The Hsp70 chaperone system: distinct roles in erythrocyte formation and maintenance

Physiological analysis and transcriptome sequencing revealed that HSPA1 was involved in response to heat stress in thick-shell mussels, Mytilus coruscus

Mytilus coruscus, being sensitive to temperature variations, has developed a protective mechanism against heat stress through the upregulation of genes encoding heat shock proteins. Past research indicates that exposure to heat stress can activate HSPA1 expression for protection, yet the underlying regulatory mechanisms governing this response are not fully clear. Therefore, the emphasis of this study lies on regulating the expression of HSPA1 in mussels under high temperature stress. This study showed that high temperature could cause tissue damage and induce apoptosis in M. coruscus. Overexpression of HSPA1 at high temperature can mitigate damage. Enzyme activity assays also found that after the overexpression of HSPA1 at high temperature, the enzyme activity of SOD, CAT and GSH-PX increased to cope with the stimulation brought by high temperature, which suggests that the HSPA1 gene plays a critical role in the antioxidant response. Transcriptome analysis showed that under high-temperature stress, key genes including HSPA1S, HSP90, HSPA5, DnaJA1, and JUN showed increased expression in HSPA1-knockdown treatments, with differential gene expression enriched in pathways associated with MAPK signaling, endoplasmic reticulum protein processing, TNF signaling, apoptosis, and cell apoptosis pathways. Based on this, we suggested that M. coruscus may counteract damage induced by high-temperature stress via the above key genes and biology processes, highlighting the crucial role of HSPA1 in mitigating cell damage and apoptosis due to high temperature. Overall, our results revealed HSPA1 regulatory relationship in M. coruscus treated with high temperature, and provided new insights for the conservation and environmental adaptive evolution of bivalve species.

De novo Transcriptomic analysis to unveil the deltamethrin induced resistance mechanisms in Callosobruchus chinensis (L.)

The use of synthetic insecticides has been crucial in the management of insect pests however the extensive use of insecticides can result in the development of resistance. Callosobruchus chinensis is a highly destructive pest of stored grains, it's a major feeder and infests a range of stored grains that are vital to both global food security and human nutrition. We extensively investigated gene expression changes of adults in response to deltamethrin to decipher the mechanism behind the insecticide resistance. The analysis of gene expression revealed 25,343 unigenes with a mean length of 1,435 bp. All the expressed genes were identified, and analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. Exposure to deltamethrin (4.6 ppm) causes 320 differentially expressed genes (DEGs), of which 280 down-regulated and 50 up-regulated. The transcriptome analysis revealed that DEGs were found to be enriched in pathways related to xenobiotics metabolism, signal transduction, cellular processes, organismal systems and information processing. The quantitative real-time PCR was used to validate the DEGs encoding metabolic detoxification. To the best of our knowledge, these results offer the first toxicity mechanisms enabling a more comprehensive comprehension of the action and detoxification of deltamethrin in C. chinensis.

Salivary heat shock protein 70 as a potential non-invasive biomarker of environmental thermal stress in dairy cattle

The present study aims to explore the potential biomarker application of salivary heat shock 70 kDa protein in detecting thermal stress in dairy animals noninvasively. The study spans for 45 days during the mid-summer season (April-May), involving twelve multiparous non-pregnant adult Jersey crossbred cows by randomly allocating them into groups (six animals in each group). The control animals were maintained in the shed, whereas the thermal stress group animals were exposed to environment heat between 10:00 h to 16.00 h and they were feed and watered ad libitum. During the experimental period, the hematobiochemical, physiological, behavioural, nutritional and production responses were recorded and the whole blood and saliva were collected fortnightly. Results revealed significant increase in WBC, AST, ALP, blood urea nitrogen, triglycerides, cholesterol, HDL, blood and salivary cortisol, respiratory rate, rectal temperature, skin temperature of neck, lumbar and forelimb regions, standing time, salivary and blood HSP70 mRNA expression and their protein concentrations in heat stressed animals. In addition, RBC, haemoglobin, MCV, PCV, platelet, platelet-large cell ratio (PLCR), lying time, feed intake, milk yield and rumination time were significantly decreased in thermally stress animals. Furthermore, ROC curve analysis revealed the biomarker potential of these significantly altered parameters with 100% sensitivity and specificity for predicting environmental heat stress in dairy cows with AUC and Youden's - index of 1.00 except platelet. Moreover, salivary HSP70 demonstrated significant correlation with these biomarkers. Noteworthily, salivary HSP70 also exhibited strong association with blood HSP70 and salivary cortisol. Furthermore, salivary HSP70 revealed 100% sensitivity and specificity in discriminating the dairy cattle succumbed to heat stress from healthy. In conclusion, the present study provides a newer insight into the multifaceted roles of HSP70 and identified salivary heat shock 70 kDa protein as a potential, reliable and more sensitive non-invasive biomarker for identifying environmental heat stress in dairy cattle.

Erythronecroptosis: an overview of necroptosis or programmed necrosis in red blood cells

Necroptosis is considered a programmed necrosis that requires receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and pore-forming mixed lineage kinase domain-like protein (MLKL) to trigger a regulated cell membrane lysis. Membrane rupture in necroptosis has been shown to fuel innate immune response due to release of damage-associated molecular patterns (DAMPs). Recently published studies indicate that mature erythrocytes can undergo necroptosis as well. In this review, we provide an outline of multiple cell death modes occurring in erythrocytes, discuss possible immunological aspects of diverse erythrocyte cell deaths, summarize available evidence related to the ability of erythrocytes to undergo necroptosis, outline key involved molecular mechanisms, and discuss the potential implication of erythrocyte necroptosis in the physiology and pathophysiology. Furthermore, we aim to highlight the interplay between necroptosis and eryptosis signaling in erythrocytes, emphasizing specific characteristics of these pathways distinct from their counterparts in nucleated cells. Thus, our review provides a comprehensive summary of the current knowledge of necroptosis in erythrocytes. To reflect critical differences between necroptosis of nucleated cells and necroptosis of erythrocytes, we suggest a term erythronecroptosis for necroptosis of enucleated cells.

Targeting erythroid progenitor cells for cancer immunotherapy

Immunotherapy, especially immune checkpoint blockade therapy, represents a major milestone in the history of cancer therapy. However, the current response rate to immunotherapy among cancer patients must be improved; thus, new strategies for sensitizing patients to immunotherapy are urgently needed. Erythroid progenitor cells (EPCs), a population of immature erythroid cells, exert potent immunosuppressive functions. As a newly recognized immunosuppressive population, EPCs have not yet been effectively targeted. In this review, we summarize the immunoregulatory mechanisms of EPCs, especially for CD45+ EPCs. Moreover, in view of the regulatory effects of EPCs on the tumor microenvironment, we propose the concept of EPC-immunity, present existing strategies for targeting EPCs, and discuss the challenges encountered in both basic research and clinical applications. In particular, the impact of existing cancer treatments on EPCs is discussed, laying the foundation for combination therapies. The aim of this review is to provide new avenues for improving the efficacy of cancer immunotherapy by targeting EPCs.

Erythropoiesis and Gene Expression Analysis in Erythroid Progenitor Cells Derived from Patients with Hemoglobin H/Constant Spring Disease

Hemoglobin H/Constant Spring (Hb H/CS) disease represents a form of non-deletional Hb H disease characterized by chronic hemolytic anemia that ranges from moderate to severe and may lead to transfusion-dependent thalassemia. To study the underlying mechanisms of this disease, we conducted an analysis of erythropoiesis and gene expression in erythroid progenitor cells derived from CD34+ hematopoietic stem/progenitor cells from patients with Hb H/CS disease and normal controls. Twelve patients with Hb H/CS disease and five normal controls were enrolled. Peripheral blood samples were collected to isolate CD34+ hematopoietic stem/progenitor cells for the analysis of cell proliferation and differentiation. Six samples from patients with Hb H/CS disease and three controls were subsequently studied for gene expression by next generation sequencing analysis. Erythroid progenitor cells derived from patients with Hb H/CS disease exhibited a trend towards increased rates of erythroid proliferation and decreased cell viability compared to those from controls. Moreover, erythroid progenitor cells derived from patients with Hb H/CS disease demonstrated delayed terminal differentiation. Gene expression profiling revealed elevated levels of genes encoding molecular chaperones, including the heat shock protein genes (HSPs) and the chaperonin containing TCP-1 subunit genes (CCTs) in the Hb H/CS disease group. In summary, erythroid progenitor cells derived from patients with Hb H/CS disease exhibit a trend towards heightened erythroid proliferation, diminished cell viability, and delayed terminal differentiation. Additionally, the increased expression of genes encoding molecular chaperones was observed, providing information on potential underlying pathophysiological mechanisms.

Pseudophosphorylation of single residues of the J-domain of DNAJA2 regulates the holding/folding balance of the Hsc70 system

The Hsp70 system is essential for maintaining protein homeostasis and comprises a central Hsp70 and two accessory proteins that belong to the J-domain protein (JDP) and nucleotide exchange factor families. Posttranslational modifications offer a means to tune the activity of the system. We explore how phosphorylation of specific residues of the J-domain of DNAJA2, a class A JDP, regulates Hsc70 activity using biochemical and structural approaches. Among these residues, we find that pseudophosphorylation of Y10 and S51 enhances the holding/folding balance of the Hsp70 system, reducing cochaperone collaboration with Hsc70 while maintaining the holding capacity. Truly phosphorylated J domains corroborate phosphomimetic variant effects. Notably, distinct mechanisms underlie functional impacts of these DNAJA2 variants. Pseudophosphorylation of Y10 induces partial disordering of the J domain, whereas the S51E substitution weakens essential DNAJA2-Hsc70 interactions without a large structural reorganization of the protein. S51 phosphorylation might be class-specific, as all cytosolic class A human JDPs harbor a phosphorylatable residue at this position.

Entire expressed peripheral blood transcriptome in pediatric severe malarial anemia

This study on severe malarial anemia (SMA: Hb < 6.0 g/dL), a leading global cause of childhood morbidity and mortality, compares the entire expressed whole blood host transcriptome between Kenyan children (3-48 mos.) with non-SMA (Hb ≥ 6.0 g/dL, n = 39) and SMA (n = 18). Differential expression analyses reveal 1403 up-regulated and 279 down-regulated transcripts in SMA, signifying impairments in host inflammasome activation, cell death, and innate immune and cellular stress responses. Immune cell profiling shows decreased memory responses, antigen presentation, and immediate pathogen clearance, suggesting an immature/improperly regulated immune response in SMA. Module repertoire analysis of blood-specific gene signatures identifies up-regulation of erythroid genes, enhanced neutrophil activation, and impaired inflammatory responses in SMA. Enrichment analyses converge on disruptions in cellular homeostasis and regulatory pathways for the ubiquitin-proteasome system, autophagy, and heme metabolism. Pathway analyses highlight activation in response to hypoxic conditions [Hypoxia Inducible Factor (HIF)-1 target and Reactive Oxygen Species (ROS) signaling] as a central theme in SMA. These signaling pathways are also top-ranking in protein abundance measures and a Ugandan SMA cohort with available transcriptomic data. Targeted RNA-Seq validation shows strong concordance with our entire expressed transcriptome data. These findings identify key molecular themes in SMA pathogenesis, offering potential targets for new malaria therapies.

Interplay between α-thalassemia and β-hemoglobinopathies: Translating genotype-phenotype relationships into therapies

α-Thalassemia represents one of the most important genetic modulators of β-hemoglobinopathies. During this last decade, the ongoing interest in characterizing genotype-phenotype relationships has yielded incredible insights into α-globin gene regulation and its impact on β-hemoglobinopathies. In this review, we provide a holistic update on α-globin gene expression stemming from DNA to RNA to protein, as well as epigenetic mechanisms that can impact gene expression and potentially influence phenotypic outcomes. Here, we highlight defined α-globin targeted strategies and rationalize the use of distinct molecular targets based on the restoration of balanced α/β-like globin chain synthesis. Considering the therapies that either increase β-globin synthesis or reactivate γ-globin gene expression, the modulation of α-globin chains as a disease modifier for β-hemoglobinopathies still remains largely uncharted in clinical studies.

Pseudouridine synthase 1 regulates erythropoiesis via transfer RNAs pseudouridylation and cytoplasmic translation

Pseudouridylation plays a regulatory role in various physiological and pathological processes. A prime example is the mitochondrial myopathy, lactic acidosis, and sideroblastic anemia syndrome (MLASA), characterized by defective pseudouridylation resulting from genetic mutations in pseudouridine synthase 1 (PUS1). However, the roles and mechanisms of pseudouridylation in normal erythropoiesis and MLASA-related anemia remain elusive. We established a mouse model carrying a point mutation (R110W) in the enzymatic domain of PUS1, mimicking the common mutation in human MLASA. Pus1-mutant mice exhibited anemia at 4 weeks old. Impaired mitochondrial oxidative phosphorylation was also observed in mutant erythroblasts. Mechanistically, mutant erythroblasts showed defective pseudouridylation of targeted tRNAs, altered tRNA profiles, decreased translation efficiency of ribosomal protein genes, and reduced globin synthesis, culminating in ineffective erythropoiesis. Our study thus provided direct evidence that pseudouridylation participates in erythropoiesis in vivo. We demonstrated the critical role of pseudouridylation in regulating tRNA homeostasis, cytoplasmic translation, and erythropoiesis.

Linking Gene Fusions to Bone Marrow Failure and Malignant Transformation in Dyskeratosis Congenita

Dyskeratosis Congenita (DC) is a multisystem disorder intrinsically associated with telomere dysfunction, leading to bone marrow failure (BMF). Although the pathology of DC is largely driven by mutations in telomere-associated genes, the implications of gene fusions, which emerge due to telomere-induced genomic instability, remain unexplored. We meticulously analyzed gene fusions in RNA-Seq data from DC patients to provide deeper insights into DC's progression. The most significant DC-specific gene fusions were subsequently put through in silico assessments to ascertain biophysical and structural attributes, including charge patterning, inherent disorder, and propensity for self-association. Selected candidates were then analyzed using deep learning-powered structural predictions and molecular dynamics simulations to gauge their potential for forming higher-order oligomers. Our exploration revealed that genes participating in fusion events play crucial roles in upholding genomic stability, facilitating hematopoiesis, and suppressing tumors. Notably, our analysis spotlighted a particularly disordered polyampholyte fusion protein that exhibits robust higher-order oligomerization dynamics. To conclude, this research underscores the potential significance of several high-confidence gene fusions in the progression of BMF in DC, particularly through the dysregulation of genomic stability, hematopoiesis, and tumor suppression. Additionally, we propose that these fusion proteins might hold a detrimental role, specifically in inducing proteotoxicity-driven hematopoietic disruptions.

Transcriptome profiling reveals the strategy of thermal tolerance enhancement caused by heat-hardening in Mytilus coruscus

The thick-shell mussel Mytilus coruscus serves as a common sessile intertidal species and holds economic significance as an aquatic organism. M. coruscus often endure higher temperatures than their ideal range during consecutive low tides in the spring. This exposure to elevated temperatures provides them with a thermal tolerance boost, enabling them to adapt to high-temperature events caused by extreme low tides and adverse weather conditions. This phenomenon is referred to as heat-hardening. Some related studies showed the phenomenon of heat-hardening in sessile intertidal species but not reported at the mechanism level based on transcriptome so far. In this study, physiological experiments, gene family identification and transcriptome sequencing were performed to confirm the thermotolerance enhancement based on heat-hardening and explore the mechanism in M. coruscus. A total of 2935 DEGs were identified and the results of the KEGG enrichment showed that seven heat-hardening relative pathways were enriched, including Toll-like receptor signal pathway, Arachidonic acid metabolism, and others. Then, 24 HSP70 members and 36 CYP2 members, were identified, and the up-regulated members are correlated with increasing thermotolerance. Finally, we concluded that the heat-hardening M. coruscus have a better thermotolerance because of the capability of maintaining the integrity and the phenomenon of vasodilation of the gill under thermal stress. Further, the physiological experiments yielded the same conclusions. Overall, this study confirms the thermotolerance enhancement caused by heat-hardening and reveals the survival strategy in M. coruscus. In addition, the conclusion provides a new reference for studying the intertidal species' heat resistance mechanisms to combat extreme heat events and the strategies for dealing with extreme weather in aquaculture under the global warming trend.

The implications of exercise in Drosophila melanogaster: insights into Akt/p38 MAPK/Nrf2 pathway associated with Hsp70 regulation in redox balance maintenance

This study investigated the potential effects of exercise on the responses of energy metabolism, redox balance maintenance, and apoptosis regulation in Drosophila melanogaster to shed more light on the mechanisms underlying the increased performance that this emerging exercise model provides. Three groups were evaluated for seven days: the control (no exercise or locomotor limitations), movement-limited flies (MLF) (no exercise, with locomotor limitations), and EXE (with exercise, no locomotor limitations). The EXE flies demonstrated greater endurance-like tolerance in the swimming test, associated with increased citrate synthase activity, lactate dehydrogenase activity and lactate levels, and metabolic markers in exercise. Notably, the EXE protocol regulated the Akt/p38 MAPK/Nrf2 pathway, which was associated with decreased Hsp70 activation, culminating in glutathione turnover regulation. Moreover, reducing the locomotion environment in the MLF group decreased endurance-like tolerance and did not alter citrate synthase activity, lactate dehydrogenase activity, or lactate levels. The MLF treatment promoted a pro-oxidant effect, altering the Akt/p38 MAPK/Nrf2 pathway and increasing Hsp70 levels, leading to a poorly-regulated glutathione system. Lastly, we demonstrated that exercise could modulate major metabolic responses in Drosophila melanogaster aerobic and anaerobic metabolism, associated with apoptosis and cellular redox balance maintenance in an emergent exercise model.

Plasmodium falciparum infection of human erythroblasts induces transcriptional changes associated with dyserythropoiesis

During development down the erythroid lineage, hematopoietic stem cells undergo dramatic changes to cellular morphology and function in response to a complex and tightly regulated program of gene expression. In malaria infection, Plasmodium spp parasites accumulate in the bone marrow parenchyma, and emerging evidence suggests erythroblastic islands are a protective site for parasite development into gametocytes. Although it has been observed that Plasmodium falciparum infection in late-stage erythroblasts can delay terminal erythroid differentiation and enucleation, the mechanism(s) underlying this phenomenon are unknown. Here, we apply RNA sequencing after fluorescence-activated cell sorting of infected erythroblasts to identify transcriptional responses to direct and indirect interaction with P falciparum. Four developmental stages of erythroid cells were analyzed: proerythroblast, basophilic erythroblast, polychromatic erythroblast, and orthochromatic erythroblast. We found extensive transcriptional changes in infected erythroblasts compared with that in uninfected cells in the same culture, including dysregulation of genes involved in erythroid proliferation and developmental processes. Although some indicators of cellular oxidative and proteotoxic stress were common across all stages of erythropoiesis, many responses were specific to cellular processes associated with developmental stage. Together, our results evidence multiple possible avenues by which parasite infection can induce dyserythropoiesis at specific points along the erythroid continuum, advancing our understanding of the molecular determinants of malaria anemia.

Plasmodium falciparum infection of human erythroblasts induces transcriptional changes associated with dyserythropoiesis

During development down the erythroid lineage, hematopoietic stem cells undergo dramatic changes to cellular morphology and function in response to a complex and tightly regulated program of gene expression. In malaria infection, Plasmodium spp . parasites accumulate in the bone marrow parenchyma, and emerging evidence suggests erythroblastic islands are a protective site for parasite development into gametocytes. While it has been observed that Plasmodium falciparum infection of late-stage erythroblasts can delay terminal erythroid differentiation and enucleation, the mechanism(s) underlying this phenomenon are unknown. Here, we apply RNA-seq after fluorescence-activated cell sorting (FACS) of infected erythroblasts to identify transcriptional responses to direct and indirect interaction with Plasmodium falciparum . Four developmental stages of erythroid cells were analyzed: proerythroblast, basophilic erythroblast, polychromatic erythroblast, and orthochromatic erythroblast. We found extensive transcriptional changes in infected erythroblasts compared to uninfected cells in the same culture, including dysregulation of genes involved in erythroid proliferation and developmental processes. Whereas some indicators of cellular oxidative and proteotoxic stress were common across all stages of erythropoiesis, many responses were specific to cellular processes associated with developmental stage. Together, our results evidence multiple possible avenues by which parasite infection can induce dyserythropoiesis at specific points along the erythroid continuum, advancing our understanding of the molecular determinants of malaria anemia.

Key Points

Erythroblasts at different stages of differentiation have distinct responses to infection by Plasmodium falciparum . P. falciparum infection of erythroblasts alters expression of genes related to oxidative and proteotoxic stress and erythroid development.

Nucleated red blood cells explain most of the association between DNA methylation and gestational age

Determining if specific cell type(s) are responsible for an association between DNA methylation (DNAm) and a given phenotype is important for understanding the biological mechanisms underlying the association. Our EWAS of gestational age (GA) in 953 newborns from the Norwegian MoBa study identified 13,660 CpGs significantly associated with GA (p_Bonferroni<0.05) after adjustment for cell type composition. When the CellDMC algorithm was applied to explore cell-type specific effects, 2,330 CpGs were significantly associated with GA, mostly in nucleated red blood cells [nRBCs; n = 2,030 (87%)]. Similar patterns were found in another dataset based on a different array and when applying an alternative algorithm to CellDMC called Tensor Composition Analysis (TCA). Our findings point to nRBCs as the main cell type driving the DNAm-GA association, implicating an epigenetic signature of erythropoiesis as a likely mechanism. They also explain the poor correlation observed between epigenetic age clocks for newborns and those for adults.

J-domain protein chaperone circuits in proteostasis and disease

The J-domain proteins (JDP) form the largest protein family among cellular chaperones. In cooperation with the Hsp70 chaperone system, these co-chaperones orchestrate a plethora of distinct functions, including those that help maintain cellular proteostasis and development. JDPs evolved largely through the fusion of a J-domain with other protein subdomains. The highly conserved J-domain facilitates the binding and activation of Hsp70s. How JDPs (re)wire Hsp70 chaperone circuits and promote functional diversity remains insufficiently explained. Here, we discuss recent advances in our understanding of the JDP family with a focus on the regulation built around J-domains to ensure correct pairing and assembly of JDP-Hsp70 machineries that operate on different clientele under various cellular growth conditions.

DNA methylation status of DNAJA4 is essential for human erythropoiesis

Aims: To investigate DNA methylation patterns in early and terminal stages of erythropoiesis, and to explore the function of differentially methylated genes in erythropoiesis and erythroid disorders. Materials & methods: Differential analysis of DNA methylation and gene expression during erythropoiesis, as well as weighted gene coexpression network analysis of acute myeloid leukemia was performed. Results: We identified four candidate genes that possessed differential methylation in the promoter regions. DNAJA4 affected proliferation, apoptosis and enucleation during terminal erythropoiesis and was associated with the prognosis of acute myeloid leukemia.  DNAJA4 was specifically highly expressed in erythroleukemia and is associated with DNA methylation. Conclusion: DNAJA4 plays a crucial role for erythropoiesis and is regulated via DNA methylation. Dysregulation of DNAJA4 expression is associated with erythroid disorders.

In Vitro Study of Ineffective Erythropoiesis in Thalassemia: Diverse Intrinsic Pathophysiological Features of Erythroid Cells Derived from Various Thalassemia Syndromes

Defective hemoglobin production and ineffective erythropoiesis contribute to the pathophysiology of thalassemia syndromes. Previous studies in the field of erythropoiesis mainly focused on the severe forms of thalassemia, such as β-thalassemia major, while mechanisms underlying the pathogenesis of other thalassemia syndromes remain largely unexplored. The current study aimed to investigate the intrinsic pathophysiological properties of erythroid cells derived from the most common forms of thalassemia diseases, including α-thalassemia (hemoglobin H and hemoglobin H-Constant Spring diseases) and β-thalassemia (homozygous β⁰-thalassemia and β⁰-thalassemia/hemoglobin E diseases), under an identical in vitro erythroid culture system. Cell proliferation capacity, differentiation velocity, cell death, as well as globin synthesis and the expression levels of erythropoiesis modifying factors were determined. Accelerated expansion was found in erythroblast cells derived from all types of thalassemia, with the highest degree in β⁰-thalassemia/hemoglobin E. Likewise, all types of thalassemia showed limited erythroid cell differentiation, but each of them manifested varying degrees of erythroid maturation arrest corresponding with the clinical severity. Robust induction of HSP70 transcripts, an erythroid maturation-related factor, was found in both α- and β-thalassemia erythroid cells. Increased cell death was distinctly present only in homozygous β⁰-thalassemia erythroblasts and associated with the up-regulation of pro-apoptotic (Caspase 9, BAD, and MTCH1) genes and down-regulation of the anti-apoptotic BCL-XL gene.

Early and Late-Phase 24 h Responses of Stored Red Blood Cells to Recipient-Mimicking Conditions

The 24-hour (24 h) post-transfusion survival of donor red blood cells (RBCs) is an important marker of transfusion efficacy. Nonetheless, within that period, donated RBCs may encounter challenges able to evoke rapid stress-responses. The aim of the present study was to assess the effect of exposure to plasma and body temperature upon stored RBCs under recipient-mimicking conditions in vitro from the first hours "post-transfusion" up to 24 h. For this purpose, packed RBCs from seven leukoreduced CPD/SAGM units were reconstituted with plasma of twenty-seven healthy individuals and incubated for 24 h at 37^oC. Three units were additionally used to examine stress-responses in 3-hour intervals post mixing with plasma (n = 5) until 24 h. All experiments were performed in shortly-, medium-, and long-stored RBCs. Hemolysis, redox, morphology, membrane protein binding and vesiculation parameters were assessed. Even though spontaneous hemolysis was minimal post-reconstitution, it presented a time-dependent increase. A similar time-course profile was evident for the concentration of procoagulant extracellular vesicles and the osmotic fragility (shortly-stored RBCs). On the contrary, mechanical fragility and reactive oxygen species accumulation were characterized by increases in medium-stored RBCs, evident even from the first hours in the recipient-mimicking environment. Finally, exposure to plasma resulted in rapid improvement of morphology, especially in medium-stored RBCs. Overall, some RBC properties vary significantly during the first 24 h post-mixing, at levels different from both the storage ones and the standard end-of-24 h. Such findings may be useful for understanding the performance of RBCs and their possible clinical effects -especially on susceptible recipients- during the first hours post-transfusion.

Proteome remodeling and organelle clearance in mammalian terminal erythropoiesis

PURPOSE OF REVIEW

The differentiation from colony forming unit-erythroid (CFU-E) cells to mature enucleated red blood cells is named terminal erythropoiesis in mammals. Apart from enucleation, several unique features during these developmental stages include proteome remodeling and organelle clearance that are important to achieve hemoglobin enrichment. Here, we review the recent advances in the understanding of novel regulatory mechanisms in these processes, focusing on the master regulators that link these major events during terminal erythropoiesis.

RECENT FINDINGS

Comprehensive proteomic studies revealed a mismatch of protein abundance to their corresponding transcript abundance, which indicates that the proteome remodeling is regulated in a complex way from transcriptional control to posttranslational modifications. Key regulators in organelle clearance were also found to play critical roles in proteome remodeling.

SUMMARY

These studies demonstrate that the complexity of terminal erythropoiesis is beyond the conventional transcriptomic centric perspective. Posttranslational modifications such as ubiquitination are critical in terminal erythroid proteome remodeling that is also closely coupled with organelle clearance.

Chaperone networks are shaped by cellular differentiation and identity

Chaperone expression is developmentally regulated, establishing tissue-specific networks. However, the molecular basis underlying this specificity is mainly unknown. Recent evidence suggests that chaperone network rewiring is mediated, in part, by differentiation transcription factors to fit the proteome folding demands, with implications for the tissue-specific manifestation of protein misfolding diseases.

Hemin accumulation and identification of a heme-binding protein clan in K562 cells by proteomic and computational analysis

Heme (iron protoporphyrin IX) is an essential regulator conserved in all known organisms. We investigated the kinetics of intracellular accumulation of hemin (oxidized form) in human transformed proerythroid K562 cells using [¹⁴ C]-hemin and observed that it is time and temperature-dependent, affected by the presence of serum proteins, as well as the amphipathic/hydrophobic properties of hemin. Hemin-uptake exhibited saturation kinetics as a function of the concentration added, suggesting the involvement of a carrier-cell surface receptor-mediated process. The majority of intracellular hemin accumulated in the cytoplasm, while a substantial portion entered the nucleus. Cytosolic proteins isolated by hemin-agarose affinity column chromatography (HACC) were found to form stable complexes with [⁵⁹ Fe]-hemin. The HACC fractionation and Liquid chromatography-mass spectrometry analysis of cytosolic, mitochondrial, and nuclear protein isolates from K562 cell extracts revealed the presence of a large number of hemin-binding proteins (HeBPs) of diverse ontologies, including heat shock proteins, cytoskeletal proteins, enzymes, and signaling proteins such as actinin a4, mitogen-activated protein kinase 1 as well as several others. The subsequent computational analysis of the identified HeBPs using HemoQuest confirmed the presence of various hemin/heme-binding motifs [C(X)nC, H, Y] in their primary structures and conformations. The possibility that these HeBPs contribute to a heme intracellular trafficking protein network involved in the homeostatic regulation of the pool and overall functions of heme is discussed.