Eukaryotic V-ATPase: novel structural findings and functional insights

Dihydroartemisinin inhibits ATP6 activity, reduces energy metabolism of hepatocellular carcinoma cells, promotes apoptosis and inhibits metastasis via CANX

Dihydroartemisinin (DHA) may inhibit the migration and invasion of liver cancer cells by reducing ATP synthase production (specifically ATP1A1 and ATP5H) through the calcium/calmodulin dependent protein kinase kinase 2/solute carrier family 8 member B1 signaling pathway. However, it is unclear whether DHA regulates ATP synthase activity by modulating other calcium ion signals to inhibit the energy metabolism and the transfer of hepatocellular carcinoma (HCC) cells. Using the Gene Expression Profiling Interactive Analysis database, a search for specific expression genes in liver cancer tissues was performed. Human HCC HuH-7 and Li-7 cells were used to produce CANX overexpression and small interfering RNA cell models. The study assessed changes in cell proliferation, apoptosis, migration and invasion. Reactive oxygen species production, ATP production, mitochondrial membrane potential (JC-1), NAD+/NADH ratio and mitochondrial fluorescence were also evaluated. Western blotting was used to assess changes in CANX, ATP6V1 domain (ATP6V1F) and V0 domain (ATP6V0B) protein expression levels. The results demonstrated that CANX is highly expressed in liver cancer tissues. Furthermore, CANX regulated malignant biological behavior, mediated mitochondrial function and energy metabolism. However, these effects were inhibited by DHA, which decreased the expression of CANX, ATP6V0B and ATP6V1F. The findings of the present study underscore the central role of CANX in affecting the malignant biological behavior of liver cancer cells by regulating mitochondrial function and energy metabolism. Additionally, they indicate that DHA serves an anticancer role by inhibiting CANX expression.

Comprehensive analysis of ATP6V1s family member, ATP6V1C2, with prognostic and drug development values in colorectal cancer

Member of the V-type ATPase family have attracted vast attention in tumor progression. Nevertheless, the specific member of V-ATPase, ATP6V1C2, its regulatory function in colorectal cancer (CRC) progression was poorly understood. In this study, comprehensive analyses demonstrated the role of ATP6V1C2 in CRC progression and drug screening based on ATP6V1C2 was carried out. As a result, among the ATPV1s family, ATP6V1C2 was significantly highly expressed in CRC. Immuno-infiltration analysis suggests that, the interaction between CRC cells and immune cells resulting in reduced immune and estimate scores. GSEA analysis found that, ATP6V1C2 negatively correlates with immune cells，especially CD8T cells. Next, Ecotyper database queries indicated that ATP6V1C2 was negatively correlates with characteristic gene expression in CD8T cells. Then, COX regression analysis and survival curves made it clear that ATP6V1C2 is positively correlates with clinicopathological progression leading to poor CRC prognosis. CellMiner explore told us LOR-253 and Sonidegib may be effective in CRC cancer treatment. Molecular Docking between ATP6V1C2 and 9 first-line and 9 natural drugs showed that ATP6V1C2 was recognized by the best geometrical and energetic matching pattern of 2 First-line and 4 natural drugs. RT-PCR and immunoblotting confirmed that ATP6V1C2 was significantly overexpressed in CRC. Four natural drugs screened by molecular docking were effective in cell proliferation inhibition by CCK8 test. In summary, ATP6V1C2 may be a new therapeutic target for CRC. The illustration is shown in Figure 9.

Contractile vacuoles: a rapidly expanding (and occasionally diminishing?) understanding

Osmoregulation is the homeostatic mechanism essential for the survival of organisms in hypoosmotic and hyperosmotic conditions. In freshwater or soil dwelling protists this is frequently achieved through the action of an osmoregulatory organelle, the contractile vacuole. This endomembrane organelle responds to the osmotic challenges and compensates by collecting and expelling the excess water to maintain the cellular osmolarity. As compared with other endomembrane organelles, this organelle is underappreciated and under-studied. Here we review the reported presence or absence of contractile vacuoles across eukaryotic diversity, as well as the observed variability in the structure, function, and molecular machinery of this organelle. Our findings highlight the challenges and opportunities for constructing cellular and evolutionary models for this intriguing organelle.

Yeast TLDc domain proteins regulate assembly state and subcellular localization of the V-ATPase

Yeast vacuoles perform crucial cellular functions as acidic degradative organelles, storage compartments, and signaling hubs. These functions are mediated by important protein complexes, including the vacuolar-type H+-ATPase (V-ATPase), responsible for organelle acidification. To gain a more detailed understanding of vacuole function, we performed cross-linking mass spectrometry on isolated vacuoles, detecting many known as well as novel protein-protein interactions. Among these, we identified the uncharacterized TLDc-domain-containing protein Rtc5 as a novel interactor of the V-ATPase. We further analyzed the influence of Rtc5 and of Oxr1, the only other yeast TLDc-domain-containing protein, on V-ATPase function. We find that both Rtc5 and Oxr1 promote the disassembly of the vacuolar V-ATPase in vivo, counteracting the role of the RAVE complex, a V-ATPase assembly chaperone. Furthermore, Oxr1 is necessary for the retention of a Golgi-specific subunit of the V-ATPase in this compartment. Collectively, our results shed light on the in vivo roles of yeast TLDc-domain proteins as regulators of the V-ATPase, highlighting the multifaceted regulation of this crucial protein complex.

Loss of the Golgi-localized v-ATPase subunit does not alter insulin granule formation or pancreatic islet β-cell function

Delayed Golgi export of proinsulin has recently been identified as an underlying mechanism leading to insulin granule loss and β-cell secretory defects in type 2 diabetes (T2D). Because acidification of the Golgi lumen is critical for proinsulin sorting and delivery into the budding secretory granule, we reasoned that dysregulation of Golgi pH may contribute to proinsulin trafficking defects. In this report, we examined pH regulation of the Golgi and identified a partial alkalinization of the Golgi lumen in a diabetes model. To further explore this, we generated a β-cell specific knockout (KO) of the v0a2 subunit of the v-ATPase pump, which anchors the v-ATPase to the Golgi membrane. Although loss of v0a2 partially neutralized Golgi pH and was accompanied by distension of the Golgi cisternae, proinsulin export from the Golgi and insulin granule formation were not affected. Furthermore, β-cell function was well preserved. β-cell v0a2 KO mice exhibited normal glucose tolerance in both sexes, no genotypic difference to diet-induced obesity, and normal insulin secretory responses. Collectively, our data demonstrate the v0a2 subunit contributes to β-cell Golgi pH regulation but suggest that additional disturbances to Golgi structure and function contribute to proinsulin trafficking defects in diabetes.NEW & NOTEWORTHY Delayed proinsulin export from the Golgi in diabetic β-cells contributes to decreased insulin granule formation, but the underlying mechanisms are not clear. Here, we explored if dysregulation of Golgi pH can alter Golgi function using β-cell specific knockout (KO) of the Golgi-localized subunit of the v-ATPase, v0a2. We show that partial alkalinization of the Golgi dilates the cisternae, but does not affect proinsulin export, insulin granule formation, insulin secretion, or glucose homeostasis.

Vacuolar H+-ATPase and BZR1 form a feedback loop to regulate the homeostasis of BR signaling in Arabidopsis

Brassinosteroid (BR) is a vital plant hormone that regulates plant growth and development. BRASSINAZOLE RESISTANT 1 (BZR1) is a key transcription factor in BR signaling, and its nucleocytoplasmic localization is crucial for BR signaling. However, the mechanisms that regulate BZR1 nucleocytoplasmic distribution and thus the homeostasis of BR signaling remain largely unclear. The vacuole is the largest organelle in mature plant cells and plays a key role in maintenance of cellular pH, storage of intracellular substances, and transport of ions. In this study, we uncovered a novel mechanism of BR signaling homeostasis regulated by the vacuolar H+-ATPase (V-ATPase) and BZR1 feedback loop. Our results revealed that the vha-a2 vha-a3 mutant (vha2, lacking V-ATPase activity) exhibits enhanced BR signaling with increased total amount of BZR1, nuclear-localized BZR1, and the ratio of BZR1/phosphorylated BZR1 in the nucleus. Further biochemical assays revealed that VHA-a2 and VHA-a3 of V-ATPase interact with the BZR1 protein through a domain that is conserved across multiple species. VHA-a2 and VHA-a3 negatively regulate BR signaling by interacting with BZR1 and promoting its retention in the tonoplast. Interestingly, a series of molecular analyses demonstrated that nuclear-localized BZR1 could bind directly to specific motifs in the promoters of VHA-a2 and VHA-a3 to promote their expression. Taken together, these results suggest that V-ATPase and BZR1 may form a feedback regulatory loop to maintain the homeostasis of BR signaling in Arabidopsis, providing new insights into vacuole-mediated regulation of hormone signaling.

ATP6V1B2-related disorders featuring Lennox-Gastaut-syndrome: A case-based overview

BACKGROUND

ATP6V1B2 (ATPase, H+ transporting, lysosomal VI subunit B, isoform 2) encodes for a subunit of a ubiquitous transmembrane lysosomal proton pump, implicated in the acidification of intracellular organelles and in several additional cellular functions. Variants in ATP6V1B2 have been related to a heterogeneous group of multisystemic disorders sometimes associated with variable neurological involvement. However, our knowledge of genotype-phenotype correlations and the neurological spectrum of ATP6V1B2-related disorders remain limited due to the few numbers of reported cases.

CASE STUDY

We hereby report the case of an 18-year-old male Sicilian patient affected by a global developmental delay, skeletal abnormalities, and epileptic encephalopathy featuring Lennox-Gastaut syndrome (LGS), in which exome sequencing led to the identification of a novel de novo variant in ATP6V1B2 (NM_001693.4: c.973G > C, p.Gly325Arg).

CONCLUSIONS

Our report provides new insights on the inclusion of developmental epileptic encephalopathies (DEEs) within the continuum group of ATP6V1B2-related disorders, expanding the phenotypic and molecular spectrum associated with these conditions.

The hybrid RAVE complex plays V-ATPase-dependent and -independent pathobiological roles in Cryptococcus neoformans

V-ATPase, which comprises 13-14 subunits, is essential for pH homeostasis in all eukaryotes, but its proper function requires a regulator to assemble its subunits. While RAVE (regulator of H+-ATPase of vacuolar and endosomal membranes) and Raboconnectin-3 complexes assemble V-ATPase subunits in Saccharomyces cerevisiae and humans, respectively, the function of the RAVE complex in fungal pathogens remains largely unknown. In this study, we identified two RAVE complex components, Rav1 and Wdr1, in the fungal meningitis pathogen Cryptococcus neoformans, and analyzed their roles. Rav1 and Wdr1 are orthologous to yeast RAVE and human Rabconnectin-3 counterparts, respectively, forming the hybrid RAVE (hRAVE) complex. Deletion of RAV1 caused severe defects in growth, cell cycle control, morphogenesis, sexual development, stress responses, and virulence factor production, while the deletion of WDR1 resulted in similar but modest changes, suggesting that Rav1 and Wdr1 play central and accessary roles, respectively. Proteomics analysis confirmed that Wdr1 was one of the Rav1-interacting proteins. Although the hRAVE complex generally has V-ATPase-dependent functions, it also has some V-ATPase-independent roles, suggesting a unique role beyond conventional intracellular pH regulation in C. neoformans. The hRAVE complex played a critical role in the pathogenicity of C. neoformans, and RAV1 deletion attenuated virulence and impaired blood-brain barrier crossing ability. This study provides comprehensive insights into the pathobiological roles of the fungal RAVE complex and suggests a novel therapeutic strategy for controlling cryptococcosis.

Six states of Enterococcus hirae V-type ATPase reveals non-uniform rotor rotation during turnover

The vacuolar-type ATPase from Enterococcus hirae (EhV-ATPase) is a thus-far unique adaptation of V-ATPases, as it performs Na⁺ transport and demonstrates an off-axis rotor assembly. Recent single molecule studies of the isolated V₁ domain have indicated that there are subpauses within the three major states of the pseudo three-fold symmetric rotary enzyme. However, there was no structural evidence for these. Herein we activate the EhV-ATPase complex with ATP and identified multiple structures consisting of a total of six states of this complex by using cryo-electron microscopy. The orientations of the rotor complex during turnover, especially in the intermediates, are not as perfectly uniform as expected. The densities in the nucleotide binding pockets in the V₁ domain indicate the different catalytic conditions for the six conformations. The off-axis rotor and its' interactions with the stator a-subunit during rotation suggests that this non-uniform rotor rotation is performed through the entire complex.

ATP Synthase Subunit α from Helicoverpa armigera Acts as a Receptor of Bacillus thuringiensis Cry1Ac and Synergizes Cry1Ac Toxicity

Insect resistance to Bacillus thuringiensis (Bt) toxins has led to an urgent need to explore the insecticidal mechanisms of Bt. Previous studies indicated that Helicoverpa armigera ATP synthase subunit α (HaATPs-α) is involved in Cry1Ac resistance. In this study, a real-time quantitative polymerase chain reaction (RT-PCR) confirmed that HaATPs-α expression was significantly reduced in the Cry1Ac-resistant strain (BtR). Cry1Ac feeding induced the downregulated expression of HaATPs-α in the susceptible strain, but not in the BtR strain. Furthermore, the interaction between HaATPs-α and Cry1Ac was verified by ligand blotting and homologous competition experiments. The in vitro gain and loss of function analyses showed HaATPs-α involved in Cry1Ac toxicity by expressing endogenous HaATPs-α and HaATPs-α double-stranded RNAs in Sf9 and midgut cells, respectively. Importantly, purified HaATPs-α synergized Cry1Ac toxicity to H. armigera larvae. These findings provide the first evidence that HaATPs-α is a potential receptor of Cry1Ac, it shows downregulated participation in Cry1Ac resistance, and it exhibits higher enhancement of Cry1Ac toxicity to H. armigera larvae.

HOPS-dependent lysosomal fusion controls Rab19 availability for ciliogenesis in polarized epithelial cells

Primary cilia are sensory cellular organelles crucial for organ development and homeostasis. Ciliogenesis in polarized epithelial cells requires Rab19-mediated clearing of apical cortical actin to allow the cilium to grow from the apically-docked basal body into the extracellular space. Loss of the lysosomal membrane-tethering HOPS complex disrupts this actin-clearing and ciliogenesis, but it remains unclear how ciliary function of HOPS relates to its canonical function in regulating late endosome-lysosome fusion. Here, we show that disruption of HOPS-dependent lysosomal fusion indirectly impairs actin-clearing and ciliogenesis by disrupting the targeting of Rab19 to the basal body. We also find that Rab19 functions in endolysosomal cargo trafficking apart from its previously-identified role in ciliogenesis. In summary, we show that inhibition of lysosomal fusion abnormally accumulates Rab19 on late endosomes, thus depleting Rab19 from the basal body and thereby disrupting Rab19-mediated actin-clearing and ciliogenesis.

Summary statement

Loss of HOPS-mediated lysosomal fusion indirectly blocks apical actin clearing and ciliogenesis in polarized epithelia by trapping Rab19 on late endosomes and depleting Rab19 from the basal body.

Proton Pumping ATPases: Rotational Catalysis, Physiological Roles in Oral Pathogenic Bacteria, and Inhibitors

Proton pumping ATPases, both F-type and V/A-type ATPases, generate ATP using electrochemical energy or pump protons/sodium ions by hydrolyzing ATP. The enzymatic reaction and proton transport are coupled through subunit rotation, and this unique rotational mechanism (rotational catalysis) has been intensively studied. Single-molecule and thermodynamic analyses have revealed the detailed rotational mechanism, including the catalytically inhibited state and the roles of subunit interactions. In mammals, F- and V-ATPases are involved in ATP synthesis and organelle acidification, respectively. Most bacteria, including anaerobes, have F- and/or A-ATPases in the inner membrane. However, these ATPases are not believed to be essential in anaerobic bacteria since anaerobes generate sufficient ATP without oxidative phosphorylation. Recent studies suggest that F- and A-ATPases perform indispensable functions beyond ATP synthesis in oral pathogenic anaerobes; F-ATPase is involved in acid tolerance in Streptococcus mutans, and A-ATPase mediates nutrient import in Porphyromonas gingivalis. Consistently, inhibitors of oral bacterial F- and A-ATPases, such as phytopolyphenols and bedaquiline, strongly diminish growth and survival. Herein, we discuss rotational catalysis of bacterial F- and A-ATPases, and discuss their physiological roles, focusing on oral bacteria. We also review the effects of ATPase inhibitors on the growth and survival of oral pathogenic bacteria. The features of the catalytic mechanism and unique physiological roles in oral bacteria highlight the potential for proton pumping ATPases to serve as targets for oral antimicrobial agents.

Intracellular development and impact of a marine eukaryotic parasite on its zombified microalgal host

Parasites are widespread and diverse in oceanic plankton and many of them infect single-celled algae for survival. How these parasites develop and scavenge energy within the host and how the cellular organization and metabolism of the host is altered remain open questions. Combining quantitative structural and chemical imaging with time-resolved transcriptomics, we unveil dramatic morphological and metabolic changes of the marine parasite Amoebophrya (Syndiniales) during intracellular infection, particularly following engulfment and digestion of nutrient-rich host chromosomes. Changes include a sequential acristate and cristate mitochondrion with a 200-fold increase in volume, a 13-fold increase in nucleus volume, development of Golgi apparatus and a metabolic switch from glycolysis (within the host) to TCA (free-living dinospore). Similar changes are seen in apicomplexan parasites, thus underlining convergent traits driven by metabolic constraints and the infection cycle. In the algal host, energy-producing organelles (plastid, mitochondria) remain relatively intact during most of the infection. We also observed that sugar reserves diminish while lipid droplets increase. Rapid infection of the host nucleus could be a "zombifying" strategy, allowing the parasite to digest nutrient-rich chromosomes and escape cytoplasmic defense, whilst benefiting from maintained carbon-energy production of the host cell.

Identification of mEAK-7 as a human V-ATPase regulator via cryo-EM data mining

Vacuolar-type adenosine triphosphatases (V-ATPases) not only function as rotary proton pumps in cellular organelles but also serve as signaling hubs. To identify the endogenous binding partners of V-ATPase, we collected a large dataset of human V-ATPases and did extensive classification and focused refinement of human V-ATPases. Unexpectedly, about 17% of particles in state 2 of human V-ATPases display additional density with an overall resolution of 3.3 Å. Structural analysis combined with artificial intelligence modeling enables us to identify this additional density as mEAK-7, a protein involved in mechanistic target of rapamycin (mTOR) signaling in mammals. Our structure shows that mEAK-7 interacts with subunits A, B, D, and E of V-ATPases in state 2. Thus, we propose that mEAK-7 may regulate V-ATPase function through binding to V-ATPases in state 2 as well as mediate mTOR signaling.

Discovery and Study of Transmembrane Rotary Ion-Translocating Nano-Motors: F-ATPase/Synthase of Mitochondria/Bacteria and V-ATPase of Eukaryotic Cells

This review discusses the history of discovery and study of the operation of the two rotary ion-translocating ATPase nano-motors: (i) F-ATPase/synthase (holocomplex F₁F_O) of mitochondria/bacteria and (ii) eukaryotic V-ATPase (holocomplex V₁V_O). Vacuolar adenosine triphosphatase (V-ATPase) is a transmembrane multisubunit complex found in all eukaryotes from yeast to humans. It is structurally and functionally similar to the F-ATPase/synthase of mitochondria/bacteria and the A-ATPase/synthase of archaebacteria, which indicates a common evolutionary origin of the rotary ion-translocating nano-motors built into cell membranes and invented by Nature billions of years ago. Previously we have published several reviews on this topic with appropriate citations of our original research. This review is focused on the historical analysis of the discovery and study of transmembrane rotary ion-translocating ATPase nano-motors functioning in bacteria, eukaryotic cells and mitochondria of animals.

ATP synthesis in an ancient ATP synthase at low driving forces

SignificanceThe ATP synthases of many anaerobic archaea have an unusual motor subunit c that otherwise is only found in eukaryotic V₁V_O ATPases. The evolutionary switch from synthase to hydrolase is thought to be caused by a doubling of the rotor subunit c, followed by a loss of the ion binding site. By purification and reconstitution of an ATP synthase with a V-type c subunit, we have unequivocally demonstrated, against expectations, the capability of such an enzyme to synthesize ATP at physiological relevant driving forces of 90 to 150 mV. This is the long-awaited answer to an eminent question in microbial energetics and physiology, especially for life near the thermodynamic limit of ATP synthesis.

Detection and quantification of the vacuolar H+ATPase using the Legionella effector protein SidK

Acidification of secretory and endocytic organelles is required for proper receptor recycling, membrane traffic, protein degradation, and solute transport. Proton-pumping vacuolar H+ ATPases (V-ATPases) are responsible for this luminal acidification, which increases progressively as secretory and endocytic vesicles mature. An increasing density of V-ATPase complexes is thought to account for the gradual decrease in pH, but available reagents have not been sufficiently sensitive or specific to test this hypothesis. We introduce a new probe to localize and quantify V-ATPases. The probe is derived from SidK, a Legionella pneumophila effector protein that binds to the V-ATPase A subunit. We generated plasmids encoding fluorescent chimeras of SidK1-278, and labeled recombinant SidK1-278 with Alexa Fluor 568 to visualize and quantify V-ATPases with high specificity in live and fixed cells, respectively. We show that V-ATPases are acquired progressively during phagosome maturation, that they distribute in discrete membrane subdomains, and that their density in lysosomes depends on their subcellular localization.

Gills full-length transcriptomic analysis of osmoregulatory adaptive responses to salinity stress in Coilia nasus

Salinity changes will threaten the survival of aquatic animals. However, osmoregulatory mechanism of Coilia nasus has not been explored. Oxford Nanopore Technologies (ONT) sequencing was performed in C. nasus gills during hypotonic and hyperosmotic stress. 23.8 G clean reads and 27,659 full-length non-redundant sequences were generated via ONT sequencing. Alternative splicing, alternative polyadenylation, transcript factors, and long noncoding RNA were identified. During hypotonic stress, 58 up-regulated differentially expressed genes (DEGs) and 36 down-regulated DEGs were identified. During hypertonic stress, 429 up-regulated DEGs and 480 down-regulated DEGs were identified. These DEGs were associated with metabolism, cell cycle, and transport. The analysis of these DEGs indicated that carbohydrate and fatty acid metabolism were activated to provide energy for cell cycle and transport during hypotonic and hypertonic stress. Cell cycle was also promoted during hypotonic and hypertonic stress. To resist hypotonic stress, polyamines metabolism, ion absorption and water transport from extra-cellular to intra-cellular were promoted, while ion secretion was inhibited. During hypotonic stress, glutamine, alanine, proline, and inositol metabolism were activated. Ion absorption and water transport from intra-cellular to extra-cellular were inhibited. Moreover, different transcript isoforms generated from the same gene performed different expression patterns during hypotonic and hypertonic stress. These findings will be beneficial to understand osmoregulatory mechanism of Coilia nasus.

Ion Channels and Pumps in Autophagy: A Reciprocal Relationship

Autophagy, the process of cellular self-degradation, is intrinsically tied to the degradative function of the lysosome. Several diseases have been linked to lysosomal degradative defects, including rare lysosomal storage disorders and neurodegenerative diseases. Ion channels and pumps play a major regulatory role in autophagy. Importantly, calcium signaling produced by TRPML1 (transient receptor potential cation channel, mucolipin subfamily) has been shown to regulate autophagic progression through biogenesis of autophagic-lysosomal organelles, activation of mTORC1 (mechanistic target of rapamycin complex 1) and degradation of autophagic cargo. ER calcium channels such as IP₃Rs supply calcium for the lysosome, and lysosomal function is severely disrupted in the absence of lysosomal calcium replenishment by the ER. TRPML1 function is also regulated by LC3 (microtubule-associated protein light chain 3) and mTORC1, two critical components of the autophagic network. Here we provide an overview of the current knowledge about ion channels and pumps-including lysosomal V-ATPase (vacuolar proton-ATPase), which is required for acidification and hence proper enzymatic activity of lysosomal hydrolases-in the regulation of autophagy, and discuss how functional impairment of some of these leads to diseases.

Full-length transcriptomic analysis reveals osmoregulatory mechanisms in Coilia nasus eyes reared under hypotonic and hyperosmotic stress

In recent years, sea-level rise, caused by global warming, will trigger salinity changes. This will threaten the survival of aquatic animals. Till now, the osmoregulatory mechanism of Coilia nasus eyes has not been yet explored. Oxford Nanopore Technologies (ONT) sequencing was performed in C. nasus eyes during hypotonic and hyperosmotic stress for the first time. 22.5G clean reads and 26,884 full-length non-redundant sequences were generated via ONT sequencing. AS events, APA, TF, and LncRNA were identified. During hypotonic stress, 46 up-regulated DEGs and 28 down-regulated DEGs were identified. During hypertonic stress, 190 up-regulated DEGs and 182 down-regulated DEGs were identified. These DEGs were associated with immune, metabolism, and transport responses. The expression of these DEGs indicated that apoptosis and inflammation were triggered during hypotonic and hyperosmotic stress. To resist hypotonic stress, polyamines metabolism and transport of Na⁺ and Cl^- from inter-cellular to extra-cellular were activated. During hyperosmotic stress, amino acids metabolism and transport of myo-inositol and Na⁺ from extra-cellular to inter-cellular were activated, while Cl^- transport was inhibited. Moreover, different transcript isoforms generated from the same gene performed different expression patterns during hypotonic and hypertonic stress. These findings will be beneficial to understand osmoregulatory mechanism of C. nasus eyes, and can also improve our insights on the adaptation of aquatic animals to environmental changes.

Whole-genome resequencing of three Coilia nasus population reveals genetic variations in genes related to immune, vision, migration, and osmoregulation

Background

Coilia nasus is an important anadromous fish, widely distributed in China, Japan, and Korea. Based on morphological and ecological researches of C. nasus, two ecotypes were identified. One is the anadromous population (AP). The sexually mature fish run thousands of kilometers from marine to river for spawning. Another one is the resident population which cannot migrate. Based on their different habitats, they were classified into landlocked population (LP) and sea population (SP) which were resident in the freshwater lake and marine during the entire lifetime, respectively. However, they have never been systematically studied. Moreover, C. nasus is declining sharply due to overfishing and pollution recently. Therefore, further understandings of C. nasus populations are needed for germplasm protection.

Results

Whole-genome resequencing of AP, LP, and SP were performed to enrich the understanding of different populations of C. nasus. At the genome level, 3,176,204, 3,307,069, and 3,207,906 single nucleotide polymorphisms (SNPs) and 1,892,068, 2,002,912, and 1,922,168 insertion/deletion polymorphisms (InDels) were generated in AP, LP, and SP, respectively. Selective sweeping analysis showed that 1022 genes were selected in AP vs LP; 983 genes were selected in LP vs SP; 116 genes were selected in AP vs SP. Among them, selected genes related to immune, vision, migration, and osmoregulation were identified. Furthermore, their expression profiles were detected by quantitative real-time PCR. Expression levels of selected genes related to immune, and vision in LP were significantly lower than AP and SP. Selected genes related to migration in AP were expressed significantly more highly than LP. Expression levels of selected genes related to osmoregulation were also detected. The expression of NKAα and NKCC1 in LP were significantly lower than SP, while expression of NCC, SLC4A4, NHE3, and V-ATPase in LP was significantly higher than SP.

Conclusions

Combined to life history of C. nasus populations, our results revealed that the molecular mechanisms of their differences of immune, vision, migration, and osmoregulation. Our findings will provide a further understanding of different populations of C. nasus and will be beneficial for wild C. nasus protection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08182-0.

Glioblastoma cytotoxicity conferred through dual disruption of endolysosomal homeostasis by Vacquinol-1

Background

Increased membrane trafficking is observed in numerous cancer types, including glioblastoma. Targeting the oncogenic driven acquired alterations in membrane trafficking by synthetic cationic amphiphilic small molecules has recently been shown to induce death of glioblastoma cells, although the molecular targets are unknown.

Methods

The mechanism of action of the cationic amphiphilic drug Vacquinol-1 (Vacq1)-induced cytotoxicity was investigated using cell biology, biochemistry, functional experiments, chemical biology, unbiased antibody-based post-translation modification profiling, and mass spectrometry-based chemical proteomic analysis on patient-derived glioblastoma cells.

Results

Vacq1 induced two types of abnormal endolysosomal vesicles, enlarged vacuoles and acidic vesicle organelles (AVOs). Mechanistically, enlarged vacuoles were formed by the impairment of lysosome reformation through the direct interaction and inhibition of calmodulin (CaM) by Vacq1, while AVO formation was induced by Vacq1 accumulation and acidification in the endosomal compartments through its activation of the v-ATPase. As a consequence of v-ATPase activation, cellular ATP consumption markedly increased, causing cellular energy shortage and cytotoxicity. This effect of Vacq1 was exacerbated by its inhibitory effects on calmodulin, causing lysosomal depletion and a failure of acidic vesicle organelle clearance.

Conclusion

Our study identifies the targets of Vacq1 and the mechanisms underlying its selective cytotoxicity in glioblastoma cells. The dual function of Vacq1 sets in motion a glioblastoma-specific vicious cycle of ATP consumption resulting in cellular energy crisis and cell death.

Mechanisms and regulation of organic acid accumulation in plant vacuoles

In fleshy fruits, organic acids are the main source of fruit acidity and play an important role in regulating osmotic pressure, pH homeostasis, stress resistance, and fruit quality. The transport of organic acids from the cytosol to the vacuole and their storage are complex processes. A large number of transporters carry organic acids from the cytosol to the vacuole with the assistance of various proton pumps and enzymes. However, much remains to be explored regarding the vacuolar transport mechanism of organic acids as well as the substances involved and their association. In this review, recent advances in the vacuolar transport mechanism of organic acids in plants are summarized from the perspectives of transporters, channels, proton pumps, and upstream regulators to better understand the complex regulatory networks involved in fruit acid formation.

Comprehensive Analysis of Mouse Hippocampal Lysine Acetylome Mediated by Sea Cucumber Peptides Preventing Memory Impairment

Memory impairment is becoming a potential health issue with the delicacy of diet and social stress. Sea cucumber peptides (SCP) prevent memory impairment, as previously reported. In this study, further research was performed using hippocampal lysine-acetylome to explore molecular regulation mechanisms. C57BL/6 mice were treated with scopolamine via intraperitoneal injection to simulate memory impairment. To determine the influence of SCP on the total acetylated-protein level of the hippocampus, acetylated-proteomics was performed. SCP increased the acetylation level of histone (H3 and H4). Meanwhile, for non-histones, the differentially acetylated proteins were involved in multiple memory-related pathways, as shown by KEGG enrichment analysis. Additionally, long-term potentiation was confirmed by western blotting. Finally, a combined analysis of proteome and lysine acetylome revealed that SCP contributed to synaptic vesicle cycle regulation and dopamine metabolism. Consequently, our findings revealed that SCP was potentially neuroprotective by regulating post-transcriptional hippocampal protein acetylation.

Loss of vacuolar-type H+-ATPase induces caspase-independent necrosis-like death of hair cells in zebrafish neuromasts

The vacuolar-type H+-ATPase (V-ATPase) is a multi-subunit proton pump that regulates cellular pH. V-ATPase activity modulates several cellular processes, but cell-type-specific functions remain poorly understood. Patients with mutations in specific V-ATPase subunits can develop sensorineural deafness, but the underlying mechanisms are unclear. Here, we show that V-ATPase mutations disrupt the formation of zebrafish neuromasts, which serve as a model to investigate hearing loss. V-ATPase mutant neuromasts are small and contain pyknotic nuclei that denote dying cells. Molecular markers and live imaging show that loss of V-ATPase induces mechanosensory hair cells in neuromasts, but not neighboring support cells, to undergo caspase-independent necrosis-like cell death. This is the first demonstration that loss of V-ATPase can lead to necrosis-like cell death in a specific cell type in vivo. Mechanistically, loss of V-ATPase reduces mitochondrial membrane potential in hair cells. Modulating the mitochondrial permeability transition pore, which regulates mitochondrial membrane potential, improves hair cell survival. These results have implications for understanding the causes of sensorineural deafness, and more broadly, reveal functions for V-ATPase in promoting survival of a specific cell type in vivo.

The V-ATPase a3 Subunit: Structure, Function and Therapeutic Potential of an Essential Biomolecule in Osteoclastic Bone Resorption

This review focuses on one of the 16 proteins composing the V-ATPase complex responsible for resorbing bone: the a3 subunit. The rationale for focusing on this biomolecule is that mutations in this one protein account for over 50% of osteopetrosis cases, highlighting its critical role in bone physiology. Despite its essential role in bone remodeling and its involvement in bone diseases, little is known about the way in which this subunit is targeted and regulated within osteoclasts. To this end, this review is broadened to include the three other mammalian paralogues (a1, a2 and a4) and the two yeast orthologs (Vph1p and Stv1p). By examining the literature on all of the paralogues/orthologs of the V-ATPase a subunit, we hope to provide insight into the molecular mechanisms and future research directions specific to a3. This review starts with an overview on bone, highlighting the role of V-ATPases in osteoclastic bone resorption. We then cover V-ATPases in other location/functions, highlighting the roles which the four mammalian a subunit paralogues might play in differential targeting and/or regulation. We review the ways in which the energy of ATP hydrolysis is converted into proton translocation, and go in depth into the diverse role of the a subunit, not only in proton translocation but also in lipid binding, cell signaling and human diseases. Finally, the therapeutic implication of targeting a3 specifically for bone diseases and cancer is discussed, with concluding remarks on future directions.

Comparative genomics reveals new functional insights in uncultured MAST species

Heterotrophic lineages of stramenopiles exhibit enormous diversity in morphology, lifestyle, and habitat. Among them, the marine stramenopiles (MASTs) represent numerous independent lineages that are only known from environmental sequences retrieved from marine samples. The core energy metabolism characterizing these unicellular eukaryotes is poorly understood. Here, we used single-cell genomics to retrieve, annotate, and compare the genomes of 15 MAST species, obtained by coassembling sequences from 140 individual cells sampled from the marine surface plankton. Functional annotations from their gene repertoires are compatible with all of them being phagocytotic. The unique presence of rhodopsin genes in MAST species, together with their widespread expression in oceanic waters, supports the idea that MASTs may be capable of using sunlight to thrive in the photic ocean. Additional subsets of genes used in phagocytosis, such as proton pumps for vacuole acidification and peptidases for prey digestion, did not reveal particular trends in MAST genomes as compared with nonphagocytotic stramenopiles, except a larger presence and diversity of V-PPase genes. Our analysis reflects the complexity of phagocytosis machinery in microbial eukaryotes, which contrasts with the well-defined set of genes for photosynthesis. These new genomic data provide the essential framework to study ecophysiology of uncultured species and to gain better understanding of the function of rhodopsins and related carotenoids in stramenopiles.

Characterization of micron-scale protein-depleted plasma membrane domains in phosphatidylserine-deficient yeast cells

Membrane phase separation to form micron-scale domains of lipids and proteins occurs in artificial membranes; however, a similar large-scale phase separation has not been reported in the plasma membrane of the living cells. We show here that a stable micron-scale protein-depleted region is generated in the plasma membrane of yeast mutants lacking phosphatidylserine at high temperatures. We named this region the 'void zone'. Transmembrane proteins and certain peripheral membrane proteins and phospholipids are excluded from the void zone. The void zone is rich in ergosterol, and requires ergosterol and sphingolipids for its formation. Such properties are also found in the cholesterol-enriched domains of phase-separated artificial membranes, but the void zone is a novel membrane domain that requires energy and various cellular functions for its formation. The formation of the void zone indicates that the plasma membrane in living cells has the potential to undergo phase separation with certain lipid compositions. We also found that void zones were frequently in contact with vacuoles, in which a membrane domain was also formed at the contact site.

Genetic Variability in Molecular Pathways Implicated in Alzheimer's Disease: A Comprehensive Review

Alzheimer's disease (AD) is a complex neurodegenerative disease, affecting a significant part of the population. The majority of AD cases occur in the elderly with a typical age of onset of the disease above 65 years. AD presents a major burden for the healthcare system and since population is rapidly aging, the burden of the disease will increase in the future. However, no effective drug treatment for a full-blown disease has been developed to date. The genetic background of AD is extensively studied; numerous genome-wide association studies (GWAS) identified significant genes associated with increased risk of AD development. This review summarizes more than 100 risk loci. Many of them may serve as biomarkers of AD progression, even in the preclinical stage of the disease. Furthermore, we used GWAS data to identify key pathways of AD pathogenesis: cellular processes, metabolic processes, biological regulation, localization, transport, regulation of cellular processes, and neurological system processes. Gene clustering into molecular pathways can provide background for identification of novel molecular targets and may support the development of tailored and personalized treatment of AD.

The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease

A primary function of the H⁺-ATPase (or V-ATPase) is to create an electrochemical proton gradient across eukaryotic cell membranes, which energizes fundamental cellular processes. Its activity allows for the acidification of intracellular vesicles and organelles, which is necessary for many essential cell biological events to occur. In addition, many specialized cell types in various organ systems such as the kidney, bone, male reproductive tract, inner ear, olfactory mucosa, and more, use plasma membrane V-ATPases to perform specific activities that depend on extracellular acidification. It is, however, increasingly apparent that V-ATPases are central players in many normal and pathophysiological processes that directly influence human health in many different and sometimes unexpected ways. These include cancer, neurodegenerative diseases, diabetes, and sensory perception, as well as energy and nutrient-sensing functions within cells. This review first covers the well-established role of the V-ATPase as a transmembrane proton pump in the plasma membrane and intracellular vesicles and outlines factors contributing to its physiological regulation in different cell types. This is followed by a discussion of the more recently emerging unconventional roles for the V-ATPase, such as its role as a protein interaction hub involved in cell signaling, and the (patho)physiological implications of these interactions. Finally, the central importance of endosomal acidification and V-ATPase activity on viral infection will be discussed in the context of the current COVID-19 pandemic.

Shear Stress Increases V-H + -ATPase and Acidic Vesicle Number Density, and p-mTORC2 Activation in Prostate Cancer Cells

Introduction

Cells in the tumor microenvironment experience mechanical stresses, such as compression generated by uncontrolled cell growth within a tissue, increased substrate stiffness due to tumor cell extracellular matrix (ECM) remodeling, and leaky angiogenic vessels which involve low fluid shear stress. With our hypothesis that shear stress increases V-H + -ATPase number density in prostate cancer cells via activation of the mTORC1 and mTORC2 pathways, we demonstrated and quantified such a mechanism in prostate cancer cells.

Methods

Moderately metastatic DU145 and highly metastatic PC3 prostate cancer cells were subjected to 0.05 dynes cm - 2 wall shear stress for 24 h, followed by immunocytochemistry and fluorescence measurements of β 1 integrin, endosome, lysosome, V-H + -ATPase proton pump, mTORC1, and p-mTORC2 antibodies. Post shear stress migration assays, and the effects of vacuolar proton pump inhibitor Bafilomycin A1 (60 nM, 24 h) as well as shear stress on the ICC fluorescence intensity of the proteins of interest were conducted with DU145 cells.

Results

Low fluid shear stress increases the fluorescence intensity of β 1 integrin, endosome, lysosome, V-H + -ATPase, mTORC1, and p-mTORC2 antibodies in PC3 and DU145 cells, and also increased cell migration. However, Bafilomycin A1 decreased fluorescence intensity of all of these proteins in DU145 cells exposed to shear stress, revealing that V-H + -ATPase controls the expression of these proteins.

Conclusions

Prostate cancer cell mechanotransduction increases endosomes, lysosomes, and proton pumps-where increases have been associated with enhanced cancer aggressiveness. We also show that the prostate cancer cell's response to force promotes the cancer drivers mTORC1 and mTORC2.

The Arabidopsis V-ATPase is localized to the TGN/EE via a seed plant-specific motif

The V-ATPase is a versatile proton-pump found in a range of endomembrane compartments yet the mechanisms governing its differential targeting remain to be determined. In Arabidopsis, VHA-a1 targets the V-ATPase to the TGN/EE whereas VHA-a2 and VHA-a3 are localized to the tonoplast. We report here that the VHA-a1 targeting domain serves as both an ER-exit and as a TGN/EE-retention motif and is conserved among seed plants. In contrast, Marchantia encodes a single VHA-isoform that localizes to the TGN/EE and the tonoplast in Arabidopsis. Analysis of CRISPR/Cas9 generated null alleles revealed that VHA-a1 has an essential function for male gametophyte development but acts redundantly with the tonoplast isoforms during vegetative growth. We propose that in the absence of VHA-a1, VHA-a3 is partially re-routed to the TGN/EE. Our findings contribute to understanding the evolutionary origin of V-ATPase targeting and provide a striking example that differential localization does not preclude functional redundancy.

Comprehensive Analysis of ATP6V1s Family Members in Renal Clear Cell Carcinoma With Prognostic Values

ATP6V1s participate in the biological process of transporting hydrogen ions and are associated with various cancers in expression and clinicopathological features, while its role in kidney renal clear cell carcinoma is unknown. We aimed to demonstrate the relationship between ATP6V1s and kidney renal clear cell carcinoma. This study investigated the expression and roles of ATP6V1s in KIRC using Oncomine, The Cancer Genome Atlas, UALCAN, Human Protein Atlas, Clinical Proteomics Tumor Analysis Consortium, GeneMANIA, Tumor IMmune Estimation Resource, GEPIA databases. Low mRNA and protein expression of ATP6V1s members were found to be significantly associated with clinical cancer stages, nodal metastasis status, and patient's gender in KIRC patients. Besides, lower mRNA expression of ATP6V1A, ATP6V1B2, ATP6V1C1, ATP6V1C2, ATP6V1D, ATP6V1E1, ATP6V1E2, ATP6V1F, ATP6V1G1, and ATP6V1H have shorter OS. Taken together, these results indicated that ATP6V1s family members could be a potential target in the development of anti-KIRC therapeutics and an efficient marker of the prognostic value of KIRC.

Comparative Ubiquitome Analysis under Heat Stress Reveals Diverse Functions of Ubiquitination in Saccharina japonica

Ubiquitination is a major post-translational modification involved in nearly all aspects of eukaryotic biology. Previous RNA-Seq studies showed that ubiquitination plays essential roles in the heat tolerance of Saccharina japonica, but to date, large-scale profiling of the ubiquitome in S. japonica has not been reported. To better understand the regulatory roles of ubiquitination in heat responses of S. japonica, we investigated its ubiquitome under normal and heat stress by the combination of affinity enrichment and high-resolution liquid chromatography-tandem mass spectroscopy analysis. Altogether, 3305 lysine ubiquitination sites in 1562 protein groups were identified. After normalization, 152 lysine ubiquitination sites in 106 proteins were significantly upregulated and 208 lysine ubiquitination sites in 131 proteins were significantly downregulated in response to heat stress. Protein annotation and functional analysis suggested that ubiquitination modulates a variety of essential cellular and physiological processes, including but not limited to the ubiquitin-26S proteasome system, ribosome, carbohydrate metabolism, and oxidative phosphorylation. Our results provide a global view of the heat response ubiquitome in S. japonica, and could facilitate future studies on the physiological roles of these ubiquitination-related proteins.

An affinity change model to elucidate the rotation mechanism of V1-ATPase

V-ATPases are ubiquitous proton-transporting ATPases of eukaryotic and prokaryotic membranes that utilize energy from ATP hydrolysis. The hydrophilic catalytic part called V₁-ATPase is composed of a ring-shaped hexametric A₃B₃ complex and a central DF shaft. We previously proposed a rotation mechanism of the Enterococcus hirae V₁-ATPase based on the crystal structures of the V₁ and A₃B₃ complexes. However, the driving force that induces the conformational changes of A₃B₃ and rotation of the DF shaft remains unclear. In this study, we investigated the binding affinity changes between subunits of V₁-ATPase by surface plasmon resonance analysis. The binding of ATP to subunit A was found to considerably increase the affinity between the A and B subunits, and thereby ATP binding contributes to forming the A₁B₁ tight conformation. Furthermore, the DF shaft bound to the reconstituted A₁B₁ complex with high affinity, suggesting that the tight A₁B₁ complex is a major binding unit of the shaft in the A₃B₃ ring complex. Based on these results, we propose that rotation of the V₁-ATPase is driven by affinity changes between each subunit via thermal fluctuations.

ATP6V0D2, a subunit associated with proton transport, serves an oncogenic role in esophagus cancer and is correlated with epithelial-mesenchymal transition

BACKGROUND

The poor prognosis of esophagus cancer (EC) is mainly due to its high invasiveness and metastasis, so it is urgent to search effectively prognostic markers and explore their roles in the mechanism of metastasis.

MATERIALS AND METHODS

Based on the TCGA database, we downloaded the RNA-Seq for analyzing the expression of ATP6V0D2. QRT-PCR was used to test the mRNA levels of ATP6V0D2 in cell lines. Chi-square tests were used to evaluate the correlation between ATP6V0D2 and clinical characteristics. Prognostic values were determined by Kaplan-Meier methods and cox's regression models. CCK-8 and clone formation assays were employed to evaluate the cell viability, and Transwell assay was implemented to determine the invasive and migratory abilities. Correlations between ATP6V0D2 and motion-related markers were analyzed by the GEPIA database and confirmed by western blot. Moreover, the relationship between ATP6V0D2 and molecules related to cell cycle and apoptosis was also determined by western blot.

RESULTS

A significant increase was observed in 3 EC-related cell lines compared to the normal cell line. ATP6V0D2 has a connection with the poor prognosis and can be considered as an independent prognosticator for patients with EC. Besides, ATP6V0D2 can improve cells viability as well as invasive and migratory abilities. What's more, downregulation of ATP6V0D2 notably enhanced E-cadherin expression, while decreased N-cadherin, Vimentin, and MMP9 expression, whereas overexpression of ATP6V0D2 presented the opposite outcomes. Furthermore, we found that silencing ATP6V0D2 led to a significant reduction on the protein expression of Cyclin D1, CDK4, Bcl-2, whereas resulted in a notable enhancement on the Bax level.

CONCLUSION

ATP6V0D2 might be an independent prognosticator for EC patients, and it possibly promotes tumorigenesis by regulating epithelial-mesenchymal transition, cell cycle and apoptosis-related markers, providing the possibility that ATP6V0D2 may be a novel biomarker for the therapeutic intervention of EC.

Infectivity and genes differentially expressed between young and aging theront cells of the marine fish parasite Cryptocaryon irritans

The ciliated protozoan Cryptocaryon irritans infects a wide range of marine fish and causes the highly lethal white spot disease. This parasite possesses three morphologically and physiologically distinct life stages: an infectious theront, a parasitic trophont, and an asexually reproductive tomont. In the past few years, several attempts have been made to help elucidate how C. irritans transforms from one stage to another using transcriptomic or proteomic approaches. However, there has been no research studying changes in transcription profiles between different time points of a single C. irritans life stage—the development of this parasite. Here we use RNA-seq and compare gene expression profiles of theront cells collected by 1 and 10 hrs after they emerged from tomonts. It has been shown that infectivity of theront cells declines 6–8 hours post-emergence, and we used this characteristic as a physiological marker to confirm the aging of theront cells. We identified a total of 41 upregulated and 90 downregulated genes that were differentially expressed between young and aging theront cells. Using Blast2Go to further analyze functions of these genes, we show that genes related to energy production are downregulated, but quite surprisingly many genes involved in transcription/translation processes are upregulated. We also show that expression of all nine detectable agglutination/immobilization antigen genes, with great sequence divergence, is invariably downregulated. Functions of other differentially expressed genes and indications are also discussed in our study.

Interplay Between V-ATPase G1 and Small EV-miRNAs Modulates ERK1/2 Activation in GBM Stem Cells and Nonneoplastic Milieu

The ATP6V1G1 subunit (V1G1) of the vacuolar proton ATPase (V-ATPase) pump is crucial for glioma stem cells (GSC) maintenance and in vivo tumorigenicity. Moreover, V-ATPase reprograms the tumor microenvironment through acidification and release of extracellular vesicles (EV). Therefore, we investigated the role of V1G1 in GSC small EVs and their effects on primary brain cultures. To this end, small EVs were isolated from patients-derived GSCs grown as neurospheres (NS) with high (V1G1^HIGH-NS) or low (V1G1^LOW-NS) V1G1 expression and analyzed for V-ATPase subunits presence, miRNA contents, and cellular responses in recipient cultures. Our results show that NS-derived small EVs stimulate proliferation and motility of recipient cells, with small EV derived from V1G1^HIGH-NS showing the most pronounced activity. This involved activation of ERK1/2 signaling, in a response reversed by V-ATPase inhibition in NS-producing small EV. The miRNA profile of V1G1^HIGH-NS-derived small EVs differed significantly from that of V1G1^LOW-NS, which included miRNAs predicted to target MAPK/ERK signaling. Mechanistically, forced expression of a MAPK-targeting pool of miRNAs in recipient cells suppressed MAPK/ERK pathway activation and blunted the prooncogenic effects of V1G1^HIGH small EV. These findings propose that the GSC influences the brain milieu through a V1G1-coordinated EVs release of MAPK/ERK-targeting miRNAs. Interfering with V-ATPase activity could prevent ERK-dependent oncogenic reprogramming of the microenvironment, potentially hampering local GBM infiltration. IMPLICATIONS: Our data identify a novel molecular mechanism of gliomagenesis specific of the GBM stem cell niche, which coordinates a V-ATPase-dependent reprogramming of the brain microenvironment through the release of specialized EVs.

The AAA + ATPase valosin-containing protein (VCP)/p97/Cdc48 interaction network in Leishmania

Valosin-containing protein (VCP)/p97/Cdc48 is an AAA + ATPase associated with many ubiquitin-dependent cellular pathways that are central to protein quality control. VCP binds various cofactors, which determine pathway selectivity and substrate processing. Here, we used co-immunoprecipitation and mass spectrometry studies coupled to in silico analyses to identify the Leishmania infantum VCP (LiVCP) interactome and to predict molecular interactions between LiVCP and its major cofactors. Our data support a largely conserved VCP protein network in Leishmania including known but also novel interaction partners. Network proteomics analysis confirmed LiVCP-cofactor interactions and provided novel insights into cofactor-specific partners and the diversity of LiVCP complexes, including the well-characterized VCP-UFD1-NPL4 complex. Gene Ontology analysis coupled with digitonin fractionation and immunofluorescence studies support cofactor subcellular compartmentalization with either cytoplasmic or organellar or vacuolar localization. Furthermore, in silico models based on 3D homology modeling and protein-protein docking indicated that the conserved binding modules of LiVCP cofactors, except for NPL4, interact with specific binding sites in the hexameric LiVCP protein, similarly to their eukaryotic orthologs. Altogether, these results allowed us to build the first VCP protein interaction network in parasitic protozoa through the identification of known and novel interacting partners potentially associated with distinct VCP complexes.

ALS/FTD mutations in UBQLN2 impede autophagy by reducing autophagosome acidification through loss of function

Mutations in UBQLN2 cause amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and other neurodegenerations. However, the mechanism by which the UBQLN2 mutations cause disease remains unclear. Alterations in proteins involved in autophagy are prominent in neuronal tissue of human ALS UBQLN2 patients and in a transgenic P497S UBQLN2 mouse model of ALS/FTD, suggesting a pathogenic link. Here, we show UBQLN2 functions in autophagy and that ALS/FTD mutant proteins compromise this function. Inactivation of UBQLN2 expression in HeLa cells reduced autophagic flux and autophagosome acidification. The defect in acidification was rescued by reexpression of wild type (WT) UBQLN2 but not by any of the five different UBQLN2 ALS/FTD mutants tested. Proteomic analysis and immunoblot studies revealed P497S mutant mice and UBQLN2 knockout HeLa and NSC34 cells have reduced expression of ATP6v1g1, a critical subunit of the vacuolar ATPase (V-ATPase) pump. Knockout of UBQLN2 expression in HeLa cells decreased turnover of ATP6v1g1, while overexpression of WT UBQLN2 increased biogenesis of ATP6v1g1 compared with P497S mutant UBQLN2 protein. In vitro interaction studies showed that ATP6v1g1 binds more strongly to WT UBQLN2 than to ALS/FTD mutant UBQLN2 proteins. Intriguingly, overexpression of ATP6v1g1 in UBQLN2 knockout HeLa cells increased autophagosome acidification, suggesting a therapeutic approach to overcome the acidification defect. Taken together, our findings suggest that UBQLN2 mutations drive pathogenesis through a dominant-negative loss-of-function mechanism in autophagy and that UBQLN2 functions as an important regulator of the expression and stability of ATP6v1g1. These findings may have important implications for devising therapies to treat UBQLN2-linked ALS/FTD.

Regulation and function of V-ATPases in physiology and disease

The vacuolar H⁺-ATPases (V-ATPases) are essential, ATP-dependent proton pumps present in a variety of eukaryotic cellular membranes. Intracellularly, V-ATPase-dependent acidification functions in such processes as membrane traffic, protein degradation, autophagy and the coupled transport of small molecules. V-ATPases at the plasma membrane of certain specialized cells function in such processes as bone resorption, sperm maturation and urinary acidification. V-ATPases also function in disease processes such as pathogen entry and cancer cell invasiveness, while defects in V-ATPase genes are associated with disorders such as osteopetrosis, renal tubular acidosis and neurodegenerative diseases. This review highlights recent advances in our understanding of V-ATPase structure, mechanism, function and regulation, with an emphasis on the signaling pathways controlling V-ATPase assembly in mammalian cells. The role of V-ATPases in cancer and other human pathologies, and the prospects for therapeutic intervention, are also discussed.

Role of V-ATPase a3-Subunit in Mouse CTL Function

CTLs release cytotoxic proteins such as granzymes and perforin through fusion of cytotoxic granules (CG) at the target cell interface, the immune synapse, to kill virus-infected and tumorigenic target cells. A characteristic feature of these granules is their acidic pH inside the granule lumen, which is required to process precursors of granzymes and perforin to their mature form. However, the role of acidic pH in CG maturation, transport, and fusion is not understood. We demonstrate in primary murine CTLs that the a3-subunit of the vacuolar-type (H⁺)-adenosine triphosphatase is required for establishing a luminal pH of 6.1 inside CG using ClopHensorN(Q69M), a newly generated CG-specific pH indicator. Knockdown of the a3-subunit resulted in a significantly reduced killing of target cells and a >50% reduction in CG fusion in total internal reflection fluorescence microscopy, which was caused by a reduced number of CG at the immune synapse. Superresolution microscopy revealed a reduced interaction of CG with the microtubule network upon a3-subunit knockdown. Finally, we find by electron and structured illumination microscopy that knockdown of the a3-subunit altered the diameter and density of individual CG, whereas the number of CG per CTL was unaffected. We conclude that the a3-subunit of the vacuolar adenosine triphosphatase is not only responsible for the acidification of CG, but also contributes to the maturation and efficient transport of the CG to the immune synapse.

Transgenic plant generated by RNAi-mediated knocking down of soybean Vma12 and soybean mosaic virus resistance evaluation

Soybean mosaic virus (SMV) is one of the most destructive viral diseases in soybean and causes severe reduction of soybean yield and destroys the seed quality. However, the production of SMV resistant plants by transgenic is the most effective and economical means. Based on our previous yeast two-hybrid assay, the GmVma12 was selected as a strong candidate gene for further function characterization. Here we transformed soybean plants with a construct containing inverted repeat of-GmVma12 sequence to analyze the role of GmVma12 during SMV invasion. Totals of 33 T₀ and 160 T₁ plants were confirmed as positive transgenic plants through herbicide application, PCR detection and LibertyLink^® strip screening. Based on the segregation ratio and Southern Blot data, T₁ lines No. 3 and No. 7 were selected to generate T₂ plants. After SMV-SC15 inoculation, 41 T₁ and 38 T₂ plants were identified as highly resistant, and their quantification disease levels were much lower than non-transformed plants. The transcript level of GmVma12 in T₂ plants decreased to 70% of non-transformed plants. The expression level of SMV-CP transcript in T₂ transgenic plants was lower than that in non-transformed plants and SMV CP protein in T₂ plants could not be detected by Enzyme-linked Immunosorbent assay, which indicated that SMV production would be inhibited in transgenic plants. Moreover, coat mottles of T₂ seeds were obliterated significantly. In conclusion, inverted repeat of the hairpin structure of GmVma12 interfered with the transcription of GmVma12, which can induce resistance to SMV in soybean. This research lays the foundation for the mechanism of SMV pathogenesis, and provides new ideas for SMV prevention and control.

Wnt signaling in cancer: therapeutic targeting of Wnt signaling beyond β-catenin and the destruction complex

Wnt/β-catenin signaling is implicated in many physiological processes, including development, tissue homeostasis, and tissue regeneration. In human cancers, Wnt/β-catenin signaling is highly activated, which has led to the development of various Wnt signaling inhibitors for cancer therapies. Nonetheless, the blockade of Wnt signaling causes side effects such as impairment of tissue homeostasis and regeneration. Recently, several studies have identified cancer-specific Wnt signaling regulators. In this review, we discuss the Wnt inhibitors currently being used in clinical trials and suggest how additional cancer-specific regulators could be utilized to treat Wnt signaling-associated cancer.

Role of endolysosomes and inter-organellar signaling in brain disease

Endosomes and lysosomes (endolysosomes) are membrane bounded organelles that play a key role in cell survival and cell death. These acidic intracellular organelles are the principal sites for intracellular hydrolytic activity required for the maintenance of cellular homeostasis. Endolysosomes are involved in the degradation of plasma membrane components, extracellular macromolecules as well as intracellular macromolecules and cellular fragments. Understanding the physiological significance and pathological relevance of endolysosomes is now complicated by relatively recent findings of physical and functional interactions between endolysosomes with other intracellular organelles including endoplasmic reticulum, mitochondria, plasma membranes, and peroxisomes. Indeed, evidence clearly indicates that endolysosome dysfunction and inter-organellar signaling occurs in different neurodegenerative diseases including Alzheimer's disease (AD), HIV-1 associated neurocognitive disease (HAND), Parkinson's disease (PD) as well as various forms of brain cancer such as glioblastoma multiforme (GBM). These findings open new areas of cell biology research focusing on understanding the physiological actions and pathophysiological consequences of inter-organellar communication. Here, we will review findings of others and us that endolysosome de-acidification and dysfunction coupled with impaired inter-organellar signaling is involved in the pathogenesis of AD, HAND, PD, and GBM. A more comprehensive appreciation of cell biology and inter-organellar signaling could lead to the development of new drugs to prevent or cure these diseases.

Cancer-associated V-ATPase induces delayed apoptosis of protumorigenic neutrophils

Tumors and neutrophils undergo an unexpected interaction, in which products released by tumor cells interact to support neutrophils that in turn support cancer growth, angiogenesis, and metastasis. A key protein that is highly expressed by cancer cells in tumors is the a2 isoform V‐ATPase (a2V). A peptide from a2V (a2NTD) is secreted specifically by cancer cells, but not normal cells, into the tumor microenvironment. This peptide reprograms neutrophils to promote angiogenesis, cancer cell invasiveness, and neutrophil recruitment. Here, we provide evidence that cancer‐associated a2V regulates the life span of protumorigenic neutrophils by influencing the intrinsic pathway of apoptosis. Immunohistochemical analysis of human cancer tissue sections collected from four different organs shows that levels of a2NTD and neutrophil counts are increased in cancer compared with normal tissues. Significant increases in neutrophil counts were present in both poorly and moderately differentiated tumors. In addition, there is a positive correlation between the number of neutrophils and a2NTD expression. Human neutrophils treated with recombinant a2NTD show significantly delayed apoptosis, and such prolonged survival was dependent on NF‐κB activation and ROS generation. Induction of antiapoptotic protein expression (Bcl‐xL and Bcl‐2A1) and decreased expression of proapoptotic proteins (Bax, Apaf‐1, caspase‐3, caspase‐6, and caspase‐7) were a hallmark of these treated neutrophils. Autocrine secretion of prosurvival cytokines of TNF‐α and IL‐8 by treated neutrophils prolongs their survival. Our findings highlight the important role of cancer‐associated a2V in regulating protumorigenic innate immunity, identifying a2V as a potential important target for cancer therapy.

Microtubules in Influenza Virus Entry and Egress

Influenza viruses are respiratory pathogens that represent a significant threat to public health, despite the large-scale implementation of vaccination programs. It is necessary to understand the detailed and complex interactions between influenza virus and its host cells in order to identify successful strategies for therapeutic intervention. During viral entry, the cellular microenvironment presents invading pathogens with a series of obstacles that must be overcome to infect permissive cells. Influenza hijacks numerous host cell proteins and associated biological pathways during its journey into the cell, responding to environmental cues in order to successfully replicate. The cellular cytoskeleton and its constituent microtubules represent a heavily exploited network during viral infection. Cytoskeletal filaments provide a dynamic scaffold for subcellular viral trafficking, as well as virus-host interactions with cellular machineries that are essential for efficient uncoating, replication, and egress. In addition, influenza virus infection results in structural changes in the microtubule network, which itself has consequences for viral replication. Microtubules, their functional roles in normal cell biology, and their exploitation by influenza viruses will be the focus of this review.