1
|
Vera E, Cornejo I, Niemeyer MI, Sepúlveda FV, Cid LP. Altered phosphatidylinositol regulation of mutant inwardly rectifying K + Kir7.1 channels associated with inherited retinal degeneration disease. J Physiol 2020; 599:593-608. [PMID: 33219695 DOI: 10.1113/jp280681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 11/12/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Kir7.1 K+ channel expressed in retinal pigment epithelium is mutated in inherited retinal degeneration diseases. We study Kir7.1 in heterologous expression to test the hypothesis that pathological R162 mutation to neutral amino acids results in loss of a crucial site that binds PI(4,5)P2 . Although R162W mutation inactivates Kir7.1, changes to smaller volume (e.g. Gln) amino acids are tolerated or even enhance function (Ala or Cys). Chemical modification of Kir7.1-R162C confirms that large residues of the size of Trp are incompatible with normal channel function even if positively charged. In addition to R162, K164 (and possibly K159) forms a binding site for the phosphoinositide and is essential for channel activity. R162 substitution with a large, neutral side chain like Trp exerts a dominant negative effect on Kir7.1 activity such that less than one fifth of the full activity is expected in a cell expressing the same amount of mutant and wild-type channels. ABSTRACT Mutations in the Kir7.1 K+ channel, highly expressed in retinal pigment epithelium, have been linked to inherited retinal degeneration diseases. Examples are mutations changing Arg 162 to Trp in snowflake vitreoretinal degeneration (SVD) and Gln in retinitis pigmentosa. R162 is believed to be part of a site that binds PI(4,5)P2 and stabilises the open state. We have tested the hypothesis that R162 mutation to neutral amino acids will result in the loss of this crucial interaction to the detriment of channel function. Our findings indicate that although R612W mutation inactivates Kir7.1, changes to smaller volume (e.g. Gln) amino acids are tolerated or even enhance function (Ala or Cys). Cys chemical modification of Kir7.1-R162C confirms that large residues of the size of Trp are incompatible with normal channel function even if positively charged. Experiments titrating the levels of plasma membrane PI(4,5)P2 with voltage-dependent phosphatase DrVSP reveal that, in addition to R162, K164 (and possibly K159) forms a binding site for the phosphoinositide and ensures channel activity. Finally, the use of a concatemeric approach shows that substitution of R162 with a large, neutral side chain mimicking a Trp residue exerts a dominant negative effect on Kir7.1 activity such that less than one fifth of the full activity is expected in heterozygous cells carrying the SVD mutation. Our results suggest that if mutations in the human KCNJ13 gene resulting in the neutralisation of R162 and Kir7.1 malfunction led to retinal degeneration diseases, their severity might depend on the nature of the side chain of the replacing amino acid.
Collapse
Affiliation(s)
- Erwin Vera
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | | | | | | | - L Pablo Cid
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| |
Collapse
|
2
|
Catalán MA, Julio-Kalajzić F, Niemeyer MI, Cid LP, Sepúlveda FV. Short Chain Fatty Acids Effect on Chloride Channel ClC-2 as a Possible Mechanism for Lubiprostone Intestinal Action. Cells 2020; 9:cells9081781. [PMID: 32722648 PMCID: PMC7464869 DOI: 10.3390/cells9081781] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 07/22/2020] [Accepted: 07/23/2020] [Indexed: 01/22/2023] Open
Abstract
Lubiprostone, a 20-carbon synthetic fatty acid used for the treatment of constipation, is thought to act through an action on Cl− channel ClC-2. Short chain fatty acids (SCFAs) are produced and absorbed in the distal intestine. We explore whether SCFAs affect ClC-2, re-examine a possible direct effect of lubiprostone on ClC-2, and use mice deficient in ClC-2 to stringently address the hypothesis that the epithelial effect of lubiprostone targets this anion channel. Patch-clamp whole cell recordings of ClC-2 expressed in mammalian cells are used to assay SCFA and lubiprostone effects. Using chamber measurements of ion current in mice deficient in ClC-2 or CFTR channels served to analyze the target of lubiprostone in the distal intestinal epithelium. Intracellular SCFAs had a dual action on ClC-2, partially inhibiting conduction but, importantly, facilitating the voltage activation of ClC-2. Intra- or extracellular lubiprostone had no effect on ClC-2 currents. Lubiprostone elicited a secretory current across colonic epithelia that was increased in mice deficient in ClC-2, consistent with the channel’s proposed proabsorptive function, but absent from those deficient in CFTR. Whilst SCFAs might exert a physiological effect on ClC-2 as part of their known proabsorptive effect, ClC-2 plays no part in the lubiprostone intestinal effect that appears mediated by CFTR activation.
Collapse
Affiliation(s)
- Marcelo A. Catalán
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia 5110466, Chile; (F.J.-K.); (M.I.N.); (L.P.C.)
- Instituto de Fisiología, Facultad de Medicina, Universidad Austral de Chile, Valdivia 5090000, Chile
- Correspondence: (M.A.C.); (F.V.S.); Tel.: +56-63-2221686 (M.A.C.)
| | - Francisca Julio-Kalajzić
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia 5110466, Chile; (F.J.-K.); (M.I.N.); (L.P.C.)
| | - María Isabel Niemeyer
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia 5110466, Chile; (F.J.-K.); (M.I.N.); (L.P.C.)
| | - Luis Pablo Cid
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia 5110466, Chile; (F.J.-K.); (M.I.N.); (L.P.C.)
| | - Francisco V. Sepúlveda
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia 5110466, Chile; (F.J.-K.); (M.I.N.); (L.P.C.)
- Correspondence: (M.A.C.); (F.V.S.); Tel.: +56-63-2221686 (M.A.C.)
| |
Collapse
|
3
|
Vera E, Cornejo I, Burgos J, Niemeyer MI, Sepúlveda FV, Cid LP. A novel Kir7.1 splice variant expressed in various mouse tissues shares organisational and functional properties with human Leber amaurosis-causing mutations of this K + channel. Biochem Biophys Res Commun 2019; 514:574-579. [PMID: 31056263 DOI: 10.1016/j.bbrc.2019.04.169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 04/24/2019] [Indexed: 01/27/2023]
Abstract
Kir7.1 is an inwardly rectifying K+ channel present in epithelia where it shares membrane localization with the Na+/K+-pump. In the present communication we report the presence of a novel splice variant of Kir7.1 in mouse tissues including kidney, lung, choroid plexus and retinal pigment epithelium (RPE). The variant named mKir7.1-SV2 lacks most of the C-terminus domain but is predicted to have the two transmembrane domains and permeation pathway unaffected. Similarly truncated predicted proteins, Kir7.1-R166X and Kir7.1-Q219X, would arise from mutations associated with Leber Congenital Amaurosis, a rare recessive hereditary retinal disease that results in vision loss at early age. We found that mKir7.1-SV2 and the pathological variants do not produce any channel activity when expressed alone in HEK-293 cells due to their scarce presence in the plasma membrane. Simultaneous expression with the full length Kir7.1 however leads to a reduction in activity of the wild-type channel that might be due to partial proteasome degradation of WT-mutant channel heteromers.
Collapse
Affiliation(s)
- Erwin Vera
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | - Isabel Cornejo
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | - Johanna Burgos
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | | | | | - L Pablo Cid
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile.
| |
Collapse
|
4
|
Gaitán-Peñas H, Apaja PM, Arnedo T, Castellanos A, Elorza-Vidal X, Soto D, Gasull X, Lukacs GL, Estévez R. Leukoencephalopathy-causing CLCN2 mutations are associated with impaired Cl - channel function and trafficking. J Physiol 2017; 595:6993-7008. [PMID: 28905383 DOI: 10.1113/jp275087] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 09/11/2017] [Indexed: 01/30/2023] Open
Abstract
KEY POINTS Characterisation of most mutations found in CLCN2 in patients with CC2L leukodystrophy show that they cause a reduction in function of the chloride channel ClC-2. GlialCAM, a regulatory subunit of ClC-2 in glial cells and involved in the leukodystrophy megalencephalic leukoencephalopathy with subcortical cysts (MLC), increases the activity of a ClC-2 mutant by affecting ClC-2 gating and by stabilising the mutant at the plasma membrane. The stabilisation of ClC-2 at the plasma membrane by GlialCAM depends on its localisation at cell-cell junctions. The membrane protein MLC1, which is defective in MLC, also contributes to the stabilisation of ClC-2 at the plasma membrane, providing further support for the view that GlialCAM, MLC1 and ClC-2 form a protein complex in glial cells. ABSTRACT Mutations in CLCN2 have been recently identified in patients suffering from a type of leukoencephalopathy involving intramyelinic oedema. Here, we characterised most of these mutations that reduce the function of the chloride channel ClC-2 and impair its plasma membrane (PM) expression. Detailed biochemical and electrophysiological analyses of the Ala500Val mutation revealed that defective gating and increased cellular and PM turnover contributed to defective A500V-ClC-2 functional expression. Co-expression of the adhesion molecule GlialCAM, which forms a tertiary complex with ClC-2 and megalencephalic leukoencephalopathy with subcortical cysts 1 (MLC1), rescued the functional expression of the mutant by modifying its gating properties. GlialCAM also restored the PM levels of the channel by impeding its turnover at the PM. This rescue required ClC-2 localisation to cell-cell junctions, since a GlialCAM mutant with compromised junctional localisation failed to rescue the impaired stability of mutant ClC-2 at the PM. Wild-type, but not mutant, ClC-2 was also stabilised by MLC1 overexpression. We suggest that leukodystrophy-causing CLCN2 mutations reduce the functional expression of ClC-2, which is partly counteracted by GlialCAM/MLC1-mediated increase in the gating and stability of the channel.
Collapse
Affiliation(s)
- Héctor Gaitán-Peñas
- Unitat de Fisiología, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Spain
| | - Pirjo M Apaja
- Department of Physiology, McGill University, Montréal, Quebec, H3E 1Y6, Canada.,Research Group Focused on Protein Structure, McGill University, Montréal, Quebec, H3E 1Y6, Canada.,South Australian Health and Medical Research Institute, Nutrition and Metabolism Theme and EMBL Australia, 5000, Adelaide, Australia
| | - Tanit Arnedo
- Unitat de Fisiología, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Spain
| | - Aida Castellanos
- Neurophysiology Laboratory, Physiology Unit, Department of Biomedicine, Medical School, Institute of Neurosciences, IDIBAPS, University of Barcelona, Barcelona, Spain
| | - Xabier Elorza-Vidal
- Unitat de Fisiología, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Spain
| | - David Soto
- Neurophysiology Laboratory, Physiology Unit, Department of Biomedicine, Medical School, Institute of Neurosciences, IDIBAPS, University of Barcelona, Barcelona, Spain
| | - Xavier Gasull
- Neurophysiology Laboratory, Physiology Unit, Department of Biomedicine, Medical School, Institute of Neurosciences, IDIBAPS, University of Barcelona, Barcelona, Spain
| | - Gergely L Lukacs
- Department of Physiology, McGill University, Montréal, Quebec, H3E 1Y6, Canada.,Research Group Focused on Protein Structure, McGill University, Montréal, Quebec, H3E 1Y6, Canada
| | - Raúl Estévez
- Unitat de Fisiología, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Spain
| |
Collapse
|
5
|
Wang H, Xu M, Kong Q, Sun P, Yan F, Tian W, Wang X. Research and progress on ClC‑2 (Review). Mol Med Rep 2017; 16:11-22. [PMID: 28534947 PMCID: PMC5482133 DOI: 10.3892/mmr.2017.6600] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 02/13/2017] [Indexed: 12/22/2022] Open
Abstract
Chloride channel 2 (ClC-2) is one of the nine mammalian members of the ClC family. The present review discusses the molecular properties of ClC‑2, including CLCN2, ClC‑2 promoter and the structural properties of ClC‑2 protein; physiological properties; functional properties, including the regulation of cell volume. The effects of ClC‑2 on the digestive, respiratory, circulatory, nervous and optical systems are also discussed, in addition to the mechanisms involved in the regulation of ClC‑2. The review then discusses the diseases associated with ClC‑2, including degeneration of the retina, Sjögren's syndrome, age‑related cataracts, degeneration of the testes, azoospermia, lung cancer, constipation, repair of impaired intestinal mucosa barrier, leukemia, cystic fibrosis, leukoencephalopathy, epilepsy and diabetes mellitus. It was concluded that future investigations of ClC‑2 are likely to be focused on developing specific drugs, activators and inhibitors regulating the expression of ClC‑2 to treat diseases associated with ClC‑2. The determination of CLCN2 is required to prevent and treat several diseases associated with ClC‑2.
Collapse
Affiliation(s)
- Hongwei Wang
- Department of Ophthalmology, People's Hospital of Jingjiang, Jingjiang, Jiangsu 214500, P.R. China
| | - Minghui Xu
- Library, Qiqihar Medical University, Qiqihar, Heilongjiang 161006, P.R. China
| | - Qingjie Kong
- School of Computer Science and Information Technology, Northeast Normal University, Changchun, Jilin 130024, P.R. China
| | - Peng Sun
- Department of Ophthalmology, The First Affiliated Hospital of Jiamusi University, Jiamusi, Heilongjiang 154000, P.R. China
| | - Fengyun Yan
- Assets Division, Harbin University of Science and Technology, Harbin, Heilongjiang 150080, P.R. China
| | - Wenying Tian
- Library, Qiqihar Medical University, Qiqihar, Heilongjiang 161006, P.R. China
| | - Xin Wang
- Library, Qiqihar Medical University, Qiqihar, Heilongjiang 161006, P.R. China
| |
Collapse
|
6
|
Sirisi S, Elorza-Vidal X, Arnedo T, Armand-Ugón M, Callejo G, Capdevila-Nortes X, López-Hernández T, Schulte U, Barrallo-Gimeno A, Nunes V, Gasull X, Estévez R. Depolarization causes the formation of a ternary complex between GlialCAM, MLC1 and ClC-2 in astrocytes: implications in megalencephalic leukoencephalopathy. Hum Mol Genet 2017; 26:2436-2450. [DOI: 10.1093/hmg/ddx134] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 03/29/2017] [Indexed: 01/06/2023] Open
|
7
|
Nighot PK, Leung L, Ma TY. Chloride channel ClC- 2 enhances intestinal epithelial tight junction barrier function via regulation of caveolin-1 and caveolar trafficking of occludin. Exp Cell Res 2017; 352:113-122. [PMID: 28161538 DOI: 10.1016/j.yexcr.2017.01.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 01/09/2017] [Accepted: 01/31/2017] [Indexed: 12/16/2022]
Abstract
Previous studies have demonstrated that the chloride channel ClC-2 plays a critical role in intestinal epithelial tight junction (TJ) barrier function via intracellular trafficking of TJ protein occludin. To study the mechanism of ClC-2-mediated TJ barrier function and intracellular trafficking of occludin, we established ClC-2 over-expressing Caco-2 cell line (Caco-2CLCN2) by full length ClC-2 ORF transfection. ClC-2 over-expression (Caco-2CLCN2) significantly enhanced TJ barrier (increased TER by ≥2 times and reduced inulin flux by 50%) compared to control Caco-2pEZ cells. ClC-2 over-expression (Caco-2CLCN2) increased occludin protein level compared to control Caco-2pEZ cells. Surface biotinylation assay revealed reduced steady state endocytosis of occludin in Caco-2CLCN2 cells. Furthermore, ClC-2 over-expression led to reduction in caveolin-1 protein level and diminishment of caveolae assembly. Caveolae disruption increased TJ permeability in control but not ClC-2 over-expressing Caco-2CLCN2 cells. Selective ClC-2 channel blocker GaTx2 caused an increase in caveolin-1 protein level and reduced occludin level. Delivery of cell permeable caveolin-1 scaffolding domain reduced the occludin protein level. Over all, these results suggest that ClC- 2 enhances TJ barrier function in intestinal epithelial cells via regulation of caveolin-1 and caveolae-mediated trafficking of occludin.
Collapse
Affiliation(s)
- Prashant K Nighot
- Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA.
| | - Lana Leung
- Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Thomas Y Ma
- Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| |
Collapse
|
8
|
Capdevila-Nortes X, Jeworutzki E, Elorza-Vidal X, Barrallo-Gimeno A, Pusch M, Estévez R. Structural determinants of interaction, trafficking and function in the ClC-2/MLC1 subunit GlialCAM involved in leukodystrophy. J Physiol 2015; 593:4165-80. [PMID: 26033718 DOI: 10.1113/jp270467] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 05/22/2015] [Indexed: 02/03/2023] Open
Abstract
KEY POINTS The extracellular domain of GlialCAM is necessary for its targeting to cell junctions, as well as for interactions with itself and MLC1 and ClC-2. The C-terminus of GlialCAM is not necessary for interaction but is required for targeting to cell junctions. The first three residues of the transmembrane segment of GlialCAM are required for GlialCAM-mediated ClC-2 activation. ABSTRACT Mutations in the genes encoding the astrocytic protein MLC1, the cell adhesion molecule GlialCAM or the Cl(-) channel ClC-2 underlie human leukodystrophies. GlialCAM binds to itself, to MLC1 and to ClC-2, and directs these proteins to cell-cell contacts. In addition, GlialCAM dramatically activates ClC-2 mediated currents. In the present study, we used mutagenesis studies combined with functional and biochemical analyses to determine which parts of GlialCAM are required to perform these cellular functions. We found that the extracellular domain of GlialCAM is necessary for cell junction targeting and for mediating interactions with itself or with MLC1 and ClC-2. The C-terminus is also necessary for proper targeting to cell-cell junctions but is not required for the biochemical interaction. Finally, we identified the first three amino acids of the transmembrane segment of GlialCAM as being essential for the activation of ClC-2 currents but not for targeting or biochemical interaction. Our results provide new mechanistic insights concerning the regulation of the cell biology and function of MLC1 and ClC-2 by GlialCAM.
Collapse
Affiliation(s)
- Xavier Capdevila-Nortes
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Barcelona, Spain
| | - Elena Jeworutzki
- Istituto di Biofisica, CNR, Genoa, Italy.,Present address IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, Münster, Germany
| | - Xabier Elorza-Vidal
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Barcelona, Spain.,U-750, Centro de investigación en red de enfermedades raras (CIBERER), ISCIII, Barcelona, Spain
| | - Alejandro Barrallo-Gimeno
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Barcelona, Spain
| | | | - Raúl Estévez
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Barcelona, Spain.,U-750, Centro de investigación en red de enfermedades raras (CIBERER), ISCIII, Barcelona, Spain
| |
Collapse
|
9
|
de la Fuente-Ortega E, Gravotta D, Perez Bay A, Benedicto I, Carvajal-Gonzalez JM, Lehmann GL, Lagos CF, Rodríguez-Boulan E. Basolateral sorting of chloride channel 2 is mediated by interactions between a dileucine motif and the clathrin adaptor AP-1. Mol Biol Cell 2015; 26:1728-42. [PMID: 25739457 PMCID: PMC4436783 DOI: 10.1091/mbc.e15-01-0047] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 02/25/2015] [Indexed: 01/03/2023] Open
Abstract
ClC-2 is a ubiquitous chloride channel that regulates cell volume, ion transport, and acid-base balance. Mice knocked out for ClC-2 are blind and sterile. Basolateral localization of ClC-2 in epithelia is mediated by the interaction of a dileucine motif with a highly conserved pocket in the γ1-σ1A hemicomplex of AP-1. In spite of the many key cellular functions of chloride channels, the mechanisms that mediate their subcellular localization are largely unknown. ClC-2 is a ubiquitous chloride channel usually localized to the basolateral domain of epithelia that regulates cell volume, ion transport, and acid–base balance; mice knocked out for ClC-2 are blind and sterile. Previous work suggested that CLC-2 is sorted basolaterally by TIFS812LL, a dileucine motif in CLC-2's C-terminal domain. However, our in silico modeling of ClC-2 suggested that this motif was buried within the channel's dimerization interface and identified two cytoplasmically exposed dileucine motifs, ESMI623LL and QVVA635LL, as candidate sorting signals. Alanine mutagenesis and trafficking assays support a scenario in which ESMI623LL acts as the authentic basolateral signal of ClC-2. Silencing experiments and yeast three-hybrid assays demonstrated that both ubiquitous (AP-1A) and epithelium-specific (AP-1B) forms of the tetrameric clathrin adaptor AP-1 are capable of carrying out basolateral sorting of ClC-2 through interactions of ESMI623LL with a highly conserved pocket in their γ1-σ1A hemicomplex.
Collapse
Affiliation(s)
- Erwin de la Fuente-Ortega
- Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | - Diego Gravotta
- Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | - Andres Perez Bay
- Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | - Ignacio Benedicto
- Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | | | - Guillermo L Lehmann
- Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| | - Carlos F Lagos
- Department of Endocrinology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago Centro 8330074, Santiago, Chile Facultad de Ciencia, Universidad San Sebastián, Providencia 7510157, Santiago, Chile
| | - Enrique Rodríguez-Boulan
- Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065
| |
Collapse
|
10
|
Bi MM, Hong S, Zhou HY, Wang HW, Wang LN, Zheng YJ. Chloride channelopathies of ClC-2. Int J Mol Sci 2013; 15:218-49. [PMID: 24378849 PMCID: PMC3907807 DOI: 10.3390/ijms15010218] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/14/2013] [Accepted: 12/16/2013] [Indexed: 12/15/2022] Open
Abstract
Chloride channels (ClCs) have gained worldwide interest because of their molecular diversity, widespread distribution in mammalian tissues and organs, and their link to various human diseases. Nine different ClCs have been molecularly identified and functionally characterized in mammals. ClC-2 is one of nine mammalian members of the ClC family. It possesses unique biophysical characteristics, pharmacological properties, and molecular features that distinguish it from other ClC family members. ClC-2 has wide organ/tissue distribution and is ubiquitously expressed. Published studies consistently point to a high degree of conservation of ClC-2 function and regulation across various species from nematodes to humans over vast evolutionary time spans. ClC-2 has been intensively and extensively studied over the past two decades, leading to the accumulation of a plethora of information to advance our understanding of its pathophysiological functions; however, many controversies still exist. It is necessary to analyze the research findings, and integrate different views to have a better understanding of ClC-2. This review focuses on ClC-2 only, providing an analytical overview of the available literature. Nearly every aspect of ClC-2 is discussed in the review: molecular features, biophysical characteristics, pharmacological properties, cellular function, regulation of expression and function, and channelopathies.
Collapse
Affiliation(s)
- Miao Miao Bi
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Sen Hong
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Hong Yan Zhou
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Hong Wei Wang
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Li Na Wang
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Ya Juan Zheng
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| |
Collapse
|
11
|
Stauber T, Weinert S, Jentsch TJ. Cell biology and physiology of CLC chloride channels and transporters. Compr Physiol 2013; 2:1701-44. [PMID: 23723021 DOI: 10.1002/cphy.c110038] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Proteins of the CLC gene family assemble to homo- or sometimes heterodimers and either function as Cl(-) channels or as Cl(-)/H(+)-exchangers. CLC proteins are present in all phyla. Detailed structural information is available from crystal structures of bacterial and algal CLCs. Mammals express nine CLC genes, four of which encode Cl(-) channels and five 2Cl(-)/H(+)-exchangers. Two accessory β-subunits are known: (1) barttin and (2) Ostm1. ClC-Ka and ClC-Kb Cl(-) channels need barttin, whereas Ostm1 is required for the function of the lysosomal ClC-7 2Cl(-)/H(+)-exchanger. ClC-1, -2, -Ka and -Kb Cl(-) channels reside in the plasma membrane and function in the control of electrical excitability of muscles or neurons, in extra- and intracellular ion homeostasis, and in transepithelial transport. The mainly endosomal/lysosomal Cl(-)/H(+)-exchangers ClC-3 to ClC-7 may facilitate vesicular acidification by shunting currents of proton pumps and increase vesicular Cl(-) concentration. ClC-3 is also present on synaptic vesicles, whereas ClC-4 and -5 can reach the plasma membrane to some extent. ClC-7/Ostm1 is coinserted with the vesicular H(+)-ATPase into the acid-secreting ruffled border membrane of osteoclasts. Mice or humans lacking ClC-7 or Ostm1 display osteopetrosis and lysosomal storage disease. Disruption of the endosomal ClC-5 Cl(-)/H(+)-exchanger leads to proteinuria and Dent's disease. Mouse models in which ClC-5 or ClC-7 is converted to uncoupled Cl(-) conductors suggest an important role of vesicular Cl(-) accumulation in these pathologies. The important functions of CLC Cl(-) channels were also revealed by human diseases and mouse models, with phenotypes including myotonia, renal loss of salt and water, deafness, blindness, leukodystrophy, and male infertility.
Collapse
Affiliation(s)
- Tobias Stauber
- Leibniz-Institut für Molekulare Pharmakologie FMP and Max-Delbrück-Centrum für Molekulare Medizin MDC, Berlin, Germany
| | | | | |
Collapse
|
12
|
Hicks DA, Nalivaeva NN, Turner AJ. Lipid rafts and Alzheimer's disease: protein-lipid interactions and perturbation of signaling. Front Physiol 2012; 3:189. [PMID: 22737128 PMCID: PMC3381238 DOI: 10.3389/fphys.2012.00189] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 05/21/2012] [Indexed: 12/16/2022] Open
Abstract
Lipid rafts are membrane domains, more ordered than the bulk membrane and enriched in cholesterol and sphingolipids. They represent a platform for protein-lipid and protein–protein interactions and for cellular signaling events. In addition to their normal functions, including membrane trafficking, ligand binding (including viruses), axonal development and maintenance of synaptic integrity, rafts have also been implicated in the pathogenesis of several neurodegenerative diseases including Alzheimer’s disease (AD). Lipid rafts promote interaction of the amyloid precursor protein (APP) with the secretase (BACE-1) responsible for generation of the amyloid β peptide, Aβ. Rafts also regulate cholinergic signaling as well as acetylcholinesterase and Aβ interaction. In addition, such major lipid raft components as cholesterol and GM1 ganglioside have been directly implicated in pathogenesis of the disease. Perturbation of lipid raft integrity can also affect various signaling pathways leading to cellular death and AD. In this review, we discuss modulation of APP cleavage by lipid rafts and their components, while also looking at more recent findings on the role of lipid rafts in signaling events.
Collapse
Affiliation(s)
- David A Hicks
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds Leeds, UK
| | | | | |
Collapse
|
13
|
Catalán MA, Flores CA, González-Begne M, Zhang Y, Sepúlveda FV, Melvin JE. Severe defects in absorptive ion transport in distal colons of mice that lack ClC-2 channels. Gastroenterology 2012; 142:346-54. [PMID: 22079595 PMCID: PMC3267842 DOI: 10.1053/j.gastro.2011.10.037] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 10/25/2011] [Accepted: 10/26/2011] [Indexed: 01/05/2023]
Abstract
BACKGROUND & AIMS The fluid secretion model predicts that intestinal obstruction disorders can be alleviated by promoting epithelial Cl(-) secretion. The adenosine 3',5'-cyclic monophosphate (cAMP)-activated anion channel CFTR mediates Cl(-)-dependent fluid secretion in the intestine. Although the role of the ClC-2 channel has not been determined in the intestine, this voltage-gated Cl(-) channel might compensate for the secretory defects observed in patients with cystic fibrosis and other chronic constipation disorders. We investigated whether mice that lack ClC-2 channels (Clcn2(-/-)) have defects in intestinal ion transport. METHODS Immunolocalization and immunoblot analyses were used to determine the cellular localization and the amount of ClC-2 expressed in mouse early distal colon (EDC) and late distal colon (LDC). Colon sheets from wild-type and Clcn2(-/-) littermates were mounted in Ussing chambers to determine transepithelial bioelectrical parameters and Na(+), K(+), and Cl(-) fluxes. RESULTS Expression of ClC-2 was higher in the basolateral membrane of surface cells in the EDC compared with the LDC, with little expression in crypts. Neither cAMP nor Ca(2+)-induced secretion of Cl(-) was affected in the EDC or LDC of Clcn2(-/-) mice, whereas the amiloride-sensitive short-circuit current was increased approximately 3-fold in Clcn2(-/-) EDC compared with control littermates. Conversely, electroneutral Na(+), K(+), and Cl(-) absorption was dramatically reduced in colons of Clcn2(-/-) mice. CONCLUSIONS Basolateral ClC-2 channels are required for colonic electroneutral absorption of NaCl and KCl. The increase in the amiloride-sensitive short-circuit current in Clcn2(-/-) mice revealed a compensatory mechanism that is activated in the colons of mice that lack the ClC-2 channel.
Collapse
Affiliation(s)
- Marcelo A. Catalán
- Secretory Mechanisms and Dysfunction Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, 10 Center Drive, Building 10/Room 5N102, Bethesda, MD 20892 USA
| | | | - Mireya González-Begne
- Center for Oral Biology, University of Rochester Medical Center, Rochester, NY 14642 USA
| | - Yan Zhang
- Secretory Mechanisms and Dysfunction Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, 10 Center Drive, Building 10/Room 5N102, Bethesda, MD 20892 USA
| | | | - James E. Melvin
- Secretory Mechanisms and Dysfunction Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, 10 Center Drive, Building 10/Room 5N102, Bethesda, MD 20892 USA
| |
Collapse
|
14
|
Chen ZY, Wang YG, Yang P, Huang WG, Zhou YS, Feng XS. Relationship between CLC-2 and intestinal mucosal barrier in rats with obstructive jaundice. Shijie Huaren Xiaohua Zazhi 2011; 19:2829-2834. [DOI: 10.11569/wcjd.v19.i27.2829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the relationship between chloride channel-2 (CLC-2) and intestinal mucosal barrier in rats with obstructive jaundice (OJ).
METHODS: Rats were randomly divided into five groups: sham operation group, OJ group, lubiprostone (Lu) group, glucagon-like peptide-2 (GLP-2) group, and Lu + GLP group. Except for the sham operation group, OJ was induced by bile duct ligation in rats of other groups. The Lu group was subcutaneously injected with LU, and the GLP-2 group was injected with GLP-2. The Lu + GLP group was injected with both Lu and GLP-2. The animals were sacrificed 7 days after treatment. The ratio of lactulose to mannitol (L/M) and plasma endotoxin levels were measured. Western blot was used to examine the changes in the expression tight junction proteins zonula occludens-1 (ZO-1) and CLC-2 in epithelial cells in the terminal ileum.
RESULTS: The ratio of L/M was significantly higher in all the experiment groups than in the sham operation group (all P = 0.00), but was significantly lower in the Lu group, GLP-2 group and Lu + GLP group than in the OJ group (0.545 ± 0.03, 0.512 ± 0.03, 0.482 ± 0.05 vs 0.656 ± 0.04, all P = 0.00). Plasma endotoxin levels increased in all the experiment groups, highest in the OJ group and decreasing somewhat in the Lu group, GLP-2 group and Lu + GLP group. The relative expression of ZO-1 in the Lu group (0.209 ± 0.03) was higher than that in the OJ group (0.178 ± 0.03) but lower than that in the sham operation group (P = 0.02). The relative expression of ZO-1 in the Lu + GLP group was comparable to that in the sham operation group. The relative expression of CLC-2 descended more obviously in the OJ, GLP-2 and Lu + GLP groups than in the sham operation group (0.195 ± 0.04, 0.217 ± 0.05, 0.222 ± 0.03 vs 0.267 ± 0.04, all P = 0.00).
CONCLUSION: CLC-2 and tight junction protein participate in the maintenance of intestinal mucosal barrier. Acute biliary obstruction-induced destruction of intestinal mucosa barrier is associated with CLC-2 in enterocytes. CLC-2 activation could activate tight junction protein and repair impaired intestinal mucosa barrier.
Collapse
|
15
|
Stauber T, Jentsch TJ. Sorting motifs of the endosomal/lysosomal CLC chloride transporters. J Biol Chem 2010; 285:34537-48. [PMID: 20817731 DOI: 10.1074/jbc.m110.162545] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The CLC protein family contains plasma membrane chloride channels and the intracellular chloride-proton exchangers ClC-3-7. The latter proteins mainly reside on the various compartments of the endosomal-lysosomal system where they are involved in the luminal acidification or chloride accumulation. Although their partially overlapping subcellular distribution has been studied extensively, little is known about their targeting mechanism. In a comprehensive study we now performed pulldown experiments to systematically map the differential binding of adaptor proteins of the endosomal sorting machinery (adaptor proteins and GGAs (Golgi-localized, γ-ear containing, Arf binding)) as well as clathrin to the cytosolic regions of the intracellular CLCs. The resulting interaction pattern fitted well to the known subcellular localizations of the CLCs. By mutating potential sorting motifs, we could locate almost all binding sites, including one already known for ClC-3 and several new motifs for ClC-5, -6, and -7. The impact of the identified binding sites on the subcellular localization of CLC transporters was determined by heterologous expression of mutants. Surprisingly, some vesicular CLCs retained their localization after disruption of interaction sites. However, ClC-7 could be partially shifted from lysosomes to the plasma membrane by combined mutation of N-terminal sorting motifs. The localization of its β-subunit, Ostm1, was determined by that of ClC-7. Ostm1 was not capable of redirecting ClC-7 to lysosomes.
Collapse
Affiliation(s)
- Tobias Stauber
- Leibniz-Institut für Molekulare Pharmakologie and Max-Delbrück-Centrum für Molekulare Medizin, Berlin D-13125, Germany
| | | |
Collapse
|