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Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy

Early/late endosomes, recycling endosomes, and lysosomes together form the endo-lysosomal recycling pathway. This system plays a crucial role in cell differentiation and survival, and dysregulation of the endo-lysosomal system appears to be important in the pathogenesis of neurodevelopmental and neu...

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Autores principales: Guzman, Raul E., Sierra-Marquez, Juan, Bungert-Plümke, Stefanie, Franzen, Arne, Fahlke, Christoph
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9198718/
https://www.ncbi.nlm.nih.gov/pubmed/35721313
http://dx.doi.org/10.3389/fnmol.2022.872407
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author Guzman, Raul E.
Sierra-Marquez, Juan
Bungert-Plümke, Stefanie
Franzen, Arne
Fahlke, Christoph
author_facet Guzman, Raul E.
Sierra-Marquez, Juan
Bungert-Plümke, Stefanie
Franzen, Arne
Fahlke, Christoph
author_sort Guzman, Raul E.
collection PubMed
description Early/late endosomes, recycling endosomes, and lysosomes together form the endo-lysosomal recycling pathway. This system plays a crucial role in cell differentiation and survival, and dysregulation of the endo-lysosomal system appears to be important in the pathogenesis of neurodevelopmental and neurodegenerative diseases. Each endo-lysosomal compartment fulfils a specific function, which is supported by ion transporters and channels that modify ion concentrations and electrical gradients across endo-lysosomal membranes. CLC-type Cl(–)/H(+) exchangers are a group of endo-lysosomal transporters that are assumed to regulate luminal acidification and chloride concentration in multiple endosomal compartments. Heterodimers of ClC-3 and ClC-4 localize to various internal membranes, from the endoplasmic reticulum and Golgi to recycling endosomes and late endosomes/lysosomes. The importance of ClC-4-mediated ion transport is illustrated by the association of naturally occurring CLCN4 mutations with epileptic encephalopathy, intellectual disability, and behavioral disorders in human patients. However, how these mutations affect the expression, subcellular localization, and function of ClC-4 is insufficiently understood. We here studied 12 CLCN4 variants that were identified in patients with X-linked intellectual disability and epilepsy and were already characterized to some extent in earlier work. We analyzed the consequences of these mutations on ClC-4 ion transport, subcellular trafficking, and heterodimerization with ClC-3 using heterologous expression in mammalian cells, biochemistry, confocal imaging, and whole-cell patch-clamp recordings. The mutations led to a variety of changes in ClC-4 function, ranging from gain/loss of function and impaired heterodimerization with ClC-3 to subtle impairments in transport functions. Our results suggest that even slight functional changes to the endosomal Cl(–)/H(+) exchangers can cause serious neurological symptoms.
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spelling pubmed-91987182022-06-16 Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy Guzman, Raul E. Sierra-Marquez, Juan Bungert-Plümke, Stefanie Franzen, Arne Fahlke, Christoph Front Mol Neurosci Neuroscience Early/late endosomes, recycling endosomes, and lysosomes together form the endo-lysosomal recycling pathway. This system plays a crucial role in cell differentiation and survival, and dysregulation of the endo-lysosomal system appears to be important in the pathogenesis of neurodevelopmental and neurodegenerative diseases. Each endo-lysosomal compartment fulfils a specific function, which is supported by ion transporters and channels that modify ion concentrations and electrical gradients across endo-lysosomal membranes. CLC-type Cl(–)/H(+) exchangers are a group of endo-lysosomal transporters that are assumed to regulate luminal acidification and chloride concentration in multiple endosomal compartments. Heterodimers of ClC-3 and ClC-4 localize to various internal membranes, from the endoplasmic reticulum and Golgi to recycling endosomes and late endosomes/lysosomes. The importance of ClC-4-mediated ion transport is illustrated by the association of naturally occurring CLCN4 mutations with epileptic encephalopathy, intellectual disability, and behavioral disorders in human patients. However, how these mutations affect the expression, subcellular localization, and function of ClC-4 is insufficiently understood. We here studied 12 CLCN4 variants that were identified in patients with X-linked intellectual disability and epilepsy and were already characterized to some extent in earlier work. We analyzed the consequences of these mutations on ClC-4 ion transport, subcellular trafficking, and heterodimerization with ClC-3 using heterologous expression in mammalian cells, biochemistry, confocal imaging, and whole-cell patch-clamp recordings. The mutations led to a variety of changes in ClC-4 function, ranging from gain/loss of function and impaired heterodimerization with ClC-3 to subtle impairments in transport functions. Our results suggest that even slight functional changes to the endosomal Cl(–)/H(+) exchangers can cause serious neurological symptoms. Frontiers Media S.A. 2022-05-31 /pmc/articles/PMC9198718/ /pubmed/35721313 http://dx.doi.org/10.3389/fnmol.2022.872407 Text en Copyright © 2022 Guzman, Sierra-Marquez, Bungert-Plümke, Franzen and Fahlke. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Neuroscience
Guzman, Raul E.
Sierra-Marquez, Juan
Bungert-Plümke, Stefanie
Franzen, Arne
Fahlke, Christoph
Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy
title Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy
title_full Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy
title_fullStr Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy
title_full_unstemmed Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy
title_short Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy
title_sort functional characterization of clcn4 variants associated with x-linked intellectual disability and epilepsy
topic Neuroscience
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9198718/
https://www.ncbi.nlm.nih.gov/pubmed/35721313
http://dx.doi.org/10.3389/fnmol.2022.872407
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