The N- or C-terminal cytoplasmic regions of P4-ATPases determine their cellular localization

Mammalian P4-ATPases specifically localize to the plasma membrane and the membranes of intracellular compartments. P4-ATPases contain 10 transmembrane domains, and their N- and C-terminal (NT and CT) regions face the cytoplasm. Among the ATP10 and ATP11 proteins of P4-ATPases, ATP10A, ATP10D, ATP11A, and ATP11C localize to the plasma membrane, while ATP10B and ATP11B localize to late endosomes and early/recycling endosomes, respectively. We previously showed that the NT region of ATP9B is critical for its localization to the Golgi apparatus, while the CT regions of ATP11C isoforms are critical for Ca²⁺-dependent endocytosis or polarized localization at the plasma membrane. Here, we conducted a comprehensive analysis of chimeric proteins and found that the NT region of ATP10 proteins and the CT region of ATP11 proteins are responsible for their specific subcellular localization. Importantly, the ATP10B NT and the ATP11B CT regions were found to harbor a trafficking and/or targeting signal that allows these P4-ATPases to localize to late endosomes and early/recycling endosomes, respectively. Moreover, dileucine residues in the NT region of ATP10B were required for its trafficking to endosomal compartments. These results suggest that the NT and CT sequences of P4-ATPases play a key role in their intracellular trafficking.

Draft whole genome sequence for four highly copper resistant soil isolates Pseudomonas lactis strain UKR1, Pseudomonas panacis strain UKR2, and Pseudomonas veronii strains UKR3 and UKR4

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Four bacterial strains with record resistance to Cu(II) have been isolated.

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Genomic sequences are available for genome mining and studying the genetic determinants of bacterial resistance to Cu(II).

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Genomic sequences provide the foundation necessary for transcriptional and functional studies of genes encoding for Cu(II) resistance mechanisms in Pseudomonas spp.

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The data will be of interest for a broad community of biotechnologists and microbiologists and will aid in developing novel technologies for copper detoxification in contaminated soils and industrial wastewaters.

Environmental copper pollution causes major destruction to ecological systems, which require the development of environmentally friendly biotechnological, in particular, microbial methods for copper removal. These methods rely on the availability of microorganisms resistant to high levels of copper. Here we isolated four bacterial strains with record resistance to up to 1.0 M Cu(II). The strains were isolated from ecologically diverse soil samples, and their genomes were sequenced. A 16S rRNA sequence-based phylogenetic analysis identified that all four isolates belong to the genus Pseudomonas. Particularly, strains UKR1 and UKR2 isolated from Kyiv region in Ukraine were identified as P. lactis and P. panacis, respectively, and strains UKR3 and UKR4 isolated from Svalbard Island in the Arctic Ocean and Galindez Island in Antarctica, respectively, were identified as P. veronii. Initial in-silico screening for genes encoding copper resistance mechanisms showed that all four strains encode copper resistance proteins CopA, CopB, CopD, CopA3, CopZ, as well as two-component regulatory system CusRS, all known to be associated with metal resistance in Pseudomonas genus. Further detailed studies will aim to characterize the full genomic potential of the isolates to enable their application for copper bioremediation in contaminated soils and industrial wastewaters.

Mutated ATP10B increases Parkinson's disease risk by compromising lysosomal glucosylceramide export

Parkinson’s disease (PD) is a progressive neurodegenerative brain disease presenting with a variety of motor and non-motor symptoms, loss of midbrain dopaminergic neurons in the substantia nigra pars compacta and the occurrence of α-synuclein-positive Lewy bodies in surviving neurons. Here, we performed whole exome sequencing in 52 early-onset PD patients and identified 3 carriers of compound heterozygous mutations in the ATP10B P4-type ATPase gene. Genetic screening of a Belgian PD and dementia with Lewy bodies (DLB) cohort identified 4 additional compound heterozygous mutation carriers (6/617 PD patients, 0.97%; 1/226 DLB patients, 0.44%). We established that ATP10B encodes a late endo-lysosomal lipid flippase that translocates the lipids glucosylceramide (GluCer) and phosphatidylcholine (PC) towards the cytosolic membrane leaflet. The PD associated ATP10B mutants are catalytically inactive and fail to provide cellular protection against the environmental PD risk factors rotenone and manganese. In isolated cortical neurons, loss of ATP10B leads to general lysosomal dysfunction and cell death. Impaired lysosomal functionality and integrity is well known to be implicated in PD pathology and linked to multiple causal PD genes and genetic risk factors. Our results indicate that recessive loss of function mutations in ATP10B increase risk for PD by disturbed lysosomal export of GluCer and PC. Both ATP10B and glucocerebrosidase 1, encoded by the PD risk gene GBA1, reduce lysosomal GluCer levels, emerging lysosomal GluCer accumulation as a potential PD driver.

The KdpFABC complex - K+ transport against all odds

In bacteria, K⁺ is used to maintain cell volume and osmotic potential. Homeostasis normally involves a network of constitutively expressed transport systems, but in K⁺ deficient environments, the KdpFABC complex uses ATP to pump K⁺ into the cell. This complex appears to be a hybrid of two types of transporters, with KdpA descending from the superfamily of K⁺ transporters and KdpB belonging to the superfamily of P-type ATPases. Studies of enzymatic activity documented a catalytic cycle with hallmarks of classical P-type ATPases and studies of ion transport indicated that K⁺ import into the cytosol occurred in the second half of this cycle in conjunction with hydrolysis of an aspartyl phosphate intermediate. Atomic structures of the KdpFABC complex from X-ray crystallography and cryo-EM have recently revealed conformations before and after formation of this aspartyl phosphate that appear to contradict the functional studies. Specifically, structural comparisons with the archetypal P-type ATPase, SERCA, suggest that K⁺ transport occurs in the first half of the cycle, accompanying formation of the aspartyl phosphate. Further controversy has arisen regarding the path by which K⁺ crosses the membrane. The X-ray structure supports the conventional view that KdpA provides the conduit, whereas cryo-EM structures suggest that K⁺ moves from KdpA through a long, intramembrane tunnel to reach canonical ion binding sites in KdpB from which they are released to the cytosol. This review discusses evidence supporting these contradictory models and identifies key experiments needed to resolve discrepancies and produce a unified model for this fascinating mechanistic hybrid.

Biochemical Characterization and Allosteric Modulation by Magnesium of (Na+, K+)-ATPase Activity in the Gills of the Red Mangrove Crab Goniopsis cruentata (Brachyura, Grapsidae)

We provide a kinetic characterization of (Na⁺, K⁺)-ATPase activity in a posterior gill microsomal fraction from the grapsid crab Goniopsis cruentata. (Na⁺, K⁺)-ATPase activity constitutes 95% of total ATPase activity, and sucrose density centrifugation reveals an ATPase activity peak between 25 and 35% sucrose, distributed into two, partially separated protein fractions. The (Na⁺, K⁺)-ATPase α-subunit is localized throughout the ionocyte cytoplasm and has an M_r of ≈ 10 kDa and hydrolyzes ATP obeying cooperative kinetics. Low (V_M = 186.0 ± 9.3 nmol Pi min^-1 mg^-1 protein and K_0.5 = 0.085 ± 0.004 mmol L^-1) and high (V_M = 153.4 ± 7.7 nmol Pi min^-1 mg^-1 protein and K_0.5 = 0.013 ± 0.0006 mmol L^-1) affinity ATP binding sites were characterized. At low ATP concentrations, excess Mg²⁺ stimulates the enzyme, triggering exposure of a high-affinity binding site that accounts for 50% of (Na⁺, K⁺)-ATPase activity. Stimulation by Mg²⁺ (V_M = 425.9 ± 25.5 nmol Pi min^-1 mg^-1 protein, K_0.5 = 0.16 ± 0.01 mmol L^-1), K⁺ (V_M = 485.3 ± 24.3 nmol Pi min^-1 mg^-1 protein, K_0.5 = 0.9 ± 0.05 mmol L^-1), Na⁺ (V_M = 425.0 ± 23.4 nmol Pi min^-1 mg^-1 protein, K_0.5 = 5.1 ± 0.3 mmol L^-1) and NH₄⁺ (V_M = 497.9 ± 24.9 nmol Pi min^-1 mg^-1 protein, K_0.5 = 9.7 ± 0.5 mmol L^-1) obeys cooperative kinetics. Ouabain inhibits up to 95% of ATPase activity with K_I = 196.6 ± 9.8 µmol L^-1. This first kinetic characterization of the gill (Na⁺, K⁺)-ATPase in Goniopsis cruentata enables better comprehension of the biochemical underpinnings of osmoregulatory ability in this semi-terrestrial mangrove crab.

The CzcCBA Efflux System Requires the CadA P-Type ATPase for Timely Expression Upon Zinc Excess in Pseudomonas aeruginosa

Zinc (Zn) is a trace element essential for life but can be toxic if present in excess. While cells have import systems to guarantee a vital Zn intracellular concentration, they also rely on export systems to avoid lethal Zn overload. In particular, the opportunistic pathogen Pseudomonas aeruginosa possesses four Zn export systems: CadA, CzcCBA, CzcD, and YiiP. In this work, we compare the importance for bacterial survival of each export system at high Zn concentrations. We show that the P-type ATPase CadA, and the efflux pump CzcCBA are the main efflux systems affecting the bacterium tolerance to Zn. In addition, cadA and czcCBA genes expression kinetics revealed a hierarchical organization and interdependence. In the presence of high Zn concentrations, cadA expression is very rapidly induced (<1 min), while czcCBA expression occurs subsequently (>15 min). Our present data show that the fast responsiveness of cadA to Zn excess is due to its transcriptional activator, CadR, which is constitutively present on its promoter and promptly activating cadA gene expression upon Zn binding. Moreover, we showed that CadA is essential for a timely induction of the CzcCBA efflux system. Finally, we observed an induction of cadA and czcCBA efflux systems upon phagocytosis of P. aeruginosa by macrophages, in which a toxic metal boost is discharged into the phagolysosome to intoxicate microbes. Importantly, we demonstrated that the regulatory link between induction of the CzcCBA system and the repression of the OprD porin responsible for carbapenem antibiotic resistance, is maintained in the macrophage environment.

Genetic perspective on the synergistic connection between vesicular transport, lysosomal and mitochondrial pathways associated with Parkinson's disease pathogenesis

Parkinson's disease (PD) and atypical parkinsonian syndromes (APS) are symptomatically characterized by parkinsonism, with the latter presenting additionally a distinctive range of atypical features. Although the majority of patients with PD and APS appear to be sporadic, genetic causes of several rare monogenic disease variants were identified. The knowledge acquired from these genetic factors indicated that defects in vesicular transport pathways, endo-lysosomal dysfunction, impaired autophagy-lysosomal protein and organelle degradation pathways, α-synuclein aggregation and mitochondrial dysfunction play key roles in PD pathogenesis. Moreover, membrane dynamics are increasingly recognized as a key player in the disease pathogenesis due lipid homeostasis alterations, associated with lysosomal dysfunction, caused by mutations in several PD and APS genes. The importance of lysosomal dysfunction and lipid homeostasis is strengthened by both genetic discoveries and clinical epidemiology of the association between parkinsonism and lysosomal storage disorders (LSDs), caused by the disruption of lysosomal biogenesis or function. A synergistic coordination between vesicular trafficking, lysosomal and mitochondria defects exist whereby mutations in PD and APS genes encoding proteins primarily involved one PD pathway are frequently associated with defects in other PD pathways as a secondary effect. Moreover, accumulating clinical and genetic observations suggest more complex inheritance patters of familial PD exist, including oligogenic and polygenic inheritance of genes in the same or interconnected PD pathways, further strengthening their synergistic connection.Here, we provide a comprehensive overview of PD and APS genes with functions in vesicular transport, lysosomal and mitochondrial pathways, and highlight functional and genetic evidence of the synergistic connection between these PD associated pathways.

Reduction of the P5A-ATPase Spf1p phosphoenzyme by a Ca2+-dependent phosphatase

P5 ATPases are eukaryotic pumps important for cellular metal ion, lipid and protein homeostasis; however, their transported substrate, if any, remains to be identified. Ca²⁺ was proposed to act as a ligand of P5 ATPases because it decreases the level of phosphoenzyme of the Spf1p P5A ATPase from Saccharomyces cerevisiae. Repeating previous purification protocols, we obtained a purified preparation of Spf1p that was close to homogeneity and exhibited ATP hydrolytic activity that was stimulated by the addition of CaCl₂. Strikingly, a preparation of a catalytically dead mutant Spf1p (D⁴⁸⁷N) also exhibited Ca²⁺-dependent ATP hydrolytic activity. These results indicated that the Spf1p preparation contained a co-purifying protein capable of hydrolyzing ATP at a high rate. The activity was likely due to a phosphatase, since the protein i) was highly active when pNPP was used as substrate, ii) required Ca²⁺ or Zn²⁺ for activity, and iii) was strongly inhibited by molybdate, beryllium and other phosphatase substrates. Mass spectrometry identified the phosphatase Pho8p as a contaminant of the Spf1p preparation. Modification of the purification procedure led to a contaminant-free Spf1p preparation that was neither stimulated by Ca²⁺ nor inhibited by EGTA or molybdate. The phosphoenzyme levels of a contaminant-free Spf1p preparation were not affected by Ca²⁺. These results indicate that the reported effects of Ca²⁺ on Spf1p do not reflect the intrinsic properties of Spf1p but are mediated by the activity of the accompanying phosphatase.

Structural and functional characterizations of the C-terminal domains of CzcD proteins

Zinc is a potent antimicrobial component of the innate immune response at the host-pathogen interface. Bacteria subvert or resist host zinc insults by metal efflux pathways that include cation diffusion facilitator (CDF) proteins. The structural and functional examination of this protein class has been limited, with only the structures of the zinc transporter YiiP proteins from E. coli and Shewanella oneidensis described to date. Here, we determine the metal binding properties, solution quaternary structures and three dimensional architectures of the C-terminal domains of the metal transporter CzcD proteins from Cupriavidus metallidurans, Pseudomonas aeruginosa and Thermotoga maritima. We reveal significant diversity in the metal-binding properties and structures of these proteins and discover a potential novel mechanism for metal-promoted dimerization for the Cupriavidus metallidurans and Pseudomonas aeruginosa proteins.

Comparison of lipidic carrier systems for integral membrane proteins - MsbA as case study

Membrane protein research suffers from the drawback that detergents, which are commonly used to solubilize integral membrane proteins (IMPs), often lead to protein instability and reduced activity. Recently, lipid nanodiscs (NDs) and saposin-lipoprotein particles (Salipro) have emerged as alternative carrier systems that keep membrane proteins in a native-like lipidic solution environment and are suitable for biophysical and structural studies. Here, we systematically compare nanodiscs and Salipros with respect to long-term stability as well as activity and stability of the incorporated membrane protein using the ABC transporter MsbA as model system. Our results show that both systems are suitable for activity measurements as well as structural studies in solution. Based on our results we suggest screening of different lipids with respect to activity and stability of the incorporated IMP before performing structural studies.

Genome-Wide Identification and Analysis of P-Type Plasma Membrane H+-ATPase Sub-Gene Family in Sunflower and the Role of HHA4 and HHA11 in the Development of Salt Stress Resistance

The P-type plasma membrane (PM) H⁺-ATPase plays a major role during the growth and development of a plant. It is also involved in plant resistance to a variety of biotic and abiotic factors, including salt stress. The PM H⁺-ATPase gene family has been well characterized in Arabidopsis and other crop plants such as rice, cucumber, and potato; however, the same cannot be said in sunflower (Helianthus annuus). In this study, a total of thirteen PM H⁺-ATPase genes were screened from the recently released sunflower genome database with a comprehensive genome-wide analysis. According to a systematic phylogenetic classification with a previously reported species, the sunflower PM H⁺-ATPase genes (HHAs) were divided into four sub-clusters (I, II, IV, and V). In addition, systematic bioinformatics analyses such as gene structure analysis, chromosome location analysis, subcellular localization predication, conserved motifs, and Cis-acting elements of promoter identification were also done. Semi-quantitative PCR analysis data of HHAs in different sunflower tissues revealed the specificity of gene spatiotemporal expression and sub-cluster grouping. Those belonging to sub-cluster I and II exhibited wide expression in almost all of the tissues studied while sub-cluster IV and V seldom showed expression. In addition, the expression of HHA4, HHA11, and HHA13 was shown to be induced by salt stress. The transgenic plants overexpressing HHA4 and HHA11 showed higher salinity tolerance compared with wild-type plants. Further analysis showed that the Na⁺ content of transgenic Arabidopsis plants decreased under salt stress, which indicates that PM H⁺ ATPase participates in the physiological process of Na⁺ efflux, resulting in salt resistance of the plants. This study is the first to identify and analyze the sunflower PM H⁺ ATPase gene family. It does not only lay foundation for future research but also demonstrates the role played by HHAs in salt stress tolerance.

Genome-Wide Identification and Characterization of Apple P3A-Type ATPase Genes, with Implications for Alkaline Stress Responses

The P3A-type ATPases play crucial roles in various physiological processes via the generation of a transmembrane H+ gradient (∆pH). However, the P3A-type ATPase superfamily in apple remains relatively uncharacterized. In this study, 15 apple P3A-type ATPase genes were identified based on the new GDDH13 draft genome sequence. The exon-intron organization of these genes, the physical and chemical properties, and conserved motifs of the encoded enzymes were investigated. Analyses of the chromosome localization and ω values of the apple P3A-type ATPase genes revealed the duplicated genes were influenced by purifying selection pressure. Six clades and frequent old duplication events were detected. Moreover, the significance of differences in the evolutionary rates of the P3A-type ATPase genes were revealed. An expression analysis indicated that all of the P3A-type ATPase genes were specifically expressed in more than one tissue. The expression of one P3A-type ATPase gene (MD15G1108400) was significantly upregulated in response to alkaline stress. Furthermore, a subcellular localization assay indicated that MD15G1108400 is targeted to the plasma membrane. These results imply that MD15G1108400 may be involved in responses to alkaline stress. Our data provide insights into the molecular characteristics and evolutionary patterns of the apple P3A-type ATPase gene family and provide a theoretical foundation for future in-depth functional characterizations of P3A-type ATPase genes under alkaline conditions.

Evolution of P2A and P5A ATPases: ancient gene duplications and the red algal connection to green plants revisited

In a search for slowly evolving nuclear genes that may cast light on the deep evolution of plants, we carried out phylogenetic analyses of two well-characterized subfamilies of P-type pumps (P2A and P5A ATPases) from representative branches of the eukaryotic tree of life. Both P-type ATPase genes were duplicated very early in eukaryotic evolution and before the divergence of the present eukaryotic supergroups. Synapomorphies identified in the sequences provide evidence that green plants and red algae are more distantly related than are green plants and eukaryotic supergroups in which secondary or tertiary plastids are common, such as several groups belonging to the clade that includes Stramenopiles, Alveolata, Rhizaria, Cryptophyta and Haptophyta (SAR). We propose that red algae branched off soon after the first photosynthesizing eukaryote had acquired a primary plastid, while in another lineage that led to SAR, the primary plastid was lost but, in some cases, regained as a secondary or tertiary plastid.

The role of P-type IIA and P-type IIB Ca2+-ATPases in plant development and growth

As sessile organisms, plants have evolved mechanisms to adapt to variable and rapidly fluctuating environmental conditions. Calcium (Ca2+) in plant cells is a versatile intracellular second messenger that is essential for stimulating short- and long-term responses to environmental stresses through changes in its concentration in the cytosol ([Ca2+]cyt). Increases in [Ca2+]cyt direct the strength and length of these stimuli. In order to terminate them, the cells must then remove the cytosolic Ca2+ against a concentration gradient, either taking it away from the cell or storing it in organelles such as the endoplasmic reticulum (ER) and/or vacuoles. Here, we review current knowledge about the biological roles of plant P-type Ca2+-ATPases as potential actors in the regulation of this cytosolic Ca2+ efflux, with a focus the IIA ER-type Ca2+-ATPases (ECAs) and the IIB autoinhibited Ca2+-ATPases (ACAs). While ECAs are analogous proteins to animal sarcoplasmic-endoplasmic reticulum Ca2+-ATPases (SERCAs), ACAs are equivalent to animal plasma membrane-type ATPases (PMCAs). We examine their expression patterns in cells exhibiting polar growth and consider their appearance during the evolution of the plant lineage. Full details of the functions and coordination of ECAs and ACAs during plant growth and development have not yet been elucidated. Our current understanding of the regulation of fluctuations in Ca2+ gradients in the cytoplasm and organelles during growth is in its infancy, but recent technological advances in Ca2+ imaging are expected to shed light on this subject.

Comparative analysis of the P-type ATPase gene family in seven Rosaceae species and an expression analysis in pear (Pyrus bretschneideri Rehd.)

P-type ATPases are integral membrane transporters that play important roles in transmembrane transport in plants. However, a comprehensive analysis of the P-type ATPase gene family has not been conducted in Chinese white pear (Pyrus bretschneideri) or other Rosaceae species. Here, we identified 419 P-type ATPase genes from seven Rosaceae species (Pyrus bretschneideri, Malus domestica, Prunus persica, Fragaria vesca, Prunus mume, Pyrus communis and Pyrus betulifolia). Structural and phylogenetic analyses revealed that P-type ATPase genes can be divided into five subfamilies. Different subfamilies have different conserved motifs and cis-acting elements, which may lead to functional divergence within one gene family. Dispersed duplication and whole-genome duplication may play critical roles in the expansion of the P-type ATPase family. Purifying selection was the primary force driving the evolution of P-type ATPase family genes. Based on the dynamic transcriptome analysis and transient transformation of Chinese white pear fruit, Pbr029767.1 in the P_3A subfamily were found to be associated with malate accumulation during pear fruit development. Using a co-expression network, we identified several transcription factors that may have regulatory relationships with the P-type ATPase gene family. Overall, this study lays a solid foundation for understanding the evolution and functions of P-type ATPase genes in Chinese white pear and six other Rosaceae species.

CtpB is a plasma membrane copper (I) transporting P-type ATPase of Mycobacterium tuberculosis

BACKGROUND

The intracellular concentration of heavy-metal cations, such as copper, nickel, and zinc is pivotal for the mycobacterial response to the hostile environment inside macrophages. To date, copper transport mediated by P-type ATPases across the mycobacterial plasma membrane has not been sufficiently explored.

RESULTS

In this work, the ATPase activity of the putative Mycobacterium tuberculosis P1B-type ATPase CtpB was associated with copper (I) transport from mycobacterial cells. Although CtpB heterologously expressed in M. smegmatis induced tolerance to toxic concentrations of Cu2+ and a metal preference for Cu+, the disruption of ctpB in M. tuberculosis cells did not promote impaired cell growth or heavy-metal accumulation in whole mutant cells in cultures under high doses of copper. In addition, the Cu+ ATPase activity of CtpB embedded in the plasma membrane showed features of high affinity/slow turnover ATPases, with enzymatic parameters KM 0.19 ± 0.04 µM and Vmax 2.29 ± 0.10 nmol/mg min. In contrast, the ctpB gene transcription was activated in cells under culture conditions that mimicked the hostile intraphagosomal environment, such as hypoxia, nitrosative and oxidative stress, but not under high doses of copper.

CONCLUSIONS

The overall results suggest that M. tuberculosis CtpB is associated with Cu+ transport from mycobacterial cells possibly playing a role different from copper detoxification.

Primary Active Ca2+ Transport Systems in Health and Disease

Calcium ions (Ca²⁺) are prominent cell signaling effectors that regulate a wide variety of cellular processes. Among the different players in Ca²⁺ homeostasis, primary active Ca²⁺ transporters are responsible for keeping low basal Ca²⁺ levels in the cytosol while establishing steep Ca²⁺ gradients across intracellular membranes or the plasma membrane. This review summarizes our current knowledge on the three types of primary active Ca²⁺-ATPases: the sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) pumps, the secretory pathway Ca²⁺- ATPase (SPCA) isoforms, and the plasma membrane Ca²⁺-ATPase (PMCA) Ca²⁺-transporters. We first discuss the Ca²⁺ transport mechanism of SERCA1a, which serves as a reference to describe the Ca²⁺ transport of other Ca²⁺ pumps. We further highlight the common and unique features of each isoform and review their structure-function relationship, expression pattern, regulatory mechanisms, and specific physiological roles. Finally, we discuss the increasing genetic and in vivo evidence that links the dysfunction of specific Ca²⁺-ATPase isoforms to a broad range of human pathologies, and highlight emerging therapeutic strategies that target Ca²⁺ pumps.

The small fiber neuropathy NaV1.7 I228M mutation: impaired neurite integrity via bioenergetic and mitotoxic mechanisms, and protection by dexpramipexole

Gain-of-function variants in voltage-gated sodium channel NaV1.7 that increase firing frequency and spontaneous firing of dorsal root ganglion (DRG) neurons have recently been identified in 5–10% of patients with idiopathic small fiber neuropathy (I-SFN). Our previous in vitro observations suggest that enhanced sodium channel activity can contribute to a decrease in length of peripheral sensory axons. We have hypothesized that sustained sodium influx due to the expression of SFN-associated sodium channel variants may trigger an energetic deficit in neurons that contributes to degeneration and loss of nerve fibers in SFN. Using an ATP FRET biosensor, we now demonstrate reduced steady-state levels of ATP and markedly faster ATP decay in response to membrane depolarization in cultured DRG neurons expressing an SFN-associated variant NaV1.7, I228M, compared with wild-type neurons. We also observed that I228M neurons show a significant reduction in mitochondrial density and size, indicating dysfunctional mitochondria and a reduced bioenergetic capacity. Finally, we report that exposure to dexpramipexole, a drug that improves mitochondrial energy metabolism, increases the neurite length of I228M-expressing neurons. Our data suggest that expression of gain-of-function variants of NaV1.7 can damage mitochondria and compromise cellular capacity for ATP production. The resulting bioenergetic crisis can consequently contribute to loss of axons in SFN. We suggest that, in addition to interventions that reduce ionic disturbance caused by mutant NaV1.7 channels, an alternative therapeutic strategy might target the bioenergetic burden and mitochondrial damage that occur in SFN associated with NaV1.7 gain-of-function mutations.

NEW & NOTEWORTHY Sodium channel NaV1.7 mutations that increase dorsal root ganglion (DRG) neuron excitability have been identified in small fiber neuropathy (SFN). We demonstrate reduced steady-state ATP levels, faster depolarization-evoked ATP decay, and reduced mitochondrial density and size in cultured DRG neurons expressing SFN-associated variant NaV1.7 I228M. Dexpramipexole, which improves mitochondrial energy metabolism, has a protective effect. Because gain-of-function NaV1.7 variants can compromise bioenergetics, therapeutic strategies that target bioenergetic burden and mitochondrial damage merit study in SFN.

ATP13A2 deficiency disrupts lysosomal polyamine export

ATP13A2 (PARK9) is a late endolysosomal transporter that is genetically implicated in a spectrum of neurodegenerative disorders, including Kufor-Rakeb syndrome-a parkinsonism with dementia¹-and early-onset Parkinson's disease². ATP13A2 offers protection against genetic and environmental risk factors of Parkinson's disease, whereas loss of ATP13A2 compromises lysosomes³. However, the transport function of ATP13A2 in lysosomes remains unclear. Here we establish ATP13A2 as a lysosomal polyamine exporter that shows the highest affinity for spermine among the polyamines examined. Polyamines stimulate the activity of purified ATP13A2, whereas ATP13A2 mutants that are implicated in disease are functionally impaired to a degree that correlates with the disease phenotype. ATP13A2 promotes the cellular uptake of polyamines by endocytosis and transports them into the cytosol, highlighting a role for endolysosomes in the uptake of polyamines into cells. At high concentrations polyamines induce cell toxicity, which is exacerbated by ATP13A2 loss due to lysosomal dysfunction, lysosomal rupture and cathepsin B activation. This phenotype is recapitulated in neurons and nematodes with impaired expression of ATP13A2 or its orthologues. We present defective lysosomal polyamine export as a mechanism for lysosome-dependent cell death that may be implicated in neurodegeneration, and shed light on the molecular identity of the mammalian polyamine transport system.

Myosin and Other Energy-Transducing ATPases: Structural Dynamics Studied by Electron Paramagnetic Resonance

The objective of this article was to document the energy-transducing and regulatory interactions in supramolecular complexes such as motor, pump, and clock ATPases. The dynamics and structural features were characterized by motion and distance measurements using spin-labeling electron paramagnetic resonance (EPR) spectroscopy. In particular, we focused on myosin ATPase with actin-troponin-tropomyosin, neural kinesin ATPase with microtubule, P-type ion-motive ATPase, and cyanobacterial clock ATPase. Finally, we have described the relationships or common principles among the molecular mechanisms of various energy-transducing systems and how the large-scale thermal structural transition of flexible elements from one state to the other precedes the subsequent irreversible chemical reactions.

Cancer-Related Increases and Decreases in Calcium Signaling at the Endoplasmic Reticulum-Mitochondria Interface (MAMs)

Endoplasmic reticulum (ER)-mitochondria regions are specialized subdomains called also mitochondria-associated membranes (MAMs). MAMs allow regulation of lipid synthesis and represent hubs for ion and metabolite signaling. As these two organelles can module both the amplitude and the spatiotemporal patterns of calcium (Ca²⁺) signals, this particular interaction controls several Ca²⁺-dependent pathways well known for their contribution to tumorigenesis, such as metabolism, survival, sensitivity to cell death, and metastasis. Mitochondria-mediated apoptosis arises from mitochondrial Ca²⁺ overload, permeabilization of the mitochondrial outer membrane, and the release of mitochondrial apoptotic factors into the cytosol. Decreases in Ca²⁺ signaling at the ER-mitochondria interface are being studied in depth as failure of apoptotic-dependent cell death is one of the predominant characteristics of cancer cells. However, some recent papers that linked MAMs Ca²⁺ crosstalk-related upregulation to tumor onset and progression have aroused the interest of the scientific community.In this review, we will describe how different MAMs-localized proteins modulate the effectiveness of Ca²⁺-dependent apoptotic stimuli by causing both increases and decreases in the ER-mitochondria interplay and, specifically, by modulating Ca²⁺ signaling.

Identification of Mycobacterium tuberculosis CtpF as a target for designing new antituberculous compounds

The emergence of tuberculosis (TB) produced by multi-drug resistance (MDR) and extensively-drug resistance (XDR) Mycobacterium tuberculosis (Mtb), encourages the development of new antituberculous compounds, as well as the identification of novel drug targets. In this regard, plasma membrane P-type ATPases are interesting targets because they play a crucial role in ion homeostasis and mycobacterial survival. We focused on Mtb CtpF, a calcium P-type ATPase that responds to a broad number of intraphagosomal conditions, as a novel target. In this study, we evaluated the capacity of cyclopiazonic acid (CPA), a well-known inhibitor of the sarco-endoplasmic reticulum Ca²⁺-ATPase (SERCA), to inhibit the ATPase activity of CtpF and the Mtb growth demonstrating that CtpF is a druggable target. A homology modeling of CtpF was generated for molecular docking studies of CtpF with CPA and key pharmacophoric features were identified, which were used to perform a pharmacophore-based virtual screening of the ZINC database, and to identify CtpF inhibitor candidates. Molecular docking-based virtual screening and MM-BGSA calculations of candidates allowed identifying six compounds with the best binding energies. The compounds displayed in vitro minimum inhibitory concentrations (MIC) ranging from 50 to 100 μg/mL, growth inhibitions from 29.5 to 64.0% on Mtb, and inhibitions of Ca²⁺-dependent ATPase activity in Mtb membrane vesicles (IC₅₀) ranging from 4.1 to 35.8 μM. The compound ZINC63908257 was the best candidate by displaying a MIC of 50 μg/mL and a Ca²⁺ P-type ATPase inhibition of 45% with IC₅₀ = 4.4 μM. Overall, the results indicate that CtpF is a druggable target for designing new antituberculous compounds.

P-type transport ATPases in Leishmania and Trypanosoma

P-type ATPases are critical to the maintenance and regulation of cellular ion homeostasis and membrane lipid asymmetry due to their ability to move ions and phospholipids against a concentration gradient by utilizing the energy of ATP hydrolysis. P-type ATPases are particularly relevant in human pathogenic trypanosomatids which are exposed to abrupt and dramatic changes in their external environment during their life cycles. This review describes the complete inventory of ion-motive, P-type ATPase genes in the human pathogenic Trypanosomatidae; eight Leishmania species (L. aethiopica, L. braziliensis, L. donovani, L. infantum, L. major, L. mexicana, L. panamensis, L. tropica), Trypanosoma cruzi and three Trypanosoma brucei subspecies (Trypanosoma brucei brucei TREU927, Trypanosoma brucei Lister strain 427, Trypanosoma brucei gambiense DAL972). The P-type ATPase complement in these trypanosomatids includes the P_1B (metal pumps), P_2A (SERCA, sarcoplasmic-endoplasmic reticulum calcium ATPases), P_2B (PMCA, plasma membrane calcium ATPases), P_2D (Na⁺ pumps), P_3A (H⁺ pumps), P₄ (aminophospholipid translocators), and P_5B (no assigned specificity) subfamilies. These subfamilies represent the P-type ATPase transport functions necessary for survival in the Trypanosomatidae as P-type ATPases for each of these seven subfamilies are found in all Leishmania and Trypanosoma species included in this analysis. These P-type ATPase subfamilies are correlated with current molecular and biochemical knowledge of their function in trypanosomatid growth, adaptation, infectivity, and survival.

Conserved mechanism of phospholipid substrate recognition by the P4-ATPase Neo1 from Saccharomyces cerevisiae

The type IV P-type ATPases (P4-ATPases) thus far characterized are lipid flippases that transport specific substrates, such as phosphatidylserine (PS) and phosphatidylethanolamine (PE), from the exofacial leaflet to the cytofacial leaflet of membranes. This transport activity generates compositional asymmetry between the two leaflets important for signal transduction, cytokinesis, vesicular transport, and host-pathogen interactions. Most P4-ATPases function as a heterodimer with a β-subunit from the Cdc50 protein family, but Neo1 from Saccharomyces cerevisiae and its metazoan orthologs lack a β-subunit requirement and it is unclear how these proteins transport substrate. Here we tested if residues linked to lipid substrate recognition in other P4-ATPases also contribute to Neo1 function in budding yeast. Point mutations altering entry gate residues in the first (Q209A) and fourth (S457Q) transmembrane segments of Neo1, where phospholipid substrate would initially be selected, disrupt PS and PE membrane asymmetry, but do not perturb growth of cells. Mutation of both entry gate residues inactivates Neo1, and cells expressing this variant are inviable. We also identified a gain-of-function mutation in the second transmembrane segment of Neo1 (Neo1[Y222S]), predicted to help form the entry gate, that substantially enhances Neo1's ability to replace the function of a well characterized phospholipid flippase, Drs2, in establishing PS and PE asymmetry. These results suggest a common mechanism for substrate recognition in widely divergent P4-ATPases.

GABA operates upstream of H+-ATPase and improves salinity tolerance in Arabidopsis by enabling cytosolic K+ retention and Na+ exclusion

The non-protein amino acid γ-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to salinity. However, the physiological rationale for this elevation remains elusive. This study compared electrophysiological and whole-plant responses of salt-treated Arabidopsis mutants pop2-5 and gad1,2, which have different abilities to accumulate GABA. The pop2-5 mutant, which was able to overaccumulate GABA in its roots, showed a salt-tolerant phenotype. On the contrary, the gad1,2 mutant, lacking the ability to convert glutamate to GABA, showed oversensitivity to salinity. The greater salinity tolerance of the pop2-5 line was explained by: (i) the role of GABA in stress-induced activation of H+-ATPase, thus leading to better membrane potential maintenance and reduced stress-induced K+ leak from roots; (ii) reduced rates of net Na+ uptake; (iii) higher expression of SOS1 and NHX1 genes in the leaves, which contributed to reducing Na+ concentration in the cytoplasm by excluding Na+ to apoplast and sequestering Na+ in the vacuoles; (iv) a lower rate of H2O2 production and reduced reactive oxygen species-inducible K+ efflux from root epidermis; and (v) better K+ retention in the shoot associated with the lower expression level of GORK channels in plant leaves.

TAp73 regulates ATP7A: possible implications for ageing-related diseases

The p53 family member p73 controls a wide range of cellular function. Deletion of p73 in mice results in increased tumorigenesis, infertility, neurological defects and altered immune system. Despite the extensive effort directed to define the molecular underlying mechanism of p73 function a clear definition of its transcriptional signature and the extent of overlap with the other p53 family members is still missing. Here we describe a novel TAp73 target, ATP7A a member of a large family of P-type ATPases implicated in human neurogenerative conditions and cancer chemoresistance. Modulation of TAp73 expression influences basal expression level of ATP7A in different cellular models and chromatin immunoprecipitation confirmed a physical direct binding of TAp73 on ATP7A genomic regions. Bioinformatic analysis of expression profile datasets of human lung cancer patients suggests a possible implication of TAp73/ATP7A axis in human cancer. These data provide a novel TAp73-dependent target which might have implications in ageing-related diseases such as cancer and neurodegeneration.

In silico characterization of residues essential for substrate binding of human cystine transporter, xCT

xCT is a sodium-independent amino acid antiporter that imports L-cystine and exports L-glutamate in a 1:1 ratio. It is a component of heterodimeric amino acid transporter system Xc- working at the cross-roads of maintaining neurological processes and regulating antioxidant defense. The transporter has 12 transmembrane domains with intracellular N- and C-termini, and like other transporter proteins can undergo various conformational changes while switching the ligand accessibilities from intracellular to extracellular site. In the present study, we generated two homology models of human xCT in two distinct conformations: inward-facing occluded state and outward-facing open state. Our results indicated the substrate translocation channel composed of transmembrane helices TMs 1, 3, 6, 8, and 10. We docked anionic L-cystine and L-glutamate within the cavities to assess the two distinct binding scenarios for xCT as antiporter. We also assessed the interactions between the ligands and transporter and observed that ligands bind to similar residues within the channel. Using MM-PBSA/MM-GBSA approach, we computed the binding energies of these ligands to different conformational states. Cystine and glutamate bind xCT with favorable binding energies, with more favorable binding observed in inward occluded state than in outward open state. We further computed the residue-wise decomposition of these binding energies and identified the residues as essential for substrate binding/permeation. Filtering the residues that form favorable energetic contributions to the ligand binding in both the states, our studies suggest T56, A60, R135, A138, V141, Y244, A247, F250, S330, L392, and R396 as critical residues for ligand binding as well as ligand transport for any conformational state adopted by xCT during its transport cycle. .Graphical Abstract.

Modified Huang-Lian-Jie-Du Decoction Ameliorates Aβ Synaptotoxicity in a Murine Model of Alzheimer's Disease

Alzheimer's disease (AD) is a common neurodegenerative disease, characterized by cognitive dysfunction; however, the therapeutic strategies are not fully understood. Huang-Lian-Jie-Du-Decoction (HLJDD) is a famous traditional Chinese herbal formula that has been widely used clinically to treat dementia. Recently, according to previous study and our clinical practice, we generate a new modification of HLJDD (named modified-HLJDD). In this study, we indicated that modified-HLJDD attenuated learning and memory deficiencies in Aβ_1-42 oligomer-induced AD model, and we confirmed the exact metabolites in modified-HLJDD solution, as compared with HLJDD by UHPLC-Q-TOF-MS. Using GC-Q-TOF/MS-based metabolomics, we identified adenosine as the potential significant metabolite, responsible for modified-HLJDD regulating energy metabolism and synaptic plasticity in AD model. We also revealed that the potential underlying mechanism of modified-HLJDD in AD model may involve NMDA receptor-mediated glutamatergic transmission and adenosine/ATPase/AMPK cascade. Moreover, we also indicated the differential gut microbiota which mainly involved Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria at the phylum level upon modified-HLJDD treatment in AD model. Based on the correlation of metabolomic analysis with microbiome analysis, we clarified that Dorea is the most affected microbiota with adenosine upon modified-HLJDD treatment in AD model. Thus, our study suggests that modified-HLJDD may serve as a potential therapeutic drug in treating AD.

The P-type ATPase CtpF is a plasma membrane transporter mediating calcium efflux in Mycobacterium tuberculosis cells

Among the 12 P-type ATPases encoded by the genome of Mycobacterium tuberculosis (Mtb), CtpF responds to the greatest number of stress conditions, including oxidative stress, hypoxia, and infection. CtpF is the mycobacterial homolog of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) of higher eukaryotes. Its expression is regulated by the global regulator of latency, DosR. However, the role that CtpF plays in the mycobacterial plasma membrane remains unknown. In this study, different functional analyses showed that CtpF is associated with calcium pumping from mycobacterial cells. Specifically, Mtb CtpF expression in Mycobacterium smegmatis cells prevents Ca2+ accumulation compared with wild type (WT) cells. In addition, plasma membrane vesicles from recombinant membranes, in which the direction of ion transport is inverted, accumulate more Ca2+ compared with vesicles obtained from the WT strain. This findings support the hypothesis that CtpF contributes to calcium efflux from mycobacterial cells. Accordingly, Mtb cells defective in ctpF (MtbΔctpF) accumulate more Ca2+ compared with WT cells, while the Ca2+-dependent ATPase activity is significantly lower in the mutant cells. Interestingly, the deletion of ctpF in Mtb impairs the tolerance of the bacteria to oxidative and nitrosative stress. Overall, our results indicate that CtpF is associated with calcium pumping from mycobacterial cells and the response to oxidative stress.

Phenomics reveals a novel putative chloroplast fatty acid transporter in the marine diatom Skeletonema marinoi involved in temperature acclimation

Diatoms are the dominant phytoplankton in temperate oceans and coastal regions and yet little is known about the genetic basis underpinning their global success. Here, we address this challenge by developing the first phenomic approach for a diatom, screening a collection of randomly mutagenized but identifiably tagged transformants. Based upon their tolerance to temperature extremes, several compromised mutants were identified revealing genes either stress related or encoding hypothetical proteins of unknown function. We reveal one of these hypothetical proteins is a novel putative chloroplast fatty acid transporter whose loss affects several fatty acids including the two omega-3, long-chain polyunsaturated fatty acids - eicosapentaenoic and docosahexaenoic acid, both of which have medical importance as dietary supplements and industrial significance in aquaculture and biofuels. This mutant phenotype not only provides new insights into the fatty acid biosynthetic pathways in diatoms but also highlights the future value of phenomics for revealing specific gene functions in these ecologically important phytoplankton.

ATPase reaction cycle of P4-ATPases affects their transport from the endoplasmic reticulum

P4-ATPases belonging to the P-type ATPase superfamily mediate active transport of phospholipids across cellular membranes. Most P4-ATPases, except ATP9A and ATP9B proteins, form heteromeric complexes with CDC50 proteins, which are required for transport of P4-ATPases from the endoplasmic reticulum (ER) to their final destinations. P-type ATPases form autophosphorylated intermediates during the ATPase reaction cycle. However, the association of the catalytic cycle of P4-ATPases with their transport from the ER and their cellular localization has not been studied. Here, we show that transport of ATP9 and ATP11 proteins as well as that of ATP10A from the ER depends on the ATPase catalytic cycle, suggesting that conformational changes in P4-ATPases during the catalytic cycle are crucial for their transport from the ER.

Autoinhibition and activation mechanisms of the eukaryotic lipid flippase Drs2p-Cdc50p

The heterodimeric eukaryotic Drs2p-Cdc50p complex is a lipid flippase that maintains cell membrane asymmetry. The enzyme complex exists in an autoinhibited form in the absence of an activator and is specifically activated by phosphatidylinositol-4-phosphate (PI4P), although the underlying mechanisms have been unclear. Here we report the cryo-EM structures of intact Drs2p-Cdc50p isolated from S. cerevisiae in apo form and in the PI4P-activated form at 2.8 Å and 3.3 Å resolution, respectively. The structures reveal that the Drs2p C-terminus lines a long groove in the cytosolic regulatory region to inhibit the flippase activity. PIP4 binding in a cytosol-proximal membrane region triggers a 90° rotation of a cytosolic helix switch that is located just upstream of the inhibitory C-terminal peptide. The rotation of the helix switch dislodges the C-terminus from the regulatory region, activating the flippase.

Role of lipid transporters in fungal physiology and pathogenicity

The fungal cell wall and membrane are the most common targets of antifungal agents, but the potential of membrane lipid organization in regulating drug-target interactions has yet to be investigated. Energy-dependent lipid transporters have been recently associated with virulence and drug resistance in many pathogenic fungi. To illustrate this view, we discuss (i) the structural and biological aspects of ATP-driven lipid transporters, comprising P-type ATPases and ATP-binding cassette transporters, (ii) the role of these transporters in fungal physiology and virulence, and (iii) the potential of lipid transporters as targets for the development of novel antifungals. These recent observations indicate that the lipid-trafficking machinery in fungi is a promising target for studies on physiology, pathogenesis and drug development.

Inhibition and Activation of Kinases by Reaction Products: A Reporter-Free Assay

Kinases are widely distributed in nature and are implicated in many human diseases. Thus, an understanding of their activity and regulation is of fundamental importance. Several kinases are known to be inhibited by ADP. However, thorough investigation of this phenomenon is hampered by the lack of a simple and effective assay for studying this inhibition. We now present a quick, general approach for measuring the effects of reaction products on kinase activity. The method, based on isothermal titration calorimetry, is the first universal, reporter-free, continuous assay for probing kinase inhibition or activation by ADP. In applications to an aminoglycoside phosphotransferase [APH(3')-IIIa] and pantothenate kinases from Escherichia coli (EcPanK) and Pseudomonas aeruginosa (PaPanK), we found ADP to be an efficient inhibitor of all three kinases, with inhibition constant (K_i) values similar to or lower than the Michaelis-Menten constant (K_m) values of ATP. Interestingly, ADP was an activator at low concentrations and an inhibitor at high concentrations for EcPanK. This unusual effect was quantitatively modeled and attributed to cooperative interactions between the two subunits of the dimeric enzyme. Importantly, our results suggest that, at typical bacterial intracellular concentrations of ATP and ADP (approximately 1.5 mM and 180 μM, respectively), all three kinases are partially inhibited by ADP, allowing enzyme activity to rapidly respond to changes in the levels of both metabolites.

The Ability to Regulate Transmembrane Potassium Transport in Root Is Critical for Drought Tolerance in Barley

In this work, the effect of drought on K+ uptake in root and its translocation from root to shoot was investigated using six barley genotypes contrasting in drought tolerance. Results showed that drought conditions caused significant changes in K+ uptake and translocation in a time- and genotype-specific manner, which consequently resulted in a significant difference in tissue K+ contents and drought tolerance levels between the contrasting barley genotypes. The role of K+ transporters and channels and plasma membrane (PM) H+-ATPase in barley's adaptive response to drought stress was further investigated at the transcript level. The expression of genes conferring K+ uptake (HvHAK1, HvHAK5, HvKUP1, HvKUP2 and HvAKT1) and xylem loading (HvSKOR) in roots were all affected by drought stress in a time- and genotype-specific manner, indicating that the regulation of these K+ transporters and channels is critical for root K+ uptake and root to shoot K+ translocation in barley under drought stress. Furthermore, the barley genotypes showed a strong correlation between H+ efflux and K+ influx under drought stress, which was further confirmed by the significant up-regulation of HvHA1 and HvHA2. These results suggested an important role of plasma membrane H+-ATPase activity and/or expression in regulating the activity of K+ transporters and channels under drought stress. Taken together, it may be concluded that the genotypic difference in drought stress tolerance in barley is conferred by the difference in the ability to regulate K+ transporters and channels in root epidermis and stele.

Strong anion exchange-mediated phosphoproteomics reveals extensive human non-canonical phosphorylation

Phosphorylation is a key regulator of protein function under (patho)physiological conditions, and defining site-specific phosphorylation is essential to understand basic and disease biology. In vertebrates, the investigative focus has primarily been on serine, threonine and tyrosine phosphorylation, but mounting evidence suggests that phosphorylation of other "non-canonical" amino acids also regulates critical aspects of cell biology. However, standard methods of phosphoprotein characterisation are largely unsuitable for the analysis of non-canonical phosphorylation due to their relative instability under acidic conditions and/or elevated temperature. Consequently, the complete landscape of phosphorylation remains unexplored. Here, we report an unbiased phosphopeptide enrichment strategy based on strong anion exchange (SAX) chromatography (UPAX), which permits identification of histidine (His), arginine (Arg), lysine (Lys), aspartate (Asp), glutamate (Glu) and cysteine (Cys) phosphorylation sites on human proteins by mass spectrometry-based phosphoproteomics. Remarkably, under basal conditions, and having accounted for false site localisation probabilities, the number of unique non-canonical phosphosites is approximately one-third of the number of observed canonical phosphosites. Our resource reveals the previously unappreciated diversity of protein phosphorylation in human cells, and opens up avenues for high-throughput exploration of non-canonical phosphorylation in all organisms.

An unusual and vital protein with guanylate cyclase and P4-ATPase domains in a pathogenic protist

Toxoplasma gondii harbors an alveolate-specific guanylate cyclase linked to P-type ATPase motifs, which is an essential actuator of cGMP-dependent gliding motility, egress, and invasion during acute infection.

cGMP signaling is one of the master regulators of diverse functions in eukaryotes; however, its architecture and functioning in protozoans remain poorly understood. Herein, we report an exclusive guanylate cyclase coupled with N-terminal P4-ATPase in a common parasitic protist, Toxoplasma gondii. This bulky protein (477-kD), termed TgATPase_P-GC to fairly reflect its envisaged multifunctionality, localizes in the plasma membrane at the apical pole of the parasite, whereas the corresponding cGMP-dependent protein kinase (TgPKG) is distributed in the cytomembranes. TgATPase_P-GC is refractory to genetic deletion, and its CRISPR/Cas9–assisted disruption aborts the lytic cycle of T. gondii. Besides, Cre/loxP–mediated knockdown of TgATPase_P-GC reduced the synthesis of cGMP and inhibited the parasite growth due to impairments in the motility-dependent egress and invasion events. Equally, repression of TgPKG by a similar strategy recapitulated phenotypes of the TgATPase_P-GC–depleted mutant. Notably, despite a temporally restricted function, TgATPase_P-GC is expressed constitutively throughout the lytic cycle, entailing a post-translational regulation of cGMP signaling. Not least, the occurrence of TgATPase_P-GC orthologs in several other alveolates implies a divergent functional repurposing of cGMP signaling in protozoans, and offers an excellent drug target against the parasitic protists.

Cadmium-induced oxidative stress, histopathology, and transcriptome changes in the hepatopancreas of freshwater crayfish (Procambarus clarkii)

Cadmium (Cd) is a common contaminant in environment. Crayfish are considered suitable for indicating the impact of heavy metals on the environment. However, there is limited information on the mechanisms causing damage to the hepatopancreas of Procambarus clarkii exposed to Cd. We exposed adult male P. clarkii to 2.0, 5.0, and 10.0 mg/L Cd for 24, 48, and 72 h to explore Cd toxicity. Afterwards, we measured bioaccumulations in the hepatopancreas and determined malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST). Additionally, the hepatopancreas histopathology was analyzed and the transcriptome analysis of the P. clarkii hepatopancreas under Cd stress was conducted. The results revealed that hepatopancreas could accumulate Cd in a time- and dose-dependent manner. Cd induced significant changes in MDA content and antioxidant enzyme activity. Severe histological alterations were observed in crayfish hepatopancreas. After 72 h exposure to 2.0, 5.0, and 10.0 mg/L Cd, transcriptome analysis identified 1061, 747, and 1086 differentially expressed genes (DEGs), respectively. Exposure to 5.0 mg/L Cd inhibited heme binding, tetrapyrrole binding, iron ion binding and activity of oxidoreductase and sulfotransferase, while exposure to 10.0 mg/L Cd enhanced the export of matters from nucleus. In the hepatopancreas treated with 10.0 mg/L Cd, pathways related to diseases and immune system were significantly enriched. Meanwhile, 31, 31, 24, 7, and 12 identified DEGs were associated with the oxidation-reduction process, immune system, ion homeostasis, digestion and absorption, and ATPases, respectively. Our study provides comprehensive information for exploring the toxic mechanisms of Cd and candidate biomarkers for aquatic Cd risk evaluation.

New insights into copper homeostasis in filamentous fungi

Copper is a metal ion that is required as a micronutrient for growth and proliferation. However, copper accumulation generates toxicity by multiple mechanisms, potentially leading to cell death. Due to its toxic nature at high concentrations, different chemical variants of copper have been extensively used as antifungal agents in agriculture and medicine. Most studies on copper homeostasis have been carried out in bacteria, yeast, and mammalian organisms. However, knowledge on filamentous fungi is less well documented. This review summarizes the knowledge gathered in the last few years about copper homeostasis in the filamentous fungi Aspergillus fumigatus and Aspergillus nidulans: The mechanism of action of copper, the uptake and detoxification systems, their regulation at the transcriptional level, and the role of copper homeostasis in fungal pathogenicity are presented.

Emerging Diversity in Lipid-Protein Interactions

Membrane lipids interact with proteins in a variety of ways, ranging from providing a stable membrane environment for proteins to being embedded in to detailed roles in complicated and well-regulated protein functions. Experimental and computational advances are converging in a rapidly expanding research area of lipid-protein interactions. Experimentally, the database of high-resolution membrane protein structures is growing, as are capabilities to identify the complex lipid composition of different membranes, to probe the challenging time and length scales of lipid-protein interactions, and to link lipid-protein interactions to protein function in a variety of proteins. Computationally, more accurate membrane models and more powerful computers now enable a detailed look at lipid-protein interactions and increasing overlap with experimental observations for validation and joint interpretation of simulation and experiment. Here we review papers that use computational approaches to study detailed lipid-protein interactions, together with brief experimental and physiological contexts, aiming at comprehensive coverage of simulation papers in the last five years. Overall, a complex picture of lipid-protein interactions emerges, through a range of mechanisms including modulation of the physical properties of the lipid environment, detailed chemical interactions between lipids and proteins, and key functional roles of very specific lipids binding to well-defined binding sites on proteins. Computationally, despite important limitations, molecular dynamics simulations with current computer power and theoretical models are now in an excellent position to answer detailed questions about lipid-protein interactions.

A Chinese family with familial hemiplegic migraine type 2 due to a novel missense mutation in ATP1A2

Background

ATP1A2 has been identified as the genetic cause of familial hemiplegic migraine type 2. Over 80 ATP1A2 mutations have been reported, but no data from Chinese family studies has been included. Here, we report the first familial hemiplegic migraine type 2 Chinese family with a novel missense mutation.

Methods

Clinical manifestations in the family were recorded. Blood samples from patients and the unaffected members were collected for whole-exome sequencing to identify the pathogenic mutation. Seven online softwares (SIFT, PolyPhen-2, PROVEAN, PANTHER, MutationTaster2, MutationAssessor and PMut) were used for predicting the pathogenic potential of the mutation. PredictProtein, Jpred 4 and PyMOL were used to analyze structural changes of the protein. The mutation function was further tested by Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay.

Results

All patients in the family had typical hemiplegic migraine attacks. Co-segregation of the mutation with the migraine phenotype in four generations, with 10 patients, was completed. The identified novel mutation, G762S in ATP1A2, exhibited the disease-causing feature by all the predictive softwares. The mutation impaired the local structure of the protein and decreased cell viability.

Conclusion

G762S in ATP1A2 is a novel pathogenic mutation identified in a Chinese family with familial hemiplegic migraine, which causes loss of function by changing the protein structure of the Na+/K+-ATPase α2 subunit.

Catch You on the Flip Side: A Critical Review of Flippase Mutant Phenotypes

Lipid flippases are integral membrane proteins that use ATP hydrolysis to power the generation of phospholipid asymmetry between the two leaflets of biological membranes, a process essential for cell survival. Although the first report of a plant lipid flippase was published in 2000, progress in the field has been slow, partially due to the high level of redundancy in this gene family. However, recently an increasing number of reports have examined the physiological function of lipid flippases, mainly in Arabidopsis thaliana. In this review we aim to summarize recent findings on the physiological relevance of lipid flippases in plant adaptation to a changing environment and caution against misinterpretation of pleiotropic effects in genetic studies of flippases.

Saccharomyces cerevisiae as a Tool to Investigate Plant Potassium and Sodium Transporters

Sodium and potassium are two alkali cations abundant in the biosphere. Potassium is essential for plants and its concentration must be maintained at approximately 150 mM in the plant cell cytoplasm including under circumstances where its concentration is much lower in soil. On the other hand, sodium must be extruded from the plant or accumulated either in the vacuole or in specific plant structures. Maintaining a high intracellular K+/Na+ ratio under adverse environmental conditions or in the presence of salt is essential to maintain cellular homeostasis and to avoid toxicity. The baker's yeast, Saccharomyces cerevisiae, has been used to identify and characterize participants in potassium and sodium homeostasis in plants for many years. Its utility resides in the fact that the electric gradient across the membrane and the vacuoles is similar to plants. Most plant proteins can be expressed in yeast and are functional in this unicellular model system, which allows for productive structure-function studies for ion transporting proteins. Moreover, yeast can also be used as a high-throughput platform for the identification of genes that confer stress tolerance and for the study of protein-protein interactions. In this review, we summarize advances regarding potassium and sodium transport that have been discovered using the yeast model system, the state-of-the-art of the available techniques and the future directions and opportunities in this field.

Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus

The ubiquitous fungus Aspergillus flavus is notorious for contaminating many important crops and food-stuffs with the carcinogenic mycotoxin, aflatoxin. This fungus is also the second most frequent Aspergillus pathogen after A. fumigatus infecting immunosuppressed patients. In many human fungal pathogens including A. fumigatus, the ability to defend from toxic levels of copper (Cu) is essential in pathogenesis. In A. fumigatus, the Cu-fist DNA binding protein, AceA, and the Cu ATPase transporter, CrpA, play critical roles in Cu defense. Here, we show that A. flavus tolerates higher concentrations of Cu than A. fumigatus and other Aspergillus spp. associated with the presence of two homologs of A. fumigatus CrpA termed CrpA and CrpB. Both crpA and crpB are transcriptionally induced by increasing Cu concentrations via AceA activity. Deletion of crpA or crpB alone did not alter high Cu tolerance, suggesting they are redundant. Deletion of both genes resulted in extreme Cu sensitivity that was greater than that following deletion of the regulatory transcription factor aceA. The ΔcrpAΔcrpB and ΔaceA strains were also sensitive to ROI stress. Compared to wild type, these mutants were impaired in the ability to colonize maize seed treated with Cu fungicide but showed no difference in virulence on non-treated seed. A mouse model of invasive aspergillosis showed ΔcrpAΔcrpB and to a lesser degree ΔaceA to be significantly reduced in virulence, following the greater sensitivity of ΔcrpAΔcrpB to Cu than ΔaceA.