Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The variations of the pH in Xenopus yolk platelets have been estimated by fluorescence confocal microscopy and computer image processing. For pH measurements in vitellogenic oocytes, the pH-sensitive fluorescent dye, DM-NERF, was coupled to vitellogenin, and the DM-NERF-vitellogenin was taken up by oocytes via receptor-mediated endocytosis. Dual emission ratio measurements of internalized DM-NERF-vitellogenin indicated that the mature yolk platelets are mildly acidic (pH 5.6). Their precursors, the primordial yolk platelets, have a similar pH. This pH is probably sufficiently low for the partial cleavage of vitellogenin to yolk proteins, but not for yolk degradation. The yolk platelet pH at various developmental stages was estimated by measuring the accumulation of Acridine Orange, both in isolated yolk platelets and in disaggregated embryonic cells. During oogenesis, the yolk platelets accumulated a constant amount of Acridine Orange, corresponding to a pH of around 5.7. During embryogenesis, however, yolk platelets became progressively much more acidic (pH < 5). Acidification correlated with yolk degradation in the various tissues examined, and yolk utilization was blocked when acidification was inhibited with bafilomycin, an inhibitor of vacuolar H+-ATPase. Bafilomycin also inhibited differentiation of cells isolated from stage 13-15 embryos. These data show that the yolk platelet pH is developmentally regulated and is involved in triggering yolk degradation. Also, yolk acidification and degradation appeared to be associated with cell differentiation and with the formation of the endosomal/lysosomal compartment, typical of adult cells, but absent in early embryos.
 ...
PMID:Changes in yolk platelet pH during Xenopus laevis development correlate with yolk utilization. A quantitative confocal microscopy study. 770 89

The small hydrophobic E5 protein of Human Papillomavirus type 16 (HPV16) binds to the 16-kDa subunit of the V-H+-ATPase. This binding has been suggested to interfere with acidification of late endocytic structures. We here used video microscopy, ratio imaging and confocal microscopy of living C127 fibroblasts to study the effects of E5. Various endocytic markers including the pH-sensitive probe DM-NERF coupled to dextran, TransFluoSpheres and TRITC-concanavalin A, were applied. In E5-transfected cells, none of these markers colocalized with the membrane permeable probe LysoTracker Red, which accumulates in acidic, late endocytic structures, or with a green fluorescent version of the small GTPase Rab7 labeling late endocytic structures. Importantly, however, late endocytic structures accumulating LysoTracker were still present in the E5-transfected cells. It is therefore concluded that HPV16 E5 perturbs trafficking from early to late endocytic structures rather than acidification.
 ...
PMID:The HPV16 E5 oncogene inhibits endocytic trafficking. 1114 54

In the stomach, production of prostaglandins by cyclo-oxygenase (COX) is believed to be important in mucosal defence. We tested the hypothesis that endogenous COX activity is required for protective gastric surface pH control. Intact stomachs of anaesthetized mice were perfused with a weakly buffered solution (150 mM NaCl + 4 mM Homopipes) at pH values from 2.5 to 7.0. Gastric effluents were collected to measure pH and estimate amounts of acid or alkali secretion in nanomoles secreted per minute. A switch from net acid to net alkali secretion was seen in response to acidifying luminal pH with an apparent 'set point' between pH 4 and 5. At luminal pH 3, the net alkali secretion (12.7 +/- 2.8 nmol OH(-) equivalents min(-1)) was abolished (2.2 +/- 1.7 nmol OH(-) min(-1)) by the non-specific COX inhibitor indomethacin (5 mg kg(-1) I.P.). Similar inhibition was observed using a COX-1 inhibitor (SC-560; 10 mg kg(-1) I.P.), but not a COX-2 inhibitor (NS-398; 10 mg kg(-1) I.P.). Subsequent treatment with 16,16-dimethyl prostaglandin E(2) (dm-PGE(2); 1 mg kg(-1) I.P.) rescued the alkali secretion (21.8 +/- 2.7 nmol OH(-) min(-1)). In either the absence or presence of the H(+),K(+)-ATPase inhibitor omeprazole (60 mg kg(-1) I.P.), indomethacin blocked similar amounts of net alkali secretion (10.5 +/- 2.7 and 16.4 +/- 3.4 nmol OH(-) min(-1), respectively). We also used in vivo confocal microscopy to examine pH near the mucosal surface. The gastric mucosal surface of anaesthetized mice was exposed and mucosal surface pH was imaged using the fluorescence intensity ratio of Cl-NERF as a pH indicator. Results showed a switch from a continuous net acid to net alkali secretion by the stomach in response to changing superfusate pH from 5 to 3. At luminal pH 3, the relatively alkaline surface pH (4.3 +/- 0.1) was acidified (3.6 +/- 0.2) by indomethacin, and subsequent dm-PGE(2) restored surface pH (4.2 +/- 0.2). We conclude that the pre-epithelial alkaline layer is regulated by endogenous COX activity.
 ...
PMID:Endogenous cyclo-oxygenase activity regulates mouse gastric surface pH. 1241 30