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

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

The purpose of this study was to examine the distribution of myosin isozymes in rodent (Rattus norvegicus) hindlimb skeletal muscles and regions of muscle known to have contrasting fiber-type composition. Muscle samples were analyzed for Ca2+-regulated myofibril adenosine triphosphatase (ATPase) activity, Ca2+-activated myosin ATPase activity, myosin isozyme profile, and myosin light chain profile. Four isozymes of myosin were identified based on native protein and light chain electrophoresis patterns: one associated primarily with slow-twitch muscle (SM) and three associated primarily with fast-twitch muscle (FM). Multiple linear regression analysis of Ca2+-regulated myofibril ATPase activity (pCA 4) vs. measured isozyme profile was used to estimate the myofibril ATPase activities of the individual isozymes (FM1 = 0.86, FM2 = 0.52, FM3 = 0.31, and SM = 0.15 mumol Pi formed . mg myofibril protein-1 . min-1 at 25 degrees C, n = 180, P less than 0.001). Differences in the native isozyme profiles and myofibril ATPase activities between muscles and muscle regions of similar fiber type composition indicate that a given fiber type may not necessarily express a single isozyme profile. These data are consistent with the hypothesis that, among rodent hindlimb skeletal muscles and inherently their motor units, a range of myosin isozyme profiles exists that may provide a broad range of mechanical expression.
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PMID:Myosin isozyme distribution in rodent hindlimb skeletal muscle. 294 6

An analysis of the native myosin isoenzyme composition, myosin light-chain distribution and histochemical profile of fast-twitch and slow-twitch muscles of normal and dystrophic (129 REJ dy/dy) mice has been performed, and the results correlated with the known contractile abnormalities of murine dystrophic muscles. Normal mouse slow-twitch soleus contained two isomyosins (slow myosin, SM and intermediate myosin, IM) which were electrophoretically distinct from the three major isomyosins (FM1, FM2, FM3) of fast-twitch extensor digitorum longus (e.d.l.) muscle. The calcium-activated ATPase activities of FM1, FM2, FM3 and IM at pH 9.2 were each much higher than that of SM, and this difference is reflected in the histochemical profile of muscle, as demonstrated with the myofibrillar ATPase reaction at alkaline pH. E.d.l. Type II fibres retained myofibrillar ATPase activity following pre-incubation of histochemical sections at pH 4.6, and were therefore classified Type IIB, whereas soleus Type II fibres did not, and were classified Type IIA. It was concluded that Type I (slow) fibres contain SM, Type IIA (intermediate) fibres contain IM, and Type IIB (fast) fibres contain FM1-FM3. Each electrophoretically distinct myosin contained a different combination of the five skeletal myosin light chains (LCs). Thus different normal muscles, which differed in their isomyosin profiles, differed also in their light-chain composition. Analysis of the distribution of native myosins (FM1, FM2, FM3, IM, SM, in order of decreasing gel migration rate) in dystrophic muscles revealed increased proportions of the slower-migrating forms, when compared with the distribution in the corresponding normal muscles. The shift in isomyosin distribution would explain the known decrease in the proportion of myosin light chain (LCf3) in murine dystrophic muscle. The abnormal isomyosin distribution in the dystrophic muscle is correlated with its altered histochemical characteristics, and with well-established abnormalities in its isometric and isotonic properties. It is concluded that the altered isomyosin distribution in murine dystrophic muscle would result in decreased power output per unit muscle mass when compared with normal muscle. The possibility is considered that defective myelination of the innervating nerve may contribute to these abnormalities by preventing higher frequency impulses from reaching muscle.
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PMID:Myosin isoenzymes in fast-twitch and slow-twitch muscles of normal and dystrophic mice. 622 40

The entire deletion of the cysteine string protein (CSP) gene causes a temperature-sensitive (ts) block of evoked neurotransmission in Drosophila. CSP has been found to interact in vitro with the clathrin-uncoating ATPase HSC70, suggesting a potential role of CSP in vesicle recycling. Using FM1-43 imaging, we analyzed whether the ts block of neurotransmission in csp mutants is caused by a defect in vesicle exocytosis or vesicle recycling. We determined that FM1-43-labeled synaptic boutons of csp mutant neuromuscular junctions fail to destain at 32 degrees C after K+ depolarization, and that FM1-43 dye uptake cannot be evoked by K+ stimulation at 32 degrees C. However, when we stimulated dye uptake independent of depolarization by using black widow spider venom (BWSV), we observed endocytotic uptake of FM1-43. This suggests that endocytosis exhibits no primary ts defect. In addition, we found no ts defect of vesicle recycling at 32 degrees C that would correlate with the ts block of neurotransmission. We also discovered that BWSV and the calcium ionophore calcimycin stimulate FM1-43 destaining and quantal release in csp mutants at 32 degrees C when depolarization fails to evoke any response. The wild-type-like, calcimycin-induced response in csp null mutants indicates that some aspect of the depolarization-dependent calcium signaling pathway must be impaired, either calcium entry, calcium action, or both. Collectively, our results indicate that the csp mutation affects calcium secretion coupling of evoked exocytosis but not vesicle recycling. This supports the hypothesis that CSP links synaptic vesicles to calcium secretion coupling.
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PMID:Cysteine string protein is required for calcium secretion coupling of evoked neurotransmission in drosophila but not for vesicle recycling. 943 17

The effect of aging on the in vitro contractile properties of the patagialis (PAT) muscle of 35 young adult (YA; 8 weeks of age) and 35 aged adult (AA, 110 weeks of age) Coturnix quails was examined after 0-30 days of stretch-overload. Overload was achieved by placing a weight equivalent to 12% of the birds' body weight on one wing. The contralateral wing served as the intra-animal control. Overload increased the weight of the PAT by 45.1+/-2.1% in YA, and 24.1+/-2.6% in AA. Twitch contraction time increased with loading from 43.2+/-1.2 to 67.3+/-2.2 ms in YA birds and 57.2+/-1.7 to 77.4+/-1.9 ms in AA birds. Unloaded shortening velocity (Vo) decreased by 40.1+/-2.2 and 38.8+/-3.2% in YA and aged birds, respectively. The decrease in fast myosin expression was greater in overloaded muscles of YA (20%) as compared to AA birds (12%). However, this was accompanied by a greater decrease in total muscle ATPase activity in aged birds (61%) compared to YA birds (40%). Myosin isozyme Ca(2+)-ATPase activity was 26% lower in FM1 but not other fast myosins in YA birds, but it was approximately 30% lower in all fast myosins in PAT muscles of aged birds. These data show that the reduction of Vo and the increase in twitch duration with aging may be due in part to reductions in ATPase activity in all myosin isoforms, as compared to myosin isoforms isolated from YA birds.
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PMID:Attenuation of Ca(2+)-activated ATPase and shortening velocity in hypertrophied fast twitch skeletal muscle from aged Japanese quail. 1190 84

Mitochondria-rich cells (MRCs) in the yolk-sac membrane of tilapia (Oreochromis mossambicus) larvae were examined by Na+/K(+)-ATPase immunocytochemistry and vital staining for glycoproteins following acclimation to high (7.5-7.9 mmol l(-1)), normal (0.48-0.52 mmol l(-1)) or low (0.002-0.007 mmol l(-1)) ambient Cl- levels. With a combination of concanavalin-A (Con-A)-Texas-Red conjugate staining (larvae exposed to the dye in vivo in the water) and a monoclonal antibody raised against Na+/K(+)-ATPase, MRCs were easily recognized and presumed to be active when Con-A-positive (i.e. with their apical membrane in contact with the water) or inactive when Con-A-negative. The proportion of active cells gradually increased during a 48-h acclimation to low-Cl- medium but decreased during acclimation to high-Cl- medium. Total densities of MRCs did not change when ambient chloride levels were altered. Furthermore, in live larvae exposed to changes in ambient Cl-, yolk-sac MRCs, vitally stained with DASPEI and subsequently traced in time, did not significantly alter turnover. The polymorphism of the apical membrane compartment of the MRCs represents structural modification of the active MRCs. Yolk-sac pavement cells labeled with the membrane marker FM1-43 (fluorescent lipophilic tracer) were shown to cover active MRCs in larvae transferred from normal to high ambient Cl- levels, thereby inactivating the MRCs.
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PMID:Mitochondria-rich cell activity in the yolk-sac membrane of tilapia (Oreochromis mossambicus) larvae acclimatized to different ambient chloride levels. 1501 Apr 84

We analyzed the contribution of calcium (Ca2+)-induced Ca2+ release to somatic secretion in serotonergic Retzius neurons of the leech. Somatic secretion was studied by the incorporation of fluorescent dye FM1-43 upon electrical stimulation with trains of 10 impulses and by electron microscopy. Quantification of secretion with FM1-43 was made in cultured neurons to improve optical resolution. Stimulation in the presence of FM1-43 produced a frequency-dependent number of fluorescent spots. While a 1-Hz train produced 19.5+/-5.0 spots/soma, a 10-Hz train produced 146.7+/-20.2 spots/soma. Incubation with caffeine (10 mM) to induce Ca2+ release from intracellular stores without electrical stimulation and external Ca2+, produced 168+/-21.7 spots/soma. This staining was reduced by 49% if neurons were preincubated with the Ca2+- ATPase inhibitor thapsigargin (200 nM). Moreover, in neurons stimulated at 10 Hz in the presence of ryanodine (100 microM) to block Ca2+-induced Ca2+ release, FM1-43 staining was reduced by 42%. In electron micrographs of neurons at rest or stimulated at 1 Hz in the ganglion, endoplasmic reticulum lay between clusters of dense core vesicles and the plasma membrane. In contrast, in neurons stimulated at 20 Hz, the vesicle clusters were apposed to the plasma membrane and flanked by the endoplasmic reticulum. These results suggest that Ca2+-induced Ca2+ release produces vesicle mobilization and fusion in the soma of Retzius neurons, and supports the idea that neuronal somatic secretion shares common mechanisms with secretion by excitable endocrine cells.
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PMID:Calcium-induced calcium release contributes to somatic secretion of serotonin in leech Retzius neurons. 1538 93

The V(0) complex forms the proteolipid pore of an ATPase that acidifies vesicles. In addition, an independent function in membrane fusion has been proposed largely based on yeast vacuolar fusion experiments. We have isolated mutations in the largest V(0) component vha100-1 in flies in an unbiased genetic screen for synaptic malfunction. The protein is only required in neurons, colocalizes with markers for synaptic vesicles as well as active zones, and interacts with t-SNAREs. Loss of vha100-1 leads to vesicle accumulation in synaptic terminals, suggesting a deficit in release. The amplitude of spontaneous release events and release with hypertonic stimulation indicate normal levels of neurotransmitter loading, yet mutant embryos display severe defects in evoked synaptic transmission and FM1-43 uptake. Our data suggest that Vha100-1 functions downstream of SNAREs in synaptic vesicle fusion.
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PMID:The v-ATPase V0 subunit a1 is required for a late step in synaptic vesicle exocytosis in Drosophila. 1590 59

Cardiac steroids (CS) are specific inhibitors of Na+, K+-ATPase activity. Although the presence of CS-like compounds in animal tissues has been established, their physiological role is not clear. In a previous study we showed that in pulse-chase membrane-labeling experiments, long term (hours) interaction of CS at physiological concentrations (nM) with Na+, K+-ATPase, caused changes in endocytosed membrane traffic in human NT2 cells. This was associated with the accumulation of large vesicles adjacent to the nucleus. For this sequence of events to function in the physiological setting, however, CS would be expected to modify membrane traffic upon short term (min) exposure and membrane labeling. We now demonstrate that CS affects membrane traffic also following a short exposure. This was reflected by the CS-induced accumulation of FM1-43 and transferrin in the cells, as well as by changes in their colocalization with Na+, K+-ATPase. We also show that the CS-induced changes in membrane traffic following up to 2 hrs exposure are reversible, whereas longer treatment induces irreversible effects. Based on these observations, we propose that endogenous CS-like compounds are physiological regulators of the recycling of endocytosed membrane proteins and cargo in neuronal cells, and may affect basic mechanisms such as neurotransmitter release and reuptake.
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PMID:Short-term effects of cardiac steroids on intracellular membrane traffic in neuronal NT2 cells. 1753 40

The loss of a glutamic acid residue in the AAA-ATPase (ATPases associated with diverse cellular activities) torsinA is responsible for most cases of early onset autosomal dominant primary dystonia. In this study, we found that snapin, which binds SNAP-25 (synaptosome-associated protein of 25,000 Da) and enhances the association of the SNARE complex with synaptotagmin, is an interacting partner for both wild type and mutant torsinA. Snapin co-localized with endogenous torsinA on dense core granules in PC12 cells and was recruited to perinuclear inclusions containing mutant DeltaE-torsinA in neuroblastoma SH-SY5Y cells. In view of these observations, synaptic vesicle recycling was analyzed using the lipophilic dye FM1-43 and an antibody directed against an intravesicular epitope of synaptotagmin I. We found that overexpression of wild type torsinA negatively affects synaptic vesicle endocytosis. Conversely, overexpression of DeltaE-torsinA in neuroblastoma cells increases FM1-43 uptake. Knockdown of snapin and/or torsinA using small interfering RNAs had a similar inhibitory effect on the exo-endocytic process. In addition, down-regulation of torsinA causes the persistence of synaptotagmin I on the plasma membrane, which closely resembles the effect observed by the overexpression of the DeltaE-torsinA mutant. Altogether, these findings suggest that torsinA plays a role together with snapin in regulated exocytosis and that DeltaE-torsinA exerts its pathological effects through a loss of function mechanism. This may affect neuronal uptake of neurotransmitters, such as dopamine, playing a role in the development of dystonic movements.
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PMID:The dystonia-associated protein torsinA modulates synaptic vesicle recycling. 1816 55

Ouabain is a cardiotonic glycoside that inhibits the sodium potassium ATPase pump leading to sodium accumulation in nerve terminals. At the frog neuromuscular junction, ouabain induces acetylcholine release and a rapid depletion of synaptic vesicles. In the present work, we used FM1-43 vital labeling to dissect the effect of ouabain on synaptic vesicles recycling. We first examined images of nerve-muscle preparations that were stained with FM1-43 by electrical stimulation of the nerve and destained with ouabain. We observed that ouabain induced exocytosis of synaptic vesicles independently of extracellular calcium, implying a mechanism of exocytosis that can bypass the requirement for extracellular calcium. We therefore tested the hypothesis that ouabain induces exocytosis by mobilizing intracellular calcium and we report that calcium release from endoplasmic reticulum through ryanodine receptors is necessary for ouabain-evoked exocytosis. In addition, the ouabain-evoked exocytosis was dependent on calcium released from mitochondria. We also investigated if exocytosis evoked by ouabain is followed by compensatory endocytosis. We observed that muscles incubated with FM1-43 in the presence of ouabain did not present significant staining. In conclusion, our data demonstrate that exocytosis evoked by ouabain is independent on extracellular calcium but dependent on calcium release from endoplasmic reticulum and mitochondrial stores. In addition, we suggest that ouabain can be used as a pharmacological tool to uncouple synaptic vesicles exocytosis from endocytosis at the neuromuscular junction.
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PMID:Ouabain evokes exocytosis dependent on ryanodine and mitochondrial calcium stores that is not followed by compensatory endocytosis at the neuromuscular junction. 1940 78


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