Hypertonic activation of AE2 anion exchanger in Xenopus oocytes via NHE-mediated intracellular alkalinization

1995 ◽  
Vol 268 (1) ◽  
pp. C201-C209 ◽  
Author(s):  
B. D. Humphreys ◽  
L. Jiang ◽  
M. N. Chernova ◽  
S. L. Alper
Keyword(s):  
Anion Exchanger ◽  
Cellular Response ◽  
Xenopus Oocytes ◽  
Chloride Transport ◽  
Cell Types ◽  
Dependent Manner ◽  
Hypertonic Stress ◽  
Anion Transporter ◽  
Hypertonic Stimulation ◽  
Exchange Activity

Xenopus oocytes express endogenous Na+/H+ exchange activity but lack significant endogenous Cl-/HCO3- exchange activity. Coupled operation of Na+/H+ exchange and Cl-/HCO3- exchange contributes in many cell types to the cellular response to hypertonic stress. We therefore examined in Xenopus oocytes the osmotic regulation of chloride transport mediated by recombinant anion exchanger proteins AE2 and AE1. Hypotonicity was without effect on either anion transporter. Hypertonicity activated AE2-associated 36Cl- influx and efflux in a time- and osmolarity-dependent manner, whether incremental osmoles were charged or uncharged, but had no measurable effect on AE1 function. Hypertonic stimulation of AE2 was completely inhibited by Na+ removal or by addition of amiloride. In contrast, neither maneuver altered isotonic activity of AE2. Hypertonicity also induced amiloride-sensitive elevation of oocyte intracellular pH (pHi), and shifted the sigmoidal relationship of extracellular pH vs. AE2 activity > or = 0.5 units to the acid. Injection of pH 7.4 buffer into oocytes attenuated both hypertonic alkalinization and activation of AE2-associated 36Cl- influx, without inhibition of isotonic AE2 function. These data demonstrate that recombinant AE2 expressed in Xenopus oocytes is activated by increased pHi and that hypertonic activation of AE2 is secondary to hypertonic activation of Na+/H+ exchange.

Localization of endogenous and recombinant Na+-driven anion exchanger protein NDAE1 fromDrosophila melanogaster

2001 ◽  
Vol 281 (2) ◽  
pp. C449-C463 ◽  
Author(s):  
Christopher M. Sciortino ◽  
Lamara D. Shrode ◽  
Bonnie R. Fletcher ◽  
Peter J. Harte ◽  
Michael F. Romero
Keyword(s):  
Xenopus Oocytes ◽  
Alimentary Tract ◽  
Regulatory Protein ◽  
Malpighian Tubule ◽  
Cell Types ◽  
Malpighian Tubules ◽  
Developmental Expression ◽  
Α Subunit ◽  
Vertebrate Cell ◽  
Exchange Activity

Na+-dependent Cl−/HCO[Formula: see text]exchange activity helps maintain intracellular pH (pHi) homeostasis in many invertebrate and vertebrate cell types. Our laboratory cloned and characterized a Na+-dependent Cl−/HCO[Formula: see text] exchanger (NDAE1) from Drosophila melanogaster (Romero MF, Henry D, Nelson S, Harte PJ, and Sciortino CM. J Biol Chem 275: 24552–24559, 2000). In the present study we used immunohistochemical and Western blot techniques to characterize the developmental expression, subcellular localization, and tissue distribution of NDAE1 protein in D. melanogaster. We have shown that a polyclonal antibody raised against the NH2terminus of NDAE1 (αCWR57) recognizes NDAE1 electrophysiologically characterized in Xenopus oocytes. Moreover, our results begin to delineate the NDAE1 topology, i.e., both the NH2and COOH termini are intracellular. NDAE1 is expressed throughout Drosophila development in the central and peripheral nervous systems, sensilla, and the alimentary tract (Malpighian tubules, gut, and salivary glands). Coimmunolabeling of larval tissues with NDAE1 antibody and a monoclonal antibody to the Na+-K+-ATPase α-subunit revealed that the majority of NDAE1 is located at the basolateral membranes of Malpighian tubule cells. These results suggest that NDAE1 may be a key pHi regulatory protein and may contribute to basolateral ion transport in epithelia and nervous system of Drosophila.

Pyrrolo-1,5-benzoxazepines: a new class of apoptotic agents

2001 ◽  
Vol 29 (6) ◽  
pp. 704-706 ◽  
Author(s):  
D. M. Zisterer ◽  
M. M. McGee ◽  
G. Campiani ◽  
A. Ramunno ◽  
C. Fattorusso ◽  
...  
Keyword(s):  
Cellular Response ◽  
Caspase 3 ◽  
Signal Transduction Pathway ◽  
Benzodiazepine Receptor ◽  
Cell Types ◽  
Dependent Manner ◽  
Apoptotic Pathway ◽  
Leukaemia Cell Line ◽  
Apoptotic Activity ◽  
Induced Apoptosis

Some members of a series of novel pyrrolo-1,5-benzoxazepines (PBOXs) potently induce apoptosis in a number of human cancerous cell lines including HL-60 cells and the drug-resistant chronic myelogenous leukaemia cell line, K562. The apoptotic induction seems to be independent of the mitochondrial peripheral-type benzodiazepine receptor (PBR), which binds these PBOXs with high affinity, due to a lack of correlation between their affinities for the receptor and their apoptotic potencies and their high apoptotic activity in PBR-deficient cells. PBOX-6, a potent member of the series, induces a transient activation of c-Jun N-terminal kinase (JNK) in a dose-dependent manner, which correlates with induction of apoptosis. Expression of a cytoplasmic inhibitor of the JNK signal transduction pathway, Jip-1, prevents JNK activity and significantly reduces the extent of apoptosis induced by PBOX-6. This demonstrates the requirement for JNK in the cellular response to this apoptotic agent. In addition, PBOX-6 activates caspase-3-like proteases in K562 and HL-60 cells. The caspase-3 inhibitor, Z-Asp-Glu-Val-Asp-fluoromethylketone (z-DEVD-fmk), blocks caspase-3-like protease activity in both cell types but only prevents PBOX-6-induced apoptosis in HL-60 cells, suggesting that the requirement for caspase-3-like proteases in the apoptotic pathway is dependent on the cell type.

NH4Cl activates AE2 anion exchanger in Xenopus oocytes at acidic pHi

1997 ◽  
Vol 272 (4) ◽  
pp. C1232-C1240 ◽  
Author(s):  
B. D. Humphreys ◽  
M. N. Chernova ◽  
L. Jiang ◽  
Y. Zhang ◽  
S. L. Alper
Keyword(s):  
Intracellular Ph ◽  
Anion Exchanger ◽  
Sodium Acetate ◽  
Xenopus Oocytes ◽  
Renal Medulla ◽  
Disulfonic Acid ◽  
Acidic Ph ◽  
Intracellular Acidification ◽  
Extracellular Acidification ◽  
Exchange Activity

In the course of experiments to define regulation by intracellular pH (pHi) of the AE2 anion exchanger expressed in Xenopus oocytes, we discovered an unexpected regulation of AE2 by NH4+. Intracellular acidification produced by extracellular acidification or produced by equimolar substitution of NaCl with sodium acetate each inhibited AE2 activity. In contrast, intracellular acidification by equimolar substitution of NaCl with NH4Cl activated AE2-associated, trans-anion-dependent, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid-sensitive 36Cl- influx and efflux. Regulation by NH4+ was isoform specific, since neither erythroid nor kidney AE1 was activated. AE2 activation was maximal at <5 mM NH4Cl; was not mimicked by extracellular KCl, chloroquine, or polyamines; and was insensitive to amiloride, bumetanide, barium, and gadolinium. Whether NH4Cl acts directly on AE2 or on another target remains to be determined. Activation of AE2 by NH4+ may serve to sustain Cl-/HCO3- exchange activity in the presence of acidic pH in renal medulla, colon, abscesses, and other AE2-expressing acidic locales exposed to elevated NH4+ concentration.

scholarly journals Matrix stiffness controls ciliogenesis and centriole position

2021 ◽  
Author(s):  
Ivanna Williantarra ◽  
Sophia Leung ◽  
Yu Suk Choi ◽  
Ashika Chhana ◽  
Susan R McGlashan
Keyword(s):  
Primary Cilium ◽  
Cellular Response ◽  
Primary Cilia ◽  
Basal Membrane ◽  
Cell Types ◽  
Substrate Stiffness ◽  
Dependent Manner ◽  
Wide Range ◽  
The Matrix ◽  
External Forces

Mechanical stress and the stiffness of the extracellular matrix are key drivers of tissue development and homeostasis. Aberrant mechanosensation is associated with a wide range of pathologies, including diseases such as osteoarthritis. Substrate stiffness is one of the well-known mechanical properties of the matrix that enabled establishing the central dogma of an integrin-mediated mechanotransduction using stem cells. However, how specific cells 'feel' or sense substrate stiffness requires further study. The primary cilium is an essential cellular organelle that senses and integrates mechanical and chemical signals from the extracellular environment. We hypothesised that the primary cilium dynamically alters its length and position to fine-tune cell mechanosignalling based on substrate stiffness alone. We used a hydrogel system of varying substrate stiffness to examine the role of substrate stiffness on cilia frequency, length and centriole position as well as cell and nuclei area over time. Contrary to other cell types, we show that chondrocyte primary cilia shorten on softer substrates demonstrating tissue-specific mechanosensing which is aligned with the tissue stiffness the cells originate from. We further show that stiffness alone determine centriole positioning to either the basal or apical membranes during attachment and spreading, with centriole positioned towards the basal membrane on stiffer substrates. These phenomena are mediated by force generation actin-myosin stress fibres in a time-dependent manner. Based on these findings, we propose that substrate stiffness plays a central role in cilia positioning, regulating cellular response to external forces, and may be a key driver of mechanosignalling-associated diseases.

scholarly journals Interleukin-15 Activates Proinflammatory and Antimicrobial Functions in Polymorphonuclear Cells

1998 ◽  
Vol 66 (6) ◽  
pp. 2640-2647 ◽  
Author(s):  
Tiziana Musso ◽  
Liliana Calosso ◽  
Mario Zucca ◽  
Maura Millesimo ◽  
Manuela Puliti ◽  
...  
Keyword(s):  
Cellular Response ◽  
Cell Types ◽  
Polymorphonuclear Cells ◽  
Dependent Manner ◽  
Microbial Infection ◽  
Phagocytic Cells ◽  
Protein Levels ◽  
Reverse Transcription Pcr ◽  
Wide Range ◽  
Interleukin 15

ABSTRACT Interleukin-15 (IL-15) is a recently discovered cytokine produced by a wide range of different cell types including fibroblasts, keratinocytes, endothelial cells, and macrophages in response to lipopolysaccharide or microbial infection. This suggests that IL-15 may play a crucial role in the activation of phagocytic cells against pathogens. We studied polymorphonuclear leukocyte (PMN) activation by IL-15, evaluated as enhancement of PMN anti-Candidaactivity as well as IL-8 production, following stimulation with the cytokine. The PMN response to IL-15 depends on binding to the IL-15 receptor. Our experiments show that binding of a biotinylated human IL-15–immunoglobulin G2b IgG2b fusion protein was competed by the addition of human recombinant IL-15 (rIL-15) or of human rIL-2, suggesting that IL-15 binding to PMN might involve the IL-2Rβ and IL-2Rγ chains, which have been shown to be constitutively expressed by PMN. In addition, we show by reverse transcription-PCR and by flow cytometry with a specific anti-IL-15Rα chain monoclonal antibody that PMN express the IL-15Rα chain at the mRNA and protein levels. Incubation with IL-15 activated PMN to secrete the chemotactic factor IL-8, and the amount secreted was increased by costimulation with heat-inactivated Candida albicans. In addition, IL-15 primed the metabolic burst of PMN in response to formyl-methionyl-leucyl-phenylalanine but was not sufficient to trigger the respiratory burst or to increase the production of superoxide in PMN exposed to C. albicans. IL-15 also increased the ability of PMN to phagocytose heat-killed C. albicansorganisms in a dose-dependent manner, without opsonization by antibodies or complement-derived products. In the same concentration range, IL-15 was as effective as gamma interferon (IFN-γ) and IL-2 in increasing the C. albicans growth-inhibitory activity of PMN. Taken together, these results suggest that IL-15 is a potent stimulant of both proinflammatory and antifungal activities of PMN, activating several antimicrobial functions of PMN involved in the cellular response against C. albicans.

Effects of cytochrome c on the mitochondrial apoptosis-induced channel MAC

2004 ◽  
Vol 286 (5) ◽  
pp. C1109-C1117 ◽  
Author(s):  
Liang Guo ◽  
Dawn Pietkiewicz ◽  
Evgeny V. Pavlov ◽  
Sergey M. Grigoriev ◽  
John J. Kasianowicz ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Outer Membrane ◽  
Cell Types ◽  
Rnase A ◽  
Mitochondrial Outer Membrane ◽  
Dependent Manner ◽  
Mitochondrial Apoptosis ◽  
Noise Type ◽  
Voltage Dependent

Recent studies indicate that cytochrome c is released early in apoptosis without loss of integrity of the mitochondrial outer membrane in some cell types. The high-conductance mitochondrial apoptosis-induced channel (MAC) forms in the outer membrane early in apoptosis of FL5.12 cells. Physiological (micromolar) levels of cytochrome c alter MAC activity, and these effects are referred to as types 1 and 2. Type 1 effects are consistent with a partitioning of cytochrome c into the pore of MAC and include a modest decrease in conductance that is dose and voltage dependent, reversible, and has an increase in noise. Type 2 effects may correspond to “plugging” of the pore or destabilization of the open state. Type 2 effects are a dose-dependent, voltage-independent, and irreversible decrease in conductance. MAC is a heterogeneous channel with variable conductance. Cytochrome c affects MAC in a pore size-dependent manner, with maximal effects of cytochrome c on MAC with conductance of 1.9–5.4 nS. The effects of cytochrome c, RNase A, and high salt on MAC indicate that size, rather than charge, is crucial. The effects of dextran molecules of various sizes indicate that the pore diameter of MAC is slightly larger than that of 17-kDa dextran, which should be sufficient to allow the passage of 12-kDa cytochrome c. These findings are consistent with the notion that MAC is the pore through which cytochrome c is released from mitochondria during apoptosis.

Production and Analysis of High Resolution Polymer Replicas of Fibrillar Collagen

1999 ◽  
Vol 5 (S2) ◽  
pp. 398-399
Author(s):  
P. Sims ◽  
B. Todd ◽  
S. Eppell ◽  
T. Li ◽  
K. Park ◽  
...  
Keyword(s):  
Cellular Response ◽  
Physical Nature ◽  
Cell Types ◽  
Artificial Substrates ◽  
Adherent Cell ◽  
Fibrillar Collagen ◽  
New Materials ◽  
Substrate Interactions ◽  
Number Of Factors ◽  
Cell Substrate

Adherent cells generally construct the immediate substrate upon which they reside. This may occur via synthesis and secretion of new materials and/or by rearrangement and modification of existing substrate. The response of adherent cell types to an existing substrate can be influenced by a number of factors which include both the chemical and physical nature of the substrate. Cell adhesion, proliferation, differentiation and death can all be substrate dependent. Much effort has been directed toward chemical modification of substrates to regulate one or more of the parameters noted above. A significant, but somewhat smaller, degree of attention has been paid to the effects of the topography and microtopography on the cell response to substrate materials. Studies to date strongly suggest the topography is a significant factor in cell-substrate interactions. As noted above, it is most probable that both the chemistry and the structure of a substrate simultaneously influence the cellular response. However we wished to determine, particularly for artificial substrates, the role which microtopography can play in cell-substrate interactions.

scholarly journals The binding of NCAM to FGFR1 induces a specific cellular response mediated by receptor trafficking

2009 ◽  
Vol 187 (7) ◽  
pp. 1101-1116 ◽  
Author(s):  
Chiara Francavilla ◽  
Paola Cattaneo ◽  
Vladimir Berezin ◽  
Elisabeth Bock ◽  
Diletta Ami ◽  
...  
Keyword(s):  
Cell Migration ◽  
Cellular Response ◽  
Critical Role ◽  
Biological Significance ◽  
Receptor Activation ◽  
Dependent Manner ◽  
Fgf Receptor ◽  
Neural Cell Adhesion ◽  
Sustained Activation

Neural cell adhesion molecule (NCAM) associates with fibroblast growth factor (FGF) receptor-1 (FGFR1). However, the biological significance of this interaction remains largely elusive. In this study, we show that NCAM induces a specific, FGFR1-mediated cellular response that is remarkably different from that elicited by FGF-2. In contrast to FGF-induced degradation of endocytic FGFR1, NCAM promotes the stabilization of the receptor, which is recycled to the cell surface in a Rab11- and Src-dependent manner. In turn, FGFR1 recycling is required for NCAM-induced sustained activation of various effectors. Furthermore, NCAM, but not FGF-2, promotes cell migration, and this response depends on FGFR1 recycling and sustained Src activation. Our results implicate NCAM as a nonconventional ligand for FGFR1 that exerts a peculiar control on the intracellular trafficking of the receptor, resulting in a specific cellular response. Besides introducing a further level of complexity in the regulation of FGFR1 function, our findings highlight the link of FGFR recycling with sustained signaling and cell migration and the critical role of these events in dictating the cellular response evoked by receptor activation.

scholarly journals Mechanisms in allergic airway inflammation – lessons from studies in the mouse

2008 ◽  
Vol 10 ◽  
Author(s):  
Bennett O.V. Shum ◽  
Michael S. Rolph ◽  
William A. Sewell
Keyword(s):  
Inflammatory Response ◽  
Airway Inflammation ◽  
Cellular Response ◽  
Allergic Airway Inflammation ◽  
Cell Types ◽  
Therapeutic Agents ◽  
Chronic Inflammatory Disease ◽  
Pathological Feature ◽  
Cytokines And Chemokines ◽  
Novel Therapeutic

Asthma is a chronic inflammatory disease of the airways, involving recurrent episodes of airway obstruction and wheezing. A common pathological feature in asthma is the presence of a characteristic allergic airway inflammatory response involving extensive leukocyte infiltration, mucus overproduction and airway hyper-reactivity. The pathogenesis of allergic airway inflammation is complex, involving multiple cell types such as T helper 2 cells, regulatory T cells, eosinophils, dendritic cells, mast cells, and parenchymal cells of the lung. The cellular response in allergic airway inflammation is controlled by a broad range of bioactive mediators, including IgE, cytokines and chemokines. The asthmatic allergic inflammatory response has been a particular focus of efforts to develop novel therapeutic agents. Animal models are widely used to investigate inflammatory mechanisms. Although these models are not perfect replicas of clinical asthma, such studies have led to the development of numerous novel therapeutic agents, of which some have already been successful in clinical trials.

Transcriptional targets of DAF-16 insulin signaling pathway protect C. elegans from extreme hypertonic stress

2005 ◽  
Vol 288 (2) ◽  
pp. C467-C474 ◽  
Author(s):  
S. Todd Lamitina ◽  
Kevin Strange
Keyword(s):  
Insulin Signaling ◽  
Stress Resistance ◽  
Molecular Mechanisms ◽  
Organic Osmolytes ◽  
Dependent Manner ◽  
Animal Cells ◽  
Hypertonic Stress ◽  
C Elegans ◽  
Downstream Target ◽  
Molecular Damage

All cells adapt to hypertonic stress by regulating their volume after shrinkage, by accumulating organic osmolytes, and by activating mechanisms that protect against and repair hypertonicity-induced damage. In mammals and nematodes, inhibition of signaling from the DAF-2/IGF-1 insulin receptor activates the DAF-16/FOXO transcription factor, resulting in increased life span and resistance to some types of stress. We tested the hypothesis that inhibition of insulin signaling in Caenorhabditis elegans also increases hypertonic stress resistance. Genetic inhibition of DAF-2 or its downstream target, the AGE-1 phosphatidylinositol 3-kinase, confers striking resistance to a normally lethal hypertonic shock in a DAF-16-dependent manner. However, insulin signaling is not inhibited by or required for adaptation to hypertonic conditions. Microarray studies have identified 263 genes that are transcriptionally upregulated by DAF-16 activation. We identified 14 DAF-16-upregulated genes by RNA interference screening that are required for age- 1 hypertonic stress resistance. These genes encode heat shock proteins, proteins of unknown function, and trehalose synthesis enzymes. Trehalose levels were elevated approximately twofold in age- 1 mutants, but this increase was insufficient to prevent rapid hypertonic shrinkage. However, age- 1 animals unable to synthesize trehalose survive poorly under hypertonic conditions. We conclude that increased expression of proteins that protect eukaryotic cells against environmental stress and/or repair stress-induced molecular damage confers hypertonic stress resistance in C. elegans daf- 2/ age- 1 mutants. Elevated levels of solutes such as trehalose may also function in a cytoprotective manner. Our studies provide novel insights into stress resistance in animal cells and a foundation for new studies aimed at defining molecular mechanisms underlying these essential processes.

Sign in / Sign up

Export Citation Format

Share Document