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Cibelli A, Mola MG, Saracino E, Barile B, Abbrescia P, Mogni G, Spray DC, Scemes E, Rossi A, Spennato D, Svelto M, Frigeri A, Benfenati V, Nicchia GP. Aquaporin-4 and transient receptor potential vanilloid 4 balance in early postnatal neurodevelopment. Glia 2024; 72:938-959. [PMID: 38362923 DOI: 10.1002/glia.24512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 01/15/2024] [Accepted: 01/19/2024] [Indexed: 02/17/2024]
Abstract
In the adult brain, the water channel aquaporin-4 (AQP4) is expressed in astrocyte endfoot, in supramolecular assemblies, called "Orthogonal Arrays of Particles" (OAPs) together with the transient receptor potential vanilloid 4 (TRPV4), finely regulating the cell volume. The present study aimed at investigating the contribution of AQP4 and TRPV4 to CNS early postnatal development using WT and AQP4 KO brain and retina and neuronal stem cells (NSCs), as an in vitro model of astrocyte differentiation. Western blot analysis showed that, differently from AQP4 and the glial cell markers, TRPV4 was downregulated during CNS development and NSC differentiation. Blue native/SDS-PAGE revealed that AQP4 progressively organized into OAPs throughout the entire differentiation process. Fluorescence quenching assay indicated that the speed of cell volume changes was time-related to NSC differentiation and functional to their migratory ability. Calcium imaging showed that the amplitude of TRPV4 Ca2+ transient is lower, and the dynamics are changed during differentiation and suppressed in AQP4 KO NSCs. Overall, these findings suggest that early postnatal neurodevelopment is subjected to temporally modulated water and Ca2+ dynamics likely to be those sustaining the biochemical and physiological mechanisms responsible for astrocyte differentiation during brain and retinal development.
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Affiliation(s)
- Antonio Cibelli
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Emanuela Saracino
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Barbara Barile
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Pasqua Abbrescia
- Department of Translational Biomedicine and Neuroscience, University of Bari Aldo Moro-Medical School, Bari, Italy
| | - Guido Mogni
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Eliana Scemes
- Department of Cell Biology and Anatomy, NY Medical College, Valhalla, New York, USA
| | - Andrea Rossi
- Genome Engineering and Model Development Lab (GEMD), IUF-Leibniz Research Institute for Environmental Medicine, Düsseldorf, Germany
| | - Diletta Spennato
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Frigeri
- Department of Translational Biomedicine and Neuroscience, University of Bari Aldo Moro-Medical School, Bari, Italy
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Valentina Benfenati
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Grazia Paola Nicchia
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
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Barile B, Mola MG, Formaggio F, Saracino E, Cibelli A, Gargano CD, Mogni G, Frigeri A, Caprini M, Benfenati V, Nicchia GP. AQP4-independent TRPV4 modulation of plasma membrane water permeability. Front Cell Neurosci 2023; 17:1247761. [PMID: 37720545 PMCID: PMC10500071 DOI: 10.3389/fncel.2023.1247761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 08/14/2023] [Indexed: 09/19/2023] Open
Abstract
Despite of the major role of aquaporin (AQP) water channels in controlling transmembrane water fluxes, alternative ways for modulating water permeation have been proposed. In the Central Nervous System (CNS), Aquaporin-4 (AQP4) is reported to be functionally coupled with the calcium-channel Transient-Receptor Potential Vanilloid member-4 (TRPV4), which is controversially involved in cell volume regulation mechanisms and water transport dynamics. The present work aims to investigate the selective role of TRPV4 in regulating plasma membrane water permeability in an AQP4-independent way. Fluorescence-quenching water transport experiments in Aqp4-/- astrocytes revealed that cell swelling rate is significantly increased upon TRPV4 activation and in the absence of AQP4. The biophysical properties of TRPV4-dependent water transport were therefore assessed using the HEK-293 cell model. Calcein quenching experiments showed that chemical and thermal activation of TRPV4 overexpressed in HEK-293 cells leads to faster swelling kinetics. Stopped-flow light scattering water transport assay was used to measure the osmotic permeability coefficient (Pf, cm/s) and activation energy (Ea, kcal/mol) conferred by TRPV4. Results provided evidence that although the Pf measured upon TRPV4 activation is lower than the one obtained in AQP4-overexpressing cells (Pf of AQP4 = 0.01667 ± 0.0007; Pf of TRPV4 = 0.002261 ± 0.0004; Pf of TRPV4 + 4αPDD = 0.007985 ± 0.0006; Pf of WT = 0.002249 ± 0.0002), along with activation energy values (Ea of AQP4 = 0.86 ± 0.0006; Ea of TRPV4 + 4αPDD = 2.73 ± 1.9; Ea of WT = 8.532 ± 0.4), these parameters were compatible with a facilitated pathway for water movement rather than simple diffusion. The possibility to tune plasma membrane water permeability more finely through TRPV4 might represent a protective mechanism in cells constantly facing severe osmotic challenges to avoid the potential deleterious effects of the rapid cell swelling occurring via AQP channels.
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Affiliation(s)
- Barbara Barile
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Francesco Formaggio
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Emanuela Saracino
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Antonio Cibelli
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Domenica Gargano
- Department of Translational Biomedicine and Neuroscience (DiBraiN), School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Guido Mogni
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Frigeri
- Department of Translational Biomedicine and Neuroscience (DiBraiN), School of Medicine, University of Bari Aldo Moro, Bari, Italy
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 840 Kennedy Center, Bronx, NY, United States
| | - Marco Caprini
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Valentina Benfenati
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 840 Kennedy Center, Bronx, NY, United States
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O'Neill KM, Saracino E, Barile B, Mennona NJ, Mola MG, Pathak S, Posati T, Zamboni R, Nicchia GP, Benfenati V, Losert W. Decoding Natural Astrocyte Rhythms: Dynamic Actin Waves Result from Environmental Sensing by Primary Rodent Astrocytes. Adv Biol (Weinh) 2023; 7:e2200269. [PMID: 36709481 DOI: 10.1002/adbi.202200269] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 12/07/2022] [Indexed: 01/30/2023]
Abstract
Astrocytes are key regulators of brain homeostasis, equilibrating ion, water, and neurotransmitter concentrations and maintaining essential conditions for proper cognitive function. Recently, it has been shown that the excitability of the actin cytoskeleton manifests in second-scale dynamic fluctuations and acts as a sensor of chemophysical environmental cues. However, it is not known whether the cytoskeleton is excitable in astrocytes and how the homeostatic function of astrocytes is linked to the dynamics of the cytoskeleton. Here it is shown that homeostatic regulation involves the excitable dynamics of actin in certain subcellular regions of astrocytes, especially near the cell boundary. The results further indicate that actin dynamics concentrate into "hotspot" regions that selectively respond to certain chemophysical stimuli, specifically the homeostatic challenges of ion or water concentration increases. Substrate topography makes the actin dynamics of astrocytes weaker. Super-resolution images demonstrate that surface topography is also associated with the predominant perpendicular alignment of actin filaments near the cell boundary, whereas flat substrates result in an actin cortex mainly parallel to the cell boundary. Additionally, coculture with neurons increases both the probability of actin dynamics and the strength of hotspots. The excitable systems character of actin thus makes astrocytes direct participants in neural cell network dynamics.
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Affiliation(s)
- Kate M O'Neill
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
| | - Emanuela Saracino
- Institute of Organic Synthesis and Photoreactivity, National Research Council of Italy, 40129, Bologna, Italy
| | - Barbara Barile
- Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, 70125, Bari, Italy
| | - Nicholas J Mennona
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
- Physics Department, University of Maryland, College Park, MD, 20742, USA
| | - Maria Grazia Mola
- Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, 70125, Bari, Italy
| | - Spandan Pathak
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
| | - Tamara Posati
- Institute of Organic Synthesis and Photoreactivity, National Research Council of Italy, 40129, Bologna, Italy
| | - Roberto Zamboni
- Institute of Organic Synthesis and Photoreactivity, National Research Council of Italy, 40129, Bologna, Italy
| | - Grazia P Nicchia
- Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, 70125, Bari, Italy
| | - Valentina Benfenati
- Institute of Organic Synthesis and Photoreactivity, National Research Council of Italy, 40129, Bologna, Italy
| | - Wolfgang Losert
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742, USA
- Physics Department, University of Maryland, College Park, MD, 20742, USA
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Scorza SI, Milano S, Saponara I, Certini M, De Zio R, Mola MG, Procino G, Carmosino M, Moccia F, Svelto M, Gerbino A. TRPML1-Induced Lysosomal Ca 2+ Signals Activate AQP2 Translocation and Water Flux in Renal Collecting Duct Cells. Int J Mol Sci 2023; 24:ijms24021647. [PMID: 36675161 PMCID: PMC9861594 DOI: 10.3390/ijms24021647] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/04/2023] [Accepted: 01/11/2023] [Indexed: 01/19/2023] Open
Abstract
Lysosomes are acidic Ca2+ storage organelles that actively generate local Ca2+ signaling events to regulate a plethora of cell functions. Here, we characterized lysosomal Ca2+ signals in mouse renal collecting duct (CD) cells and we assessed their putative role in aquaporin 2 (AQP2)-dependent water reabsorption. Bafilomycin A1 and ML-SA1 triggered similar Ca2+ oscillations, in the absence of extracellular Ca2+, by alkalizing the acidic lysosomal pH or activating the lysosomal cation channel mucolipin 1 (TRPML1), respectively. TRPML1-dependent Ca2+ signals were blocked either pharmacologically or by lysosomes' osmotic permeabilization, thus indicating these organelles as primary sources of Ca2+ release. Lysosome-induced Ca2+ oscillations were sustained by endoplasmic reticulum (ER) Ca2+ content, while bafilomycin A1 and ML-SA1 did not directly interfere with ER Ca2+ homeostasis per se. TRPML1 activation strongly increased AQP2 apical expression and depolymerized the actin cytoskeleton, thereby boosting water flux in response to an hypoosmotic stimulus. These effects were strictly dependent on the activation of the Ca2+/calcineurin pathway. Conversely, bafilomycin A1 led to perinuclear accumulation of AQP2 vesicles without affecting water permeability. Overall, lysosomal Ca2+ signaling events can be differently decoded to modulate Ca2+-dependent cellular functions related to the dock/fusion of AQP2-transporting vesicles in principal cells of the CD.
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Affiliation(s)
- Simona Ida Scorza
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Serena Milano
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Ilenia Saponara
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Maira Certini
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Roberta De Zio
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Giuseppe Procino
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Monica Carmosino
- Department of Sciences, University of Basilicata, 85100 Potenza, Italy
| | - Francesco Moccia
- Department of Biology and Biotechnology Lazzaro Spallanzani, University of Pavia, 27100 Pavia, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Andrea Gerbino
- Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70125 Bari, Italy
- Correspondence: ; Tel.: +39-0805443334
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Centrone M, D’Agostino M, Ranieri M, Mola MG, Faviana P, Lippolis PV, Silvestris DA, Venneri M, Di Mise A, Valenti G, Tamma G. dDAVP Downregulates the AQP3-Mediated Glycerol Transport via V1aR in Human Colon HCT8 Cells. Front Cell Dev Biol 2022; 10:919438. [PMID: 35874817 PMCID: PMC9304624 DOI: 10.3389/fcell.2022.919438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 06/15/2022] [Indexed: 11/28/2022] Open
Abstract
Vasopressin (AVP) plays a key function in controlling body water and salt balance through the activation of the vasopressin receptors V1aR and V2R. Abnormal secretion of AVP can cause the syndrome of inappropriate antidiuresis that leads to hyponatremia, which is an electrolyte disorder often observed in the elderly hospitalized and oncologic patients. Beyond kidneys, the colonic epithelium modulates water and salt homeostasis. The water channel AQP3, expressed in villus epithelial cells is implicated in water absorption across human colonic surface cells. Here, the action of dDAVP, a stable vasopressin analog, was evaluated on the AQP3 expression and function using human colon HCT8 cells as an experimental model. Confocal and Western Blotting analysis revealed that HCT8 cells express both V1aR and V2R. Long-term (72 h) treatment with dDAVP reduced glycerol uptake and cell viability. These effects were prevented by SR49059, a synthetic antagonist of V1aR, but not by tolvaptan, a specific V2R antagonist. Of note, the SR49059 action was impaired by DFP00173, a selective inhibitor of AQP3. Interestingly, compared to the normal colonic mucosa, in the colon of patients with adenocarcinoma, the expression of V1aR was significantly decreased. These findings were confirmed by gene expression analysis with RNA-Seq data. Overall, data suggest that dDAVP, through the V1aR dependent pathway, reduces AQP3 mediated glycerol uptake, a process that is reversed in adenocarcinoma, suggesting that the AVP-dependent AQP3 pathway may represent a novel target in colon diseases associated with abnormal cell growth.
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Affiliation(s)
- Mariangela Centrone
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Mariagrazia D’Agostino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Marianna Ranieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Pinuccia Faviana
- Department of Surgical, Medical, Molecular Pathology, and Critical Area, University of Pisa, Pisa, Italy
| | | | | | - Maria Venneri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Annarita Di Mise
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Giovanna Valenti
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Grazia Tamma
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
- *Correspondence: Grazia Tamma,
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Mola MG, Saracino E, Formaggio F, Amerotti AG, Barile B, Posati T, Cibelli A, Frigeri A, Palazzo C, Zamboni R, Caprini M, Nicchia GP, Benfenati V. Cell Volume Regulation Mechanisms in Differentiated Astrocytes. Cell Physiol Biochem 2021; 55:196-212. [PMID: 34740285 DOI: 10.33594/000000469] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/08/2021] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND/AIMS The ability of astrocytes to control extracellular volume homeostasis is critical for brain function and pathology. Uncovering the mechanisms of cell volume regulation by astrocytes will be important for identifying novel therapeutic targets for neurological conditions, such as those characterized by imbalances to hydro saline challenges (as in edema) or by altered cell volume regulation (as in glioma). One major challenge in studying the astroglial membrane channels involved in volume homeostasis in cell culture model systems is that the expression patterns of these membrane channels do not resemble those observed in vivo. In our previous study, we demonstrated that rat primary astrocytes grown on nanostructured interfaces based on hydrotalcite-like compounds (HTlc) in vitro are differentiated and display molecular and functional properties of in vivo astrocytes, such as the functional expression of inwardly rectifying K+ channel (Kir 4.1) and Aquaporin-4 (AQP4) at the astrocytic microdomain. Here, we take advantage of the properties of differentiated primary astrocytes in vitro to provide an insight into the mechanism underpinning astrocytic cell volume regulation and its correlation with the expression and function of AQP4, Transient Receptor Potential Vanilloid 4
(TRPV4), and Volume Regulated Anion Channel (VRAC). METHODS The calcein quenching method was used to study water transport and cell volume regulation. Calcium imaging and electrophysiology (patch-clamp) were used for functional analyses of calcium dynamics and chloride currents. Western blot and immunofluorescence were used to analyse the expression and localization of the channel proteins of interest. RESULTS We found that the increase in water permeability, previously observed in differentiated astrocytes, occurs simultaneously with more efficient regulatory volume increase and regulatory volume decrease. Accordingly, the magnitude of the hypotonic induced intracellular calcium response, typically mediated by TRPV4, as well as the hypotonic induced VRAC current, was almost twice as high in differentiated astrocytes. Interestingly, while we confirmed increased AQP4 expression in the membrane of differentiated astrocytes, the expression of the channels TRPV4 and Leucine-Rich Repeats-Containing 8-A (LRRC8-A) were comparable between differentiated and non-differentiated astrocytes. CONCLUSION The reported results indicate that AQP4 up-regulation observed in differentiated astrocytes might promote higher sensitivity of the cell to osmotic changes, resulting in increased magnitude of calcium signaling and faster kinetics of the RVD and RVI processes. The implications for cell physiology and the mechanisms underlying astrocytic interaction with nanostructured interfaces are discussed.
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Affiliation(s)
- Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Emanuela Saracino
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), Bologna, Italy
| | - Francesco Formaggio
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Arcangela Gabriella Amerotti
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), Bologna, Italy
| | - Barbara Barile
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Tamara Posati
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), Bologna, Italy
| | - Antonio Cibelli
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Frigeri
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Claudia Palazzo
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Roberto Zamboni
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), Bologna, Italy
| | - Marco Caprini
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Grazia Paola Nicchia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy,
| | - Valentina Benfenati
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), Bologna, Italy,
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Pisani F, Simone L, Mola MG, De Bellis M, Frigeri A, Nicchia GP, Svelto M. Regulation of aquaporin-4 expression in the central nervous system investigated using M23-AQP4 null mouse. Glia 2021; 69:2235-2251. [PMID: 34038017 PMCID: PMC8361696 DOI: 10.1002/glia.24032] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 04/15/2021] [Accepted: 05/17/2021] [Indexed: 12/22/2022]
Abstract
In astrocytes, unknown mechanisms regulate the expression of M1 and M23 isoforms of water channel aquaporin-4 (M1-AQP4 and M23-AQP4). The ratio between these two isoforms controls the AQP4 assembly state in the plasma membrane known as orthogonal arrays of particles (OAPs). To give new insights into these mechanisms, here, we explore the regulation of AQP4 expression in the spinal cord of a CRISPR/Cas9 M23-null mouse model (M23-null). In the M23-null spinal cord OAP assembly, the perivascular localization of AQP4 and M1-AQP4 protein were drastically reduced. In heterozygous, M1-AQP4 was proportionally reduced with M23-AQP4, maintaining the isoform ratio unaffected. We hypothesize a role of the M23-AQP4 in the regulation of M1-AQP4 expression. M1-AQP4 transcription, splicing and M1-AQP4 protein degradation were found to be unaffected in M23-null spinal cord and in M23-null astrocyte primary culture. The translational control was investigated by mRNA-protein pull down and quantitative mass spectrometry, to isolate and quantify AQP4 mRNA binding proteins (AQP4-RBPs). Compared to WT, in M23-null spinal cord, the interaction between AQP4 mRNA and polypyrimidine tract binding protein 1, a positive regulator of AQP4 translation, was higher, while interaction with the RNA helicase DDX17 was lower. In astrocyte primary cultures, DDX17 knockdown upregulated AQP4 protein expression and increased cell swelling, leaving AQP4 mRNA levels unchanged. Here, we identify AQP4-RBPs and provide evidence that in mouse spinal cord M23-AQP4 deletion changes the interaction between AQP4 mRNA and some RBPs involved in AQP4 translation. We describe for the first time the RNA helicase DDX17 as a regulator of AQP4 expression in astrocytes.
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Affiliation(s)
- Francesco Pisani
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Laura Simone
- Fondazione IRCCS Casa Sollievo della Sofferenza, Cancer Stem Cells Unit, San Giovanni Rotondo (FG), Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Manuela De Bellis
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Frigeri
- School of Medicine, Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Grazia Paola Nicchia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy.,Institute of Biomembranes and Bioenergetics, National Research Council, Bari, Italy.,National Institute of Biostructures and Biosystems (INBB), Rome, Italy
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de Bellis M, Cibelli A, Mola MG, Pisani F, Barile B, Mastrodonato M, Banitalebi S, Amiry-Moghaddam M, Abbrescia P, Frigeri A, Svelto M, Nicchia GP. Orthogonal arrays of particle assembly are essential for normal aquaporin-4 expression level in the brain. Glia 2020; 69:473-488. [PMID: 32946135 DOI: 10.1002/glia.23909] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 08/26/2020] [Accepted: 08/28/2020] [Indexed: 11/11/2022]
Abstract
Astrocyte endfeet are endowed with aquaporin-4 (AQP4)-based assemblies called orthogonal arrays of particles (OAPs) whose function is still unclear. To investigate the function of OAPs and of AQP4 tetramers, we have generated a novel "OAP-null" mouse model selectively lacking the OAP forming M23-AQP4 isoform. We demonstrated that AQP4 transcript levels were not reduced by using qPCR. Blue native (BN)/SDS-PAGE and Western blot performed on OAP-null brain and primary astrocyte cultures showed the complete depletion of AQP4 assemblies, the selective expression of M1-AQP4-based tetramers, and a substantial reduction in AQP4 total expression level. Fluorescence quenching and super-resolution microscopy experiments showed that AQP4 tetramers were functionally expressed in astrocyte plasma membrane and their dimensions were reduced compared to wild-type assemblies. Finally, as shown by light and electron microscopy, OAP depletion resulted in a massive reduction in AQP4 expression and a loss of perivascular AQP4 staining at astrocyte endfeet, with only sparse labeling throughout the brain areas analyzed. Our study relies on the unique property of AQP4 to form OAPs, using a novel OAP-null mouse model for the first time, to show that (a) AQP4 assembly is essential for normal AQP4 expression level in the brain and (b) most of AQP4 is organized into OAPs under physiological conditions. Therefore, AQP4 tetramers cannot be used by astrocytes as an alternative to OAPs without affecting AQP4 expression levels, which is important in the physiological and pathological conditions in which OAP aggregation/disaggregation dynamics have been implicated.
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Affiliation(s)
- Manuela de Bellis
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Cibelli
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Francesco Pisani
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Barbara Barile
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | | | - Shervin Banitalebi
- Department of Molecular Medicine, Division of Anatomy, University of Oslo, Oslo, Norway
| | | | - Pasqua Abbrescia
- School of Medicine, Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Frigeri
- School of Medicine, Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Grazia Paola Nicchia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
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9
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Borrachero‐Conejo AI, Adams WR, Saracino E, Mola MG, Wang M, Posati T, Formaggio F, De Bellis M, Frigeri A, Caprini M, Hutchinson MR, Muccini M, Zamboni R, Nicchia GP, Mahadevan‐Jansen A, Benfenati V. Stimulation of water and calcium dynamics in astrocytes with pulsed infrared light. FASEB J 2020; 34:6539-6553. [DOI: 10.1096/fj.201903049r] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 02/25/2020] [Accepted: 03/06/2020] [Indexed: 01/17/2023]
Affiliation(s)
- Ana I. Borrachero‐Conejo
- Istituto per lo Studio dei Materiali Nanostrutturati Consiglio Nazionale delle Ricerche Bologna Italy
| | - Wilson R. Adams
- Department Biomedical Engineering Vanderbilt University Nashville TN USA
- Vanderbilt Biophotonics Center Vanderbilt University Nashville TN USA
| | - Emanuela Saracino
- Istituto per la Sintesi Organica e la Fotoreattività Consiglio Nazionale delle Ricerche Bologna Italy
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnology and Biopharmaceutics and Centre of Excellence in Comparative Genomics University of Bari Aldo Moro Bari Italy
| | - Manqing Wang
- Vanderbilt Biophotonics Center Vanderbilt University Nashville TN USA
- Bioengineering College Chongqing University Chongqing China
| | - Tamara Posati
- Istituto per la Sintesi Organica e la Fotoreattività Consiglio Nazionale delle Ricerche Bologna Italy
| | - Francesco Formaggio
- Dipartimento di Farmacia e Biotecnologie University of Bologna Bologna Italy
| | - Manuela De Bellis
- Department of Bioscience, Biotechnology and Biopharmaceutics and Centre of Excellence in Comparative Genomics University of Bari Aldo Moro Bari Italy
| | - Antonio Frigeri
- Department of Basic Medical Sciences, Neuroscience and Sense Organs School of Medicine University of Bari Aldo Moro Bari Italy
- Department of Neuroscience Albert Einstein College of Medicine Yeshiva University New York NY USA
| | - Marco Caprini
- Istituto per lo Studio dei Materiali Nanostrutturati Consiglio Nazionale delle Ricerche Bologna Italy
- Dipartimento di Farmacia e Biotecnologie University of Bologna Bologna Italy
| | - Mark R. Hutchinson
- Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, Adelaide Medical School University of Adelaide Adelaide SA Australia
| | - Michele Muccini
- Istituto per lo Studio dei Materiali Nanostrutturati Consiglio Nazionale delle Ricerche Bologna Italy
| | - Roberto Zamboni
- Istituto per la Sintesi Organica e la Fotoreattività Consiglio Nazionale delle Ricerche Bologna Italy
| | - Grazia Paola Nicchia
- Istituto per la Sintesi Organica e la Fotoreattività Consiglio Nazionale delle Ricerche Bologna Italy
- Department of Bioscience, Biotechnology and Biopharmaceutics and Centre of Excellence in Comparative Genomics University of Bari Aldo Moro Bari Italy
- Department of Neuroscience Albert Einstein College of Medicine Yeshiva University New York NY USA
| | - Anita Mahadevan‐Jansen
- Department Biomedical Engineering Vanderbilt University Nashville TN USA
- Vanderbilt Biophotonics Center Vanderbilt University Nashville TN USA
- Department of Neurological Surgery Vanderbilt University Medical Center Nashville TN USA
| | - Valentina Benfenati
- Istituto per la Sintesi Organica e la Fotoreattività Consiglio Nazionale delle Ricerche Bologna Italy
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10
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Palazzo C, Buccoliero C, Mola MG, Abbrescia P, Nicchia GP, Trojano M, Frigeri A. AQP4ex is crucial for the anchoring of AQP4 at the astrocyte end-feet and for neuromyelitis optica antibody binding. Acta Neuropathol Commun 2019; 7:51. [PMID: 30935410 PMCID: PMC6444679 DOI: 10.1186/s40478-019-0707-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 03/21/2019] [Indexed: 12/18/2022] Open
Abstract
Brain water homeostasis is essential for the appropriate control of neuronal activity. Furthermore, the encasement of the central nervous system (CNS) by a hard structure, greatly limits its tolerance for the volume changes occurring with acute brain edema, which quickly leads to severe damage or death. The recent discovery of the extended isoform of AQP4 (AQP4ex), generated by translational readthrough, revealed a potential new mechanism of water transport regulation and polarization at the blood-brain-barrier level. In the present study we used CRISPR/Cas9 technology to generate an AQP4ex−/− mouse model and evaluate the effect on the overall AQP4 expression, polarization, supramolecular organization in orthogonal arrays of particles (OAPs) and neuromyelitis optica (NMO-IgG) autoantibodies binding. AQP4ex removal did not cause a decrease in total AQP4 protein expression but completely suppressed the specific location of AQP4 at the astrocyte endfeet. Without AQP4ex, AQP4 was mislocalized and α-syntrophin expression, the selective partner for AQP4 localization, was partially altered. The supramolecular organization of AQP4 in OAPs was subtly altered. Indeed, the absence of AQP4ex reduced the size of AQP4-OAPs but the number of AQP4-OAP pools remained largely the same. More importantly, AQP4ex resulted critical for the binding of pathogenic human NMO-IgG autoantibodies to the brain. Indeed, the absence of AQP4ex completely abolished the binding of NMO-IgG at the perivascular astrocyte endfeet. This study provides the first direct evidence in vivo on the specific role of AQP4ex in AQP4 perivascular OAPs assembly and confinement and reveals AQP4ex as new and important player in neuromyelitis optica.
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11
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Pisani F, Simone L, Mola MG, De Bellis M, Mastrapasqua M, Ruggieri M, Trojano M, Nicchia GP, Svelto M, Frigeri A. Host-Cell Type Dependent Features of Recombinant Human Aquaporin-4 Orthogonal Arrays of Particles-New Insights for Structural and Functional Studies. Cells 2019; 8:cells8020119. [PMID: 30717425 PMCID: PMC6406603 DOI: 10.3390/cells8020119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 01/26/2019] [Accepted: 02/01/2019] [Indexed: 11/16/2022] Open
Abstract
The CNS plasma-membrane water channel aquaporin-4 (AQP4) is expressed as two major isoforms able to aggregate into supramolecular assemblies known as ‘orthogonal arrays of particles’ (OAPs). OAP subnanometric features are largely unknown mainly because a method for the expression, isolation, and crystallization of integral human OAPs has not been developed. Here, the human OAP-forming isoform M23-AQP4 was expressed in insect and mammalian cell lines and AQP4 and OAP features evaluated. Native size exclusion chromatography was employed to isolate and analyze authentically folded OAPs, and neuromyelitis optica (NMO)-specific sandwich ELISA was developed to test OAP-integrity. The results demonstrate that in insect cells most AQP4 remains intracellular and unfolded and that OAPs are largely disassembled after the detergent extraction step. In mammalian cells, AQP4 showed regular plasma membrane targeting and OAPs exhibited strong post-extraction stability. Starting from the mammalian cell expression system, we isolated authentically folded OAPs. Together these data suggest a new strategy for expressing and isolating integral recombinant human OAPs and providing new insights into the cell-type dependent OAP-assembly and post-extraction stability, potentially useful to design new approaches for structural and functional studies of OAP and for other plasma membrane proteins organized into supramolecular structures.
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Affiliation(s)
- Francesco Pisani
- Department of Bioscience, Biotechnologies and Biopharmaceutic, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
| | - Laura Simone
- Fondazione IRCCS Casa Sollievo della Sofferenza, Cancer Stem Cells Unit, 71013 San Giovanni Rotondo (FG), Italy.
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnologies and Biopharmaceutic, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
| | - Manuela De Bellis
- Department of Bioscience, Biotechnologies and Biopharmaceutic, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
| | - Maria Mastrapasqua
- School of Medicine, Basic Medical Sciences, Neuroscience and Sense Organs, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
| | - Maddalena Ruggieri
- School of Medicine, Basic Medical Sciences, Neuroscience and Sense Organs, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
| | - Maria Trojano
- School of Medicine, Basic Medical Sciences, Neuroscience and Sense Organs, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnologies and Biopharmaceutic, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
| | - Maria Svelto
- Department of Bioscience, Biotechnologies and Biopharmaceutic, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, National Research Council, 70126 Bari, Italy.
| | - Antonio Frigeri
- School of Medicine, Basic Medical Sciences, Neuroscience and Sense Organs, Univ. of Bari "Aldo Moro", 70124 Bari, Italy.
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12
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Formaggio F, Saracino E, Mola MG, Rao SB, Amiry-Moghaddam M, Muccini M, Zamboni R, Nicchia GP, Caprini M, Benfenati V. LRRC8A is essential for swelling-activated chloride current and for regulatory volume decrease in astrocytes. FASEB J 2018; 33:101-113. [PMID: 29957062 DOI: 10.1096/fj.201701397rr] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Consolidated evidence indicates that astroglial cells are critical in the homeostatic regulation of cellular volume by means of ion channels and aquaporin-4. Volume-regulated anion channel (VRAC) is the chloride channel that is activated upon cell swelling and critically contributes to cell volume regulation in astrocytes. The molecular identity of VRAC has been recently defined, revealing that it belongs to the leucine-rich repeat-containing 8 (LRRC8) protein family. However, there is a lack of evidence demonstrating that LRRC8A underpins VRAC currents in astrocyte. Nonetheless, direct evidence of the role of LRRC8A in astrocytic regulatory volume decrease remains to be proved. Here, we aim to bridge this gap in knowledge by combining RNA interference specific for LRRC8A with patch-clamp analyses and a water-permeability assay. We demonstrated that LRRC8A molecular expression is essential for swelling-activated chloride current via VRAC in primary-cultured cortical astrocytes. The knockdown of LRRC8A with a specific short interference RNA abolished the recovery of the cell volume after swelling induced by hypotonic challenge. In addition, immunoblotting, immunofluorescence, confocal imaging, and immunogold electron microscopy demonstrated that LRRC8A is expressed in the plasma membrane of primary cortical astrocytes and in situ in astrocytes at the perivascular interface with endothelial cells. Collectively, our results suggest that LRRC8A is an essential subunit of VRAC and a key factor for astroglial volume homeostasis.-Formaggio, F., Saracino, E., Mola, M. G., Rao, S. B., Amiry-Moghaddam, M., Muccini, M., Zamboni, R., Nicchia, G. P., Caprini, M., Benfenati, V. LRRC8A is essential for swelling-activated chloride current and for regulatory volume decrease in astrocytes.
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Affiliation(s)
- Francesco Formaggio
- Laboratory of Human and General Physiology, Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy.,Institute for the Study of Nanostructured Materials, National Research Council of Italy, Bologna, Italy
| | - Emanuela Saracino
- Institute for the Organic Synthesis and Photoreactivity, National Research Council of Italy, Bologna, Italy
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnologies, and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari Aldo Moro, Bari, Italy
| | - Shreyas Balachandra Rao
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Mahmood Amiry-Moghaddam
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Michele Muccini
- Institute for the Study of Nanostructured Materials, National Research Council of Italy, Bologna, Italy
| | - Roberto Zamboni
- Institute for the Organic Synthesis and Photoreactivity, National Research Council of Italy, Bologna, Italy
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnologies, and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari Aldo Moro, Bari, Italy.,Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York, USA
| | - Marco Caprini
- Laboratory of Human and General Physiology, Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy.,Institute for the Study of Nanostructured Materials, National Research Council of Italy, Bologna, Italy
| | - Valentina Benfenati
- Institute for the Study of Nanostructured Materials, National Research Council of Italy, Bologna, Italy.,Institute for the Organic Synthesis and Photoreactivity, National Research Council of Italy, Bologna, Italy
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13
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Gerbino A, Bottillo I, Milano S, Lipari M, Zio RD, Morlino S, Mola MG, Procino G, Re F, Zachara E, Grammatico P, Svelto M, Carmosino M. Functional Characterization of a Novel Truncating Mutation in Lamin A/C Gene in a Family with a Severe Cardiomyopathy with Conduction Defects. Cell Physiol Biochem 2017; 44:1559-1577. [PMID: 29197877 DOI: 10.1159/000485651] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 11/01/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Truncating LMNA gene mutations occur in many inherited cardiomyopathy cases, but the molecular mechanisms involved in the disease they cause have not yet been systematically investigated. Here, we studied a novel frameshift LMNA variant (p.D243Gfs*4) identified in three members of an Italian family co-segregating with a severe form of cardiomyopathy with conduction defects. METHODS HEK293 cells and HL-1 cardiomyocytes were transiently transfected with either Lamin A or D243Gfs*4 tagged with GFP (or mCherry). D243Gfs*4 expression, cellular localization and its effects on diverse cellular mechanisms were evaluated with western blotting, laser-scanning confocal microscopy and video-imaging analysis in single cells. RESULTS When expressed in HEK293 cells, GFP- (or mCherry)-tagged LMNA D243Gfs*4 colocalized with calnexin within the ER. ER mislocalization of LMNA D243Gfs*4 did not significantly induce ER stress response, abnormal Ca2+ handling and apoptosis when compared with HEK293 cells expressing another truncated mutant of LMNA (R321X) which similarly accumulates within the ER. Of note, HEK293-LMNA D243Gfs*4 cells showed a significant reduction of connexin 43 (CX43) expression level, which was completely rescued by activation of the WNT/β-catenin signaling pathway. When expressed in HL-1 cardiomyocytes, D243Gfs*4 significantly impaired the spontaneous Ca2+ oscillations recorded in these cells as result of propagation of the depolarizing waves through the gap junctions between non-transfected cells surrounding a cell harboring the mutation. Furthermore, mCh-D243Gfs*4 HL-1 cardiomyocytes showed reduced CX43-dependent Lucifer Yellow (LY) loading and propagation. Of note, activation of β-catenin rescued both LY loading and LMNA D243Gfs*4 -HL-1 cells spontaneous activity propagation. CONCLUSION Overall, the present results clearly indicate the involvement of the aberrant CX43 expression/activity as a pathogenic mechanism for the conduction defects associated to this LMNA truncating alteration.
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Affiliation(s)
- Andrea Gerbino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Irene Bottillo
- Medical Genetics, Department of Molecular Medicine, Sapienza University, San Camillo-Forlanini Hospital, Rome, Italy
| | - Serena Milano
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Martina Lipari
- Medical Genetics, Department of Molecular Medicine, Sapienza University, San Camillo-Forlanini Hospital, Rome, Italy
| | - Roberta De Zio
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Silvia Morlino
- Medical Genetics, Department of Molecular Medicine, Sapienza University, San Camillo-Forlanini Hospital, Rome, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Giuseppe Procino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Federica Re
- Cardiology Division, Cardiac Arrhythmia Center and Cardiomyopathies Unit, San Camillo-Forlanini Hospital, Rome, Italy
| | - Elisabetta Zachara
- Cardiology Division, Cardiac Arrhythmia Center and Cardiomyopathies Unit, San Camillo-Forlanini Hospital, Rome, Italy
| | - Paola Grammatico
- Medical Genetics, Department of Molecular Medicine, Sapienza University, San Camillo-Forlanini Hospital, Rome, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Monica Carmosino
- Department of Sciences, University of Basilicata, Via dell'Ateneo Lucano, Potenza, Italy
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14
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Simone L, Gargano CD, Pisani F, Cibelli A, Mola MG, Frigeri A, Svelto M, Nicchia GP. Aquaporin-1 inhibition reduces metastatic formation in a mouse model of melanoma. J Cell Mol Med 2017; 22:904-912. [PMID: 29044946 PMCID: PMC5783831 DOI: 10.1111/jcmm.13378] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 08/16/2017] [Indexed: 01/14/2023] Open
Abstract
Aquaporin-1 (AQP1) is a proangiogenic water channel protein promoting endothelial cell migration. We previously reported that AQP1 silencing by RNA interference reduces angiogenesis-dependent primary tumour growth in a mouse model of melanoma. In this study, we tested the hypothesis that AQP1 inhibition also affects animal survival and lung nodule formation. Melanoma was induced by injecting B16F10 cells into the back of C57BL6J mice. Intratumoural injection of AQP1 siRNA and CTRL siRNA was performed 10 days after tumour cell implantation. Lung nodule formation was analysed after the death of the mice. Western blot was used to quantify HIF-1α, caspase-3 (CASP3) and metalloproteinase-2 (MMP2) protein levels. We found that AQP1 knock-down (KD) strongly inhibited metastatic lung nodule formation. Moreover, AQP1 siRNA-treated mice showed a twofold survival advantage compared to mice receiving CTRL siRNAs. The reduced AQP1-dependent tumour angiogenesis caused a hypoxic condition, evaluated by HIF-1α significant increase, in turn causing an increased level of apoptosis in AQP1 KD tumours, assessed by CASP3 quantification and DNA fragmentation. Importantly, a decreased level of MMP2 after AQP1 KD indicated a decreased activity against extracellular matrix associated with reduced vascularization and metastatic formation. In conclusion, these findings highlight an additional role for AQP1 as an important determinant of tumour dissemination by facilitating tumour cell extravasation and metastatic formation. This study adds knowledge on the role played by AQP1 in tumour biology and supports the view of AQP1 as a potential drug target for cancer therapy.
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Affiliation(s)
- Laura Simone
- IRCCS Casa Sollievo della Sofferenza, Institute for Stem Cell Biology, Regenerative Medicine and Innovative Therapies (ISBReMIT), San Giovanni Rotondo, FG, Italy.,Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Concetta Domenica Gargano
- Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Francesco Pisani
- Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Antonio Cibelli
- Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Antonio Frigeri
- School of Medicine, Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari "Aldo Moro", Bari, BA, Italy.,Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, New York, Bronx, NY, USA
| | - Maria Svelto
- Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy.,Institute of Biomembranes and Bioenergetics, National Research Council, Bari, BA, Italy.,National Institute of Biostructures and Biosystems (INBB), Rome, Italy
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy.,Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, New York, Bronx, NY, USA
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15
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Pisani F, Cammalleri M, Dal Monte M, Locri F, Mola MG, Nicchia GP, Frigeri A, Bagnoli P, Svelto M. Potential role of the methylation of VEGF gene promoter in response to hypoxia in oxygen-induced retinopathy: beneficial effect of the absence of AQP4. J Cell Mol Med 2017; 22:613-627. [PMID: 28940930 PMCID: PMC5742711 DOI: 10.1111/jcmm.13348] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Accepted: 07/11/2017] [Indexed: 12/16/2022] Open
Abstract
Hypoxia‐dependent accumulation of vascular endothelial growth factor (VEGF) plays a major role in retinal diseases characterized by neovessel formation. In this study, we investigated whether the glial water channel Aquaporin‐4 (AQP4) is involved in the hypoxia‐dependent VEGF upregulation in the retina of a mouse model of oxygen‐induced retinopathy (OIR). The expression levels of VEGF, the hypoxia‐inducible factor‐1α (HIF‐1α) and the inducible form of nitric oxide synthase (iNOS), the production of nitric oxide (NO), the methylation status of the HIF‐1 binding site (HBS) in the VEGF gene promoter, the binding of HIF‐1α to the HBS, the retinal vascularization and function have been determined in the retina of wild‐type (WT) and AQP4 knock out (KO) mice under hypoxic (OIR) or normoxic conditions. In response to 5 days of hypoxia, WT mice were characterized by (i) AQP4 upregulation, (ii) increased levels of VEGF, HIF‐1α, iNOS and NO, (iii) pathological angiogenesis as determined by engorged retinal tufts and (iv) dysfunctional electroretinogram (ERG). AQP4 deletion prevents VEGF, iNOS and NO upregulation in response to hypoxia thus leading to reduced retinal damage although in the presence of high levels of HIF‐1α. In AQP4 KO mice, HBS demethylation in response to the beginning of hypoxia is lower than in WT mice reducing the binding of HIF‐1α to the VEGF gene promoter. We conclude that in the absence of AQP4, an impaired HBS demethylation prevents HIF‐1 binding to the VEGF gene promoter and the relative VEGF transactivation, reducing the VEGF‐induced retinal damage in response to hypoxia.
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Affiliation(s)
- Francesco Pisani
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | | | | | - Filippo Locri
- Department of Biology, University of Pisa, Pisa, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Grazia Paola Nicchia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Antonio Frigeri
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, Bari, Italy
| | - Paola Bagnoli
- Department of Biology, University of Pisa, Pisa, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy.,Institute of Biomembranes and Bioenergetics, National Research Council, Bari, Italy
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De Bellis M, Pisani F, Mola MG, Rosito S, Simone L, Buccoliero C, Trojano M, Nicchia GP, Svelto M, Frigeri A. Translational readthrough generates new astrocyte AQP4 isoforms that modulate supramolecular clustering, glial endfeet localization, and water transport. Glia 2017; 65:790-803. [PMID: 28206694 DOI: 10.1002/glia.23126] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 01/02/2017] [Accepted: 01/25/2017] [Indexed: 11/10/2022]
Abstract
Regulation of water homeostasis is a central feature of central nervous system pathophysiology. In this context, several lines of evidence suggest a crucial role for the water channel aquaporin-4 (AQP4) and its plasma membrane supramolecular organization as the key element. Here, we demonstrate the expression in tissues of additional isoforms of AQP4 characterized by a C-terminal extension generated by programmed translational readthrough. These extended isoforms (AQP4ex) display a perivascular polarization and expression in dystrophin-dependent pools. AQP4ex reduces supramolecular clustering tendency and allows AQP4 interactions with syntrophin. Furthermore, site-directed mutagenesis of two serines in the extended C-terminus of AQP4ex showed potential regulation of water permeability by phosphorylation. Finally, AQP4ex expression can be positively modulated by gentamicin treatment, demonstrating the possibility of regulating the AQP4 translational readthrough frequency. This novel regulatory mechanism could have important pathophysiological implications for conditions in which alternations have been reported in AQP4 structure.
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Affiliation(s)
- Manuela De Bellis
- Department of Bioscience, Biotechnologies and Biopharmaceutic and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Francesco Pisani
- Department of Bioscience, Biotechnologies and Biopharmaceutic and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnologies and Biopharmaceutic and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Stefania Rosito
- Department of Bioscience, Biotechnologies and Biopharmaceutic and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Laura Simone
- Department of Bioscience, Biotechnologies and Biopharmaceutic and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy.,IRCCS "Casa Sollievo della Sofferenza", Research Hospital, San Giovanni Rotondo, Foggia, Italy
| | - Cinzia Buccoliero
- Department of Bioscience, Biotechnologies and Biopharmaceutic and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Maria Trojano
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnologies and Biopharmaceutic and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy.,Dominick P. Purpura Department of Neuroscience, 840 Kennedy Center, Bronx, New York
| | - Maria Svelto
- Department of Bioscience, Biotechnologies and Biopharmaceutic and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Antonio Frigeri
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, University of Bari Aldo Moro, Bari, Italy.,Dominick P. Purpura Department of Neuroscience, 840 Kennedy Center, Bronx, New York
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17
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Pisani F, Simone L, Gargano CD, De Bellis M, Cibelli A, Mola MG, Catacchio G, Frigeri A, Svelto M, Nicchia GP. Role of the H-bond between L53 and T56 for Aquaporin-4 epitope in Neuromyelitis Optica. Biochim Biophys Acta Biomembr 2016; 1859:368-376. [PMID: 28027883 DOI: 10.1016/j.bbamem.2016.12.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 12/13/2016] [Accepted: 12/23/2016] [Indexed: 11/29/2022]
Abstract
Aquaporin-4 (AQP4) is the CNS water channel organized into well-ordered protein aggregates called Orthogonal Arrays of Particles (OAPs). Neuromyelitis Optica (NMO) is an autoimmune disease caused by anti-OAP autoantibodies (AQP4-IgG). Molecular Dynamics (MD) simulations have identified an H-bond between L53 and T56 as the key for AQP4 epitope and therefore of potential interest for drug design in NMO field. In the present study, we have experimentally tested this MD-prediction using the classic mutagenesis approach. We substituted T56 with V56 and tested this mutant for AQP4 aggregates and AQP4-IgG binding. gSTED super-resolution microscopy showed that the mutation does not affect AQP4 aggregate dimension; immunofluorescence and cytofluorimetric analysis demonstrated its unaltered AQP4-IgG binding, therefore invalidating the MD-prediction. We later investigated whether AQP4, expressed in Sf9 insect and HEK-293F cells, is able to correctly aggregate before and after the purification steps usually applied to obtain AQP4 crystal. The results demonstrated that AQP4-IgG recognizes AQP4 expressed in Sf9 and HEK-293F cells by immunofluorescence even though BN-PAGE analysis showed that AQP4 forms smaller aggregates when expressed in insect cells compared to mammalian cell lines. Notably, after AQP4 purification, from both insect and HEK-293F cells, no aggregates are detectable by BN-PAGE and AQP4-IgG binding is impaired in sandwich ELISA assays. All together these results indicate that 1) the MD prediction under analysis is not supported by experimental data and 2) the procedure to obtain AQP4 crystals might affect its native architecture and, as a consequence, MD simulations. In conclusion, given the complex nature of the AQP4 epitope, MD might not be the suitable for molecular medicine advances in NMO.
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Affiliation(s)
- Francesco Pisani
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Laura Simone
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy; IRCCS "Casa Sollievo della Sofferenza", Research Hospital, San Giovanni Rotondo, Foggia, Italy
| | - Concetta Domenica Gargano
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Manuela De Bellis
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Antonio Cibelli
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Giacomo Catacchio
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy
| | - Antonio Frigeri
- School of Medicine, Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari "Aldo Moro", Bari, Italy; Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY, USA
| | - Maria Svelto
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy; Institute of Biomembranes and Bioenergetics, National Research Council, Bari, Italy; National Institute of Biostructures and Biosystems (INBB), Rome, Italy
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy; Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY, USA.
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18
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Posati T, Pistone A, Saracino E, Formaggio F, Mola MG, Troni E, Sagnella A, Nocchetti M, Barbalinardo M, Valle F, Bonetti S, Caprini M, Nicchia GP, Zamboni R, Muccini M, Benfenati V. A Nanoscale Interface Promoting Molecular and Functional Differentiation of Neural Cells. Sci Rep 2016; 6:31226. [PMID: 27503424 PMCID: PMC4977496 DOI: 10.1038/srep31226] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 07/04/2016] [Indexed: 12/11/2022] Open
Abstract
Potassium channels and aquaporins expressed by astrocytes are key players in the maintenance of cerebral homeostasis and in brain pathophysiologies. One major challenge in the study of astrocyte membrane channels in vitro, is that their expression pattern does not resemble the one observed in vivo. Nanostructured interfaces represent a significant resource to control the cellular behaviour and functionalities at micro and nanoscale as well as to generate novel and more reliable models to study astrocytes in vitro. However, the potential of nanotechnologies in the manipulation of astrocytes ion channels and aquaporins has never been previously reported. Hydrotalcite-like compounds (HTlc) are layered materials with increasing potential as biocompatible nanoscale interface. Here, we evaluate the effect of the interaction of HTlc nanoparticles films with primary rat neocortical astrocytes. We show that HTlc films are biocompatible and do not promote gliotic reaction, while favouring astrocytes differentiation by induction of F-actin fibre alignment and vinculin polarization. Western Blot, Immunofluorescence and patch-clamp revealed that differentiation was accompanied by molecular and functional up-regulation of both inward rectifying potassium channel Kir 4.1 and aquaporin 4, AQP4. The reported results pave the way to engineering novel in vitro models to study astrocytes in a in vivo like condition.
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Affiliation(s)
- Tamara Posati
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), via Gobetti, 101, 40129, Bologna, Italy
| | - Assunta Pistone
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), via Gobetti, 101, 40129, Bologna, Italy
| | - Emanuela Saracino
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), via Gobetti, 101, 40129, Bologna, Italy
| | - Francesco Formaggio
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), via Gobetti, 101, 40129, Bologna, Italy
| | - Maria Grazia Mola
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari “Aldo Moro”, Via Amendola 165/A, 70126, Bari, Italy
| | - Elisabetta Troni
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), via Gobetti, 101, 40129, Bologna, Italy
| | - Anna Sagnella
- Laboratorio di Micro e Submicro Tecnologie abilitanti dell’Emilia-Romagna (MIST E-R), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - Morena Nocchetti
- Dipartimento di Scienze Farmaceutiche, University of Perugia, Via del Liceo 1, 06123, Perugia, Italy
| | - Marianna Barbalinardo
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), via Gobetti, 101, 40129, Bologna, Italy
| | - Francesco Valle
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), via Gobetti, 101, 40129, Bologna, Italy
| | - Simone Bonetti
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), via Gobetti, 101, 40129, Bologna, Italy
| | - Marco Caprini
- Department of Pharmacy and Biotechnology, via S. Donato 19/2, University of Bologna, 40127 Bologna, Italy
| | - Grazia Paola Nicchia
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari “Aldo Moro”, Via Amendola 165/A, 70126, Bari, Italy
| | - Roberto Zamboni
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), via Gobetti, 101, 40129, Bologna, Italy
| | - Michele Muccini
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), via Gobetti, 101, 40129, Bologna, Italy
| | - Valentina Benfenati
- Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Sintesi Organica e la Fotoreattività (ISOF), via Gobetti, 101, 40129, Bologna, Italy
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19
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Nicchia GP, Pisani F, Simone L, Cibelli A, Mola MG, Dal Monte M, Frigeri A, Bagnoli P, Svelto M. Glio-vascular modifications caused by Aquaporin-4 deletion in the mouse retina. Exp Eye Res 2016; 146:259-268. [DOI: 10.1016/j.exer.2016.03.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/08/2016] [Accepted: 03/22/2016] [Indexed: 10/22/2022]
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20
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Mola MG, Sparaneo A, Gargano CD, Spray DC, Svelto M, Frigeri A, Scemes E, Nicchia GP. The speed of swelling kinetics modulates cell volume regulation and calcium signaling in astrocytes: A different point of view on the role of aquaporins. Glia 2015; 64:139-54. [PMID: 26413835 DOI: 10.1002/glia.22921] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 08/14/2015] [Accepted: 09/01/2015] [Indexed: 01/11/2023]
Abstract
Regulatory volume decrease (RVD) is a process by which cells restore their original volume in response to swelling. In this study, we have focused on the role played by two different Aquaporins (AQPs), Aquaporin-4 (AQP4), and Aquaporin-1 (AQP1), in triggering RVD and in mediating calcium signaling in astrocytes under hypotonic stimulus. Using biophysical techniques to measure water flux through the plasma membrane of wild-type (WT) and AQP4 knockout (KO) astrocytes and of an astrocyte cell line (DI TNC1) transfected with AQP4 or AQP1, we here show that AQP-mediated fast swelling kinetics play a key role in triggering and accelerating RVD. Using calcium imaging, we show that AQP-mediated fast swelling kinetics also significantly increases the amplitude of calcium transients inhibited by Gadolinium and Ruthenium Red, two inhibitors of the transient receptor potential vanilloid 4 (TRPV4) channels, and prevented by removing extracellular calcium. Finally, inhibition of TRPV4 or removal of extracellular calcium does not affect RVD. All together our study provides evidence that (1) AQP influenced swelling kinetics is the main trigger for RVD and in mediating calcium signaling after hypotonic stimulus together with TRPV4, and (2) calcium influx from the extracellular space and/or TRPV4 are not essential for RVD to occur in astrocytes.
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Affiliation(s)
- Maria Grazia Mola
- Department of Bioscience, Biotechnology, and Biopharmaceutics, University of Bari "Aldo Moro,", Bari, Italy
| | - Angelo Sparaneo
- Laboratory of Oncology, IRCCS Casa Sollievo Della Sofferenza, San Giovanni Rotondo, Italy
| | - Concetta Domenica Gargano
- Department of Bioscience, Biotechnology, and Biopharmaceutics, University of Bari "Aldo Moro,", Bari, Italy
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Maria Svelto
- Department of Bioscience, Biotechnology, and Biopharmaceutics, University of Bari "Aldo Moro,", Bari, Italy
| | - Antonio Frigeri
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.,Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari "Aldo Moro,", Bari, Italy
| | - Eliana Scemes
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnology, and Biopharmaceutics, University of Bari "Aldo Moro,", Bari, Italy.,Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA
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21
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Pisani F, Mola MG, Simone L, Rosito S, Alberga D, Mangiatordi GF, Lattanzi G, Nicolotti O, Frigeri A, Svelto M, Nicchia GP. Identification of a point mutation impairing the binding between aquaporin-4 and neuromyelitis optica autoantibodies. J Biol Chem 2014; 289:30578-30589. [PMID: 25239624 DOI: 10.1074/jbc.m114.582221] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuromyelitis optica (NMO) is characterized by the presence of pathogenic autoantibodies (NMO-IgGs) against supra-molecular assemblies of aquaporin-4 (AQP4), known as orthogonal array of particles (OAPs). NMO-IgGs have a polyclonal origin and recognize different conformational epitopes involving extracellular AQP4 loops A, C, and E. Here we hypothesize a pivotal role for AQP4 transmembrane regions (TMs) in epitope assembly. On the basis of multialignment analysis, mutagenesis, NMO-IgG binding, and cytotoxicity assay, we have disclosed the key role of aspartate 69 (Asp(69)) of TM2 for NMO-IgG epitope assembly. Mutation of Asp(69) to histidine severely impairs NMO-IgG binding for 85.7% of the NMO patient sera analyzed here. Although Blue Native-PAGE, total internal reflection fluorescence microscopy, and water transport assays indicate that the OAP Asp(69) mutant is similar in structure and function to the wild type, molecular dynamic simulations have revealed that the D(69)H mutation has the effect of altering the structural rearrangements of extracellular loop A. In conclusion, Asp(69) is crucial for the spatial control of loop A, the particular molecular conformation of which enables the assembly of NMO-IgG epitopes. These findings provide additional clues for new strategies for NMO treatment and a wealth of information to better approach NMO pathogenesis.
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Affiliation(s)
- Francesco Pisani
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro," 70126 Bari
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro," 70126 Bari
| | - Laura Simone
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro," 70126 Bari
| | - Stefania Rosito
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro," 70126 Bari
| | - Domenico Alberga
- Dipartimento Interateneo di Fisica "M. Merlin", INFN and TIRES, Università di Bari "Aldo Moro", via Orabona, 4, 70126 Bari, Italy
| | - Giuseppe Felice Mangiatordi
- Dipartimento di Farmacia-Scienze del Farmaco, Via Orabona, 4, Università di Bari "Aldo Moro", Bari, 70126 Bari, and
| | - Gianluca Lattanzi
- Dipartimento Interateneo di Fisica "M. Merlin", INFN and TIRES, Università di Bari "Aldo Moro", via Orabona, 4, 70126 Bari, Italy
| | - Orazio Nicolotti
- Dipartimento di Farmacia-Scienze del Farmaco, Via Orabona, 4, Università di Bari "Aldo Moro", Bari, 70126 Bari, and
| | - Antonio Frigeri
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro," 70126 Bari
| | - Maria Svelto
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro," 70126 Bari
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro," 70126 Bari,.
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22
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Tamma G, Lasorsa D, Trimpert C, Ranieri M, Di Mise A, Mola MG, Mastrofrancesco L, Devuyst O, Svelto M, Deen PMT, Valenti G. A protein kinase A-independent pathway controlling aquaporin 2 trafficking as a possible cause for the syndrome of inappropriate antidiuresis associated with polycystic kidney disease 1 haploinsufficiency. J Am Soc Nephrol 2014; 25:2241-53. [PMID: 24700872 DOI: 10.1681/asn.2013111234] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Renal water reabsorption is controlled by arginine vasopressin (AVP), which binds to V2 receptors, resulting in protein kinase A (PKA) activation, phosphorylation of aquaporin 2 (AQP2) at serine 256, and translocation of AQP2 to the plasma membrane. However, AVP also causes dephosphorylation of AQP2 at S261. Recent studies showed that cyclin-dependent kinases (cdks) can phosphorylate AQP2 peptides at S261 in vitro. We investigated the possible role of cdks in the phosphorylation of AQP2 and identified a new PKA-independent pathway regulating AQP2 trafficking. In ex vivo kidney slices and MDCK-AQP2 cells, R-roscovitine, a specific inhibitor of cdks, increased pS256 levels and decreased pS261 levels. The changes in AQP2 phosphorylation status were paralleled by increases in cell surface expression of AQP2 and osmotic water permeability in the absence of forskolin stimulation. R-Roscovitine did not alter cAMP-dependent PKA activity but specifically reduced protein phosphatase 2A (PP2A) expression and activity in MDCK cells. Notably, we found reduced PP2A expression and activity and reduced pS261 levels in Pkd1(+/-) mice displaying a syndrome of inappropriate antidiuresis with high levels of pS256, despite unchanged AVP and cAMP. Similar to previous findings in Pkd1(+/-) mice, R-roscovitine treatment caused a significant decrease in intracellular calcium in MDCK cells. Our data indicate that reduced activity of PP2A, secondary to reduced intracellular Ca(2+) levels, promotes AQP2 trafficking independent of the AVP-PKA axis. This pathway may be relevant for explaining pathologic states characterized by inappropriate AVP secretion and positive water balance.
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Affiliation(s)
- Grazia Tamma
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy;
| | - Domenica Lasorsa
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Christiane Trimpert
- Department of Physiology, Radboud University Medical Centre, Nijmegen, The Netherlands; and
| | - Marianna Ranieri
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Annarita Di Mise
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Maria Grazia Mola
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Lisa Mastrofrancesco
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Olivier Devuyst
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Maria Svelto
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Peter M T Deen
- Department of Physiology, Radboud University Medical Centre, Nijmegen, The Netherlands; and
| | - Giovanna Valenti
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
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23
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De Bellis M, Pisani F, Mola MG, Basco D, Catalano F, Nicchia GP, Svelto M, Frigeri A. A novel human aquaporin-4 splice variant exhibits a dominant-negative activity: a new mechanism to regulate water permeability. Mol Biol Cell 2013; 25:470-80. [PMID: 24356448 PMCID: PMC3923639 DOI: 10.1091/mbc.e13-06-0331] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
An alternatively spliced transcript of human AQP4 that lacks exon 4 is identified. In transfected cells, AQP4-Δ4 shows no water transport properties, is retained in the ER, and has a dominant-negative effect on full-length AQP4. In skeletal muscles, AQP4-Δ4 mRNA expression inversely correlates with the level of AQP4 protein in different muscles. Two major isoforms of aquaporin-4 (AQP4) have been described in human tissue. Here we report the identification and functional analysis of an alternatively spliced transcript of human AQP4, AQP4-Δ4, that lacks exon 4. In transfected cells AQP4-Δ4 is mainly retained in the endoplasmic reticulum and shows no water transport properties. When AQP4-Δ4 is transfected into cells stably expressing functional AQP4, the surface expression of the full-length protein is reduced. Furthermore, the water transport activity of the cotransfectants is diminished in comparison to transfectants expressing only AQP4. The observed down-regulation of both the expression and water channel activity of AQP4 is likely to originate from a dominant-negative effect caused by heterodimerization between AQP4 and AQP4-Δ4, which was detected in coimmunoprecipitation studies. In skeletal muscles, AQP4-Δ4 mRNA expression inversely correlates with the level of AQP4 protein and is physiologically associated with different types of skeletal muscles. The expression of AQP4-Δ4 may represent a new regulatory mechanism through which the cell-surface expression and therefore the activity of AQP4 can be physiologically modulated.
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Affiliation(s)
- Manuela De Bellis
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro," 70126 Bari, Italy Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland M. Sarcone Hospital, 70038 Terlizzi, Bari, Italy
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24
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Basco D, Blaauw B, Pisani F, Sparaneo A, Nicchia GP, Mola MG, Reggiani C, Svelto M, Frigeri A. AQP4-dependent water transport plays a functional role in exercise-induced skeletal muscle adaptations. PLoS One 2013; 8:e58712. [PMID: 23520529 PMCID: PMC3592820 DOI: 10.1371/journal.pone.0058712] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 02/05/2013] [Indexed: 02/07/2023] Open
Abstract
In this study we assess the functional role of Aquaporin-4 (AQP4) in the skeletal muscle by analyzing whether physical activity modulates AQP4 expression and whether the absence of AQP4 has an effect on osmotic behavior, muscle contractile properties, and physical activity. To this purpose, rats and mice were trained on the treadmill for 10 (D10) and 30 (D30) days and tested with exercise to exhaustion, and muscles were used for immunoblotting, RT-PCR, and fiber-type distribution analysis. Taking advantage of the AQP4 KO murine model, functional analysis of AQP4 was performed on dissected muscle fibers and sarcolemma vesicles. Moreover, WT and AQP4 KO mice were subjected to both voluntary and forced activity. Rat fast-twitch muscles showed a twofold increase in AQP4 protein in D10 and D30 rats compared to sedentary rats. Such increase positively correlated with the animal performance, since highest level of AQP4 protein was found in high runner rats. Interestingly, no shift in muscle fiber composition nor an increase in AQP4-positive fibers was found. Furthermore, no changes in AQP4 mRNA after exercise were detected, suggesting that post-translational events are likely to be responsible for AQP4 modulation. Experiments performed on AQP4 KO mice revealed a strong impairment in osmotic responses as well as in forced and voluntary activities compared to WT mice, even though force development amplitude and contractile properties were unvaried. Our findings definitively demonstrate the physiological role of AQP4 in supporting muscle contractile activity and metabolic changes that occur in fast-twitch skeletal muscle during prolonged exercise.
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Affiliation(s)
- Davide Basco
- Department of Bioscience, Biotechnologies and Biopharmaceutics and Center of Excellence in Comparative Genomics (CEGBA), University of Bari, Bari, Italy
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25
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Procino G, Barbieri C, Carmosino M, Tamma G, Milano S, De Benedictis L, Mola MG, Lazo-Fernandez Y, Valenti G, Svelto M. Fluvastatin modulates renal water reabsorption in vivo through increased AQP2 availability at the apical plasma membrane of collecting duct cells. Pflugers Arch 2011; 462:753-66. [PMID: 21858457 DOI: 10.1007/s00424-011-1007-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 07/28/2011] [Accepted: 08/01/2011] [Indexed: 01/20/2023]
Abstract
X-linked nephrogenic diabetes insipidus (XNDI), a severe pathological condition characterized by greatly impaired urine-concentrating ability of the kidney, is caused by inactivating mutations in the V2 vasopressin receptor (V2R) gene. The lack of functional V2Rs prevents vasopressin-induced shuttling of aquaporin-2 (AQP2) water channels to the apical plasma membrane of kidney collecting duct principal cells, thus promoting water reabsorption from urine to the interstitium. At present, no specific pharmacological therapy exists for the treatment of XNDI. We have previously reported that the cholesterol-lowering drug lovastatin increases AQP2 membrane expression in renal cells in vitro. Here we report the novel finding that fluvastatin, another member of the statins family, greatly increases kidney water reabsorption in vivo in mice in a vasopressin-independent fashion. Consistent with this observation, fluvastatin is able to increase AQP2 membrane expression in the collecting duct of treated mice. Additional in vivo and in vitro experiments indicate that these effects of fluvastatin are most likely caused by fluvastatin-dependent changes in the prenylation status of key proteins regulating AQP2 trafficking in collecting duct cells. We identified members of the Rho and Rab families of proteins as possible candidates whose reduced prenylation might result in the accumulation of AQP2 at the plasma membrane. In conclusion, these results strongly suggest that fluvastatin, or other drugs of the statin family, may prove useful in the therapy of XNDI.
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Affiliation(s)
- Giuseppe Procino
- Department of General and Environmental Physiology, University of Bari, Bari, Italy.
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26
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Abstract
Aquaporins form water channels that play major roles in a variety of physiological processes so that altered expression or function may underlie pathological conditions. In order to identify compounds that modulate aquaporin function, we have implemented a functional assay based on rapid measurement of osmotically induced cell volume changes to screen several libraries of diverse drugs. The time course of fluorescence changes in calcein-loaded cells was analyzed during an osmotic challenge using a 96-multiwell fluorescence plate reader. This system was validated using astrocyte primary cultures and fibroblasts that strongly express endogenous AQP4 and AQP1 proteins, respectively, as well as AQP4-transfected cells. We screened 3575 compounds, including 418 FDA-approved and commercially available drugs, for their effect on AQP-mediated water transport. Primary screening yielded 10 compounds that affected water transport activity in both astrocytes and AQP4-transfected cells and 42 compounds that altered cell volume regulation in astrocytes. Selected drugs were then analyzed on AQP1-expressing erythrocytes and AQP4-expressing membrane vesicles by stopped-flow light scattering. Four molecules of the National Cancer Institute's chemical library (NSC164914, NSC670229, NSC168597, NSC301460) were identified that differentially affected both AQP4 and AQP1 mediated water transport, with EC50 values between 20 and 50 microM. This fluorescence microplate reader-based assay may, thus, provide a platform for high-throughput screening which, when coupled to a secondary evaluation to confirm target specificity, should allow discovery of AQP-specific compounds for novel therapeutic strategies in the treatment of water balance disorders.
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Affiliation(s)
- Maria Grazia Mola
- Department of General and Environmental Physiology and Centre of Excellence in Comparative Genomics (CEGBA), University of Bari, I-70126 Bari, Italy
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27
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Nicchia GP, Rossi A, Mola MG, Procino G, Frigeri A, Svelto M. Actin cytoskeleton remodeling governs aquaporin-4 localization in astrocytes. Glia 2009; 56:1755-66. [PMID: 18649401 DOI: 10.1002/glia.20724] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Aquaporin-4 (AQP4) is constitutively concentrated in the plasma membrane of the perivascular glial processes, and its expression is altered in certain pathological conditions associated with brain edema or altered glial migration. When astrocytes are grown in culture, they lose their characteristic star-like shape and AQP4 continuous plasma membrane localization observed in vivo. In this study, we differentiated primary astrocyte cultures with cAMP and lovastatin, both able to induce glial stellation through a reorganization of F-actin cytoskeleton, and obtained AQP4 selectively localized on the cell plasma membrane associated with an increase in the plasma membrane water transport level, but only cAMP induced an increase in AQP4 total protein expression. Phosphorylation experiments indicated that AQP4 in astrocytes is neither phosphorylated nor a substrate of PKA. Depolymerization of F-actin cytoskeleton performed by cytochalasin-D suggested that F-actin cytoskeleton plays a primary role for AQP4 plasma membrane localization and during cell adhesion. Finally, AQP4 knockdown does not compromise the ability of astrocytes to stellate in the presence of cAMP, indicating that astrocyte stellation is independent of AQP4.
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Affiliation(s)
- Grazia Paola Nicchia
- Department of General and Environmental Physiology, Centre of Excellence in Comparative Genomics (CEGBA), University of Bari, Bari, Italy.
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28
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Nicchia GP, Nico B, Camassa LMA, Mola MG, Loh N, Dermietzel R, Spray DC, Svelto M, Frigeri A. The role of aquaporin-4 in the blood-brain barrier development and integrity: studies in animal and cell culture models. Neuroscience 2005; 129:935-45. [PMID: 15561409 DOI: 10.1016/j.neuroscience.2004.07.055] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/23/2004] [Indexed: 02/09/2023]
Abstract
Aquaporin-4 (AQP4) is the major water channel expressed in brain perivascular astrocyte processes. Although the role of AQP4 in brain edema has been extensively investigated, little information exists regarding its functional role at the blood-brain barrier (BBB). The purpose of this work is to integrate previous and recent data regarding AQP4 expression during BBB formation and depending on BBB integrity, using several experimental models. Results from studies on the chick optic tectum, a well-established model of BBB development, and the effect of lipopolysaccharide on the BBB integrity and on perivascular AQP4 expression have been analyzed and discussed. Moreover, data on the BBB structure and AQP4 expression in murine models of Duchenne muscular dystrophy are reviewed. In particular, published results obtained from mdx(3cv) mice have been analyzed together with new data obtained from mdx mice in which all the dystrophin isoforms including DP71 are strongly reduced. Finally, the role of the endothelial component on AQP4 cellular expression and distribution has been investigated using rat primary astrocytes and brain capillary endothelial cell co-cultures as an in vitro model of BBB.
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Affiliation(s)
- G P Nicchia
- Department of General and Environmental Physiology and Centre of Excellence in Comparative Genomics (CEGBA), University of Bari, via Amendola 165/A, I-70126 Bari, Italy
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29
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Scalera V, Mola MG, Prezioso G. The kinetic mechanism of the glutamate-aspartate carrier in rat intestinal brush-border membrane vesicles: the role of potassium. J Bioenerg Biomembr 2002; 34:95-103. [PMID: 12018893 DOI: 10.1023/a:1015171824847] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The sodium dependent transport system for L-glutamate and L-aspartate localized in the apical part of rat enterocytes has previously been kinetically characterized (Prezioso, G., and Scalera, V. (1996). Biochim. Biophys. Acta 1279, 144-148). In this paper the mechanism by which the potassium cation specifically activates the L-glutamate-sodium cotransport process is investigated. Potassium has been found to act as an activator when it is present inside the membrane vesicles, while its presence outside is ineffective, and the effect is saturable. The kinetic parameters with respect to sodium and glutamate have been compared in the presence and in the absence of the activator. The results indicate that the ordered sodium-sodium glutamate mechanism is not altered by potassium, and that the activation is probably exerted on both the rate determining steps of the transport process. It is proposed that (1) a specific binding site for potassium is present on the inside hydrophilic part of the membrane carrier, (2) the binding of the effector accelerates the intramembrane rearrangement steps of both the disodium glutamate-carrier complex and the free carrier, (3) the affinity of the carrier is lowered with respect to sodium whereas it is increased for glutamate, and (4) K+ antiport is not performed by this carrier.
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Affiliation(s)
- V Scalera
- Dipartimento di Fisiologia Generale ed Ambientale, Università degli Studi di Bari, Italy.
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Calamita G, Mola MG, Gounon P, Jouve M, Bourguet J, Svelto M. Aquaporin-CHIP-related protein in frog urinary bladder: localization by confocal microscopy. J Membr Biol 1995; 143:267-71. [PMID: 7539501 DOI: 10.1007/bf00233455] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Aquaporin CHIP, a 28 kDa channel forming protein, has been proposed to function as water channel in both erythrocyte and kidney proximal tubule. Recently, we have reported that in frog urinary bladder, a model of the kidney collecting tubule, polyclonal antibodies against human erythrocyte CHIP recognize and immunoprecipitate a 30 kDa protein from the epithelial cell homogenate. In the present work confocal fluorescence microscopy was used to determine the cellular and subcellular localization of CHIP28-like proteins in the urinary epithelium. A clear labeling of the apical border was found after Triton X-100 permeabilization. The labeling was distributed throughout the apical domain and not restricted to specific domains of the membrane. The staining was also present in the deeper confocal sections where the fluorescence seems to be localized at the cellular contour. No difference in the labeling patterns was observed between resting and ADH-treated bladder. Specificity of the staining was confirmed by the absence of the labeling pattern when antiserum was preadsorbed on CHIP28 protein immobilized on Immobilon P stripes. Our results suggest that CHIP-like proteins are not proteins inserted in the apical membrane during the antidiuretic response. Moreover, we do not know whether the labeling was due to the presence of CHIP28 itself or an as-yet-unidentified protein sharing immunological analogies with aquaporin CHIP.
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Affiliation(s)
- G Calamita
- Istituto di Fisiologia Generale, Università degli studi di Bari, Italy
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Calamita G, Mola MG, Svelto M. Presence in frog urinary bladder of proteins immunologically related to the aquaporin-CHIP. Eur J Cell Biol 1994; 64:222-8. [PMID: 7529179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Aquaporin-CHIP, a 28 kDa channel forming protein already referred to as CHIP28, has been identified as the water channel in red blood cells as well as in mammalian renal tubule cells. Another member of the aquaporin family, WCH-CD, has been found in the apical membrane of collecting duct principal cells and may represent the ADH-sensitive water channel. The present study investigates the possible presence of CHIP28-like proteins in amphibian urinary bladder, where the presence of water channels has been postulated. For this purpose, we raised polyclonal antibodies against human erythrocyte CHIP28. Immune serum precipitated a protein of about 30 kDa from the whole homogenate of urinary epithelial cells. By Western blotting, in addition to the reaction with the 30 kDa component, the immune serum reacted with higher molecular weight components from the bladder homogenate. The 30 kDa band was detected by Western blot only in bladders having a high water permeability. Moreover, a 30 kDa protein was also recognized in frog red blood cell membranes by the anti-CHIP28 antibodies. In line with the immunoblotting studies, in immunohistofluorescence anti-CHIP28 antibodies stained frog red blood cells and urinary bladder epithelial cells. However, in whole tissue water permeability studies apical treatment with the anti-CHIP28 antibodies had no effect on either the hydrosmotic response to ADH or on the basal net water flow of the bladder. All together, these results indicate the presence in the frog red blood cells and urinary epithelium of proteins sharing immunological analogies with aquaporin-CHIP.
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Affiliation(s)
- G Calamita
- Istituto di Fisiologia Generale, Università di Bari, Italy
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