Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Electron microscopy cytochemistry has been used to study the cytoplasmic location of liposomes and lipid vesicles following specific antibody-dependent phagocytosis. The vesicle compositions were 94-99 mol% 'fluid' lipid (egg phosphatidylcholine or dimyristoylphosphatidylcholine at 37 degrees C or 'solid' lipid (dipalmitoylphosphatidylcholine at 37 degrees C). In some cases, 4 mol% phosphatidylserine was included in the vesicle membrane so as to vary the surface charge density. These vesicles undergo specific antibody-dependent phagocytosis by RAW264 macrophages when the lipid membranes contain 1-2 mol% dinitrophenyl lipid hapten in the presence of rabbit anti-dinitrophenyl IgG antibody. Internalized lipid vesicles can be visualized with the electron microscope when ferritin is trapped in the internal aqueous compartments prior to internalization. The lipid vesicles were demonstrated to be internal to the macrophage plasma membranes by selectively staining the plasma membranes with Ruthenium red. The cytoplasmic location of vesicles and liposomes was studied by electron microscopic staining for activities of the following enzymes: (1) acid phosphatase; (2) inorganic trimetaphosphatase; (3) adenosine triphosphatase; and (4) glucose-6-phosphatase. The first two enzymatic activities were found in association with ferritin-containing vesicles after antibody-dependent phagocytosis, showing the formation of vesicle-containing phagolysosomes. Adenosine triphosphatase and glucose-6-phosphatase were primary not associated with the vesicles, suggesting a minimal association of vesicles with plasma membrane, Golgi, endoplasmic reticulum and perinuclear cisternae. Phagosome-lysosome fusion did not appear to depend on the type of target lipid vesicle or liposome, on the 'fluidity' of the target membrane, or the presence of phosphatidylserine in the target membrane.
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PMID:Cytochemical study of liposome and lipid vesicle phagocytosis. 668 37

Procedures to isolate plasma membrane, Golgi apparatus, and endoplasmic reticulum from a single homogenate of mouse liver are described. Fractions contain low levels of contaminating membranes as determined from morphometry and analyses of marker enzymes. The method requires only 2-3 gm of liver as starting material and yields approximately 0.7, 0.7, and 0.5 mg protein/gm liver, respectively, for endoplasmic reticulum, Golgi apparatus, and plasma membrane. Golgi apparatus fractions show high levels of galactosyltransferase activity and consist of cisternal stacks and associated secretory vesicles and tubules. Endoplasmic reticulum fractions are enriched in both glucose-6-phosphatase and nicotinamide adenine dinucleotide phosphate (reduced) (NADPH)-cytochrome c reductase and contain membrane vesicles with attached ribosomes. K+-stimulated p-nitrophenyl phosphatase and (Na+K+) adenosine triphosphatase activity are enriched in the plasma membrane fraction. This fraction consists of membrane sheets, many with junctional complexes, and bile canaliculi that are representative of the total hepatocyte plasma membrane. The fractionation procedure is designed to utilize small amounts of tissue (e.g., with liver slices), to reduce the total time required for fractionation, and to permit comparisons of constituents of plasma membrane, Golgi apparatus, and endoplasmic reticulum prepared from the same starting homogenates.
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PMID:Isolation of plasma membrane, golgi apparatus, and endoplasmic reticulum fractions from single homogenates of mouse liver. 670 2

An enzyme histochemical and cytochemical study of normal dermal microvasculature showed that respiratory enzymes, lipase and non-specific esterase occurred in all vascular segments. Lysosomal enzymes were also widely distributed and acid phosphatase activity was localized in lysosomes, Golgi apparatus and small portions of endoplasmic reticulum of both endothelial cells and pericytes. Alkaline phosphatase activity, however, was confined to the arterial side and tip of the capillary loop where it occurred in vesicles along the luminal surface of the endothelium and in junctions between endothelial cells. The localization of nucleoside phosphatase activity within the endothelium varied according to substrate; with adenosine triphosphate as substrate, the reaction product occurred in vesicles distributed throughout the endothelial cells; with adenosine diphosphate it was limited to vesicles along the luminal surface; and with adenosine monophosphate, activity was mostly localized to the lateral surfaces of endothelial cells. These findings suggest functional variation between different vascular segments and between various components of the endothelium. Attempts to demonstrate a specific Na+K+ adenosine triphosphatase (transport ATPase) within the endothelium were not successful.
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PMID:Human dermal microvasculature: II. Enzyme histochemical and cytochemical study. 723 11

Bradykinin (BK) induces intracellular calcium ([Ca2+]i) release in Madin-Darby canine kidney (MDCK) cells. During long-term continuous BK exposure, cells become desensitized and fail to respond to a new BK stimulus. We used a protocol of repeated short-term BK addition and removal. MDCK cells were loaded with the Ca-indicator indo-1 and were exposed to BK (100 nmol/L) for 10 seconds, followed by BK removal. This cycle was repeated four to eight times while [Ca2+]i was continuously recorded. In a Ca-free bath, the cells gradually became completely desensitized to repeated BK stimuli. In the presence of 1 mmol/L or 10 mmol/L Cae, however, repeated addition of BK caused repeated [Ca2+]i transients with partial decrease of peak heights (327 and 436 nmol/L delta[Ca2+]i final) (partial desensitization). Repeated BK stimuli also led to partial desensitization (70% to 85%) to adenosine triphosphatase and carbachol (heterologous desensitization). BK also reduced peak thapsigargin response (70%), consistent with partial depletion of endoplasmic reticulum Ca pools. Our results show that MDCK cells maintain their sensitivity to BK during repeated short-term BK exposures. Available Ca3 plays a major role in modulating the degree of cellular responsiveness.
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PMID:Maintenance of bradykinin-induced intracellular calcium response of MDCK cells depends on extracellular calcium. 770 2

Fluorescence intensity was monitored from individual NG108-15 cells loaded with the Ca(++)-selective probe fura-2, and exposed to 2 microM methylmercury (MeHg). The initial effect of 2 microM MeHg was an elevation in intracellular Ca++ concentration ([Ca++]i), which was not blocked by lowering extracellular Ca++ (Ca++e), nifedipine (0.1 microM) or by Ni++ (1 mM). Addition of 100 microM Mn++ to Ca(++)-containing medium did not alter fluorescence intensity at either the Ca(++)-insensitive excitation wavelength of 360 nm or the Ca(++)-sensitive wavelength of 380 nm. Depolarization with K+ decreased the intensity at both wavelengths, indicating Mn++ entry. In the presence of Mn++, MeHg decreased the 380 nm, but not the 360 nm signal. Bradykinin (Bk) caused a transient increase in the fluorescence ratio, which was blocked by the endoplasmic reticulum Ca(++)-adenosine triphosphatase inhibitor thapsigargin. Pretreatment with Bk and thapsigargin reduced significantly the increase in ratio induced by MeHg from 21.9 +/- 3.4 to 6.9 +/- 1.8% of base line. Bk had no effect when applied after MeHg. Caffeine reduced the Bk-induced increase in [Ca++]i and the MeHg-induced increase in ratio from 21.9 +/- 3.4 to 9.0 +/- 2.1%. Thus, Bk, caffeine and MeHg all appear to release a common pool of intracellular calcium (Ca2+i). When applied after MeHg, Bk increased inositol 1,4,5-trisphosphate (IP3) by 305 +/- 27% compared to 270 +/- 29% in controls. Thus, MeHg did not induce Ca++ release by IP3 generation, nor did it block the effects of Bk by interfering with IP3 synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Methylmercury mobilizes Ca++ from intracellular stores sensitive to inositol 1,4,5-trisphosphate in NG108-15 cells. 789 11

The biosynthesis and assembly of the peripheral sector (V1) of the vacuolar proton-translocating adenosine triphosphatase (V-ATPase) was studied in a bovine kidney epithelial cell line. Monolayer cultures of cells were metabolically radiolabeled with Tran35S-label and the V-ATPase subsequently immunoprecipitated using a monoclonal antibody raised against the bovine brain-coated vesicle proton pump. The V-ATPase immunoprecipitated from the bovine kidney cell line has a subunit composition very similar to that of the bovine brain-coated vesicle proton pump and the V-ATPase prepared from other kidney tissues. Radiolabeling the cells for increasing times showed that the V1 or peripheral portion of the V-ATPase is assembled within 10-15 min; the intact V1V0 complex is also detectable within 10-15 min. Fractionation of the cells into cytosolic and membrane components prior to immunoprecipitation revealed that there is a significant pool of V1 in the cytosol; a similar complex is also found in bovine brain cytosol. Pulse-chase studies suggest that this cytosolic pool is not an obligate precursor for membrane-bound V1V0 and does not exchange with the membrane V1 population at later times. No qualitative differences in assembly were observed when pulse-chase studies were performed at 15 degrees C or in the presence of brefeldin A. This suggests that assembly of V1V0 is probably completed in the endoplasmic reticulum prior to distribution of the enzyme throughout the cell, with a cytosolic pool of V1 of unknown function existing in parallel with the fully assembled complex.
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PMID:Assembly of the peripheral domain of the bovine vacuolar H(+)-adenosine triphosphatase. 831 60

Calcium triggers muscle contraction and is a second messenger of hormones and growth factors that regulate metabolism, gene expression, and secretion in smooth muscle cells (SMC). SMC contain dozens of proteins that bind Ca2+ either to buffer changes in ionized calcium or to elicit a cellular response such contraction or secretion. Although there practically an infinite supply of Ca2+ in extracellular medium, SMC respond to a variety of stimuli by mobilizing Ca2+ accumulated in the sarcoplasmic reticulum (SR), where most cellular Ca2+ resides. The SR of smooth muscle resembles the endoplasmic reticulum of nonmuscle cells and accumulates Ca2+ via the sarcoendoplasmic reticulum Ca2+ adenosine triphosphatase (ATPase). Stimuli, such as angiotensin II, produce inositol 1,4,5,-trisphosphate (IP3), which regulates a Ca2+ channel of the SR. IP3 binding opens the channel and produces a "spike" in the cytoplasmic concentration of free Ca2+ ([Ca2+]i). The spike is largely due to the release of stored Ca2+ because hormonal stimulation produces similar spikes in the presence and absence of extracellular Ca2+. Ca2+ ejection from the cell, rather than reaccumulation by the SR, is responsible for rapidly decreasing [Ca2+]i from the peak level produced by the stimulus. Release of SR Ca2+ and activation of plasma membrane Ca2+ efflux mechanisms markedly decrease total cell Ca2+. Two independent Ca2+ transporters in the plasma membrane, the Na(+)-Ca2+ exchanger and the Ca2+ ATPase, actively eject Ca2+ from SMC. The Na(+)-Ca2+ exchanger is largely responsible for the acute phase of Ca2+ ejection, whereas the plasma membrane Ca2+ ATPase contributes to the sustained increase in Ca2+ efflux from stimulated SMC. Following Ca2+ release from the SR and ejection from the cell, Ca2+ enters via channels, which sustain a modest increase in [Ca2+]i and a gradual refilling of the SR. Mitochondria have an important role in intracellular Ca2+ signaling. Mitochondrial metabolism is highly responsive to transient increases in [Ca2+]i, although mitochondria are not a Ca2+ repository. Ca2+ uptake by mitochondria is driven by the highly favorable electrochemical potential difference across the inner membrane. Mitochondria actively expel Ca2+ via a H(+)-Ca2+ or Na(+)-Ca2+ exchanger. Ca2+ uptake and ejection by mitochondria contributes to temporal and spatial oscillations in [Ca2+]i. accelerated Ca2+ cycling between the Sr, cytoplasm, mitochondria, and the environment is a hallmark of cell stimulation.
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PMID:Calcium homeostasis in smooth muscle cells. 868 72

Phosphatase cytochemical activity in the normal glomerulus of the desert gerbil Meriones crassus was demonstrated using cerium ions as capturing agents. Three major enzymes have been recognized: sodium-potassium adenosine triphosphatase (Na(+)-K(+)-ATPase), alkaline phosphatase (ALPase) and acid phosphatase (ACPase). However, cytochemical staining for these markers to map their localizations and distributions reveal a high positivity of Na(+)-K(+)-ATPase. This appeared as uniform dense precipitates surrounding the glomerular basement membrane (GBM) and the plasma membranes of the epithelial and endothelial cells of the glomerular layers. Negligible ALKase reaction product being over the glomerular epithelia including the GBM. In contrast, the cytochemical profiles of ACPase was unusual, with dense reaction products extensively covering the endoplasmic reticulum at the region of Golgi apparatus products lysosomes (GERL) complex, including its cisternal and tubular elements and the lysosomal-vacuolar apparatus of the glomerular epithelial cells. All other subcellular organelles showed no activity. For Na(+)-K(+)-ATPase, the reaction product was successive when acetate buffer (as decalcifying agent, pH 5.0) was used. This reaction was still seen when a medium containing levamisole was used. Cytochemical controls for all enzymes were incubated in substrate-free media including those using levamisole as an inhibitor of ALPase. The data presented, which is reported for the first time, is not an attempt to determine the contribution of the selected phosphatases in the glomerular physiology and pathology. Such findings may, nevertheless, have functional implications in the fact that these markers may be involved in the ultrafiltration and other metabolic activities of the glomerulus at the molecular and/or cellular level. In addition to earlier morphological and recent histochemical work, the present study updates and recognizes information to be used as a baseline to which the gerbil model can now be employed to investigate the behavioural adaptations of the desert rodents.
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PMID:Presence of cerium-cytochemical reactions of glomerular phosphatases of normal gerbil Meriones crassus: an ultrastructural localization study. 917 76

The yeast Ca2+ adenosine triphosphatase Pmr1, located in medial-Golgi, has been implicated in intracellular transport of Ca2+ and Mn2+ ions. We show here that addition of Mn2+ greatly alleviates defects of pmr1 mutants in N-linked and O-linked protein glycosylation. In contrast, accurate sorting of carboxypeptidase Y (CpY) to the vacuole requires a sufficient supply of intralumenal Ca2+. Most remarkably, pmr1 mutants are also unable to degrade CpY*, a misfolded soluble endoplasmic reticulum protein, and display phenotypes similar to mutants defective in the stress response to malfolded endoplasmic reticulum proteins. Growth inhibition of pmr1 mutants on Ca2+-deficient media is overcome by expression of other Ca2+ pumps, including a SERCA-type Ca2+ adenosine triphosphatase from rabbit, or by Vps10, a sorting receptor guiding non-native luminal proteins to the vacuole. Our analysis corroborates the dual function of Pmr1 in Ca2+ and Mn2+ transport and establishes a novel role of this secretory pathway pump in endoplasmic reticulum-associated processes.
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PMID:The medial-Golgi ion pump Pmr1 supplies the yeast secretory pathway with Ca2+ and Mn2+ required for glycosylation, sorting, and endoplasmic reticulum-associated protein degradation. 957 Dec 46

Cells derived from an experimental luteinized ovarian tumor are more sensitive to GnRH endocrine action than control luteal cells. In an attempt to understand the possible causes of the differential sensibility to GnRH action, we examined the number and affinity of GnRH receptors and the second messenger response to GnRH stimulation in both tissues. For GnRH receptor studies membranes were obtained from 4- to 6-week-old ovarian tumors (luteoma) and ovaries from prepubertal rats treated with 25 IU PMSG and 25 IU hCG (SPO) and were incubated with [125I]Buserelin. The number of GnRH receptors were increased in luteoma compared with that in SPO ovaries; dissociation constants were similar in both tissues. GnRH stimulation of second messenger release was assessed in cells obtained from luteoma and SPO ovaries by collagenase treatment. Buserelin (100 ng/ml) induced a significant 35% calcium increase in SPO cells, as determined by the fura-2 method; in luteoma cells no response was observed after buserelin stimulation, although a calcium transient was induced by thapsigargin (0.5 microM), an inhibitor of Ca2+-adenosine triphosphatase associated with the endoplasmic reticulum. The effect of buserelin on inositol phosphates was evaluated after incubation of luteoma and SPO cells with [3H]myoinositol for 48 h. Buserelin induced a 400% increase in inositol trisphosphate in SPO cells. Again, luteoma cells did not respond to buserelin stimulation, although NaF (10 mM), an activator of G proteins coupled to phospholipase C, induced an 800% increase in inositol trisphosphate. Although the number of GnRH receptors is augmented in luteoma cells, justifying an increased endocrine response, neither inositol phosphates nor intracellular calcium were released by a GnRH analog, indicating the uncoupling of GnRH receptors from phospholipase C. These data provide evidence that the transformation of the ovary into a luteoma implies the acquisition of novel characteristics in the GnRH receptor second messenger-generating system.
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PMID:Alterations in intracellular messengers mobilized by gonadotropin-releasing hormone in an experimental ovarian tumor. 1043 13


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