Evolution of the ATP-binding cassette (ABC) transporter superfamily in vertebrates

From Genetics to Function: the Role of ABCA12 in Autism Neurobiology

ASD is a complex neurodevelopmental disorder with genetic, environmental, and molecular roots. Among the thousands of genes that have been associated with ASD, one critical factor has emerged as ABCA12, which plays an important role in lipid transport and metabolism. Traditionally, it has been related to skin disorders but has only recently been implicated in broader brain development and function. Some of the implicated effects include dysregulated lipid homeostasis, neuroinflammation, oxidative stress, and abnormalities in synaptic when the ABCA12 system is dysregulated. All the above processes are related to pathology in ASD. In this review, the emerging function of ABCA12 in autism neurobiology has been discussed; the core base is derived from in vivo models and preclinical studies. In vivo models such as mice and zebrafish that, in the previous studies had earlier shown impairments of ABCA12 which results in social deficiency behaviors but also perform repetitive actions. Based on the effects of the gene on molecular pathways, including neuronal signalling and membrane integrity, and identifying therapeutic approaches targeting ABCA12 or its downstream effects, preclinical studies have contributed to the integration of genetic, functional, and therapeutic perspectives for understanding the contribution of ABCA12 to ASD. These findings may unlock further investigations geared toward unravelling how lipid metabolism intricately influences neurodevelopment with regards to interventions available for use in ASD.

HvStaufenC contributes to the high RNAi efficiency in the 28-spotted ladybeetle, Henosepilachna vigintioctopunctata

RNA interference (RNAi) has been shown to be relatively effective in coleopteran insects, with limited exploration into the molecular mechanisms that underlie this effectiveness. This study specifically examines the 28-spotted ladybeetle, Henosepilachna vigintioctopunctata (Hvig), known for its high RNAi efficiency. Here, we utilized RNAi and CRISPR/Cas9 techniques to identify and validate the genes involved in the RNAi pathway that enhance RNAi efficacy in Hvig. We identified a total of 15 potential genes within the RNAi pathway that may impact RNAi efficiency. The bioassay results showed that only knockdown of HvStaufenC in the 3rd instar larvae could block the abnormal body color phenotype and lethality induced by the subsequent silencing of the two marker genes, HvTH (tyrosine hydroxylase) and HvABCH1 (ATP-binding cassette H transporter gene), respectively. Additionally, successful CRISPR/Cas9-mediated knockout of HvStaufenC led to the generation of stable, heritable mutants that exhibited insensitivity to RNAi, displaying no response to RNAi targeting HvTH and HvABCH1. Compared to the wild-type strain, the HvStaufenC knockout (HvStaufenCKO) mutant females demonstrated a 42 % decrease in oviposition rate and a 41.3 % reduction in egg hatchability. This study demonstrates that HvStaufenC gene is crucial for the RNAi efficiency of Hvig and offers new evidence into the RNAi mechanisms in coleopteran species.

Human ATP-binding proteins: Structural features, functional diversity, and pharmacotherapeutic potential in disease: A review

ATP-binding proteins (ABPs) form diverse and essential protein families across living organisms. Early life forms likely relied on simple chemical reactions for energy, but with the emergence of ABPs and their evolving functions, organisms became capable of more efficient energy storage and utilization, which drove the complexity of metabolic and life processes. By binding and hydrolyzing ATP through conserved structural motifs such as the Walker motifs, ABPs play critical roles in material transport, signal transduction, cellular structure maintenance, motility, and cell cycle regulation. Dysfunctions arising from mutations, deletions, or misregulation of ABPs are linked to a variety of human diseases, including cancer, neurodegenerative disorders, and cardiovascular diseases. The growing recognition of ABPs' significance in disease progression highlights their relevance not only in basic biology but also in clinical applications, particularly as biomarkers and therapeutic targets. This review provides a comprehensive overview of human ABPs, detailing their structural and functional roles, their involvement in disease mechanisms, and the latest advances in understanding their clinical relevance. Additionally, it identifies current research gaps and offers new perspectives for future investigations and therapeutic strategies.

Relationship between melanoma vemurafenib tolerance thresholds and metabolic pathway choice and Wnt signaling involvement

Vemurafenib constitutes an important therapeutic for BRAFV600 mutant melanomas, but despite high initial response rates, resistance to BRAF and MEK inhibitors quickly develops. Here, we performed an integrative analysis of metabolomic consequences and transcriptome alterations to uncover mechanisms involved in adaptive vemurafenib resistance (VemR) development and their relationship with vemurafenib tolerance thresholds. We developed BRAFV600E isogenic models of VemR utilizing M14 and A2058 lines, and patient-derived melanomas with V600E or normal BRAF to verify vemurafenib selectivity. MEK or PI3K inhibitors only partially inhibited VemR cell proliferation, indicating cross-resistance to these inhibitors. MITF and β-catenin levels were induced and treatment with Wnt/β-catenin inhibitor ICG-001 restored vemurafenib sensitivity with concomitant reductions in β-catenin-regulated gene expressions, phospho-ERK1/2, and VemR-induced mitochondrial mass and respiration. Targeted metabolite, MitoPlate-S1, Mito-stress and transcriptome/metabolomic analysis showed that melanoma cells with elevated vemurafenib tolerance thresholds such as A2058 VemR cells utilize Wnt/β-catenin signaling for mitochondrial metabolism while VemR cells with low tolerance such as M14 VemR cells rely on Wnt/β-catenin signaling for pentose phosphate pathway. Pathways associated with cytokine-cytokine receptor, ECM receptor, and neuroactive ligand receptor interactions were similarly enriched in BRAFV600E patient-derived melanoma as M14 and A2058 cells whereas distinct pathways involving cell cycle, DNA replication, Fanconi anemia and DNA repair pathways are upregulated in wild type BRAF expressing patient derived melanoma. These data show for the first time that the metabolic pathway choices made by VemR BRAF mutant melanomas are controlled by vemurafenib tolerance and endurance thresholds and Wnt/β-catenin signaling plays a central role in coordinating expression of genes controlling VemR and metabolic pathway shifts.

Unraveling the triad of hypoxia, cancer cell stemness, and drug resistance

In the domain of addressing cancer resistance, challenges such as limited effectiveness and treatment resistance remain persistent. Hypoxia is a key feature of solid tumors and is strongly associated with poor prognosis in cancer patients. Another significant portion of the development of acquired drug resistance is attributed to tumor stemness. Cancer stem cells (CSCs), a small tumor cell subset with self-renewal and proliferative abilities, are crucial for tumor initiation, metastasis, and intra-tumoral heterogeneity. Studies have shown a significant association between hypoxia and CSCs in the context of tumor resistance. Recent studies reveal a strong link between hypoxia and tumor stemness, which together promote tumor survival and progression during treatment. This review elucidates the interplay between hypoxia and CSCs, as well as their correlation with resistance to therapeutic drugs. Targeting pivotal genes associated with hypoxia and stemness holds promise for the development of novel therapeutics to combat tumor resistance.

Predictive role of ABC transporters in the efficacy of enfortumab vedotin for urothelial carcinoma

Objective

To evaluate the correlation between ATP-binding cassette (ABC) transporter expression and therapeutic efficacy of enfortumab vedotin (EV), an antibody-drug conjugate targeting Nectin-4, in urothelial cancer, as only a few studies have been conducted on this topic.

Patients and methods

This retrospective study included 20 patients with metastatic urothelial carcinoma (mUC), including bladder and upper urinary tract cancers, who were treated with EV at Dokkyo Medical University Hospital between 2022 and 2024. Immunohistochemical staining was performed on formalin-fixed, paraffin-embedded tissue samples. Progression-free survival (PFS) was estimated using the Kaplan-Meier method, and differences between subgroups (e.g., Nectin-4 and ABC transporter expression) were compared using the log-rank test.

Results

Immunohistochemical analysis indicated that tumours with high ABC transporter expression exhibited shorter PFS time and poorer response to EV. Furthermore, a decrease in Nectin-4 expression and an increase in ABC transporter expression were observed as the disease progressed from non-muscle-invasive to muscle-invasive and metastatic. Patients with Nectin-4-positive and ABC transporter-negative tumours had the longest PFS, underscoring the prognostic significance of these biomarkers.

Conclusion

To our knowledge, this study is the first to show a correlation between ABC transporter expression and EV efficacy in urothelial carcinoma. Future research should focus on optimizing treatment strategies based on Nectin-4 and ABC transporter expression to improve outcomes.

Rlip76 in ageing and Alzheimer's disease: Focus on oxidative stress and mitochondrial mechanisms

RLIP76 (Rlip), a stress-responsive protein, plays a multifaceted role in cellular function. This protein acts primarily as a glutathione-electrophile conjugate (GS-E) transporter, crucial for detoxifying hazardous compounds and converting them into mercapturic acids. RLIP76 also modulates cytoskeletal motility and membrane plasticity through its role in the Ral-signaling pathway, interacting with RalA and RalB, key small GTPases involved in growth and metastasis. Beyond its ATP-dependent transport functions in various tissues, RLIP76 also demonstrates GTPase Activating Protein (GAP) activity towards Rac1 and Cdc42, with a preference for Ral-GTP over Ral-GDP. Its functions span critical physiological processes including membrane dynamics, oxidative stress response, and mitochondrial dynamics. The protein's widespread expression and evolutionary conservation underscore its significance. Our lab discovered that Rlip interacts with Alzheimer's disease (AD) proteins, amyloid beta and phosphorylated and induce oxidative stress, mitochondrial dysfnction and synaptic damage in AD. Our in vitro studies revealed that overexpression of Rlip reduces mitochondrial abnormalities. Further, our in vivo studies (Rlip+/- mice) revealed that a partial reduction of Rlip in mice (Rlip+/-), leads to mitochondrial abnormalities, elevated oxidative stress, and cognitive deficits resembling late-onset AD, emphasizing the protein's crucial role in neuronal health and disease. Finally, we discuss the experimental cross-breedings of overexpression of mice Rlip TG/TG or Rlip + /- mice with Alzheimer's disease models - earlyonset 5XFAD, late-onset APPKI and Tau transgenic mice, providing new insights into RLIP76's role in AD progression and development. This review summarizes RLIP76's structure, function, and cellular pathways, highlighting its implications in AD and its potential as a therapeutic target.

Epigenome-wide Association Analysis of Mitochondrial Heteroplasmy Provides Insight into Molecular Mechanisms of Disease

The relationship between mitochondrial DNA (mtDNA) heteroplasmy and nuclear DNA (nDNA) methylation (CpGs) remains to be studied. We conducted an epigenome-wide association analysis of heteroplasmy burden scores across 10,986 participants (mean age 77, 63% women, and 54% non-White races/ethnicities) from seven population-based observational cohorts. We identified 412 CpGs (FDR p < 0.05) associated with mtDNA heteroplasmy. Higher levels of heteroplasmy burden were associated with lower nDNA methylation levels at most significant CpGs. Functional inference analyses of genes annotated to heteroplasmy-associated CpGs emphasized mitochondrial functions and showed enrichment in cardiometabolic conditions and traits. We developed CpG-scores based on heteroplasmy-count associated CpGs (MHC-CpG scores) using elastic net Cox regression in a training cohort. A one-unit higher level of the standardized MHC-CpG scores were associated with 1.26-fold higher hazard of all-cause mortality (95% CI: 1.14, 1.39) and 1.09-fold higher hazard of CVD (95% CI: 1.01-1.17) in the meta-analysis of testing cohorts, adjusting for age, sex, and smoking. These findings shed light on the relationship between mtDNA heteroplasmy and DNA methylation, and the role of heteroplasmy-associated CpGs as biomarkers in predicting all-cause mortality and cardiovascular disease.

Roles of eyestalk in salinity acclimatization of mud crab (Scylla paramamosain) by transcriptomic analysis

Salinity acclimatization refers to the physiological and behavioral adjustments made by crustaceans to adapt to varying salinity environments. The eyestalk, a neuroendocrine organ in crustaceans, plays a crucial role in salinity acclimatization. To elucidate the molecular mechanisms underlying eyestalk involvement in mud crab (Scylla paramamosain) acclimatization, we employed RNA-seq technology to analyze transcriptomic changes in the eyestalk under low (5 ppt) and standard (23 ppt) salinity conditions. This analysis revealed 5431 differentially expressed genes (DEGs), with 2372 upregulated and 3059 downregulated. Notably, these DEGs were enriched in crucial biological pathways like metabolism, osmoregulation, and signal transduction. To validate the RNA-seq data, we further analyzed 15 DEGs of interest using qRT-PCR. Our results suggest a multifaceted role for the eyestalk: maintaining energy homeostasis, regulating hormone synthesis and release, PKA activity, and downstream signaling, and ensuring proper ion and osmotic balance. Furthermore, our findings indicate that the crustacean hyperglycemic hormone (CHH) may function as a key regulator, modulating carbonic anhydrase expression through the activation of the PKA signaling pathway, thereby influencing cellular osmoregulation, and associated metabolic processes. Overall, our study provides valuable insights into unraveling the molecular mechanisms of mud crab acclimatization to low salinity environments.

ATP-binding cassette transporter TaABCG2 contributes to Fusarium head blight resistance by mediating salicylic acid transport in wheat

ATP-binding cassette (ABC) transporters hydrolyse ATP to transport various substrates. Previous studies have shown that ABC transporters are responsible for transporting plant hormones and heavy metals, thus contributing to plant immunity. Herein, we identified a wheat G-type ABC transporter, TaABCG2-5B, that responds to salicylic acid (SA) treatment and is induced by Fusarium graminearum, the primary pathogen causing Fusarium head blight (FHB). The loss-of-function mutation of TaABCG2-5B (ΔTaabcg2-5B) reduced SA accumulation and increased susceptibility to F. graminearum. Conversely, overexpression of TaABCG2-5B (OE-TaABCG2-5B) exerted the opposite effect. Quantification of intracellular SA in ΔTaabcg2-5B and OE-TaABCG2-5B protoplasts revealed that TaABCG2-5B acts as an importer, facilitating the transport of SA into the cytoplasm. This role was further confirmed by Cd2+ absorption experiments in wheat roots, indicating that TaABCG2-5B also participates in Cd2+ transport. Thus, TaABCG2-5B acts as an importer and is crucial for transporting multiple substrates. Notably, the homologous gene TaABCG2-5A also facilitated Cd2+ uptake in wheat roots but did not significantly influence SA accumulation or FHB resistance. Therefore, TaABCG2 could be a valuable target for enhancing wheat tolerance to Cd2+ and improving FHB resistance.

Alzheimer's Disease and Effects of ABCA7 Polymorphisms: A Review

Alzheimer's Disease (AD) is a progressive neurodegenerative disease and the main cause of dementia. Its etiology remains largely unclear, though genetic and environmental factors appear to confer susceptibility to AD development. This study assessed the role of ATP-binding Cassette A Subfamily 7 (ABCA7) genetic polymorphisms, as ongoing research suggests they have a role in the development of AD. We conducted a PubMed, Google Scholar, and Scopus search to identify and assess all AD studies examining ABCA7 variants in different populations and ethnicities. The last search was conducted on February 8, 2023. Inclusion and exclusion criteria were applied and only the studies that met the inclusion criteria were included in this review. Seventeen studies were finally included. According to the results, ABCA7 variants infer different risks for AD among populations with different ancestries. African American populations show a higher risk for AD, carrying the five novel variants rs115550680, rs142076058, rs10405305, rs3764647, and rs567222111. Asian populations also have an increased risk for AD, harboring three variants. ABCA7 genetic variability contributes to AD development and shows racial disparities. African American and Asian populations seem to be at greater risk of developing AD. These results may assist future research efforts for the early and accurate diagnosis of AD. Moreover, further exploration of the mechanisms of ABCA7 in the context of AD could identify potential therapeutic targets.

Transcriptome mining and expression analysis of ABC transporter genes in a monophagous herbivore, Leucinodes orbonalis (Crambidae: Lepidoptera)

Insecticide resistance is a global concern and requires immediate attention to manage dreadful insect pests. One of the resistance mechanisms adopted by insects is through ATP-binding cassette (ABC) transporter proteins. These proteins rapidly transport and eliminate the insecticidal molecules across the lipid membranes (Phase III detoxification mechanism). In the present study, we investigated the potential role of ABC transporter genes in imparting insecticide resistance in field-collected insecticide resistant larvae of eggplant shoot and fruit borer (Leucinodes orbonalis; Crambidae: Lepidoptera). Dose-mortality bioassays against five insecticidal molecules revealed moderate to high levels of insecticide resistance (32.2. to 134.1-fold). Thirty-one genes encoding ABC transporter proteins were mined from the transcriptome resources of L. orbonalis. They were classified under eight sub-families (ABCA to ABCH). Phylogenetic analysis indicated ABCG is the most divergent, composed of nine genes as compared to many other insects. Transcriptome analysis of the insecticide resistant and susceptible strains of L. orbonalis revealed differential expression of 13 ABC transporter genes. The altered expression of these genes was further validated using qRT-PCR. The knockdown studies indicated the involvement of ABCD1 and ABCG2 genes in chlorantraniliprole resistance in the insecticide-resistant strain of L. orbonalis. This study unveils the additional mechanisms employed by L. orbonalis in resisting insecticide toxicity through accelerated excretion mode. These ABCD and ABCG family genes could be candidate targets in developing genome-assisted pest management strategies in the future.

Unveiling the Dynamic Interplay between Cancer Stem Cells and the Tumor Microenvironment in Melanoma: Implications for Novel Therapeutic Strategies

Cutaneous melanoma still represents a significant health burden worldwide, being responsible for the majority of skin cancer deaths. Key advances in therapeutic strategies have significantly improved patient outcomes; however, most patients experience drug resistance and tumor relapse. Cancer stem cells (CSCs) are a small subpopulation of cells in different tumors, including melanoma, endowed with distinctive capacities of self-renewal and differentiation into bulk tumor cells. Melanoma CSCs are characterized by the expression of specific biomarkers and intracellular pathways; moreover, they play a pivotal role in tumor onset, progression and drug resistance. In recent years, great efforts have been made to dissect the molecular mechanisms underlying the protumor activities of melanoma CSCs to provide the basis for novel CSC-targeted therapies. Herein, we highlight the intricate crosstalk between melanoma CSCs and bystander cells in the tumor microenvironment (TME), including immune cells, endothelial cells and cancer-associated fibroblasts (CAFs), and its role in melanoma progression. Specifically, we discuss the peculiar capacities of melanoma CSCs to escape the host immune surveillance, to recruit immunosuppressive cells and to educate immune cells toward an immunosuppressive and protumor phenotype. We also address currently investigated CSC-targeted strategies that could pave the way for new promising therapeutic approaches for melanoma care.

Exploring the Ligand Binding and Conformational Dynamics of the Substrate-Binding Domain 1 of the ABC Transporter GlnPQ

The adenosine triphosphate (ATP)-binding cassette (ABC) importer GlnPQ from Lactococcus lactis has two sequential covalently linked substrate-binding domains (SBDs), which capture the substrates and deliver them to the translocon. The two SBDs differ in their ligand specificities, binding affinities and the distance to the transmembrane domain; interestingly, both SBDs can bind their ligands simultaneously without affecting each other. In this work, we studied the binding of ligands to both SBDs using X-ray crystallography and molecular dynamics simulations. We report three high-resolution structures of SBD1, namely, the wild-type SBD1 with bound asparagine or arginine, and E184D SBD1 with glutamine bound. Molecular dynamics (MD) simulations provide a detailed insight into the dynamics associated with open-closed transitions of the SBDs.

Differing temperature dependencies of functional homologs zebrafish Abcb4 and human ABCB1

The ATP binding cassette (ABC) transporters human ABCB1 and zebrafish (Danio rerio) Abcb4 are functionally homologous multixenobiotic/multidrug (MXR/MDR) efflux transporters that confer the efflux of a broad range of diverse chemical compounds from the cell. As ATPases, the transporters utilize the energy released by ATP cleavage for protein conformation changes and concomitant active transport of substrate compounds. The temperatures, at which human ABCB1 and zebrafish Abcb4 need to function, can substantially differ: Whereas the ambient temperature of human ABCB1, which is that of the human body, is constant, zebrafish Abcb4 has to be active in a wider temperature range as the body temperature of zebrafish can considerably vary, depending on the ambient water temperature (18°C-40°C). Here, we examined the effect of temperature on the ATPase activities of recombinant human ABCB1 and zebrafish Abcb4 generated with the baculovirus expression system. Incubation temperatures for enzyme reactions were set to 37°C and 27°C, corresponding to the human body temperature and the cultivation temperature of zebrafish in our lab, respectively. For stimulation and inhibition of zebrafish Abcb4 and human ABCB1 ATPase activities verapamil and cyclosporin A were added at different concentrations and 50% effect concentrations (EC50) were determined. The different temperatures had a stronger effect on the human ABCB1 than on the zebrafish Abcb4 ATPase: Differences between EC50 values for verapamil at 37°C and 27°C, respectively, were 1.8-fold for human ABCB1 but only 1.2-fold for zebrafish Abcb4. Activation energies (Ea) of basal and verapamil-stimulated ATPases, calculated based on the Arrhenius equation, were 2-fold (basal) and 1.5-fold (verapamil-stimulated) higher for human ABCB1 than for zebrafish Abcb4. The differences between zebrafish Abcb4 and human ABCB1 ATPases in temperature sensitivity and activation energy could be important for the comparison of the functional properties of the two transporter proteins in the context of pharmaco-/toxicokinetics. Related to this, our finding that at equal reaction conditions the zebrafish Abcb4 ATPase activity tended to be generally higher than that of human ABCB1 may also be important, as this may point to a higher substrate compound transport rate of Abcb4.

Insights into the role of non-coding RNAs in the development of insecticide resistance in insects

Pest control heavily relies on chemical pesticides has been going on for decades. However, the indiscriminate use of chemical pesticides often results in the development of resistance in pests. Almost all pests have developed some degree of resistance to pesticides. Research showed that the mechanisms of insecticide resistance in insects encompass metabolic resistance, behavioral resistance, penetration resistance and target-site resistance. Research on the these mechanisms has been mainly focused on the cis-regulatory or trans-regulatory for the insecticide resistance-related genes, with less attention paid to non-coding RNAs (ncRNAs), such as microRNA (miRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA). There has been increased studies focus on understanding how these ncRNAs are involved in post-transcriptional regulation of insecticide resistance-related genes. Besides, the formatted endogenous RNA (ceRNA) regulatory networks (lncRNA/circRNA-miRNA-mRNA) has been identified as a key player in governing insect resistance formation. This review delves into the functions and underlying mechanisms of miRNA, lncRNA, and circRNA in regulating insect resistance. ncRNAs orchestrate insect resistance by modulating the expression of detoxification enzyme genes, insecticide target genes, as well as receptor genes, effectively regulating both target-site, metabolic and penetration resistance in insects. It also explores the regulatory mechanisms of ceRNA networks in the development of resistance. By enhancing our understanding of the mechanisms of ncRNAs in insecticide resistance, it will not only provide valuable insights into the new mechanisms of insecticide resistance but also help to enrich new directions in ncRNAs gene regulation research.

A review of moxidectin vs. other macrocyclic lactones for prevention of heartworm disease in dogs with an appraisal of two commercial formulations

Macrocyclic lactones (MLs) are the only drug class currently licensed for heartworm disease prophylaxis. Macrocyclic lactones kill third- and fourth-stage larvae of Dirofilaria immitis, thus preventing the development of adult worms in dogs, which are responsible for heartworm disease, a potentially life-threatening condition. Despite considerable overlap in terms of endectocide spectrum, several important differences distinguish moxidectin from other MLs. Moxidectin has beneficial pharmacokinetic characteristics, such as a longer half-life and greater tissue distribution compared to ivermectin. Additionally, moxidectin has a greater margin of safety compared to ivermectin in dogs with ABCB1 (previously MDR1) gene-defect, which is commonly recognized in collies and other breeds. Multiple laboratory studies have shown that moxidectin is more effective than other commonly used heartworm preventives against resistant strains of D. immitis. This improved efficacy benefits individual dogs and helps reduce the risk of spreading resistant strains within the community. Despite the presence of proven resistant strains in the United States, non-compliance with preventive measures remains a major factor contributing to the diagnosis of heartworm disease in dogs. In retrospective analyses, the oral moxidectin combination product Simparica Trio® (sarolaner, moxidectin, and pyrantel) was associated with increased compliance, resulting in more time of protection compared to dogs receiving flea/tick and heartworm preventive products separately. Compliance with the extended-release moxidectin injectables ProHeart® 6 and ProHeart® 12 was higher than with monthly heartworm preventives, as they provide 6 months or a full year of protection with one single injection, respectively, and revenues remain in the veterinary clinics as injectable moxidectin cannot be sourced through online retailers.

Integrative Metabolomics, Enzymatic Activity, and Gene Expression Analysis Provide Insights into the Metabolic Profile Differences between the Slow-Twitch Muscle and Fast-Twitch Muscle of Pseudocaranx dentex

The skeletal muscles of teleost fish encompass heterogeneous muscle types, termed slow-twitch muscle (SM) and fast-twitch muscle (FM), characterized by distinct morphological, anatomical, histological, biochemical, and physiological attributes, driving different swimming behaviors. Despite the central role of metabolism in regulating skeletal muscle types and functions, comprehensive metabolomics investigations focusing on the metabolic differences between these muscle types are lacking. To reveal the differences in metabolic characteristics between the SM and FM of teleost, we conducted an untargeted metabolomics analysis using Pseudocaranx dentex as a representative model and identified 411 differential metabolites (DFMs), of which 345 exhibited higher contents in SM and 66 in FM. KEGG enrichment analysis showed that these DFMs were enriched in the metabolic processes of lipids, amino acids, carbohydrates, purines, and vitamins, suggesting that there were significant differences between the SM and FM in multiple metabolic pathways, especially in the metabolism of energy substances. Furthermore, an integrative analysis of metabolite contents, enzymatic activity assays, and gene expression levels involved in ATP-PCr phosphate, anaerobic glycolysis, and aerobic oxidative energy systems was performed to explore the potential regulatory mechanisms of energy metabolism differences. The results unveiled a set of differential metabolites, enzymes, and genes between the SM and FM, providing compelling molecular evidence of the FM achieving a higher anaerobic energy supply capacity through the ATP-PCr phosphate and glycolysis energy systems, while the SM obtains greater energy supply capacity via aerobic oxidation. These findings significantly advance our understanding of the metabolic profiles and related regulatory mechanisms of skeletal muscles, thereby expanding the knowledge of metabolic physiology and ecological adaptation in teleost fish.

The ABC's of Alzheimer risk gene ABCA7

Alzheimer's disease (AD) is a growing problem worldwide. Since ABCA7's identification as a risk gene, it has been extensively researched for its role in the disease. We review its recently characterized structure and what the mechanistic insights teach us about its function. We furthermore provide an overview of identified ABCA7 mutations, their presence in different ancestries and protein domains and how they might cause AD. For ABCA7 PTC variants and a VNTR expansion, haploinsufficiency is proposed as the most likely mode-of-action, although splice events could further influence disease risk. Overall, the need to better understand expression of canonical ABCA7 and its isoforms in disease is indicated. Finally, ABCA7's potential functions in lipid metabolism, phagocytosis, amyloid deposition, and the interplay between these three, is described. To conclude, in this review, we provide a comprehensive overview and discussion about the current knowledge on ABCA7 in AD, and what research questions remain. HIGHLIGHTS: Alzheimer's risk-increasing variants in ABCA7 can be found in up to 7% of AD patients. We review the recently characterized protein structure of ABCA7. We present latest insights in genetics, expression patterns, and functions of ABCA7.

Turning weeds into feed: Ensiling Calotropis gigantea (Giant milkweed) reduces its toxicity and enhances its palatability for dairy cows

Calotropis gigantea (Giant milkweed, GM) has the potential to be utilized as a new feed additive for ruminants, however, the presence of unpalatable or toxic compounds decreases animal feed intake. This study aimed to valorize GM as a potential new feed resource through the chemical and microbial biotransformation of toxic compounds that will henceforth, make the plant palatable for cows. After GM's ensiling using fermentative bacteria, the plant was sampled for UHPLC-MS/MS to analyse the metabolomic changes. Illumina Miseq of the 16 S rRNA fragment genes and ITS1 were used to describe the microbial composition and structure colonizing GM silage and contributing to the biodegradation of toxic compounds. Microbial functions were predicted from metataxonomic data and KEGG pathways analysis. Eight Holstein dairy cows assigned in a cross-over design were supplemented with GM and GM silage to evaluate palatability and effects on milk yield and milk protein. Cows were fed their typical diet prior to the experiment (positive control). After ensiling, 23 flavonoids, 47 amino acids and derivatives increased, while the other 14 flavonoids, 9 amino acids and derivatives decreased, indicating active metabolism during the GM ensiling process. Lactobacillus buchneri, Bacteroides ovatus, and Megasphaera elsdenii were specific to ensiled GM and correlated to functional plant metabolites, while Sphingomonas paucimobilis and Staphylococcus saprophyticus were specific to non-ensiled GM and correlated to the toxic metabolite 5-hydroxymethylfurfural."Xenobiotics biodegradation and metabolism", "cancer overview" and "neurodegenerative disease" were the highly expressed microbial KEGG pathways in non-ensiled GM. Non-ensiled GM is unpalatable for cows and drastically reduces the animal's feed intake, whereas ensiled GM does not reduce feed intake, milk yield and milk protein. This study provides essential information for sustainable animal production by valorizing GM as a new feed additive.

Comparing Transcriptomic Points of Departure to Apical Effect Concentrations For Larval Fathead Minnow Exposed to Chemicals with Four Different Modes Of Action

It is postulated that below a transcriptomic-based point of departure, adverse effects are unlikely to occur, thereby providing a chemical concentration to use in screening level hazard assessment. The present study extends previous work describing a high-throughput fathead minnow assay that can provide full transcriptomic data after exposure to a test chemical. One-day post-hatch fathead minnows were exposed to ten concentrations of three representatives of four chemical modes of action: organophosphates, ecdysone receptor agonists, plant photosystem II inhibitors, and estrogen receptor agonists for 24 h. Concentration response modeling was performed on whole body gene expression data from each exposure, using measured chemical concentrations when available. Transcriptomic points of departure in larval fathead minnow were lower than apical effect concentrations across fish species but not always lower than toxic effect concentrations in other aquatic taxa like crustaceans and insects. The point of departure was highly dependent on measured chemical concentration which were often lower than the nominal concentration. Differentially expressed genes between chemicals within modes of action were compared and often showed statistically significant overlap. In addition, reproducibility between identical exposures using a positive control chemical (CuSO4) and variability associated with the transcriptomic point of departure using in silico sampling were considered. Results extend a transcriptomic-compatible fathead minnow high-throughput assay for possible use in ecological hazard screening.

Involvement of miR-8510a-3p in response to Cry1Ac protoxin by regulating PxABCG3 in Plutella xylostella

Overuse of insecticides has accelerated the evolution of insecticide resistance and created serious environmental concerns worldwide, thus incentivizing development of alternative methods. Bacillus thuringiensis (Bt) is an insecticidal bacterium that has been developed as a biopesticide to successfully control multiple species of pests. It operates by secreting several insect toxins such as Cry1Ac. However, metabolic resistance based on ATP-binding cassette (ABC) transporters may play a crucial role in the development of metabolic resistance to Bt. Here, we characterized an ABCG gene from the agricultural pest Plutella xylostella (PxABCG3) and found that it was highly expressed in a Cry1Ac-resistant strain, up-regulated after Cry1Ac protoxin treatment. Binding miR-8510a-3p to the coding sequence (CDS) of PxABCG3 was then confirmed by a luciferase reporter assay and RNA immunoprecipitation. miR-8510a-3p agomir delivery markedly reduced PxABCG3 expression in vivo and consequently decreased the tolerance of P. xylostella to Cry1Ac, while reduction of miR-8510a-3p significantly increased PxABCG3 expression, accompanied by an increased tolerance to Cry1Ac. Our results suggest that miR-8510a-3p could potentially be used as a novel molecular target against P. xylostella or other lepidopterans, providing novel insights into developing effective and environmentally friendly pesticides.

Effects of Heat Stress on Breast Muscle Metabolomics and Lipid Metabolism Related Genes in Growing Broilers

With global warming and worsening climatic conditions, heat stress (HS) has become a significant challenge affecting the development of poultry production. In this study, we aimed to determine the effects of HS on breast muscle metabolomics and lipid metabolism-related genes in growing broilers. One hundred twenty 29-day-old Arbor Acres broilers were randomly divided into normal temperature (NT; 21 ± 1 °C) and heat stress (HS; 31 ± 1 °C) groups, with six replicates (ten birds in each replicate) in each group, raised for 14 days in two environment chambers at 60 ± 7% relative humidity. Compared with the broilers in the NT group, the average daily food intake, average daily gain and breast muscle yield in the HS group were significantly lower (p < 0.05). The feed conversion ratio was significantly higher in the HS group (p < 0.05). The concentrations of serum corticosterone, free fatty acids and cholesterol and the percentage of abdominal fat of broilers in the HS group were significantly higher (p < 0.05) than the values of the broilers in the NT group. Untargeted breast muscle metabolome analysis revealed 14 upregulated differential metabolites, including glycerophosphocholine, and 27 downregulated differential metabolites, including taurine, in the HS group compared to the NT group; the HS group also displayed significant effects on six metabolic pathways compared to the NT group (p < 0.05). The mRNA expression levels of peroxisome proliferator-activated receptor gamma coactivator-1-alpha, peroxisome proliferator-activated receptor alpha (PPARα) and ATP-binding cassette transporter A1 in the liver and breast muscles were significantly decreased in the HS group compared with the NT group (p < 0.05). The collective findings reveal that HS can cause disorders in breast muscle lipid metabolism in broilers. The PPARα gene might be the key gene in the mechanism of the lipid metabolism that is induced by HS in breast muscle of broilers. These findings provide novel insights into the effects of HS on chicken growth.

Association of ABCG5 and ABCG8 Transporters with Sitosterolemia

Sitosterolemia is a rare genetic lipid disorder, mainly characterized by the accumulation of dietary xenosterols in plasma and tissues. It is caused by inactivating mutations in either ABCG5 or ABCG8 subunits, a subfamily-G ATP-binding cassette (ABCG) transporters. ABCG5/G8 encodes a pair of ABC half transporters that form a heterodimer (G5G8). This heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the hepatobiliary and transintestinal secretion of cholesterol and dietary plant sterols to the surface of hepatocytes and enterocytes, promoting the secretion of cholesterol and xenosterols into the bile and the intestinal lumen. In this way, ABCG5/G8 function in the reverse cholesterol transport pathway and mediate the efflux of cholesterol and xenosterols to high-density lipoprotein and bile salt micelles, respectively. Here, we review the biological characteristics and function of ABCG5/G8, and how the mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumulation and premature atherosclerosis, among other features.

Progress in characterizing ABC multidrug transporters in zebrafish

Zebrafish have proved to be invaluable for modeling complex physiological processes shared by all vertebrate animals. Resistance of cancers and other diseases to drug treatment can occur owing to expression of the ATP-dependent multidrug transporters ABCB1, ABCG2, and ABCC1, either because of expression of these transporters by the target cells to reduce intracellular concentrations of cytotoxic drugs at barrier sites such as the blood-brain barrier (BBB) to limit penetration of drugs into privileged compartments, or by affecting the absorption, distribution, and excretion of drugs administered orally, through the skin, or directly into the bloodstream. We describe the drug specificity, cellular localization, and function of zebrafish orthologs of multidrug resistance ABC transporters with the goal of developing zebrafish models to explore the physiological and pathophysiological functions of these transporters. Finally, we provide context demonstrating the utility of zebrafish in studying cancer drug resistance. Our ultimate goal is to improve treatment of cancer and other diseases which are affected by ABC multidrug resistance transporters.

Characterization and transcriptional expression of ABCG genes in Bactrocera dorsalis: Insights into their roles in fecundity and insecticidal stress response

The ATP-binding cassette (ABC) transporters are essential for regulating various physiological processes and insecticide resistance across different living organisms. ABCG subfamily genes have diverse functions in insects, but little is known about the function of ABCGs in a serious agricultural pest, Bactrocera dorsalis. In this study, 15 BdABCG genes were identified, and BdABCG6 and BdABCG11 were highly expressed in the pupal and adult stages, especially during the transition period from pupae to adults. Silencing of these two genes resulted in a significant reduction of egg production in B. dorsalis, confirming their importance in reproduction. Analysis of tissue expression patterns showed that most genes, including BdABCG1, 3, 8, and 14, exhibited tissue-specificity, with significantly higher expression levels observed in the intestine, Malpighian tubule, and fat body compared to other tissues. Meanwhile, the induction of malathion and avermectin can significantly upregulate the expression of the above four genes. Furthermore, knockdown of BdABCG3 by RNAi significantly increased the mortality of B. dorsalis upon exposure to avermectin, which suggested that BdABCG3 is involved in the transport or metabolism of avermectin in B. dorsalis. Overall, our work provides valuable insights into the function of BdABCGs involved in the reproduction and detoxification system of B. dorsalis.

Reduced expression of the P-glycoprotein gene HaABCB1 is linked to resistance to Bacillus thuringiensis Cry1Ac toxin but not Cry2Ab toxin in Helicoverpa armigera

Rapid evolution of pest resistance to Bt insecticidal proteins presents a serious threat to the sustainable use of Bt crops. The cotton bollworm has been extensively exposed to Bt cotton worldwide and has evolved resistance in laboratory and field. Previous studies have highlighted the significant roles played by the ABC transporter proteins in Bt resistance. In this study, the ORF of HaABCB1 was cloned and analyzed. The expression of HaABCB1 was detected in all developmental stages and tissues, with the highest expression in third instar larvae stage and hindgut tissue. Compared with susceptible strain, a remarkable decrease of HaABCB1 expression in Cry1Ac resistant strain while no significant change in Cry2Ab resistant strain were found. The HaABCB1 expression reduced after susceptible larvae induced by Cry1Ac, but no obvious expression changes after Cry2Ab exposure. RNAi-mediated down-regulation of HaABCB1 could lead to a significant reduction in larval susceptibility to Cry1Ac, but not to Cry2Ab, in susceptible strain. Genetic linkage analysis confirmed that decreased expression of the HaABCB1 mediates resistance to Cry1Ac, but not Cry2Ab resistance. This knowledge contributes to better understanding of the complex molecular mechanisms underlying Bt resistance and provide theoretical foundation for the development of new strategies for pest resistance management.

ATP-dependent transporters: emerging players at the crossroads of immunity and metabolism

Nearly 50 ATP-binding cassette (ABC) transporters are encoded by mammalian genomes. These transporters are characterized by conserved nucleotide-binding and hydrolysis (i.e., ATPase) domains, and power directional transport of diverse substrate classes - ions, small molecule metabolites, xenobiotics, hydrophobic drugs, and even polypeptides - into or out of cells or subcellular organelles. Although immunological functions of ABC transporters are only beginning to be unraveled, emerging literature suggests these proteins have under-appreciated roles in the development and function of T lymphocytes, including many of the key effector, memory and regulatory subsets that arise during responses to infection, inflammation or cancers. One transporter in particular, MDR1 (Multidrug resistance-1; encoded by the ABCB1 locus in humans), has taken center stage as a novel player in immune regulation. Although MDR1 remains widely viewed as a simple drug efflux pump in tumor cells, recent evidence suggests that this transporter fills key endogenous roles in enforcing metabolic fitness of activated CD4 and CD8 T cells. Here, we summarize current understanding of the physiological functions of ABC transporters in immune regulation, with a focus on the anti-oxidant functions of MDR1 that may shape both the magnitude and repertoires of antigen-specific effector and memory T cell compartments. While much remains to be learned about the functions of ABC transporters in immunobiology, it is already clear that they represent fertile new ground, both for the definition of novel immunometabolic pathways, and for the discovery of new drug targets that could be leveraged to optimize immune responses to vaccines and cancer immunotherapies.

Identification and functional analysis of ABC transporter genes related to deltamethrin resistance in Culex pipiens pallens

BACKGROUND

Pathogens that reproduce or develop in mosquitoes can transmit several diseases, endanger human health, and overwhelm health systems. Synthetic pyrethroids are the most widely used insecticides against adult mosquitoes, but their widespread use has led to resistance. The adenosine triphosphate (ATP)-binding cassette (ABC) transporters are involved in the resistance monitoring of insects, but their role and underlying mechanisms in insecticide resistance have not been fully elucidated. In the present study, we identified ABC transporter genes in Culex pipiens and investigated their role in the development of insecticide resistance.

RESULTS

We identified 63 ABC transporter genes in Cx. pipiens and classified them as per the ABC transporter subfamilies. We also performed phylogenetic analysis. The knockdown rate of the mosquitoes orally fed with the ABC transporter inhibitor verapamil increased after deltamethrin treatment compared with that of the control group. Several genes from the ABCB, ABCC, and ABCG subfamilies were highly expressed in resistant mosquitoes. Immunofluorescence analysis revealed that ABCG6032427 was expressed in the head, chest, abdomen, wings, and legs, and the expression was the highest in the legs. Subsequently, knockdown of ABCG6032427 using RNA interference (RNAi) increased the sensitivity of the mosquitoes to deltamethrin, and scanning and transmission electron microscopy revealed that ABCG6032427 knockdown reduced cuticle thickness and the cuticle became loose and irregular.

CONCLUSIONS

ABCG6032427 may modulate cuticle thickness and structure, thus play an important role in the development of deltamethrin resistance in mosquitoes. Thus, it could be a potential target for deltamethrin resistance management in Cx. pipiens. © 2023 Society of Chemical Industry.

A review of the pathophysiology and the role of ion channels on bronchial asthma

Asthma is one of the main non-communicable chronic diseases and affects a huge portion of the population. It is a multifactorial disease, classified into several phenotypes, being the allergic the most frequent. The pathophysiological mechanism of asthma involves a Th2-type immune response, with high concentrations of allergen-specific immunoglobulin E, eosinophilia, hyperreactivity and airway remodeling. These mechanisms are orchestrated by intracellular signaling from effector cells, such as lymphocytes and eosinophils. Ion channels play a fundamental role in maintaining the inflammatory response on asthma. In particular, transient receptor potential (TRP), stock-operated Ca2+ channels (SOCs), Ca2+-activated K+ channels (IKCa and BKCa), calcium-activated chloride channel (TMEM16A), cystic fibrosis transmembrane conductance regulator (CFTR), piezo-type mechanosensitive ion channel component 1 (PIEZO1) and purinergic P2X receptor (P2X). The recognition of the participation of these channels in the pathological process of asthma is important, as they become pharmacological targets for the discovery of new drugs and/or pharmacological tools that effectively help the pharmacotherapeutic follow-up of this disease, as well as the more specific mechanisms involved in worsening asthma.

Assessment of the role of an ABCC transporter TuMRP1 in the toxicity of abamectin to Tetranychus urticae

The rapid evolution of pest resistance threatens the sustainable utilization of bioinsecticides such as abamectin, and so deciphering the molecular mechanisms affecting toxicity and resistance is essential for their long-term application. Historical studies of abamectin resistance in arthropods have mainly focused on mechanisms involving the glutamate-gated chloride channel (GluCl) targets, with the role of metabolic processes less clear. The two-spotted spider mite, Tetranychus urticae, is a generalist herbivore notorious for rapidly developing resistance to pesticides worldwide, and abamectin has been widely used for its control in the field. After reanalyzing previous transcriptome and RNA-seq data, we here identified an ABC transporter subfamily C gene in T. urticae named multidrug resistance-associated protein 1 (TuMRP1), whose expression differed between susceptible and resistant populations. Synergism bioassays with the inhibitor MK-571, the existence of a genetic association between TuMRP1 expression and susceptibility to abamectin, and the effect of RNA interference mediated silencing of TuMRP1 were all consistent with a direct role of this transporter protein in the toxicity of abamectin. Although ABC transporters are often involved in removing insecticidal compounds from cells, our data suggest either an alternative role for these proteins in the mechanism of action of abamectin or highlight an indirect association between their expression and abamectin toxicity.

ABCH2 transporter mediates deltamethrin uptake and toxicity in the malaria vector Anopheles coluzzii

Contact insecticides are primarily used for the control of Anopheles malaria vectors. These chemicals penetrate mosquito legs and other appendages; the first barriers to reaching their neuronal targets. An ATP-Binding Cassette transporter from the H family (ABCH2) is highly expressed in Anopheles coluzzii legs, and further induced upon insecticide exposure. RNAi-mediated silencing of the ABCH2 caused a significant increase in deltamethrin mortality compared to control mosquitoes, coincident with a corresponding increase in 14C-deltamethrin penetration. RT-qPCR analysis and immunolocalization revealed ABCH2 to be mainly localized in the legs and head appendages, and more specifically, the apical part of the epidermis, underneath the cuticle. To unravel the molecular mechanism underlying the role of ABCH2 in modulating pyrethroid toxicity, two hypotheses were investigated: An indirect role, based on the orthology with other insect ABCH transporters involved with lipid transport and deposition of CHC lipids in Anopheles legs which may increase cuticle thickness, slowing down the penetration rate of deltamethrin; or the direct pumping of deltamethrin out of the organism. Evaluation of the leg cuticular hydrocarbon (CHC) content showed no affect by ABCH2 silencing, indicating this protein is not associated with the transport of leg CHCs. Homology-based modeling suggested that the ABCH2 half-transporter adopts a physiological homodimeric state, in line with its ability to hydrolyze ATP in vitro when expressed on its own in insect cells. Docking analysis revealed a deltamethrin pocket in the homodimeric transporter. Furthermore, deltamethrin-induced ATP hydrolysis in ABCH2-expressing cell membranes, further supports that deltamethrin is indeed an ABCH2 substrate. Overall, our findings pinpoint ABCH2 participating in deltamethrin toxicity regulation.

In-Silico Mining of the Toxins Database (T3DB) towards Hunting Prospective Candidates as ABCB1 Inhibitors: Integrated Molecular Docking and Lipid Bilayer-Enhanced Molecular Dynamics Study

Multidrug resistance (MDR) is one of the most problematic issues in chemotherapeutic carcinoma therapy. The ABCB1 transporter, a drug efflux pump overexpressed in cancer cells, has been thoroughly investigated for its association with MDR. Thus, discovering ABCB1 inhibitors can reverse the MDR in cancer cells. In the current work, a molecular docking technique was utilized for hunting the most prospective ABCB1 inhibitors from the Toxin and Toxin-Target Database (T3DB). Based on the docking computations, the most promising T3DB compounds complexed with the ABCB1 transporter were subjected to molecular dynamics (MD) simulations over 100 ns. Utilizing the MM-GBSA approach, the corresponding binding affinities were computed. Compared to ZQU (calc. -49.8 kcal/mol), Emamectin B1a (T3D1043), Emamectin B1b (T3D1044), Vincristine (T3D4016), Vinblastine (T3D4017), and Vindesine (T3D2479) complexed with ABCB1 transporter demonstrated outstanding binding affinities with ΔG_binding values of -93.0, -92.6, -93.8, -92.2, and -90.8 kcal/mol, respectively. The structural and energetic investigations confirmed the constancy of the identified T3DB compounds complexed with the ABCB1 transporter during the 100 ns MD course. To mimic the physiological conditions, MD simulations were conducted for those identified inhibitors complexed with ABCB1 transporter in the presence of a POPC membrane. These findings revealed that Emamectin B1a, Emamectin B1b, Vincristine, Vinblastine, and Vindesine are promising ABCB1 inhibitors that can reverse the MDR. Therefore, subjecting those compounds to further in-vitro and in-vivo investigations is worthwhile.

Factors Determining the Susceptibility of Fish to Effects of Human Pharmaceuticals

The increasing levels and frequencies at which active pharmaceutical ingredients (APIs) are being detected in the environment are of significant concern, especially considering the potential adverse effects they may have on nontarget species such as fish. With many pharmaceuticals lacking environmental risk assessments, there is a need to better define and understand the potential risks that APIs and their biotransformation products pose to fish, while still minimizing the use of experimental animals. There are both extrinsic (environment- and drug-related) and intrinsic (fish-related) factors that make fish potentially vulnerable to the effects of human drugs, but which are not necessarily captured in nonfish tests. This critical review explores these factors, particularly focusing on the distinctive physiological processes in fish that underlie drug absorption, distribution, metabolism, excretion and toxicity (ADMET). Focal points include the impact of fish life stage and species on drug absorption (A) via multiple routes; the potential implications of fish's unique blood pH and plasma composition on the distribution (D) of drug molecules throughout the body; how fish's endothermic nature and the varied expression and activity of drug-metabolizing enzymes in their tissues may affect drug metabolism (M); and how their distinctive physiologies may impact the relative contribution of different excretory organs to the excretion (E) of APIs and metabolites. These discussions give insight into where existing data on drug properties, pharmacokinetics and pharmacodynamics from mammalian and clinical studies may or may not help to inform on environmental risks of APIs in fish.

Comparative genetic, biochemical, and biophysical analyses of the four E. coli ABCF paralogs support distinct functions related to mRNA translation

Multiple paralogous ABCF ATPases are encoded in most genomes, but the physiological functions remain unknown for most of them. We herein compare the four Escherichia coli K12 ABCFs - EttA, Uup, YbiT, and YheS - using assays previously employed to demonstrate EttA gates the first step of polypeptide elongation on the ribosome dependent on ATP/ADP ratio. A Δ uup knockout, like Δ ettA , exhibits strongly reduced fitness when growth is restarted from long-term stationary phase, but neither Δ ybiT nor Δ yheS exhibits this phenotype. All four proteins nonetheless functionally interact with ribosomes based on in vitro translation and single-molecule fluorescence resonance energy transfer experiments employing variants harboring glutamate-to-glutamine active-site mutations (EQ ₂ ) that trap them in the ATP-bound conformation. These variants all strongly stabilize the same global conformational state of a ribosomal elongation complex harboring deacylated tRNA ^Val in the P site. However, EQ ₂ -Uup uniquely exchanges on/off the ribosome on a second timescale, while EQ ₂ -YheS-bound ribosomes uniquely sample alternative global conformations. At sub-micromolar concentrations, EQ ₂ -EttA and EQ ₂ -YbiT fully inhibit in vitro translation of an mRNA encoding luciferase, while EQ ₂ -Uup and EQ ₂ -YheS only partially inhibit it at ~10-fold higher concentrations. Moreover, tripeptide synthesis reactions are not inhibited by EQ ₂ -Uup or EQ ₂ -YheS, while EQ ₂ -YbiT inhibits synthesis of both peptide bonds and EQ ₂ -EttA specifically traps ribosomes after synthesis of the first peptide bond. These results support the four E. coli ABCF paralogs all having different activities on translating ribosomes, and they suggest that there remains a substantial amount of functionally uncharacterized "dark matter" involved in mRNA translation.

Cognitive decline in diabetic mice predisposed to Alzheimer's disease is greater than in wild type

In this work, we tested the hypothesis that the development of dementia in individuals with type 2 diabetes (T2DM) requires a genetic background of predisposition to neurodegenerative disease. As a proof of concept, we induced T2DM in middle-aged hAPP NL/F mice, a preclinical model of Alzheimer's disease. We show that T2DM produces more severe behavioral, electrophysiological, and structural alterations in these mice compared with wild-type mice. Mechanistically, the deficits are not paralleled by higher levels of toxic forms of Aβ or by neuroinflammation but by a reduction in γ-secretase activity, lower levels of synaptic proteins, and by increased phosphorylation of tau. RNA-seq analysis of the cerebral cortex of hAPP NL/F and wild-type mice suggests that the former could be more susceptible to T2DM because of defects in trans-membrane transport. The results of this work, on the one hand, confirm the importance of the genetic background in the severity of the cognitive disorders in individuals with T2DM and, on the other hand, suggest, among the involved mechanisms, the inhibition of γ-secretase activity.

Structure and Mechanism of Human ABC Transporters

ABC transporters are essential for cellular physiology. Humans have 48 ABC genes organized into seven distinct families. Of these genes, 44 (in five distinct families) encode for membrane transporters, of which several are involved in drug resistance and disease pathways resulting from transporter dysfunction. Over the last decade, advances in structural biology have vastly expanded our mechanistic understanding of human ABC transporter function, revealing details of their molecular arrangement, regulation, and interactions, facilitated in large part by advances in cryo-EM that have rendered hitherto inaccessible targets amenable to high-resolution structural analysis. As a result, experimentally determined structures of multiple members of each of the five families of ABC transporters in humans are now available. Here we review this recent progress, highlighting the physiological relevance of human ABC transporters and mechanistic insights gleaned from their direct structure determination. We also discuss the impact and limitations of model systems and structure prediction methods in understanding human ABC transporters and discuss current challenges and future research directions.

ABCG2 in Acute Myeloid Leukemia: Old and New Perspectives

Despite recent advances, prognosis of acute myeloid leukemia (AML) remains unsatisfactory due to poor response to therapy or relapse. Among causes of resistance, over-expression of multidrug resistance (MDR) proteins represents a pivotal mechanism. ABCG2 is an efflux transporter responsible for inducing MDR in leukemic cells; through its ability to extrude many antineoplastic drugs, it leads to AML resistance and/or relapse, even if conflicting data have been reported to date. Moreover, ABCG2 may be co-expressed with other MDR-related proteins and is finely regulated by epigenetic mechanisms. Here, we review the main issues regarding ABCG2 activity and regulation in the AML clinical scenario, focusing on its expression and the role of polymorphisms, as well as on the potential ways to inhibit its function to counteract drug resistance to, eventually, improve outcomes in AML patients.

ABCB1 and ABCC1 Function during TGF-β-Induced Epithelial-Mesenchymal Transition: Relationship between Multidrug Resistance and Tumor Progression

Multidrug resistance (MDR) and induction of metastasis are some of the puzzles encountered during cancer chemotherapy. The MDR phenotype is associated with overexpression of ABC transporters, involved in drug efflux. Metastasis originates from the epithelial-mesenchymal transition (EMT), in which cells acquire a migratory phenotype, invading new tissues. ABC transporters' role during EMT is still elusive, though cells undergoing EMT exhibit enhanced ABCB1 expression. We demonstrated increased ABCB1 expression but no change in activity after TGF-β-induced EMT in A549 cells. Moreover, ABCB1 inhibition by verapamil increased snail and fibronectin expression, an event associated with upregulation of ABCB1, evidencing coincident cell signaling pathways leading to ABCB1 and EMT-related markers transcription, rather than a direct effect of transport. Additionally, for the first time, increased ABCC1 expression and activity was observed after EMT, and use of ABCC1 inhibitors partially inhibited EMT-marker snail, although increased ABCC1 function translated into collateral sensibility to daunorubicin. More investigations must be done to evaluate the real benefits that the gain of ABC transporters might have on the process of metastasis. Considering ABCC1 is involved in the stress response, affecting intracellular GSH content and drug detoxification, this transporter could be used as a therapeutic target in cancer cells undergoing EMT.

ABC transporters linked to multiple herbicide resistance in blackgrass (Alopecurus myosuroides)

Enhanced detoxification is a prominent mechanism protecting plants from toxic xenobiotics and endows resistance to diverse herbicide chemistries in grass weeds such as blackgrass (Alopecurus myosuroides). The roles of enzyme families which impart enhanced metabolic resistance (EMR) to herbicides through hydroxylation (phase 1 metabolism) and/or conjugation with glutathione or sugars (phase 2) have been well established. However, the functional importance of herbicide metabolite compartmentalisation into the vacuole as promoted by active transport (phase 3), has received little attention as an EMR mechanism. ATP-binding cassette (ABC) transporters are known to be important in drug detoxification in fungi and mammals. In this study, we identified three distinct C-class ABCCs transporters namely AmABCC1, AmABCC2 and AmABCC3 in populations of blackgrass exhibiting EMR and resistance to multiple herbicides. Uptake studies with monochlorobimane in root cells, showed that the EMR blackgrass had an enhanced capacity to compartmentalize fluorescent glutathione-bimane conjugated metabolites in an energy-dependent manner. Subcellular localisation analysis using transient expression of GFP-tagged AmABCC2 assays in Nicotiana demonstrated that the transporter was a membrane bound protein associated with the tonoplast. At the transcript level, as compared with herbicide sensitive plants, AmABCC1 and AmABCC2 were positively correlated with EMR in herbicide resistant blackgrass being co-expressed with AmGSTU2a, a glutathione transferase (GST) involved in herbicide detoxification linked to resistance. As the glutathione conjugates generated by GSTs are classic ligands for ABC proteins, this co-expression suggested AmGSTU2a and the two ABCC transporters delivered the coupled rapid phase 2/3 detoxification observed in EMR. A role for the transporters in resistance was further confirmed in transgenic yeast by demonstrating that the expression of either AmABCC1 or AmABCC2, promoted enhanced tolerance to the sulfonylurea herbicide, mesosulfuron-methyl. Our results link the expression of ABCC transporters to enhanced metabolic resistance in blackgrass through their ability to transport herbicides, and their metabolites, into the vacuole.

Identification and characterization of ABC proteins in an important rice insect pest, Cnaphalocrocis medinalis unveil their response to Cry1C toxin

Rice leaffolder (Cnaphalocrocis medinalis) is an important insect pest in paddy fields. Due to their essential role in the physiology and insecticidal resistance, ATP-binding cassette (ABC) proteins were studied in many insects. In this study, we identified the ABC proteins in C. medinalis through genomic data and analyzed their molecular characteristics. A total of 37 sequences with nucleotide-binding domain (NBD) were identified as ABC proteins and belonged to eight families (ABCA-ABCH). Four structure styles of ABC proteins were found in C. medinalis, including full structure, half structure, single structure, and ABC2 structure. In addition to these structures, TMD-NBD-TMD, NBD-TMD-NBD, and NBD-TMD-NBD-NBD were found in C. medinalis ABC proteins. Docking studies suggested that in addition to the soluble ABC proteins, other ABC proteins including ABCC4, ABCH1, ABCG3, ABCB5, ABCG1, ABCC7, ABCB3, ABCA3, and ABCC5 binding with Cry1C had higher weighted scores. The upregulation of ABCB1 and downregulation of ABCB3, ABCC1, ABCC7, ABCG1, ABCG3, and ABCG6 were associated with the C. medinalis response to Cry1C toxin. Collectively, these results help elucidate the molecular characteristics of C. medinalis ABC proteins, pave the way for further functional studies of C. medinalis ABC proteins, including their interaction with Cry1C toxin, and provide potential insecticide targets.

Genome-scale analysis of ABC transporter genes and characterization of the ABCC type transporter genes in the oriental armyworm, Mythimna separata (Walker)

The oriental armyworm Mythimna separata is a polyphagous, migratory corn pest in China and other Asian countries. Transgenic Bacillus thuringiensis (Bt) corn may effectively control this insect pest. Several reports have suggested that ATP-binding cassette (ABC) transporter proteins may act as receptors that bind Bt toxins. However, our knowledge about ABC transporter proteins in M. separata is limited. We identified 43 ABC transporter genes in the M. separata genome by bioinformatics prediction. Evolutionary tree analysis grouped these 43 genes into 8 subfamilies, ABCA to ABCH. Among the 13 ABCC subfamily genes, the transcript levels of MsABCC2 and MsABCC3 were upregulated. In addition, RT-qPCR analyses of these two potentials showed that both were predominantly expressed in the midgut tissue. Knock-down of MsABCC2, but not MsABCC3, decreased Cry1Ac susceptibility as indicated by increased larval weight and reduced larval mortality. This suggested that MsABCC2 might play a more important role in Cry1Ac toxicity and that it is a putative Cry1Ac receptor in M. separata. Together, these findings provide unique and valuable information for future elucidating of the role of ABC transporter genes in M. separata, which is highly valuable and important for the long-term application of Bt insecticidal protein.

Cholesterol accumulation in ovarian follicles causes ovulation defects in Abca1a -/- Japanese medaka (Oryzias latipes)

ATP-binding cassette A1 (ABCA1) is a membrane protein, which exports excess cellular cholesterol to generate HDL to reduce the risk of the onset of cardiovascular diseases (CVD). In addition, ABCA1 exerts pleiotropic effects on such as inflammation, tissue repair, and cell proliferation and migration. In this study, we explored the novel physiological roles of ABCA1 using Japanese medaka (Oryzias latipes), a small teleost fish. Three Abca1 genes were found in the medaka genome. ABCA1A and ABCA1C exported cholesterol to generate nascent HDL as human ABCA1 when expressed in HEK293 cells. To investigate their physiological roles, each Abca1-deficient fish was generated using the CRISPR-Cas9 system. Abca1a -/- female medaka was found to be infertile, while Abca1b -/- and Abca1c -/- female medaka were fertile. In vitro ovarian follicle culture suggested that Abca1a deficiency causes ovulation defects. In the ovary, ABCA1A was expressed in theca cells, an outermost layer of the ovarian follicle. Total cholesterol content of Abca1a -/- ovary was significantly higher than that of the wild-type, while estrogen and progestin contents were compatible with those of the wild-type. Furthermore, cholesterol loading to the wild-type follicles caused ovulation defects. These results suggest that ABCA1A in theca cells regulates cholesterol content in the ovarian follicles and its deficiency inhibits successful ovulation through cholesterol accumulation in the ovarian follicle.

Anti-Hypoxia Nanoplatforms for Enhanced Photosensitizer Uptake and Photodynamic Therapy Effects in Cancer Cells

Photodynamic therapy (PDT) holds great promise in cancer eradication due to its target selectivity, non-invasiveness, and low systemic toxicity. However, due to the hypoxic nature of many native tumors, PDT is frequently limited in its therapeutic effect. Additionally, oxygen consumption during PDT may exacerbate the tumor's hypoxic condition, which stimulates tumor proliferation, metastasis, and invasion, resulting in poor treatment outcomes. Therefore, various strategies have been developed to combat hypoxia in PDT, such as oxygen carriers, reactive oxygen supplements, and the modulation of tumor microenvironments. However, most PDT-related studies are still conducted on two-dimensional (2D) cell cultures, which fail to accurately reflect tissue complexity. Thus, three-dimensional (3D) cell cultures are ideal models for drug screening, disease simulation and targeted cancer therapy, since they accurately replicate the tumor tissue architecture and microenvironment. This review summarizes recent advances in the development of strategies to overcome tumor hypoxia for enhanced PDT efficiency, with a particular focus on nanoparticle-based photosensitizer (PS) delivery systems, as well as the advantages of 3D cell cultures.

Polymorphic renal transporters and cisplatin's toxicity in urinary bladder cancer patients: current perspectives and future directions

Urinary bladder cancer (UBC) holds a potentially profound social burden and affects over 573,278 new cases annually. The disease's primary risk factors include occupational tobacco smoke exposure and inherited genetic susceptibility. Over the past 30 years, a number of treatment modalities have emerged, including cisplatin, a platinum molecule that has demonstrated effectiveness against UBC. Nevertheless, it has severe dose-limiting side effects, such as nephrotoxicity, among others. Since intracellular accumulation of platinum anticancer drugs is necessary for cytotoxicity, decreased uptake or enhanced efflux are the root causes of platinum resistance and response failure. Evidence suggests that genetic variations in any transporter involved in the entry or efflux of platinum drugs alter their kinetics and, to a significant extent, determine patients' responses to them. This review aims to consolidate and describe the major transporters and their polymorphic variants in relation to cisplatin-induced toxicities and resistance in UBC patients. We concluded that the efflux transporters ABCB1, ABCC2, SLC25A21, ATP7A, and the uptake transporter OCT2, as well as the organic anion uptake transporters OAT1 and OAT2, are linked to cisplatin accumulation, toxicity, and resistance in urinary bladder cancer patients. While suppressing the CTR1 gene's expression reduced cisplatin-induced nephrotoxicity and ototoxicity, inhibiting the expression of the MATE1 and MATE2-K genes has been shown to increase cisplatin's nephrotoxicity and resistance. The roles of ABCC5, ABCA8, ABCC10, ABCB10, ABCG1, ATP7B, ABCG2, and mitochondrial SLC25A10 in platinum-receiving urinary bladder cancer patients should be the subject of further investigation.

Molecular dynamics study of Cl- permeation through cystic fibrosis transmembrane conductance regulator (CFTR)

The recent elucidation of atomistic structures of Cl^- channel CFTR provides opportunities for understanding the molecular basis of cystic fibrosis. Despite having been activated through phosphorylation and provided with ATP ligands, several near-atomistic cryo-EM structures of CFTR are in a closed state, as inferred from the lack of a continuous passage through a hydrophobic bottleneck region located in the extracellular portion of the pore. Here, we present repeated, microsecond-long molecular dynamics simulations of human CFTR solvated in a lipid bilayer and aqueous NaCl. At equilibrium, Cl^- ions enter the channel through a lateral intracellular portal and bind to two distinct cationic sites inside the channel pore but do not traverse the narrow, de-wetted bottleneck. Simulations conducted in the presence of a strong hyperpolarizing electric field led to spontaneous Cl^- translocation events through the bottleneck region of the channel, suggesting that the protein relaxed to a functionally open state. Conformational changes of small magnitude involving transmembrane helices 1 and 6 preceded ion permeation through diverging exit routes at the extracellular end of the pore. The pore bottleneck undergoes wetting prior to Cl^- translocation, suggesting that it acts as a hydrophobic gate. Although permeating Cl^- ions remain mostly hydrated, partial dehydration occurs at the binding sites and in the bottleneck. The observed Cl^- pathway is largely consistent with the loci of mutations that alter channel conductance, anion binding, and ion selectivity, supporting the model of the open state of CFTR obtained in the present study.

Antiproliferative and cytotoxic effects of sesquiterpene lactones isolated from Ambrosia artemisiifolia on human adenocarcinoma and normal cell lines

CONTEXT

Ambrosia artemisiifolia L. (Asteraceae) contains sesquiterpene lactones as characteristic secondary metabolites. Many of these compounds exert antiproliferative and cytotoxic effects.

OBJECTIVE

To isolate the sesquiterpene lactones from the aerial part of A. artemisiifolia and to elucidate their cytotoxic, antiproliferative and antibacterial effects.

MATERIALS AND METHODS

The compounds were identified by one-dimensional (1D) and 2D NMR, HR-MS spectroscopy from the methanol extract. Isolated compounds were investigated for their cytotoxic and antiproliferative effects on human colonic adenocarcinoma cell lines and human embryonal lung fibroblast cell line using MTT assay. The selectivity of the sesquiterpenes was calculated towards the normal cell line. To check the effect of drug interactions between compounds and doxorubicin, multidrug-resistant Colo 320 cells were used.

RESULTS

A new seco-psilostachyinolide derivative, 1,10-dihydro-1'-noraltamisin, and seven known compounds were isolated from the methanol extract. Acetoxydihydrodamsin had the most potent cytotoxic effect on sensitive (Colo205) cell line (IC₅₀ = 7.64 µM), also the strongest antiproliferative effect on Colo205 (IC₅₀ = 5.14 µM) and Colo320 (IC₅₀ = 3.67 µM) cell lines. 1'-Noraltamisin (IC₅₀ = 8.78 µM) and psilostachyin (IC₅₀ = 5.29 µM) showed significant antiproliferative effects on the multidrug-resistant Colo320 cell line and had moderate selectivity against human embryonal lung fibroblast cell line. Psilostachyin C exhibited cytotoxic effects on Colo205 cells (IC₅₀ = 26.60 µM). None of the isolated compounds inhibited ABCB1 efflux pump (EP; P-glycoprotein) or the bacterial EPs.

DISCUSSION AND CONCLUSIONS

Acetoxydihydrodamsin, 1'-noraltamisin, and psilostachyin showed the most remarkable cytotoxic and antiproliferative activity on tumour cell lines and exerted selectivity towards MRC-5 cell line.

Unraveling cellular and molecular mechanisms of acid stress tolerance and resistance in marine species: New frontiers in the study of adaptation to ocean acidification

Since the industrial revolution, fossil fuel combustion has led to a 30 %-increase of the atmospheric CO₂ concentration, also increasing the ocean partial CO₂ pressure. The consequent lowered surface seawater pH is termed ocean acidification (OA) and severely affects marine life on a global scale. Cellular and molecular responses of marine species to lowered seawater pH have been studied but information on the mechanisms driving the tolerance of adapted species to comparatively low seawater pH is limited. Such information may be obtained from species inhabiting sites with naturally low water pH that have evolved remarkable abilities to tolerate such conditions. This review gathers information on current knowledge about species naturally facing low water pH conditions and on cellular and molecular adaptive mechanisms enabling the species to survive under, and even benefit from, adverse pH conditions. Evidences derived from case studies on naturally acidified systems and on resistance mechanisms will guide predictions on the consequences of future adverse OA scenarios for marine biodiversity.

Microbial Multitrophic Communities Drive the Variation of Antibiotic Resistome in the Gut of Soil Woodlice (Crustacea: Isopoda)

Multitrophic communities inhabit in soil faunal gut, including bacteria, fungi, and protists, which have been considered a hidden reservoir for antibiotic resistance genes (ARGs). However, there is a dearth of research focusing on the relationships between ARGs and multitrophic communities in the gut of soil faunas. Here, we studied the contribution of multitrophic communities to variations of ARGs in the soil woodlouse gut. The results revealed diverse and abundant ARGs in the woodlouse gut. Network analysis further exhibited strong connections between key ecological module members and ARGs, suggesting that multitrophic communities in the keystone ecological cluster may play a pivotal role in the variation of ARGs in the woodlouse gut. Moreover, long-term application of sewage sludge significantly altered the woodlice gut resistome and interkingdom communities. The variation portioning analysis indicated that the fungal community has a greater contribution to variations of ARGs than bacterial and protistan communities in the woodlice gut after long-term application of sewage sludge. Together, our results showed that changes in gut microbiota associated with agricultural practices (e.g., sewage sludge application) can largely alter the gut interkingdom network in ecologically relevant soil animals, with implications for antibiotic resistance, which advances our understanding of the microecological drivers of ARGs in terrestrial ecosystem.

ABCC1 transporter exports the immunostimulatory cyclic dinucleotide cGAMP

The DNA sensor cyclic GMP-AMP synthase (cGAS) is important for antiviral and anti-tumor immunity. cGAS generates cyclic GMP-AMP (cGAMP), a diffusible cyclic dinucleotide that activates the antiviral response through the adaptor protein stimulator of interferon genes (STING). cGAMP cannot passively cross cell membranes, but recent advances have established a role for extracellular cGAMP as an "immunotransmitter" that can be imported into cells. However, the mechanism by which cGAMP exits cells remains unknown. Here, we identifed ABCC1 as a direct, ATP-dependent cGAMP exporter in mouse and human cells. We show that ABCC1 overexpression enhanced cGAMP export and limited STING signaling and that loss of ABCC1 reduced cGAMP export and potentiated STING signaling. We demonstrate that ABCC1 deficiency exacerbated cGAS-dependent autoimmunity in the Trex1-/- mouse model of Aicardi-Goutières syndrome. Thus, ABCC1-mediated cGAMP export is a key regulatory mechanism that limits cell-intrinsic activation of STING and ameliorates STING-dependent autoimmune disease.