements in VCO2 were 10, 24, and 26% with 5, 20, and 100 mg/kg Actz, respectively, without full recovery of VCO2 at 1 h postinfusion. Equilibrated arterial PCO2 overestimated alveolar PCO2, and tissue PCO2 was underestimated by the measured equilibrated mixed venous blood PCO2. Mathematical model computations predicted hysteresis loops of the instantaneous CO2-HCO(-3)-H+ relationship and in vivo blood PCO2-pH relationship due to the finite reaction times for CO2-HCO(-3)-H+ reactions. The shape of the hysteresis loops was affected by the extent of Actz inhibition of CA in red blood cells and plasma.

Acetazolamide↗

Interactions between membrane conductances underlying thalamocortical slow-wave oscillations.

Neurons of the central nervous system display a broad spectrum of intrinsic electrophysiological properties that are absent in the traditional "integrate-and-fire" model. A network of neurons with these properties interacting through synaptic receptors with many time scales can produce complex patterns of activity that cannot be intuitively predicted. Computational methods, tightly linked to experimental data, provide insights into the dynamics of neural networks. We review this approach for the case of bursting neurons of the thalamus, with a focus on thalamic and thalamocortical slow-wave oscillations. At the single-cell level, intrinsic bursting or oscillations can be explained by interactions between calcium- and voltage-dependent channels. At the network level, the genesis of oscillations, their initiation, propagation, termination, and large-scale synchrony can be explained by interactions between neurons with a variety of intrinsic cellular properties through different types of synaptic receptors. These interactions can be altered by neuromodulators, which can dramatically shift the large-scale behavior of the network, and can also be disrupted in many ways, resulting in pathological patterns of activity, such as seizures. We suggest a coherent framework that accounts for a large body of experimental data at the ion-channel, single-cell, and network levels. This framework suggests physiological roles for the highly synchronized oscillations of slow-wave sleep.

Action Potentials↗

Disease-stage variance in functional CD4(+) T-cell responses against novel pan-human leukocyte antigen-D region presented human papillomavirus-16 E7 epitopes.

Given the anticipated clinical importance of helper and regulatory CD4(+) T cells reactive against human papillomavirus-16 E7 in the cervical carcinoma setting, we performed this study to identify novel E7-derived T helper (Th) epitopes and to characterize functional anti-E7 Th responses in normal donors and patients with cervical intraepithelial neoplasia I-III or cervical cancer. Candidate pan-HLA-DR (D region) binding peptides were identified and synthesized based on results obtained using a predictive computer algorithm, then applied in short-term in vitro T-cell sensitization assays. Using IFN-gamma/IL-5 (interleukin 5) enzyme-linked immunospot assays as readouts for Th1-type and Th2-type CD4(+) T-cell responses, respectively, we identified three E7-derived T helper epitopes (E7(1-12), E7(48-62), and E7(62-75)), two of which are novel. Normal donor CD4(+) T cells failed to react against these E7 peptides, whereas patients with premalignant cervical intraepithelial neoplasia I-III lesions displayed preferential Th1-type responses against all three E7 epitopes. Th1-type responses were still observed to the E7(48-62) but not to the E7(1-12) and E7(62-75) peptides in cancer patients, where these latter two epitopes evoked Th2-type responses. Notably all responders to the E7(1-12) and E7(62-75) peptides expressed the HLA-DR4 or -DR15 alleles, whereas all responders to the E7(48-62) peptide failed to express the HLA-DR4 allele. Our results are consistent with a model in which cervical cancer progression is linked to an undesirable Th1- to Th2-type shift in functional CD4(+) T cell responses to two novel E7-derived epitopes. These peptides may prove important in vaccines to promote and maintain protective Th1-type antihuman papillomavirus immunity and in the immune monitoring of treated patients harboring HPV-16(+) malignancies.

Adult↗

Important animal allergens are lipocalin proteins: why are they allergenic?

Major respiratory allergens of dogs, mice, rats, horses and cows belong to the lipocalin group of proteins. The sequence identity of lipocalins is often less than 20%, but they contain between one and three structurally conserved regions and their three-dimensional structures are similar. Lipocalins share common biological functions, predominantly related to the transport of small hydrophobic molecules, such as vitamins and pheromones. Immune reactivity to lipocalin allergens is not well known. In Bos d 5, the IgE-binding epitopes are spread along the molecule, whereas in Bos d 2, the C terminus appears to contain the human B cell epitopes. Bos d 5 contains several murine T cell epitopes. No information is available on human T cell epitopes. The maximal number of epitopes an allergic patient's T cells could recognize in Bos d 2 was five. Three of the epitopes were colocalized in the structurally conserved regions of lipocalins. Interestingly, one of the epitopes was recognized by the T cells of all patients and the computer predictions suggested that there would be an epitope in the corresponding parts of human endogenous lipocalins. The proliferative responses of peripheral blood mononuclear cells of Bos d 2-allergic subjects to Bos d 2 were weak. The T cell response was Th2-dominated. To explain these observations, we have proposed that the allergenicity of lipocalins may be a consequence of molecular mimicry between lipocalin allergens and endogenous lipocalins at the T cell level.

Allergens↗

Ferritin mRNA translation, structure, and gene transcription during development of animals and plants.

Changes in transcription/accumulation of ferritin mRNA accompany cell differentiation and development as cells establish the pattern of iron storage and metabolism that matches their specialized features. Signals which induce changes in ferritin gene expression include hormones (thyrotropin in thyroid cells), monokines (tumor necrosis factor alpha in myoblasts, and preadipocytes), phagocytosis and/or inducing agents (erythrophagocytosis in macrophages, phorbol esters in promyelocytes, and dimethyslulfoxide in proerythroblasts), heat shock (in red cells) and light (in leaf mesophyll). Iron, which has a major effect on the translation of ferritin mRNA, also leads to synthesis and/or accumulation of ferritin mRNA in hepatocytes, adult red cells, HeLa cells, and undifferentiated plant cells. Iron-induced changes in ferritin mRNA composition allow cells to synthesize large amounts of different ferritins in response to excess iron. Whether iron will act both on translation and transcription may relate to the uses of stored iron by the cell (iron reserve for other cells? detoxification?) and the magnitude of the iron signal relative to the existing pool of ferritin mRNA. Translational regulation of ferritin mRNA depends on two distinctive features of the RNA: (1) conserved regulatory sequence of 28 nucleotides occurs in the 5' noncoding region (iron 'regulatory' or 'responsive' element, IRE) which interacts with cytoplasmic regulator proteins, present in animal cells, that block initiation; sequences in the 3' untranslated region can modulate translation when the IRE is present. (2) Ferritin mRNA, either deregulated by iron induction in cells or isolated from cells (polyA+), forms initiation complexes efficiently compared to other cellular mRNAs. The structure of the IRE, which is also found in the 3' untranslated region of the iron-destabilized transferrin receptor mRNA, has begun to be analyzed by computer prediction, site-directed mutagenesis, and solution behavior. The results to date show that the IRE is a hairpin with bulges and loops that is stacked upon a base-paired flanking region (FL) with varying sequence. Interactions of the IRE+FL with other parts of ferritin mRNA are indicated by comparing the reactivity of natural ferritin mRNA with an oligomer (n = 55). The structure of the stem nearest the hairpin loop is sequence-dependent and flexible. Variations in the distance of the IRE from the cap in various ferritin mRNAs, compensated by the length of FL, and the structural properties of the IRE+FL suggest that the 5' regulatory structure of ferritin mRNA includes the IRE+FL.

Animals↗

Unveiling the Molecular Secrets of Seaweeds: A Comprehensive Review of Bioinformatics Applications in Algal Research.

Recent advances in high-throughput sequencing, bioinformatics, and multi-omics technologies have transformed seaweed research by overcoming long-standing challenges associated with complex genomes, diverse life cycles, and limited genomic resources. This review provides a comprehensive overview of bioinformatics approaches used to investigate seaweed genomics, transcriptomics, proteomics, metabolomics, microbiomes, and functional genomics, with emphasis on the computational tools and databases that support these analyses. Applications of bioinformatics in phylogenetics, drug discovery, microbiome characterization, and the development of biofuels, nutraceuticals, pharmaceuticals, and sustainable agriculture are also discussed. Particular attention is given to emerging strategies involving multi-omics integration, genome editing, artificial intelligence, machine learning, and synthetic biology that are reshaping seaweed research. The review further examines current challenges, including incomplete genomic resources, data standardization, and the need for experimental validation of computational predictions. Collectively, these advances highlight the growing role of bioinformatics in enabling systems-level understanding of seaweed biology and accelerating their translation into sustainable biotechnological and marine bioeconomy applications.

macroalgal genomics↗

Phospho.ELM: a database of experimentally verified phosphorylation sites in eukaryotic proteins.

BACKGROUND: Post-translational phosphorylation is one of the most common protein modifications. Phosphoserine, threonine and tyrosine residues play critical roles in the regulation of many cellular processes. The fast growing number of research reports on protein phosphorylation points to a general need for an accurate database dedicated to phosphorylation to provide easily retrievable information on phosphoproteins. DESCRIPTION: Phospho.ELM http://phospho.elm.eu.org is a new resource containing experimentally verified phosphorylation sites manually curated from the literature and is developed as part of the ELM (Eukaryotic Linear Motif) resource. Phospho.ELM constitutes the largest searchable collection of phosphorylation sites available to the research community. The Phospho.ELM entries store information about substrate proteins with the exact positions of residues known to be phosphorylated by cellular kinases. Additional annotation includes literature references, subcellular compartment, tissue distribution, and information about the signaling pathways involved as well as links to the molecular interaction database MINT. Phospho.ELM version 2.0 contains 1703 phosphorylation site instances for 556 phosphorylated proteins. CONCLUSION: Phospho.ELM will be a valuable tool both for molecular biologists working on protein phosphorylation sites and for bioinformaticians developing computational predictions on the specificity of phosphorylation reactions.

Animals↗

Flexible promoter architecture requirements for coactivator recruitment.

BACKGROUND: The spatial organization of transcription factor binding sites in regulatory DNA, and the composition of intersite sequences, influences the assembly of the multiprotein complexes that regulate RNA polymerase recruitment and thereby affects transcription. We have developed a genetic approach to investigate how reporter gene transcription is affected by varying the spacing between transcription factor binding sites. We characterized the components of promoter architecture that govern the yeast transcription factors Cbf1 and Met31/32, which bind independently, but collaboratively recruit the coactivator Met4. RESULTS: A Cbf1 binding site was required upstream of a Met31/32 binding site for full reporter gene expression. Distance constraints on coactivator recruitment were more flexible than those for cooperatively binding transcription factors. Distances from 18 to 50 bp between binding sites support efficient recruitment of Met4, with only slight modulation by helical phasing. Intriguingly, we found that certain sequences located between the binding sites abolished gene expression. CONCLUSION: These results yield insight to the influence of both binding site architecture and local DNA flexibility on gene expression, and can be used to refine computational predictions of gene expression from promoter sequences. In addition, our approach can be applied to survey promoter architecture requirements for arbitrary combinations of transcription factor binding sites.

Basic Helix-Loop-Helix Leucine Zipper Transcriptio↗

Multiplatform genome-wide identification and modeling of functional human estrogen receptor binding sites.

BACKGROUND: Transcription factor binding sites (TFBS) impart specificity to cellular transcriptional responses and have largely been defined by consensus motifs derived from a handful of validated sites. The low specificity of the computational predictions of TFBSs has been attributed to ubiquity of the motifs and the relaxed sequence requirements for binding. We posited that the inadequacy is due to limited input of empirically verified sites, and demonstrated a multiplatform approach to constructing a robust model. RESULTS: Using the TFBS for the estrogen receptor (ER)alpha (estrogen response element [ERE]) as a model system, we extracted EREs from multiple molecular and genomic platforms whose binding to ERalpha has been experimentally confirmed or rejected. In silico analyses revealed significant sequence information flanking the standard binding consensus, discriminating ERE-like sequences that bind ERalpha from those that are nonbinders. We extended the ERE consensus by three bases, bearing a terminal G at the third position 3' and an initiator C at the third position 5', which were further validated using surface plasmon resonance spectroscopy. Our functional human ERE prediction algorithm (h-ERE) outperformed existing predictive algorithms and produced fewer than 5% false negatives upon experimental validation. CONCLUSION: Building upon a larger experimentally validated ERE set, the h-ERE algorithm is able to demarcate better the universe of ERE-like sequences that are potential ER binders. Only 14% of the predicted optimal binding sites were utilized under the experimental conditions employed, pointing to other selective criteria not related to EREs. Other factors, in addition to primary nucleotide sequence, will ultimately determine binding site selection.

Algorithms↗

Thyroid-stimulating hormone receptor mediates peripheral-central neuroimmune crosstalk in autoimmune thyroid diseases.

BACKGROUND: Organ-specific autoimmune diseases, particularly Graves' disease (GD) and its extrathyroidal manifestation, Graves' orbitopathy (GO), are characterized by systemic autoimmunity that may extend its impact to the central nervous system (CNS). While thyroid-stimulating hormone receptor (TSHR) is the primary driver of pathological remodeling in the thyroid and orbital tissues, emerging evidence suggests it is also expressed in the brain and may participate in neuroimmune signaling. However, the molecular mechanisms linking peripheral TSHR-driven autoimmunity to these extended systemic features remain unclear. Thus, GD and GO provide a unique window to investigate how peripheral autoantibodies influence CNS involvement as part of its broader pathological spectrum. METHODS: Genome-wide association studies (GWAS) and post-GWAS analyses were integrated with bulk RNA sequencing, single-cell and spatial transcriptomics, and brain imaging phenotypes to comprehensively characterize peripheral and central alterations in GD and GO. Mendelian randomization was applied to test causal relationships between genetic variants and brain signatures. Structural biology analyses were further conducted including protein-protein docking, small-molecule docking, and normal mode dynamics to identify prospective modulators of TSHR. Immunofluorescence staining was performed in a GO mouse model to validate the colocalization of potential interacted proteins in the specific brain region. RESULTS: Brain imaging-derived phenotypes (IDPs) alterations in GO and GO were systematically analyzed to identify neuroanatomical and functional alterations. TSHR was further identified as a shared genetic driver across peripheral and central compartments. TSHR was expressed in spiny projection neurons, microglia, and peripheral T cells, with cell-cell communication analyses highlighting TSHR-mediated interactions among neurons, endothelial cells, and microglia. Immunofluorescence staining in a GO mouse model confirmed the colocalization of TSHR with FN1 and GNAS in the basal ganglia, providing tissue-level validation of the computationally predicted ligand-receptor interactions. Immune profiling further showed immune alterations in GD and GO. Structural modeling supported plausible physical interfaces between TSHR and interacting proteins, and small-molecule screening identified three repurposable compounds - venetoclax, irinotecan, and dutasteride - with predicted favorable docking scores and stable binding poses in our simulations. CONCLUSIONS: These findings demonstrate that TSHR acts as a molecular hub mediating peripheral-central neuroimmune crosstalk in GD and GO. The results support a broader "disease-molecule axis" framework that links genetic susceptibility with multi-level immune and neural mechanisms. This work provides mechanistic insights relevant to the development of TSHR-targeted therapies, with implications for both peripheral immune modulation and central regulation. However, the limited sample size, lack of longitudinal follow-up, and absence of in vivo validation warrant cautious interpretation and further investigation.

Receptors, Thyrotropin↗

Rare damaging CCR2 variants are associated with lower lifetime cardiovascular risk.

BACKGROUND: Previous work has shown a role of CCL2, a key chemokine governing monocyte trafficking, in atherosclerosis. However, it remains unknown whether targeting CCR2, the cognate receptor of CCL2, provides protection against human atherosclerotic cardiovascular disease. METHODS: Computationally predicted damaging or loss-of-function (REVEL&#x2009;>&#x2009;0.5) variants within CCR2 were detected in whole-exome-sequencing data from 454,775 UK Biobank participants and tested for association with cardiovascular endpoints in gene-burden tests. Given the key role of CCR2 in monocyte mobilization, variants associated with lower monocyte count were prioritized for experimental validation. The response to CCL2 of human cells transfected with these variants was tested in migration and cAMP assays. Validated damaging variants were tested for association with cardiovascular endpoints, atherosclerosis burden, and vascular risk factors. Significant associations were replicated in six independent datasets (n&#x2009;=&#x2009;1,062,595). RESULTS: Carriers of 45 predicted damaging or loss-of-function CCR2 variants (n&#x2009;=&#x2009;787 individuals) were at lower risk of myocardial infarction and coronary artery disease. One of these variants (M249K, n&#x2009;=&#x2009;585, 0.15% of European ancestry individuals) was associated with lower monocyte count and with both decreased downstream signaling and chemoattraction in response to CCL2. While M249K showed no association with conventional vascular risk factors, it was consistently associated with a lower risk of myocardial infarction (odds ratio [OR]: 0.66, 95% confidence interval [CI]: 0.54-0.81, p&#x2009;=&#x2009;6.1&#x2009;&#xd7;&#x2009;10-5) and coronary artery disease (OR: 0.74, 95%CI: 0.63-0.87, p&#x2009;=&#x2009;2.9&#x2009;&#xd7;&#x2009;10-4) in the UK Biobank and in six replication cohorts. In a phenome-wide association study, there was no evidence of a higher risk of infections among M249K carriers. CONCLUSIONS: Carriers of an experimentally confirmed damaging CCR2 variant are at a lower lifetime risk of myocardial infarction and coronary artery disease without carrying a higher risk of infections. Our findings provide genetic support for the translational potential of CCR2-targeting as an atheroprotective approach.

Humans↗

Ligands on the string: single-molecule AFM studies on the interaction of antibodies and substrates with the Na+-glucose co-transporter SGLT1 in living cells.

Atomic force microscopy (AFM) was used to probe topology, conformational changes and initial substrate-carrier interactions of Na+-glucose co-transporter (SGLT1) in living cells on a single-molecule level. By scanning SGLT1-transfected Chinese hamster ovary (CHO) cells with AFM tips carrying an epitope-specific antibody directed against the extramembranous C-terminal loop 13, significant recognition events could be detected. Specificity was confirmed by the absence of events in nontransfected CHO cells and by the use of free antigen and free antibody superfusion. Thus, contrary to computer predictions on SGLT1 topology, loop 13 seems to be part of the extracellular surface of the transporter. Binding probability of the antibody decreased upon addition of phlorizin, a specific inhibitor of SGLT1, suggesting a considerable conformational change of loop 13 when the inhibitor occludes the sugar translocation pathway. Using an AFM tip carrying 1-thio-D-glucose, direct evidence could be obtained that in the presence of Na+ a sugar-binding site appears on the transporter surface. The binding site accepts the sugar residue of the glucoside phlorizin, free D-glucose, and D-galactose, but not free L-glucose and probably represents the first of several selectivity filters of the transporter. This work demonstrates the potential of AFM to study the presence and dynamics of plasma membrane transporters in intact cells on the single molecule level.

Animals↗