Red Blood Cell Protein Research Articles

Opportunistic infections changed before and after SARS-CoV-2 infection in inflammatory bowel disease patients: a retrospective single-center study in China.

SARS-CoV-2 transmission has become a serious worldwide public health concern. However, there is currently insufficient data to determine whether SARS-CoV-2 infection would affect opportunistic infections in inflammatory bowel disease (IBD) patients. A retrospective study included 451 IBD patients (294 UC and 157 CD). The IBD patients were divided into two groups: before SARS-CoV-2 infection and after SARS-CoV-2 infection, and outcomes were measured for these groups. The primary outcome was the presence and distribution of opportunistic infections. The secondary outcomes included factors associated with opportunistic infections, based on which a nomogram prediction model was developed and validated. After SARS-CoV-2 infection, the proportion of IBD patients with opportunistic infections by Clostridium difficile (21.31% vs. 14.01%, p = 0.044) and Epstein-Barr virus (13.93% vs. 4.35%, p = 0.001) was significantly higher compared to that before. Conversely, the proportion of patients with hepatitis B virus (3.69% vs. 10.14%, p = 0.006) and herpes simplex virus type I (1.23% vs. 4.35%, p = 0.04) infections was significantly lower after the infection. Additionally, pre-SARS-CoV-2 infection factors associated with opportunistic infections in IBD include duration of illness, red blood cell count, the presence of comorbid chronic illnesses, and alcohol consumption, while post-SARS-CoV-2 infection, the primary risk factors involve corticosteroid use, red blood cell count, protein level, and high-sensitivity C-reactive protein. After the SARS-CoV-2 infection, there has been a shift in the occurrence of opportunistic infections among IBD patients. It might be attributed to the use of corticosteroids and also the strengthening of containment measures, heightened public health awareness, and widespread vaccination.

Role of Quercetin Supplementation on Iron Parameters in Blood Transfusion-Dependent Thalassemia Patients

Background: Thalassemia is a group of inherited blood disorders that affect the production of hemoglobin, a protein in red blood cells that carries oxygen throughout the body. Iron overload is a condition in which the body absorbs and stores too much iron. In addition to repeated blood transfusions, increased gastrointestinal tract (GIT) iron absorption plays an important role in iron overload with thalassemia. Quercetin, a common flavonoid present in fruits and vegetables, exhibits diverse biological effects. Objective: To assess the effect of quercetin on iron overload parameters in blood transfusion-dependent thalassemia patients (TDT). Methods: A randomized, double-blind, placebo-placebo group-led study was conducted on 110 TDT patients, more than 12 years of age, who were supplemented with either quercetin or a placebo capsule daily (500 mg) for 3 months. A blood sample was obtained for laboratory parameters at baseline and at the end of 3 months. Results: At the baseline time of the study, the demographic features and iron overload parameters of patients and the placebo group were not statistically different, while after three months of supplementation, there was a significant decrease in levels of serum iron, UIBC, serum ferritin and ferritin saturation rate, and a significant increase in TIBC in the patients compared with the placebo group. Conclusions: The study shows the significant role of quercetin on iron overload parameters in blood transfusion-dependent thalassemia patients.

WITHDRAWN: Recent Advances in the Microbial Synthesis of Human Hemoglobin

Hemoglobin is a major binding protein in human red blood cells and plays an important role in the storage and transportation of oxygen. In recent years, the use of recombinant hemoglobin as a new type of oxygen carrier has attracted widespread attention. So far, the research on recombinant hemoglobin technology is in its early stages and there are still many problems, such as low yield and easy degradation. In this review, we summarize the molecular strategies for recombinant synthesis of human hemoglobin in microorganisms through metabolic engineering and synthetic biology techniques in recent years, and explore the possibility of preparing hemoglobin-based oxygen carriers based on fetal hemoglobin, in order to improve the yield of recombinant human hemoglobin and the sustained stability during protein production through protein engineering strategies, and to possibly reduce the toxic side effects of recombinant hemoglobin products.

Reconsidering red blood cells as the diagnostic potential for neurodegenerative disorders.

Red blood cells (RBCs) are usually considered simple cells and transporters of gases to tissues. However, recent research has suggested that RBCs may have diagnostic potential in major neurodegenerative disorders (NDDs). This review summarizes the current knowledge on changes in RBC in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and other NDDs. It discusses the deposition of neuronal proteins like amyloid-β, tau, and α-synuclein, polyamines, changes in the proteins of RBCs like band-3, membrane transporter proteins, heat shock proteins, oxidative stress biomarkers, and altered metabolic pathways in RBCs during neurodegeneration. It also highlights the comparison of RBC diagnostic markers to other in-market diagnoses and discusses the challenges in utilizing RBCs as diagnostic tools, such as the need for standardized protocols and further validation studies. The evidence suggests that RBCs have diagnostic potential in neurodegenerative disorders, and this study can pave the foundation for further research which may lead to the development of novel diagnostic approaches and treatments.

Mechanisms Underlying the Effects of Chloroquine on Red Blood Cells Metabolism.

Chloroquine (CQ) is a 4-aminoquinoline derivative largely employed in the management of malaria. CQ treatment exploits the drug's ability to cross the erythrocyte membrane, inhibiting heme polymerase in malarial trophozoites. Accumulation of CQ prevents the conversion of heme to hemozoin, causing its toxic buildup, thus blocking the survival of Plasmodium parasites. Recently, it has been reported that CQ is able to exert antiviral properties, mainly against HIV and SARS-CoV-2. This renewed interest in CQ treatment has led to the development of new studies which aim to explore its side effects and long-term outcome. Our study focuses on the effects of CQ in non-parasitized red blood cells (RBCs), investigating hemoglobin (Hb) functionality, the anion exchanger 1 (AE1) or band 3 protein, caspase 3 and protein tyrosine phosphatase 1B (PTP-1B) activity, intra and extracellular ATP levels, and the oxidative state of RBCs. Interestingly, CQ influences the functionality of both Hb and AE1, the main RBC proteins, affecting the properties of Hb oxygen affinity by shifting the conformational structure of the molecule towards the R state. The influence of CQ on AE1 flux leads to a rate variation of anion exchange, which begins at a concentration of 2.5 μM and reaches its maximum effect at 20 µM. Moreover, a significant decrease in intra and extracellular ATP levels was observed in RBCs pre-treated with 10 µM CQ vs. erythrocytes under normal conditions. This effect is related to the PTP-1B activity which is reduced in RBCs incubated with CQ. Despite these metabolic alterations to RBCs caused by exposure to CQ, no signs of variations in oxidative state or caspase 3 activation were recorded. Our results highlight the antithetical effects of CQ on the functionality and metabolism of RBCs, and encourage the development of new research to better understand the multiple potentiality of the drug.

Effect of Degree of Smoking Based on Brinkman Index on Hemoglobin Levels in Adults

Cigarette consumption is the main cause of death in the world because it affects various physiological conditions in the body. Various ingredients in cigarette smoke such as tar, nicotine, carbon monoxide, and others can cause health problems, especially in the O2 transportation system. Hemoglobin is a protein in red blood cells that carries oxygen from the lungs to all tissues. The carbon monoxide contained in cigarette smoke is competitive with O2 in binding to hemoglobin so that the oxygen distributed to the tissues is reduced. The body will compensate for peripheral hypoxia that occurs by increasing hemoglobin levels in the body so that oxygen transport to the tissues can be maintained. Research regarding the relationship between the degree of smoking and hemoglobin levels is still controversial. Analytical research with cross-sectional design. A total of 184 respondents were taken using purposive sampling and it was found that the majority (94%) were men who worked as security officers, cleaners, parking attendants, or technicians. Based on the Brinkman Index, 73.9% of respondents were classified as light smokers, only 1.6% were classified as heavy smokers and 50.5% of respondents had low hemoglobin levels. Analysis showed that the majority of respondents in the light smoker group had normal hemoglobin levels (58.1%), while moderate and heavy smokers had lower hemoglobin levels. In statistical analysis, a significant p-value (0.001) was found between the degree of smoking and hemoglobin levels.

Ginseng total saponin improves red blood cell oxidative stress injury by regulating tyrosine phosphorylation and glycolysis in red blood cells

BackgroundOxidative stress is the main cause of many diseases, but because of its complex pathogenic factors, there is no clear method for treating it. Ginseng total saponin (GTS) an important active ingredients in Panax ginseng C.A. Mey (PG) and has potential therapeutic ability for oxidative stress due to various causes. However, the molecular mechanism of GTS in the treating oxidative stress damage in red blood cells (RBCs) is still unclear. PurposeThis study aimed to examine the protective effect of GTS on RBCs under oxidative stress damage and to determine its potential mechanism. MethodsThe oxidative stress models of rat RBCs induced by hydrogen peroxide (H2O2) and exhaustive swimming in vivo and in vitro was used. We determined the cell morphology, oxygen carrying capacity, apoptosis, antioxidant capacity, and energy metabolism of RBCs. The effect of tyrosine phosphorylation (pTyr) of Band 3 protein on RBCs glycolysis was also examined. ResultsGTS reduced the hemolysis of RBCs induced by H2O2 at the lowest concentration. Moreover, GTS effectively improved the morphology, enhanced the oxygen carrying capacity, and increased antioxidant enzyme activity, adenosine triphosphate (ATP) levels, and adenosine triphosphatase (ATPase) activity in RBCs. GTS also promoted the expression of membrane proteins in RBCs, inhibited pTyr of Band 3 protein, and further improved glycolysis, restoring the morphological structure and physiological function of RBCs. ConclusionsThis study shows, that GTS can protect RBCs from oxidative stress damage by improving RBCs morphology and physiological function. Changes in pTyr expression and its related pTyr regulatory enzymes before and after GTS treatment suggest that Band 3 protein is the main target of GTS in the treating endogenous and exogenous oxidative stress. Moreover, GTS can enhance the glycolytic ability of RBCs by inhibiting pTyr of Band 3 protein, thereby restoring the function of RBCs.

Microstrip isoelectric focusing with deep learning for simultaneous screening of diabetes, anemia, and thalassemia

BackgroundHemoglobin (Hb) is an important protein in red blood cells and a crucial diagnostic indicator of diseases, e.g., diabetes, thalassemia, and anemia. However, there is a rare report on methods for the simultaneous screening of diabetes, anemia, and thalassemia. Isoelectric focusing (IEF) is a common separative tool for the separation and analysis of Hb. However, the current analysis of IEF images is time-consuming and cannot be used for simultaneous screening. Therefore, an artificial intelligence (AI) of IEF image recognition is desirable for accurate, sensitive, and low-cost screening. ResultsHerein, we proposed a novel comprehensive method based on microstrip isoelectric focusing (mIEF) for detecting the relative content of Hb species. There was a good coincidence between the quantitation of Hb via a conventional automated hematology analyzer and the one via mIEF with R2 = 0.9898. Nevertheless, our results showed that the accuracy of disease diagnosis based on the quantification of Hb species alone is as low as 69.33 %, especially for the simultaneous screening of multiple diseases of diabetes, anemia, alpha-thalassemia, and beta-thalassemia. Therefore, we introduced a ResNet1D-based diagnosis model for the improvement of screening accuracy of multiple diseases. The results showed that the proposed model could achieve a high accuracy of more than 90 % and a good sensitivity of more than 96 % for each disease, indicating the overwhelming advantage of the mIEF method combined with deep learning in contrast to the pure mIEF method. SignificanceOverall, the presented method of mIEF with deep learning enabled, for the first time, the absolute quantitative detection of Hb, relative quantitation of Hb species, and simultaneous screening of diabetes, anemia, alpha-thalassemia, and beta-thalassemia. The AI-based diagnosis assistant system combined with mIEF, we believe, will help doctors and specialists perform fast and precise disease screening in the future.

Protein fibril aggregation on red blood cells: a potential biomarker to distinguish neurodegenerative diseases from healthy aging.

Neurodegenerative diseases like Alzheimer's disease are characterized by the accumulation of misfolded proteins into fibrils in the brain. Atomic force microscopy is a nanoscale imaging technique that can be used to resolve and quantify protein aggregates from oligomers to fibrils. Recently, we characterized protein fibrillar aggregates adsorbed on the surface of red blood cells with atomic force microscopy from patients with neurocognitive disorders, suggesting a novel Alzheimer's disease biomarker. However, the age association of fibril deposits on red blood cells has not yet been studied in detail in healthy adults. Here, we used atomic force microscopy to visualize and quantify fibril coverage on red blood cells in 50 healthy adults and 37 memory clinic patients. Fibrillar protein deposits sporadically appeared in healthy individuals but were much more prevalent in patients with neurodegenerative disease, especially those with Alzheimer's disease as confirmed by positive CSF amyloid beta 1-42/1-40 ratios. The prevalence of fibrils on the red blood cell surface did not significantly correlate with age in either healthy individuals or Alzheimer's disease patients. The overlap in fibril prevalence on red blood cells between Alzheimer's disease and amyloid-negative patients suggests that fibril deposition on red blood cells could occur in various neurodegenerative diseases. Quantifying red blood cell protein fibril morphology and prevalence on red blood cells could serve as a sensitive biomarker for neurodegeneration, distinguishing between healthy individuals and those with neurodegenerative diseases. Future studies that combine atomic force microscopy with immunofluorescence techniques in larger-scale studies could further identify the chemical nature of these fibrils, paving the way for a comprehensive, non-invasive biomarker platform for neurodegenerative diseases.

Building Synthetic Biosensors Using Red Blood Cell Proteins.

As the use of engineered cell therapies expands from pioneering efforts in cancer immunotherapy to other applications, an attractive but less explored approach is the use of engineered red blood cells (RBCs). Compared to other cells, RBCs have a very long circulation time and reside in the blood compartment, so they could be ideally suited for applications as sentinel cells that enable in situ sensing and diagnostics. However, we largely lack tools for converting RBCs into biosensors. A unique challenge is that RBCs remodel their membranes during maturation, shedding many membrane components, suggesting that an RBC-specific approach may be needed. Toward addressing this need, here we develop a biosensing architecture built on RBC membrane proteins that are retained through erythropoiesis. This biosensor employs a mechanism in which extracellular ligand binding is transduced into intracellular reconstitution of a split output protein (including either a fluorophore or an enzyme). By comparatively evaluating a range of biosensor architectures, linker types, scaffold choices, and output signals, we identify biosensor designs and design features that confer substantial ligand-induced signal in vitro. Finally, we demonstrate that erythroid precursor cells engineered with our RBC-protein biosensors function in vivo. This study establishes a foundation for developing RBC-based biosensors that could ultimately address unmet needs including noninvasive monitoring of physiological signals for a range of diagnostic applications.

Pyruvate kinase deficiency and PKLR gene mutations: Insights from molecular dynamics simulation analysis

Pyruvate kinase deficiency is a rare hereditary erythrocyte enzyme disease caused by mutations in the pyruvate kinase liver and red blood cell gene. The clinical presentations of pyruvate kinase deficiency are significantly heterogeneous, ranging from just mild anemia to hemolytic crisis or even death. The proband in our study was a 2-year-old girl for severe skin and scleral icterus with progressive aggravation. We collected the family's data for further analysis. Whole exome genome sequencing of the pedigree revealed a novel compound heterozygous mutation, c.1097del (p.P366Lfs*12) and c.1493G > A (p.R498H), in the pyruvate kinase liver and red blood cell gene. Furthermore, molecular dynamics simulations were employed to uncover differences between the wild type and mutant pyruvate kinase liver and red blood cell proteins, focusing on structural stability, protein flexibility, secondary structure, and overall conformation. The combined bioinformatic tools were also utilised to assess the effects of the missense mutation on protein function. Thereafter, wild type and mutant plasmids were constructed and transfected into 293T cells, and Western blot assay was conducted to validate the impact of the mutations on the expression of pyruvate kinase liver and red blood cell protein. The data presented in our study enriches the genotype database and provides evidence for genetic counseling and molecular diagnosis of pyruvate kinase deficiency.

Pharmacologic Therapies in Beta Hemoglobinopathies: Fetal Globin Gene Induction in the First Molecular Diseases

Beta hemoglobinopathies and thalassemias are caused by diverse molecular mutations of the βA globin chains and modulated by polymorphisms. These are important disorders in medical history, as they became prevalent globally in regions where P. falciparum malaria was endemic. Heterozygous or carrier states conferred a survival advantage; however, doubly heterozygous or homozygous states cause severe hemolytic anemia and multi-organ complications. These disorders are somewhat unique in that all humans have alternate genes for fetal globin chains, which are expressed in fetal life but are silenced on a developmental clock in infancy. An established approach to ameliorating conditions of abnormal adult globin genes is to reactivate, or increase expression, of the endogenous fetal globin genes to replace the missing protein chains in beta thalassemias or inhibit polymerization of hemoglobin S and reduce the red cell abnormalities. This review provides a high-level overview of cell and molecular mechanisms that mediate fetal to adult globin gene switching and pharmacologic therapies that can reactivate fetal globin through different actions. Intermittent or metronomic dosing regimens have overcome challenges of undesirable off-target effects by agents that cause erythroid cell growth arrest. Multiple pharmacologic candidates reactivate or increase the expression of fetal globin protein and proportions of red blood cells containing HbF (F-cells). Hydroxyurea maintains high levels of HbF if begun in infancy, with some decline in mid-childhood. It elicits lower responses in HbF in adult patients, but still has broad clinical benefit in reducing many complications. However, many adult patients do not tolerate optimal hydroxyurea dosing due to cytopenias. Parenterally administered therapies with differing molecular actions, such as demethylating agents and histone deacetylase inhibitors, have shown proof-of-principle in reactivating HbF. Orally bioavailable candidates with complementary molecular mechanisms are in trials. Combining fetal globin-inducing agents with other therapies with complementary mechanisms, such as recombinant erythropoietin that promotes the survival of red blood cells and therapeutics that promote erythroid cell metabolism, should have additive effects. These pharmaceutical candidates offer great clinical potential and global feasibility for ameliorating these serious diseases.

Peran Tenaga Kesehatan Dalam Menurunkan Prevalensi Anemia Pada Remaja, dan Faktor Yang Mempengaruhi Terjadinya Anemia

Anemia is a disease characterized by lower-than-normal hemoglobin (Hb) levels in the blood. Hemoglobin is a protein in red blood cells that functions to transport oxygen from the lungs to the rest of the body. Based on the research findings, it is known that the role of Posyandu adolescents is to provide health services by health workers. The services provided are in the form of facilitators who will conduct health checks and refer adolescent girls diagnosed with anemia to the Puskesmas for hemoglobin testing. Since adolescent girls are at risk of anemia during menstruation, Posyandu Remaja needs to motivate them to take blood product tablets and undergo regular health checks every month. This study uses a literature review methodology that focuses on themes or variables obtained from previous research, namely written research (Wahyudi, 2022). Data regarding the role of health workers in reducing the prevalence of anemia in adolescents and factors influencing the occurrence of anemia were identified from research articles and literature reviews. Similar to Bangladesh and India, the prevalence of anemia in India is very high at 45.9%. One of the main factors causing anemia in adolescent girls is improper nutritional habits.

Functional and Multi-Omics Signatures of Mitapivat Efficacy upon Activation of Pyruvate Kinase in Red Blood Cells from Patients with Sickle Cell Disease

2,3-diphosphoglycerate (DPG) in red blood cells (RBCs) stabilizes deoxyhemoglobin to promote hemoglobin (Hb) oxygen off-loading and counteract hypoxia. In sickle cell disease (SCD), mutation of glutamate 6 to valine in the beta chain of Hb results in HbS that polymerizes, causing RBCs to sickle upon deoxygenation in the tissues. Elevated DPG promotes sickling by stabilizing HbS fibers. DPG is an intermediate substrate in the glycolytic pathway in which pyruvate kinase (PK) is a rate-limiting enzyme. In a previous Phase 1 study (NCT04000165, Xu et al, 2022), we established proof-of-concept for activating PK as a viable anti-sickling therapeutic approach; mitapivat, an investigational oral allosteric activator of PK, decreased DPG and increased adenosine triphosphate (ATP) levels, improved hematologic and sickling parameters in patients (pts) with SCD (HbSS). Here, we investigated the changes in the metabolome, lipidome and proteome of RBCs from patients with SCD currently enrolled in an open label, Phase 1/2 study (NCT04610866) that evaluates long-term safety and tolerability of mitapivat in pts with SCD. Fifteen pts with HbSS (aged 25 - 57 years, 10 males) were evaluated. All pts started mitapivat at 50 mg twice daily (BID), escalating after 4 wks to 100 mg BID; dose adjustments were performed for safety and tolerability, per PI discretion. At the time of data cutoff (March 23, 2023), all 15 pts completed the core period of 24 wks, 14 pts completed 48 wks ,10 pts completed 72 wks and 6 pts completed 92 wks. Leuko-depleted RBCs (LDRBCs) obtained from fresh whole blood in EDTA at baseline (V1, prior to drug initiation) and various longitudinal time points over the course of the study were flash-frozen in liquid nitrogen and kept frozen at -80°C until analysis. Clinical measurements of DPG, ATP, red cell PK (PKR) protein and activity levels, oxygen affinity (p50) and sickling kinetics (t50) were accompanied by multi-omics (metabolomics, lipidomics, proteomics) characterization of the LDRBCs. In total, 150 (6x12, 4x10, 4x8 and 1x6) timepoint samples were analyzed (Fig 1A). Multi-omics analyses were performed through a stepwise extraction of metabolites, lipids and proteins on 50 µl of packed LDRBC pellets. Extracts were separated via ultra-high-pressure liquid chromatography coupled to mass spectrometry, prior to peak picking and identification of ddMS2 data as previously described (Thomas et al 2020). Statistical analyses were conducted using MetaboAnalyst v 5.0 and Rstudio upon normalization of relative quantitative data to visit 0 levels for each variable. Network analysis and pathway analysis were performed in OmicsNet v 2.0. Mitapivat therapy had significant effects on the metabolome, lipidome and proteome of SCD RBCs. Overall, the temporal trends of omics responses to mitapivat treatment across visits was evident, especially when focusing on the top 50 metabolites/lipids or proteins by time series ANOVA. Specifically, results suggested a positive correlation between mass spectrometry-based quantitation of RBC mitapivat levels and DPG consumption, ATP accumulation, PKR activity (measured via enzymatic assays), and PKR protein levels, with internal consistency between omics data and antibody-based or enzymatic assays (Fig. 1A). The treatment also promoted activation of the Lands cycle, transient elevation of lysophosphatidylcholines and oxylipins, and depletion in free fatty acids within the first 6 months, suggestive of an effect on membrane lipid remodeling. SCD RBCs abnormally retain mitochondria; here, we showed a consistent decrease in the levels of residual mitochondrial proteins in RBCs within 4 wks of mitapivat treatment (Fig. 1B). In keeping with the predicted activation of PKR upon mitapivat treatment, we observed decreases in DPG and increases in ATP, with elevation in glycolytic fluxes, as inferred from longitudinal changes in glycolytic intermediates at the hexose and triose phosphate steps, as well as lactate. Unsupervised analyses of omics data confirmed the specificity of mitapivat on targeting late glycolysis, with glycolytic metabolites ranking as the top correlates to parameters of oxygen affinity (p50) and sickling kinetics (t50) during mitapivat treatment. Multi-omics analysis of RBCs from HbSS patients treated with mitapivat identified benefits for glycolysis, DPG consumption and ATP generation, as well as activation of the Lands cycle.

Urea Transporter B Is Produced in the Jk Null Blood Group Yet Fails to Integrate into the Red Cell Membrane Impacting Erythropoiesis and Erythrocytes

The Kidd (Jk) blood group is carried by an integral membrane glycoprotein, urea transporter B (UT-B), which transports urea through the red blood cell (RBC) membrane. The absence of both Jk a and Jk b antigens, designated phenotypically as Jk(a-b-) (Jk null), is very rare with a significantly increased prevalence in certain ethnicities, most abundantly within the Polynesian population where it is found at 0.9% prevalence. Provision of blood for patients requiring this phenotype is challenging. In Australia, there are only 15 active Jk null blood donors. Individuals of the Jk null phenotype have been shown to have suboptimal urine concentrating ability but erythrocytes appear phenotypically normal with shape, size and lifespan within normal reference indices (Lawicki et al., Transfus Med Rev, 2017). Where UT-B integrates in the RBC membrane is unknown although protein 4.1R deficiency is reported to lead to the absence of UT-B (Azouzi et al., Br J Haematol, 2015). Our aim was to identify and characterise the molecular basis for the Jk null phenotype in Australian blood donors and decipher the biological impact of the Jk null phenotype using our ex vivo model of erythropoiesis to help inform clinical transfusion practice. Massively parallel sequencing showed that all blood donors (n=9) were homozygous for JK c.342-1G>A (splice site variant) and c.838G>A polymorphisms resulting in the JK*02N.01/*02N.01 genotype. This genotype predicts a Jk null phenotype, and a truncated UT-B protein caused by the formation of a premature stop codon. The assumption from the genomics data is that the putative truncated UT-B protein would not be translated. To test this hypothesis we examined the RBCs of Jk null individuals and confirmed the lack of UT-B expression on the RBC surface by live flow cytometry and confocal imaging. In control RBCs UT-B is seen in discrete microdomains on the RBC surface by live confocal microscopy. To establish the expression of UT-B during erythropoiesis we cultured CD34+ cells from control and Jk null buffy coats after whole blood donation. Flow cytometry and confocal microscopy of control cells identified that UT-B is expressed intracellularly and at the cell surface in the developing erythroid cells. Notably we identified that the UT-B protein can also be found intracellularly in developing Jk null erythroid cells but is not detectable in the plasma membrane. In Jk null reticulocytes, UT-B colocalises with markers of protein degradation and destruction implying that the truncated UT-B protein is quickly removed by controlled protein degradation pathways. Quantitative proteomics was used to assess the global effect of the Jk null phenotype on the mature RBC membrane proteome. These data confirmed the absence of UT-B but also uncovered that in mature Jk null RBCs, RBC proteins involved in solute transport (aquaporin-1, stomatin) and membrane-cytoskeleton stabilisation (alpha and beta adducins, and dematin) are significantly downregulated. In contrast, actin binding proteins including tropomyosin and myosin IIA were upregulated in Jk null RBCs. The proteomics data also revealed that numerous major plasma proteins including alpha-2-macroglobulin, hemopexin and immunoglobulins are associated exclusively with Jk null RBCs. These findings imply that the lack of functional, membrane embedded UT-B induces various compensatory mechanisms in the Jk null RBCs membrane. In conclusion, we show that a truncated UT-B protein is produced in Jk null erythroid cells but fails to mature into a RBC membrane integrated, functional glycoprotein. Our data also suggest that the absence of a functional UT-B glycoprotein on the RBC surface affects the RBC membrane and cytoskeletal proteome and its interaction with major plasma glycoproteins.

Abstract 12733: The Effect of Mavacamten Treatment on Hemolysis Biomarkers in Patients With Obstructive Hypertrophic Cardiomyopathy in the EXPLORER-HCM Study

Introduction: In patients with obstructive hypertrophic cardiomyopathy (HCM), blood flow changes from left ventricular outflow tract (LVOT) obstruction can lead to hemolysis and release of red blood cell proteins into circulation. Increased cell-free plasma hemoglobin (Hb) and reduced haptoglobin (Hp) are biomarkers of intravascular hemolysis. Mavacamten, a cardiac myosin inhibitor, reduced LVOT obstruction in the phase 3 EXPLORER-HCM study; however, its effect on hemolysis biomarkers is unknown. Aim: To assess the effect of 30 weeks of mavacamten treatment versus placebo on levels of intravascular hemolysis biomarkers in patients with obstructive HCM. Methods: Hemolysis biomarkers were measured as part of exploratory proteomic analyses from randomized EXPLORER-HCM (NCT03470545) patients at baseline and Week 30 (mavacamten, n = 115; placebo, n = 120) using a proteomic platform (SomaScan v4.1). Results: At Week 30, mavacamten treatment showed decreases in cell-free plasma Hb (Log 2 fold change = -1.57, FDR = 1.7х10 -4 ) and increases in cell-free plasma Hp (Log 2 fold change = 1.83, FDR = 1.2х10 -4 ) vs placebo (Figure). Hb and Hp levels were negatively correlated at baseline and at Week 30. In general, patients can be grouped into high- or low- hemolysis biomarker profile (high Hb with low Hp or low Hb with high Hp, respectively) at baseline and Week 30. Patients who received mavacamten and changed from high- to low hemolysis biomarker profile at Week 30 trended towards greater LVOT reductions under resting and Valsalva conditions. No changes were detected for either group in whole blood Hb or hematocrit. Conclusions: Reduced cell-free plasma Hb and increased cell-free plasma Hp levels, suggest a reduction in intravascular hemolysis by mavacamten in obstructive HCM. These results are consistent with improved hemodynamic effects (less outflow obstruction) and indicate that mavacamten may reduce shear forces on red blood cells in the heart.

The dual action of human antibodies specific to Plasmodium falciparum PfRH5 and PfCyRPA: Blocking invasion and inactivating extracellular merozoites.

The Plasmodium falciparum reticulocyte-binding protein homolog 5 (PfRH5) is the current leading blood-stage malaria vaccine candidate. PfRH5 functions as part of the pentameric PCRCR complex containing PTRAMP, CSS, PfCyRPA and PfRIPR, all of which are essential for infection of human red blood cells (RBCs). To trigger RBC invasion, PfRH5 engages with RBC protein basigin in a step termed the RH5-basigin binding stage. Although we know increasingly more about how antibodies specific for PfRH5 can block invasion, much less is known about how antibodies recognizing other members of the PCRCR complex can inhibit invasion. To address this, we performed live cell imaging using monoclonal antibodies (mAbs) which bind PfRH5 and PfCyRPA. We measured the degree and timing of the invasion inhibition, the stage at which it occurred, as well as subsequent events. We show that parasite invasion is blocked by individual mAbs, and the degree of inhibition is enhanced when combining a mAb specific for PfRH5 with one binding PfCyRPA. In addition to directly establishing the invasion-blocking capacity of the mAbs, we identified a secondary action of certain mAbs on extracellular parasites that had not yet invaded where the mAbs appeared to inactivate the parasites by triggering a developmental pathway normally only seen after successful invasion. These findings suggest that epitopes within the PfCyRPA-PfRH5 sub-complex that elicit these dual responses may be more effective immunogens than neighboring epitopes by both blocking parasites from invading and rapidly inactivating extracellular parasites. These two protective mechanisms, prevention of invasion and inactivation of uninvaded parasites, resulting from antibody to a single epitope indicate a possible route to the development of more effective vaccines.

Changes in Hemoglobin Properties in Complex with Glutathione and after Glutathionylation.

Hemoglobin is the main protein of red blood cells that provides oxygen transport to all cells of the human body. The ability of hemoglobin to bind the main low-molecular-weight thiol of the cell glutathione, both covalently and noncovalently, is not only an important part of the antioxidant protection of red blood cells, but also affects its affinity for oxygen in both cases. In this study, the properties of oxyhemoglobin in complex with reduced glutathione (GSH) and properties of glutathionylated hemoglobin bound to glutathione via an SS bond were characterized. For this purpose, the methods of circular dichroism, Raman spectroscopy, infrared spectroscopy, tryptophan fluorescence, differential scanning fluorimetry, and molecular modeling were used. It was found that the glutathionylation of oxyhemoglobin caused changes in the secondary structure of the protein, reducing the alpha helicity, but did not affect the heme environment, tryptophan fluorescence, and the thermostability of the protein. In the noncovalent complex of oxyhemoglobin with reduced glutathione, the secondary structure of hemoglobin remained almost unchanged; however, changes in the heme environment and the microenvironment of tryptophans, as well as a decrease in the protein's thermal stability, were observed. Thus, the formation of a noncovalent complex of hemoglobin with glutathione makes a more significant effect on the tertiary and quaternary structure of hemoglobin than glutathionylation, which mainly affects the secondary structure of the protein. The obtained data are important for understanding the functioning of glutathionylated hemoglobin, which is a marker of oxidative stress, and hemoglobin in complex with GSH, which appears to deposit GSH and release it during deoxygenation to increase the antioxidant protection of cells.

A Pyridyl-Furan Series Developed from the Open Global Health Library Block Red Blood Cell Invasion and Protein Trafficking in Plasmodium falciparum through Potential Inhibition of the Parasite's PI4KIIIB Enzyme.

With the resistance increasing to current antimalarial medicines, there is an urgent need to discover new drug targets and to develop new medicines against these targets. We therefore screened the Open Global Health Library of Merck KGaA, Darmstadt, Germany, of 250 compounds against the asexual blood stage of the deadliest malarial parasite Plasmodium falciparum, from which eight inhibitors with low micromolar potency were found. Due to its combined potencies against parasite growth and inhibition of red blood cell invasion, the pyridyl-furan compound OGHL250 was prioritized for further optimization. The potency of the series lead compound (WEHI-518) was improved 250-fold to low nanomolar levels against parasite blood-stage growth. Parasites selected for resistance to a related compound, MMV396797, were also resistant to WEHI-518 as well as KDU731, an inhibitor of the phosphatidylinositol kinase PfPI4KIIIB, suggesting that this kinase is the target of the pyridyl-furan series. Inhibition of PfPI4KIIIB blocks multiple stages of the parasite's life cycle and other potent inhibitors are currently under preclinical development. MMV396797-resistant parasites possess an E1316D mutation in PfPKI4IIIB that clusters with known resistance mutations of other inhibitors of the kinase. Building upon earlier studies that showed that PfPI4KIIIB inhibitors block the development of the invasive merozoite parasite stage, we show that members of the pyridyl-furan series also block invasion and/or the conversion of merozoites into ring-stage intracellular parasites through inhibition of protein secretion and export into red blood cells.

Physicochemical evaluation of interaction behavior of a series of biocompatible gemini surfactants with hemoglobin: Insights from spectroscopic and computational studies

In this study, we investigated the interaction behavior of biodegradable, cationic, oxy-diester functionalized gemini surfactants N1,N1,N14,N14-tetramethyl-2,13-dioxo-N1,N14-dialkyl-3,6,12-tetraoxateradecane-1,14-diaminium dichloride (in short Cm-E2O2-Cm, m = 12, 14 or 16 is the number of carbon atoms in the alkyl chain) with one of the most important proteins in red blood cells viz. hemoglobin. We employed a variety of in-vitro and in-silico methodologies, such as fluorescence, UV–vis, FT-IR and circular dichroism spectroscopies, DFT, molecular docking, and molecular dynamics simulations, to study these interactions. Our results show that the chain length of the surfactants have distinct implications for the interaction behavior, as evidenced by the estimated physical parameters, such as Kb and ∆G. The order of Kb values (0.24 × 103 < 3.11 ×103 < 5.85 × 103 M-1) is in accordance with the increasing alkyl chain length of the surfactants. The negative Gibbs free energy change values and their order, − 13.58 < −19.93 < −21.49, further support the spontaneity of interactions and the effect of alkyl chain length. Theoretical insight into the environment at the quantum mechanical level, binding site, and energy stability of the protein-surfactant interactions were produced by computational methods. This research contributes significantly to the field of knowledge concerning surfactants' effects on protein structure and behavior.