Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Solubilization of bone mineral by osteoclasts depends on the formation of an acidic extracellular compartment through the action of a V-type ATPase. We previously cloned a gene encoding a putative osteoclast-specific proton pump subunit, termed OC-116 kDa, approved mouse Atp6i (ATPase, H+ transporting, [vacuolar proton pump] member I). The function of Atp6i as osteoclast-specific proton pump subunit was confirmed in our mouse knockout study. However, the transcription regulation of Atp6i remains largely unknown. In this study, the gene encoding mouse Atp6i and the promoter have been isolated and completely sequenced. In addition, the temporal and spatial expressions of Atp6i have been characterized. Intrachromosomal mapping studies revealed that the gene contains 20 exons and 19 introns spanning approximately 11 kilobases (kb) of genomic DNA. Alignment of the mouse Atp6i gene exon sequence and predicted amino acid sequence to that of the human reveals a strong homology at both the nucleotide (82%) and the amino acid (80%) levels. Primer extension assay indicates that there is one transcription start site at 48 base pairs (bp) upstream of the initiator Met codon. Analysis of 4 kb of the putative promoter region indicates that this gene lacks canonical TATA and CAAT boxes and contains multiple putative transcription regulatory elements. Northern blot analysis of RNAs from a number of mouse tissues reveals that Atp6i is expressed predominantly in osteoclasts, and this predominant expression was confirmed by reverse-transcription polymerase chain reaction (RT-PCR) assay and immunohistochemical analysis. Whole-mount in situ hybridization shows that Atp6i expression is detected initially in the headfold region and posterior region in the somite stage of mouse embryonic development (E8.5) and becomes progressively restricted to anterior regions and the limb bud by E9.5. The expression level of Atp6i is largely reduced after E10.5. This is the first report of the characterizations of Atp6i gene, its promoter, and its gene expression patterns during mouse development. This study may provide valuable insights into the function of Atp6i, its osteoclast-selective expression, regulation, and the molecular mechanisms responsible for osteoclast activation.
...
PMID:Characterization of mouse Atp6i gene, the gene promoter, and the gene expression. 1139 91

The 116-kDa a-subunit of the vacuolar proton pump (H(+)-ATPase) exists as several isoforms encoded by different genes and with different patterns of tissue expression. Its function within the multisubunit pump complex has yet to be elucidated. To date, three isoforms have been identified in mouse (designated a1-a3). We now report the cloning and characterization of Atp6n1b, encoding a novel fourth murine isoform (a4). Murine a4 has 833 residues and shows 85% amino acid identity to the human kidney-specific ATP6N1B protein in which loss-of-function alterations cause autosomal recessive distal renal tubular acidosis. The human and murine genes have similar genomic organization; furthermore, Atp6n1b maps to a region of mouse chromosome 6 that is syntenic with the segment of human 7q33-34 containing ATP6N1B. Together these findings establish the two genes as orthologs. The mouse a4 protein is 61, 52, and 47% identical to a1, a2, and a3, respectively. Phylogenetic analysis confirms that among vertebrates there are four a-subunit families, with a4 most resembling a1. Northern blot analysis of Atp6n1b reveals a 3.7-kilobase a4 transcript in kidney but not other major organs, and a reverse transcription polymerase chain reaction in 12 mouse tissues detects expression in kidney alone. Immunofluorescence studies in murine kidney demonstrate high intensity a4 staining at the surface of intercalated cells, with additional expression in the proximal tubule (not previously reported in human kidney). Similar apical a4 immunostaining is also present in male genital tissue. Identification of this novel murine kidney-enriched 116-kDa a-subunit provides a molecular tool for investigation of the currently unknown role of this protein, which is essential for proper function of the apical renal vacuolar H(+)-ATPase in man.
...
PMID:Molecular cloning and characterization of Atp6n1b: a novel fourth murine vacuolar H+-ATPase a-subunit gene. 1149 28

The lysosomal system is the main intracellular mechanism for the turnover of endogenous and exogenous macromolecules. This catabolism is brought about in the lumen of lysosomes by a cocktail of predominantly hydrolytic enzymes with characteristic acidic pH-optima. The lysosomal membrane, which has a typical single phospholipid bilayer, controls the passage of material into and out of lysosomes, by its permeability and ability to fuse with digestive vacuoles or engulf cytosolic material. About 20 systems for transporting small molecules across the lysosomal membrane have been characterized but only two proteins, cystinosin and sialin, involved in the transport of cystine and sialic acid, respectively, have been cloned. A distinct, vacuolar proton pump (V-type H+ ATPase), which maintains the low luminal pH, has been characterized. Ubiquitous, highly glycosylated, integral membrane proteins of largely unknown function, called lysosome-associated membrane proteins (LAMPS) or lysosomal integral membrane proteins (LIMPS), account for about 50% of the protein in the lysosomal membrane. They have a short cytosolic domain of 10-20 amino acids containing single tyrosine or di-leucine motifs, which interact with adaptor complexes (APS) for sorting at the trans-Golgi network and targeting to lysosomes. A deficiency of LAMP-2 is the primary defect in Danon disease. Other proteins associate with the membrane transiently or cell-specifically. The structure, function and intracellular transport of these different classes of lysosomal membrane proteins will be reviewed.
...
PMID:Lysosomal membrane proteins. 1158 80

The plant vacuolar proton pump can be subjected to reversible redox regulation in vitro. The redox-dependent activity change involves disulfide bridge formation not only in Vatp A, as reported for bovine V-ATPase, but also in the stalk subunit Vatp E. Microsomal membranes isolated from barley leaves were analysed for their activity of bafilomycin-sensitive ATP hydrolysis and proton pumping using quinacrine fluorescence quenching in vesicle preparations. ATP hydrolysis and proton pumping activity were inhibited by H2O2. H2O2-deactivated ATPase was reactivated by cysteine and glutathione. The glutathione concentration needed for half maximal reactivation was 1 mmol l-1. The activity loss was accompanied by shifts in electrophoretic mobility of Vatp A and E which were reversed upon reductive reactivation. The redox-dependent shift was also seen with recombinant Vatp E, and was absent following site-directed mutagenesis of either of the two cys residues conserved throughout all plant Vatp E sequences. V-ATPase was also inhibited by oxidized thioredoxin. These results support the hypothesis that tuning of vacuolar ATPase activity can be mediated by redox control depending on the metabolic requirements.
...
PMID:Reversible redox control of plant vacuolar H+-ATPase activity is related to disulfide bridge formation in subunit E as well as subunit A. 1169 86

The vacuolar proton pump (V-ATPase) appears to be essential for viability of Dictyostelium cells. To investigate the function of VatM, the 100 kDa transmembrane V-ATPase subunit, we altered its level. By means of homologous recombination, the promoter for the chromosomal vatM gene was replaced with the promoter for the act6 gene, yielding the mutant strain VatMpr. The act6 promoter is much more active in cells growing axenically than on bacteria. Thus, transformants were selected under axenic growth conditions, then shifted to bacteria to determine the consequences of reduced vatM expression. When VatMpr cells were grown on bacteria, the level of the 100 kDa V-ATPase subunit dropped, cell growth slowed, and the A subunit, a component of the peripheral catalytic domain of the V-ATPase, became mislocalized. These defects were complemented by transformation of the mutant cells with a plasmid expressing vatM under the control of its own promoter. Although the principal locus of vacuolar proton pumps in Dictyostelium is membranes of the contractile vacuole system, mutant cells did not manifest osmoregulatory defects. However, bacterially grown VatMpr cells did exhibit substantially reduced rates of phagocytosis and a prolonged endosomal transit time. In addition, mutant cells manifested alterations in the dynamic regulation of cytosolic pH that are characteristic of normal cells grown in acid media, which suggested that the V-ATPase also plays a role in cytosolic pH regulation.
...
PMID:Altered expression of the 100 kDa subunit of the Dictyostelium vacuolar proton pump impairs enzyme assembly, endocytic function and cytosolic pH regulation. 1195 22

Trapping of weak bases was utilized to evaluate stimulus-induced changes in the internal pH of the secretory vesicles of chromaffin cells and enteric neurons. The internal acidity of chromaffin vesicles was increased by the nicotinic agonist 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP; in vivo and in vitro) and by high K+ (in vitro); and in enteric nerve terminals by exposure to veratridine or a plasmalemmal [Ca2+]o receptor agonist (Gd3+). Stimulation-induced acidification of chromaffin vesicles was [Ca2+]o-dependent and blocked by agents that inhibit the vacuolar proton pump (vH+-ATPase) or flux through Cl- channels. Stimulation also increased the average volume of chromaffin vesicles and the proportion that displayed a clear halo around their dense cores (called active vesicles). Stimulation-induced increases in internal acidity and size were greatest in active vesicles. Stimulation of chromaffin cells in the presence of a plasma membrane marker revealed that membrane was internalized in endosomes but not in chromaffin vesicles. The stable expression of botulinum toxin E to prevent exocytosis did not affect the stimulation-induced acidification of the secretory vesicles of mouse neuroblastoma Neuro2A cells. Stimulation-induced acidification thus occurs independently of exocytosis. The quantal size of secreted catecholamines, measured by amperometry in cultured chromaffin cells, was found to be increased either by prior exposure to L-DOPA or stimulation by high K+, and decreased by inhibition of vH+-ATPase or flux through Cl- channels. These observations are consistent with the hypothesis that the content of releasable small molecules in secretory vesicles is increased when the driving force for their uptake is enhanced, either by increasing the transmembrane concentration or pH gradients.
...
PMID:Stimulation-dependent regulation of the pH, volume and quantal size of bovine and rodent secretory vesicles. 1212 45

The inhibitor sensitivity of the endoplasmic reticulum (ER) and plasma membrane (PM) calcium pumps of red beet (Beta vulgaris L.) were studied by measuring the ATP-driven accumulation of 45Ca2+ into isolated membrane vesicles. Both transporters were strongly inhibited by 50 [mu]mol m-3 erythrosin B, but only by 50% in the presence of 100 mmol m-3 vanadate. A number of inhibitors considered to be specific for the sarcoplasmic reticulum (SR)/ER-type calcium pump in animal cells were used to further characterize the PM and ER Ca2+-ATPases in red beet and were compared with their effect on the transport and hydrolytic activities of the PM and tonoplast H+-ATPases. The hydroquinones 2,5-di(tert-butyl)-1,4-benzohydroquinone and 2,5-di(tert-amyl)-1,4-benzohydroquinone produced around 20 and 40% inhibition of activity, respectively, of the PM and ER calcium pumps and the PM H+-ATPase when present at concentrations of 30 mmol m-3. In contrast, the vacuolar proton pump displayed a much higher sensitivity to these two compounds. Nonylphenol appeared to have a general inhibitory effect on all four membrane transport proteins and gave almost complete inhibition when present at a concentration of 100 mmol m-3. Thapsigargin and the structurally related compound trilobolide produced 50% inhibition of both the ER and PM calcium pumps at concentrations of 12.5 and 24 mmol m-3, respectively. The PM and tonoplast proton pumps were also sensitive to these compounds. The ER and PM calcium pumps were almost completely insensitive to cyclopiazonic acid (CPA) up to a concentration of 20 mmol m-3. When present at 100 mmol m-3 CPA caused 30% inhibition of the transport properties of all four ATPases. The high concentrations of all of the inhibitors of the SR/ER Ca-ATPase required to inhibit the red beet ER calcium pump, together with the similar effects on the PM calcium pump and the PM and tonoplast proton pumps, suggests that these hydrophobic compounds have a general nonselective action in red beet, possibly through disruption of membrane lipid-protein interactions.
...
PMID:A Study of the Effect of Inhibitors of the Animal Sarcoplasmic/Endoplasmic Reticulum-Type Calcium Pumps on the Primary Ca2+-ATPases of Red Beet. 1223 68

The electroneutral sodium bicarbonate cotransporter 3 (NBC3) coimmunoprecipitates from renal lysates with the vacuolar H(+)-ATPase. In renal type A and B intercalated cells, NBC3 colocalizes with the vacuolar H(+)-ATPase. The involvement of the COOH termini of NBC3 and the 56-kDa subunit of the proton pump in the interaction of these proteins was investigated. The intact and modified COOH termini of NBC3 and the 56-kDa subunit of the proton pump were synthesized, coupled to Sepharose beads, and used to pull down kidney membrane proteins. Both the 56- and the 70-kDa subunits of the proton pump, as well as a PDZ domain containing protein Na(+)/H(+) exchanger regulatory factor 1 (NHERF-1), were bound to the intact 18 amino acid NBC3 COOH terminus. A peptide truncated by five COOH-terminal amino acids did not bind these proteins. Replacement of the COOH-terminal leucine with glycine blocked binding of both the proton pump subunits but did not affect binding of NHERF-1. The 18 amino acid COOH terminus of the 56-kDa subunit of the proton pump bound NHERF-1 and NBC3, but the truncated and modified peptide did not. A complex of NBC3, the 56-kDa subunit of the proton pump, and NHERF-1 was identified in rat kidney. The data indicate that the COOH termini of NBC3 and the 56-kDa subunit of the vacuolar proton pump are PDZ-interacting motifs that are necessary for the interaction of these proteins. NHERF-1 is involved in the interaction of NBC3 and the vacuolar proton pump.
...
PMID:The COOH termini of NBC3 and the 56-kDa H+-ATPase subunit are PDZ motifs involved in their interaction. 1244 18

The rare bone thickening disease osteopetrosis occurs in various forms, one of which is accompanied by renal tubular acidosis (RTA), and is known as Guibaud-Vainsel syndrome or marble brain disease. Clinical manifestations of this autosomal recessive syndrome comprise increased bone density, growth failure, intracerebral calcification, facial dysmorphism, mental retardation, and conductive hearing impairment. The most common cause is carbonic anhydrase II (CAII) deficiency. Several different loss of function mutations in CA2, the gene encoding CAII, have been described. To date, there have been no exceptions to the finding of CAII deficiency in patients with coexistent osteopetrosis and RTA. Most often, the RTA is of mixed proximal and distal type, but kindreds are reported in which either distal or proximal RTA predominates. We report the molecular genetic investigation of two consanguineous kindreds where osteopetrosis and distal RTA (dRTA) were both manifest. One kindred harbours a novel homozygous frameshift alteration in CA2. In the other, CAII levels were normal despite a similar clinical picture, and we excluded defects in CA2. In this kindred, two separate recessive disorders are penetrant, each affecting a different, tissue specific subunit of the vacuolar proton pump (H(+)-ATPase), providing a highly unusual, novel genetic explanation for the coexistence of osteopetrosis and dRTA. The osteopetrosis is the result of a homozygous deletion in TCIRG1, which encodes an osteoclast specific isoform of subunit a of the H(+)-ATPase, while the dRTA is associated with a homozygous mutation in ATP6V1B1, encoding the kidney specific B1 subunit of H(+)-ATPase. This kindred is exceptional firstly because the coinheritance of two rare recessive disorders has created a phenocopy of CAII deficiency, and secondly because these disorders affect two different subunits of the H(+)-ATPase that have opposite effects on bone density, but which have only recently been determined to possess tissue specific isoforms.
...
PMID:A phenocopy of CAII deficiency: a novel genetic explanation for inherited infantile osteopetrosis with distal renal tubular acidosis. 1256 20

Murine coronavirus mouse hepatitis virus (MHV) causes demyelination of the central nervous system (CNS) in rats and mice. Apoptotic oligodendrocytes have been detected in the vicinity of the CNS demyelinating lesions in these animals. However, whether MHV can directly induce oligodendrocyte apoptosis has not been documented. Here, we established a rat oligodendrocyte culture that is morphologically and phenotypically indistinguishable from the primary rat oligodendrocytes. Using this culture, we showed that mature rat oligodendrocytes were permissive to MHV infection but did not support productive virus replication. Significantly, oligodendrocytes infected with both live and ultraviolet light-inactivated viruses underwent apoptosis to a similar extent, which was readily detectable at 24 h postinfection as revealed by apoptotic bodies and DNA fragmentation, indicating that MHV-induced apoptosis is mediated during the early stages of the virus life cycle and does not require virus replication. Prior treatment of cells with the lysosomotropic agents NH(4)Cl and chloroquine as well as the vacuolar proton pump-ATPase inhibitor bafilomycin A1, all of which block the acidification of the endosome, prevented oligodendrocytes from succumbing to apoptosis induced by MHV mutant OBLV60, which enters cells via endocytosis, indicating that fusion between the viral envelope and cell membranes triggers the apoptotic cascade. Treatment with the pan-caspase inhibitor Z-VAD-fmk blocked MHV-induced apoptosis, suggesting an involvement of the caspase-dependent pathway. Our results, thus, for the first time provide unequivocal evidence that infection of oligodendrocytes with MHV directly results in apoptosis. This finding provides an explanation for the destruction of oligodendrocytes and the damage of myelin sheath in MHV-infected CNS and suggests that oligodendrocyte apoptosis may be one of the underlying mechanisms for the pathogenesis of MHV-induced demyelinating diseases in animals.
...
PMID:Induction of caspase-dependent apoptosis in cultured rat oligodendrocytes by murine coronavirus is mediated during cell entry and does not require virus replication. 1458 32


<< Previous 1 2 3 4 5 6 Next >>

---