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Measurement of Transmembrane Potential in the Study Of Systemic Disease*
Published in Richard C. Niemtzow, Transmembrane Potentials and Characteristics of Immune and Tumor Cell, 2020
J. Hamilton Licht, Hardin Jones
The cell membrane regulates the intracellular milieu. It is selectively permeable and has active, energy-requiring transport mechanisms. Intracellular sodium and potassium concentrations represent a balance between active transport and movement of these ions in accordance with their electrical and chemical gradients. Cell membrane function is dependent upon the presence of adequate energy stores (ATP), normal membrane permeability, and normal sodium-potassium-ATPase activity. ATPase activity is a function of both the quantity of available pumping units and the quality of their function. Cells with membrane dysfunction do not thrive. If membrane dysfunction is widespread the integrity of the organism is jeopardized.
Abnormalities of the Calcium Pump in Primary Hypertension
Published in Antonio Coca, Ricardo P. Garay, Ionic Transport in Hypertension: New Perspectives, 2019
Alejandro De la Sierra, Javier Sobrino, Antonio Coca
In the first study in which intact RBC from SHR and essential hypertensive patients were used, Dagher et al.63 concluded that no disturbances in the maximal transport rate nor in the affinity for Ca2+ of the erythrocyte Ca2+-dependent ATPase existed in essential hypertensives. Nevertheless, more detailed analysis of these results revealed slight differences in the tendency of essential hypertensive patients to present lower affinity values for intracellular Ca2+ than those obtained in the normotensive population. In fact, the same authors suggested in the discussion of their results the possibility that a small subgroup of patients did present alterations in the Ca2+-dependent ATPase.
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Published in Calver Pang, Ibraz Hussain, John Mayberry, Pre-Clinical Medicine, 2017
Calver Pang, Ibraz Hussain, John Mayberry
This question focuses on drugs affecting acid secretion. Proton pump inhibitors are acid-activated prodrugs that target ATPase. They inhibit gastric acid secretion by blocking the hydrogen-potassium adenosine triphosphatase enzyme system (proton pump) of gastric parietal cells. The action is delayed as not all pumps are active all of the time therefore maximum efficacy occurs after two to 3 days. Main side effects associated with this class of drugs include gastrointestinal disturbance (nausea, vomiting, abdominal pain, flatulence, diarrhoea, constipation) and headache. Histamine-2 receptor antagonists reduce gastric output as a result of histamine H2-receptor blockade. Alginate taken in combination with an antacid increases the viscosity of stomach contents and can protect the oesophageal mucosa from acid reflux. Some alginate-containing preparations form a viscous gel (‘raft’) that floats on the surface of the stomach contents, thereby reducing reflux symptoms.
pH regulators to target the tumor immune microenvironment in human hepatocellular carcinoma
Published in OncoImmunology, 2018
Olga Kuchuk, Alessandra Tuccitto, Davide Citterio, Veronica Huber, Chiara Camisaschi, Massimo Milione, Barbara Vergani, Antonello Villa, Malcolm Ronald Alison, Simone Carradori, Claudiu T Supuran, Licia Rivoltini, Chiara Castelli, Vincenzo Mazzaferro
HCC is a highly hypoxic tumor due to its rapid growth rate and the surrounding fibrotic tissue produced by chronic inflammation.6 In cancer cells, hypoxia is associated with metabolic reprogramming based on anaerobic glycolysis, leading to the overproduction of pyruvate, lactate and carbonic acids.7 A hypoxic/acidic microenvironment is the hallmark of invasive tumors,8,9 the aggressiveness of which is also driven by the ability to escape adaptive immune surveillance and contribute to local inflammation.10-13 To cope with hypoxic stress and acidity, tumor cells overexpress different pH regulators, including carbonic anhydrase (CA) IX and XII.14 CAs are zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide to carbonic acid and are involved in respiration and acid-base equilibrium.14 V-ATPase is also a key protein in the regulation of the tumor acidic microenvironment and is one of the most studied pH regulators in cancer.15 V-ATPase consists of multiple subunits assembled in two domains: the membrane-associated domain V0 transports protons across the membrane, while the cytoplasmic domain V1 hydrolyses ATP.16 Each V-ATPase subunit displays several splice variants, conferring specific intracellular localization and tissue specificity.17
ATP6V1H facilitates osteogenic differentiation in MC3T3-E1 cells via Akt/GSK3β signaling pathway
Published in Organogenesis, 2019
Fusong Jiang, Haojie Shan, Chenhao Pan, Zubin Zhou, Keze Cui, Yuanliang Chen, Haibo Zhong, Zhibin Lin, Nan Wang, Liang Yan, Xiaowei Yu
ATP6V1H (V-type proton ATPase subunit H) encodes the subunit H of V-type proton ATPase,4 and plays crucial roles in various biological processes, including a key role in regulating functions of osteoblastic cells.5 Through interacting with TGF-β receptor I and AP-2 complex, ATP6V1H regulates the proliferation and differentiation of bone marrow stromal cells.6 In zebrafish, ATP6V1H loss-of-function mutants led to severe reduced number of mature-calcified bone cells, demonstrating that ATP6V1H could regulate bone formation.5 In addition, ATP6V1H± knockout mice showed significantly decreased bone remodeling, bone matrix loss and impaired bone formation.7
The role of lysosomal ion channels in lysosome dysfunction
Published in Inhalation Toxicology, 2021
Rebekah L. Kendall, Andrij Holian
Ion channels play a crucial role in maintaining the necessary pH levels for lysosomal function, as the ionic homeostasis necessary for lysosome acidification comes from the progressive proton pump activity of the vacuolar-type ATPase (V-ATPase) in conjunction with ionic movement by other channels (Mindell 2012). The V-ATPase is similar in many ways to the F-type ATPase found in the inner mitochondrial membrane, a rotary proton transport machine comprised of multiple subunits organized into two large domains, V1 and V0. The peripheral domain, V1, catalyzes the cytosolic hydrolysis of ATP, providing the energy needed to pump protons into the lumen. The membrane-embedded domain, V0, houses the rotary component that facilitates the transport of protons from the cytosol into the lumen (Mindell 2012). The V-ATPase proton pumping action is irreversible and highly efficient, moving 2-4 protons into the lysosome lumen per ATP hydrolyzed (Mindell 2012; Colacurcio and Nixon 2016). The coupling ratio of protons to ATP is dynamic and allows the lysosome to react to a variety of substrates while maintaining an optimal pH that can change depending on nutrient needs of the cell (Li et al. 2019). This ability to maintain an optimal pH is dependent on the function of other lysosomal ion channels and membrane potential. The H+ concentration within the lysosome is balanced by an influx and efflux of ions to counter the charges contained within the lumen and maintain the lysosomal membrane potential necessary for continued V-ATPase function (Xu and Ren 2015; Kissing et al. 2018). A more comprehensive understanding of V-ATPase activity and its role in lysosome function can be found in these reviews (Mindell 2012; Cotter et al. 2015; Kissing et al. 2018).