A Human Platelet Receptor Protein Microarray Identifies the High Affinity Immunoglobulin E Receptor Subunit α (FcεR1α) as an Activating Platelet Endothelium Aggregation Receptor 1 (PEAR1) Ligand

Extracellular matrix protein 1 binds to connective tissue growth factor against liver fibrosis and ductular reaction

BACKGROUND

Extracellular matrix protein 1 (ECM1) can inhibit TGFβ activation, but its antifibrotic action remains largely unknown. This study aims to investigate ECM1 function and its physical interaction with the profibrotic connective tissue growth factor (CTGF) in fibrosis and ductular reaction (DR).

METHODS

Ecm1 knockouts or animals that ectopically expressed this gene were subjected to induction of liver fibrosis and DR by feeding 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) or α-naphthyl-isothiocyanate (ANIT). ECM1 and CTGF were also examined in the livers of patients with alcohol-associated liver disease (ALD) or ethanol-exposed animals that were fed the western diet for 4 months in the WDA model with liver pathology resembing ALD in patients.

RESULTS

ECM1 bound to CTGF in yeast two-hybrid systems, cultured liver cells, and cholestatic livers damaged by DDC or α-naphthyl-isothiocyanate. This interaction blocked integrin αvβ6-mediated TGFβ activation, thereby reducing fibrotic responses in vitro. ECM1 downregulation was associated with biliary CTGF induction during human ALD progression. In experimental models, Ecm1 loss enhanced susceptibility to DDC-induced cholestasis with upregulation of Ctgf, αvβ6, alpha-smooth muscle actin, procollagen type I, serum transaminase, and total bilirubin levels in germline knockouts, whereas forced expression of this gene significantly attenuated DR and biliary fibrosis after the feeding of DDC or α-naphthyl-isothiocyanate containing diets. Moreover, ectopic Ecm1 inhibited not only alcohol-associated fibrosis but also TGFβ-mediated deregulation of hepatocyte nuclear factor 4α, preventing the production of the fetal p2 promoter-driven isoforms in the WDA model.

CONCLUSIONS

We uncover a novel antifibrotic action by ECM1 that binds CTGF and inhibits integrin αvβ6-mediated TGFβ activation. Targeting its loss has therapeutic potential for the treatment of DR and liver fibrosis in chronic conditions, such as cholangiopathy and ALD.

A Synergistic Overview between Microfluidics and Numerical Research for Vascular Flow and Pathological Investigations

Vascular diseases are widespread, and sometimes such life-threatening medical disorders cause abnormal blood flow, blood particle damage, changes to flow dynamics, restricted blood flow, and other adverse effects. The study of vascular flow is crucial in clinical practice because it can shed light on the causes of stenosis, aneurysm, blood cancer, and many other such diseases, and guide the development of novel treatments and interventions. Microfluidics and computational fluid dynamics (CFDs) are two of the most promising new tools for investigating these phenomena. When compared to conventional experimental methods, microfluidics offers many benefits, including lower costs, smaller sample quantities, and increased control over fluid flow and parameters. In this paper, we address the strengths and weaknesses of computational and experimental approaches utilizing microfluidic devices to investigate the rheological properties of blood, the forces of action causing diseases related to cardiology, provide an overview of the models and methodologies of experiments, and the fabrication of devices utilized in these types of research, and portray the results achieved and their applications. We also discuss how these results can inform clinical practice and where future research should go. Overall, it provides insights into why a combination of both CFDs, and experimental methods can give even more detailed information on disease mechanisms recreated on a microfluidic platform, replicating the original biological system and aiding in developing the device or chip itself.

PAI1 Regulates Cell Morphology and Migration Markers in Trastuzumab-Resistant HER2-Positive Breast Cancer Cells

HER2-positive breast cancer is a significant cause of mortality. Overcoming trastuzumab resistance requires a deeper understanding of its molecular mechanisms to develop effective therapies. This study investigates the role of plasminogen activator inhibitor-1 (PAI1) in migration and drug resistance in trastuzumab-resistant HER2-positive breast cancer. Trastuzumab resistance poses a significant challenge in clinical management due to its association with aggressive disease behaviour and limited treatment options. This study focuses on PAI1, a key player in the TGF-β signalling pathway, which is implicated in cancer progression and metastasis. Trastuzumab-resistant cell lines (SKBR3 and HCC1954) demonstrated markedly elevated PAI1 expression levels, up to 40-fold compared to parental lines. This elevation was accompanied by increased expression of migration markers such as Col4a1, Fibronectin, ICAM1, Timp2, and Vimentin. Through overexpression and silencing experiments, we observed that modulating PAI1 levels significantly impacts cell morphology, transitioning cells from an epithelial to mesenchymal phenotype. Importantly, combining trastuzumab with aleplasinin, a PAI1 inhibitor, synergistically reduced PAI1 expression in both parental and resistant cell lines. This suggests a potential therapeutic strategy to overcome trastuzumab resistance. These findings emphasise PAI1 as a critical mediator of migration and therapeutic response in HER2-positive breast cancer, offering insights into novel treatment approaches targeting PAI1 to improve clinical outcomes in drug resistance.

Global View of Domain-Specific O-Linked Mannose Glycosylation in Glycoengineered Cells

Protein O-linked mannose (O-Man) glycosylation is an evolutionary conserved posttranslational modification that fulfills important biological roles during embryonic development. Three nonredundant enzyme families, POMT1/POMT2, TMTC1-4, and TMEM260, selectively coordinate the initiation of protein O-Man glycosylation on distinct classes of transmembrane proteins, including α-dystroglycan, cadherins, and plexin receptors. However, a systematic investigation of their substrate specificities is lacking, in part due to the ubiquitous expression of O-Man glycosyltransferases in cells, which precludes analysis of pathway-specific O-Man glycosylation on a proteome-wide scale. Here, we apply a targeted workflow for membrane glycoproteomics across five human cell lines to extensively map O-Man substrates and genetically deconstruct O-Man initiation by individual and combinatorial knockout of O-Man glycosyltransferase genes. We established a human cell library for the analysis of substrate specificities of individual O-Man initiation pathways by quantitative glycoproteomics. Our results identify 180 O-Man glycoproteins, demonstrate new protein targets for the POMT1/POMT2 pathway, and show that TMTC1-4 and TMEM260 pathways widely target distinct Ig-like protein domains of plasma membrane proteins involved in cell-cell and cell-extracellular matrix interactions. The identification of O-Man on Ig-like folds adds further knowledge on the emerging concept of domain-specific O-Man glycosylation which opens for functional studies of O-Man-glycosylated adhesion molecules and receptors.

A screen for Plasmodium falciparum sporozoite surface protein binding to human hepatocyte surface receptors identifies novel host-pathogen interactions

BACKGROUND

Sporozoite invasion of hepatocytes is an essential step in the Plasmodium life-cycle and has similarities, at the cellular level, to merozoite invasion of erythrocytes. In the case of the Plasmodium blood-stage, efforts to identify host-pathogen protein-protein interactions have yielded important insights including vaccine candidates. In the case of sporozoite-hepatocyte invasion, the host-pathogen protein-protein interactions involved are poorly understood.

METHODS

To gain a better understanding of the protein-protein interaction between the sporozoite ligands and host receptors, a systematic screen was performed. The previous Plasmodium falciparum and human surface protein ectodomain libraries were substantially extended, resulting in the creation of new libraries comprising 88 P. falciparum sporozoite protein coding sequences and 182 sequences encoding human hepatocyte surface proteins. Having expressed recombinant proteins from these sequences, a plate-based assay was used, capable of detecting low affinity interactions between recombinant proteins, modified for enhanced throughput, to screen the proteins for interactions. The novel interactions identified in the screen were characterized biochemically, and their essential role in parasite invasion was further elucidated using antibodies and genetically manipulated Plasmodium parasites.

RESULTS

A total of 7540 sporozoite-hepatocyte protein pairs were tested under conditions capable of detecting interactions of at least 1.2 µM KD. An interaction between the human fibroblast growth factor receptor 4 (FGFR4) and the P. falciparum protein Pf34 is identified and reported here, characterizing its affinity and demonstrating the blockade of the interaction by reagents, including a monoclonal antibody. Furthermore, further interactions between Pf34 and a second P. falciparum rhoptry neck protein, PfRON6, and between human low-density lipoprotein receptor (LDLR) and the P. falciparum protein PIESP15 are identified. Conditional genetic deletion confirmed the essentiality of PfRON6 in the blood-stage, consistent with the important role of this protein in parasite lifecycle. Pf34 was refractory to attempted genetic modification. Antibodies to Pf34 abrogated the interaction and had a modest effect upon sporozoite invasion into primary human hepatocytes.

CONCLUSION

Pf34 and PfRON6 may be members of a functionally important invasion complex which could be a target for future interventions. The modified interaction screening assay, protein expression libraries and P. falciparum mutant parasites reported here may be a useful tool for protein interaction discovery and antigen candidate screening which could be of wider value to the scientific community.

Activation of endothelial TRPM2 exacerbates blood-brain barrier degradation in ischemic stroke

AIMS

Damage of the blood-brain barrier (BBB) is a hallmark of brain injury during the early stages of ischemic stroke. The subsequent endothelial hyperpermeability drives the initial pathological changes and aggravates neuronal death. Transient receptor potential melastatin 2 (TRPM2) is a Ca2+-permeable nonselective cation channel activated by oxidative stress. However, whether TRPM2 is involved in BBB degradation during ischemic stroke remains unknown. We aimed to investigate the role of TRPM2 in BBB degradation during ischemic stroke and the underlying molecular mechanisms.

METHODS AND RESULTS

Specific deletion of Trpm2 in endothelial cells using Cdh5 Cre produces a potent protective effect against brain injury in mice subjected to middle cerebral artery occlusion (MCAO), which is characterized by reduced infarction size, mitigated plasma extravasation, suppressed immune cell invasion, and inhibited oxidative stress. In vitro experiments using cultured cerebral endothelial cells (CECs) demonstrated that either Trpm2 deletion or inhibition of TRPM2 activation attenuates oxidative stress, Ca2+ overload, and endothelial hyperpermeability induced by oxygen-glucose deprivation (OGD) and CD36 ligand thrombospondin-1 (TSP1). In transfected HEK293T cells, OGD and TSP1 activate TRPM2 in a CD36-dependent manner. Noticeably, in cultured CECs, deleting Trpm2 or inhibiting TRPM2 activation also suppresses the activation of CD36 and cellular dysfunction induced by OGD or TSP1.

CONCLUSIONS

In conclusion, our data reveal a novel molecular mechanism in which TRPM2 and CD36 promote the activation of each other, which exacerbates endothelial dysfunction during ischemic stroke. Our study suggests that TRPM2 in endothelial cells is a promising target for developing more effective and safer therapies for ischemic stroke.

Complement receptor 1 is the human erythrocyte receptor for Plasmodium vivax erythrocyte binding protein

The discovery that Africans were resistant to infection by Plasmodium vivax (P. vivax) led to the conclusion that P. vivax invasion relied on the P. vivax Duffy Binding Protein (PvDBP) interacting with the Duffy Antigen Receptor for Chemokines (DARC) expressed on erythrocytes. However, the recent reporting of P. vivax infections in DARC-negative Africans suggests that the parasite might use an alternate invasion pathway to infect DARC-negative reticulocytes. To identify the parasite ligands and erythrocyte receptors that enable P. vivax invasion of both DARC-positive and -negative erythrocytes, we expressed region II containing the Duffy Binding-Like (DBL) domain of P. vivax erythrocyte binding protein (PvEBP-RII) and verified that the DBL domain binds to both DARC-positive and -negative erythrocytes. Furthermore, an AVidity-based EXtracelluar Interaction Screening (AVEXIS) was used to identify the receptor for PvEBP among over 750 human cell surface receptor proteins, and this approach identified only Complement Receptor 1 (CR1, CD35, or C3b/C4b receptor) as a PvEBP receptor. CR1 is a well-known receptor for P. falciparum Reticulocyte binding protein Homology 4 (PfRh4) and is present on the surfaces of both reticulocytes and normocytes, but its expression decreases as erythrocytes age. Indeed, PvEBP-RII bound to a subpopulation of both reticulocytes and normocytes, and this binding was blocked by the addition of soluble CR1 recombinant protein, indicating that CR1 is the receptor of PvEBP. In addition, we found that the Long Homology Repeat A (LHR-A) subdomain of CR1 is the only subdomain responsible for mediating the interaction with PvEBP-RII.

Recessive TMOD1 mutation causes childhood cardiomyopathy

Familial cardiomyopathy in pediatric stages is a poorly understood presentation of heart disease in children that is attributed to pathogenic mutations. Through exome sequencing, we report a homozygous variant in tropomodulin 1 (TMOD1; c.565C>T, p.R189W) in three individuals from two unrelated families with childhood-onset dilated and restrictive cardiomyopathy. To decipher the mechanism of pathogenicity of the R189W mutation in TMOD1, we utilized a wide array of methods, including protein analyses, biochemistry and cultured cardiomyocytes. Structural modeling revealed potential defects in the local folding of TMOD1R189W and its affinity for actin. Cardiomyocytes expressing GFP-TMOD1R189W demonstrated longer thin filaments than GFP-TMOD1wt-expressing cells, resulting in compromised filament length regulation. Furthermore, TMOD1R189W showed weakened activity in capping actin filament pointed ends, providing direct evidence for the variant's effect on actin filament length regulation. Our data indicate that the p.R189W variant in TMOD1 has altered biochemical properties and reveals a unique mechanism for childhood-onset cardiomyopathy.

Genetic Polymorphisms of GP1BA, PEAR1, and PAI-1 may be Associated with Serum sIgE and Blood Eosinophil Levels in Chinese Patients with Allergic Diseases

BACKGROUND

It has been suggested that genetic factors may be substantially linked to allergy disorders.

OBJECTIVE

This study aims to investigate the relationship between the serum specific Immunoglobulin E (sIgE), blood eosinophil, and the polymorphisms of glycoprotein Ib alpha gene (GP1BA) rs6065, platelet endothelial aggregation receptor 1 gene (PEAR1) rs12041331, and plasminogen activator inhibitor 1 gene (PAI-1) rs1799762.

METHODS

From the Peking Union Medical College Hospital, this study enrolled 60 healthy participants and 283 participants with allergic diseases. TaqMan-minor groove binder (MGB) quantitative polymerase chain reaction (qPCR) was used to examine the gene polymorphisms in each group.

RESULTS

The TaqMan-MGB qPCR results were completely consistent with the DNA sequencing results, according to other studies in this medical center (Kappa =1, p <0.001). The GP1BA rs6065, PEAR1 rs12041331, and PAI-1 rs1799762 polymorphisms did not show different distribution between allergy patients and healthy individuals. Concerning allergy patients, the CT (n=33) genotype of GP1BA rs6065 had higher blood eosinophil level than the CC (n=250) genotype (0.59, IQR 0.32-0.72 vs 0.31, IQR 0.15-0.61, *109/L, p =0.005). The serum sIgE of AA (n=46) genotype of PEAR1 rs12041331 was lower (median 3.7, interquartile quartiles (IQR) 0.2-16.8, kU/L) than the GA (n=136) and GG (n=101) genotypes (GA median 16.3, IQR 3.1-46.3, kU/L, p = 0.002; GG median 12.9, IQR 3.0-46.9, kU/L, p =0.003). The GA genotypes of PEAR1 rs12041331were with higher blood eosinophil levels (median 0.42, IQR 0.17-0.74 *109/L) than the AA genotype (median 0.25, IQR 0.15-0.41*109/L, p =0.012). The sIgE of the 5G5G (n=44) genotype of PAI-1 rs1799762 was lower (median 5.0, IQR 0.1-22.8, kU/L) than the 4G5G (n=144) (median 17.3, IQR 3.7-46.0, kU/L, p = 0.012).

CONCLUSION

The GP1BA rs6065, PEAR1 rs12041331, and PAI-1 rs1799762 polymorphisms may be associated with the genetic susceptibility of serum sIgE or blood eosinophil in Chinese allergic disease patients.

SVEP1 is an endogenous ligand for the orphan receptor PEAR1

Sushi, von Willebrand factor type A, EGF and pentraxin domain containing 1 (SVEP1) is an extracellular matrix protein that causally promotes vascular disease and associates with platelet reactivity in humans. Here, using a human genomic and proteomic approach, we identify a high affinity, disease-relevant, and potentially targetable interaction between SVEP1 and the orphan receptor Platelet and Endothelial Aggregation Receptor 1 (PEAR1). This interaction promotes PEAR1 phosphorylation and disease associated AKT/mTOR signaling in vascular cells and platelets. Mice lacking SVEP1 have reduced platelet activation, and exogenous SVEP1 induces PEAR1-dependent activation of platelets. SVEP1 and PEAR1 causally and concordantly relate to platelet phenotypes and cardiovascular disease in humans, as determined by Mendelian Randomization. Targeting this receptor-ligand interaction may be a viable therapeutic strategy to treat or prevent cardiovascular and thrombotic disease.

New tools to study the interaction between integrins and latent TGFβ1

Transforming growth factor beta (TGFβ) 1 regulates cell differentiation and proliferation in different physiological settings, but is also involved in fibrotic progression and protects tumors from the immune system. Integrin αVβ6 has been shown to activate latent TGFβ1 by applying mechanical forces onto the latency-associated peptide (LAP). While the extracellular binding between αVβ6 and LAP1 is well characterized, less is known about the cytoplasmic adaptations that enable αVβ6 to apply such forces. Here, we generated new tools to facilitate the analysis of this interaction. We combined the integrin-binding part of LAP1 with a GFP and the Fc chain of human IgG. This chimeric protein, sLAP1, revealed a mechanical rearrangement of immobilized sLAP1 by αVβ6 integrin. This unique interaction was not observed between sLAP1 and other integrins. We also analyzed αVβ6 integrin binding to LAP2 and LAP3 by creating respective sLAPs. Compared to sLAP1, integrin αVβ6 showed less binding to sLAP3 and no rearrangement. These observations indicate differences in the binding of αVβ6 to LAP1 and LAP3 that have not been appreciated so far. Finally, αVβ6-sLAP1 interaction was maintained even at strongly reduced cellular contractility, highlighting the special mechanical connection between αVβ6 integrin and latent TGFβ1.

Germline gain-of-function MMP11 variant results in an aggressive form of colorectal cancer

Matrix metalloproteinase-11 (MMP11) is an enzyme with proteolytic activity against matrix and nonmatrix proteins. Although most MMPs are secreted as inactive proenzymes and are later activated extracellularly, MMP11 is activated intracellularly by furin within the constitutive secretory pathway. It is a key factor in physiological tissue remodeling and its alteration may play an important role in the progression of epithelial malignancies and other diseases. TCGA colon and colorectal adenocarcinoma data showed that upregulation of MMP11 expression correlates with tumorigenesis and malignancy. Here, we provide evidence that a germline variant in the MMP11 gene (NM_005940: c.232C>T; p.(Pro78Ser)), identified by whole exome sequencing, can increase the tumorigenic properties of colorectal cancer (CRC) cells. P78S is located in the prodomain region, which is responsible for blocking MMP11's protease activity. This variant was detected in the proband and all the cancer-affected family members analyzed, while it was not detected in healthy relatives. In silico analyses predict that P78S could have an impact on the activation of the enzyme. Furthermore, our in vitro analyses show that the expression of P78S in HCT116 cells increases tumor cell invasion and proliferation. In summary, our results show that this variant could modify the structure of the MMP11 prodomain, producing a premature or uncontrolled activation of the enzyme that may contribute to an early CRC onset in these patients. The study of this gene in other CRC cases will provide further information about its role in CRC development, which might improve patient treatment in the future.

The 4G/5G polymorphism of plasminogen activator inhibitor type 1 is a predictor of allergic cough

Background: It has been suggested that genetic factors may be substantially linked to allergy disorders. This study aims to investigate the relationship between the genetic susceptibility of Chinese patients with allergy disorders and the polymorphisms of plasminogen activator inhibitor 1 gene (PAI-1) rs1799762, cysteinyl leukotriene receptor 1 gene (CYSLTR1) rs320995, gasdermin B gene (GSDMB) rs7216389, glycoprotein IIIa gene (GPIIIa) rs5918, glycoprotein Ib alpha gene (GP1BA) rs6065, platelet endothelial aggregation receptor 1 gene (PEAR1) rs12041331, and tumor necrosis factor alpha gene (TNF-α) rs1800629. Methods: From the Peking Union Medical College Hospital, this study enrolled 60 healthy participants and 286 participants with allergic diseases. TaqMan-minor groove binder (MGB) quantitative polymerase chain reaction (qPCR) was used to examine the gene polymorphisms in each group. Results: The TaqMan-MGB qPCR results were completely consistent with the DNA sequencing results, according to other studies in this medical center (Kappa = 1, p < .001). Only the distribution of PAI-1 rs1799762 was different between patients with allergic cough and healthy people (χ2 = 7.48, p = .0238). With regard to cough patients, the 4G4G and 5G5G genotypes were more frequent (allergic cough vs. healthy individuals: 4G4G 57.9% vs. 26.7%; 5G5G 20.0% vs. 13.3%), but the 4G5G genotype was more frequent in healthy people (allergic cough vs. healthy individuals: 45.7% vs. 60.0%). The CYSLTR1 rs320995, GSDMB rs7216389, GPIIIa rs5918, GP1BA rs6065, PEAR1 rs12041331, and TNF-α rs1800629 polymorphisms, however, did not show any of such relationships. Conclusion: The PAI-1 rs1799762 polymorphisms may be associated with the genetic susceptibility of Chinese allergic disease patients with cough performance.

Heparin and heparin proteoglycan-mimetics activate platelets via PEAR1 and PI3Kβ

BACKGROUND

Platelet endothelial aggregation receptor 1 (PEAR1) is a single-transmembrane orphan receptor primarily expressed on platelets and endothelial cells. Genetic variants of PEAR1 have repeatedly and independently been identified to be associated with cardiovascular diseases, including coronary artery disease.

OBJECTIVES

We have identified sulfated fucoidans and their mimetics as ligands for PEAR1 and proposed that its endogenous ligand is a sulfated proteoglycan. The aim of this study was to test this hypothesis.

METHODS

A heparin proteoglycan-mimetic (HPGM) was created by linking unfractionated heparin (UFH) to albumin. The ability of the HPGM, UFH and selectively desulfated heparins to stimulate platelet aggregation and protein phosphorylation was investigated. Nanobodies against the 12th to 13th epidermal growth factor-like repeat of PEAR1 and phosphoinositide 3-kinase (PI3K) isoform-selective inhibitors were tested for the inhibition of platelet activation.

RESULTS

We show that HPGM, heparin conjugated to an albumin protein core, stimulates aggregation and phosphorylation of PEAR1 in washed platelets. Platelet aggregation was abolished by an anti-PEAR1 nanobody, Nb138. UFH stimulated platelet aggregation in washed platelets, but desulfated UFH did not. Furthermore, HPGM, but not UFH, stimulated maximal aggregation in platelet-rich plasma. However, both HPGM and UFH increased integrin αIIbβ3 activation in whole blood. By using PI3K isoform-selective inhibitors, we show that PEAR1 activates PI3Kβ, leading to Akt phosphorylation.

CONCLUSION

Our findings reveal that PEAR1 is a receptor for heparin and HPGM and that PI3Kβ is a key signaling molecule downstream of PEAR1 in platelets. These findings may have important implications for our understanding of the role of PEAR1 in cardiovascular disease.

PEAR1 regulates expansion of activated fibroblasts and deposition of extracellular matrix in pulmonary fibrosis

Pulmonary fibrosis is a chronic interstitial lung disease that causes irreversible and progressive lung scarring and respiratory failure. Activation of fibroblasts plays a central role in the progression of pulmonary fibrosis. Here we show that platelet endothelial aggregation receptor 1 (PEAR1) in fibroblasts may serve as a target for pulmonary fibrosis therapy. Pear1 deficiency in aged mice spontaneously causes alveolar collagens accumulation. Mesenchyme-specific Pear1 deficiency aggravates bleomycin-induced pulmonary fibrosis, confirming that PEAR1 potentially modulates pulmonary fibrosis progression via regulation of mesenchymal cell function. Moreover, single cell and bulk tissue RNA-seq analysis of pulmonary fibroblast reveals the expansion of Activated-fibroblast cluster and enrichment of marker genes in extracellular matrix development in Pear1^-/- fibrotic lungs. We further show that PEAR1 associates with Protein Phosphatase 1 to suppress fibrotic factors-induced intracellular signalling and fibroblast activation. Intratracheal aerosolization of monoclonal antibodies activating PEAR1 greatly ameliorates pulmonary fibrosis in both WT and Pear1-humanized mice, significantly improving their survival rate.

Protein Scaffold-Based Multimerization of Soluble ACE2 Efficiently Blocks SARS-CoV-2 Infection In Vitro and In Vivo

Soluble ACE2 (sACE2) decoys are promising agents to inhibit SARS-CoV-2, as their efficiency is unlikely to be affected by escape mutations. However, their success is limited by their relatively poor potency. To address this challenge, multimeric sACE2 consisting of SunTag or MoonTag systems is developed. These systems are extremely effective in neutralizing SARS-CoV-2 in pseudoviral systems and in clinical isolates, perform better than the dimeric or trimeric sACE2, and exhibit greater than 100-fold neutralization efficiency, compared to monomeric sACE2. SunTag or MoonTag fused to a more potent sACE2 (v1) achieves a sub-nanomolar IC50 , comparable with clinical monoclonal antibodies. Pseudoviruses bearing mutations for variants of concern, including delta and omicron, are also neutralized efficiently with multimeric sACE2. Finally, therapeutic treatment of sACE2(v1)-MoonTag provides protection against SARS-CoV-2 infection in an in vivo mouse model. Therefore, highly potent multimeric sACE2 may offer a promising treatment approach against SARS-CoV-2 infections.

Integrative analysis of drug response and clinical outcome in acute myeloid leukemia

Acute myeloid leukemia (AML) is a cancer of myeloid-lineage cells with limited therapeutic options. We previously combined ex vivo drug sensitivity with genomic, transcriptomic, and clinical annotations for a large cohort of AML patients, which facilitated discovery of functional genomic correlates. Here, we present a dataset that has been harmonized with our initial report to yield a cumulative cohort of 805 patients (942 specimens). We show strong cross-cohort concordance and identify features of drug response. Further, deconvoluting transcriptomic data shows that drug sensitivity is governed broadly by AML cell differentiation state, sometimes conditionally affecting other correlates of response. Finally, modeling of clinical outcome reveals a single gene, PEAR1, to be among the strongest predictors of patient survival, especially for young patients. Collectively, this report expands a large functional genomic resource, offers avenues for mechanistic exploration and drug development, and reveals tools for predicting outcome in AML.

A physical wiring diagram for the human immune system

The human immune system is composed of a distributed network of cells circulating throughout the body, which must dynamically form physical associations and communicate using interactions between their cell-surface proteomes1. Despite their therapeutic potential2, our map of these surface interactions remains incomplete3,4. Here, using a high-throughput surface receptor screening method, we systematically mapped the direct protein interactions across a recombinant library that encompasses most of the surface proteins that are detectable on human leukocytes. We independently validated and determined the biophysical parameters of each novel interaction, resulting in a high-confidence and quantitative view of the receptor wiring that connects human immune cells. By integrating our interactome with expression data, we identified trends in the dynamics of immune interactions and constructed a reductionist mathematical model that predicts cellular connectivity from basic principles. We also developed an interactive multi-tissue single-cell atlas that infers immune interactions throughout the body, revealing potential functional contexts for new interactions and hubs in multicellular networks. Finally, we combined targeted protein stimulation of human leukocytes with multiplex high-content microscopy to link our receptor interactions to functional roles, in terms of both modulating immune responses and maintaining normal patterns of intercellular associations. Together, our work provides a systematic perspective on the intercellular wiring of the human immune system that extends from systems-level principles of immune cell connectivity down to mechanistic characterization of individual receptors, which could offer opportunities for therapeutic intervention.

Autoantibodies to IgE can induce the release of proinflammatory and vasoactive mediators from human cardiac mast cells

Mast cells are multifunctional immune cells with complex roles in tissue homeostasis and disease. Cardiac mast cells (HCMCs) are strategically located within the human myocardium, in atherosclerotic plaques, in proximity to nerves, and in the aortic valve. HCMCs express the high-affinity receptor (FcεRI) for IgE and can be activated by anti-IgE and anti-FcεRI. Autoantibodies to IgE and/or FcεRI have been found in the serum of patients with a variety of immune disorders. We have compared the effects of different preparations of IgG anti-IgE obtained from patients with atopic dermatitis (AD) with rabbit IgG anti-IgE on the release of preformed (histamine and tryptase) and lipid mediators [prostaglandin D₂ (PGD₂) and cysteinyl leukotriene C₄ (LTC₄)] from HCMCs. Functional human IgG anti-IgE from one out of six AD donors and rabbit IgG anti-IgE induced the release of preformed (histamine, tryptase) and de novo synthesized mediators (PGD₂ and LTC₄) from HCMCs. Human IgG anti-IgE was more potent than rabbit IgG anti-IgE in inducing proinflammatory mediators from HCMCs. Human monoclonal IgE was a competitive antagonist of both human and rabbit IgG anti-IgE. Although functional anti-IgE autoantibodies rarely occur in patients with AD, when present, they can powerfully activate the release of proinflammatory and vasoactive mediators from HCMCs.

An embeddable molecular code for Lewis X modification through interaction with fucosyltransferase 9

N-glycans are diversified by a panel of glycosyltransferases in the Golgi, which are supposed to modify various glycoproteins in promiscuous manners, resulting in unpredictable glycosylation profiles in general. In contrast, our previous study showed that fucosyltransferase 9 (FUT9) generates Lewis X glycotopes primarily on lysosome-associated membrane protein 1 (LAMP-1) in neural stem cells. Here, we demonstrate that a contiguous 29-amino acid sequence in the N-terminal domain of LAMP-1 is responsible for promotion of the FUT9-catalyzed Lewis X modification. Interestingly, Lewis X modification was induced on erythropoietin as a model glycoprotein both in vitro and in cells, just by attaching this sequence to its C-terminus. Based on these results, we conclude that the amino acid sequence from LAMP-1 functions as a “Lewis X code”, which is deciphered by FUT9, and can be embedded into other glycoproteins to evoke a Lewis X modification, opening up new possibilities for protein engineering and cell engineering.

A 29-amino acid sequence in the N-terminal domain of LAMP-1 promotes its Lewis X glycosylation and is embeddable to other proteins for Lewis X glycoengineering.

Ubiquitination of ADRα1d/SerpinA1 complex stimulates hypoxia to induce gastric tumorigenesis with a combination of Helicobacter pylori and chronic stress through IL-1α

BACKGROUND

Helicobacter pylori (H. pylori) has been recognized as the class I carcinogen of gastric cancer and several studies have demonstrated that chronic stress may accelerate gastric cancer progression. However, the evidence is not sufficient.

METHODS

Here, we developed a mouse model that combined H. pylori infection with chronic stress. Gastric inflammation promotes gastric tumor development progression. To evaluate the number of pro-inflammatory cells through observing the numbers of activated macrophages and neutrophils in mice gastric tumors compared with untreated mice or only treated with one factor. ADRα1d /SerpinA1 expression and localization were assessed under stress conditions and H. pylori infection, and evaluated by analyzing IL-1α, CD8, platelet, and RBC status using α- or β- blockers against gastritis to prevent gastric cancer.

RESULTS

Further mechanism study showed that stress hormones increase the number of CD8⁺ lymphocytes by activating ADRβ2 receptors, leading to IL-1α secretion and tumorigenicity. Gastric carcinogenesis also involves gastric muscle contraction mediated through ADRα1d/Serpina1 interaction. Specifically, we showed that the ADRα1d/SerpinA1 complex increases glucose uptake and the development of hypoxia conditions. These responses promote platelet aggregation and muscle contraction. In turn, gastric cancer cells increase lactate production and promote gastric cell proliferation through Muc-13 and IL-1α stimulation.

CONCLUSION

H. pylori infection in combination with chronic stress can lead to gastric cancer, and the synergistic effects of cytokine production (i.e. IL-1α), T lymphocyte dysfunction contributes to gastric carcinogenesis which will offer treatment opportunities for stress-associated gastric cancer and provide new strategies for the prevention and treatment of gastric cancer in clinics.

Serine Protease Inhibitors Restrict Host Susceptibility to SARS-CoV-2 Infections

The coronavirus disease 2019, COVID-19, is a complex disease with a wide range of symptoms from asymptomatic infections to severe acute respiratory syndrome with lethal outcome. Individual factors such as age, sex, and comorbidities increase the risk for severe infections, but other aspects, such as genetic variations, are also likely to affect the susceptibility to SARS-CoV-2 infection and disease severity. Here, we used a human 3D lung cell model based on primary cells derived from multiple donors to identity host factors that regulate SARS-CoV-2 infection. With a transcriptomics-based approach, we found that less susceptible donors show a higher expression level of serine protease inhibitors SERPINA1, SERPINE1, and SERPINE2, identifying variation in cellular serpin levels as restricting host factors for SARS-CoV-2 infection. We pinpoint their antiviral mechanism of action to inhibition of the cellular serine protease, TMPRSS2, thereby preventing cleavage of the viral spike protein and TMPRSS2-mediated entry into the target cells. By means of single-cell RNA sequencing, we further locate the expression of the individual serpins to basal, ciliated, club, and goblet cells. Our results add to the importance of genetic variations as determinants for SARS-CoV-2 susceptibility and suggest that genetic deficiencies of cellular serpins might represent risk factors for severe COVID-19. Our study further highlights TMPRSS2 as a promising target for antiviral intervention and opens the door for the usage of locally administered serpins as a treatment against COVID-19. IMPORTANCE Identification of host factors affecting individual SARS-CoV-2 susceptibility will provide a better understanding of the large variations in disease severity and will identify potential factors that can be used, or targeted, in antiviral drug development. With the use of an advanced lung cell model established from several human donors, we identified cellular protease inhibitors, serpins, as host factors that restrict SARS-CoV-2 infection. The antiviral mechanism was found to be mediated by the inhibition of a serine protease, TMPRSS2, which results in a blockage of viral entry into target cells. Potential treatments with these serpins would not only reduce the overall viral burden in the patients, but also block the infection at an early time point, reducing the risk for the hyperactive immune response common in patients with severe COVID-19.

TRPM2 deficiency in mice protects against atherosclerosis by inhibiting TRPM2-CD36 inflammatory axis in macrophages

Atherosclerosis is the major cause of ischemic heart disease and stroke, the leading causes of mortality worldwide. The central pathological features of atherosclerosis include macrophage infiltration and foam cell formation. However, the detailed mechanisms regulating these two processes remain unclear. Here we show that oxidative stress-activated Ca2+-permeable transient receptor potential melastatin 2 (TRPM2) plays a critical role in atherogenesis. Both global and macrophage-specific Trpm2 deletion protect Apoe -/- mice against atherosclerosis. Trpm2 deficiency reduces oxidized low-density lipoprotein (oxLDL) uptake by macrophages, thereby minimizing macrophage infiltration, foam cell formation and inflammatory responses. Activation of the oxLDL receptor CD36 induces TRPM2 activity, and vice versa. In cultured macrophages, TRPM2 is activated by CD36 ligands oxLDL and thrombospondin-1 (TSP1), and deleting Trpm2 or inhibiting TRPM2 activity suppresses the activation of CD36 signaling cascade induced by oxLDL and TSP1. Our findings establish the TRPM2-CD36 axis as a molecular mechanism underlying atherogenesis, and suggest TRPM2 as a potential therapeutic target for atherosclerosis.

Proteomic profiling in cerebral amyloid angiopathy reveals an overlap with CADASIL highlighting accumulation of HTRA1 and its substrates

Cerebral amyloid angiopathy (CAA) is an age-related condition and a major cause of intracerebral hemorrhage and cognitive decline that shows close links with Alzheimer's disease (AD). CAA is characterized by the aggregation of amyloid-β (Aβ) peptides and formation of Aβ deposits in the brain vasculature resulting in a disruption of the angioarchitecture. Capillaries are a critical site of Aβ pathology in CAA type 1 and become dysfunctional during disease progression. Here, applying an advanced protocol for the isolation of parenchymal microvessels from post-mortem brain tissue combined with liquid chromatography tandem mass spectrometry (LC-MS/MS), we determined the proteomes of CAA type 1 cases (n = 12) including a patient with hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D), and of AD cases without microvascular amyloid pathology (n = 13) in comparison to neurologically healthy controls (n = 12). ELISA measurements revealed microvascular Aβ1-40 levels to be exclusively enriched in CAA samples (mean: > 3000-fold compared to controls). The proteomic profile of CAA type 1 was characterized by massive enrichment of multiple predominantly secreted proteins and showed significant overlap with the recently reported brain microvascular proteome of patients with cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary cerebral small vessel disease (SVD) characterized by the aggregation of the Notch3 extracellular domain. We found this overlap to be largely attributable to the accumulation of high-temperature requirement protein A1 (HTRA1), a serine protease with an established role in the brain vasculature, and several of its substrates. Notably, this signature was not present in AD cases. We further show that HTRA1 co-localizes with Aβ deposits in brain capillaries from CAA type 1 patients indicating a pathologic recruitment process. Together, these findings suggest a central role of HTRA1-dependent protein homeostasis in the CAA microvasculature and a molecular connection between multiple types of brain microvascular disease.

Phosphatidylserine-Targeting Monoclonal Antibodies Exhibit Distinct Biochemical and Cellular Effects on Anti-CD3/CD28-Stimulated T Cell IFN-γ and TNF-α Production

Phosphatidylserine (PS)-targeting monoclonal Abs (mAbs) that directly target PS and target PS via β2-gp1 (β2GP1) have been in preclinical and clinical development for over 10 y for the treatment of infectious diseases and cancer. Although the intended targets of PS-binding mAbs have traditionally included pathogens as well as stressed tumor cells and its associated vasculature in oncology, the effects of PS-targeting mAbs on activated immune cells, notably T cells, which externalize PS upon Ag stimulation, is not well understood. Using human T cells from healthy donor PBMCs activated with an anti-CD3 + anti-CD28 Ab mixture (anti-CD3/CD28) as a model for TCR-mediated PS externalization and T cell stimulation, we investigated effects of two different PS-targeting mAbs, 11.31 and bavituximab (Bavi), on TCR activation and TCR-mediated cytokine production in an ex vivo paradigm. Although 11.31 and Bavi bind selectivity to anti-CD3/28 activated T cells in a PS-dependent manner, surprisingly, they display distinct functional activities in their effect on IFN-γ and TNF-ɑ production, whereby 11.31, but not Bavi, suppressed cytokine production. This inhibitory effect on anti-CD3/28 activated T cells was observed on both CD4⁺ and CD8⁺ cells and independently of monocytes, suggesting the effects of 11.31 were directly mediated by binding to externalized PS on activated T cells. Imaging showed 11.31 and Bavi bind at distinct focal depots on the cell membrane. Collectively, our findings indicate that PS-targeting mAb 11.31 suppresses cytokine production by anti-CD3/28 activated T cells.

Lysyl hydroxylase 2-induced collagen cross-link switching promotes metastasis in head and neck squamous cell carcinomas

Head and neck squamous cell carcinoma (HNSCC) is the 6th most common cancer worldwide and incidence rates are continuing to rise globally. HNSCC patient prognosis is closely related to the occurrence of tumor metastases, and collagen within the tumor microenvironment (TME) plays a key role in this process. Lysyl hydroxylase 2 (LH2), encoded by the Procollagen-Lysine,2-Oxoglutarate 5-Dioxygenase 2 (PLOD2) gene, catalyzes hydroxylation of telopeptidyl lysine (Lys) residues of fibrillar collagens which then undergo subsequent modifications to form stable intermolecular cross-links that change the biomechanical properties (i.e. quality) of the TME. While LH2-catalyzed collagen modification has been implicated in driving tumor progression and metastasis in diverse cancers, little is known about its role in HNSCC progression. Thus, using gain- and loss-of-function studies, we examined the effects of LH2 expression levels on collagen cross-linking and cell behavior in vitro and in vivo using a tractable bioluminescent imaging-based orthotopic xenograft model. We found that LH2 overexpression dramatically increases HNSCC cell migratory and invasive abilities in vitro and that LH2-driven changes in collagen cross-linking robustly induces metastasis in vivo. Specifically, the amount of LH2-mediated collagen cross-links increased significantly with PLOD2 overexpression, without affecting the total quantity of collagen cross-links. Conversely, LH2 knockdown significantly blunted HNSCC cells invasive capacity in vitro and metastatic potential in vivo. Thus, regardless of the total "quantity" of collagen crosslinks, it is the "quality" of these cross-links that is the key driver of HNSCC tumor metastatic dissemination. These data implicate LH2 as a key regulator of HNSCC tumor invasion and metastasis by modulating collagen cross-link quality and suggest that therapeutic strategies targeting LH2-mediated collagen cross-linking in the TME may be effective in controlling tumor progression and improving disease outcomes.

Is the endogenous ligand for PEAR1 a proteoglycan: clues from the sea

Platelet Endothelial Aggregation Receptor 1 (PEAR1) is an orphan receptor of unknown function which mediates powerful activation of platelets and endothelial cells in response to crosslinking by antibodies and sulfated polysaccharides belonging to the dextran and fucoidan families. PEAR1 is a single transmembrane protein composed of 15 epidermal growth factor-like repeat sequences and with a conserved binding motif, YXXM, which when phosphorylated binds to phosphoinositide 3-kinase (PI3K). The 13^th of the repeats has a heparin-binding sequence that is the site of interaction with the sulfated fucoidans and the only known endogenous ligand FcεRIα. Crosslinking of PEAR1 drives Src family kinase phosphorylation of the cytosolic tail leading to binding and activation of PI3K. In this Opinion Article, we summarize the literature on PEAR1 expression, structure and signaling, and the search for further endogenous ligands. We highlight one article in which phosphorylation of a 150 kDa platelet protein by heparin-containing ligands has been reported and propose that PEAR1 is a receptor for one or more glycosaminoglycan-conjugated proteins (proteoglycans). The up-regulation of PEAR1 at sites of inflammation in the vasculature and its role in angiogenesis suggests a role in the interplay of inflammation, platelets, coagulation, and thromboinflammation. We speculate that this may explain the link between single nucleotide variants in PEAR1 and cardiovascular disease.

Niche-derived soluble DLK1 promotes glioma growth

Tumor cell behaviors associated with aggressive tumor growth such as proliferation, therapeutic resistance, and stem cell characteristics are regulated in part by soluble factors derived from the tumor microenvironment. Tumor-associated astrocytes represent a major component of the glioma tumor microenvironment, and astrocytes have an active role in maintenance of normal neural stem cells in the stem cell niche, in part via secretion of soluble delta-like noncanonical Notch ligand 1 (DLK1). We found that astrocytes, when exposed to stresses of the tumor microenvironment such as hypoxia or ionizing radiation, increased secretion of soluble DLK1. Tumor-associated astrocytes in a glioma mouse model expressed DLK1 in perinecrotic and perivascular tumor areas. Glioma cells exposed to recombinant DLK1 displayed increased proliferation, enhanced self-renewal and colony formation abilities, and increased levels of stem cell marker genes. Mechanistically, DLK1-mediated effects on glioma cells involved increased and prolonged stabilization of hypoxia-inducible factor 2alpha, and inhibition of hypoxia-inducible factor 2alpha activity abolished effects of DLK1 in hypoxia. Forced expression of soluble DLK1 resulted in more aggressive tumor growth and shortened survival in a genetically engineered mouse model of glioma. Together, our data support DLK1 as a soluble mediator of glioma aggressiveness derived from the tumor microenvironment.

Conjugation of arginylglycylaspartic acid to human serum albumin decreases the tumor-targeting effect of albumin by hindering its secreted protein acidic and rich in cysteine-mediated accumulation in tumors

Human serum albumin (HSA) accumulates in tumors by the enhanced permeability and retention (EPR) effect, which is a passive targeting effect in tumors. A recent study showed that secreted protein acidic and rich in cysteine (SPARC), an albumin-binding protein, mediates albumin accumulation in tumors. Arg-Gly-Asp (RGD) is a peptide targeting integrin α_vβ₃, which is highly expressed during tumor angiogenesis. We investigated whether conjugation of RGD to HSA could synergistically enhance tumor targeting. Accumulation of cRGDyK-HSA in integrin α_vβ₃-expressing SK-OV3 cells was observed by confocal microscopy. In SK-OV3 cells overexpressing the albumin binding protein SPARC, cellular uptake of HSA increased, but uptake of cRGDyK-HSA did not. cRGDyK-HSA showed decreased tumor accumulation compared with HSA by positron emission tomography (PET) scanning and biodistribution studies in an SK-OV3 xenograft mouse model. In SK-OV3 tumors, HSA accumulation colocalized with SPARC expression, while cRGDyK-HSA only accumulated in the outer region of the tumor, even though SPARC and integrin α_vβ₃ were expressed within the tumor core. We speculate that cRGDyK conjugation to HSA changes the characteristics of HSA and hinders its tumor-targeting effect. Therefore, HSA should be modified to preserve its native characteristics and enhance the tumor-targeting effects of HSA conjugates.

PEAR1 polymorphisms as a prognostic factor in hemostasis and cardiovascular diseases

Platelet Endothelial Aggregation Receptor (PEAR1), as a platelet receptor, plays a vital role in hemostasis. This receptor, by its extracellular part, causes platelet adhesion and consequently initiates platelet aggregation. Dysfunction of PEAR1 can disrupt platelet aggregation in patients with cardiovascular diseases (CVDs). The content used in this paper has been taken from English language articles (2005-2020) retrieved from Pubmed database and Google scholar search engine using "Cardiovascular Disease", "PEAR1", "Polymorphism", and "Platelet Aggregation" keywords. Some PEAR1 polymorphisms can disrupt homeostasis and interfere with the function mechanism of cardiac drugs. Since polymorphisms in this gene affect platelet function and the platelet aggregation process, PEAR1 could be further studied in the future as an essential factor in controlling the treatment process of patients with cardiovascular diseases. PEAR1 polymorphisms through disruption of the platelet aggregation process can be a risk factor in patients with CVDs. Therefore, controlling patients through genetic testing and the evaluation of PEAR1 polymorphisms can help improve the treatment process of patients. According to the studies on the PEAR1 gene and the effect of different polymorphisms on some crucial issues in CVDs patients (changes in platelet activity), it is clear that if there is a significant relationship between polymorphisms and CVDs, they can be used as prognostic and diagnostic markers. This study aims to evaluate the prognosis and drug treatment of the PEAR1 gene in CVDs patients.

Impact of Platelet Endothelial Aggregation Receptor-1 Genotypes on Platelet Reactivity and Early Cardiovascular Outcomes in Patients Undergoing Percutaneous Coronary Intervention and Treated With Aspirin and Clopidogrel

BACKGROUND

The genetic determinants of response to clopidogrel and aspirin are incompletely characterized. Recently, PEAR1 (platelet endothelial aggregation receptor-1) rs12041331 polymorphism has been shown to influence the platelet reactivity, but its impact on cardiovascular outcomes remains unclear in patients treated with antiplatelet agents.

METHODS AND RESULTS

In this prospective cohort study, 2439 Chinese patients with acute coronary syndrome or stable coronary artery disease undergoing coronary stent implantation and receiving clopidogrel and aspirin were consecutively recruited. Their platelet reactivity was determined by light transmission aggregometry at 5 and 30 days after coronary intervention. Genotyping was performed using an improved multiplex ligation detection reaction technique. All patients completed a 30-day follow-up for clinical outcomes. Genotyping for PEAR1 showed 768 (38.3%) GG homozygotes, 941 (46.9%) GA heterozygotes, and 298 (14.8%) AA homozygotes. The 30-day incidence of major adverse cardiovascular events, the composite of cardiovascular death, nonfatal myocardial infarction, and ischemic stroke were significantly higher in AA homozygotes than in non-AA homozygotes (adjusted hazard ratio, 2.78; 95% CI, 1.13-6.82; P=0.026), irrespective of CYP2C19*2 loss-of-function polymorphism and known outcome predictors including age, sex, smoking, and diabetes mellitus. The ADP-induced platelet aggregation was significantly lower in AA homozygotes than that in GG homozygotes at both time points, although no significant difference was found for the arachidonic acid-induced platelet aggregation among the 3 groups.

CONCLUSIONS

About 15% of Chinese patients undergoing coronary stent implantation were AA homozygotes for PEAR1 rs12041331. These patients had ≈3-fold increase in short-term major adverse cardiovascular events risk compared with non-AA homozygotes, and the adverse clinical outcome is unlikely to be mediated by suboptimal pharmacological response to aspirin or clopidogrel.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01968499.

The Enigma of CRB1 and CRB1 Retinopathies

Mutations in the gene Crumbs homolog 1 (CRB1) are responsible for several retinopathies that are diverse in severity and phenotype. Thus, there is considerable incentive to determine how disruption of this gene causes disease. Progress on this front will aid in developing molecular diagnostics that can predict disease severity with the ultimate goal of developing therapies for CRB1 retinopathies via gene replacement. The purpose of this review is to summarize what is known regarding CRB1 and highlights information outstanding. Doing so will provide a framework toward a thorough understanding of CRB1 at the molecular and protein level with the ultimate goal of deciphering how it contributes to the disease.

Genetically Engineered Lung Cancer Cells for Analyzing Epithelial-Mesenchymal Transition

Cell plasticity, defined as the ability to undergo phenotypical transformation in a reversible manner, is a physiological process that also exerts important roles in disease progression. Two forms of cellular plasticity are epithelial-mesenchymal transition (EMT) and its inverse process, mesenchymal-epithelial transition (MET). These processes have been correlated to the poor outcome of different types of neoplasias as well as drug resistance development. Since EMT/MET are transitional processes, we generated and validated a reporter cell line. Specifically, a far-red fluorescent protein was knocked-in in-frame with the mesenchymal gene marker VIMENTIN (VIM) in H2170 lung cancer cells. The vimentin reporter cells (VRCs) are a reliable model for studying EMT and MET showing cellular plasticity upon a series of stimulations. These cells are a robust platform to dissect the molecular mechanisms of these processes, and for drug discovery in vitro and in vivo in the future.

PEAR1 suppresses the proliferation of pulmonary microvascular endothelial cells via PI3K/AKT pathway in ALI model

BACKGROUND

Activation of the proliferation of pulmonary microvascular endothelial cells (PMVECs) is a key step in the recovery of the integrity of endothelial monolayer, which helps to alleviate acute lung injury (ALI). Platelet endothelial aggregation receptor-1 (PEAR1), expressed on endothelial cells, was reported to inhibit the proliferation of vascular endothelial cells and angiogenesis. However, little is known about its role and mechanism in vascular endothelial disorders in ALI.

OBJECTIVE

The aim of this study was to investigate the impact of PEAR1 on the proliferation of pulmonary microvascular endothelial cells in ALI.

METHODS

We tested the expression level of PEAR1 in the lungs of WT mice in ALI model induced by intestinal IR. Primary human pulmonary microvascular endothelial cells (HPMECs) were stimulated by 1 mg/L LPS in vitro. We synthesized siPEAR1 and Flag-PEAR1 plasmid to verify the role of PEAR1 on regulating the proliferation of HPMECs under LPS condition and to explore related signaling pathways.

RESULTS

The expression level of PEAR1 significantly increased in ALI induced by intestinal IR. PEAR1 knockdown enhanced the proliferation level of HPMECs, which, however, was inhibited by PEAR1 overexpression. PEAR1 knockdown activated PI3K/AKT pathway both in steady state and under LPS condition. PI3K inhibitor, LY294002, reversed the increasing proliferation level and cell progression of HPMECs induced by PEAR1 knockdown after LPS challenge.

CONCLUSIONS

PEAR1 acts as a negative regulator in the proliferation of HPMECs in ALI model via the PI3K/AKT pathway.

Variation of PEAR1 DNA methylation influences platelet and leukocyte function

BACKGROUND

Platelet-endothelial aggregation receptor 1 (PEAR-1) is a transmembrane receptor involved in platelet activation and megakaryopoiesis whose expression is driven by DNA methylation. PEAR1 variants were associated with differential platelet response to activation and cardiovascular outcomes. We aimed at investigating the link between PEAR1 methylation and platelet and leukocyte function markers in a family-based population.

RESULTS

We measured PEAR1 methylation in 605 Moli-family participants with available blood counts, plasma P-selectin and C-reactive protein, whole blood platelet P-selectin, and platelet-leukocyte mixed conjugate measurements. We performed principal component analysis (PCA) to identify groups of highly correlated CpG sites. We used linear mixed regression models (using age, gender, BMI, smoking, alcohol drinking, being a proband for family recruitment, being a member of myocardial infarction (MI) family as fixed effects, and family as a random effect) to evaluate associations between PEAR1 methylation and phenotypes. PEAR1 methylation Factor2, characterized by the previously identified megakaryocyte-specific CpG sites, was inversely associated with platelet-monocyte conjugates, P-selectin, and WBC counts, while positively associated with the platelet distribution width (PDW) and with leukocyte CD11b and L-selectin. Moreover, PEAR1 Factor2 methylation was negatively associated with INFLAscore, a low-grade inflammation score. The latter was partially mediated by the PEAR1 methylation effect on platelet variables. PEAR1 methylation association with WBC measurements and INFLAscore was confirmed in the independent cohort FLEMENGHO.

CONCLUSIONS

We report a significant link between epigenetic signatures in a platelet functional gene and inflammation-dependent platelet function variability measured in two independent cohorts.

Structural consequences of transforming growth factor beta-1 activation from near-therapeutic X-ray doses

Dissociation of transforming growth factor beta-1 (TGFβ-1) from the inhibitory protein latency-associated peptide (LAP) can occur from low doses of X-ray irradiation of the LAP-TGFβ-1 complex, resulting in the activation of TGFβ-1, and can have health-related consequences. Using the tools and knowledge developed in the study of radiation damage in the crystallographic setting, small-angle X-ray scattering (SAXS) and complementary techniques suggest an activation process that is initiated but not driven by the initial X-ray exposure. LAP is revealed to be extended when not bound to TGFβ-1 and has a different structural conformation compared to the bound state. These studies pave the way for the structural understanding of systems impacted at therapeutic X-ray doses and show the potential impact of radiation damage studies beyond their original intent.

Superantigenic Activation of Human Cardiac Mast Cells

B cell superantigens, also called immunoglobulin superantigens, bind to the variable regions of either the heavy or light chain of immunoglobulins mirroring the lymphocyte-activating properties of classical T cell superantigens. Protein A of Staphylococcus aureus, protein L of Peptostreptococcus magnus, and gp120 of HIV are typical immunoglobulin superantigens. Mast cells are immune cells expressing the high-affinity receptor for IgE (FcεRI) and are strategically located in the human heart, where they play a role in several cardiometabolic diseases. Here, we investigated whether immunoglobulin superantigens induced the activation of human heart mast cells (HHMCs). Protein A induced the de novo synthesis of cysteinyl leukotriene C₄ (LTC₄) from HHMCs through the interaction with IgE V_H3⁺ bound to FcεRI. Protein L stimulated the production of prostaglandin D₂ (PGD₂) from HHMCs through the interaction with κ light chains of IgE. HIV glycoprotein gp120 induced the release of preformed (histamine) and de novo synthesized mediators, such as cysteinyl leukotriene C₄ (LTC₄), angiogenic (VEGF-A), and lymphangiogenic (VEGF-C) factors by interacting with the V_H3 region of IgE. Collectively, our data indicate that bacterial and viral immunoglobulin superantigens can interact with different regions of IgE bound to FcεRI to induce the release of proinflammatory, angiogenic, and lymphangiogenic factors from human cardiac mast cells.

Understanding Platelets in Infectious and Allergic Lung Diseases

Emerging evidence suggests that platelets, cytoplasmic fragments derived from megakaryocytes, can no longer be considered just as mediators in hemostasis and coagulation processes, but as key modulators of immunity. Platelets have received increasing attention as the emergence of new methodologies has allowed the characterization of their components and functions in the immune continuum. Platelet activation in infectious and allergic lung diseases has been well documented and associated with bacterial infections reproduced in several animal models of pulmonary bacterial infections. Direct interactions between platelets and bacteria have been associated with increased pulmonary platelet accumulation, whereas bacterial-derived toxins have also been reported to modulate platelet function. Recently, platelets have been found extravascular in the lungs of patients with asthma, and in animal models of allergic lung inflammation. Their ability to interact with immune and endothelial cells and secrete immune mediators makes them one attractive target for biomarker identification that will help characterize their contribution to lung diseases. Here, we present an original review of the last advances in the platelet field with a focus on the contribution of platelets to respiratory infections and allergic-mediated diseases.

Epidermal growth factor-like repeats of SCUBE1 derived from platelets are critical for thrombus formation

Aims

SCUBE1 [signal peptide-CUB-epidermal growth factor (EGF) domain-containing protein 1], expressed in endothelial cells (ECs) and platelets, exists in soluble or membrane forms. We previously showed that soluble SCUBE1 is a biomarker for platelet activation and also an active participant of thrombosis. However, whether the adhesive module of its EGF-like repeats is essential and the specific contribution of SCUBE1 synthesized in ECs or platelets to thrombosis in vivo remain unclear.

Methods and results

We generated new mutant (Δ2) mice lacking the entire EGF-like repeats to evaluate the module’s functional importance during thrombogenesis in vivo. The Δ2 platelet-rich plasma showed markedly impaired platelet aggregation induced by agonists including adenosine diphosphate, collagen, the thrombin agonist PAR-4 peptide and the thromboxane A2 analogue U46619. Consistently, genetic ablation of the EGF-like repeats diminished arterial thrombosis and protected Δ2 mice against lethal thromboembolism. On flow chamber assay, whole blood isolated from Δ2 or wild-type (WT) mice pre-treated with blocking antibodies against the EGF-like repeats showed a significant decrease in platelet deposition and thrombus formation on collagen-coated surfaces under arterial shear rates. Moreover, we created animals expressing SCUBE1 only in ECs (S1-EC) or platelets (S1-PLT) by reciprocal bone-marrow transplantation between WT and Δ2 mice. The time of carotid arterial thrombosis induced by ferric chloride was normal in S1-PLT chimeric mice but much prolonged in S1-EC animals.

Conclusions

We demonstrate that platelet-derived SCUBE1 plays a critical role in arterial thrombosis via its adhesive EGF-like repeats in vivo and suggest targeting these adhesive motifs of SCUBE1 for potential anti-thrombotic strategy.

iTRAQ-based proteomic analysis of human umbilical vein endothelial cells with platelet endothelial aggregation receptor-1 knockdown

The disorders of hemostasis and coagulation were believed to be the main contributors to the pathogenesis of pulmonary thromboembolism (PTE), and platelets are the basic factors regulating hemostasis and coagulation and play important roles in the process of thrombosis. This study investigated the proteome of human umbilical vein endothelial cells (HUVECs) with platelet endothelial aggregation receptor-1 (PEAR1) knockdown using the isobaric tags for relative and absolute quantitation (iTRAQ) method and analyzed the role of differential abundance proteins (DAPs) in the regulation of platelets aggregation. Our results showed that the conditioned media-culturing HUVECs with PEAR1 knockdown partially suppressed the adenosine diphosphate (ADP)-induced platelet aggregation. The proteomics analysis was performed by using the iTRAQ technique, and a total of 215 DAPs (124 protein was upregulated and 91 protein were downregulated) were identified. The Gene Ontology (GO) enrichment analysis showed that proteins related to platelet α granule, adenosine triphosphate metabolic process, and endocytosis were significantly enriched. Further, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis also identified the significant enrichment of endocytosis-related pathways. The real-time polymerase chain reaction assay confirmed that the expression of P2Y₁₂ , mitochondrial carrier 2, NADH dehydrogenase (ubiquinone) iron-sulfur protein 3, and ubiquinol-cytochrome c reductase hinge protein are significantly downregulated in the HUVECs with PEAR1 knockdown. In conclusion, our in vitro results implicated that DAPs induced by PEAR1 knockdown might contribute to the platelet aggregation. Proteomic studies by employing GO enrichment and KEGG pathway analysis suggested that the potential effects of DAPs on platelet aggregation may be linked to the balance of ADP synthesis or degradation in mitochondria.

Synthetic glycopolymers and natural fucoidans cause human platelet aggregation via PEAR1 and GPIbα

Fucoidans are sulfated fucose-based polysaccharides that activate platelets and have pro- and anticoagulant effects; thus, they may have therapeutic value. In the present study, we show that 2 synthetic sulfated α-l-fucoside-pendant glycopolymers (with average monomeric units of 13 and 329) and natural fucoidans activate human platelets through a Src- and phosphatidylinositol 3-kinase (PI3K)-dependent and Syk-independent signaling cascade downstream of the platelet endothelial aggregation receptor 1 (PEAR1). Synthetic glycopolymers and natural fucoidan stimulate marked phosphorylation of PEAR1 and Akt, but not Syk. Platelet aggregation and Akt phosphorylation induced by natural fucoidan and synthetic glycopolymers are blocked by a monoclonal antibody to PEAR1. Direct binding of sulfated glycopolymers to epidermal like growth factor (EGF)-like repeat 13 of PEAR1 was shown by avidity-based extracellular protein interaction screen technology. In contrast, synthetic glycopolymers and natural fucoidans activate mouse platelets through a Src- and Syk-dependent pathway regulated by C-type lectin-like receptor 2 (CLEC-2) with only a minor role for PEAR1. Mouse platelets lacking the extracellular domain of GPIbα and human platelets treated with GPIbα-blocking antibodies display a reduced aggregation response to synthetic glycopolymers. We found that synthetic sulfated glycopolymers bind directly to GPIbα, substantiating that GPIbα facilitates the interaction of synthetic glycopolymers with CLEC-2 or PEAR1. Our results establish PEAR1 as the major signaling receptor for natural fucose-based polysaccharides and synthetic glycopolymers in human, but not in mouse, platelets. Sulfated α-l-fucoside-pendant glycopolymers are unique tools for further investigation of the physiological role of PEAR1 in platelets and beyond.

EGFR-Aurka Signaling Rescues Polarity and Regeneration Defects in Dystrophin-Deficient Muscle Stem Cells by Increasing Asymmetric Divisions

Loss of dystrophin expression in Duchenne muscular dystrophy (DMD) causes progressive degeneration of skeletal muscle, which is exacerbated by reduced self-renewing asymmetric divisions of muscle satellite cells. This, in turn, affects the production of myogenic precursors and impairs regeneration and suggests that increasing such divisions may be beneficial. Here, through a small-molecule screen, we identified epidermal growth factor receptor (EGFR) and Aurora kinase A (Aurka) as regulators of asymmetric satellite cell divisions. Inhibiting EGFR causes a substantial shift from asymmetric to symmetric division modes, whereas EGF treatment increases asymmetric divisions. EGFR activation acts through Aurka to orient mitotic centrosomes, and inhibiting Aurka blocks EGF stimulation-induced asymmetric division. In vivo EGF treatment markedly activates asymmetric divisions of dystrophin-deficient satellite cells in mdx mice, increasing progenitor numbers, enhancing regeneration, and restoring muscle strength. Therefore, activating an EGFR-dependent polarity pathway promotes functional rescue of dystrophin-deficient satellite cells and enhances muscle force generation.

Structural Modeling and in Silico Screening of Potential Small-Molecule Allosteric Agonists of a Glucagon-like Peptide 1 Receptor

The glucagon-like peptide 1 receptor (GLP-1R) belongs to the pharmaceutically important class B family of G-protein-coupled receptors (GPCRs), and its incretin peptide ligand GLP-1 analogs are adopted drugs for the treatment of type 2 diabetes. Despite remarkable antidiabetic effects, GLP-1 peptide-based drugs are limited by the need of injection. On the other hand, developing nonpeptidic small-molecule drugs targeting GLP-1R remains elusive. Here, we first constructed a three-dimensional structure model of the transmembrane (TM) domain of human GLP-1R using homology modeling and conformational sampling techniques. Next, a potential allosteric binding site on the TM domain was predicted computationally. In silico screening of druglike compounds against this predicted allosteric site has identified nine compounds as potential GLP-1R agonists. The independent agonistic activity of two compounds was subsequently confirmed using a cAMP response element-based luciferase reporting system. One compound was also shown to stimulate insulin secretion through in vitro assay. In addition, this compound synergized with GLP-1 to activate human GLP-1R. These results demonstrated that allosteric regulation potentially exists in GLP-1R and can be exploited for developing small-molecule agonists. The success of this work will help pave the way for small-molecule drug discovery targeting other class B GPCRs through allosteric regulations.

CADASIL brain vessels show a HTRA1 loss-of-function profile

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and a phenotypically similar recessive condition (CARASIL) have emerged as important genetic model diseases for studying the molecular pathomechanisms of cerebral small vessel disease (SVD). CADASIL, the most frequent and intensely explored monogenic SVD, is characterized by a severe pathology in the cerebral vasculature including the mutation-induced aggregation of the Notch3 extracellular domain (Notch3ECD) and the formation of protein deposits of insufficiently determined composition in vessel walls. To identify key molecules and pathways involved in this process, we quantitatively determined the brain vessel proteome from CADASIL patient and control autopsy samples (n = 6 for each group), obtaining 95 proteins with significantly increased abundance. Intriguingly, high-temperature requirement protein A1 (HTRA1), the extracellular protease mutated in CARASIL, was found to be strongly enriched (4.9-fold, p = 1.6 × 10-3) and to colocalize with Notch3ECD deposits in patient vessels suggesting a sequestration process. Furthermore, the presence of increased levels of several HTRA1 substrates in the CADASIL proteome was compatible with their reduced degradation as consequence of a loss of HTRA1 activity. Indeed, a comparison with the brain vessel proteome of HTRA1 knockout mice (n = 5) revealed a highly significant overlap of 18 enriched proteins (p = 2.2 × 10-16), primarily representing secreted and extracellular matrix factors. Several of them were shown to be processed by HTRA1 in an in vitro proteolysis assay identifying them as novel substrates. Our study provides evidence for a loss of HTRA1 function as a critical step in the development of CADASIL pathology linking the molecular mechanisms of two distinct SVD forms.