101
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Kordium VA, Irodov DM, Maslova OO, Ruban TA, Sukhorada EM, Andrienko VI, Shuvalova NS, Likhachova LI, Shpilova SP. Fundamental biology reached a plateau – development of ideas. ACTA ACUST UNITED AC 2011. [DOI: 10.7124/bc.00011b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- V. A. Kordium
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - D. M. Irodov
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - O. O. Maslova
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - T. A. Ruban
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - E. M. Sukhorada
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - V. I. Andrienko
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - N. S. Shuvalova
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - L. I. Likhachova
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
| | - S. P. Shpilova
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine
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102
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Aabo T, Glückstad J, Siegumfeldt H, Arneborg N. Intracellular pH distribution as a cell health indicator in Saccharomyces cerevisiae. J R Soc Interface 2011; 8:1635-43. [PMID: 21527496 PMCID: PMC3177618 DOI: 10.1098/rsif.2011.0148] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 04/08/2011] [Indexed: 11/12/2022] Open
Abstract
Internal pH regulation is vital for many cell functions, including transport mechanisms and metabolic enzyme activity. More specifically, transport mechanisms are to a wide degree governed by internal pH distributions. We introduce the term standard deviation of the intracellular pH (s.d.(pH(int))) to describe the internal pH distributions. The cellular pH distributional response to external stress such as heat has not previously been determined. In this study, the intracellular pH (pH(i)) and the s.d.(pH(int)) of Saccharomyces cerevisiae cells exposed to supralethal temperatures were measured using fluorescence ratio imaging microscopy (FRIM). An exponential decline in pH(i) was observed after an initial small decline. For the first time, we report the use of FRIM for determining in vivo plasma membrane proton permeability coefficients in yeast. Furthermore, the exponential decay of pH(i) and the rupture of the cell plasma membrane, as measured by propidium iodide staining, at 70°C were not simultaneous but were separated by a significant temporal difference. Finally, a nonlinear relationship between the pH(i) and s.d.(pH(int)) was found; i.e. the s.d.(pH(int)) was significantly more sensitive to supralethal temperatures than pH(i). s.d.(pH(int)) is therefore proposed as an early health/vitality indicator in S. cerevisiae cells exposed to heat stress.
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Affiliation(s)
- Thomas Aabo
- Department of Food Science, University of Copenhagen, , Frederiksberg, Denmark.
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103
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van der Poel S, Wolthoorn J, van den Heuvel D, Egmond M, Groux-Degroote S, Neumann S, Gerritsen H, van Meer G, Sprong H. Hyperacidification of Trans-Golgi Network and Endo/Lysosomes in Melanocytes by Glucosylceramide-Dependent V-ATPase Activity. Traffic 2011; 12:1634-47. [DOI: 10.1111/j.1600-0854.2011.01263.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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104
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Overmeyer JH, Young AM, Bhanot H, Maltese WA. A chalcone-related small molecule that induces methuosis, a novel form of non-apoptotic cell death, in glioblastoma cells. Mol Cancer 2011; 10:69. [PMID: 21639944 PMCID: PMC3118192 DOI: 10.1186/1476-4598-10-69] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 06/06/2011] [Indexed: 01/19/2023] Open
Abstract
Background Methuosis is a unique form of non-apoptotic cell death triggered by alterations in the trafficking of clathrin-independent endosomes, ultimately leading to extreme vacuolization and rupture of the cell. Results Here we describe a novel chalcone-like molecule, 3-(2-methyl-1H- indol-3-yl)-1-(4-pyridinyl)-2-propen-1-one (MIPP) that induces cell death with the hallmarks of methuosis. MIPP causes rapid accumulation of vacuoles derived from macropinosomes, based on time-lapse microscopy and labeling with extracellular fluid phase tracers. Vacuolization can be blocked by the cholesterol-interacting compound, filipin, consistent with the origin of the vacuoles from non-clathrin endocytic compartments. Although the vacuoles rapidly acquire some characteristics of late endosomes (Rab7, LAMP1), they remain distinct from lysosomal and autophagosomal compartments, suggestive of a block at the late endosome/lysosome boundary. MIPP appears to target steps in the endosomal trafficking pathway involving Rab5 and Rab7, as evidenced by changes in the activation states of these GTPases. These effects are specific, as other GTPases (Rac1, Arf6) are unaffected by the compound. Cells treated with MIPP lose viability within 2-3 days, but their nuclei show no evidence of apoptotic changes. Inhibition of caspase activity does not protect the cells, consistent with a non-apoptotic death mechanism. U251 glioblastoma cells selected for temozolomide resistance showed sensitivity to MIPP-induced methuosis that was comparable to the parental cell line. Conclusions MIPP might serve as a prototype for new drugs that could be used to induce non-apoptotic death in cancers that have become refractory to agents that work through DNA damage and apoptotic mechanisms.
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Affiliation(s)
- Jean H Overmeyer
- Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio, USA
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105
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Koivusalo M, Steinberg BE, Mason D, Grinstein S. In situ Measurement of the Electrical Potential Across the Lysosomal Membrane Using FRET. Traffic 2011; 12:972-82. [DOI: 10.1111/j.1600-0854.2011.01215.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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106
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Orij R, Brul S, Smits GJ. Intracellular pH is a tightly controlled signal in yeast. Biochim Biophys Acta Gen Subj 2011; 1810:933-44. [PMID: 21421024 DOI: 10.1016/j.bbagen.2011.03.011] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 03/15/2011] [Accepted: 03/15/2011] [Indexed: 11/25/2022]
Abstract
BACKGROUND Nearly all processes in living cells are pH dependent, which is why intracellular pH (pH(i)) is a tightly regulated physiological parameter in all cellular systems. However, in microbes such as yeast, pH(i) responds to extracellular conditions such as the availability of nutrients. This raises the question of how pH(i) dynamics affect cellular function. SCOPE OF REVIEW We discuss the control of pH(i,) and the regulation of processes by pH(i), focusing on the model organism Saccharomyces cerevisiae. We aim to dissect the effects of pH(i) on various aspects of cell physiology, which are often intertwined. Our goal is to provide a broad overview of how pH(i) is controlled in yeast, and how pH(i) in turn controls physiology, in the context of both general cellular functioning as well as of cellular decision making upon changes in the cell's environment. MAJOR CONCLUSIONS Besides a better understanding of the regulation of pH(i), evidence for a signaling role of pH(i) is accumulating. We conclude that pH(i) responds to nutritional cues and relays this information to alter cellular make-up and physiology. The physicochemical properties of pH allow the signal to be fast, and affect multiple regulatory levels simultaneously. GENERAL SIGNIFICANCE The mechanisms for regulation of processes by pH(i) are tightly linked to the molecules that are part of all living cells, and the biophysical properties of the signal are universal amongst all living organisms, and similar types of regulation are suggested in mammals. Therefore, dynamic control of cellular decision making by pH(i) is therefore likely a general trait. This article is part of a Special Issue entitled: Systems Biology of Microorganisms.
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Affiliation(s)
- Rick Orij
- Swammerdam Institute for Life Sciences, University of Amsterdam, the Netherlands.
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107
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Genome-wide analysis reveals the vacuolar pH-stat of Saccharomyces cerevisiae. PLoS One 2011; 6:e17619. [PMID: 21423800 PMCID: PMC3056714 DOI: 10.1371/journal.pone.0017619] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 02/02/2011] [Indexed: 11/26/2022] Open
Abstract
Protons, the smallest and most ubiquitous of ions, are central to physiological processes. Transmembrane proton gradients drive ATP synthesis, metabolite transport, receptor recycling and vesicle trafficking, while compartmental pH controls enzyme function. Despite this fundamental importance, the mechanisms underlying pH homeostasis are not entirely accounted for in any organelle or organism. We undertook a genome-wide survey of vacuole pH (pHv) in 4,606 single-gene deletion mutants of Saccharomyces cerevisiae under control, acid and alkali stress conditions to reveal the vacuolar pH-stat. Median pHv (5.27±0.13) was resistant to acid stress (5.28±0.14) but shifted significantly in response to alkali stress (5.83±0.13). Of 107 mutants that displayed aberrant pHv under more than one external pH condition, functional categories of transporters, membrane biogenesis and trafficking machinery were significantly enriched. Phospholipid flippases, encoded by the family of P4-type ATPases, emerged as pH regulators, as did the yeast ortholog of Niemann Pick Type C protein, implicated in sterol trafficking. An independent genetic screen revealed that correction of pHv dysregulation in a neo1ts mutant restored viability whereas cholesterol accumulation in human NPC1−/− fibroblasts diminished upon treatment with a proton ionophore. Furthermore, while it is established that lumenal pH affects trafficking, this study revealed a reciprocal link with many mutants defective in anterograde pathways being hyperacidic and retrograde pathway mutants with alkaline vacuoles. In these and other examples, pH perturbations emerge as a hitherto unrecognized phenotype that may contribute to the cellular basis of disease and offer potential therapeutic intervention through pH modulation.
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108
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Zhang Z, Nguyen KT, Barrett EF, David G. Vesicular ATPase inserted into the plasma membrane of motor terminals by exocytosis alkalinizes cytosolic pH and facilitates endocytosis. Neuron 2011; 68:1097-108. [PMID: 21172612 DOI: 10.1016/j.neuron.2010.11.035] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2010] [Indexed: 01/29/2023]
Abstract
Key components of vesicular neurotransmitter release, such as Ca(2+) influx and membrane recycling, are affected by cytosolic pH. We measured the pH-sensitive fluorescence of Yellow Fluorescent Protein transgenically expressed in mouse motor nerve terminals, and report that Ca(2+) influx elicited by action potential trains (12.5-100 Hz) evokes a biphasic pH change: a brief acidification (∼ 13 nM average peak increase in [H(+)]), followed by a prolonged alkalinization (∼ 30 nM peak decrease in [H(+)]) that outlasts the stimulation train. The alkalinization is selectively eliminated by blocking vesicular exocytosis with botulinum neurotoxins, and is prolonged by the endocytosis-inhibitor dynasore. Blocking H(+) pumping by vesicular H(+)-ATPase (with folimycin or bafilomycin) suppresses stimulation-induced alkalinization and reduces endocytotic uptake of FM1-43. These results suggest that H(+)-ATPase, known to transfer cytosolic H(+) into prefused vesicles, continues to extrude cytosolic H(+) after being exocytotically incorporated into the plasma membrane. The resulting cytosolic alkalinization may facilitate vesicular endocytosis.
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Affiliation(s)
- Zhongsheng Zhang
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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109
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Maeda Y, Kinoshita T. The acidic environment of the Golgi is critical for glycosylation and transport. Methods Enzymol 2010; 480:495-510. [PMID: 20816224 DOI: 10.1016/s0076-6879(10)80022-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
Abstract
Proteins and glycolipids are modified by various modes of glycosylation in the endoplasmic reticulum (ER) and the Golgi apparatus. It is well known that the lumen of the Golgi is acidic and compromising acidification by chemical compounds causes impaired glycosylation and transport of proteins (Axelsson et al., 2001; Chapman and Munro, 1994; Palokangas et al., 1994; Presley et al., 1997; Puri et al., 2002; Reaves and Banting, 1994; Rivinoja et al., 2006; Tartakoff et al., 1978). The mechanisms by which glycosylation and transport are regulated by an acidic pH remain largely unknown. Recent findings that the impaired regulation of an acidic environment may be implicated in the pathology of several diseases emphasize the importance of pH regulation (Jentsch, 2007; Kasper et al., 2005; Kornak et al., 2001; Kornak et al., 2008; Piwon et al., 2000; Stobrawa et al., 2001; Teichgraber et al., 2008). We recently established a mutant cell line in which Golgi acidification was selectively impaired and the raised luminal Golgi pH caused impaired transport and glycosylation of proteins and altered Golgi morphology (Maeda et al., 2008). As alkalinizing compounds nonselectively affect all acidic organelles including lysosomes, endosomes, and the Golgi, the mutant cell is thought to be useful in analyzing how the acidic environment of the Golgi regulates glycosylation. In this chapter, we have introduced how we established mutant cells with impaired Golgi acidification and methods for measuring Golgi pH.
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Affiliation(s)
- Yusuke Maeda
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
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110
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Abstract
Cholesterol-engorged macrophage foam cells are a critical component of the atherosclerotic lesion. Reducing the sterol deposits in lesions reduces clinical events. Sterol accumulations within lysosomes have proven to be particularly hard to mobilize out of foam cells. Moreover, excess sterol accumulation in lysosomes has untoward effects, including a complete disruption of lysosome function. Recently, we demonstrated that treatment of sterol-engorged macrophages in culture with triglyceride-containing particles can reverse many of the effects of cholesterol on lysosomes and dramatically reduce the sterol burden in these cells. This article describes what is known about lysosomal sterol engorgement, discusses the possible mechanisms by which triglyceride could produce its effects, and evaluates the possible positive and negative effects of reducing the lysosomal cholesterol levels in foam cells.
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Affiliation(s)
- W Gray Jerome
- Department of Pathology, U-2206 Medical Center North Vanderbilt University School of Medicine 1161 21st Avenue, South Nashville, TN 37232-32561, USA, Tel.: +1 615 322 5530
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111
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Brignone MS, Lanciotti A, Macioce P, Macchia G, Gaetani M, Aloisi F, Petrucci TC, Ambrosini E. The beta1 subunit of the Na,K-ATPase pump interacts with megalencephalic leucoencephalopathy with subcortical cysts protein 1 (MLC1) in brain astrocytes: new insights into MLC pathogenesis. Hum Mol Genet 2010; 20:90-103. [PMID: 20926452 DOI: 10.1093/hmg/ddq435] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Megalencephalic leucoencephalopathy with subcortical cysts (MLC) is a rare congenital leucodystrophy caused by mutations in MLC1, a membrane protein of unknown function. MLC1 expression in astrocyte end-feet contacting blood vessels and meninges, along with brain swelling, fluid cysts and myelin vacuolation observed in MLC patients, suggests a possible role for MLC1 in the regulation of fluid and ion homeostasis and cellular volume changes. To identify MLC1 direct interactors and dissect the molecular pathways in which MLC1 is involved, we used NH2-MLC1 domain as a bait to screen a human brain library in a yeast two-hybrid assay. We identified the β1 subunit of the Na,K-ATPase pump as one of the interacting clones and confirmed it by pull-downs, co-fractionation assays and immunofluorescence stainings in human and rat astrocytes in vitro and in brain tissue. By performing ouabain-affinity chromatography on astrocyte and brain extracts, we isolated MLC1 and the whole Na,K-ATPase enzyme in a multiprotein complex that included Kir4.1, syntrophin and dystrobrevin. Because Na,K-ATPase is involved in intracellular osmotic control and volume regulation, we investigated the effect of hypo-osmotic stress on MLC1/Na,K-ATPase relationship in astrocytes. We found that hypo-osmotic conditions increased MLC1 membrane expression and favoured MLC1/Na,K-ATPase-β1 association. Moreover, hypo-osmosis induced astrocyte swelling and the reversible formation of endosome-derived vacuoles, where the two proteins co-localized. These data suggest that through its interaction with Na,K-ATPase, MLC1 is involved in the control of intracellular osmotic conditions and volume regulation in astrocytes, opening new perspectives for understanding the pathological mechanisms of MLC disease.
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Affiliation(s)
- Maria S Brignone
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Rome, Italy
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112
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Sodium or potassium efflux ATPase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1841-53. [DOI: 10.1016/j.bbamem.2010.07.009] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 07/06/2010] [Accepted: 07/13/2010] [Indexed: 12/20/2022]
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113
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Mechanisms for the intracellular manipulation of organelles by conventional electroporation. Biophys J 2010; 98:2506-14. [PMID: 20513394 DOI: 10.1016/j.bpj.2010.02.035] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 01/22/2010] [Accepted: 02/12/2010] [Indexed: 01/04/2023] Open
Abstract
Conventional electroporation (EP) changes both the conductance and molecular permeability of the plasma membrane (PM) of cells and is a standard method for delivering both biologically active and probe molecules of a wide range of sizes into cells. However, the underlying mechanisms at the molecular and cellular levels remain controversial. Here we introduce a mathematical cell model that contains representative organelles (nucleus, endoplasmic reticulum, mitochondria) and includes a dynamic EP model, which describes formation, expansion, contraction, and destruction for the plasma and all organelle membranes. We show that conventional EP provides transient electrical pathways into the cell, sufficient to create significant intracellular fields. This emerging intracellular electrical field is a secondary effect due to EP and can cause transmembrane voltages at the organelles, which are large enough and long enough to gate organelle channels, and even sufficient, at some field strengths, for the poration of organelle membranes. This suggests an alternative to nanosecond pulsed electric fields for intracellular manipulations.
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114
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Wang W, Zhou S, Guo L, Zhi W, Li X, Weng J. Investigation of endocytosis and cytotoxicity of poly-d, l-lactide-poly(ethylene glycol) micro/nano-particles in osteoblast cells. Int J Nanomedicine 2010; 5:557-66. [PMID: 20957117 PMCID: PMC2950413 DOI: 10.2147/ijn.s12089] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Indexed: 11/30/2022] Open
Abstract
Biodegradable polymer particles present a promising approach for intracellular delivery of drugs, proteins, and nucleic acids. Poly-d,l-lactide-poly(ethylene glycol) (PELA) copolymers with different weight ratios of polyethylene glycol (PEG) were used as drug carriers in the present study. PELA particles entrapped with fluorescein isothiocyanate (FITC) as a fluorescent marker were formulated using a double emulsion-solvent evaporation technique. The size and morphology of the particles were observed with scanning electron microscope (SEM), atomic force microscope (AFM), and laser diffraction particle size analyzer (LDPSA). The purpose in the present work was to investigate the cytotoxicity and the process of endocytosis of PELA particles with different contents of PEG and variable particle size using rat osteoblasts (OBs). The cytotoxicity of the particles was investigated using 5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. Results indicate that as the content of PEG in the polymer increased, so did cell survival. Endocytosis was observed through a light microscope and a fluorescence microscope; intracellular uptake and retention were determined quantitatively using fluorescence spectrophotometer (FSP). The results showed that as PEG content in PELA copolymer increased, there was a reduction in endocytosis of nanoparticles in osteoblasts.
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Affiliation(s)
- Weijia Wang
- School of Materials Science and Engineering, Key Laboratory of Advanced Technologies of Material, Ministry of Education, Southwest Jiaotong University, Chengdou, Sichuan, People's Republic of China
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115
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Weinert S, Jabs S, Supanchart C, Schweizer M, Gimber N, Richter M, Rademann J, Stauber T, Kornak U, Jentsch TJ. Lysosomal pathology and osteopetrosis upon loss of H+-driven lysosomal Cl- accumulation. Science 2010; 328:1401-3. [PMID: 20430974 DOI: 10.1126/science.1188072] [Citation(s) in RCA: 190] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
During lysosomal acidification, proton-pump currents are thought to be shunted by a chloride ion (Cl-) channel, tentatively identified as ClC-7. Surprisingly, recent data suggest that ClC-7 instead mediates Cl-/proton (H+) exchange. We generated mice carrying a point mutation converting ClC-7 into an uncoupled (unc) Cl- conductor. Despite maintaining lysosomal conductance and normal lysosomal pH, these Clcn7(unc/unc) mice showed lysosomal storage disease like mice lacking ClC-7. However, their osteopetrosis was milder, and they lacked a coat color phenotype. Thus, only some roles of ClC-7 Cl-/H+ exchange can be taken over by a Cl- conductance. This conductance was even deleterious in Clcn7(+/unc) mice. Clcn7(-/-) and Clcn7(unc/unc) mice accumulated less Cl- in lysosomes than did wild-type mice. Thus, lowered lysosomal chloride may underlie their common phenotypes.
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Affiliation(s)
- Stefanie Weinert
- Leibniz-Institut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
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116
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Deka SR, Quarta A, Di Corato R, Falqui A, Manna L, Cingolani R, Pellegrino T. Acidic pH-responsive nanogels as smart cargo systems for the simultaneous loading and release of short oligonucleotides and magnetic nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:10315-10324. [PMID: 20355740 DOI: 10.1021/la1004819] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Smart materials able to sense environmental stimuli can be exploited as intelligent carrier systems. Acidic pH-responsive polymers, for instance, exhibit a variation in the ionization state upon lowering the pH, which leads to their swelling. The different permeability of these polymers as a function of the pH could be exploited for the incorporation and subsequent release of previously trapped payload molecules/nanoparticles. We provide here a proof of concept of a novel use of pH-responsive polymer nanostructures based on 2-vinylpyridine and divinylbenzene, having an overall size below 200 nm, as cargo system for magnetic nanoparticles, for oligonucleotide sequences, as well as for their simultaneous loading and controlled release mediated by the pH.
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Affiliation(s)
- Smriti R Deka
- Istituto Italiano di Tecnologia, via Morego 30, 16163, Genova, Italy
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117
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Park IK, Singha K, Arote RB, Choi YJ, Kim WJ, Cho CS. pH-Responsive Polymers as Gene Carriers. Macromol Rapid Commun 2010; 31:1122-33. [PMID: 21590865 DOI: 10.1002/marc.200900867] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 02/05/2010] [Indexed: 11/05/2022]
Abstract
Despite the immense potential of non-viral delivery system in gene therapy its application has been impaired greatly by various impediments having contrasting traits. Therefore it is an absolute necessity to develop some non-viral vectors which are endowed with special characteristics to act differently in intracellular as well as extracellular compartments to surmount these inter-conflicting hurdles. Such smart polymers should serve some specific purposes by adjusting their structural or functional traits under the influence of stimuli such as temperature, light, salt concentration or pH. Among all these stimuli-responsive polymers pH-responsive polymers have attracted major attention and great impetus has been directed towards utilizing the subtle yet significant change in pH value within the cellular compartments. This review is intended to provide a comprehensive account of the development of pH-responsive polymeric vectors based on their structural features and consequent functional attributes to achieve efficient transfection. The underlying modes of actions relating to structure and differential pH environment have also been discussed in this review.
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Affiliation(s)
- In-Kyu Park
- Department of Biomedical Sciences, Chonnam National University Medical School, Chonnam National University, Gwangju 501-746, Korea
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118
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Cherng JY, Lee YP, Lin CH, Chang KH, Chang WY, Shau MD. The characteristics and transfection efficiency of PEI modified by biodegradable poly(beta-amino ester). JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2010; 21:1543-1551. [PMID: 20135203 DOI: 10.1007/s10856-010-4004-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Accepted: 01/16/2010] [Indexed: 05/28/2023]
Abstract
To improve the cytotoxicity of PEI25k and the transfection efficiency of poly(beta-amino ester) with DNA, we synthesized a poly(beta-amino ester), PEDP, bearing ester linkages in the backbone and tertiary amines in the backbone and side chain and prepared a binary mixture, PEDP-PEI25k, using physical blending meyhod. Both poly(beta-amino ester) PEDP and binary mixture PEDP-PEI25k, readily self-assembled with plasmid DNA (pCMV-beta gal) in a HEPES buffer, were characterized by dynamic light scattering. The results reveal that PEDP-PEI25k was able to self-assemble plasmid DNA into PEDP-PEI25k/DNA nano-complexes small enough to enter a cell through endocytosis. Titration studies were performed to determine the buffering capacities of PEDP and PEDP-PEI25k. The COS-7 cell viabilities in the presence of PEDP and PEDP-PEI25k were studied. At low mass ratio of PEDP/PEI25k (1/1), it is found that the transfection curve of PEDP-PEI25k/DNA bearing a maximum peak is similar to that of PEI25k/DNA. In addition, the PEDP-PEI25k/DNA complexes were able to transfect COS-7 cells in vitro with a high efficiency comparable to a well-known gene carrier PEI25k/DNA. The results indicate that binary mixture PEDP-PEI25k is an attractive cationic carrier for gene delivery and an interesting candidate for further study.
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Affiliation(s)
- Jong-Yuh Cherng
- Department of Chemistry and Biochemistry, National Chung Cheng University, 168 University Rd., Min-Hsiung Chia-Yi, Taiwan, ROC
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119
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Wang H, Mao Y, Zhang B, Wang T, Li F, Fu S, Xue Y, Yang T, Wen X, Ding Y, Duan X. Chloride channel ClC-3 promotion of osteogenic differentiation through Runx2. J Cell Biochem 2010; 111:49-58. [DOI: 10.1002/jcb.22658] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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120
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Deriy LV, Gomez EA, Zhang G, Beacham DW, Hopson JA, Gallan AJ, Shevchenko PD, Bindokas VP, Nelson DJ. Disease-causing mutations in the cystic fibrosis transmembrane conductance regulator determine the functional responses of alveolar macrophages. J Biol Chem 2010; 284:35926-38. [PMID: 19837664 DOI: 10.1074/jbc.m109.057372] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Alveolar macrophages (AMs) play a major role in host defense against microbial infections in the lung. To perform this function, these cells must ingest and destroy pathogens, generally in phagosomes, as well as secrete a number of products that signal other immune cells to respond. Recently, we demonstrated that murine alveolar macrophages employ the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel as a determinant in lysosomal acidification (Di, A., Brown, M. E., Deriy, L. V., Li, C., Szeto, F. L., Chen, Y., Huang, P., Tong, J., Naren, A. P., Bindokas, V., Palfrey, H. C., and Nelson, D. J. (2006) Nat. Cell Biol. 8, 933-944). Lysosomes and phagosomes in murine cftr(-/-) AMs failed to acidify, and the cells were deficient in bacterial killing compared with wild type controls. Cystic fibrosis is caused by mutations in CFTR and is characterized by chronic lung infections. The information about relationships between the CFTR genotype and the disease phenotype is scarce both on the organismal and cellular level. The most common disease-causing mutation, DeltaF508, is found in 70% of patients with cystic fibrosis. The mutant protein fails to fold properly and is targeted for proteosomal degradation. G551D, the second most common mutation, causes loss of function of the protein at the plasma membrane. In this study, we have investigated the impact of CFTR DeltaF508 and G551D on a set of core intracellular functions, including organellar acidification, granule secretion, and microbicidal activity in the AM. Utilizing primary AMs from wild type, cftr(-/-), as well as mutant mice, we show a tight correlation between CFTR genotype and levels of lysosomal acidification, bacterial killing, and agonist-induced secretory responses, all of which would be expected to contribute to a significant impact on microbial clearance in the lung.
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Affiliation(s)
- Ludmila V Deriy
- Department of Neurobiology, Pharmacology, and Physiology, University of Chicago, Chicago, Illinois 60637, USA
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121
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Kolter T, Sandhoff K. Lysosomal degradation of membrane lipids. FEBS Lett 2009; 584:1700-12. [PMID: 19836391 DOI: 10.1016/j.febslet.2009.10.021] [Citation(s) in RCA: 201] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 10/09/2009] [Indexed: 01/05/2023]
Abstract
The constitutive degradation of membrane components takes place in the acidic compartments of a cell, the endosomes and lysosomes. Sites of lipid degradation are intralysosomal membranes that are formed in endosomes, where the lipid composition is adjusted for degradation. Cholesterol is sorted out of the inner membranes, their content in bis(monoacylglycero)phosphate increases, and, most likely, sphingomyelin is degraded to ceramide. Together with endosomal and lysosomal lipid-binding proteins, the Niemann-Pick disease, type C2-protein, the GM2-activator, and the saposins sap-A, -B, -C, and -D, a suitable membrane lipid composition is required for degradation of complex lipids by hydrolytic enzymes.
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Affiliation(s)
- Thomas Kolter
- LiMES - Life and Medical Sciences Institute, Membrane Biology and Lipid Biochemistry Unit, c/o Kekulé-Institut für Organische Chemie und Biochemie, University of Bonn, Bonn, Germany
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Pennisi CP, Greenbaum E, Yoshida K. Analysis of light-induced transmembrane ion gradients and membrane potential in Photosystem I proteoliposomes. Biophys Chem 2009; 146:13-24. [PMID: 19854559 DOI: 10.1016/j.bpc.2009.09.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 09/25/2009] [Accepted: 09/27/2009] [Indexed: 10/20/2022]
Abstract
Photosystem I (PSI) complexes can support a light-driven electrochemical gradient for protons, which is the driving force for energy-conserving reactions across biological membranes. In this work, a computational model that enables a quantitative description of the light-induced proton gradients across the membrane of PSI proteoliposomes is presented. Using a set of electrodiffusion equations, a compartmental model of a vesicle suspended in aqueous medium was studied. The light-mediated proton movement was modeled as a single proton pumping step with backpressure of the electric potential. The model fits determinations of pH obtained from PSI proteoliposomes illuminated in the presence of mediators of cyclic electron transport. The model also allows analysis of the proton gradients in relation to the transmembrane ion fluxes and electric potential. Sensitivity analysis enabled a determination of the parameters that have greater influence on steady-state levels and onset/decay rates of transmembrane pH and electric potential. This model could be used as a tool for optimizing PSI proteoliposomes for photo-electrochemical applications.
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Affiliation(s)
- Cristian Pablo Pennisi
- Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Denmark.
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123
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Kneipp J, Kneipp H, Wittig B, Kneipp K. Novel optical nanosensors for probing and imaging live cells. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2009; 6:214-26. [PMID: 19699322 DOI: 10.1016/j.nano.2009.07.009] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 07/16/2009] [Accepted: 07/19/2009] [Indexed: 10/20/2022]
Abstract
UNLABELLED This review introduces multifunctional optical nanosensors based on surface-enhanced Raman scattering (SERS) and demonstrates their application in live cells. The novel nanosensors have the potential to improve our understanding of cellular processes on the molecular level. The hybrid sensor consists of gold or silver nanoparticles with an attached reporter species. The sensor can be detected and imaged based on the SERS signature of the reporter. This results in several advantages, such as high spectral specificity, multiplex capabilities, improved contrast, and photostability. SERS sensors not only highlight cellular structures, based on enhanced Raman spectra of intrinsic cellular molecules measured in the local optical fields of the gold nanoparticles, they also provide molecular structural information on their cellular environment. Moreover, the SERS signature of the reporter can deliver information on the local pH value inside a cell at subendosomal resolution. SERS sensors are suitable for one- and two-photon excitation. FROM THE CLINICAL EDITOR This review introduces multifunctional optical nanosensors based on surface enhanced Raman scattering (SERS) and demonstrates their application in live cells. These hybrid sensors consist of gold or silver nanoparticles with an attached reporter species. The sensor can be detected and imaged based on the SERS signature of the reporter. SERS sensors highlight cellular structures and provide molecular structural information on their cellular environment. They can also deliver information on the intracellular pH-value at subendosomal resolution.
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Affiliation(s)
- Janina Kneipp
- Department of Chemistry, Humboldt University, Berlin, Germany.
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Zhang X, Jin Y, Plummer MR, Pooyan S, Gunaseelan S, Sinko PJ. Endocytosis and membrane potential are required for HeLa cell uptake of R.I.-CKTat9, a retro-inverso Tat cell penetrating peptide. Mol Pharm 2009; 6:836-48. [PMID: 19278221 DOI: 10.1021/mp800121f] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cell-penetrating peptides (CPPs) can enter many types of cells and have become useful tools for introducing a variety of cargo such as exogenous peptides, proteins, and nucleic acids into cultured cells in vitro. Tat CPPs derived from the HIV-1 Tat protein are the most widely used among the arginine-rich CPPs. Even though CPPs hold considerable promise for drug delivery, poor biological stability and high in vivo clearance may limit their effectiveness for delivering cargo. Therefore, we utilize a retro-inverso form of a Tat peptide, R.I.-CKTat9, which is proteolytically stable. In the current study, the cellular entry mechanism of this arginine-rich CPP is investigated. Fluorescently labeled R.I.-CKTat9 entered HeLa cells in a concentration- and energy-dependent manner demonstrating both diffuse and punctate (vesicular) appearance inside the cells. The labeled R.I.-CKTat9 colocalized with labeled transferrin in the punctate structure, suggesting that the peptide enters HeLa cells by clathrin-dependent endocytosis. Incubation of cells with an isotonic/high K(+) buffer (KPBS) or an NH(4)Cl solution abolished the diffuse but not the punctate fluorescence, suggesting that membrane potential plays a critical role. This result also suggests that the flux originates from the endosome, not the extracellular space, and relies on the acidity of the endosome. Impairment of clathrin-mediated endocytosis by RNAi with clathrin heavy chain function and endocytosis inhibitors greatly reduced or completely abolished both diffuse and punctate fluorescence, further supporting a single route of endocytosis and subsequent endosomal escape. Since cells in the mitotic (M) phase shut down endocytosis but maintain plasma membrane potential, this property was used to further confirm the endocytic mechanism. Direct measurement of plasma membrane potential confirmed its persistence in M phase arrested HeLa cells. Consistent with our working hypothesis, these cells did not show any vesicular nor diffuse fluorescence of labeled R.I.-CKTat9, providing compelling evidence for the sequential steps of endocytosis and endosomal escape. Binding of labeled R.I.-CKTat9 to the surface of HeLa cells at 0 degrees C was reduced under the mildly acidic conditions of early endosomes, suggesting an acidity-dependent endosomal escape mechanism. Overall, these results indicate that both endocytosis and membrane potential are required for R.I.-CKTat9 entry into HeLa cells and suggest that translocation occurs at the endosomal membrane.
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Affiliation(s)
- Xiaoping Zhang
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
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125
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Lamb FS, Moreland JG, Miller FJ. Electrophysiology of reactive oxygen production in signaling endosomes. Antioxid Redox Signal 2009; 11:1335-47. [PMID: 19207039 PMCID: PMC2872256 DOI: 10.1089/ars.2008.2448] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Endosome trafficking and function require acidification by the vacuolar ATPase (V-ATPase). Electrogenic proton (H+) transport reduces the pH and creates a net positive charge in the endosomal lumen. Concomitant chloride (Cl-) influx has been proposed to occur via ClC Cl-=H+ exchangers. This maintains charge balance and drives Cl- accumulation, which may itself be critical to endosome function. Production of reactive oxygen species (ROS) in response to cytokines occurs within specialized endosomes that form in response to receptor occupation. ROS production requires an NADPH oxidase (Nox) and the ClC-3 Cl-=H+ exchanger. Like the V-ATPase, Nox activity is highly electrogenic, but separates charge with an opposite polarity (lumen negative). Here we review established paradigms of early endosomal ion transport focusing on the relation between the V-ATPase and ClC proteins. Electrophysiologic constraints on Nox-mediated vesicular ROS production are then considered. The potential for ClC-3 to participate in charge neutralization of both proton (V-ATPase) and electron (Nox) transport is discussed. It is proposed that uncompensated charge separation generated by Nox enzymatic activity could be used to drive secondary transport into negatively charged vesicles. Further experimentation will be necessary to establish firmly the biochemistry and functional implications of endosomal ROS production.
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Affiliation(s)
- Fred S Lamb
- Department of Pediatrics, University of Iowa Hospitals and Clinics, University of Iowa Children's Hospital, and Department of Veterans Affairs Medical Center, Iowa City, Iowa 52242, USA.
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126
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Barriere H, Bagdany M, Bossard F, Okiyoneda T, Wojewodka G, Gruenert D, Radzioch D, Lukacs GL. Revisiting the role of cystic fibrosis transmembrane conductance regulator and counterion permeability in the pH regulation of endocytic organelles. Mol Biol Cell 2009; 20:3125-41. [PMID: 19420138 DOI: 10.1091/mbc.e09-01-0061] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Organellar acidification by the electrogenic vacuolar proton-ATPase is coupled to anion uptake and cation efflux to preserve electroneutrality. The defective organellar pH regulation, caused by impaired counterion conductance of the mutant cystic fibrosis transmembrane conductance regulator (CFTR), remains highly controversial in epithelia and macrophages. Restricting the pH-sensitive probe to CFTR-containing vesicles, the counterion and proton permeability, and the luminal pH of endosomes were measured in various cells, including genetically matched CF and non-CF human respiratory epithelia, as well as cftr(+/+) and cftr(-/-) mouse alveolar macrophages. Passive proton and relative counterion permeabilities, determinants of endosomal, lysosomal, and phagosomal pH-regulation, were probed with FITC-conjugated transferrin, dextran, and Pseudomonas aeruginosa, respectively. Although CFTR function could be documented in recycling endosomes and immature phagosomes, neither channel activation nor inhibition influenced the pH in any of these organelles. CFTR heterologous overexpression also failed to alter endocytic organellar pH. We propose that the relatively large CFTR-independent counterion and small passive proton permeability ensure efficient shunting of the proton-ATPase-generated membrane potential. These results have implications in the regulation of organelle acidification in general and demonstrate that perturbations of the endolysosomal organelles pH homeostasis cannot be linked to the etiology of the CF lung disease.
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Affiliation(s)
- Herve Barriere
- Department of Physiology, McGill University, Montreal, Quebec, H3G 1Y6, Canada
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127
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Venugopal B, Mesires NT, Kennedy JC, Curcio-Morelli C, Laplante JM, Dice JF, Slaugenhaupt SA. Chaperone-mediated autophagy is defective in mucolipidosis type IV. J Cell Physiol 2009; 219:344-53. [PMID: 19117012 DOI: 10.1002/jcp.21676] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Mucolipidosis type IV (MLIV) is a lysosomal storage disorder caused by mutations in the MCOLN1 gene, a member of the transient receptor potential (TRP) cation channel gene family. The encoded protein, transient receptor potential mucolipin-1 (TRPML1), has been localized to lysosomes and late endosomes but the pathogenic mechanism by which loss of TRPML1 leads to abnormal cellular storage and neuronal cell death is still poorly understood. Yeast two-hybrid and co-immunoprecipitation (coIP) experiments identified interactions between TRPML1 and Hsc70 as well as TRPML1 and Hsp40. Hsc70 and Hsp40 are members of a molecular chaperone complex required for protein transport into the lysosome during chaperone-mediated autophagy (CMA). To determine the functional relevance of this interaction, we compared fibroblasts from MLIV patients to those from sex- and age-matched controls and show a defect in CMA in response to serum withdrawal. This defect in CMA was subsequently confirmed in purified lysosomes isolated from control and MLIV fibroblasts. We further show that the amount of lysosomal-associated membrane protein type 2A (LAMP-2A) is reduced in lysosomal membranes of MLIV fibroblasts. As a result of decreased CMA, MLIV fibroblasts have increased levels of oxidized proteins compared to control fibroblasts. We hypothesize that TRPML1 may act as a docking site for intralysosomal Hsc70 (ly-Hsc70) allowing it to more efficiently pull in substrates for CMA. It is also possible that TRPML1 channel activity may be required for CMA. Understanding the role of TRPML1 in CMA will undoubtedly help to characterize the pathogenesis of MLIV.
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Affiliation(s)
- Bhuvarahamurthy Venugopal
- Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
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128
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Meng F, Zhong Z, Feijen J. Stimuli-responsive polymersomes for programmed drug delivery. Biomacromolecules 2009; 10:197-209. [PMID: 19123775 DOI: 10.1021/bm801127d] [Citation(s) in RCA: 851] [Impact Index Per Article: 56.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the past decade, polymersomes (also referred to as polymeric vesicles) have attracted rapidly growing interest based on their intriguing aggregation phenomena, cell and virus-mimicking dimensions and functions, as well as tremendous potential applications in medicine, pharmacy, and biotechnology. Unlike liposomes self-assembled from low molecular weight lipids, polymersomes are in general prepared from macromolecular amphiphiles of various architectures including amphiphilic diblock, triblock, graft and dendritic copolymers. Polymersomes exhibit very unique features highlighted with high stability, tunable membrane properties, versatility, and capacity of transporting hydrophilic as well as hydrophobic species such as anticancer drugs, genes, proteins, and diagnostic probes. Recently, much effort has been directed to the development of intelligent polymersomes that respond to internal or external stimuli, in particular, pH, temperature, redox potential, light, magnetic field, and ultrasound, either reversibly or nonreversibly. Stimuli-sensitive polymersomes have emerged as novel programmable delivery systems in which the release of the encapsulated contents can be readily modulated by the stimulus. The stimuli-responsive release may result in significantly enhanced therapeutic efficacy and minimized possible side effects. It is also feasible to form and disassemble polymersomes in water simply by applying an appropriate stimulus. In this article, recent advances in stimuli-sensitive polymersomes have been reviewed, and perspectives on future developments have been discussed.
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Affiliation(s)
- Fenghua Meng
- Biomedical Polymers Laboratory, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, People's Republic of China
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129
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Neutralization of endomembrane compartments in epithelial MDCK cells affects proteoglycan synthesis in the apical secretory pathway. Biochem J 2009; 418:517-28. [DOI: 10.1042/bj20081179] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PGs (proteoglycans) are proteins acquiring long, linear and sulfated GAG (glycosaminoglycan) chains during Golgi passage. In MDCK cells (Madin–Darby canine kidney cells), most of the CS (chondroitin sulfate) PGs are secreted apically, whereas most of the HS (heparan sulfate) PGs are secreted basolaterally. The apical and basolateral secretory routes differ in their GAG synthesis, since a protein core that traverses both routes acquires shorter chains, but more sulfate, in the basolateral pathway than in the apical counterpart [Tveit, Dick, Skibeli and Prydz (2005) J. Biol. Chem. 280, 29596–29603]. Golgi cisternae and the trans-Golgi network have slightly acidic lumens. We therefore investigated how neutralization of endomembrane compartments with the vacuolar H+-ATPase inhibitor Baf A1 (bafilomycin A1) affected GAG synthesis and PG sorting in MDCK cells. Baf A1 induced a slight reduction in basolateral secretion of macromolecules, which was compensated by an apical increase. More dramatic changes occurred to PG synthesis in the apical pathway on neutralization. The difference in apical and basolateral PG sulfation levels observed for control cells was abolished, due to enhanced sulfation of apical CS-GAGs. In addition, a large fraction of apical HS-GAGs was elongated to longer chain lengths. The differential sensitivity of the apical and basolateral secretory pathways to Baf A1 indicates that the apical pathway is more acidic than the basolateral counterpart in untreated MDCK cells. Neutralization gave an apical GAG output that was more similar to that of the basolateral pathway, suggesting that neutralization made the luminal environments of the two pathways more similar.
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130
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Human rhinovirus type 2 uncoating at the plasma membrane is not affected by a pH gradient but is affected by the membrane potential. J Virol 2009; 83:3778-87. [PMID: 19193784 DOI: 10.1128/jvi.01739-08] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The minor receptor group human rhinovirus type 2 enters host cells by endocytosis via members of the low-density-lipoprotein receptor family. In late endosomes, it undergoes a conformational change solely induced by a pH of < or =5.6, resulting in RNA transfer across the endosomal membrane into the cytoplasm. To determine potential driving forces of this process, we investigated whether RNA penetration might depend on the pH gradient and/or the membrane potential between the acidic endosome lumen and the neutral cytoplasm. Since these parameters are difficult to assess in endosomes, we took advantage of the possibility of inducing structural changes, RNA release, and consequently infection from the plasma membrane. To manipulate the pH gradient, cell-bound virus was exposed to membrane-permeant or -impermeant acidic buffers at 4 degrees C, and this was followed by a shift to 34 degrees C in medium containing bafilomycin to prevent RNA release from endosomes. To manipulate the plasma membrane potential, similar experiments were carried out, but these included K(+) diffusion potentials in the presence of the K(+) ionophore valinomycin. We demonstrated that infection does not depend on a pH gradient but is enhanced by plasma membrane hyperpolarization compared to plasma membrane depolarization.
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131
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Nam HY, Kwon SM, Chung H, Lee SY, Kwon SH, Jeon H, Kim Y, Park JH, Kim J, Her S, Oh YK, Kwon IC, Kim K, Jeong SY. Cellular uptake mechanism and intracellular fate of hydrophobically modified glycol chitosan nanoparticles. J Control Release 2009; 135:259-67. [PMID: 19331853 DOI: 10.1016/j.jconrel.2009.01.018] [Citation(s) in RCA: 431] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Revised: 01/07/2009] [Accepted: 01/16/2009] [Indexed: 12/16/2022]
Abstract
Polymeric nanoparticle-based carriers are promising agents for the targeted delivery of therapeutics to the intracellular site of action. To optimize the efficacy in delivery, often the tuning of physicochemical properties (i.e., particle size, shape, surface charge, lipophilicity, etc.) is necessary, in a manner specific to each type of nanoparticle. Recent studies showed an efficient tumor targeting by hydrophobically modified glycol chitosan (HGC) nanoparticles through the enhanced permeability and retention (EPR) effect. As a continued effort, here the investigations on the cellular uptake mechanism and the intracellular fate of the HGC nanoparticles are reported. The HGC nanoparticle, prepared by a partial derivatization of the free amino groups of glycol chitosan (GC) with 5beta-cholanic acid, had a globular shape with the average diameter of 359 nm and the zeta potential of ca. 22 mV. Interestingly, these nanoparticles showed an enhanced distribution in the whole cells, compared to the parent hydrophilic GC polymers. In vitro experiments with endocytic inhibitors suggested that several distinct uptake pathways (e.g., clathrin-mediated endocytosis, caveolae-mediated endocytosis, and macropinocytosis) are involved in the internalization of HGC. Some HGC nanoparticles were found entrapped in the lysosomes upon entry, as determined by TEM and colocalization studies. Given such favorable properties including low toxicity, biocompatibility, and fast uptake by several nondestructive endocytic pathways, our HGC nanoparticles may serve as a versatile carrier for the intracellular delivery of therapeutic agents.
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Affiliation(s)
- Hae Yun Nam
- Biomedical Research Center, Korea Institute of Science and Technology, 39-1 Hawolgok-dong, Seongbuk-gu, Seoul 136-791, South South Korea
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Schulze H, Kolter T, Sandhoff K. Principles of lysosomal membrane degradation: Cellular topology and biochemistry of lysosomal lipid degradation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1793:674-83. [PMID: 19014978 DOI: 10.1016/j.bbamcr.2008.09.020] [Citation(s) in RCA: 180] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Revised: 09/24/2008] [Accepted: 09/30/2008] [Indexed: 12/17/2022]
Abstract
Cellular membranes enter the lysosomal compartment by endocytosis, phagocytosis, or autophagy. Within the lysosomal compartment, membrane components of complex structure are degraded into their building blocks. These are able to leave the lysosome and can then be utilized for the resynthesis of complex molecules or can be further degraded. Constitutive degradation of membranes occurs on the surface of intra-endosomal and intra-lysosomal membrane structures. Many integral membrane proteins are sorted to the inner membranes of endosomes and lysosome after ubiquitinylation. In the lysosome, proteins are degraded by proteolytic enzymes, the cathepsins. Phospholipids originating from lipoproteins or cellular membranes are degraded by phospholipases. Water-soluble glycosidases sequentially cleave off the terminal carbohydrate residues of glycoproteins, glycosaminoglycans, and glycosphingolipids. For glycosphingolipids with short oligosaccharide chains, the additional presence of membrane-active lysosomal lipid-binding proteins is required. The presence of lipid-binding proteins overcomes the phase problem of water soluble enzymes and lipid substrates by transferring the substrate to the degrading enzyme or by solubilizing the internal membranes. The lipid composition of intra-lysosomal vesicles differs from that of the plasma membrane. To allow at least glycosphingolipid degradation by hydrolases and activator proteins, the cholesterol content of these intraorganellar membranes decreases during endocytosis and the concentration of bis(monoacylglycero)phosphate, a stimulator of sphingolipid degradation, increases. A considerable part of our current knowledge about mechanism and biochemistry of lysosomal lipid degradation is derived from a class of human diseases, the sphingolipidoses, which are caused by inherited defects within sphingolipid and glycosphingolipid catabolism.
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Affiliation(s)
- Heike Schulze
- LIMES Program Unit Membrane Biology and Lipid Biochemistry, Laboratory of Lipid Biochemistry, Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn, Germany
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133
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Ahmed KH, Pelster B. Ionic determinants of pH of acidic compartments under hypertonic conditions in trout hepatocytes. J Exp Biol 2008; 211:3306-14. [PMID: 18840665 DOI: 10.1242/jeb.020776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Exposure of trout hepatocytes to hypertonicity induced a decrease in acridine orange (AO) fluorescence, indicating a corresponding decrease in pH inside the lumen of acidic compartments (pH(L)). Pre-exposure of cells to the specific V-ATPase inhibitor bafilomycin A1 (0.3 micromol l(-1)) increased AO fluorescence - unmasking H(+) leaks under steady-state conditions - and partially removed the hypertonicity-induced pH(L) decrease. The sustainability of the luminal acidification, but not the acidification itself, appeared to depend on a low K(+) and a high Cl(-) conductance under hypertonic conditions. Increasing K(+) conductance using the specific ionophore valinomycin (10 micromol l(-1)) or removal of extracellular Cl(-) after an instant drop in AO fluorescence resulted in a reversal of luminal acidity. The alkalinization measured under hypertonic conditions in the absence of Cl(-) was largely attenuated when cells were bathed in HCO(3)(-)-free medium, signifying the possible presence of Cl(-)/HCO(3)(-) exchange. Under steady-state conditions, while a slight and brief pH(L) increase was measured upon exposure of cells to valinomycin, Cl(-) removal, unexpectedly, induced a decrease in pH(L), indicating a role for extracellular Cl(-) in limiting luminal acidification. This was confirmed by the substantial pH(L) decrease measured upon exposure of cells to the anion exchanger inhibitor SITS (0.5 mmol l(-1)). Furthermore, hypertonicity-induced acidification was still noticeable in the presence of SITS. On the other hand, the hypertonicity-induced acidification was significantly reduced in the absence of extracellular Na(+) or Ca(2+). However, BAPTA-AM induced an increase in steady-state pH(L) that was independent of V-ATPase inhibition. Moreover, the BAPTA-induced alkalinization was still apparent after depletion of intracellular Ca(2+) using the Ca(2+) ionophore A23187 in Ca(2+)-free medium. We conclude that pH(L) of trout hepatocytes is sensitive to hypertonicity and ionic determinants of hypertonicity. Thus, changes in pH(L) should be considered when studying pH adaptations to hypertonic stress.
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Affiliation(s)
- Khaled H Ahmed
- Institut für Zoologie and Center of Molecular Biosciences, Leopold Franzens Universität Innsbruck, Innsbruck, Austria
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134
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Maeda Y, Ide T, Koike M, Uchiyama Y, Kinoshita T. GPHR is a novel anion channel critical for acidification and functions of the Golgi apparatus. Nat Cell Biol 2008; 10:1135-45. [PMID: 18794847 DOI: 10.1038/ncb1773] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Accepted: 08/20/2008] [Indexed: 01/26/2023]
Abstract
The organelles within secretory and endocytotic pathways in mammalian cells have acidified lumens, and regulation of their acidic pH is critical for the trafficking, processing and glycosylation of cargo proteins and lipids, as well as the morphological integrity of the organelles. How organelle lumen acidification is regulated, and how luminal pH elevation disturbs these fundamental cellular processes, is largely unknown. Here, we describe a novel molecule involved in Golgi acidification. First, mutant cells defective in Golgi acidification were established that exhibited delayed protein transport, impaired glycosylation and Golgi disorganization. Using expression cloning, a novel Golgi-resident multi-transmembrane protein, named Golgi pH regulator (GPHR), was identified as being responsible for the mutant cells. After reconstitution in planar lipid bilayers, GPHR exhibited a voltage-dependent anion-channel activity that may function in counterion conductance. Thus, GPHR modulates Golgi functions through regulation of acidification.
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Affiliation(s)
- Yusuke Maeda
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
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135
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Lafourcade C, Sobo K, Kieffer-Jaquinod S, Garin J, van der Goot FG. Regulation of the V-ATPase along the endocytic pathway occurs through reversible subunit association and membrane localization. PLoS One 2008; 3:e2758. [PMID: 18648502 PMCID: PMC2447177 DOI: 10.1371/journal.pone.0002758] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Accepted: 06/20/2008] [Indexed: 01/06/2023] Open
Abstract
The lumen of endosomal organelles becomes increasingly acidic when going from the cell surface to lysosomes. Luminal pH thereby regulates important processes such as the release of internalized ligands from their receptor or the activation of lysosomal enzymes. The main player in endosomal acidification is the vacuolar ATPase (V-ATPase), a multi-subunit transmembrane complex that pumps protons from the cytoplasm to the lumen of organelles, or to the outside of the cell. The active V-ATPase is composed of two multi-subunit domains, the transmembrane V0 and the cytoplasmic V1. Here we found that the ratio of membrane associated V1/Vo varies along the endocytic pathway, the relative abundance of V1 being higher on late endosomes than on early endosomes, providing an explanation for the higher acidity of late endosomes. We also found that all membrane-bound V-ATPase subunits were associated with detergent resistant membranes (DRM) isolated from late endosomes, raising the possibility that association with lipid-raft like domains also plays a role in regulating the activity of the proton pump. In support of this, we found that treatment of cells with U18666A, a drug that leads to the accumulation of cholesterol in late endosomes, affected acidification of late endosome. Altogether our findings indicate that the activity of the vATPase in the endocytic pathway is regulated both by reversible association/dissociation and the interaction with specific lipid environments.
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Affiliation(s)
- Céline Lafourcade
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Faculty of Life Sciences, Lausanne, Switzerland
| | - Komla Sobo
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Faculty of Life Sciences, Lausanne, Switzerland
| | - Sylvie Kieffer-Jaquinod
- CEA, DSV, iRTSV, Laboratoire d'Etude de la Dynamique des Protéomes, INSERM U880, Grenoble, France
| | - Jérome Garin
- CEA, DSV, iRTSV, Laboratoire d'Etude de la Dynamique des Protéomes, INSERM U880, Grenoble, France
| | - F. Gisou van der Goot
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Faculty of Life Sciences, Lausanne, Switzerland
- * E-mail:
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136
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Martínez-Muñoz GA, Kane P. Vacuolar and plasma membrane proton pumps collaborate to achieve cytosolic pH homeostasis in yeast. J Biol Chem 2008; 283:20309-19. [PMID: 18502746 DOI: 10.1074/jbc.m710470200] [Citation(s) in RCA: 209] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vacuolar proton-translocating ATPases (V-ATPases) play a central role in organelle acidification in all eukaryotic cells. To address the role of the yeast V-ATPase in vacuolar and cytosolic pH homeostasis, ratiometric pH-sensitive fluorophores specific for the vacuole or cytosol were introduced into wild-type cells and vma mutants, which lack V-ATPase subunits. Transiently glucose-deprived wild-type cells respond to glucose addition with vacuolar acidification and cytosolic alkalinization, and subsequent addition of K(+) ion increases the pH of both the vacuole and cytosol. In contrast, glucose addition results in an increase in vacuolar pH in both vma mutants and wild-type cells treated with the V-ATPase inhibitor concanamycin A. Cytosolic pH homeostasis is also significantly perturbed in the vma mutants. Even at extracellular pH 5, conditions optimal for their growth, cytosolic pH was much lower, and response to glucose was smaller in the mutants. In plasma membrane fractions from the vma mutants, activity of the plasma membrane proton pump, Pma1p, was 65-75% lower than in fractions from wild-type cells. Immunofluorescence microscopy confirmed decreased levels of plasma membrane Pma1p and increased Pma1p at the vacuole and other compartments in the mutants. Pma1p was not mislocalized in concanamycin-treated cells, but a significant reduction in cytosolic pH under all conditions was still observed. We propose that short-term, V-ATPase activity is essential for both vacuolar acidification in response to glucose metabolism and for efficient cytosolic pH homeostasis, and long-term, V-ATPases are important for stable localization of Pma1p at the plasma membrane.
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Affiliation(s)
- Gloria A Martínez-Muñoz
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
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137
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Morille M, Passirani C, Vonarbourg A, Clavreul A, Benoit JP. Progress in developing cationic vectors for non-viral systemic gene therapy against cancer. Biomaterials 2008; 29:3477-96. [PMID: 18499247 DOI: 10.1016/j.biomaterials.2008.04.036] [Citation(s) in RCA: 568] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Accepted: 04/23/2008] [Indexed: 02/06/2023]
Abstract
Initially, gene therapy was viewed as an approach for treating hereditary diseases, but its potential role in the treatment of acquired diseases such as cancer is now widely recognized. The understanding of the molecular mechanisms involved in cancer and the development of nucleic acid delivery systems are two concepts that have led to this development. Systemic gene delivery systems are needed for therapeutic application to cells inaccessible by percutaneous injection and for multi-located tumor sites, i.e. metastases. Non-viral vectors based on the use of cationic lipids or polymers appear to have promising potential, given the problems of safety encountered with viral vectors. Using these non-viral vectors, the current challenge is to obtain a similarly effective transfection to viral ones. Based on the advantages and disadvantages of existing vectors and on the hurdles encountered with these carriers, the aim of this review is to describe the "perfect vector" for systemic gene therapy against cancer.
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Affiliation(s)
- Marie Morille
- Inserm U646, Ingénierie de la Vectorisation Particulaire, Université d'Angers, 10, rue André Boquel, 49100 Angers, France
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138
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Lehane AM, Hayward R, Saliba KJ, Kirk K. A verapamil-sensitive chloroquine-associated H+ leak from the digestive vacuole in chloroquine-resistant malaria parasites. J Cell Sci 2008; 121:1624-32. [PMID: 18445688 DOI: 10.1242/jcs.016758] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chloroquine resistance in the malaria parasite Plasmodium falciparum has made malaria increasingly difficult to control. Chloroquine-resistant parasites accumulate less chloroquine than their chloroquine-sensitive counterparts; however, the mechanism underlying this remains unclear. The primary site of accumulation and antimalarial action of chloroquine is the internal acidic digestive vacuole of the parasite, the acidity of which is maintained by inwardly-directed H+ pumps, working against the (outward) leak of H+. In this study we have investigated the leak of H+ from the digestive vacuole of the parasite by monitoring the alkalinisation of the vacuole following inhibition of the H+-pumping V-type ATPase by concanamycin A. The rates of alkalinisation observed in three chloroquine-resistant strains were two- to fourfold higher than those measured in three chloroquine-sensitive strains. On addition of chloroquine there was a dramatic increase in the rate of alkalinisation in the chloroquine-resistant strains, whereas chloroquine caused the rate of alkalinisation to decrease in the chloroquine-sensitive strains. The chloroquine-associated increase in the rate of alkalinisation seen in chloroquine-resistant parasites was inhibited by the chloroquine-resistance reversal agent verapamil. The data are consistent with the hypothesis that in chloroquine-resistant parasites chloroquine effluxes from the digestive vacuole, in association with H+, via a verapamil-sensitive pathway.
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Affiliation(s)
- Adele M Lehane
- School of Biochemistry and Molecular Biology, The Australian National University, Canberra ACT 0200, Australia
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139
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Jerome WG, Cox BE, Griffin EE, Ullery JC. Lysosomal cholesterol accumulation inhibits subsequent hydrolysis of lipoprotein cholesteryl ester. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2008; 14:138-49. [PMID: 18312718 PMCID: PMC2837357 DOI: 10.1017/s1431927608080069] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Accepted: 08/07/2007] [Indexed: 05/20/2023]
Abstract
Human macrophages incubated for prolonged periods with mildly oxidized LDL (oxLDL) or cholesteryl ester-rich lipid dispersions (DISP) accumulate free and esterified cholesterol within large, swollen lysosomes similar to those in foam cells of atherosclerosis. The cholesteryl ester (CE) accumulation is, in part, the result of inhibition of lysosomal hydrolysis due to increased lysosomal pH mediated by excessive lysosomal free cholesterol (FC). To determine if the inhibition of hydrolysis was long lived and further define the extent of the lysosomal defect, we incubated THP-1 macrophages with oxLDL or DISP to produce lysosome sterol engorgement and then chased with acetylated LDL (acLDL). Unlike oxLDL or DISP, CE from acLDL normally is hydrolyzed rapidly. Three days of incubation with oxLDL or DISP produced an excess of CE in lipid-engorged lysosomes, indicative of inhibition. After prolonged oxLDL or DISP pretreatment, subsequent hydrolysis of acLDL CE was inhibited. Coincident with the inhibition, the lipid-engorged lysosomes failed to maintain an acidic pH during both the initial pretreatment and subsequent acLDL incubation. This indicates that the alterations in lysosomes were general, long lived, and affected subsequent lipoprotein metabolism. This same phenomenon, occurring within atherosclerotic foam cells, could significantly affect lesion progression.
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Affiliation(s)
- W Gray Jerome
- Department of Pathology, Vanderbilt University School of Medicine, South Nashville, TN 37232-2561, USA.
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140
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Clustering of endocytic organelles in parental and drug-resistant myeloid leukaemia cell lines lacking centrosomally organised microtubule arrays. Int J Biochem Cell Biol 2008; 40:2240-52. [PMID: 18439867 DOI: 10.1016/j.biocel.2008.03.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 02/28/2008] [Accepted: 03/01/2008] [Indexed: 11/23/2022]
Abstract
Spatial organisation and trafficking of endocytic organelles in mammalian cells is tightly regulated and dependent on cytoskeletal networks. The dynamics of endocytic pathways is modified in a number of diseases, including cancer, and notably in multidrug resistant (MDR) cells that are refractory to the effects of several anti-cancer agents. These cells often upregulate expression of drug-efflux pumps but this may be synergistic with alternative resistance mechanisms including increased acidification of endocytic organelles that enhances vesicular sequestration of weak-base anti-cancer drugs such as daunorubicin away from their nuclear target. Here, we characterised the distribution of sequestered daunorubicin in commonly used leukaemia cell lines, HL-60, K562, KG1a and the multidrug resistant HL-60/ADR line, and related this to the spatial distribution of their endocytic organelles and microtubule networks. HL-60 and KG1a cells contained microtubule arrays emanating from organising centres, and their endocytic organelles and daunorubicin labelled vesicles were scattered throughout the cytoplasm. HL-60/ADR and K562 cells showed extensive clustering of early and recycling endosomes, late endosomes, lysosomes and daunorubicin to a juxtanuclear region but these cells lacked microtubule arrays. Microtubular organisation within these clustered regions was however, required for spatial tethering of endocytic organelles and the Golgi, as treatment with nocodazole and paclitaxel had major effects on their distribution. HL-60 and HL-60/ADR cells had similar lysosomal pH of <5.0 and overall these findings suggests a general relationship between the absence of microtubule arrays and the propensity of leukaemia cell lines to cluster endocytic organelles and daunorubicin into the juxtanuclear region.
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141
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The role of calcium and other ions in sorting and delivery in the late endocytic pathway. Biochem Soc Trans 2008; 35:1088-91. [PMID: 17956286 DOI: 10.1042/bst0351088] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The passage of endocytosed receptor-bound ligands and membrane proteins through the endocytic pathway of mammalian cells to lysosomes occurs via early and late endosomes. The latter contain many luminal vesicles and are often referred to as MVBs (multivesicular bodies). The overall morphology of endosomal compartments is, in major part, a consequence of the many fusion events occurring in the endocytic pathway. Kissing events and direct fusion between late endosomes and lysosomes provide a means of delivery to lysosomes. The luminal ionic composition of organelles in the endocytic pathway is of considerable importance both in the trafficking of endocytosed ligands and in the membrane fusion events. In particular, H(+) ions play a role in sorting processes and providing an appropriate environment for the action of lysosomal acid hydrolases. Na(+)/H(+) exchangers in the endosomal membrane have been implicated in the formation of MVBs and sorting into luminal vesicles. Ca(2+) ions are required for fusion events and luminal content condensation in the lysosome. Consistent with an important role for luminal Ca(2+) in traffic through the late endocytic pathway, mutations in the gene encoding mucolipin-1, a lysosomal non-specific cation channel, result in abnormalities in lipid traffic and are associated with the autosomal recessive lysosomal storage disease MLIV (mucolipidosis type IV).
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142
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Leuber M, Kronhardt A, Tonello F, Dal Molin F, Benz R. Binding of N-terminal fragments of anthrax edema factor (EF(N)) and lethal factor (LF(N)) to the protective antigen pore. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1436-43. [PMID: 18243126 DOI: 10.1016/j.bbamem.2008.01.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 01/07/2008] [Accepted: 01/08/2008] [Indexed: 12/23/2022]
Abstract
Anthrax toxin consists of three different molecules: the binding component protective antigen (PA, 83 kDa), and the enzymatic components lethal factor (LF, 90 kDa) and edema factor (EF, 89 kDa). The 63 kDa C-terminal part of PA, PA(63), forms heptameric channels that insert in endosomal membranes at low pH, necessary to translocate EF and LF into the cytosol of target cells. In many studies, about 30 kDa N-terminal fragments of the enzymatic components EF (254 amino acids) and LF (268 amino acids) were used to study their interaction with PA(63)-channels. Here, in experiments with artificial lipid bilayer membranes, EF(N) and LF(N) show block of PA(63)-channels in a dose, voltage and ionic strength dependent way with high affinity. However, when compared to their full-length counterparts EF and LF, they exhibit considerably lower binding affinity. Decreasing ionic strength and, in the case of EF(N), increasing transmembrane voltage at the cis side of the membranes, resulted in a strong decrease of half saturation constants. Our results demonstrate similarities but also remarkable differences between the binding kinetics of both truncated and full-length effectors to the PA(63)-channel.
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Affiliation(s)
- Michael Leuber
- Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Am Hubland, Würzburg, Germany
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143
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Markov D, Mosharov EV, Setlik W, Gershon MD, Sulzer D. Secretory vesicle rebound hyperacidification and increased quantal size resulting from prolonged methamphetamine exposure. J Neurochem 2008; 107:1709-21. [PMID: 19014382 DOI: 10.1111/j.1471-4159.2008.05737.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Acute exposure to amphetamines (AMPHs) collapses secretory vesicle pH gradients, which increases cytosolic catecholamine levels while decreasing the quantal size of catecholamine release during fusion events. AMPH and methamphetamine (METH), however, are retained in tissues over long durations. We used optical and electron microscopic probes to measure the effects of long-term METH exposure on secretory vesicle pH, and amperometry and intracellular patch electrochemistry to observe the effects on neurosecretion and cytosolic catecholamines in cultured rat chromaffin cells. In contrast to acute METH effects, exposure to the drug for 6-48 h at 10 microM and higher concentrations produced a concentration-dependent rebound hyperacidification of secretory vesicles. At 5-10 microM levels, prolonged METH increased the quantal size and reinstated exocytotic catecholamine release, although very high (> 100 microM) levels of the drug, while continuing to produce rebound hyperacidification, did not increase quantal size. Secretory vesicle rebound hyperacidification was temperature dependent with optimal response at approximately 37 degrees C, was not blocked by the transcription inhibitor, puromycin, and appears to be a general compensatory response to prolonged exposure with membranophilic weak bases, including AMPHs, methylphenidate, cocaine, and ammonia. Thus, under some conditions of prolonged exposure, AMPHs and other weak bases can enhance, rather than deplete, the vesicular release of catecholamines via a compensatory response resulting in vesicle acidification.
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Affiliation(s)
- Dmitriy Markov
- Department of Neurology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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144
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Huynh KK, Grinstein S. Regulation of vacuolar pH and its modulation by some microbial species. Microbiol Mol Biol Rev 2007; 71:452-62. [PMID: 17804666 PMCID: PMC2168644 DOI: 10.1128/mmbr.00003-07] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
To survive within the host, pathogens such as Mycobacterium tuberculosis and Helicobacter pylori need to evade the immune response and find a protected niche where they are not exposed to microbicidal effectors. The pH of the microenvironment surrounding the pathogen plays a critical role in dictating the organism's fate. Specifically, the acidic pH of the endocytic organelles and phagosomes not only can affect bacterial growth directly but also promotes a variety of host microbicidal responses. The development of mechanisms to avoid or resist the acidic environment generated by host cells is therefore crucial to the survival of many pathogens. Here we review the processes that underlie the generation of organellar acidification and discuss strategies employed by pathogens to circumvent it, using M. tuberculosis and H. pylori as examples.
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Affiliation(s)
- Kassidy K Huynh
- Cell Biology Program, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8
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145
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Gamazo C, Prior S, Concepción Lecároz M, Vitas AI, Campanero MA, Pérez G, Gonzalez D, Blanco-Prieto MJ. Biodegradable gentamicin delivery systems for parenteral use for the treatment of intracellular bacterial infections. Expert Opin Drug Deliv 2007; 4:677-88. [DOI: 10.1517/17425247.4.6.677] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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146
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Obara M, Szeliga M, Albrecht J. Regulation of pH in the mammalian central nervous system under normal and pathological conditions: facts and hypotheses. Neurochem Int 2007; 52:905-19. [PMID: 18061308 DOI: 10.1016/j.neuint.2007.10.015] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 10/17/2007] [Accepted: 10/22/2007] [Indexed: 11/27/2022]
Abstract
The maintenance of pH homeostasis in the CNS is of key importance for proper execution and regulation of neurotransmission, and deviations from this homeostasis are a crucial factor in the mechanism underlying a spectrum of pathological conditions. The first few sections of the review are devoted to the brain operating under normal conditions. The article commences with an overview of how extrinsic factors modelling the brain at work: neurotransmitters, depolarising stimuli (potassium and voltage changes) and cyclic nucleotides as major signal transducing vehicles affect pH in the CNS. Further, consequences of pH alterations on the major aspects of CNS function and metabolism are outlined. Next, the major cellular events involved in the transport, sequestration, metabolic production and buffering of protons that are common to all the mammalian cells, including the CNS cells. Since CNS function reflects tight interaction between astrocytes and neurons, the pH regulatory events pertinent to either cell type are discussed: overwhelming evidence implicates astrocytes as a key player in pH homeostasis in the brain. The different classes of membrane proteins involved in proton shuttling are listed and their mechanisms of action are given. These include: the Na+/H+ exchanger, different classes of bicarbonate transporters acting in a sodium-dependent- or -independent mode, monocarboxylic acid transporters and the vacuolar-type proton ATPase. A separate section is devoted to carbonic anhydrase, which is represented by multiple isoenzymes capable of pH buffering both in the cell interior and in the extracellular space. Next, impairment of pH regulation and compensatory responses occurring in brain affected by different pathologies: hypoxia/ischemia, epilepsy, hyperammonemic encephalopathies, cerebral tumours and HIV will be described. The review is limited to facts and plausible hypotheses pertaining to phenomena directly involved in pH regulation: changes in pH that accompany metabolic stress but have no distinct implications for the pH regulatory mechanisms are not dealt with. In most cases, the vast body of knowledge derived from in vitro studies remains to be verified in in vivo settings.
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Affiliation(s)
- Marta Obara
- Department of Neurotoxicology, Medical Research Centre, Polish Academy of Sciences, 5 Pawińskiego Street, 02-106 Warsaw, Poland
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147
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148
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Saito M, Hanson PI, Schlesinger P. Luminal chloride-dependent activation of endosome calcium channels: patch clamp study of enlarged endosomes. J Biol Chem 2007; 282:27327-27333. [PMID: 17609211 DOI: 10.1074/jbc.m702557200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Although Ca(2+) release from early endosomes (EE) is important for the fusion of primary endosomes, the presence of an ion channel responsible for releasing calcium from the EE has not been shown. A recent proteomics study has identified the TRPV2 channel protein in EE, suggesting that transient receptor potential-like Ca(2+) channels may be in endosomes. The submicron size of endosomes has made it difficult to study their ion channels in the past. We have overcome this problem by generating enlarged EE with the help of a hydrolysis-deficient SKD1/VPS4B mutant in HEK293 cells. Here we report the first patch clamp recording of a novel endosome calcium channel (ECC) in these enlarged EE. The ECC shows a similar pharmacology to that of the TRPV2 channel. In addition, the ECC has a unique chloride-dependent regulation; it is inhibited by the endosome luminal chloride with a K(50) of 82 mm.
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Affiliation(s)
- Mitsuyoshi Saito
- Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri 63110.
| | - Phyllis I Hanson
- Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri 63110
| | - Paul Schlesinger
- Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri 63110
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149
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Erent M, Meli A, Moisoi N, Babich V, Hannah MJ, Skehel P, Knipe L, Zupancic G, Ogden D, Carter T. Rate, extent and concentration dependence of histamine-evoked Weibel-Palade body exocytosis determined from individual fusion events in human endothelial cells. J Physiol 2007; 583:195-212. [PMID: 17540703 PMCID: PMC2277235 DOI: 10.1113/jphysiol.2007.132993] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The rate, concentration dependence and extent of histamine-evoked Weibel-Palade body (WPB) exocytosis were investigated with time-resolved fluorescence microscopy in cultured human umbilical vein endothelial cells expressing WPB-targeted chimeras of enhanced green fluorescent protein (EGFP). Exocytosis of single WPBs was characterized by an increase in EGFP fluorescence, morphological changes and release of WPB contents. The fluorescence increase was due to a rise of intra-WPB pH from resting levels, estimated as pH 5.45+/-0.26 (s.d., n=144), to pH 7.40. It coincided with uptake of extracellular Alexa-647, indicating the formation of a fusion pore, prior to loss of fluorescent contents. Delays between the increase in intracellular free calcium ion concentration evoked by histamine and the first fusion event were 10.0+/-4.42 s (n=9 cells) at 0.3 microM histamine and 1.57+/-0.21 s (n=15 cells) at 100 microM histamine, indicating the existence of a slow process or processes in histamine-evoked WPB exocytosis. The maximum rates of exocytosis were 1.20+/-0.16 WPB s(-1) (n=9) at 0.3 microM and 3.66+/-0.45 WPB s(-1) at 100 microM histamine (n=15). These occurred 2-5 s after histamine addition and declined to lower rates with continued stimulation. The initial delays and maximal rate of exocytosis were unaffected by removal of external Ca2+ indicating that the initial burst of secretion is driven by Ca2+ release from internal stores, but sustained exocytosis required external Ca2+. Data were compared to exocytosis evoked by a maximal concentration of the strong secretagogue ionomycin (1 microM), for which there was a delay between calcium elevation and secretion of 1.67+/-0.24 s (n=6), and a peak fusion rate of approximately 10 WPB s(-1).
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Affiliation(s)
- M Erent
- Medical Research Councils National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
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150
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Wolf M, Bauder-Wüst U, Eskerski H, Bauer C, Eisenhut M. Role of acidic cell organelles in the higher nonmelanoma retention of melanoma markers based on N-(2-dialkylaminoethyl)benzamides and the cytotoxicity of alkylating benzamides. Melanoma Res 2007; 17:61-73. [PMID: 17496781 DOI: 10.1097/cmr.0b013e328042bb1d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Melanoma markers based on both N-(2-dialkylaminoethyl)benzamides and lysosomotropic agents comprise a N-(2-dialkylaminoethyl)aminocarbamoyl pharmacophore, suggesting that benzamides and lysosomotropic probes should show affinity to melanoma and acidic cell organelles. We prepared novel fluorescent N-(2-dialkylaminoethyl)benzamides to prove this presumption. Lysosomotropic probes showed a melanin affinity comparable to benzamides. Lysosomal markers and benzamides colocalized in acidic organelles. Various nonmelanoma cell lines showed equal benzamide uptake and retention compared with melanoma cells. In nonmelanoma cells the amount of retained benzamides correlates with the number of acidic cell organelles. Benzamides almost completely failed to accumulate in melanoma cells with neutralized acidic organelles but normal melanin content. In melanoma retention of benzamides, acidic cell organelles are the main determinant. N-(2-dialkylaminoethyl)benzamides are lysosomotropic probes with high accumulation in nonmelanoma tumors with many acidic cell organelles. Alkylating benzamides were reported previously to show a melanoma unselective, in general enhanced cytotoxicity. Alkylating benzamides can act as lysosomotropic detergents or as DNA alkylators. The ability of alkylating benzamides to disrupt the membrane of lysosomes and cause liberation of lysosomal-trapped fluorescent dyes was demonstrated by fluorescence microscopy. Whether they act as an alkylating agent or a lysosomotropic detergent in a specific cell line is dependent on the amount of acidic cell organelles. In cell lines with small amounts of acidic cell organelles alkylating benzamides act as alkylating agents, whereas in cell lines with many acidic cell organelles they act as lysosomotropic detergents. In cell lines with high amounts of acidic cell organelles they do not reach the nucleus.
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Affiliation(s)
- Markus Wolf
- Department of Radiopharmaceutical Chemistry, German Cancer Research Center (DKFZ), Heidelberg, Germany.
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