1
|
Caballé RB, Bortolozzi M. New perspectives for gene therapy of the X-linked form of Charcot-Marie-Tooth disease. Mol Ther Methods Clin Dev 2024; 32:101184. [PMID: 38292668 PMCID: PMC10827554 DOI: 10.1016/j.omtm.2023.101184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Affiliation(s)
- Rafael Balada Caballé
- University of Padua, Department of Physics and Astronomy “G. Galilei”, Padua, Italy
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
| | - Mario Bortolozzi
- University of Padua, Department of Physics and Astronomy “G. Galilei”, Padua, Italy
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Padova Neuroscience Center (PNC), Padua, Italy
| |
Collapse
|
2
|
Bayraktar E, Bortolozzi M. Measuring Connexin Hemichannel Opening in Response to an InsP3-Mediated Cytosolic Ca 2+ Increase. Methods Mol Biol 2024; 2801:189-197. [PMID: 38578422 DOI: 10.1007/978-1-0716-3842-2_14] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
The opening of connexin hemichannels (HCs) expressed at the plasma membrane of mammalian cells is regulated by a number of physiological parameters, including extracellular and intracellular Ca2+ ions. Submicromolar variations of the cytosolic Ca2+ concentration ([Ca2+]c) are per se sufficient to trigger extracellular bursts of messenger molecules through connexin HCs, thus mediating paracrine signaling. In this chapter, we present a quantitative method to measure the opening dynamics of connexin HCs expressed in a single HeLa cell upon stimulation by a canonical InsP3-mediated [Ca2+]c transient. The protocol relies on a combination of Ca2+ imaging and patch-clamp techniques. The insights gained from our method are expected to make a significant contribution to understanding the structure-function relationship of connexin HCs. The protocol is also suitable to screen candidate therapeutic compounds to treat connexin-related diseases linked to HC dysfunction.
Collapse
Affiliation(s)
- Erva Bayraktar
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padova, Italy
- Veneto Institute of Molecular Medicine (VIMM), Padova, Italy
| | - Mario Bortolozzi
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padova, Italy.
- Veneto Institute of Molecular Medicine (VIMM), Padova, Italy.
| |
Collapse
|
3
|
Qi C, Lavriha P, Bayraktar E, Vaithia A, Schuster D, Pannella M, Sala V, Picotti P, Bortolozzi M, Korkhov VM. Structures of wild-type and selected CMT1X mutant connexin 32 gap junction channels and hemichannels. Sci Adv 2023; 9:eadh4890. [PMID: 37647412 PMCID: PMC10468125 DOI: 10.1126/sciadv.adh4890] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 07/27/2023] [Indexed: 09/01/2023]
Abstract
In myelinating Schwann cells, connection between myelin layers is mediated by gap junction channels (GJCs) formed by docked connexin 32 (Cx32) hemichannels (HCs). Mutations in Cx32 cause the X-linked Charcot-Marie-Tooth disease (CMT1X), a degenerative neuropathy without a cure. A molecular link between Cx32 dysfunction and CMT1X pathogenesis is still missing. Here, we describe the high-resolution cryo-electron cryo-myography (cryo-EM) structures of the Cx32 GJC and HC, along with two CMT1X-linked mutants, W3S and R22G. While the structures of wild-type and mutant GJCs are virtually identical, the HCs show a major difference: In the W3S and R22G mutant HCs, the amino-terminal gating helix partially occludes the pore, consistent with a diminished HC activity. Our results suggest that HC dysfunction may be involved in the pathogenesis of CMT1X.
Collapse
Affiliation(s)
- Chao Qi
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Pia Lavriha
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Erva Bayraktar
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Physics and Astronomy “G. Galilei”, University of Padua, Padua, Italy
| | - Anand Vaithia
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Dina Schuster
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Micaela Pannella
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Physics and Astronomy “G. Galilei”, University of Padua, Padua, Italy
| | - Valentina Sala
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
| | - Paola Picotti
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Mario Bortolozzi
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Physics and Astronomy “G. Galilei”, University of Padua, Padua, Italy
| | - Volodymyr M. Korkhov
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| |
Collapse
|
4
|
Qi C, Acosta Gutierrez S, Lavriha P, Othman A, Lopez-Pigozzi D, Bayraktar E, Schuster D, Picotti P, Zamboni N, Bortolozzi M, Gervasio FL, Korkhov VM. Structure of the connexin-43 gap junction channel in a putative closed state. eLife 2023; 12:RP87616. [PMID: 37535063 PMCID: PMC10400079 DOI: 10.7554/elife.87616] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/04/2023] Open
Abstract
Gap junction channels (GJCs) mediate intercellular communication by connecting two neighbouring cells and enabling direct exchange of ions and small molecules. Cell coupling via connexin-43 (Cx43) GJCs is important in a wide range of cellular processes in health and disease (Churko and Laird, 2013; Liang et al., 2020; Poelzing and Rosenbaum, 2004), yet the structural basis of Cx43 function and regulation has not been determined until now. Here, we describe the structure of a human Cx43 GJC solved by cryo-EM and single particle analysis at 2.26 Å resolution. The pore region of Cx43 GJC features several lipid-like densities per Cx43 monomer, located close to a putative lateral access site at the monomer boundary. We found a previously undescribed conformation on the cytosolic side of the pore, formed by the N-terminal domain and the transmembrane helix 2 of Cx43 and stabilized by a small molecule. Structures of the Cx43 GJC and hemichannels (HCs) in nanodiscs reveal a similar gate arrangement. The features of the Cx43 GJC and HC cryo-EM maps and the channel properties revealed by molecular dynamics simulations suggest that the captured states of Cx43 are consistent with a closed state.
Collapse
Affiliation(s)
- Chao Qi
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Silvia Acosta Gutierrez
- Institute for the Physics of Living Systems, Institute of Structural and Molecular Biology, University College London, London, United Kingdom
- Institute for Bioengineering of Catalunya (IBEC), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Pia Lavriha
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Alaa Othman
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Diego Lopez-Pigozzi
- Department of Physics and Astronomy "G. Galilei", University of Padova, Padua, Italy
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
| | - Erva Bayraktar
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
| | - Dina Schuster
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Paola Picotti
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Nicola Zamboni
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Mario Bortolozzi
- Department of Physics and Astronomy "G. Galilei", University of Padova, Padua, Italy
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
| | - Francesco Luigi Gervasio
- Department of Chemistry, University College London, London, United Kingdom
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland
- ISPSO, University of Geneva, Geneva, Switzerland
| | - Volodymyr M Korkhov
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| |
Collapse
|
5
|
Imran SJ, Vagaska B, Kriska J, Anderova M, Bortolozzi M, Gerosa G, Ferretti P, Vrzal R. Aryl Hydrocarbon Receptor (AhR)-Mediated Signaling in iPSC-Derived Human Motor Neurons. Pharmaceuticals (Basel) 2022; 15:ph15070828. [PMID: 35890127 PMCID: PMC9321538 DOI: 10.3390/ph15070828] [Citation(s) in RCA: 0] [Impact Index Per Article: 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] [Received: 05/29/2022] [Revised: 06/26/2022] [Accepted: 07/01/2022] [Indexed: 12/04/2022] Open
Abstract
Exposure to environmental pollutants and endogenous metabolites that induce aryl hydrocarbon receptor (AhR) expression has been suggested to affect cognitive development and, particularly in boys, also motor function. As current knowledge is based on epidemiological and animal studies, in vitro models are needed to better understand the effects of these compounds in the human nervous system at the molecular level. Here, we investigated expression of AhR pathway components and how they are regulated by AhR ligands in human motor neurons. Motor neurons generated from human induced pluripotent stem cells (hiPSCs) were characterized at the molecular level and by electrophysiology. mRNA levels of AhR target genes, CYP1A1 and CYP1B1 (cytochromes P450 1A1/1B1), and AhR signaling components were monitored in hiPSCs and in differentiated neurons following treatment with AhR ligands, 2,3,7,8,-tetrachlodibenzo-p-dioxin (TCDD), L-kynurenine (L-Kyn), and kynurenic acid (KA), by RT-qPCR. Changes in AhR cellular localization and CYP1A1 activity in neurons treated with AhR ligands were also assessed. The neurons we generated express motor neuron-specific markers and are functional. Transcript levels of CYP1B1, AhR nuclear translocators (ARNT1 and ARNT2) and the AhR repressor (AhRR) change with neuronal differentiation, being significantly higher in neurons than hiPSCs. In contrast, CYP1A1 and AhR transcript levels are slightly lower in neurons than in hiPSCs. The response to TCDD treatment differs in hiPSCs and neurons, with only the latter showing significant CYP1A1 up-regulation. In contrast, TCDD slightly up-regulates CYP1B1 mRNA in hiPSCs, but downregulates it in neurons. Comparison of the effects of different AhR ligands on AhR and some of its target genes in neurons shows that L-Kyn and KA, but not TCDD, regulate AhR expression and differently affect CYP1A1 and CYP1B1 expression. Finally, although TCDD does not significantly affect AhR transcript levels, it induces AhR protein translocation to the nucleus and increases CYP1A1 activity. This is in contrast to L-Kyn and KA, which either do not affect or reduce, respectively, CYP1A1 activity. Expression of components of the AhR signaling pathway are regulated with neuronal differentiation and are differently affected by TCDD, suggesting that pluripotent stem cells might be less sensitive to this toxin than neurons. Crucially, AhR signaling is affected differently by TCDD and other AhR ligands in human motor neurons, suggesting that they can provide a valuable tool for assessing the impact of environmental pollutants.
Collapse
Affiliation(s)
- Saima Jalil Imran
- Department of Cell Biology and Genetics, Faculty of Science, 77147 Olomouc, Czech Republic
- Stem Cells and Regenerative Medicine Section, UCL Great Ormond Street Institute of Child Health, University College London, London WC1N 1EH, UK; (B.V.); (P.F.)
- Department of Cardiac, Thoracic, Vascular Sciences and Public Health, University of Padua, 35128 Padua, Italy;
- Correspondence: (S.J.I.); (R.V.); Tel.: +39-498212410 (S.J.I.); +420-58-5634904 (R.V.)
| | - Barbora Vagaska
- Stem Cells and Regenerative Medicine Section, UCL Great Ormond Street Institute of Child Health, University College London, London WC1N 1EH, UK; (B.V.); (P.F.)
| | - Jan Kriska
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, 14220 Prague, Czech Republic; (J.K.); (M.A.)
| | - Miroslava Anderova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, 14220 Prague, Czech Republic; (J.K.); (M.A.)
- Second Faculty of Medicine, Charles University, 15006 Prague, Czech Republic
| | - Mario Bortolozzi
- Department of Physics and Astronomy “G. Galilei”, University of Padua, 35131 Padua, Italy;
- Veneto Institute of Molecular Medicine (VIMM), 35129 Padua, Italy
| | - Gino Gerosa
- Department of Cardiac, Thoracic, Vascular Sciences and Public Health, University of Padua, 35128 Padua, Italy;
| | - Patrizia Ferretti
- Stem Cells and Regenerative Medicine Section, UCL Great Ormond Street Institute of Child Health, University College London, London WC1N 1EH, UK; (B.V.); (P.F.)
| | - Radim Vrzal
- Department of Cell Biology and Genetics, Faculty of Science, 77147 Olomouc, Czech Republic
- Correspondence: (S.J.I.); (R.V.); Tel.: +39-498212410 (S.J.I.); +420-58-5634904 (R.V.)
| |
Collapse
|
6
|
Di Nisio A, Pannella M, Vogiatzis S, Sut S, Dall'Acqua S, Rocca MS, Antonini A, Porzionato A, De Caro R, Bortolozzi M, Toni LD, Foresta C. Impairment of human dopaminergic neurons at different developmental stages by perfluoro-octanoic acid (PFOA) and differential human brain areas accumulation of perfluoroalkyl chemicals. Environ Int 2022; 158:106982. [PMID: 34781208 DOI: 10.1016/j.envint.2021.106982] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 11/09/2021] [Accepted: 11/10/2021] [Indexed: 06/13/2023]
Abstract
Perfluoroalkyl substances (PFASs) are synthetic chemicals widely used in industrial and consumer products. The environmental spreading of PFASs raises concerns for their impact on human health. In particular, the bioaccumulation in humans due to environmental exposure has been reported also in total brain samples and PFAS exposure has been associated with neurodevelopmental disorders. In this study we aimed to investigate the specific PFAS bioaccumulation in different brain areas. Our data reported major accumulation in the brainstem region, which is richly populated by dopaminergic neurons (DNs), in brain autopsy samples from people resident in a PFAS-polluted area of Italy. Since DNs are the main source of dopamine (DA) in the mammalian central nervous system (CNS), we evaluated the possible functional consequences of perfluoro-octanoic acid (PFOA) exposure in a human model of DNs obtained by differentiation of human induced pluripotent stem cells (hiPSCs). Particularly, we analyzed the specific effect of the exposure to PFOA for 24 h, at the concentration of 10 ng/ml, at 3 different steps of dopaminergic differentiation: the neuronal commitment phase (DP1), the neuronal precursor phase (DP2) and the mature dopaminergic differentiation phase (DP3). Interestingly, compared to untreated cells, exposure to PFOA was associated with a reduced expression of Tyrosine Hydroxylase (TH) and Neurofilament Heavy (NFH), both markers of dopaminergic maturation at DP2 phase. In addition, cells at DP3 phase exposed to PFOA showed a severe reduction in the expression of the Dopamine Transporter (DAT), functionally involved in pre-synaptic dopamine reuptake. In this proof-of-concept study we show a significant impact of PFOA exposure, mainly on the most sensitive stage of neural dopaminergic differentiation, prompting the way for further investigations more directly relevant to risk assessment of these chemicals.
Collapse
Affiliation(s)
| | | | - Stefania Vogiatzis
- Venetian Institute of Molecular Medicine - VIMM, Department of Physics and Astronomy, University of Padova, Italy
| | - Stefania Sut
- Department of Medicine, University of Padova, Padova, Italy
| | - Stefano Dall'Acqua
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy
| | | | - Angelo Antonini
- Department of Neuroscience, University of Padua, Padova, Italy
| | | | | | - Mario Bortolozzi
- Venetian Institute of Molecular Medicine - VIMM, Department of Physics and Astronomy, University of Padova, Italy
| | - Luca De Toni
- Department of Medicine, University of Padova, Padova, Italy.
| | - Carlo Foresta
- Department of Medicine, University of Padova, Padova, Italy
| |
Collapse
|
7
|
Donati V, Peres C, Nardin C, Scavizzi F, Raspa M, Ciubotaru CD, Bortolozzi M, Pedersen MG, Mammano F. Calcium Signaling in the Photodamaged Skin: In Vivo Experiments and Mathematical Modeling. Function (Oxf) 2021; 3:zqab064. [PMID: 35330924 PMCID: PMC8788836 DOI: 10.1093/function/zqab064] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 11/23/2021] [Accepted: 11/23/2021] [Indexed: 01/07/2023] Open
Abstract
The epidermis forms an essential barrier against a variety of insults. The overall goal of this study was to shed light not only on the effects of accidental epidermal injury, but also on the mechanisms that support laser skin resurfacing with intra-epidermal focal laser-induced photodamage, a widespread medical practice used to treat a range of skin conditions. To this end, we selectively photodamaged a single keratinocyte with intense, focused and pulsed laser radiation, triggering Ca2+ waves in the epidermis of live anesthetized mice with ubiquitous expression of a genetically encoded Ca2+ indicator. Waves expanded radially and rapidly, reaching up to eight orders of bystander cells that remained activated for tens of minutes, without displaying oscillations of the cytosolic free Ca2+ concentration ([Formula: see text]). By combining in vivo pharmacological dissection with mathematical modeling, we demonstrate that Ca2+ wave propagation depended primarily on the release of ATP, a prime damage-associated molecular patterns (DAMPs), from the hit cell. Increments of the [Formula: see text] in bystander cells were chiefly due to Ca2+ release from the endoplasmic reticulum (ER), downstream of ATP binding to P2Y purinoceptors. ATP-dependent ATP release though connexin hemichannels (HCs) affected wave propagation at larger distances, where the extracellular ATP concentration was reduced by the combined effect of passive diffusion and hydrolysis due to the action of ectonucleotidases, whereas pannexin channels had no role. Bifurcation analysis suggests basal keratinocytes have too few P2Y receptors (P2YRs) and/or phospholipase C (PLC) to transduce elevated extracellular ATP levels into inositol trisphosphate (IP3) production rates sufficiently large to sustain [Formula: see text] oscillations.
Collapse
Affiliation(s)
- Viola Donati
- Department of Physics and Astronomy “G. Galilei”, University of Padova, 35131 Padova, Italy
- Institute of Biochemistry and Cell Biology (IBBC)-CNR, 00015 Monterotondo (RM), Italy
| | - Chiara Peres
- Institute of Biochemistry and Cell Biology (IBBC)-CNR, 00015 Monterotondo (RM), Italy
| | - Chiara Nardin
- Institute of Biochemistry and Cell Biology (IBBC)-CNR, 00015 Monterotondo (RM), Italy
| | - Ferdinando Scavizzi
- Institute of Biochemistry and Cell Biology (IBBC)-CNR, 00015 Monterotondo (RM), Italy
| | - Marcello Raspa
- Institute of Biochemistry and Cell Biology (IBBC)-CNR, 00015 Monterotondo (RM), Italy
| | | | - Mario Bortolozzi
- Department of Physics and Astronomy “G. Galilei”, University of Padova, 35131 Padova, Italy
- Institute of Biochemistry and Cell Biology (IBBC)-CNR, 00015 Monterotondo (RM), Italy
- Foundation for Advanced Biomedical Research, Veneto Institute of Molecular Medicine (VIMM), 35129 Padova (PD), Italy
| | - Morten Gram Pedersen
- Department of Information Engineering, University of Padova, 35131 Padova (PD), Italy
- Department of Mathematics “Tullio Levi-Civita”, University of Padova, 35121 Padova (PD), Italy
| | - Fabio Mammano
- Department of Physics and Astronomy “G. Galilei”, University of Padova, 35131 Padova, Italy
- Institute of Biochemistry and Cell Biology (IBBC)-CNR, 00015 Monterotondo (RM), Italy
| |
Collapse
|
8
|
Abstract
Hair cells of the inner ear detect sound stimuli, inertial or gravitational forces by deflection of their apical stereocilia. A small number of stereociliary cation-selective mechanotransduction (MET) channels admit K+ and Ca2+ ions into the cytoplasm promoting hair cell membrane depolarization and, consequently, neurotransmitter release at the cell basolateral pole. Ca2+ influx into the stereocilia compartment is counteracted by the unusual w/a splicing variant of plasma-membrane calcium-pump isoform 2 (PMCA2) which, unlike other PMCA2 variants, increases only marginally its activity in response to a rapid variation of the cytoplasmic free Ca2+ concentration ([Ca2+]c). Missense mutations of PMCA2w/a cause deafness and loss of balance in humans. Mouse models in which the pump is genetically ablated or mutated show hearing and balance impairment, which correlates with defects in homeostatic regulation of stereociliary [Ca2+]c, decreased sensitivity of mechanotransduction channels to hair bundle displacement and progressive degeneration of the organ of Corti. These results highlight a critical role played by the PMCA2w/a pump in the control of hair cell function and survival, and provide mechanistic insight into the etiology of deafness and vestibular disorders.
Collapse
Affiliation(s)
- Mario Bortolozzi
- University of Padua, Department of Physics and Astronomy "G. Galilei", Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Padua, Italy; CNR Institute of Protein Biochemistry, Naples, Italy.
| | - Fabio Mammano
- University of Padua, Department of Physics and Astronomy "G. Galilei", Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Padua, Italy; CNR Institute of Cell Biology and Neurobiology, Monterotondo Scalo, Rome, Italy
| |
Collapse
|
9
|
Abstract
Connexin 32 (Cx32) is a fundamental protein in the peripheral nervous system (PNS) as its mutations cause the X-linked form of Charcot–Marie–Tooth disease (CMT1X), the second most common form of hereditary motor and sensory neuropathy and a demyelinating disease for which there is no effective therapy. Since mutations of the GJB1 gene encoding Cx32 were first reported in 1993, over 450 different mutations associated with CMT1X including missense, frameshift, deletion and non-sense ones have been identified. Despite the availability of a sizable number of studies focusing on normal and mutated Cx32 channel properties, the crucial role played by Cx32 in the PNS has not yet been elucidated, as well as the molecular pathogenesis of CMT1X. Is Cx32 fundamental during a particular phase of Schwann cell (SC) life? Are Cx32 paired (gap junction, GJ) channels in myelinated SCs important for peripheral nerve homeostasis? The attractive hypothesis that short coupling of adjacent myelin layers by Cx32 GJs is required for efficient diffusion of K+ and signaling molecules is still debated, while a growing body of evidence is supporting other possible functions of Cx32 in the PNS, mainly related to Cx32 unpaired channels (hemichannels), which could be involved in a purinergic-dependent pathway controlling myelination. Here we review the intriguing puzzle of findings about Cx32 function and dysfunction, discussing possible directions for future investigation.
Collapse
Affiliation(s)
- Mario Bortolozzi
- Department of Physics and Astronomy G. Galilei, University of Padua, Padua, Italy.,Venetian Institute of Molecular Medicine (VIMM), Padua, Italy.,Padova Neuroscience Center (PNC), Padua, Italy
| |
Collapse
|
10
|
Ford KL, Moorhouse EL, Bortolozzi M, Richards MA, Swietach P, Vaughan-Jones RD. Regional acidosis locally inhibits but remotely stimulates Ca2+ waves in ventricular myocytes. Cardiovasc Res 2018; 113:984-995. [PMID: 28339694 PMCID: PMC5852542 DOI: 10.1093/cvr/cvx033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 02/17/2017] [Indexed: 11/30/2022] Open
Abstract
Aims Spontaneous Ca2+ waves in cardiomyocytes are potentially arrhythmogenic. A
powerful controller of Ca2+ waves is the cytoplasmic H+
concentration ([H+]i), which fluctuates spatially and temporally
in conditions such as myocardial ischaemia/reperfusion. H+-control of
Ca2+ waves is poorly understood. We have therefore investigated how
[H+]i co-ordinates their initiation and frequency. Methods and results Spontaneous Ca2+ waves were imaged (fluo-3) in rat isolated ventricular
myocytes, subjected to modest Ca2+-overload. Whole-cell intracellular
acidosis (induced by acetate-superfusion) stimulated wave frequency. Pharmacologically
blocking sarcolemmal Na+/H+ exchange (NHE1) prevented this
stimulation, unveiling inhibition by H+. Acidosis also increased
Ca2+ wave velocity. Restricting acidosis to one end of a myocyte, using a
microfluidic device, inhibited Ca2+ waves in the acidic zone (consistent with
ryanodine receptor inhibition), but stimulated wave emergence elsewhere in the cell.
This remote stimulation was absent when NHE1 was selectively inhibited in the acidic
zone. Remote stimulation depended on a locally evoked, NHE1-driven rise of
[Na+]i that spread rapidly downstream. Conclusion Acidosis influences Ca2+ waves via inhibitory Hi+ and stimulatory Nai+ signals (the latter facilitating intracellular
Ca2+-loading through modulation of sarcolemmal
Na+/Ca2+ exchange activity). During spatial
[H+]i-heterogeneity, Hi+-inhibition dominates in acidic regions, while rapid
Nai+ diffusion stimulates waves in downstream, non-acidic
regions. Local acidosis thus simultaneously inhibits and stimulates arrhythmogenic
Ca2+-signalling in the same myocyte. If the principle of remote
H+-stimulation of Ca2+ waves also applies in multicellular
myocardium, it raises the possibility of electrical disturbances being driven remotely
by adjacent ischaemic areas, which are known to be intensely acidic.
Collapse
Affiliation(s)
- Kerrie L Ford
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, OX1 3PT, UK
| | - Emma L Moorhouse
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, OX1 3PT, UK
| | - Mario Bortolozzi
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, OX1 3PT, UK.,Department of Physics and Astronomy "G. Galilei", University of Padua, 35121 Padua, Italy
| | - Mark A Richards
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, OX1 3PT, UK
| | - Pawel Swietach
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, OX1 3PT, UK
| | - Richard D Vaughan-Jones
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, OX1 3PT, UK
| |
Collapse
|
11
|
Menegazzo L, Scattolini V, Cappellari R, Bonora BM, Albiero M, Bortolozzi M, Romanato F, Ceolotto G, Vigili de Kreutzeberg S, Avogaro A, Fadini GP. The antidiabetic drug metformin blunts NETosis in vitro and reduces circulating NETosis biomarkers in vivo. Acta Diabetol 2018; 55:593-601. [PMID: 29546579 DOI: 10.1007/s00592-018-1129-8] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 03/07/2018] [Indexed: 12/19/2022]
Abstract
AIMS Diabetes is associated with an excess release of neutrophil extracellular traps (NETs) and an enhanced NETosis, a neutrophil cell death programme instrumental to anti-microbial defences, but also involved in tissue damage. We herein investigated whether the antidiabetic drug metformin protects against NETosis. METHODS We measured NET components in the plasma of patients with pre-diabetes who were randomized to receive metformin or placebo for 2 months. To control for the effect on glucose, we also measured NET components in the plasma of patients with type 2 diabetes before and after treatment with insulin or dapagliflozin. In vitro, we used static and dynamic imaging with advanced live confocal two-photon microscopy to evaluate the effects of metformin on cellular events during NETosis. We examined putative molecular mechanisms by monitoring chromatin decondensation and DNA release in vitro. RESULTS Metformin, as compared to placebo, significantly reduced the concentrations of NET components elastase, proteinase-3, histones and double strand DNA, whereas glucose control with insulin or dapagliflozin exerted no significant effect. In vitro, metformin prevented pathologic changes in nuclear dynamics and DNA release, resulting in a blunted NETosis in response to phorbol myristate acetate and calcium influx. Metformin prevented membrane translocation of PKC-βII and activation of NADPH oxidase in neutrophils, both of which diminished the NETosis response. CONCLUSIONS Metformin treatment reduced the concentrations of NET components independently from glucose control. This effect was reproducible in vitro and was related to the inhibitory effect exerted by metformin on the PKC-NADPH oxidase pathway.
Collapse
Affiliation(s)
- Lisa Menegazzo
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128, Padua, Italy
- Venetian Institute of Molecular Medicine, 35129, Padua, Italy
| | - Valentina Scattolini
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128, Padua, Italy
- Venetian Institute of Molecular Medicine, 35129, Padua, Italy
| | - Roberta Cappellari
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128, Padua, Italy
- Venetian Institute of Molecular Medicine, 35129, Padua, Italy
| | - Benedetta Maria Bonora
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128, Padua, Italy
- Venetian Institute of Molecular Medicine, 35129, Padua, Italy
| | - Mattia Albiero
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128, Padua, Italy
- Venetian Institute of Molecular Medicine, 35129, Padua, Italy
| | - Mario Bortolozzi
- Venetian Institute of Molecular Medicine, 35129, Padua, Italy
- Department of Physics and Astronomy, University of Padova, 35131, Padua, Italy
| | - Filippo Romanato
- Department of Physics and Astronomy, University of Padova, 35131, Padua, Italy
- IOM-CNR, ss.14 km 163.5, 34149, Basovizza, Trieste, Italy
| | - Giulio Ceolotto
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128, Padua, Italy
| | | | - Angelo Avogaro
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128, Padua, Italy
| | - Gian Paolo Fadini
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128, Padua, Italy.
- Venetian Institute of Molecular Medicine, 35129, Padua, Italy.
| |
Collapse
|
12
|
Carrer A, Leparulo A, Crispino G, Ciubotaru CD, Marin O, Zonta F, Bortolozzi M. Cx32 hemichannel opening by cytosolic Ca2+ is inhibited by the R220X mutation that causes Charcot-Marie-Tooth disease. Hum Mol Genet 2018; 27:80-94. [PMID: 29077882 DOI: 10.1093/hmg/ddx386] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 10/17/2017] [Indexed: 11/15/2022] Open
Abstract
Mutations of the GJB1 gene encoding connexin 32 (Cx32) cause the X-linked form of Charcot-Marie-Tooth disease (CMTX1), a demyelinating peripheral neuropathy for which there is no cure. A growing body of evidence indicates that ATP release through Cx32 hemichannels in Schwann cells could be critical for nerve myelination, but it is unknown if CMTX1 mutations alter the cytosolic Ca2+-dependent gating mechanism that controls Cx32 hemichannel opening and ATP release. The current study uncovered that loss of the C-terminus in Cx32 (R220X mutation), which causes a severe CMTX1 phenotype, inhibits hemichannel opening during a canonical IP3-mediated increase in cytosolic Ca2+ in HeLa cells. Interestingly, the gating function of R220X hemichannels was completely restored by both the intracellular and extracellular application of a peptide that mimics the Cx32 cytoplasmic loop. All-atom molecular dynamics simulations suggest that loss of the C-terminus in the mutant hemichannel triggers abnormal fluctuations of the cytoplasmic loop which are prevented by binding to the mimetic peptide. Experiments that stimulated R220X hemichannel opening by cell depolarization displayed reduced voltage sensitivity with respect to wild-type hemichannels which was explained by loss of subconductance states at the single channel level. Finally, experiments of intercellular diffusion mediated by wild-type or R220X gap junction channels revealed similar unitary permeabilities to ions, signalling molecules (cAMP) or larger solutes (Lucifer yellow). Taken together, our findings support the hypothesis that paracrine signalling alteration due to Cx32 hemichannel dysfunction underlies CMTX1 pathogenesis and suggest a candidate molecule for novel studies investigating a therapeutic approach.
Collapse
Affiliation(s)
- Andrea Carrer
- Venetian Institute of Molecular Medicine (VIMM), Padua 35129, Italy
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padua 35131, Italy
| | - Alessandro Leparulo
- Venetian Institute of Molecular Medicine (VIMM), Padua 35129, Italy
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padua 35131, Italy
| | - Giulia Crispino
- Venetian Institute of Molecular Medicine (VIMM), Padua 35129, Italy
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padua 35131, Italy
| | | | - Oriano Marin
- Department of Biomedical Sciences, University of Padua, Padua 35131, Italy
| | - Francesco Zonta
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai 201210, China
- Italian National Research Council (CNR), Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy
| | - Mario Bortolozzi
- Venetian Institute of Molecular Medicine (VIMM), Padua 35129, Italy
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padua 35131, Italy
- Italian National Research Council (CNR), Institute of Protein Biochemistry, Naples 80131, Italy
| |
Collapse
|
13
|
Mammano F, Bortolozzi M. Ca 2+ signaling, apoptosis and autophagy in the developing cochlea: Milestones to hearing acquisition. Cell Calcium 2017; 70:117-126. [PMID: 28578918 DOI: 10.1016/j.ceca.2017.05.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [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: 03/23/2017] [Revised: 05/09/2017] [Accepted: 05/09/2017] [Indexed: 12/16/2022]
Abstract
In mammals, the sense of hearing arises through a complex sequence of morphogenetic events that drive the sculpting of the auditory sensory epithelium into its terminally functional three-dimensional shape. While the majority of the underlying mechanisms remain unknown, it has become increasingly clear that Ca2+ signaling is at center stage and plays numerous fundamental roles both in the sensory hair cells and in the matrix of non-sensory, epithelial and supporting cells, which embed them and are tightly interconnected by a dense network of gap junctions formed by connexin 26 (Cx26) and connexin 30 (Cx30) protein subunits. In this review, we discuss the intricate interplay between Ca2+ signaling, connexin expression and function, apoptosis and autophagy in the crucial steps that lead to hearing acquisition.
Collapse
Affiliation(s)
- Fabio Mammano
- Department of Physics and Astronomy "G. Galilei", University of Padua, 35131 Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Foundation for Advanced Biomedical Research, 35129 Padua, Italy; Department of Biomedical Sciences, Institute of Cell Biology and Neurobiology, Italian National Research Council, 00015 Monterotondo, (RM), Italy.
| | - Mario Bortolozzi
- Department of Physics and Astronomy "G. Galilei", University of Padua, 35131 Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Foundation for Advanced Biomedical Research, 35129 Padua, Italy; Department of Biomedical Sciences, Institute of Protein Biochemistry, Italian National Research Council, 80131 Naples (NA), Italy
| |
Collapse
|
14
|
Monterisi S, Lobo MJ, Livie C, Castle JC, Weinberger M, Baillie G, Surdo NC, Musheshe N, Stangherlin A, Gottlieb E, Maizels R, Bortolozzi M, Micaroni M, Zaccolo M. PDE2A2 regulates mitochondria morphology and apoptotic cell death via local modulation of cAMP/PKA signalling. eLife 2017; 6:e21374. [PMID: 28463107 PMCID: PMC5423767 DOI: 10.7554/elife.21374] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 04/29/2017] [Indexed: 01/31/2023] Open
Abstract
cAMP/PKA signalling is compartmentalised with tight spatial and temporal control of signal propagation underpinning specificity of response. The cAMP-degrading enzymes, phosphodiesterases (PDEs), localise to specific subcellular domains within which they control local cAMP levels and are key regulators of signal compartmentalisation. Several components of the cAMP/PKA cascade are located to different mitochondrial sub-compartments, suggesting the presence of multiple cAMP/PKA signalling domains within the organelle. The function and regulation of these domains remain largely unknown. Here, we describe a novel cAMP/PKA signalling domain localised at mitochondrial membranes and regulated by PDE2A2. Using pharmacological and genetic approaches combined with real-time FRET imaging and high resolution microscopy, we demonstrate that in rat cardiac myocytes and other cell types mitochondrial PDE2A2 regulates local cAMP levels and PKA-dependent phosphorylation of Drp1. We further demonstrate that inhibition of PDE2A, by enhancing the hormone-dependent cAMP response locally, affects mitochondria dynamics and protects from apoptotic cell death.
Collapse
Affiliation(s)
- Stefania Monterisi
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Miguel J Lobo
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Craig Livie
- Institute of Neuroscioence and Psychology, University of Glasgow, Glasgow, United Kingdom
| | - John C Castle
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Michael Weinberger
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - George Baillie
- Institute of Cardiovascular and Medical Science, University of Glasgow, Glasgow, United Kingdom
| | - Nicoletta C Surdo
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Nshunge Musheshe
- Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands
| | - Alessandra Stangherlin
- Institute of Neuroscioence and Psychology, University of Glasgow, Glasgow, United Kingdom
| | - Eyal Gottlieb
- Beatson Institute, University of Glasgow, Glasgow, United Kingdom
| | - Rory Maizels
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Mario Bortolozzi
- Department of Physics and Astronomy “G. Galilei”, University of Padova, Padova, Italy
- Venetian Institute of Molecular Medicine, University of Padova, Padova, Italy
| | - Massimo Micaroni
- Swedish National Centre for Cellular Imaging, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Manuela Zaccolo
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
15
|
Calì B, Ceolin S, Ceriani F, Bortolozzi M, Agnellini AHR, Zorzi V, Predonzani A, Bronte V, Molon B, Mammano F. Critical role of gap junction communication, calcium and nitric oxide signaling in bystander responses to focal photodynamic injury. Oncotarget 2016; 6:10161-74. [PMID: 25868859 PMCID: PMC4496347 DOI: 10.18632/oncotarget.3553] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [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: 01/24/2015] [Accepted: 02/14/2015] [Indexed: 12/02/2022] Open
Abstract
Ionizing and nonionizing radiation affect not only directly targeted cells but also surrounding “bystander” cells. The underlying mechanisms and therapeutic role of bystander responses remain incompletely defined. Here we show that photosentizer activation in a single cell triggers apoptosis in bystander cancer cells, which are electrically coupled by gap junction channels and support the propagation of a Ca2+ wave initiated in the irradiated cell. The latter also acts as source of nitric oxide (NO) that diffuses to bystander cells, in which NO levels are further increased by a mechanism compatible with Ca2+-dependent enzymatic production. We detected similar signals in tumors grown in dorsal skinfold chambers applied to live mice. Pharmacological blockade of connexin channels significantly reduced the extent of apoptosis in bystander cells, consistent with a critical role played by intercellular communication, Ca2+ and NO in the bystander effects triggered by photodynamic therapy.
Collapse
Affiliation(s)
- Bianca Calì
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine, Padua, Italy.,University of Padua, Department of Surgery Oncology and Gastroenterology, Oncology and Immunology Section, Padua, Italy
| | - Stefano Ceolin
- University of Padua, Department of Physics and Astronomy, Padua, Italy
| | - Federico Ceriani
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine, Padua, Italy.,University of Padua, Department of Physics and Astronomy, Padua, Italy
| | - Mario Bortolozzi
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine, Padua, Italy.,University of Padua, Department of Physics and Astronomy, Padua, Italy
| | - Andrielly H R Agnellini
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine, Padua, Italy.,University of Padua, Department of Surgery Oncology and Gastroenterology, Oncology and Immunology Section, Padua, Italy
| | - Veronica Zorzi
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine, Padua, Italy.,University of Padua, Department of Physics and Astronomy, Padua, Italy
| | | | - Vincenzo Bronte
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine, Padua, Italy.,Verona University Hospital, Department of Pathology and Diagnostics, Immunology Section, Verona, Italy
| | | | - Fabio Mammano
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine, Padua, Italy.,University of Padua, Department of Physics and Astronomy, Padua, Italy.,Present address: CNR, Institute of Cell Biology and Neurobiology, Monterotondo (RM), Italy
| |
Collapse
|
16
|
Abstract
Confocal imaging of fluorescent probes offers a powerful, non-invasive tool which enables data collection from vast population of cells at high spatial and temporal resolution. Spinning disk confocal microscopy parallelizes the imaging process permitting the study of dynamic events in populations of living cells on the millisecond time scale. Several spinning disk microscopy solutions are commercially available, however these are often poorly configurable and relatively expensive. This chapter describes a procedure to assemble a cost-effective homemade spinning disk system for fluorescence microscopy, which is highly flexible and easily configurable. We finally illustrate a reliable protocol to obtain high-quality Ca(2+) and voltage imaging data from cochlear preparations.
Collapse
Affiliation(s)
- Federico Ceriani
- Department of Physics and Astronomy, University of Padua, via Marzolo 8, Padua, 35131, Italy
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine (VIMM), via G. Orus 2, Padua, 35129, Italy
- CNR, Institute of Cell Biology and Neurobiology, via E. Ramarini 32, Monterotondo, RM, 00015, Italy
| | | | - Mario Bortolozzi
- Department of Physics and Astronomy, University of Padua, via Marzolo 8, Padua, 35131, Italy.
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine (VIMM), via G. Orus 2, Padua, 35129, Italy.
- CNR, Institute of Cell Biology and Neurobiology, via E. Ramarini 32, Monterotondo, RM, 00015, Italy.
| | - Fabio Mammano
- Department of Physics and Astronomy, University of Padua, via Marzolo 8, Padua, 35131, Italy
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine (VIMM), via G. Orus 2, Padua, 35129, Italy
- CNR, Institute of Cell Biology and Neurobiology, via E. Ramarini 32, Monterotondo, RM, 00015, Italy
| |
Collapse
|
17
|
Bortolozzi M, Mammano F. PMCA2w/a Splice Variant: A Key Regulator of Hair Cell Mechano-transduction Machinery. Regulation of Ca2+-ATPases,V-ATPases and F-ATPases 2016:27-45. [DOI: 10.1007/978-3-319-24780-9_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
|
18
|
Zonta F, Buratto D, Cassini C, Bortolozzi M, Mammano F. Molecular dynamics simulations highlight structural and functional alterations in deafness-related M34T mutation of connexin 26. Front Physiol 2014; 5:85. [PMID: 24624091 PMCID: PMC3941013 DOI: 10.3389/fphys.2014.00085] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 02/12/2014] [Indexed: 11/22/2022] Open
Abstract
Mutations of the GJB2 gene encoding the connexin 26 (Cx26) gap junction protein, which is widely expressed in the inner ear, are the primary cause of hereditary non-syndromic hearing loss in several populations. The deafness–associated single amino acid substitution of methionine 34 (M34) in the first transmembrane helix (TM1) with a threonine (T) ensues in the production of mutant Cx26M34T channels that are correctly synthesized and assembled in the plasma membrane. However, mutant channels overexpressed in HeLa cells retain only 11% of the wild type unitary conductance. Here we extend and rationalize those findings by comparing wild type Cx26 (Cx26WT) and Cx26M34T mutant channels in silico, using molecular dynamics simulations. Our results indicate that the quaternary structure of the Cx26M34T hemichannel is altered at the level of the pore funnel due to the disruption of the hydrophobic interaction between M34 and tryptophan 3 (W3) in the N–terminal helix (NTH). Our simulations also show that external force stimuli applied to the NTHs can detach them from the inner wall of the pore more readily in the mutant than in the wild type hemichannel. These structural alterations significantly increase the free energy barrier encountered by permeating ions, correspondingly decreasing the unitary conductance of the Cx26M34T hemichannel. Our results accord with the proposal that the mutant resides most of the time in a low conductance state. However, the small displacement of the NTHs in our Cx26M34T hemichannel model is not compatible with the formation of a pore plug as in the related Cx26M34A mutant.
Collapse
Affiliation(s)
- Francesco Zonta
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy
| | - Damiano Buratto
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy
| | - Chiara Cassini
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy
| | - Mario Bortolozzi
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy ; Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata Padova, Italy
| | - Fabio Mammano
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy ; Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata Padova, Italy ; Istituto di Neuroscienze, Consiglio Nazionale delle Ricerche Padova, Italy
| |
Collapse
|
19
|
Wong AKC, Capitanio P, Lissandron V, Bortolozzi M, Pozzan T, Pizzo P. Heterogeneity of Ca2+ handling among and within Golgi compartments. J Mol Cell Biol 2014; 5:266-76. [PMID: 23918284 DOI: 10.1093/jmcb/mjt024] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [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: 12/25/2022] Open
Abstract
The Golgi apparatus (GA) is a dynamic intracellular Ca(2+) store endowed with complex Ca(2+) homeostatic mechanisms in part distinct from those of the endoplasmic reticulum (ER). We describe the generation of a novel fluorescent Ca(2+) probe selectively targeted to the medial-Golgi. We demonstrate that in the medial-Golgi: (i) Ca(2+) accumulation takes advantage of two distinct pumps, the sarco/endoplasmic reticulum Ca(2+) ATPase and the secretory pathway Ca(2+) ATPase1; (ii) activation of IP3 or ryanodine receptors causes Ca(2+) release, while no functional two-pore channel was found; (iii) luminal Ca(2+) concentration appears higher than that of the trans-Golgi, but lower than that of the ER, suggesting the existence of a cis- to trans-Golgi Ca(2+) concentration gradient. Thus, the GA represents a Ca(2+) store of high complexity where, despite the continuous flow of membranes and luminal contents, each sub-compartment maintains its Ca(2+) identity with specific Ca(2+) homeostatic characteristics. The functional role of such micro-heterogeneity in GA Ca(2+) handling is discussed.
Collapse
Affiliation(s)
- Andrea K C Wong
- Department of Biomedical Sciences, University of Padua, 35121 Padua, Italy
| | | | | | | | | | | |
Collapse
|
20
|
Zonta F, Polles G, Sanasi MF, Bortolozzi M, Mammano F. The 3.5 ångström X-ray structure of the human connexin26 gap junction channel is unlikely that of a fully open channel. Cell Commun Signal 2013; 11:15. [PMID: 23445664 PMCID: PMC3599431 DOI: 10.1186/1478-811x-11-15] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [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: 11/20/2012] [Accepted: 02/12/2013] [Indexed: 01/30/2023] Open
Abstract
The permeability of gap junction channels to metabolites, and not simply to small inorganic ions, is likely to play an important role in development, physiology as well as in etiology of several diseases. Here, we combined dual patch clamp and fluorescence imaging techniques with molecular dynamics (MD) simulations to investigate the permeation of calcein, a relatively large fluorescent tracer (MW 622 Da) through homomeric gap junction channels formed by wild type human connexin26 (hCx26wt) protomers. Our experimental data indicate that the unitary flux of calcein driven by a 125 μM concentration difference is Jpore = 226 molecule/s per channel. In the light of Eyring transition state theory adapted for the liquid phase, this value corresponds to an energy barrier of ~20 kBT (where kB is the Boltzmann constant and T is absolute temperature). The barrier predicted by our MD simulations, based on the 3.5 Å X–ray structural model of the hCx26wt gap junction channel, is ~45 kBT. The main contributions to the energetics of calcein permeation originated from the interaction between the permeating molecule and the charged aminoacids lining the channel pore. Assigning a fake zero total charge to the calcein molecule yielded a value for the barrier height compatible with the experimental data. These results can be accounted for by two different (although not mutually exclusive) hypotheses: (1) the X–ray model of the hCx26wt gap junction channel is not representative of a fully open state; (2) post translational modifications affecting the hCx26wt protein in our expression system differed from the modifications undergone by the proteins in the conditions used to obtain the crystal structure. Hypothesis (1) is compatible with data indicating that, only 10% or less of the channels forming a gap junction plaque are in the open state, and therefore the averaging procedure intrinsic in the generation of the crystal structure data more closely reflects that of a closed channel. Hypothesis (2) is compatible with recent mass spectrometry data and implies that the charge of several amino acid side chains may have been altered, thus modifying substantially the permeation properties of the channels in living cells.
Collapse
Affiliation(s)
- Francesco Zonta
- Department of Physics and Astronomy "G, Galilei", University of Padua, 35131, Padua, Italy.
| | | | | | | | | |
Collapse
|
21
|
Ford KL, Moorhouse EL, Bortolozzi M, Vaughan-Jones RD. Global and Local Effects of Intracellular pH on Ca2+ Waves in Rat Ventricular Myocytes. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.3348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
|
22
|
Crispino G, Di Pasquale G, Scimemi P, Rodriguez L, Galindo Ramirez F, De Siati RD, Santarelli RM, Arslan E, Bortolozzi M, Chiorini JA, Mammano F. BAAV mediated GJB2 gene transfer restores gap junction coupling in cochlear organotypic cultures from deaf Cx26Sox10Cre mice. PLoS One 2011; 6:e23279. [PMID: 21876744 PMCID: PMC3158073 DOI: 10.1371/journal.pone.0023279] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 07/11/2011] [Indexed: 11/24/2022] Open
Abstract
The deafness locus DFNB1 contains GJB2, the gene encoding connexin26 and GJB6, encoding connexin30, which appear to be coordinately regulated in the inner ear. In this work, we investigated the expression and function of connexin26 and connexin30 from postnatal day 5 to adult age in double transgenic Cx26(Sox10Cre) mice, which we obtained by crossing connexin26 floxed mice with a deleter Sox10-Cre line. Cx26(Sox10Cre) mice presented with complete connexin26 ablation in the epithelial gap junction network of the cochlea, whereas connexin30 expression was developmentally delayed; immunolabeling patterns for both connexins were normal in the cochlear lateral wall. In vivo electrophysiological measurements in Cx26(Sox10Cre) mice revealed profound hearing loss accompanied by reduction of endocochlear potential, and functional experiments performed in postnatal cochlear organotypic cultures showed impaired gap junction coupling. Transduction of these cultures with a bovine adeno associated virus vector restored connexin26 protein expression and rescued gap junction coupling. These results suggest that restoration of normal connexin levels by gene delivery via recombinant adeno associated virus could be a way to rescue hearing function in DFNB1 mouse models and, in future, lead to the development of therapeutic interventions in humans.
Collapse
Affiliation(s)
- Giulia Crispino
- Fondazione per la Ricerca Biomedica Avanzata, Istituto Veneto di Medicina Molecolare, Padova, Italy
- Dipartimento di Fisica “G. Galilei”, Università di Padova, Padova, Italy
| | - Giovanni Di Pasquale
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Pietro Scimemi
- Dipartimento di Specialità Medico–Chirurgiche e Servizio di Audiologia, Università di Padova, Padova, Italy
| | - Laura Rodriguez
- Fondazione per la Ricerca Biomedica Avanzata, Istituto Veneto di Medicina Molecolare, Padova, Italy
- Dipartimento di Fisica “G. Galilei”, Università di Padova, Padova, Italy
| | - Fabian Galindo Ramirez
- Fondazione per la Ricerca Biomedica Avanzata, Istituto Veneto di Medicina Molecolare, Padova, Italy
| | - Romolo Daniele De Siati
- Dipartimento di Specialità Medico–Chirurgiche e Servizio di Audiologia, Università di Padova, Padova, Italy
| | - Rosa Maria Santarelli
- Dipartimento di Specialità Medico–Chirurgiche e Servizio di Audiologia, Università di Padova, Padova, Italy
| | - Edoardo Arslan
- Dipartimento di Specialità Medico–Chirurgiche e Servizio di Audiologia, Università di Padova, Padova, Italy
| | - Mario Bortolozzi
- Fondazione per la Ricerca Biomedica Avanzata, Istituto Veneto di Medicina Molecolare, Padova, Italy
- Dipartimento di Fisica “G. Galilei”, Università di Padova, Padova, Italy
- Istituto CNR di Neuroscienze, Padova, Italy
| | - John A. Chiorini
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Fabio Mammano
- Fondazione per la Ricerca Biomedica Avanzata, Istituto Veneto di Medicina Molecolare, Padova, Italy
- Dipartimento di Fisica “G. Galilei”, Università di Padova, Padova, Italy
- Istituto CNR di Neuroscienze, Padova, Italy
| |
Collapse
|
23
|
Zampese E, Fasolato C, Kipanyula MJ, Bortolozzi M, Pozzan T, Pizzo P. Presenilin 2 modulates endoplasmic reticulum (ER)-mitochondria interactions and Ca2+ cross-talk. Proc Natl Acad Sci U S A 2011; 108:2777-82. [PMID: 21285369 PMCID: PMC3041131 DOI: 10.1073/pnas.1100735108] [Citation(s) in RCA: 215] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Presenilin mutations are the main cause of familial Alzheimer's disease (FAD). Presenilins also play a key role in Ca(2+) homeostasis, and their FAD-linked mutants affect cellular Ca(2+) handling in several ways. We previously have demonstrated that FAD-linked presenilin 2 (PS2) mutants decrease the Ca(2+) content of the endoplasmic reticulum (ER) by inhibiting sarcoendoplasmic reticulum Ca(2+)-ATPase (SERCA) activity and increasing ER Ca(2+) leak. Here we focus on the effect of presenilins on mitochondrial Ca(2+) dynamics. By using genetically encoded Ca(2+) indicators specifically targeted to mitochondria (aequorin- and GFP-based probes) in SH-SY5Y cells and primary neuronal cultures, we show that overexpression or down-regulation of PS2, but not of presenilin 1 (PS1), modulates the Ca(2+) shuttling between ER and mitochondria, with its FAD mutants strongly favoring Ca(2+) transfer between the two organelles. This effect is not caused by a direct PS2 action on mitochondrial Ca(2+)-uptake machinery but rather by an increased physical interaction between ER and mitochondria that augments the frequency of Ca(2+) hot spots generated at the cytoplasmic surface of the outer mitochondrial membrane upon stimulation. This PS2 function adds further complexity to the multifaceted nature of presenilins and to their physiological role within the cell. We also discuss the importance of this additional effect of FAD-linked PS2 mutants for the understanding of FAD pathogenesis.
Collapse
Affiliation(s)
| | | | | | - Mario Bortolozzi
- Physics, University of Padua, 35121 Padua, Italy
- Venetian Institute of Molecular Medicine, 35129 Padua, Italy; and
| | - Tullio Pozzan
- Departments of Biomedical Sciences and
- Venetian Institute of Molecular Medicine, 35129 Padua, Italy; and
- Consiglio Nazionale delle Ricerche Institute of Neuroscience, 35121 Padua, Italy
| | | |
Collapse
|
24
|
Bortolozzi M. Defects in the Atp2b2 Gene Causing Hereditary Hearing and Balance Loss in Mice and Humans: A Biophysical Study of Normal and Mutated PMCA2 Pump Function. Biophotonics: Spectroscopy, Imaging, Sensing, and Manipulation 2011:371-371. [DOI: 10.1007/978-90-481-9977-8_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
|
25
|
Schütz M, Scimemi P, Majumder P, De Siati RD, Crispino G, Rodriguez L, Bortolozzi M, Santarelli R, Seydel A, Sonntag S, Ingham N, Steel KP, Willecke K, Mammano F. The human deafness-associated connexin 30 T5M mutation causes mild hearing loss and reduces biochemical coupling among cochlear non-sensory cells in knock-in mice. Hum Mol Genet 2010; 19:4759-73. [PMID: 20858605 PMCID: PMC2989887 DOI: 10.1093/hmg/ddq402] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 08/18/2010] [Accepted: 09/14/2010] [Indexed: 12/11/2022] Open
Abstract
Mutations in the GJB2 and GJB6 genes, respectively, coding for connexin26 (Cx26) and connexin30 (Cx30) proteins, are the most common cause for prelingual non-syndromic deafness in humans. In the inner ear, Cx26 and Cx30 are expressed in different non-sensory cell types, where they largely co-localize and may form heteromeric gap junction channels. Here, we describe the generation and characterization of a mouse model for human bilateral middle/high-frequency hearing loss based on the substitution of an evolutionarily conserved threonine by a methionine residue at position 5 near the N-terminus of Cx30 (Cx30T5M). The mutation was inserted in the mouse genome by homologous recombination in mouse embryonic stem cells. Expression of the mutated Cx30T5M protein in these transgenic mice is under the control of the endogenous Cx30 promoter and was analysed via activation of the lacZ reporter gene. When probed by auditory brainstem recordings, Cx30(T5M/T5M) mice exhibited a mild, but significant increase in their hearing thresholds of about 15 dB at all frequencies. Immunolabelling with antibodies to Cx26 or Cx30 suggested normal location of these proteins in the adult inner ear, but western blot analysis showed significantly down-regulated the expression levels of Cx26 and Cx30. In the developing cochlea, electrical coupling, probed by dual patch-clamp recordings, was normal. However, transfer of the fluorescent tracer calcein between cochlear non-sensory cells was reduced, as was intercellular Ca(2+) signalling due to spontaneous ATP release from connexin hemichannels. Our findings link hearing loss to decreased biochemical coupling due to the point-mutated Cx30 in mice.
Collapse
Affiliation(s)
- Melanie Schütz
- Institut fuer Genetik, Rheinische Friedrich-Wilhelms-Universitaet Bonn, Roemerstrasse 164, D-53117 Bonn, Germany
| | - Pietro Scimemi
- Dipartimento di Specialità Medico Chirurgiche, Università di Padova, via Giustiniani 2, 35129 Padova, Italy
- Servizio di Audiologia, Ospedale ‘Ca’ Foncello’, Treviso, Italy
| | - Paromita Majumder
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Romolo Daniele De Siati
- Dipartimento di Specialità Medico Chirurgiche, Università di Padova, via Giustiniani 2, 35129 Padova, Italy
- Servizio di Audiologia, Ospedale ‘Ca’ Foncello’, Treviso, Italy
| | - Giulia Crispino
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Laura Rodriguez
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Mario Bortolozzi
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
- Dipartimento di Fisica ‘G. Galilei’, Università di Padova, 35131 Padova, Italy
- Istituto CNR di Neuroscienze, Padova, Italy and
| | - Rosamaria Santarelli
- Dipartimento di Specialità Medico Chirurgiche, Università di Padova, via Giustiniani 2, 35129 Padova, Italy
- Servizio di Audiologia, Ospedale ‘Ca’ Foncello’, Treviso, Italy
| | - Anke Seydel
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Stephan Sonntag
- Institut fuer Genetik, Rheinische Friedrich-Wilhelms-Universitaet Bonn, Roemerstrasse 164, D-53117 Bonn, Germany
| | - Neil Ingham
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Karen P. Steel
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Klaus Willecke
- Institut fuer Genetik, Rheinische Friedrich-Wilhelms-Universitaet Bonn, Roemerstrasse 164, D-53117 Bonn, Germany
| | - Fabio Mammano
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
- Dipartimento di Fisica ‘G. Galilei’, Università di Padova, 35131 Padova, Italy
- Istituto CNR di Neuroscienze, Padova, Italy and
| |
Collapse
|
26
|
Bortolozzi M, Brini M, Parkinson N, Crispino G, Scimemi P, De Siati RD, Di Leva F, Parker A, Ortolano S, Arslan E, Brown SD, Carafoli E, Mammano F. The novel PMCA2 pump mutation Tommy impairs cytosolic calcium clearance in hair cells and links to deafness in mice. J Biol Chem 2010; 285:37693-703. [PMID: 20826782 PMCID: PMC2988374 DOI: 10.1074/jbc.m110.170092] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [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: 11/17/2022] Open
Abstract
The mechanotransduction process in hair cells in the inner ear is associated with the influx of calcium from the endolymph. Calcium is exported back to the endolymph via the splice variant w/a of the PMCA2 of the stereocilia membrane. To further investigate the role of the pump, we have identified and characterized a novel ENU-induced mouse mutation, Tommy, in the PMCA2 gene. The mutation causes a non-conservative E629K change in the second intracellular loop of the pump that harbors the active site. Tommy mice show profound hearing impairment from P18, with significant differences in hearing thresholds between wild type and heterozygotes. Expression of mutant PMCA2 in CHO cells shows calcium extrusion impairment; specifically, the long term, non-stimulated calcium extrusion activity of the pump is inhibited. Calcium extrusion was investigated directly in neonatal organotypic cultures of the utricle sensory epithelium in Tommy mice. Confocal imaging combined with flash photolysis of caged calcium showed impairment of calcium export in both Tommy heterozygotes and homozygotes. Immunofluorescence studies of the organ of Corti in homozygous Tommy mice showed a progressive base to apex degeneration of hair cells after P40. Our results on the Tommy mutation along with previously observed interactions between cadherin-23 and PMCA2 mutations in mouse and humans underline the importance of maintaining the appropriate calcium concentrations in the endolymph to control the rigidity of cadherin and ensure the function of interstereocilia links, including tip links, of the stereocilia bundle.
Collapse
Affiliation(s)
- Mario Bortolozzi
- Department of Physics G Galilei, University of Padua, Padua 35131, Italy
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Majumder P, Crispino G, Rodriguez L, Ciubotaru CD, Anselmi F, Piazza V, Bortolozzi M, Mammano F. ATP-mediated cell-cell signaling in the organ of Corti: the role of connexin channels. Purinergic Signal 2010; 6:167-87. [PMID: 20806010 PMCID: PMC2912995 DOI: 10.1007/s11302-010-9192-9] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 05/31/2010] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Connexin 26 (Cx26) and connexin 30 (Cx30) form hemichannels that release ATP from the endolymphatic surface of cochlear supporting and epithelial cells and also form gap junction (GJ) channels that allow the concomitant intercellular diffusion of Ca(2+) mobilizing second messengers. Released ATP in turn activates G-protein coupled P2Y(2) and P2Y(4) receptors, PLC-dependent generation of IP(3), release of Ca(2+) from intracellular stores, instigating the regenerative propagation of intercellular Ca(2+) signals (ICS). The range of ICS propagation is sensitive to the concentration of extracellular divalent cations and activity of ectonucleotidases. Here, the expression patterns of Cx26 and Cx30 were characterized in postnatal cochlear tissues obtained from mice aged between P5 and P6. The expression gradient along the longitudinal axis of the cochlea, decreasing from the basal to the apical cochlear turn (CT), was more pronounced in outer sulcus (OS) cells than in inner sulcus (IS) cells. GJ-mediated dye coupling was maximal in OS cells of the basal CT, inhibited by the nonselective connexin channel blocker carbenoxolone (CBX) and absent in hair cells. Photostimulating OS cells with caged inositol (3,4,5) tri-phosphate (IP(3)) resulted in transfer of ICS in the lateral direction, from OS cells to IS cells across the hair cell region (HCR) of medial and basal CTs. ICS transfer in the opposite (medial) direction, from IS cells photostimulated with caged IP(3) to OS cells, occurred mostly in the basal CT. In addition, OS cells displayed impressive rhythmic activity with oscillations of cytosolic free Ca(2+) concentration ([Ca(2+)](i)) coordinated by the propagation of Ca(2+) wavefronts sweeping repeatedly through the same tissue area along the coiling axis of the cochlea. Oscillations evoked by uncaging IP(3) or by applying ATP differed greatly, by as much as one order of magnitude, in frequency and waveform rise time. ICS evoked by direct application of ATP propagated along convoluted cellular paths in the OS, which often branched and changed dynamically over time. Potential implications of these findings are discussed in the context of developmental regulation and cochlear pathophysiology. ELECTRONIC SUPPLEMENTARY MATERIAL The online version of this article (doi:10.1007/s11302-010-9192-9) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Paromita Majumder
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Giulia Crispino
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Laura Rodriguez
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Catalin Dacian Ciubotaru
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Fabio Anselmi
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Valeria Piazza
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Mario Bortolozzi
- Dipartimento di Fisica “G. Galilei”, Università di Padova, via Marzolo 8, 35129 Padova, Italy
- Istituto di Neuroscienze, CNR, Padova, Italy
| | - Fabio Mammano
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
- Dipartimento di Fisica “G. Galilei”, Università di Padova, via Marzolo 8, 35129 Padova, Italy
- Istituto di Neuroscienze, CNR, Padova, Italy
- Centro Interdipartimentale per lo Studio dei Segnali Cellulari, Università di Padova, via G. Orus 2, 35129 Padova, Italy
- VIMM, Via G. Orus 2, 35129 Padova, Italy
| |
Collapse
|
28
|
Giacomello M, Drago I, Bortolozzi M, Scorzeto M, Gianelle A, Pizzo P, Pozzan T. Ca2+ hot spots on the mitochondrial surface are generated by Ca2+ mobilization from stores, but not by activation of store-operated Ca2+ channels. Mol Cell 2010; 38:280-90. [PMID: 20417605 DOI: 10.1016/j.molcel.2010.04.003] [Citation(s) in RCA: 310] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 12/21/2009] [Accepted: 02/03/2010] [Indexed: 12/19/2022]
Abstract
Although it is widely accepted that mitochondria in living cells can efficiently uptake Ca(2+) during stimulation because of their vicinity to microdomains of high [Ca(2+)], the direct proof of Ca(2+) hot spots' existence is still lacking. Thanks to a GFP-based Ca(2+) probe localized on the cytosolic surface of the outer mitochondrial membrane, we demonstrate that, upon Ca(2+) mobilization, the [Ca(2+)] in small regions of the mitochondrial surface reaches levels 5- to 10-fold higher than in the bulk cytosol. We also show that the [Ca(2+)] to which mitochondria are exposed during capacitative Ca(2+) influx is similar between near plasma membrane mitochondria and organelles deeply located in the cytoplasm, whereas it is 2- to 3-fold higher in subplasma membrane mitochondria upon activation of voltage-gated Ca(2+) channels. These results demonstrate that mitochondria are exposed to Ca(2+) hot spots close to the ER but are excluded from the regions where capacitative Ca(2+) influx occurs.
Collapse
Affiliation(s)
- Marta Giacomello
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | | | | | | | | | | | | |
Collapse
|
29
|
Spinazzi M, Cazzola S, Bortolozzi M, Baracca A, Loro E, Casarin A, Solaini G, Sgarbi G, Casalena G, Cenacchi G, Malena A, Frezza C, Carrara F, Angelini C, Scorrano L, Salviati L, Vergani L. A novel deletion in the GTPase domain of OPA1 causes defects in mitochondrial morphology and distribution, but not in function. Hum Mol Genet 2008; 17:3291-302. [PMID: 18678599 DOI: 10.1093/hmg/ddn225] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Autosomal dominant optic atrophy (ADOA), the commonest cause of inherited optic atrophy, is caused by mutations in the ubiquitously expressed gene optic atrophy 1 (OPA1), involved in fusion and biogenesis of the inner membrane of mitochondria. Bioenergetic failure, mitochondrial network abnormalities and increased apoptosis have all been proposed as possible causal factors. However, their relative contribution to pathogenesis as well as the prominent susceptibility of the retinal ganglion cell (RGC) in this disease remains uncertain. Here we identify a novel deletion of OPA1 gene in the GTPase domain in three patients affected by ADOA. Muscle biopsy of the patients showed neurogenic atrophy and abnormal morphology and distribution of mitochondria. Confocal microscopy revealed increased mitochondrial fragmentation in fibroblasts as well as in myotubes, where mitochondria were also unevenly distributed, with clustered organelles alternating with areas where mitochondria were sparse. These abnormalities were not associated with altered bioenergetics or increased susceptibility to pro-apoptotic stimuli. Therefore, changes in mitochondrial shape and distribution can be independent of other reported effects of OPA1 mutations, and therefore may be the primary cause of the disease. The arrangement of mitochondria in RGCs, which degenerate in ADOA, may be exquisitely sensitive to disturbance, and this may lead to bioenergetic crisis and/or induction of apoptosis. Our results highlight the importance of mitochondrial dynamics in the disease per se, and point to the loss of the fine positioning of mitochondria in the axons of RGCs as a possible explanation for their predominant degeneration in ADOA.
Collapse
|
30
|
Bortolozzi M, Lelli A, Mammano F. Calcium microdomains at presynaptic active zones of vertebrate hair cells unmasked by stochastic deconvolution. Cell Calcium 2008; 44:158-68. [PMID: 18249440 DOI: 10.1016/j.ceca.2007.11.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 11/01/2007] [Accepted: 11/08/2007] [Indexed: 11/15/2022]
Abstract
Signal transduction by auditory and vestibular hair cells involves an impressive ensemble of finely tuned control mechanisms, strictly dependent on the local intracellular Ca(2+) concentration ([Ca(2+)](i)). The study of Ca(2+) dynamics in hair cells typically combines Ca(2+)-sensitive fluorescent indicators (dyes), patch clamp and optical microscopy to produce images of the patterns of fluorescence of a Ca(2+) indicator following various stimulation protocols. Here we describe a novel method that combines electrophysiological recordings, fluorescence imaging and numerical simulations to effectively deconvolve Ca(2+) signals within cytoplasmic microdomains that would otherwise remain inaccessible to direct observation. The method relies on the comparison of experimental data with virtual signals derived from a Monte Carlo reaction-diffusion model based on a realistic reconstruction of the relevant cell boundaries in three dimensions. The model comprises Ca(2+) entry at individual presynaptic active zones followed by diffusion, buffering, extrusion and release of Ca(2+). Our results indicate that changes of the hair cell [Ca(2+)](i) during synaptic transmission are primarily controlled by the Ca(2+) endogenous buffers both at short (<1mu) and at long (tens of microns) distances from the active zones. We provide quantitative estimates of concentration and kinetics of the hair cell endogenous Ca(2+) buffers and Ca(2+)-ATPases. We finally show that experimental fluorescence data collected during Ca(2+) influx are not interpreted correctly if the [Ca(2+)](i) is estimated by assuming that Ca(2+) equilibrates instantly with its reactants. In our opinion, this approach is of potentially general interest as it can be easily adapted to the study of Ca(2+) dynamics in diverse biological systems.
Collapse
Affiliation(s)
- Mario Bortolozzi
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine, via G. Orus 2, 35129 Padova, Italy
| | | | | |
Collapse
|
31
|
Abstract
The inner ear contains delicate sensory receptors that have adapted to detect the minutest mechanical disturbances. Ca(2+) ions are implicated in all steps of the transduction process, as well as in its regulation by an impressive ensemble of finely tuned feedback control mechanisms. Recent studies have unveiled some of the key players, but things do not sound quite right yet.
Collapse
Affiliation(s)
- Fabio Mammano
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, Padua, Italy.
| | | | | | | |
Collapse
|
32
|
Hernandez VH, Bortolozzi M, Pertegato V, Beltramello M, Giarin M, Zaccolo M, Pantano S, Mammano F. Unitary permeability of gap junction channels to second messengers measured by FRET microscopy. Nat Methods 2007; 4:353-8. [PMID: 17351620 DOI: 10.1038/nmeth1031] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Accepted: 02/22/2007] [Indexed: 11/08/2022]
Abstract
Gap junction channels assembled from connexin protein subunits mediate intercellular transfer of ions and metabolites. Impaired channel function is implicated in several hereditary human diseases. In particular, defective permeation of cAMP or inositol-1,4,5-trisphosphate (InsP(3)) through connexin channels is associated with peripheral neuropathies and deafness, respectively. Here we present a method to estimate the permeability of single gap junction channels to second messengers. Using HeLa cells that overexpressed wild-type human connexin 26 (HCx26wt) as a model system, we combined measurements of junctional conductance and fluorescence resonance energy transfer (FRET) emission ratio of biosensors selective for cAMP and InsP(3). The unitary permeabilities to cAMP (47 x 10(-3) +/- 15 x 10(-3) microm(3)/s) and InsP(3) (60 x 10(-3) +/- 12 x 10(-3) microm(3)/s) were similar, but substantially larger than the unitary permeability to lucifer yellow (LY; 7 +/- 3 x 10(-3) microm(3)/s), an exogenous tracer. This method permits quantification of defects of metabolic coupling and can be used to investigate interdependence of intercellular diffusion and cross-talk between diverse signaling pathways.
Collapse
Affiliation(s)
- Victor H Hernandez
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Ficarella R, Di Leva F, Bortolozzi M, Ortolano S, Donaudy F, Petrillo M, Melchionda S, Lelli A, Domi T, Fedrizzi L, Lim D, Shull GE, Gasparini P, Brini M, Mammano F, Carafoli E. A functional study of plasma-membrane calcium-pump isoform 2 mutants causing digenic deafness. Proc Natl Acad Sci U S A 2007; 104:1516-21. [PMID: 17234811 PMCID: PMC1785272 DOI: 10.1073/pnas.0609775104] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ca2+ enters the stereocilia of hair cells through mechanoelectrical transduction channels opened by the deflection of the hair bundle and is exported back to endolymph by an unusual splicing isoform (w/a) of plasma-membrane calcium-pump isoform 2 (PMCA2). Ablation or missense mutations of the pump cause deafness, as described for the G283S mutation in the deafwaddler (dfw) mouse. A deafness-inducing missense mutation of PMCA2 (G293S) has been identified in a human family. The family also was screened for mutations in cadherin 23, which accentuated hearing loss in a previously described human family with a PMCA2 mutation. A T1999S substitution was detected in the cadherin 23 gene of the healthy father and affected son but not in that of the unaffected mother, who presented instead the PMCA2 mutation. The w/a isoform was overexpressed in CHO cells. At variance with the other PMCA2 isoforms, it became activated only marginally when exposed to a Ca2+ pulse. The G293S and G283S mutations delayed the dissipation of Ca2+ transients induced in CHO cells by InsP3. In organotypic cultures, Ca2+ imaging of vestibular hair cells showed that the dissipation of stereociliary Ca2+ transients induced by Ca2+ uncaging was compromised in the dfw and PMCA2 knockout mice, as was the sensitivity of the mechanoelectrical transduction channels to hair bundle displacement in cochlear hair cells.
Collapse
Affiliation(s)
- R. Ficarella
- *Telethon Institute of Genetics and Medicine, 80131 Naples, Italy
| | - F. Di Leva
- Departments of Biochemistry, Experimental Veterinary Sciences, and
| | - M. Bortolozzi
- Venetian Institute of Molecular Medicine, 35129 Padua, Italy
| | - S. Ortolano
- Venetian Institute of Molecular Medicine, 35129 Padua, Italy
| | - F. Donaudy
- *Telethon Institute of Genetics and Medicine, 80131 Naples, Italy
| | - M. Petrillo
- *Telethon Institute of Genetics and Medicine, 80131 Naples, Italy
| | - S. Melchionda
- Unit of Medical Genetics, Instituto di Ricovero e Cura a Carattere Scientifico, Casa Sollievo della Sofferenza, 71013 San Giovanni Rotondo, Italy
| | - A. Lelli
- Venetian Institute of Molecular Medicine, 35129 Padua, Italy
| | - T. Domi
- Departments of Biochemistry, Experimental Veterinary Sciences, and
| | - L. Fedrizzi
- Departments of Biochemistry, Experimental Veterinary Sciences, and
| | - D. Lim
- Venetian Institute of Molecular Medicine, 35129 Padua, Italy
| | - G. E. Shull
- Department of Molecular Genetics, University of Cincinnati, Cincinnati, OH 45221; and
| | - P. Gasparini
- *Telethon Institute of Genetics and Medicine, 80131 Naples, Italy
- Unit of Medical Genetics, Department of Reproductive Science and Development, Instituto di Ricovero e Cura a Carattere Scientifico-Burlo Garofalo, University of Trieste, 34127 Trieste, Italy
| | - M. Brini
- Departments of Biochemistry, Experimental Veterinary Sciences, and
- **To whom correspondence may be addressed. E-mail:
, , or fabio.mammano@unipd
| | - F. Mammano
- Physics, University of Padua, 35121 Padua, Italy
- Venetian Institute of Molecular Medicine, 35129 Padua, Italy
- **To whom correspondence may be addressed. E-mail:
, , or fabio.mammano@unipd
| | - E. Carafoli
- Venetian Institute of Molecular Medicine, 35129 Padua, Italy
- **To whom correspondence may be addressed. E-mail:
, , or fabio.mammano@unipd
| |
Collapse
|