Cell Surface Expression Of Receptors Research Articles

Fluorescence labeling strategies for the study of ion channel and receptor cell surface expression: A comprehensive toolkit for extracellular labeling of TRPV1.

Regulation of ion channel expression on the plasma membrane is a major determinant of neuronal excitability, and identifying the underlying mechanisms of this expression is critical to our understanding of neurons. A critical aspect of measuring changes in ion channel expression is uniquely identifying ion channels located on the cell surface. To accomplish this goal we demonstrate two orthogonal strategies to label extracellular sites of the ion channel TRPV1 that minimally perturb the function of the channel: 1) We use the amber codon suppression technique to introduce a non-canonical amino acid (ncAA) with tetrazine click chemistry compatible with a trans-cyclooctene coupled fluorescent dye. 2) By inserting the circularly permutated HaloTag (cpHaloTag) in an extracellular loop of TRPV1, we incorporate a click-chemistry site for a chloroalkane-linked fluorescent dye of our choosing. Optimization of ncAA insertion sites was accomplished by screening residue positions between the S1 and S2 transmembrane domains with elevated missense variants in the human population, and we identified T468 as a rapid labeling site (∼5 minutes) based on functional as well as biochemical assays in HEK293T/17 cells. After several rounds of adapting the linker lengths and backbone placement of cpHaloTag on the extracellular side of TRPV1, our efforts led to a channel construct that robustly expressed as a fully functional TRPV1exCellHalo fusion with intact wild-type gating properties. The TRPV1exCellHalo construct was used in a single molecule experiment to track TRPV1 on the cell surface and validate studies that show decreased mobility of the channel upon activation. The success of these extracellular label TRPV1 (exCellTRPV1) constructs as tools to track surface expression of the channel will shed significant light on the mechanisms regulating expression and provide a general scheme to introduce similar modifications to other cell surface receptors.

Immunophenotypic Evaluation of Circulating Monocyte Subsets in Beta Thalassemia Major Patients

Abstract Background β-thalassemia is a major public health problem in Egypt with particularly high incidence due to strong cultural preference for consanguineous marriages, and the high carrier rate. Iron overload, which is caused by increased gut iron absorption secondary to ineffective erythropoiesis, and regular blood transfusion is linked to accumulation within different organs with subsequent organ dysfunction. Monocytes are important lineages of innate immunity which activate the adaptive immune response and play a pivotal role in the host response to pathogens. Human blood monocyte subsets classification is based on the expression of CD14 and CD16 cell surface receptors. Aim of the Work To evaluate the circulating monocyte subsets in β-thalassemia major (β-TM) patients and its potential role in prediction of iron overload and chronic inflammation in β- thalassemia major patients. Patients and Methods A Case-Control study conducted on 40 previously diagnosed beta thalassemia major patients attending the outpatient clinic of Ain Shams University Pediatric Hospital, and 20 age and sex matched healthy control subjects. CBC, iron profile, CRP and immunophenotyping for monocyte subsets classification were done. Results Non classical monocytes were found statistically significantly higher in thalassemic patients especially in those with serum ferritin level < 1000 ng/ml (P value < 0.01). In addition, classical monocytes were found to be statistically significantly lower among the patients’ group (P value < 0.01). A negative correlation was found between intermediate monocytes and Transferrin saturation percent (TS%) suggesting its protective role in iron overload thalassemia patients. By using ROC curve, non- classical monocytes predicted ferritin < 1000 ng/ml at a cutoff point of 17.8 % and 0.05 x 10∧9/L for relative and absolute counts respectively. Conclusion All monocyte subsets proposed to have role in predicting iron overload and chronic inflammation β-TM patients. We recommend further studies on β-TM patients with the engagement of activity assays of monocyte subsets to clarify the co-regulatory role in iron hemostasis and chronic inflammation.

Impaired Sonic Hedgehog Responsiveness of Induced Pluripotent Stem Cell-Derived Floor Plate Cells Carrying the LRRK2-I1371V Mutation Contributes to the Ontogenic Origin of Lower Dopaminergic Neuron Yield.

Lower population of dopaminergic (DA) neurons is known to increase susceptibility to Parkinson's disease (PD), and our earlier study showed a lower yield of DA neurons in Leucine-Rich Repeat Kinase Isoleucine 1371 Valine (LRRK2-I1371V) mutation-carrying PD patient-derived induced Pluripotent Stem Cells (iPSCs). Although the role of Sonic Hedgehog (SHH) in DA neurogenesis of floor plate cells (FPCs) is known, the effect of LRRK2 mutations on SHH responsiveness of FPCs impacting DA neuronal yield has not been studied. We investigated SHH responsiveness of FPCs derived from LRRK2-I1371V PD patient iPSCs with regard to the expression of SHH receptors Patched1 (Ptch1) and Smoothened (Smo), in conjunction with nuclear Gli1 (glioma-associated oncogene 1) expression, intracellular Ca2+ rise, and cytosolic cyclic adenosine monophosphate (cAMP) levels upon SHH induction. In addition, we examined the mechanistic link with LRRK2-I1371V gain-of-function by assessing membrane fluidity and Rab8A and Rab10 phosphorylation in SH-SY5Y cells and healthy control (HC) FPCs overexpressing LRRK2-I1371V as well as FPCs. Although total expression of Ptch1 and Smo was comparable, receptor expression on cell surface was significantly lower in LRRK2-I1371V FPCs than in HC FPCs, with distinctly lower nuclear expression of the downstream transcription factor Gli1. HC-FPCs transfected with LRRK2-I1371V exhibited a similarly reduced cell surface expression of Ptch1 and Smo. Intracellular Ca2+ response was significantly lower with corresponding elevated cAMP levels in LRRK2-I1371V FPCs compared with HC FPCs upon SHH stimulation. The LRRK2-I1371V mutant FPCs and LRRK2-I1371V-transfected SH-SY5Y and HC FPCs too exhibited higher autophosphorylation of phospho LRRK2 (pLRRK2) serine1292 and serine935, as well as substrate phosphorylation of Rab8A and Rab10. Concurrent increase in membrane fluidity, accompanied by a decrease in membrane cholesterol, and lower expression of lipid raft marker caveolin 1 were also observed in them. These findings suggest that impaired SHH responsiveness of LRRK2-I1371V PD FPCs indeed leads to lower yield of DA neurons during ontogeny. Reduced cell surface expression of SHH receptors is influenced by alteration in membrane fluidity owing to the increased substrate phosphorylation of Rab8A and reduced membrane protein trafficking due to pRab10, both results of the LRRK2-I1371V mutation.

Circadian Regulation of Leishmania Parasite Internalisation in Macrophages and Downstream Cellular Events.

Leishmania spp. parasites use macrophages as a host cell during infection. As a result, macrophages have a dual role: clearing the parasite as well as acting as host cells. Recently, studies have shown that macrophages harbour circadian clocks, which affect many of their functions such as phagocytosis, receptor expression and cytokine release. Interestingly, Leishmania major infection in hosts was also shown to be under circadian control. Therefore, we decided to investigate what underlies the rhythms of L. major infection within macrophages. Using a culture model of infection of bone marrow-derived macrophages with L. major promastigotes, we show that the parasites are internalised into macrophages with a 24-h variation dependent on a functional circadian clock in the cells. This was associated with a variation in the number of parasites per macrophage. The cell surface expression of parasite receptors was not controlled by the cells' circadian clock. In contrast, the expression of the components of the endocytic pathway, EEA1 and LC3b, varied according to the time of infection. This was paralleled by variations in parasite-induced ROS production as well as cytokine tumour necrosis factor α. In summary, we have uncovered a time-dependent regulation of the internalisation of L. major promastigotes in macrophages, controlled by the circadian clock in these cells, as well as subsequent cellular events in the endocytic pathway, intracellular signalling and cytokine production.

Immune Cell Migration to Cancer.

Immune cell migration is required for the development of an effective and robust immune response. This elegant process is regulated by both cellular and environmental factors, with variables such as immune cell state, anatomical location, and disease state that govern differences in migration patterns. In all cases, a major factor is the expression of cell surface receptors and their cognate ligands. Rapid adaptation to environmental conditions partly depends on intrinsic cellular immune factors that affect a cell's ability to adjust to new environment. In this review, we discuss both myeloid and lymphoid cells and outline key determinants that govern immune cell migration, including molecules required for immune cell adhesion, modes of migration, chemotaxis, and specific chemokine signaling. Furthermore, we summarize tumor-specific elements that contribute to immune cell trafficking to cancer, while also exploring microenvironment factors that can alter these cellular dynamics within the tumor in both a pro and antitumor fashion. Specifically, we highlight the importance of the secretome in these later aspects. This review considers a myriad of factors that impact immune cell trajectory in cancer. We aim to highlight the immunotherapeutic targets that can be harnessed to achieve controlled immune trafficking to and within tumors.

Neutrophils impaired by anti-galectin-3 antibodies elicit inflammation of endothelial cells to aggregate the development of lupus cutaneous vasculitis.

To investigate whether the interplay of anti-galectin-3 antibodies (anti-Gal3 Abs) with neutrophils contributes to the development of lupus cutaneous vasculitis. Enzyme-linked immunosorbent assay was used to determine the serum level of anti-Gal3 Abs in lupus patients. Flow cytometry, quantitative PCR and western blot were performed to investigate the expression of cell surface receptors, proinflammatory cytokines and signalling molecules in neutrophils stimulated by serum from lupus patients or healthy controls (HCs) or anti-Gal3 Ab, respectively. Immunofluorescence was performed to visualise the formation of neutrophil extracellular traps (NETs). Human umbilical vein endothelial cells were co-cultured with the supernatants from neutrophils stimulated by anti-Gal3 Ab, and cytokine production was measured at mRNA and protein levels. Immunohistochemistry was adopted to reveal the distribution of Gal3, cytokines and myeloperoxidase within lupus skin lesions. Serum levels of anti-Gal3 Abs were negatively correlated with peripheral counts of neutrophils. Anti-Gal3 Abs positive sera from SLE patients accelerated neutrophil death, altered cell phenotype and promoted formation of NETs with the involvement of p38 MAPK pathway. Supernatants collected from neutrophils co-cultured with anti-Gal3 Ab provoked endothelial cells to produce cytokines such as IL-1, ICAM-1, SELE and particularly IL-6. Consistently, IL-6 was higher in SLE patients with anti-Gal3 Ab positive sera and enriched in the area of vascular inflammation together with enhanced expression of Gal3 protein and infiltration of neutrophils. Overall, these findings suggested that neutrophils were crucial mediators in anti-Gal3 Ab induced lupus cutaneous vasculitis.

Mechano-sensitivity of β2-adrenoceptors enhances constitutive activation of cAMP generation that is inhibited by inverse agonists

The concept of agonist-independent signalling that can be attenuated by inverse agonists is a fundamental element of the cubic ternary complex model of G protein-coupled receptor (GPCR) activation. This model shows how a GPCR can exist in two conformational states in the absence of ligands; an inactive R state and an active R* state that differ in their affinities for agonists, inverse agonists, and G-protein alpha subunits. The proportion of R* receptors that exist in the absence of agonists determines the level of constitutive receptor activity. In this study we demonstrate that mechanical stimulation can induce β2-adrenoceptor agonist-independent Gs-mediated cAMP signalling that is sensitive to inhibition by inverse agonists such as ICI-118551 and propranolol. The size of the mechano-sensitive response is dependent on the cell surface receptor expression level in HEK293G cells, is still observed in a ligand-binding deficient D113A mutant β2-adrenoceptor and can be attenuated by site-directed mutagenesis of the extracellular N-glycosylation sites on the N-terminus and second extracellular loop of the β2-adrenoceptor. Similar mechano-sensitive agonist-independent responses are observed in HEK293G cells overexpressing the A2A-adenosine receptor. These data provide new insights into how agonist-independent constitutive receptor activity can be enhanced by mechanical stimulation and regulated by inverse agonists.

Abstract 4402: A genomic insertion/deletion variant activates immune escape and tumor promoting programs in breast cancer

Abstract Purpose: Despite all the knowledge we have concerning cancer cells’ immunesuppressive ability, we still don’t understand whether the mechanisms upregulatingimmune suppression in cancer cells are patient specific. This information is critical forthe generation of tailored treatments that recruit the immune system for the eradicationof cancer disease. In the past, we showed that super-enhancers, composed of cluster ofenhancers spanning over long genomic regions characterized by having potent generegulatory activity, are critical for the upregulation of immune suppressive genes,including CD47, within the tumor. Recently we found a DNA insertion/deletion variant (8bp in size) within a super-enhancer located between the CD47 and Linc00636 genes,that is present more often in European (53%) than Asian (12%) populations and whichassociates with breast cancer. Moreover, sequence analyses of patient-derived breasttumors (44) and gynecological tumor samples (23) demonstrated a significantassociation of this insert with breast cancer and not with gynecological cancer. Thus, wehypothesize that the insertion variant regulates genes that drive immune escape andbreast cancer specifically in patient populations that carry the insert version. Methods: To test this, we CRISPR deleted the variant’s insertion and CRISPR-VP64induced its activation and quantified its effect on target genes and encoded proteinsusing high throughput RNA sequencing and immunofluorescence flow cytometryanalyses respectively. Results: CRISPR-VP64 induction of the 8bp insertion confirmed that the insertion issufficient to regulate gene expression of CD47 and of an anti-tumor, long intergenicnon-coding RNA (Linc00636) in breast cancer cells. Furthermore, we observed thatCRISPR deletion of the 8bp insertion increases CD47 levels, while dramaticallyincreasing expression of Linc00636 and reducing the expression of CD44, CXCL14,MUC1 genes involved in invasion and migration. Our work shows that the insertion ofan 8bp is responsible for stabilizing upregulation of CD47 (an immune suppressivesignal), downregulating Linc00636 (a modulator of tumor metastasis), and upregulating,as a result, the expression of cell surface receptors involved in metastasis andtumorigenesis. Conclusions: Here we found a genomic insert within a super-enhancer that unleashesthe upregulation of Linc00636 and of a program that promotes breast cancer, mostlikely in populations of patients carrying this variant. Our findings are important tounderstand patient specific genomic bifunctional modulators of immune suppressionand tumor progression for the design of more personalized treatments geared towardprecision medicine. Citation Format: Paola Betancur, Carolina DiBenedetto, Daniza Diane Acenas, Anthony Rodriguez, Alysia Thach. A genomic insertion/deletion variant activates immune escape and tumor promoting programs in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4402.

Abstract 46: Mechanisms and impact of bystander killing by CAR T cells

Abstract While CD19-directed chimeric antigen receptor (CAR) T cell therapy has improved outcomes of patients with relapsed/refractory diffuse large B cell lymphoma (r/r DLBCL), a majority will suffer disease relapse following CAR T cell infusion. Therefore, understanding mechanisms of CAR T cell killing is critical to enhance therapeutic efficacy. Cytolysis of CAR T cell targets presumably involves recognition of CD19 antigen by the CAR followed by activation of the granzyme/perforin axis. However, bystander elimination of CD19-negative lymphoma cells by CAR T cells has been reported, indicating that an alternative pathway may be required for optimal killing. Through in-depth phenotyping of a large panel of human DLBCLs and in vitro killing assays, we observed that CD19 expression levels on DLBCL cells and vulnerability to CAR T cell killing were weakly correlated. Conversely, cell surface expression of the death receptor, FAS, on DLBCL cells was strongly associated with susceptibility to CAR T cell killing. Although FAS expression across DLBCL cell lines varied, it could be broadly enhanced following exposure to IFNγ. Potent CAR T cell-mediated cytolysis of CD19-negative, Fas-positive murine DLBCL cells required the presence of CD19-positive lymphoma cells in the culture. CRISPR/Cas9 targeting was employed to delete FAS and/or CD19 in isogenic human DLBCL cells to generate CD19+FAS+, CD19+FAS−, CD19−FAS+, and CD19−FAS− subsets, which enabled us to define the extent to which CD19 engagement by the CAR was required to affect killing via FAS. When CAR T cells were co-cultured with equal numbers of the four gene-modified DLBCL cells described above, CD19+FAS+ DLBCL cells were killed most effectively, followed by CD19+FAS− DLBCL cells, and CD19−FAS+ DLBCL cells. Double-negative DLBCL cells were poorly killed. This result suggested that CD19 engagement by the CAR was required for optimal DLBCL cell killing via FAS, and that CD19 and FAS need not necessarily be engaged on the same target cell. Future studies will determine if Fas/FasL interactions can be exploited by overexpression of FasL in CAR T cells and examination of DLBCL killing in vitro and in vivo. Citation Format: Joanna Chorazeczewski, Lishi Xie, Xiufen Chen, Sidney Wang, Justin Kline. Mechanisms and impact of bystander killing by CAR T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 46.

Unraveling the molecular interactions between α7 nicotinic receptor and a RIC3 variant associated with backward speech

Recent work putatively linked a rare genetic variant of the chaperone Resistant to Inhibitors of acetylcholinesterase (RIC3) (NM_024557.4:c.262G > A, NP_078833.3:p.G88R) to a unique ability to speak backwards, a language skill that is associated with exceptional working memory capacity. RIC3 is important for the folding, maturation, and functional expression of α7 nicotinic acetylcholine receptors (nAChR). We compared and contrasted the effects of RIC3G88R on assembly, cell surface expression, and function of human α7 receptors using fluorescent protein tagged α7 nAChR and Förster resonance energy transfer (FRET) microscopy imaging in combination with functional assays and 125I-α-bungarotoxin binding. As expected, the wild-type RIC3 protein was found to increase both cell surface and functional expression of α7 receptors. In contrast, the variant form of RIC3 decreased both. FRET analysis showed that RICG88R increased the interactions between RIC3 and α7 protein in the endoplasmic reticulum. These results provide interesting and novel data to show that a RIC3 variant alters the interaction of RIC3 and α7, which translates to decreased cell surface and functional expression of α7 nAChR.

Primary Human M2 Macrophage Subtypes Are Distinguishable by Aqueous Metabolite Profiles.

The complexity of macrophage (MΦ) plasticity and polarization states, which include classically activated pro-inflammatory (M1) and alternatively activated anti-inflammatory (M2) MΦ phenotypes, is becoming increasingly appreciated. Within the M2 MΦ polarization state, M2a, M2b, M2c, and M2d MΦ subcategories have been defined based on their expression of specific cell surface receptors, secreted cytokines, and specialized immune effector functions. The importance of immunometabolic networks in mediating the function and regulation of MΦ immune responses is also being increasingly recognized, although the exact mechanisms and extent of metabolic modulation of MΦ subtype phenotypes and functions remain incompletely understood. In this study, proton (1H) nuclear magnetic resonance (NMR) metabolomics was employed to determine the polar metabolomes of M2 MΦ subtypes and to investigate the relationship between aqueous metabolite profiles and M2 MΦ functional phenotypes. Results from this study demonstrate that M2a MΦs are most distinct from M2b, M2c, and M2d MΦ subtypes, and that M2b MΦs display several metabolic traits associated with an M1-like MΦ phenotype. The significance of metabolome differences for metabolites implicated in glycolysis, the tricarboxylic acid (TCA) cycle, phospholipid metabolism, and creatine-phosphocreatine cycling is discussed. Altogether, this study provides biochemical insights into the role of metabolism in mediating the specialized effector functions of distinct M2 MΦ subtypes and supports the concept of a continuum of macrophage activation states rather than two well-separated and functionally distinct M1/M2 MΦ classes, as originally proposed within a classical M1/M2 MΦ framework.

Exploiting spatiotemporal regulation of FZD5 during neural patterning for efficient ventral midbrain specification.

The Wnt/β-catenin signaling governs anterior-posterior neural patterning during development. Current human pluripotent stem cell (hPSC) differentiation protocols use a GSK3 inhibitor to activate Wnt signaling to promote posterior neural fate specification. However, GSK3 is a pleiotropic kinase involved in multiple signaling pathways and, as GSK3 inhibition occurs downstream in the signaling cascade, it bypasses potential opportunities for achieving specificity or regulation at the receptor level. Additionally, the specific roles of individual FZD receptors in anterior-posterior patterning are poorly understood. Here, we have characterized the cell surface expression of FZD receptors in neural progenitor cells with different regional identity. Our data reveal unique upregulation of FZD5 expression in anterior neural progenitors, and this expression is downregulated as cells adopt a posterior fate. This spatial regulation of FZD expression constitutes a previously unreported regulatory mechanism that adjusts the levels of β-catenin signaling along the anterior-posterior axis and possibly contributes to midbrain-hindbrain boundary formation. Stimulation of Wnt/β-catenin signaling in hPSCs, using a tetravalent antibody that selectively triggers FZD5 and LRP6 clustering, leads to midbrain progenitor differentiation and gives rise to functional dopaminergic neurons in vitro and in vivo.

IMMUNOLOGICAL FEATURES OF COVID-19 IN PATIENTS WITH NEUROPSYCHIATRIC SYMPTOMS AND HHV-6-INFECTION

SARS-CoV-2 infection in most cases is characterised by mild symptoms of fever, tiredness and dry cough. Coronaviruses can also induce cognitive, emotional, neurovegetative and behavioral dysregulation due to direct neurological injury through hypoxic damage and neuroinvasion. Most SARS-CoV-2 infections resolve within two weeks. However, the infection, which is characterized by neurological and neuropsychiatric symptoms, may last longer than 12 weeks. This phenomenon has been termed as Long COVID (LC) – a multisystemic condition, associated with acute phase disease severities. Several hypotheses for its pathogenesis have been suggested, including immune dysregulation with or without reactivation of herpesviruses. The inflammation is central to pathogenesis of psychiatric symptoms in COVID-19 patients, which is often associated with presence of neural autoantibodies.
 The following changes are established of innate immunity in patients with SARS-CoV-2 infection and long COVID: 1) cytokine storm, which manifests itself in high concentration of proinflammatory cytokines and chemokines (IFN-β, IFN-λ1, IFN-γ, CXCL9, CXCL10, IL-8, IL-1α/β, IP-10, MCP-1); 2) elevated level C-reactive protein; 3) decreased number of NK, NKT cells and its exhaustion; 4) lower expression of NKG2C, upregulation of checkpoint receptors (LAG3, TIGIT and TIM3) on NK cells; 5) poor interacting between monocytes, infectious agents and Tolllike receptor (TLR) ligands; 6) reinforced products of thromboxane-A2, resulting in increased platelet aggregation, which mediate thrombus formation. It was also found in such patients the changes of adaptive immunity: 1) T cell alterations, including exhausted T cells; 2) reduced CD4+ and CD8+ effector memory cell numbers, which mainly express PD-1, CTLA-4, TIGIT and Tim-3; 3) a lack of naive T and B cells; 4) increases in the numbers of IL-4- and IL-6-secreting CD4+ T cells; 5) higher expression of cytotoxic granules (GrA, GrB, perforin) on CD8+ T cells.
 The exact mechanisms underlying the immune response after SARS-CoV-2 infection remain unclear. The count of helper T cells, regulatory T cells and memory T cells are all diminished in severe COVID- 19 cases, though Th1 and Th2 cytokine levels remain high. T cell activation (indicated by CD38 and HLA-DR) occur during severe COVID-19. Besides, T cells are overactivated in COVID-19 patients, leading to cytokine storm, and decreased Treg cells are a reason for severe disease. A subset of T cell expressed at the same time both: T cell immunoglobulin and mucin domain-3 (Tim-3) and programmed death-1 (PD-1).
 The overproduction of several inflammatory cytokines, overactivated and exhausted T cells, overstimulation of immune system and loss of self-tolerance alone can cause the production of autoantibodies. In addition, are activated the extrafollicular B cells in conjunction with autoantibody-secreting B cells. As seen in COVID-19 patients with autoantibodies and autoreactive CD4+ and CD8+ cells, probably promotes the development of neural autoantibody-associated psychiatric disease. The neural autoantibodies probably promote the development of psychiatric disease according to such pathomechanisms: 1) molecular mimicry: 2) NETs; 3) altered blood-brain barrier permeability; 4) coagulopathy and endothelial dysfunction (brain microhaemorrhages); 5) neuronal injury and apoptosis; 6) chronic hypoxia; 7) oxidative stress.
 Some features of COVID-19 resemble clinical diseases that accompany certain acute and chronic viral diseases, including diseases caused by HHV-6. Virus HHV-6 act in the following ways: 1) downregulation of CD3; 2) induction of IL-10-producing T-regulatory type 1 cells; 3) inhibition of IFN-β, IL-2, IL-12, and molecules MHC class I production; 4) immunomodulation – alterations in cell surface receptor expression and cytokine/chemokine production. Infection with SARS-CoV-2 causes overproduction of inflammatory cytokines that activate the inflammatory cascade. The hyperinflammatory processes in COVID-19 patients reactivate latent HHV-6, and that this is related to the inflammatory status of the patient. HHV-6 infects a broad array of immune and non-immune cell types and may introduce changes in T cell expression profiles and differential proliferation rates. The subclinical reactivation HHV-6 may affect the degree or severity of the SARS-CoV-2 infection. The severity of the course of the SARS-CoV-2 infection against the background of reactivation of HHV-6 threatens the formation of immunopathological syndromes, first of all is autoimmune syndrome. Long COVID could be induced by different mechanisms, including viral persistence that leads to disorders of immune response regulation, the release of superantigens that overactivate the immune system, destroys the blood-brain barriers which collectively may result in autoimmunity and polyautoimmunity, including neuroautoimmunity. This process was accompanied by the production of autoantibodies against thyroglobulin, thyroid peroxidase, insulin, double-stranded DNA, topoisomerase 1, glomerular basement membrane, and myoloperoxidase, which are detected in many autoimmune diseases. The production of antibodies against autoantigens that are detected mainly in polyautoimmunity through a completely new mechanism which involves the disruption of central tolerance Therefore, neuropsychiatric disorders in patients who have experienced moderate and severe forms of the course of COVID-19 are in the vast majority caused by deep immune changes and concominant lymphotropic/ neurotropic infection (HHV-6). The depth of disorders is often associated with autoimmunity to neuronal and other autoantigens.

TLR2 and TLR9 Blockade Using Specific Intrabodies Inhibits Inflammation-Mediated Pancreatic Cancer Cell Growth.

Pancreatic cancer (pancreatic ductal adenocarcinoma, PDAC) remains a deadly cancer worldwide with a need for new therapeutic approaches. A dysregulation in the equilibrium between pro- and anti-inflammatory responses with a predominant immunosuppressive inflammatory reaction in advanced stage tumors seem to contribute to tumor growth and metastasis. The current therapies do not include strategies against pro-tumorigenic inflammation in cancer patients. We have shown that the upregulated cell surface expression of Toll-like Receptor (TLR) 2 and of TLR9 inside PDAC cells maintain chronic inflammatory responses, support chemotherapeutic resistance, and mediate tumor progression in human pancreatic cancer. We further demonstrated intracellular TLR2 and TLR9 targeting using specific intrabodies, which resulted in downregulated inflammatory signaling. In this study, we tested, for the first time, an intrabody-mediated TLR blockade in human TLR2- and TLR9-expressing pancreatic cancer cells for its effects on inflammatory signaling-mediated tumor growth. Newly designed anti-TLR2- and anti-TLR9-specific intrabodies inhibited PDAC growth. Co-expression analysis of the intrabodies and corresponding human TLRs showed efficient retention and accumulation of both intrabodies within the endoplasmic reticulum (ER), while co-immunoprecipitation studies indicated both intrabodies interacting with their cognate TLR antigen within the pancreatic cancer cells. Cancer cells with attenuated proliferation expressing accumulated TLR2 and TRL9 intrabodies demonstrated reduced STAT3 phosphorylation signaling, while apoptotic markers Caspases 3 and 8 were upregulated. To conclude, our results demonstrate the TLR2 and TLR9-specific intrabody-mediated signaling pathway inhibition of autoregulatory inflammation inside cancer cells and their proliferation, resulting in the suppression of pancreatic tumor cell growth. These findings underscore the potential of specific intrabody-mediated TLR inhibition in the ER relevant for tumor growth inhibition and open up a new therapeutic intervention strategy for the treatment of pancreatic cancer.

Selective Cell-Surface Expression of Triheteromeric NMDA Receptors.

NMDA-type ionotropic glutamate receptors are critically involved in many brain functions and are implicated in a variety of brain disorders. Seven NMDA receptor subunits exist (GluN1, GluN2A-D, and GluN3A-B) that assemble into tetrameric receptor subtypes with distinct functional properties and physiological roles. The majority NMDA receptors are composed of two GluN1 and two GluN2 subunits, which can assemble into four diheteromeric receptors subtypes composed of GluN1 and one type of GluN2 subunit (e.g., GluN1/2A), and presumably also six triheteromeric receptor subtypes composed of GluN1 and two different GluN2 subunits (e.g., GluN1/2A/2B). Furthermore, the GluN1 subunit exists as eight splice variants (e.g., GluN1-1a and GluN1-1b isoforms), and two different GluN1 isoforms can co-assemble to also form triheteromeric NMDA receptors (e.g., GluN1-1a/1b/2A). Here, we describe a method to faithfully express triheteromeric NMDA receptors in heterologous expression systems by controlling the identity of two of the four subunits. This method overcomes the problem that co-expression of three different NMDA receptor subunits generates two distinct diheteromeric receptor subtypes as well as one triheteromeric receptor subtype, thereby confounding studies that require a homogenous population of triheteromeric NMDA receptors. The method has been applied to selectively express recombinant triheteromeric GluN1/2A/2B, GluN1/2A/2C, GluN1/2B/2D, GluN1-1a/GluN1-1b/2A, GluN1-1a/GluN1-1b/2B receptors with negligible co-expression of the respective diheteromeric receptor subtypes. This method therefore enables quantitative evaluation of functional and pharmacological properties of triheteromeric NMDA receptors, some of which are abundant NMDA receptor subtypes in the adult brain.

Functional Characterization of Novel MC4R Variants Identified in Two Unrelated Patients with Morbid Obesity in Qatar.

The leptin-melanocortin pathway is pivotal in appetite and energy homeostasis. Pathogenic variants in genes involved in this pathway lead to severe early-onset monogenic obesity (MO). The MC4R gene plays a central role in leptin-melanocortin signaling, and heterozygous variants in this gene are the most common cause of MO. A targeted gene panel consisting of 52 obesity-related genes was used to screen for variants associated with obesity. Variants were analyzed and filtered to identify potential disease-causing activity and validated using Sanger sequencing. We identified two novel heterozygous variants, c.253A>G p.Ser85Gly and c.802T>C p.Tyr268His, in the MC4R gene in two unrelated patients with morbid obesity and evaluated the functional impact of these variants. The impact of the variants on the MC4R gene was assessed using in silico prediction tools and molecular dynamics simulation. To further study the pathogenicity of the identified variants, GT1-7 cells were transfected with plasmid DNA encoding either wild-type or mutant MC4R variants. The effects of allelic variations in the MC4R gene on cAMP synthesis, MC4R protein level, and activation of PKA, ERB, and CREB signaling pathways in both stimulated and unstimulated ɑ-MSH paradigms were determined for their functional implications. In silico analysis suggested that the variants destabilized the MC4R structure and affected the overall dynamics of the MC4R protein, possibly leading to intracellular receptor retention. In vitro analysis of the functional impact of these variants showed a significant reduction in cell surface receptor expression and impaired extracellular ligand binding activity, leading to reduced cAMP production. Our analysis shows that the variants do not affect total protein expression; however, they are predicted to affect the post-translational localization of the MC4R protein to the cell surface and impair downstream signaling cascades such as PKA, ERK, and CREB signaling pathways. This finding might help our patients to benefit from the novel therapeutic advances for monogenic forms of obesity.

Amygdalin Improves Allergic Asthma via the Thymic Stromal Lymphopoietin–dendritic Cell–OX40 Ligand Axis in a Mouse Model

Asthma, characterized by persistent inflammation and increased sensitivity of the airway, is the most common chronic condition among children. Novel, safe, and reliable treatment strategies are the focus of current research on pediatric asthma. Amygdalin, mainly present in bitter almonds, has anti-inflammatory and immunoregulatory potential, but its effect on asthma remains uninvestigated. Here, the impact of amygdalin on the thymic stromal lymphopoietin (TSLP)–dendritic cell (DC)–OX40L axis was investigated.
 A BALB/c mouse model for allergic asthma was established using the ovalbumin-sensitization method. Amygdalin treatment was administered between days 21 and 27 of the protocol. Cell numbers and hematoxylin and eosin (H&E) staining in bronchoalveolar lavage fluid (BALF) were used to observe the impact of amygdalin on airway inflammation. TSLP, IL-4, IL-5, IL-13, and IFN-γ concentrations were determined via Enzyme-linked immunosorbent assay (ELISA). TSLP, GATA-3, and T-bet proteins were measured using western blotting. Cell-surface receptor expression on DCs (MHC II, CD80, and CD86) was assessed via flow cytometry. OX40L mRNA and protein levels were detected using western blotting and qRT-PCR, respectively.
 Amygdalin treatment attenuated airway inflammation decreased BALF TSLP levels, inhibited DC maturation, restrained TSLP-induced DC surface marker expression (MHCII, CD80, and CD86), and further decreased OX40L levels in activated DCs. This occurred together with decreased Th2 cytokine levels (IL-4, IL-5, and IL-13) and GATA3 expression, whereas Th1 cytokine (IFN-γ) levels and T-bet expression increased.
 Amygdalin thus regulates the Th1/Th2 balance through the TSLP–DC–OX40L axis to participate in inflammation development in the airways, providing a basis for potential allergic asthma treatments.

The injured monocyte: The link to chronic critical illness and mortality following injury.

This study aimed to understand the altered innate immune response in severely injured patients leading to chronic critical illness (CCI). Specifically, it focused on characterizing the monocyte populations and their correlation with CCI development and long-term complications. Over a 3-year period, we monitored patients with severe injuries for up to 1-year postinjury. Chronic critical illness was defined as an ICU stay exceeding 14 days with persistent organ failure. Blood samples were collected on Days 1 and 5 for monocyte phenotypic expression analysis using cytometry by time flight. The monocyte subpopulations studied were classical (CL), intermediate (INT), and nonclassical (NC), along with cell surface receptor expression and activation. Out of 80 enrolled patients, 26 (32.5%) developed CCI. Patients with CCI had more severe injuries (Injury Severity Score, 32.4 + 5.2 vs. 29.6 + 4.1, p = 0.01) and received a higher number of red blood cells (8.9 + 4.1 vs. 4.7 + 3.8 units, p < 0.01) compared with those without CCI. In patients with CCI, the NC monocytes were significantly reduced by over twofold early, and significantly increased later, compared with those without CCI. Moreover, significant changes in intracellular cytokine expression and cell receptors were observed within each monocyte subpopulation in patients with CCI, indicating an increased proinflammatory phenotype but decreased phagocytic capacity and antigen presentation. The development of CCI and the presence of this unique monocyte phenotype were associated with a significantly increased risk of infection, discharge to a long-term care facility, and 1-year mortality of 27%. Development of CCI following severe injury is associated with significant long-term morbidity and unacceptably high mortality. The altered NC phenotype with reduced phagocytic capacity and antigen presentation in patients developing CCI after severe injury is appears partially responsible. Early identification of this unique phenotype may help predict and treat patients at risk for CCI, leading to improved outcomes. Prognostic and Epidemiological; Level III.

OR18-01 Massively Parallel Functional Assay Of Extracellular Insulin Receptor Variants

Abstract Disclosure: V. Aslanzadeh: None. G. Brierley: None. G. Kudla: None. R.K. Semple: None. Loss-of-function mutations in the gene for the human insulin receptor, INSR, cause either autosomal dominant or autosomal recessive severe insulin resistance. Biallelic mutations produce extreme insulin resistance which is commonly fatal in infancy or childhood. A wide and growing number of mutations have been associated with disease, with few recurring mutations, and only a small subset have been studied functionally to date. Discriminating loss-of-function pathogenic alleles from insignificant variants is an important barrier to diagnosis and translational studies of novel candidate treatments. Such candidate therapies include a variety of antibody, peptide and small molecule ligands that activate the receptor in a manner distinct to insulin. These show potential to activate mutant receptors that are expressed but show impaired insulin binding or responsiveness. To address this barrier to translation we have now used massively multiplexed, Flow-Seq-based assays simultaneously to determine the effects of 14,000 human INSR extracellular domain missense variants. We assayed receptor cell surface expression, insulin binding and signal transduction using heterologous expression of mutants in mouse embryonic cells in which endogenous Insr and Igf1r genes had been knocked out or knocked down. Preliminary analysis reliably discriminates A. variants that reduce or abolish receptor cell surface expression when measured with two different monoclonal anti-receptor antibodies B. variants with preserved cell surface expression but selectively impaired binding of insulin and C. an overlapping group of variants with severely impaired signalling response to insulin but preserved response to antibody. Our assay confirmed previously studied attributes of a panel of disease-causing variants, and shows strong agreement with prior alanine scanning mutagenesis studies and structural predictions. We thus provide a rich sequence-function map for INSR variant interpretation. A prediction tool trained on known pathogenic INSR alleles is currently being developed for access by the community both to accelerate confident molecular diagnosis of newly identified rare INSR variants, and also to aid stratification of mutations according to potential for activation by non canonical INSR ligands. Presentation: Saturday, June 17, 2023

Radiosensitization of Glioblastoma Using Targeted Inhibition of N-Myristoylation

Treating Glioblastoma remains a major challenge. Radiotherapy has a long-standing role in extending survival, but almost all tumors are expected to recur and be fatal. Historic dose-escalation studies do not yield additional benefit beyond the current 60 Gy dose. Further therapeutic improvement can be gained with radiosensitizers. An undiscovered potential radiosensitization approach may exist in inhibiting the N-myristoylation pathways upregulated in malignant cells. Inhibiting this pathway has been shown to have pleotropic effects including decreasing PARP-1 activity and other cancer-driving pathways that may synergize with radiotherapy. This is a first report in using a targeted N-myristoyltransferase (NMT) inhibitor as a radiosensitizer in glioblastoma. Immortalized glioma cell lines (U87 and U251) and patient-derived de novo (ED501) and post-chemoradiation recurrent (ED512) cell lines were used to a NMT1/2 inhibitor with radiotherapy. Cell surface expression levels for NMT1 and NMT2 were established using immunofluorescence microscopy. In vitro cell viability studies via mitochondrial reduction of resazurin dye and clonogenic assays were done with single fraction 2 & 4 Gy irradiation with 5 days of drug exposure (5-150 nM 3 days prior to irradiation and 2 days post) to account for drug pharmacodynamics. PARP-1 expression by western blot was tested with exposure to drug and/or radiation. Whole exome sequencing and methylation profiling were done to find predictive markers of radiosensitization. Preliminary results show significant radiosensitization effect with a dose enhancement factor ranging from 1.33 to 2.71x higher than radiation alone. The amount of radiosensitization varied per cell line, with U251 and ED512 being more sensitive. The cell line sensitivity was not reliably predicted by the NMT cell surface receptor expression. PARP-1 activity increased with radiotherapy but was inhibited with drug exposure. Exome sequencing showed the radiosensitizing effect correlated with mutations in DNA damage repair and myristoylation pathways. N-myristoylation inhibition appears to be a novel method of radiosensitization for glioblastoma. N-myristoylation affects multiple oncogenic pathways including PARP-1 downregulation, which impedes DNA damage repair and may be what leads to radiosensitization. Future studies are aimed at further predictive markers and in vivo efficacy.