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At least 19 recordsLinked to original sources
PubMed2001

Vesicular trafficking machinery, the actin cytoskeleton, and H+-K+-ATPase recycling in the gastric parietal cell.

Gastric HCl secretion by the parietal cell involves the secretagogue-regulated re-cycling of the H+-K+-ATPase at the apical membrane. The trafficking of the H+-K+-ATPase and the remodelling of the apical membrane during this process are likely to involve the co-ordination of the function of vesicular trafficking machinery and the cytoskeleton. This review summarizes the progress made in the identification and characterization of components of the vesicular trafficking machinery that are associated with the H+-K+-ATPase and of components of the actin-based cytoskeleton that are associated with the apical membrane of the parietal cell. Since many of these proteins are also expressed at the apical pole of other epithelial cells, the parietal cell may represent a model system to characterize the protein- protein interactions that regulate apical membrane trafficking in many other epithelial cells.

Actins↗
PubMed2002

Helicobacter pylori induces apoptosis of rat gastric parietal cells.

Gastric Helicobacter pylori infection may lead to multifocal atrophic corpus gastritis associated with loss of epithelial cells as well as glandular structures. The current work investigated H. pylori effects on cell death of isolated, nontransformed rat parietal cells (PC). Highly enriched rat PC (>97%) were isolated from gastric mucosa and cultured in serum-free medium over 24 h. The cells were cocultured over 8 h with cytotoxin-associated immunodominant protein (cagA)(+)/vacuolating toxin (vacA)(+) or with cagA(-)/vacA(-) H. pylori laboratory strains and also with H. pylori mutants deleted in several genes of the cag pathogenicity island. Staphylococcus aureus or Campylobacter jejuni were used as controls. Apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and electron microscopy. Interleukin (IL)-8 and cytokine-induced neutrophil chemoattractant (CINC)-1 secretion was measured by ELISA. Activation of nuclear factor-kappaB (NF-kappaB) was studied in nuclear extracts of PC by electrophoretic mobility shift assay. Apoptosis of PC was induced in a concentration- and time-dependent manner by cagA(+)/vacA(+) H. pylori strains but not by cagA(-)/vacA(-) negative strains or by the cagE knockout mutant. S. aureus and C. jejuni had no effect. PC showed no IL-8 or CINC-1 secretion on exposure to cagA(+)/vacA(+) H. pylori. cagA(+)/vacA(+) strains induced activation of NF-kappaB complexes in nuclear extracts of PC, which were composed of p65 and p50 subunits. No significant stimulation of NF-kappaB activation was detected by incubation of PC with the cagE knockout mutant. Preincubation of PC with antisense but not missense oligodeoxynucleotides against the p65 subunit significantly reduced DNA binding to the kappaB recognition sequence. The p65 oligonucleotides as well as the proteasome inhibitor N-CBZ-isoleucin-glutamin-(o-t-butyl-)-alanin-leucin and the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine completely prevented PC apoptosis induced by cagA(+)/vacA(+) strains. In summary, cagE presence appears to be essential for H. pylori-induced apoptosis of gastric parietal cells, and this effect is dependent on the activation of NF-kappaB and production of nitric oxide.

Animals↗
PubMed1994

A basolateral CHIP28/MIP26-related protein (BLIP) in kidney principal cells and gastric parietal cells.

The water channel CHIP28 accounts for the high water permeability of proximal tubules and thin descending limbs of Henle; a homologous water channel, WCH-CD, in the apical membrane of collecting duct principal cells, may be the vasopressin-sensitive water channel. We show here that one antiserum, raised against CHIP28, immunostains the basolateral membrane of collecting duct principal cells, in addition to staining CHIP28 in other cells. This serum was named anti-basolateral integral protein (anti-BLIP) to distinguish it from other anti-CHIP28 antisera. By Western blotting, BLIP serum recognized both CHIP28 and MIP26, and it stained lens fibers, which contain MIP26 but not CHIP28. BLIP antiserum immunoprecipitated a 28-kDa band, a broad 35- to 50-kDa band, and an approximately 16-kDa band from kidney papilla. It also stained the basolateral membrane of gastric parietal cells, which were not stained with anti-CHIP28 or anti-MIP26 antibodies. BLIP antiserum immunoprecipitated a 28-kDa protein band from stomach; this protein was not precipitated by anti-CHIP28 antibodies. These results suggest that basolateral membranes of principal cells and parietal cells contain a protein(s) that shares common epitopes with CHIP28 and MIP26. Finally, BLIP but not CHIP28 antiserum stained mesothelial (but not epithelial) cells of toad urinary bladder, a further indication that the BLIP antiserum recognizes a protein distinct from CHIP28.

Animals↗
PubMedDate not supplied

Calcium signaling mechanisms in the gastric parietal cell.

Gastric hydrochloric acid (HCl) secretion is stimulated in vivo by histamine, acetylcholine, and gastrin. In vitro studies have shown that histamine acts mainly via a cAMP-dependent pathway, and acetylcholine acts via a calcium-dependent pathway. Histamine also elevates intracellular calcium ([Ca2+]i) in parietal cells. Both gastrin and acetylcholine release histamine from histamine-containing cells. In humans, rats, and rabbits, there is considerable controversy as to whether or not gastrin receptors are also present on the parietal cell. We utilized digitized video image analysis techniques in this study to demonstrate gastrin-induced changes in intracellular calcium in single parietal cells from rabbit in primary culture. Gastrin also stimulated a small increase in [14C]-aminopyrine (AP) accumulation, an index of acid secretory responsiveness in cultured parietal cells. In contrast to histamine and the cholinergic agonist, carbachol, stimulation of parietal cells with gastrin led to rapid loss of the calcium signaling response, an event that is presumed to be closely related to gastrin receptor activation. Moreover, different calcium signaling patterns were observed for histamine, carbachol, and gastrin, Previous observations coupled with present studies using manganese, caffeine, and ryanodine suggest that agonist-stimulated increases in calcium influx into parietal cells do not occur via voltage-sensitive calcium channels or nonspecific divalent cation channels. It also appears to be unlikely that release of intracellular calcium is mediated by a muscle or neuronal-type ryanodine receptor. We hypothesize that calcium influx may be mediated by either a calcium exchange mechanism or by an unidentified calcium channel subtype that possesses different molecular characteristics as compared to muscle, nerve, and certain secretory cell types such as, for example, the adrenal chromaffin cell. Release of intracellular calcium may be mediated via both InsP3-sensitive and -insensitive mechanisms. The InsP3-insensitive calcium pools, if present, do not appear, however, to possess ryanodine receptors capable of modulating calcium efflux from these storage sites.

Aminopyrine↗
PubMed1993

Ezrin-calpain I interactions in gastric parietal cells.

Gastric ezrin, a membrane-cytoskeletal linker with sequence homology to talin and erythrocyte band 4.1, has been associated with the remodeling of parietal cell apical membrane that occurs with adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase stimulation. Here we examine the interrelationship between parietal cell ezrin and Ca(2+)-dependent protease activity. Addition of Ca2+ to sonicated gastric gland preparations rendered a relatively selective proteolysis of the 80-kDa ezrin, accompanied by the appearance of a 55-kDa breakdown product. Ca(2+)-dependent proteolysis of ezrin was blocked by E64, a cysteine protease inhibitor, or calpastatin, indicating calpain as the responsible protease. Degradation of ezrin in intact gastric glands was achieved by varying extracellular [Ca2+] and [ionomycin]. Ezrin degradation in situ was rapid and relatively selective, although Ca(2+)-dependent degradation of some spectrin-like bands was also observed. The effect of activated calpain I on parietal cell function was assessed by probing the secretory response to histamine stimulation using [14C]aminopyrine uptake, along with parallel measurements of calpain activity, over a wide range of ionomycin. Activation of calpain, as evidenced by loss of parietal cell ezrin, was correlated with decreased AP uptake by stimulated gastric glands, supporting a role for ezrin in the oxyntic secretory process. The calpain-ezrin interaction established here, and the similarities of calpain with talin and erythrocyte band 4.1, suggest a common feature to this family of ezrin/band 4.1/talin proteins that have been implicated in membrane-cytoskeletal association.

Animals↗
PubMed1981

Histamine regulation of adenylyl cyclase of enriched rat gastric parietal cells.

Rat gastric parietal cells were isolated to 90% or greater purity by discontinuous gradient ultracentrifugation in sucrose-Ficoll. Adenylyl cyclase activity was initiated by histamine in the presence of 5'-guanylyl imidodiphosphate, but not by pentagastrin or acetylcholine. The concentration of histamine needed for half-maximal activation of adenylyl cyclase was 38 microM. The histamine H2-receptor antagonist, metiamide, inhibited histamine (100 microM) activation with a Ki of 0.9 microM. The effects of other histamine agonists and antagonists suggest that presence of H2-type histaminic receptors on parietal cells. Adenylyl cyclase activity was also stimulated by isoproterenol, norepinephrine, and epinephrine, but not by methoxamine. Half-maximal activation by isoproterenol occurred at 0.5 microM. Propranolol, but not phentolamine, prevented activation by these agents, indicating the presence of beta-adrenergic receptors on parietal cells. Prostaglandins E2 stimulated adenylyl cyclase of partially purified (30%), but not the enriched (90%), parietal cell populations.

Adenylyl Cyclases↗
PubMed1990

HCl secretion and [Ca2+]i in cultured parietal cells.

Gastric parietal cells in primary culture have been tested to determine their utility as a model for the study of the role of intracellular calcium ([Ca2+]i) in the control of HCl secretion. Changes in [Ca2+]i were measured in single cells on a microscope stage using the cell-permeant form of the fluorescent calcium probe, fura-2. Simultaneous images of cell fluorescence and morphology were acquired using a digitized video image analysis system and two video cameras, one for low-light level fluorescence detection and one for high resolution DIC/transmitted light images. Both histamine and carbachol, which are known stimulants of HCl secretion, increased [Ca2+]i and stimulated dramatic changes in morphology in these cultured cells. Changes in morphology were accompanied by an increased uptake of the weak base, [14C]-aminopyrine (AP), and a shift from green to red fluorescence of another weak base, acridine orange. These results indicate that cultured parietal cells, maintained under controlled conditions on a microscope stage, retain viability and secretagogue responsiveness. Thus, this cellular model appears to be suitable for correlation of changes in [Ca2+]i and activation of HCl secretion.

Animals↗
PubMed2000

Morphological studies on the translocation of tubulovesicular system toward the intracellular canaliculus during stimulation of the gastric parietal cell.

The gastric parietal has two characteristic membrane systems. One is the intracellular canaliculus, which is specialized networks of enfolded luminal membrane channels lined with numerous microvilli. The other structures common to all parietal cells are the tubulovesicles or the tubulovesicular membranes, a system of tubules and vesicles. The tubulovesicular compartment is drastically depleted during maximal gastric acid secretion and this is coincident with an increase in the canalicular cell surface membrane. A plausible explanation for this redistribution is the fusion and transfer of tubulovesicular membranes to the plasma membrane. However, for many years there was no convincing evidence of connections between these two membrane systems. The mechanism of the transformation of tubulovesicular membrane into the plasma membrane without demonstrable connections has been an enigma to electron microscopists. Using a recently developed fixation technique for parietal cells [Sugai et al. (1995) Acta Anat Nippon 74:S101], we have investigated the organization of the cytoplasmic membrane systems in the rat resting and tetragastrin stimulated stomachs by ultra-high-resolution scanning electron microscopy (SEM). Gastric mucosae were microwave-fixed in a cacodylate buffer, (334 milliosmoles/kgH(2)O (mOsm)), to which 1.0% glutaraldehyde and 0.5% formaldehyde were added. Specimens examined by TEM of thin sections revealed the cytoplasm packed with tubular membranes similar to images detected by rapid-freeze/freeze-substitution fixation. To render the cytoplasmic membranes visible by SEM, fixed mucosae were treated by the aldehyde-osmium-DMSO-osmium maceration procedure. With much of the cell matrix and filaments removed, SEM revealed numerous 30-60-nm tubules, which formed a meshwork with small cisternae. Vesicles or isolated tubules were not found in adequately macerated parietal cells. The cytoplasmic surface of the intracellular canaliculus was smooth except for round openings representing the bases of macerated microvilli. In favorable sites, connections of the tubular membranes to the canaliculi were clearly visible. Stereo pair views were particularly useful to demonstrate these continuities. Connections between these two membrane compartments suggest the probability of rapid membrane transposition. In this article, the form and distribution of membrane systems of parietal cells in the resting state and after tetragastrin stimulation will be presented and discussed. Special emphasis is made to demonstrate connections between the tubulovesicular system and the intracellular canaliculus.

Animals↗
PubMed1993

Diversity of cell-cell interactions formed by gastric parietal cells in culture: morphological study on guinea pig cells.

Parietal cells of gastric glands are specialized to produce acid. Tight junctions between the parietal cells and their neighbouring cells (usually chief cells and mucous cells, less commonly parietal cells) avoid acid back-diffusion. Alterations of these junctions are accompanied by a defective epithelial barrier function. The conditions leading to junction formation, e.g. during epithelial restitution and regeneration are entirely unknown. The present study has the purpose to establish an in vitro model which allows studying these junctions. Freshly isolated gastric epithelial cells of guinea pig, moderately enriched with parietal cells, were cocultured for 2 days. Highly specific staining techniques showed the following composition in the near-confluent monolayer: 45% parietal cells (succinic dehydrogenase-positive), 36% mucous cells (lectin-binding granules), 18% chief cells (pepsinogen-positive granules) and 1% subepithelial cells (vimentin-positive). Ultrastructural investigations of sections of these monolayers revealed a high tendency of parietal cells to form cell junctions with the following characteristics: 1) virtually all parietal cells formed junctions with their neighbouring cells; 2) only junctions, but no desmosomes, were observed among neighbouring parietal cells; 3) junctional complexes and desmosomes were regularly present between parietal cells and their neighbouring mucous and chief cells; 4) parietal cells were sometimes integrated into three-dimensional structures, resembling rudimentary gastric glands. In conclusion, parietal cells under standard coculture conditions, generate de novo the same types of cell junctions that are observed in the intact gastric epithelium. The results show that parietal cells in vitro spontaneously make junctions with parietal and non-parietal cells, resembling the junctions in the intact tissue.

Animals↗
PubMed1980

Gastric parietal cell antibodies: demonstration by immunofluorescence of their reactivity with surface of the gastric parietal cells.

Viable, intact gastric cells were obtained by pronase digestion of inverted rat stomach. The cell suspensions contained two main distinct cell population, i.e. 'large' cells (mean diameter 16 microns) and 'small' cells (mean diameter 8.5 microns). By indirect immunofluorescence on smears of dispersed rat gastric cells, the large cells were identified as parietal cells, since all the sera containing parietal cell antibodies (PCA) were seen to react with the cytoplasm of these cells, leaving the cytoplasm of the small cells completely unstained. Thirty-one PCA-positive sera and forty-one PCA-negative sera were tested for gastric cell surface-reactive antibodies by an indirect immunofluorescence technique on suspensions of viable gastric cells. All the PCA-containing sera yielded a membrane immunofluorescence confined to the large cells, while none of the PCA-negative sera induced this fluorescent pattern. The surface reaction persisted unmodified when F(ab')2 fragments processed from IgG PCA-positive sera and FITC-conjugated pepsin fragments of rabbit IgG directed against the F(ab')2 fragments of human IgG were employed for the membrane fluorescence studies. The absorption of PCA-positive sera with viable, intact gastric cells led to the disappearance of both the surface immunofluorescence of the viable large cells and the cytoplasmic fluorescence of the rat parietal cells. These results demonstrate that PCA invariably react with an antigen represented on the surface of parietal cells, and that this antigen is immunologically identical to the intracytoplasmic 'microsomal' antigen.

Animals↗
PubMed1991

Effect of omeprazole on gene expression in canine gastric parietal cells.

Stimulation of gastric parietal cells by carbachol induces coordinate expression of the genes for two enzymes involved in the process of acid secretion, H(+)-K(+)-ATPase and carbonic anhydrase II (CA II). The basis of this coordinate expression was examined in experiments using parietal cells that had been pretreated with omeprazole. We observed a twofold increase in the steady-state mRNA levels of both H(+)-K(+)-ATPase and CA II after cells were treated with the inhibitor. The induction of CA II mRNA by carbachol followed the same kinetics in omeprazole-pretreated cells as in those that were not pretreated, suggesting that the induction of CA II gene expression by carbachol was not dependent on activation of the gastric H(+)-K(+)-ATPase. In addition, carbachol stimulation of omeprazole-pretreated cells resulted in an induction of one or more larger mRNA species that hybridized with the H(+)-K(+)-ATPase probe. The observation that carbachol-induced increases in steady-state levels of beta-actin mRNA in parietal cells could be inhibited by omeprazole pretreatment suggests a possible linkage between increased beta-actin gene expression and the process of acid secretion.

Actins↗
PubMed1996

Human gastric intrinsic factor expression is not restricted to parietal cells.

Gastric parietal cells have been accepted as the only site of intrinsic factor production in the human stomach. In animals, however, intrinsic factor has been localised to various other cell types of foregut origin, including chief and enteroendocrine cells in gastric mucosa, and duct cells from salivary glands and pancreas. The availability of recombinant human intrinsic factor has led to production of high titre, monospecific antiserum which was used to reexamine the distribution and subcellular localisation of intrinsic factor in the human stomach. Immunolight microscopy revealed that most positively stained cells were gastric parietal cells, but at the margins of the anatomical regions (e.g. cardia/fundus, body/antrum) clusters of gastric chief cells and individual enteroendocrine cells were found to contain intrinsic factor. Immunoelectron microscopy demonstrated the highest antigen density on endocytic and apical membranes of parietal cells. Exocrine secretory granules of a subpopulation of chief cells, the secretory granules of some enteroendocrine cells, and the plasma membranes and smooth vesicles of endothelial cells of the lamina propria capillaries underlying enteroendocrine cells were also positive for the antigen. Labelling in all cells was specific, as it was abolished by preabsorption of the antisera with purified recombinant human intrinsic factor. These findings demonstrate a potential for cellular expression of human intrinsic factor in nonparietal cells. Because such expression occurs normally at the margins of anatomical gastric regions, it suggests that local factors may influence expression of intrinsic factor.

Adult↗
PubMed1991

Carbonic anhydrase II in rat acid secreting cells: comparison of osteoclasts with gastric parietal cells and kidney intercalated cells.

Location of carbonic anhydrase II, an important enzyme involved in acid production, was studied using an immunogold method on ultracryosections. Its distribution in osteoclasts was compared with that in gastric parietal cells and kidney intercalated cells of the inner stripe of outer medulla. It is shown that the distribution of carbonic anhydrase II is much similar in all of these acid producing cells: most of the enzyme is cytoplasmic and nucleoplasmic and only a small fraction of the enzyme is associated with the apical plasma membrane. It seems likely that carbonic anhydrase II has a similar role in all of these acid producing cells.

Animals↗
PubMed1980

The interaction of K+ with gastric parietal cells and gastric ATPase.

The gastric H+ secretion in isolated cell requires K+ and is ATP dependent. There is also evidence in the cell system for Na+ inhibition of H+ secretion. The isolated gastric ATPase also shows K+ activation and inhibition by K+ or Na+ located on the ATP binding side of the enzyme, which corresponds to the cytoplasmic face of the enzyme. Gastric vesicles are activated in terms of transport activity by internal K+, and this site, inhibited by reagents that modify carboxyl groups, is required for enzyme turnover and transport.

Adenosine Triphosphate↗
PubMed2003

Characterization of protein kinase A-mediated phosphorylation of ezrin in gastric parietal cell activation.

Gastric ezrin was initially identified as a phosphoprotein associated with parietal cell activation. To explore the nature of ezrin phosphorylation, proteins from resting and secreting gastric glands were subjected to two-dimensional SDS-PAGE. Histamine triggers acid secretion and a series of acidic isoforms of ezrin on two-dimensional SDS-PAGE. Mass spectrometric analysis of these acidic ezrin spots induced by stimulation suggests that Ser66 is phosphorylated. To determine whether Ser66 is a substrate of protein kinase A (PKA), recombinant proteins of ezrin, both wild type and S66A mutant, were incubated with the catalytic subunit of PKA and [32P]ATP. Incorporation of 32P into wild type but not the mutant ezrin verified that Ser66 is a substrate of PKA. In addition, expression of S66A mutant ezrin in cultured parietal cells attenuates the dilation of apical vacuolar membrane associated with stimulation by histamine, indicating that PKA-mediated phosphorylation of ezrin is necessary for acid secretion. In fact, expression of phosphorylation-like S66D mutant in parietal cells mimics histamine-stimulated apical vacuole remodeling. Further examination of H,K-ATPase distribution revealed a blockade of stimulation-induced proton pump mobilization in S66A but not S66D ezrin-expressing parietal cells. These data suggest that PKA-mediated phosphorylation of ezrin plays an important role in mediating the remodeling of the apical membrane cytoskeleton associated with acid secretion in parietal cells.

Adenosine Triphosphate↗
PubMed2003

Starvation induces the formation of giant mitochondria in gastric parietal cells of guinea pigs.

Mitochondria occasionally increase in size in response to metabolic injury. Numerous studies have reported giant mitochondria in patients with various diseases and animals with metabolic injuries, but there are few reports on giant mitochondria in normal cells under physiological conditions. Here, we report giant mitochondria in normal gastric parietal cells. Stomachs of guinea pigs fed freely, fasted or fasted and then injected with histamine were processed for electron microscopy. Giant mitochondria >2 microm in the diameter of their major axis were observed in resting-type parietal cells in the gastric glands of animals fasted for 60-72 h, whereas acid-secreting-type parietal cells found in those fed ad libitum did not contain giant mitochondria. Giant mitochondria showed unusual structures, especially in their cristae: they contained closely packed, tubular and concentric cristae as well as amorphous and pleomorphic inclusion bodies in their matrix. We observed giant mitochondria consisting of several segments, suggesting the fusion of several normal-sized mitochondria. Histamine injection decreased in a frequency of giant mitochondria in accordance with a decrease in a frequency of resting-type parietal cells. This is the first report of giant mitochondria in gastric parietal cells under physiological or near physiological conditions. Gastric parietal cells might be a good model for examining mitochondrial fusion and fission in a physiological state accompanied by the morphological change of the cells in the membrane system from an acid-secreting to resting type.

Animals↗
PubMed1980

Prostaglandin production by intact isolated gastric parietal cells.

An enriched population of isolated gastric parietal cells was obtained from canine gastric mucosa. Parietal cells incubated with [14C]arachidonic acid produced radiolabelled PGF2 alpha, PGE2, PGD2 and 6-keto PGF1 alpha (acid hydrolysis product of PGI2). The prostaglandin synthesis was inhibited by indomethacin. Prostaglandin production, as measured by gas chromatography-mass spectrometry demonstrated that PGF2 alpha was produced in the highest quantity followed by PGE2 and 6-keto PGF 1 alpha. This demonstrates that isolated prietal cells are capable of producing prostaglandins. Since prostaglandins have a potent effect on gastric acid secretion, local prostaglandin synthesis could modulate parietal cell function.

Animals↗