Lipid flippases ATP9A and ATP9B form a complex and contribute to the exocytic pathway from the Golgi

Type IV P-type ATPases (P4-ATPases) serve as lipid flippases, translocating membrane lipids from the exoplasmic (or luminal) leaflet to the cytoplasmic leaflet of lipid bilayers. In mammals, these P4-ATPases are localized to distinct subcellular compartments. ATP8A1 and ATP9A, members of the P4-ATPase family, are involved in endosome-mediated membrane trafficking, although the roles of P4-ATPases in the exocytic pathway remain to be clarified. ATP9A and ATP9B are located in the TGN, with ATP9A also present in endosomal compartments. This study revealed the overlapping roles of ATP9A and ATP9B in transporting VSVG from the Golgi to the plasma membrane within the exocytic pathway. Furthermore, we demonstrated that the flippase activities of ATP9A and ATP9B were crucial for the transport process. Notably, we discovered the formation of homomeric and/or heteromeric complexes between ATP9A and ATP9B. Therefore, ATP9A and ATP9B play a role in the exocytic pathway from the Golgi to the plasma membrane, forming either homomeric or heteromeric complexes.

Alternating hemiplegia of childhood associated mutations in Atp1a3 reveal diverse neurological alterations in mice

Pathogenic variants in the neuronal Na+/K+ ATPase transmembrane ion transporter (ATP1A3) cause a spectrum of neurological disorders including alternating hemiplegia of childhood (AHC). The most common de novo pathogenic variants in AHC are p.D801N (~40 % of patients) and p.E815K (~25 % of patients), which lead to early mortality by spontaneous death in mice. Nevertheless, knowledge of the development of clinically relevant neurological phenotypes without the obstacle of premature death, is critical for the identification of pathophysiological mechanisms and ultimately, for the testing of therapeutic strategies in disease models. Here, we used hybrid vigor attempting to mitigate the fragility of AHC mice and then performed behavioral, electrophysiological, biochemical, and molecular testing to comparatively analyze mice that carry either of the two most common AHC patient observed variants in the Atp1a3 gene. Collectively, our data reveal the presence but also the differential impact of the p.D801N and p.E815K variants on disease relevant alterations such as spontaneous and stress-induced paroxysmal episodes, motor function, behavioral and neurophysiological activity, and neuroinflammation. Our alternate AHC mouse models with their phenotypic deficits open novel avenues for the investigation of disease biology and therapeutic testing for ATP1A3 research.

The molecular mechanism and therapeutic landscape of copper and cuproptosis in cancer

Copper, an essential micronutrient, plays significant roles in numerous biological functions. Recent studies have identified imbalances in copper homeostasis across various cancers, along with the emergence of cuproptosis, a novel copper-dependent form of cell death that is crucial for tumor suppression and therapeutic resistance. As a result, manipulating copper levels has garnered increasing interest as an innovative approach to cancer therapy. In this review, we first delineate copper homeostasis at both cellular and systemic levels, clarifying copper's protumorigenic and antitumorigenic functions in cancer. We then outline the key milestones and molecular mechanisms of cuproptosis, including both mitochondria-dependent and independent pathways. Next, we explore the roles of cuproptosis in cancer biology, as well as the interactions mediated by cuproptosis between cancer cells and the immune system. We also summarize emerging therapeutic opportunities targeting copper and discuss the clinical associations of cuproptosis-related genes. Finally, we examine potential biomarkers for cuproptosis and put forward the existing challenges and future prospects for leveraging cuproptosis in cancer therapy. Overall, this review enhances our understanding of the molecular mechanisms and therapeutic landscape of copper and cuproptosis in cancer, highlighting the potential of copper- or cuproptosis-based therapies for cancer treatment.

Allosteric modulation of SERCA pumps in health and disease: structural dynamics, posttranslational modifications, and therapeutic potential

Sarco/endoplasmic reticulum (SR/ER) Ca2+-ATPase (SERCA) pumps are ubiquitous membrane proteins in all eukaryotic cells, playing a central role in maintaining intracellular calcium homeostasis by re-sequestering Ca2+ ions from the cytosol into the SR/ER at the expense of ATP hydrolysis. SERCA pumps are well-characterized components of the calcium transport machinery in the cell, playing a role in various physiological processes, including muscle contraction, energy metabolism, secretion exocytosis, gene expression, synaptic transmission, cell survival, and fertilization. Allosteric regulation of SERCA pumps plays a key role in health and disease, and modulation of the SERCA pumps has emerged as a therapeutic approach for the treatment of cardiovascular, muscular, metabolic, and neurodegenerative disorders. In this review, we provide a comprehensive overview of the structural dynamics underlying allosteric modulation of SERCA, focusing on the effects of endogenous regulatory proteins, Ca2+ ions, ATP, and small-molecule effectors on the dynamics and function of the pump. We also examine in detail the role of posttranslational modifications as allosteric modulators of SERCA function, focusing on the oxidative modifications S-glutathionylation, S-nitrosylation, tyrosine nitration, and carbonylation, and non-oxidative modifications that include SUMOylation, acetylation, O-GlcNAcylation, phosphorylation, and ubiquitination. Finally, we discuss the therapeutic potential and challenges of allosteric modulation of SERCA pumps, including the design of small-molecule effectors, microRNA-based interventions, and targeted strategies that modulate SERCA posttranslational regulation. Overall, this review aims to bridge the gap between the mechanisms underlying allosteric modulation of SERCA and the translation of basic science discoveries into effective therapies targeting SERCA pumps.

Open or closed: pH modulation and calcification by foraminifera

Marine calcifying organisms precipitate their shells either in equilibrium with seawater or under strict biological control. Here, we show that these two options represent two ends of a spectrum. In species with a more "closed" system, rates of H+ removal and Ca2+ uptake are high and exceed the amount of ions required for calcification. This explains the relatively low Mg/Ca of the calcite of this species by dilution of the [Mg2+] in the calcifying fluid. Conversely, in species with a more open system, the H+ and Ca2+ fluxes are lower, with more seawater exchanged between the environment and calcifying fluid, explaining the relatively high Mg/Ca in these foraminifera. In either of these species, mitochondria were found to be located at the site where the Ca2+/H+ exchange takes place and the mitochondrial density aligned with the rate of pumping. These findings highlight the crucial role of transmembrane transporters and mitochondria in foraminifera calcification and explain the species-specific elemental signatures.

ATPase copper transporting beta attenuates malignant features with high expression as an indicator of favorable prognosis in breast cancer

BACKGROUND

ATPase copper transporting beta (ATP7B) functions as a copper-transporting ATPase that ejects copper from cells. Although high expression of ATP7B has been reported to increase cisplatin resistance, its role in breast cancer (BC) remains unclear. This study aimed to elucidate the function of ATP7B in BC cells and its significance in patients with BC.

METHODS

The mRNA and protein expression levels of ATP7B were evaluated in BC and non-cancerous mammary cell lines. Polymerase chain reaction (PCR) array analysis was conducted to determine the correlation between ATP7B and 84 cancer-related genes. ATP7B knockdown was performed using small interfering RNA, and cell proliferation, invasiveness, and migration were analyzed. The associations between the mRNA and protein expression of ATP7B and clinicopathological factors were also investigated in 156 patients with BC.

RESULTS

ATP7B was found to be highly expressed in estrogen receptor-positive and human epidermal growth factor receptor 2-positive BC cell lines. PCR array analysis revealed a significant correlation between the expression level of ATP7B and those of cadherin 1, estrogen receptor 1, and MET proto-oncogene. ATP7B knockdown significantly increased the proliferation, invasiveness, and migration of MDA-MB-361 and MDA-MB-415 cells. Patients with high ATP7B expression at the mRNA and protein levels experienced favorable prognoses. In addition, ATP7B expression level was identified as an independent prognostic factor in multivariate analysis.

CONCLUSIONS

ATP7B is involved in promoting anti-cancer activities of tumor suppressors in BC cells across different subtypes and is considered a prognostic marker for BC.

CRISPR-Cas9 Mediated Gene Editing Platform Through Callus-to-Plant Regeneration and Functional Analysis of DoALA4─DoALA6 in Dendrobium officinale

Dendrobium orchids are well known for their great horticultural and medicinal values; however, the CRISPR/Cas9 gene editing system for Dendrobium species still needs to be improved. Therefore, this study aims to establish a CRISPR/Cas9-based functional validation system using Dendrobium officinale as a model species for the Dendrobium genus and to validate the DoALA4─DoALA6 genes, which may relate to growth and disease resistance. We first conducted a bioinformatics analysis of the P-type ATPase gene family in D. officinale, revealing the evolutionary diversity of P-type ATPase genes in orchids. Second, we inserted the GFP gene into the vector of CRISPR/Cas9 gene editing system to enhance the selection efficiency of genome-edited plants. Comparative analysis showed that different explants exhibited varying transformation efficiencies, ranging from 5% to 46.2%. Considering the regeneration capability, survival rate and gene editing efficiency, we selected callus as the transformation explant. Third, we used this editing system to generate DoALA4─DoALA6 mutants. Phenotypic observations of the mutants and inoculation of D. officinale with Sclerotium rolfsii indicated that DoALA4─DoALA6 are crucial for the growth of D. officinale and its resistance to southern blight disease. This efficient and stable CRISPR/Cas9 platform offers a foundation for further gene studies and Dendrobium breeding.

Nitric oxide enhances copper tolerance by regulating cell wall composition and copper transporting-related transcripts in cotton roots

Little is known about nitric oxide (NO)-mediated cotton plants' response to copper (Cu) stress and the underlying tolerance mechanism. It was hypothesized that NO can alleviate Cu toxicity to cotton roots by regulating the root cell wall composition and the transcription of Cu ion transporting-related genes. Cu stress significantly increased NO synthase (EC 1.14.14.47) activity, leading to elevated endogenous NO content. Cu excess-induced growth inhibition was reversed by sodium nitroprusside (SNP, NO donor) application but exacerbated by cPTIO (NO scavenger) addition. The SNP + Cu treatment promoted more Cu ions accumulation in roots and less Cu ions transportation to leaves than Cu treatment, which also produced the largest Cu uptake amount per plant among all treatments. The concentration of cell wall pectin was significantly enhanced by 16.95% by the SNP application. Pectin methylesterase activity was up-regulated by 30.86% (p < 0.05), thus resulting in a reduction of 10.39% in pectin methylesterification degree in the Cu + SNP treatment than in Cu stress alone; additionally, Cu chaperons COX17, CCH, and ATX1, Cu chelator MT2, and Cu homeostasis regulator SPL7 exhibited higher transcriptional levels. Collectively, NO improved cotton roots' tolerance to Cu stress through the enhancement of Cu ions binding to cell wall due to increased polysaccharide biosynthesis and pectin demethylesterification degree, and via the promotion of Cu ions sequestration owing to up-regulated expressions of Cu chaperones and chelators. These findings should have significant implications for the phytoremediation of Cu-contaminated soils by using cotton plants, which needs further validation under field conditions.

Structure of the [Ca]E2P intermediate of Ca2+-ATPase 1 from Listeria monocytogenes

Active transport by P-type Ca2+-ATPases maintain internal calcium stores and a low cytosolic calcium concentration. Structural studies of mammalian sarco/endoplasmic reticulum Ca2+-ATPases (SERCA) have revealed several steps of the transport cycle, but a calcium-releasing intermediate has remained elusive. Single-molecule FRET studies of the bacterial Ca2+-ATPase LMCA1 revealed an intermediate of the transition between so-called [Ca]E1P and E2P states and suggested that calcium release from this intermediate was the essentially irreversible step of transport. Here, we present a 3.5 Å resolution cryo-EM structure for a four-glycine insertion mutant of LMCA1 in a lipid nanodisc obtained under conditions with calcium and ATP and adopting such an intermediate state, denoted [Ca]E2P. The cytosolic domains are positioned in the E2P-like conformation, while the calcium-binding transmembrane (TM) domain adopts a calcium-bound E1P-ADP-like conformation. Missing density for the E292 residue at the calcium site (the equivalent of SERCA1a E309) suggests flexibility and a site poised for calcium release and proton uptake. The structure suggests a mechanism where ADP release and re-organization of the cytoplasmic domains precede calcium release.

Transition metal transporting P-type ATPases: terminal metal-binding domains serve as sensors for autoinhibitory tails

Copper is an essential micronutrient and yet is highly toxic to cells at elevated concentrations. P1B-ATPase proteins are critical for this regulation, providing active extrusion across cellular membranes. One unique molecular adaptation of P1B-ATPases compared to other P-type ATPases is the presence of metal-binding domains (MBDs) at the cytosolic termini, which however are poorly characterized with an elusive mechanistic role. Here we present the MBD architecture in metal-free and metal-bound forms of the archetype Cu+-specific P1B-ATPase LpCopA, determined using NMR. The MBD is composed of a flexible tail and a structured core with a metal ion binding site defined by three sulfur atoms, one of which is pertinent to the so-called CXXC motif. Furthermore, we demonstrate that the MBD rather than being involved in ion delivery likely serves a regulatory role, which is dependent on the classical P-type ATPase E1-E2 transport mechanism. Specifically, the flexible tail appears responsible for autoinhibition while the metal-binding core is used for copper sensing. This model is validated by a conformation-sensitive and MBD-targeting nanobody that can structurally and functionally replace the flexible tail. We propose that autoinhibition of Cu+-ATPases occurs at low copper conditions via MBD-mediated interference with the soluble domains of the ATPase core and that metal transport is enabled when copper levels rise, through metal-induced dissociation of the MBD. This allows P1B-ATPase 'vacuum cleaners' to tune their own activity, balancing the levels of critical micronutrients in the cells.

A Soluble Expression Construct of the Isolated Catalytic Domain of Plasmodium falciparum ATP4 Exhibits ATPase Activity Independent of a γ-Phosphate Receiving Aspartate

The sodium/proton-exchanging ATPase of Plasmodium falciparum malaria parasites, PfATP4, is an emerging drug target. Inhibition results in detrimental cell swelling due to cytosolic accumulation of sodium and alkalization. PfATP4 is a sodium-releasing type II P-type ATPase restricted to apicomplexan parasites. Experimental data on structure-function relationships of the isolated protein are absent. Here, we produced and purified the soluble catalytic domain of PfATP4 and evaluated kinetic properties by in vitro phosphate colorimetry. The protein exhibited Mg2+-dependent ATPase activity at the same order of magnitude as the native cellular PfATP4 and was insensitive to the presence of sodium. AlphaFold 3-based structure and ATP/Mg2+ interaction predictions identified key residues of the nucleotide binding domain (Lys619, Lys652, Arg703). Replacement of the lysines by methionine decreased the enzymatic activity to one quarter. Individual mutation of the putative Mg2+-coordinating Asp865 of the phosphorylation domain was tolerated, while a joint replacement with Asp869 decreased ATPase again to one quarter. Mutation of the putative γ-phosphate receiving Asp451 maintained the rate of Pi release. Our data attribute typical functional roles for P-type ATPases to the basic and acidic residues of the soluble PfATP4 catalytic domain and show that its ATP hydrolysis is independent of phosphorylation of Asp451.

Heterozygous Missense Variants in the ATPase Phospholipid Transporting 9A Gene, ATP9A, Alter Dendritic Spine Maturation and Cause Dominantly Inherited Nonsyndromic Intellectual Disability

Intellectual disability is a neurodevelopmental disorder, affecting 2%-3% of the population, with a genetic cause in the majority of cases. ATP9A (Online Mendelian Inheritance in Man (OMIM)⁣∗609126, NM_006045.3) has recently been added to the list of candidate genes involved in this disorder with the identification of biallelic truncating variants in patients with a neurodevelopmental disorder. In this study, we propose a novel mode of inheritance for ATP9A-related disorders with the identification of five de novo heterozygous missense variants (p.(Thr393Arg), p.(Glu400Gln), p.(Lys461Glu), p.(Gly552Ala), and p.(His713Asp)), in patients with intellectual disability. In a patient with a similar phenotype, we also identified two truncating variants in ATP9A (p.(Arg145⁣∗), p.(Glu901⁣∗)), adding a novel family to the six already described in the literature with the recessive mode of inheritance. Functional studies were performed to assess the pathogenicity of these variants. Overexpression of four selected missense mutant forms of Atp9a in HeLa cells and in primary neuronal cultures led to a loss of mature dendritic spines. In HeLa cells, the endosomal localization of the protein encoded by three of these missense variants was preserved whereas the fourth remained blocked in the endoplasmic reticulum. To mimic the effect on neuronal morphology and spine density of nonsense variants, small hairpin RNAs (shRNAs) were used. They induced a decreased expression of ATP9A, affecting the neuronal arborization by decreasing the number of dendrites per neuron. Our results therefore demonstrate the pathogenicity of ATP9A heterozygous missense variants and confirm the role of ATP9A in neuronal maturation and in brain wiring during development. They strengthen the association of ATP9A with neurodevelopmental disorders and demonstrate that a double mode of inheritance should be considered for ATP9A-related disorders.

The role of interplay between the plant plasma membrane H+-ATPase and its lipid environment

The mechanisms behind the regulation of plasma membrane (PM) P-type H+-ATPase in plant cells mediated by lipid-protein interactions and lateral heterogeneity of the plasma membrane are discussed. This review will focus on 1) the structural organization and mechanisms of the catalytic cycle of the enzyme, 2) phosphorylation as the primary mechanism of pump regulation; 3) the possible role of lateral heterogeneity of the plasma membrane in this process, as well as 4) the role of lipids in the H+-ATPase biosynthesis and its delivery to the plasma membrane. In addition, 5) the potential role of membrane lipids in the H+-ATPase co-localisation with secondary active transporters is speculated.

The Physiological Responses of Tea to pH and Cd Conditions and the Effect of the CsHMA2 on Cd Transport

Soil acidification in tea (Camellia sinensis L.) gardens leads to nutrient depletion, inhibits the growth of tea plants, reduces tea quality, and activates heavy metals such as cadmium (Cd) in the soil. To clarify the impact of soil pH under acidified conditions on tea plant growth physiology and the key genes involved in Cd2+ transport in tea plants, this study planted 'Longjing 43' under different pH levels (4.0, 4.5, and 5.5) and Cd concentrations (T1 = 0 mg L-1, T2 = 0.01 mg L-1, T3 = 0.05 mg L-1, and T4 = 0.2 mg L-1). The results showed that the concentration of Cd in tea plants from highest to lowest was root > stem > mature leaves > young leaves. Under T4, with decreasing pH, the total chlorophyll significantly decreased, the Fv/Fm significantly decreased, stomatal aperture reduced, and net photosynthetic rate and transpiration rate significantly decreased. In the T4 treatment at pH = 4.0, the contents of free proline and malondialdehyde were both the highest, while superoxide dismutase (SOD), peroxidase (POD), and catalase from micrococcus lysodeiktic (CAT) showed a significant negative correlation with pH. By screening the tea genome data, a total of nine CsHMAs involved in metal ion transport were identified. The qRT-PCR results indicated that the expression level of CsHMA2 was the highest in young leaves of tea, and CsHMA2 was localized on the cell membrane. Under T4 and pH = 4.0, transient overexpression of CsHMA2 enhanced the ability of tea to transport Cd2+, whereas transient silencing of CsHMA2 weakened this ability. These findings not only help understand how tea adapts and regulates its physiological processes in acidic environments but also provide an important theoretical basis and technical guidance for soil improvement in tea gardens, the control of heavy metal pollution, and the optimization of tea quality.

The correlation between mitochondria-associated endoplasmic reticulum membranes (MAMs) and Ca2+ transport in the pathogenesis of diseases

Mitochondria and the endoplasmic reticulum (ER) are vital organelles that influence various cellular physiological and pathological processes. Recent evidence shows that about 5%-20% of the mitochondrial outer membrane is capable of forming a highly dynamic physical connection with the ER, maintained at a distance of 10-30 nm. These interconnections, known as MAMs, represent a relatively conserved structure in eukaryotic cells, acting as a critical platform for material exchange between mitochondria and the ER to maintain various aspects of cellular homeostasis. Particularly, ER-mediated Ca2+ release and recycling are intricately associated with the structure and functionality of MAMs. Thus, MAMs are integral in intracellular Ca2+ transport and the maintenance of Ca2+ homeostasis, playing an essential role in various cellular activities including metabolic regulation, signal transduction, autophagy, and apoptosis. The disruption of MAMs observed in certain pathologies such as cardiovascular and neurodegenerative diseases as well as cancers leads to a disturbance in Ca2+ homeostasis. This imbalance potentially aggravates pathological alterations and disease progression. Consequently, a thorough understanding of the link between MAM-mediated Ca2+ transport and these diseases could unveil new perspectives and therapeutic strategies. This review focuses on the changes in MAMs function during disease progression and their implications in relation to MAM-associated Ca2+ transport.

Substrates, regulation, cellular functions, and disease associations of P4-ATPases

P4-ATPases, a subfamily of the P-type ATPase superfamily, play a crucial role in translocating membrane lipids from the exoplasmic/luminal leaflet to the cytoplasmic leaflet. This process generates and regulates transbilayer lipid asymmetry. These enzymes are conserved across all eukaryotes, and the human genome encodes 14 distinct P4-ATPases. Initially identified as aminophospholipid translocases, P4-ATPases have since been found to translocate other phospholipids, including phosphatidylcholine, phosphatidylinositol, and even glycosphingolipids. Recent advances in structural analysis have significantly improved our understanding of the lipid transport machinery associated with P4-ATPases, as documented in recent reviews. In this review, we highlight the emerging evidence related to substrate diversity, the regulation of cellular localization, enzymatic activities, and their impact on organism homeostasis and diseases.

Identification and expression analysis of P-type ATPase IIIA subfamily in Puccinia Striiformis f. sp. tritici

BACKGROUND

Puccinia striiformis f. sp. tritici (Pst) causes wheat stripe (yellow) rust disease, which is one of the most destructive diseases affecting wheat worldwide. ATPases, a class of membrane proteins, play an important role in material exchange and signal transduction both within and outside biological cells by transporting ions and phospholipids. In plant pathogens, P-type ATPases primarily participate in pathogen development and virulence regulation. However, the P-type ATPase of subfamily IIIA (PMA) has not yet been identified in Pst. To investigate the potential functions of the PMA gene family in Pst, we conducted a genome-wide bioinformatics analysis and examined the expression profiles of the PMA gene family.

RESULTS

Six PMA genes were identified in the genome of P. striiformis f. sp. tritici (CYR34 race). The PMA proteins encoded by these genes ranged in length from 811 to 960 amino acids (aa). Each of the six PMA genes contained a typical ATPase IIIA H superfamily domain and was distributed across four chromosomes. Thirty-six major cis-regulatory elements were detected within the PMA gene family members. Elements such as the CGTCA-motif and TGACG-motif play significant roles in responding to environmental stresses and hormone signals. Quantitative PCR analysis revealed that the expression of the PMA04 gene was generally higher at 9 °C under various temperature stresses. The PMA06 gene typically exhibited higher expression levels at 16 °C. During the infection of Pst, the expression levels of PMA04, PMA05, and PMA06 were elevated at 72 h post treatment.

CONCLUSIONS

Our results indicate that the PMA gene family in the CYR34 strain comprises six PMA genes, which are crucial for managing temperature stress and pathogen infection, and exhibit a distinctive splicing pattern. This study not only identifies a target and direction for the development of new, efficient, and environmentally friendly control agents for wheat stripe rust but also establishes a foundation for analyzing its pathogenic mechanisms.

Mutational analysis of an antimalarial drug target, PfATP4

Among new antimalarials discovered over the past decade are multiple chemical scaffolds that target Plasmodium falciparum P-type ATPase (PfATP4). This essential protein is a Na+ pump responsible for the maintenance of Na+ homeostasis. PfATP4 belongs to the type two-dimensional (2D) subfamily of P-type ATPases, for which no structures have been determined. To gain better insight into the structure/function relationship of this validated drug target, we generated a homology model of PfATP4 based on sarco/endoplasmic reticulum Ca2+ ATPase, a P2A-type ATPase, and refined the model using molecular dynamics in its explicit membrane environment. This model predicted several residues in PfATP4 critical for its function, as well as those that impart resistance to various PfATP4 inhibitors. To validate our model, we developed a genetic system involving merodiploid states of PfATP4 in which the endogenous gene was conditionally expressed, and the second allele was mutated to assess its effect on the parasite. Our model predicted residues involved in Na+ coordination as well as the phosphorylation cycle of PfATP4. Phenotypic characterization of these mutants involved assessment of parasite growth, localization of mutated PfATP4, response to treatment with known PfATP4 inhibitors, and evaluation of the downstream consequences of Na+ influx. Our results were consistent with modeled predictions of the essentiality of the critical residues. Additionally, our approach confirmed the phenotypic consequences of resistance-associated mutations as well as a potential structural basis for the fitness cost associated with some mutations. Taken together, our approach provides a means to explore the structure/function relationship of essential genes in haploid organisms.

Bacterial Metallostasis: Metal Sensing, Metalloproteome Remodeling, and Metal Trafficking

Transition metals function as structural and catalytic cofactors for a large diversity of proteins and enzymes that collectively comprise the metalloproteome. Metallostasis considers all cellular processes, notably metal sensing, metalloproteome remodeling, and trafficking (or allocation) of metals that collectively ensure the functional integrity and adaptability of the metalloproteome. Bacteria employ both protein and RNA-based mechanisms that sense intracellular transition metal bioavailability and orchestrate systems-level outputs that maintain metallostasis. In this review, we contextualize metallostasis by briefly discussing the metalloproteome and specialized roles that metals play in biology. We then offer a comprehensive perspective on the diversity of metalloregulatory proteins and metal-sensing riboswitches, defining general principles within each sensor superfamily that capture how specificity is encoded in the sequence, and how selectivity can be leveraged in downstream synthetic biology and biotechnology applications. This is followed by a discussion of recent work that highlights selected metalloregulatory outputs, including metalloproteome remodeling and metal allocation by metallochaperones to both client proteins and compartments. We close by briefly discussing places where more work is needed to fill in gaps in our understanding of metallostasis.

Generating Multistate Conformations of P-type ATPases with a Conditional Diffusion Model

Understanding and predicting the diverse conformational states of membrane proteins is essential for elucidating their biological functions. Despite advancements in computational methods, accurately capturing these complex structural changes remains a significant challenge. Here, we introduce a computational approach to generate diverse and biologically relevant conformations of membrane proteins using a conditional diffusion model. Our approach integrates forward and backward diffusion processes, incorporating state classifiers and additional conditioners to control the generation gradient of conformational states. We specifically targeted the P-type ATPases, a critical family of membrane transporters, and constructed a comprehensive data set through a combination of experimental structures and molecular dynamics simulations. Our model, incorporating a graph neural network with specialized membrane constraints, demonstrates exceptional accuracy in generating a wide range of P-type ATPase conformations associated with different functional states. This approach represents a meaningful step forward in the computational generation of membrane protein conformations using AI and holds promise for studying the dynamics of other membrane proteins.

Molecular Structure of the Na+,K+-ATPase α4β1 Isoform in Its Ouabain-Bound Conformation

Na+,K+-ATPase is the active ion transport system that maintains the electrochemical gradients for Na+ and K+ across the plasma membrane of most animal cells. Na+,K+-ATPase is constituted by the association of two major subunits, a catalytic α and a glycosylated β subunit, both of which exist as different isoforms (in mammals known as α1, α2, α3, α4, β1, β2 and β3). Na+,K+-ATPase α and β isoforms assemble in different combinations to produce various isozymes with tissue specific expression and distinct biochemical properties. Na+,K+-ATPase α4β1 is only found in male germ cells of the testis and is mainly expressed in the sperm flagellum, where it plays a critical role in sperm motility and male fertility. Here, we report the molecular structure of Na+,K+-ATPase α4β1 at 2.37 Å resolution in the ouabain-bound state and in the presence of beryllium fluoride. Overall, Na+,K+-ATPase α4 structure exhibits the basic major domains of a P-Type ATPase, resembling Na+,K+-ATPase α1, but has differences specific to its distinct sequence. Dissimilarities include the site where the inhibitor ouabain binds. Molecular simulations indicate that glycosphingolipids can bind to a putative glycosphingolipid binding site, which could potentially modulate Na+,K+-ATPase α4 activity. This is the first experimental evidence for the structure of Na+,K+-ATPase α4β1. These data provide a template that will aid in better understanding the function Na+,K+-ATPase α4β1 and will be important for the design and development of compounds that can modulate Na+,K+-ATPase α4 activity for the purpose of improving male fertility or to achieve male contraception.

Recent Advances in Understanding the Regulatory Mechanism of Plasma Membrane H+-ATPase through the Brassinosteroid Signaling Pathway

The polyhydroxylated steroid phytohormone brassinosteroid (BR) controls many aspects of plant growth, development and responses to environmental changes. Plasma membrane (PM) H+-ATPase, the well-known PM proton pump, is a central regulator in plant physiology, which mediates not only plant growth and development, but also adaptation to stresses. Recent studies highlight that PM H+-ATPase is at least partly regulated via the BR signaling. Firstly, the BR cell surface receptor BRASSINOSTEROID-INSENSITIVE 1 (BRI1) and multiple key components of BR signaling directly or indirectly influence PM H+-ATPase activity. Secondly, the SMALL AUXIN UP RNA (SAUR) gene family physically interacts with BRI1 to enhance organ development of Arabidopsis by activating PM H+-ATPase. Thirdly, RNA-sequencing (RNA-seq) assays showed that the expression of some SAUR genes is upregulated under the light or sucrose conditions, which is related to the phosphorylation state of the penultimate residue of PM H+-ATPase in a time-course manner. In this review, we describe the structural and functional features of PM H+-ATPase and summarize recent progress towards understanding the regulatory mechanism of PM H+-ATPase by BRs, and briefly introduce how PM H+-ATPase activity is modulated by its own biterminal regions and the post-translational modifications.

Investigating MerR's Selectivity: The Crosstalk Between Cadmium and Copper Under Elevated Stress Conditions

Bacteria respond to metal pollution through sensors that control the uptake and the detoxification machineries. Specificity in metal recognition is therefore a prerequisite for triggering the appropriate response, particularly when facing a mixture of metals. In response to Cu+, the purple bacterium Rubrivivax gelatinosus induces the efflux Cu+-ATPase CopA by the Cu+ regulator CopR. However, genetic analyses have suggested the presence of additional regulators. Here, we show that CadR, the Cd2+ sensor, is involved in Cd2+ and Cu+ tolerance and demonstrate that CopR and CadR share common target genes. Interestingly, expression of the Cu+ detoxification and efflux (CopI/CopA) system was induced by Cd2+ and downregulated in the double mutant copRcadR-. This double mutant was more sensitive to low Cu+ concentration than the single copR- mutant, and accumulation of coproporphyrin III pointed to a significantly decreased expression of CopA. Furthermore, analyses of Cd2+ toxicity in the cadR- mutant suggested that although CopR is Cu+ selective, CopR is involved in Cd2+ response since the addition of Cu+ alleviates Cd2+ toxicity. Based on our current knowledge of metal transport across the inner membrane, Cd2+ and Cu+ do not share common efflux routes nor do they share common regulators. Nevertheless, the crosstalk between Cd2+ and Cu+ tolerance systems is demonstrated in the present study. The modulation of Cu+ detoxification by a Cd2+ regulator in vivo places emphasis on the relaxed selectivity, under elevated metal concentration, in MerR regulators.

The structure and function of P5A-ATPases

Endoplasmic reticulum (ER) membrane resident P5A-ATPases broadly affect protein biogenesis and quality control, and yet their molecular function remains debated. Here, we report cryo-EM structures of a P5A-ATPase, CtSpf1, covering multiple transport intermediates of the E1 → E1-ATP → E1P-ADP → E1P → E2P → E2.Pi → E2 → E1 cycle. In the E2P and E2.Pi states a cleft spans the entire membrane, holding a polypeptide cargo molecule. The cargo includes an ER luminal extension, pinpointed as the C-terminus in the E2.Pi state, which reenters the membrane in E2P. The E1 structure harbors a cytosol-facing cavity that is blocked by an insertion we refer to as the Plug-domain. The Plug-domain is nestled to key ATPase features and is displaced in the E1P-ADP and E1P states. Collectively, our findings are compatible with a broad range of proteins as cargo, with the P5A-ATPases serving a role in membrane removal of helices, although insertion/secretion cannot be excluded, as well as with a mechanistic role of the Plug-domain.

The MYC2 and MYB43 transcription factors cooperate to repress HMA2 and HMA4 expression, altering cadmium tolerance in Arabidopsis thaliana

Cadmium (Cd) represents a hazardous heavy metal, prevalent in agricultural soil due to industrial and agricultural expansion. Its propensity for being absorbed by edible plants, even at minimal concentrations, and subsequently transferred along the food chain poses significant risks to human health. Accordingly, it is imperative to investigate novel genes and mechanisms that govern Cd tolerance and detoxification in plants. Here, we discovered that the transcription factor MYC2 directly binds to the promoters of HMA2 and HMA4 to repress their expression, thereby altering the distribution of Cd in plant tissues and negatively regulating Cd stress tolerance. Additionally, molecular, biochemical, and genetic analyses revealed that MYC2 interacts and cooperates with MYB43 to negatively regulate the expression of HMA2 and HMA4 and Cd stress tolerance. Notably, under Cd stress conditions, MYC2 undergoes degradation, thereby alleviating its inhibitory effect on HMA2 and HMA4 expression and plant tolerance to Cd stress. Thus, our study highlights the dynamic regulatory role of MYC2, in concert with MYB43, in regulating the expression of HMA2 and HMA4 under both normal and Cd stress conditions. These findings present MYC2 as a promising target for directed breeding efforts aimed at mitigating Cd accumulation in edible plant roots.

Genome wide analysis of HMA gene family in Hydrangea macrophylla and characterization of HmHMA2 in response to aluminum stress

Aluminum toxicity poses a significant threat to plant growth, especially in acidic soils. Heavy metal ATPases (HMAs) are crucial for transporting heavy metal ions across plant cell membranes, yet their role in Al3+ transport remains unexplored. This study identified eight HmHMA genes in the genome of Hydrangea macrophylla, categorizing them into two major clades based on phylogenetic relationships. These genes were found unevenly distributed across six chromosomes. Detailed analysis of their physicochemical properties, collinearity, and gene structure was conducted. RNA-seq and qRT-PCR analyses revealed that specific HmHMA genes, notably HmHMA2, were predominantly expressed in roots and flowers under Al3+ stress, indicating their potential role in Al3+ tolerance. HmHMA2 showed significant expression in roots, especially under Al3+ stress conditions, and when expressed in yeast cells, it conferred resistance to aluminum and zinc but increased sensitivity to cadmium. Overexpression of HmHMA2 in hydrangea leaf discs significantly improved Al3+ tolerance, reduced oxidative stress markers like hydrogen peroxide and malondialdehyde, and enhanced antioxidant enzyme activity such as SOD, POD and CAT compared to controls. These findings shed lights on the potential role of HmHMAs in Al transport and tolerance in H. macrophylla.

Role of Na+-K+ ATPase Alterations in the Development of Heart Failure

Na+-K+ ATPase is an integral component of cardiac sarcolemma and consists of three major subunits, namely the α-subunit with three isoforms (α1, α2, and α3), β-subunit with two isoforms (β1 and β2) and γ-subunit (phospholemman). This enzyme has been demonstrated to transport three Na and two K ions to generate a trans-membrane gradient, maintain cation homeostasis in cardiomyocytes and participate in regulating contractile force development. Na+-K+ ATPase serves as a receptor for both exogenous and endogenous cardiotonic glycosides and steroids, and a signal transducer for modifying myocardial metabolism as well as cellular survival and death. In addition, Na+-K+ ATPase is regulated by different hormones through the phosphorylation/dephosphorylation of phospholemman, which is tightly bound to this enzyme. The activity of Na+-K+ ATPase has been reported to be increased, unaltered and depressed in failing hearts depending upon the type and stage of heart failure as well as the association/disassociation of phospholemman and binding with endogenous cardiotonic steroids, namely endogenous ouabain and marinobufagenin. Increased Na+-K+ ATPase activity in association with a depressed level of intracellular Na+ in failing hearts is considered to decrease intracellular Ca2+ and serve as an adaptive mechanism for maintaining cardiac function. The slight to moderate depression of Na+-K+ ATPase by cardiac glycosides in association with an increased level of Na+ in cardiomyocytes is known to produce beneficial effects in failing hearts. On the other hand, markedly reduced Na+-K+ ATPase activity associated with an increased level of intracellular Na+ in failing hearts has been demonstrated to result in an intracellular Ca2+ overload, the occurrence of cardiac arrhythmias and depression in cardiac function during the development of heart failure. Furthermore, the status of Na+-K+ ATPase activity in heart failure is determined by changes in isoform subunits of the enzyme, the development of oxidative stress, intracellular Ca2+-overload, protease activation, the activity of inflammatory cytokines and sarcolemmal lipid composition. Evidence has been presented to show that marked alterations in myocardial cations cannot be explained exclusively on the basis of sarcolemma alterations, as other Ca2+ channels, cation transporters and exchangers may be involved in this event. A marked reduction in Na+-K+ ATPase activity due to a shift in its isoform subunits in association with intracellular Ca2+-overload, cardiac energy depletion, increased membrane permeability, Ca2+-handling abnormalities and damage to myocardial ultrastructure appear to be involved in the progression of heart failure.

Kinetic properties of gill (Na+, K+)-ATPase in the Pacific whiteleg shrimp Penaeus vannamei (Decapoda, Penaeidae)

The whiteleg marine shrimp Penaeus vannamei, originally from the Eastern Pacific Ocean, now inhabits tropical waters across Asia and Central and Southern America. This benthic species exhibits rapid growth, wide salinity and temperature tolerance, and disease resistance. These physiological traits have led to extensive research on its osmoregulatory mechanisms, including next-generation sequencing, transcriptomic analyses, and lipidomic responses. In crustaceans, osmotic and ionic homeostasis is primarily maintained by the membrane-bound metalloenzyme (Na+, K+)-ATPase. However, little is known about how various ligands modulate this enzyme in P. vannamei. Here, we examined the kinetic characteristics of the gill (Na+, K+)-ATPase to get biochemical insights into its modulation. A prominent immunoreactive band of ~120 kDa, corresponding to the (Na+, K+)-ATPase alpha-subunit, was identified. The enzyme exhibited two ATP hydrolyzing sites with K0.5 = 0.0003 ± 0.00002 and 0.05 ± 0.003 mmol L-1 and was stimulated by low sodium ion concentrations. Potassium and ammonium ions also stimulated enzyme activity with similar K0.5 values of 0.08 ± 0.004 and 0.06 ± 0.003 mmol L-1, respectively. Ouabain inhibition profile suggested a single enzyme isoform with a KI value of 2.10 ± 0.16 mmol L-1. Our findings showed significant kinetic differences in the (Na+, K+)-ATPase in Penaeus vannamei compared to marine and freshwater crustaceans. We expect our results to enhance understanding of the modulation of gill (Na+, K+)-ATPase in Penaeus vannamei and to provide a valuable tool for studying the shrimp's biochemical acclimation to varying salinity conditions.

A novel missense variant in the ATPase domain of ATP8A2 and review of phenotypic variability of ATP8A2-related disorders caused by missense changes

ATPase, class 1, type 8 A, member 2 (ATP8A2) is a P4-ATPase with a critical role in phospholipid translocation across the plasma membrane. Pathogenic variants in ATP8A2 are known to cause cerebellar ataxia, impaired intellectual development, and disequilibrium syndrome 4 (CAMRQ4) which is often associated with encephalopathy, global developmental delay, and severe motor deficits. Here, we present a family with two siblings born from a consanguineous, first-cousin union from Sudan presenting with global developmental delay, intellectual disability, spasticity, ataxia, nystagmus, and thin corpus callosum. Whole exome sequencing revealed a homozygous missense variant in the nucleotide binding domain of ATP8A2 (p.Leu538Pro) that results in near complete loss of protein expression. This is in line with other missense variants in the same domain leading to protein misfolding and loss of ATPase function. In addition, by performing diffusion-weighted imaging, we identified bilateral hyperintensities in the posterior limbs of the internal capsule suggesting possible microstructural changes in axon tracts that had not been appreciated before and could contribute to the sensorimotor deficits in these individuals.

Crossing the membrane-What does it take to flip a phospholipid? Structural and biochemical advances on P4-ATPase flippases

Membrane asymmetry is critical for maintenance of several different processes such as cell signaling, apoptosis, and vesicular transport in various eukaryotic systems. Flippases of the P4-ATPase family are associated with flipping phospholipids from the luminal or exoplasmic leaflet to the cytosolic leaflet. P4-ATPases belong to the P-type ATPase family, which are activated by phosphorylation and couple ATPase activity to substrate translocation. These proteins possess a transmembrane domain responsible for substrate transport, while the cytosolic machinery performs the necessary ATP hydrolysis for this process. Several high-resolution structures of human or yeast P4-ATPases have recently been resolved, but a comprehensive overview of the changes for reaction cycle in different members was crucial for future research. In this review, we have compiled available data reflecting the reaction cycle-associated changes in conformation of P4-ATPases. Together, this will provide an improved understanding of the similarities and differences between these members, which will drive further structural, functional, and computational studies to understand the mechanisms of these flippases.

Effect of Cations on ATP Binding to the N-domain of Na+, K+-ATPase

The nucleotide-binding domain (N-domain) of the Na+, K+-ATPase (NKA) is physicochemically characterized by a high content of Glu and Asp residues, resulting in a low isoelectric point (pI = 5.0). Acidic proteins are known to interact with cations. The analysis in silico revealed potential cation interaction sites in the NKA N-domain structure. The interaction with cations was tested in vitro by using a recombinant NKA N-domain. The N-domain contains two Trp residues at the protein surface, as determined by acrylamide-mediated fluorescence quenching, that are useful for structural studies through fluorescence changes. Intrinsic fluorescence of the N-domain was decreased by the presence of cations (Na+, K+, Ca2+) indicating an effect on the protein structure. ATP binding also decreased the N-domain intrinsic fluorescence, which allowed nucleotide affinity determination. In the presence of cations, the N-domain affinity for ATP was increased. Molecular docking of fluorescein isothiocyanate (FITC) with the N-domain showed two binding modes with the isothiocyanate group located 5-6 Å close to Lys485 and Lys506 in the nucleotide-binding site. The presence of ATP prevented the FITC covalent labeling of the N-domain demonstrating the competitive behavior for the binding site. It is proposed that cations interact with the N-domain structure and thereby modulate nucleotide (ATP) affinity and possibly affecting NKA catalysis.

Effects of superoxide radical on photosynthesis and K+ and redox homeostasis in quinoa and spinach

Methyl viologen (MV), also known as paraquat, is a widely used herbicide but has also been reported as highly toxic to different life forms. The mode of its operation is related to superoxide radical (O2.-) production and consequent oxidative damage. However, besides the damage to key macromolecules, reactive oxygen species (ROS; to which O2.- belongs) are also known as regulators of numerous ion transport systems located at cellular membranes. In this study, we used MV as a tool to probe the role of O2.- in regulating membrane-transport activity and systemic acquired tolerance in halophytic Chenopodium quinoa and glycophytic spinach plants. Both plant species showed growth reduction in terms of reduced shoot length, lower shoot fresh and dry weight, photosynthesis rate, and chlorophyll contents; however, quinoa showed less reduction in growth compared with spinach. This whole plant response was further examined by measuring the ion concentration, gene expression of ion transporters, activation of antioxidants, and osmolyte accumulation. We observed that at the mechanistic level, the differences in growth in response to MV were conferred by at least four complementary physiological mechanisms: (1) higher K+ loss from spinach leaves resulted from higher expression of MV-induced plasma membrane-based depolarization-activated K+ efflux GORK channel, (2) higher activation of high-affinity K+ uptake transporter HAK5 in quinoa, (3) higher antioxidant production and osmolyte accumulation in quinoa as compared with spinach, and (4) maintaining a higher rate of photosynthesis due to higher chlorophyll contents, and efficiency of photosystem II and reduced ROS and MDA contents. Obtained results also showed that MV induced O2.- significantly reduced N contents in both species but with more pronounced effects in glycophytic spinach. Taken together this study has shown the role of O2.- in regulating membrane ion transport and N metabolism in the leaves of halophyte vs. glycophyte in the context of oxidative stress tolerance.

Impacts of P4-ATPase Deletion on Membrane Asymmetry and Disease Development

Phospholipids exhibit an asymmetrical distribution on the cell membrane. P4-ATPases, type IV lipid flippases, are responsible for establishing and maintaining this phospholipid compositional asymmetry. The essential β subunit CDC50 (also known as TMEM30) assists in the transport and proper functioning of P4-ATPases. Deletion of P4-ATPases and its β subunit disrupts the membrane asymmetry, impacting the growth and development and leading to various diseases affecting the nervous, skeletal muscle, digestive, and hematopoietic systems. This review discusses the crucial roles of P4-ATPases and their β subunit in Saccharomyces cerevisiae, Arabidopsis thaliana, Caenorhabditis elegans, and mammals, offering valuable insights for future research.

Copper homeostasis and cuproptosis in radiation-induced injury

Radiation therapy for cancer treatment brings about a series of radiation injuries to normal tissues. In recent years, the discovery of copper-regulated cell death, cuproptosis, a novel form of programmed cell death, has attracted widespread attention and exploration in various biological functions and pathological mechanisms of copper metabolism and cuproptosis. Understanding its role in the process of radiation injury may open up new avenues and directions for exploration in radiation biology and radiation oncology, thereby improving tumor response and mitigating adverse reactions to radiotherapy. This review provides an overview of copper metabolism, the characteristics of cuproptosis, and their potential regulatory mechanisms in radiation injury.

The role of reactive oxygen species in regulation of the plasma membrane H+-ATPase activity in Masson pine (Pinus massoniana Lamb.) roots responding to acid stress

To understand the role of reactive oxygen species (ROS) in regulation of the plasma membrane (PM) H+-ATPase in acid-stressed Masson pine roots, different acidity (pH 6.6 as the control, pH 5.6 and pH 4.6) of simulated acid rain (SAR) added with and without external chemicals (H2O2, enzyme inhibitors and ROS scavenger) was prepared. After 30 days of SAR exposure, the plant morphological phenotype attributes, levels of cellular ROS and lipid peroxidation, enzymatic activities of antioxidants, PM nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and PM H+-ATPase activity in pine seedlings were measured. Compared with the control, the growth of pine seedlings exposed to SAR in the presence or absence of H2O2 was well-maintained, but the application of Na3VO4, 1,3-dimethyl-2-thiourea, N, N-dimethylthiourea (DMTU) and diphenyleneiodonium chloride (DPI) caused a substantial growth inhibition. In addition, SAR exposure, SAR with H2O2 treatment, and SAR with Na3VO4 treatment increased the cellular H2O2 content, O2- content and malondialdehyde (MDA) content, while the use of DMTU and DPI lead to relatively low levels. Similarly, the enzymatic activities of antioxidants, PM NADPH oxidase and PM H+-ATPase in acid stressed pine seedlings elevated with the increasing acidity. A significant stimulation of these enzymatic activities obtained from SAR with H2O2 treatment was observed, whereas which decreased obviously with the addition of Na3VO4, DMTU and DPI (P < 0.05). Moreover, a positive correlation was found between plant morphological attributes and the PM H+-ATPase activity (P < 0.05). Besides, the PM H+-ATPase activity positively correlated with the cellular ROS contents and the enzymatic activities of antioxidants and PM NADPH oxidase (P < 0.05). Therefore, the PM H+-ATPase is instrumental in the growth of pine seedlings resisting to acid stress by enhancing its activity. The process involves the signaling transduction of cellular ROS and coordination with PM NADPH oxidase.

Understanding the role of P-type ATPases in regulating pollen fertility and development in pigeonpea

The P-type ATPase superfamily genes are the cation and phospholipid pumps that transport ions across the membranes by hydrolyzing ATP. They are involved in a diverse range of functions, including fundamental cellular events that occur during the growth of plants, especially in the reproductive organs. The present work has been undertaken to understand and characterize the P-type ATPases in the pigeonpea genome and their potential role in anther development and pollen fertility. A total of 59 P-type ATPases were predicted in the pigeonpea genome. The phylogenetic analysis classified the ATPases into five subfamilies: eleven P1B, eighteen P2A/B, fourteen P3A, fifteen P4, and one P5. Twenty-three pairs of P-type ATPases were tandemly duplicated, resulting in their expansion in the pigeonpea genome during evolution. The orthologs of the reported anther development-related genes were searched in the pigeonpea genome, and the expression profiling studies of specific genes via qRT-PCR in the pre- and post-meiotic anther stages of AKCMS11A (male sterile), AKCMS11B (maintainer) and AKPR303 (fertility restorer) lines of pigeonpea was done. Compared to the restorer and maintainer lines, the down-regulation of CcP-typeATPase22 in the post-meiotic anthers of the male sterile line might have played a role in pollen sterility. Furthermore, the strong expression of CcP-typeATPase2 in the post-meiotic anthers of restorer line and CcP-typeATPase46, CcP-typeATPase51, and CcP-typeATPase52 in the maintainer lines, respectively, compared to the male sterile line, clearly indicates their potential role in developing male reproductive organs in pigeonpea.

Cuproptosis in cancers: Function and implications from bench to bedside

Copper, an indispensable micronutrient, is implicated in numerous vital biological processes and is essential for all physiological activities. Recently, the discovery of a novel type of copper-dependent cell death, known as cuproptosis, has shed light on its role in cancer development. Extensive research is currently underway to unravel the mechanisms underlying cuproptosis and its correlation with various cancer types. In this review, we summarize the findings regarding the roles and mechanisms of cuproptosis in various cancer types, including colorectal cancer, lung cancer, gastric cancer, breast cancer, liver cancer and cutaneous melanoma. Furthermore, the effects of copper-related agents such as copper chelators and copper ionophores on cell proliferation, apoptosis, angiogenesis, tumor immunity, and chemotherapy resistance have been explored in cancer preclinical and clinical trials. These insights provide promising avenues for the development of prospective anticancer drugs aimed at inducing cuproptosis.

Copper homeostasis and cuproptosis in gynecological disorders: Pathogenic insights and therapeutic implications

This review comprehensively explores the complex role of copper homeostasis in female reproductive system diseases. As an essential trace element, copper plays a crucial role in various biological functions. Its dysregulation is increasingly recognized as a pivotal factor in the pathogenesis of gynecological disorders. We investigate how copper impacts these diseases, focusing on aspects like oxidative stress, inflammatory responses, immune function, estrogen levels, and angiogenesis. The review highlights significant changes in copper levels in diseases such as cervical, ovarian, endometrial cancer, and endometriosis, underscoring their potential roles in disease mechanisms and therapeutic exploration. The recent discovery of 'cuproptosis,' a novel cell death mechanism induced by copper ions, offers a fresh molecular perspective in understanding these diseases. The review also examines genes associated with cuproptosis, particularly those related to drug resistance, suggesting new strategies to enhance traditional therapy effectiveness. Additionally, we critically evaluate current therapeutic approaches targeting copper homeostasis, including copper ionophores, chelators, and nanoparticles, emphasizing their emerging potential in gynecological disease treatment. This article aims to provide a comprehensive overview of copper's role in female reproductive health, setting the stage for future research to elucidate its mechanisms and develop targeted therapeutic strategies.

Identification of the potato (Solanum tuberosum L.) P-type ATPase gene family and investigating the role of PHA2 in response to Pep13

P-type ATPase family members play important roles in plant growth and development and are involved in plant resistance to various biotic and abiotic factors. Extensive studies have been conducted on the P-type ATPase gene families in Arabidopsis thaliana and rice but our understanding in potato remains relatively limited. Therefore, this study aimed to screen and analyze 48 P-type ATPase genes from the potato (Solanum tuberosum L.) genome database at the genome-wide level. Potato P-type ATPase genes were categorized into five subgroups based on the phylogenetic classification of the reported species. Additionally, several bioinformatic analyses, including gene structure analysis, chromosomal position analysis, and identification of conserved motifs and promoter cis-acting elements, were performed. Interestingly, the plasma membrane H+-ATPase (PM H+-ATPase) genes of one of the P3 subgroups showed differential expression in different tissues of potato. Specifically, PHA2, PHA3, and PHA7 were highly expressed in the roots, whereas PHA8 was expressed in potatoes only under stress. Furthermore, the small peptide Pep13 inhibited the expression of PHA1, PHA2, PHA3, and PHA7 in potato roots. Transgenic plants heterologously overexpressing PHA2 displayed a growth phenotype sensitive to Pep13 compared with wild-type plants. Further analysis revealed that reducing potato PM H+-ATPase enzyme activity enhanced resistance to Pep13, indicating the involvement of PM H+-ATPase in the physiological process of potato late blight and the enhancement of plant disease resistance. This study confirms the critical role of potato PHA2 in resistance to Pep13.

Small but powerful: RALF peptides in plant adaptive and developmental responses

Plants live in a highly dynamic environment and require to rapidly respond to a plethora of environmental stimuli, so that to maintain their optimal growth and development. A small plant peptide, rapid alkalization factor (RALF), can rapidly increase the pH value of the extracellular matrix in plant cells. RALFs always function with its corresponding receptors. Mechanistically, effective amount of RALF is induced and released at the critical period of plant growth and development or under different external environmental factors. Recent studies also highlighted the role of RALF peptides as important regulators in plant intercellular communications, as well as their operation in signal perception and as ligands for different receptor kinases on the surface of the plasma membrane, to integrate various environmental cues. In this context, understanding the fine-print of above processes may be essential to solve the problems of crop adaptation to various harsh environments under current climate trends scenarios, by genetic means. This paper summarizes the current knowledge about the structure and diversity of RALF peptides and their roles in plant development and response to stresses, highlighting unanswered questions and problems to be solved.

AlphaFold2-guided description of CoBaHMA, a novel family of bacterial domains within the heavy-metal-associated superfamily

Three-dimensional (3D) structure information, now available at the proteome scale, may facilitate the detection of remote evolutionary relationships in protein superfamilies. Here, we illustrate this with the identification of a novel family of protein domains related to the ferredoxin-like superfold, by combining (i) transitive sequence similarity searches, (ii) clustering approaches, and (iii) the use of AlphaFold2 3D structure models. Domains of this family were initially identified in relation with the intracellular biomineralization of calcium carbonates by Cyanobacteria. They are part of the large heavy-metal-associated (HMA) superfamily, departing from the latter by specific sequence and structural features. In particular, most of them share conserved basic amino acids  (hence their name CoBaHMA for Conserved Basic residues HMA), forming a positively charged surface, which is likely to interact with anionic partners. CoBaHMA domains are found in diverse modular organizations in bacteria, existing in the form of monodomain proteins or as part of larger proteins, some of which are membrane proteins involved in transport or lipid metabolism. This suggests that the CoBaHMA domains may exert a regulatory function, involving interactions with anionic lipids. This hypothesis might have a particular resonance in the context of the compartmentalization observed for cyanobacterial intracellular calcium carbonates.

Na+/K+-ATPase: More than an Electrogenic Pump

The sodium pump, or Na+/K+-ATPase (NKA), is an essential enzyme found in the plasma membrane of all animal cells. Its primary role is to transport sodium (Na+) and potassium (K+) ions across the cell membrane, using energy from ATP hydrolysis. This transport creates and maintains an electrochemical gradient, which is crucial for various cellular processes, including cell volume regulation, electrical excitability, and secondary active transport. Although the role of NKA as a pump was discovered and demonstrated several decades ago, it remains the subject of intense research. Current studies aim to delve deeper into several aspects of this molecular entity, such as describing its structure and mode of operation in atomic detail, understanding its molecular and functional diversity, and examining the consequences of its malfunction due to structural alterations. Additionally, researchers are investigating the effects of various substances that amplify or decrease its pumping activity. Beyond its role as a pump, growing evidence indicates that in various cell types, NKA also functions as a receptor for cardiac glycosides like ouabain. This receptor activity triggers the activation of various signaling pathways, producing significant morphological and physiological effects. In this report, we present the results of a comprehensive review of the most outstanding studies of the past five years. We highlight the progress made regarding this new concept of NKA and the various cardiac glycosides that influence it. Furthermore, we emphasize NKA's role in epithelial physiology, particularly its function as a receptor for cardiac glycosides that trigger intracellular signals regulating cell-cell contacts, proliferation, differentiation, and adhesion. We also analyze the role of NKA β-subunits as cell adhesion molecules in glia and epithelial cells.

Consensus, controversies, and conundrums of P4-ATPases: The emerging face of eukaryotic lipid flippases

The cryo-EM resolution revolution has heralded a new era in our understanding of eukaryotic lipid flippases with a rapidly growing number of high-resolution structures. Flippases belong to the P4 family of ATPases (type IV P-type ATPases) that largely follow the reaction cycle proposed for the more extensively studied cation-transporting P-type ATPases. However, unlike the canonical P-type ATPases, no flippase cargos are transported in the phosphorylation half-reaction. Instead of being released into the intracellular or extracellular milieu, lipid cargos are transported to their destination at the inner leaflet of the membrane. Recent flippase structures have revealed multiple conformational states during the lipid transport cycle. Nonetheless, critical conformational states capturing the lipid cargo "in transit" are still missing. In this review, we highlight the amazing structural advances of these lipid transporters, discuss various perspectives on catalytic and regulatory mechanisms in the literature, and shed light on future directions in further deciphering the detailed molecular mechanisms of lipid flipping.

Genome-wide identification of heavy-metal ATPases genes in Areca catechu: investigating their functionality under heavy metal exposure

Heavy-metal ATPases (HMAs) play a vital role in plants, helping to transport heavy metal ions across cell membranes.However, insufficient data exists concerning HMAs genes within the Arecaceae family.In this study, 12 AcHMA genes were identified within the genome of Areca catechu, grouped into two main clusters based on their phylogenetic relationships.Genomic distribution analysis reveals that the AcHMA genes were unevenly distributed across six chromosomes. We further analyzed their physicochemical properties, collinearity, and gene structure.Furthermore, RNA-seq data analysis exhibited varied expressions in different tissues of A. catechu and found that AcHMA1, AcHMA2, and AcHMA7 were highly expressed in roots, leaves, pericarp, and male/female flowers. A total of six AcHMA candidate genes were selected based on gene expression patterns, and their expression in the roots and leaves was determined using RT-qPCR under heavy metal stress. Results showed that the expression levels of AcHMA1 and AcHMA3 genes were significantly up-regulated under Cd2 + and Zn2 + stress. Similarly, in response to Cu2+, the AcHMA5 and AcHMA8 revealed the highest expression in roots and leaves, respectively. In conclusion, this study will offer a foundation for exploring the role of the HMAs gene family in dealing with heavy metal stress conditions in A. catechu.

An ATP13A1-assisted topogenesis pathway for folding multi-spanning membrane proteins

Many multi-spanning membrane proteins contain poorly hydrophobic transmembrane domains (pTMDs) protected from phospholipid in mature structure. Nascent pTMDs are difficult for translocon to recognize and insert. How pTMDs are discerned and packed into mature, muti-spanning configuration remains unclear. Here, we report that pTMD elicits a post-translational topogenesis pathway for its recognition and integration. Using six-spanning protein adenosine triphosphate-binding cassette transporter G2 (ABCG2) and cultured human cells as models, we show that ABCG2's pTMD2 can pass through translocon into the endoplasmic reticulum (ER) lumen, yielding an intermediate with inserted yet mis-oriented downstream TMDs. After translation, the intermediate recruits P5A-ATPase ATP13A1, which facilitates TMD re-orientation, allowing further folding and the integration of the remaining lumen-exposed pTMD2. Depleting ATP13A1 or disrupting pTMD-characteristic residues arrests intermediates with mis-oriented and exposed TMDs. Our results explain how a "difficult" pTMD is co-translationally skipped for insertion and post-translationally buried into the final correct structure at the late folding stage to avoid excessive lipid exposure.

A novel missense variant in the ATPase domain of ATP8A2 and review of phenotypic variability of ATP8A2-related disorders caused by missense changes

ATPase, class 1, type 8A, member 2 (ATP8A2) is a P4-ATPase with a critical role in phospholipid translocation across the plasma membrane. Pathogenic variants in ATP8A2 are known to cause cerebellar ataxia, mental retardation, and disequilibrium syndrome 4 (CAMRQ4) which is often associated with encephalopathy, global developmental delay, and severe motor deficits. Here, we present a family with two siblings presenting with global developmental delay, intellectual disability, spasticity, ataxia, nystagmus, and thin corpus callosum. Whole exome sequencing revealed a homozygous missense variant in the nucleotide binding domain of ATP8A2 (p.Leu538Pro) that results in near complete loss of protein expression. This is in line with other missense variants in the same domain leading to protein misfolding and loss of ATPase function. In addition, by performing diffusion-weighted imaging, we identified bilateral hyperintensities in the posterior limbs of the internal capsule suggesting possible microstructural changes in axon tracts that had not been appreciated before and could contribute to the sensorimotor deficits in these individuals.

Fungal Plasma Membrane H+-ATPase: Structure, Mechanism, and Drug Discovery

The fungal plasma membrane H+-ATPase (Pma1) pumps protons out of the cell to maintain the transmembrane electrochemical gradient and membrane potential. As an essential P-type ATPase uniquely found in fungi and plants, Pma1 is an attractive antifungal drug target. Two recent Cryo-EM studies on Pma1 have revealed its hexameric architecture, autoinhibitory and activation mechanisms, and proton transport mechanism. These structures provide new perspectives for the development of antifungal drugs targeting Pma1. In this article, we review the history of Pma1 structure determination, the latest structural insights into Pma1, and drug discoveries targeting Pma1.

ERMA (TMEM94) is a P-type ATPase transporter for Mg2+ uptake in the endoplasmic reticulum

Intracellular Mg2+ (iMg2+) is bound with phosphometabolites, nucleic acids, and proteins in eukaryotes. Little is known about the intracellular compartmentalization and molecular details of Mg2+ transport into/from cellular organelles such as the endoplasmic reticulum (ER). We found that the ER is a major iMg2+ compartment refilled by a largely uncharacterized ER-localized protein, TMEM94. Conventional and AlphaFold2 predictions suggest that ERMA (TMEM94) is a multi-pass transmembrane protein with large cytosolic headpiece actuator, nucleotide, and phosphorylation domains, analogous to P-type ATPases. However, ERMA uniquely combines a P-type ATPase domain and a GMN motif for ERMg2+ uptake. Experiments reveal that a tyrosine residue is crucial for Mg2+ binding and activity in a mechanism conserved in both prokaryotic (mgtB and mgtA) and eukaryotic Mg2+ ATPases. Cardiac dysfunction by haploinsufficiency, abnormal Ca2+ cycling in mouse Erma+/- cardiomyocytes, and ERMA mRNA silencing in human iPSC-cardiomyocytes collectively define ERMA as an essential component of ERMg2+ uptake in eukaryotes.

P-type ATPase zinc transporter Rv3270 of Mycobacterium tuberculosis enhances multi-drug efflux activity

Metal homeostasis is maintained by the uptake, storage and efflux of metal ions that are necessary for the survival of the bacterium. Homeostasis is mostly regulated by a group of transporters categorized as ABC transporters and P-type ATPases. On the other hand, efflux pumps often play a role in drug-metal cross-resistance. Here, with the help of antibiotic sensitivity, antibiotic/dye accumulation and semi-quantitative biofilm formation assessments we report the ability of Rv3270, a P-type ATPase known for its role in combating Mn2+ and Zn2+ metal ion toxicity in Mycobacterium tuberculosis, in influencing the extrusion of multiple structurally unrelated drugs and enhancing the biofilm formation of Escherichia coli and Mycobacterium smegmatis. Overexpression of Rv3270 increased the tolerance of host cells to norfloxacin, ofloxacin, sparfloxacin, ampicillin, oxacillin, amikacin and isoniazid. A significantly lower accumulation of norfloxacin, ethidium bromide, bocillin FL and levofloxacin in cells harbouring Rv3270 as compared to host cells indicated its role in enhancing efflux activity. Although over-expression of Rv3270 did not alter the susceptibility levels of levofloxacin, rifampicin and apramycin, the presence of a sub-inhibitory concentration of Zn2+ resulted in low-level tolerance towards these drugs. Of note, the expression of Rv3270 enhanced the biofilm-forming ability of the host cells strengthening its role in antimicrobial resistance. Therefore, the study indicated that the over-expression of Rv3270 enhances the drug efflux activity of the micro-organism where zinc might facilitate drug-metal cross-resistance for some antibiotics.