Impaired Autophagic Clearance with a Gain-of-Function Variant of the Lysosomal Cl<sup>−</sup>/H<sup>+</sup> Exchanger ClC-7
ClC-7 is a ubiquitously expressed voltage-gated Cl<sup>−</sup>/H<sup>+</sup> exchanger that critically contributes to lysosomal ion homeostasis. Together with its β-subunit Ostm1, ClC-7 localizes to lysosomes and to the ruffled border of osteoclasts, where it supports the aci...
| Main Authors: | , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2023-12-01
|
| Series: | Biomolecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2218-273X/13/12/1799 |
| _version_ | 1827575501358628864 |
|---|---|
| author | Shroddha Bose Cecilia de Heus Mary E. Kennedy Fan Wang Thomas J. Jentsch Judith Klumperman Tobias Stauber |
| author_facet | Shroddha Bose Cecilia de Heus Mary E. Kennedy Fan Wang Thomas J. Jentsch Judith Klumperman Tobias Stauber |
| author_sort | Shroddha Bose |
| collection | DOAJ |
| description | ClC-7 is a ubiquitously expressed voltage-gated Cl<sup>−</sup>/H<sup>+</sup> exchanger that critically contributes to lysosomal ion homeostasis. Together with its β-subunit Ostm1, ClC-7 localizes to lysosomes and to the ruffled border of osteoclasts, where it supports the acidification of the resorption lacuna. Loss of ClC-7 or Ostm1 leads to osteopetrosis accompanied by accumulation of storage material in lysosomes and neurodegeneration. Interestingly, not all osteopetrosis-causing <i>CLCN7</i> mutations from patients are associated with a loss of ion transport. Some rather result in an acceleration of voltage-dependent ClC-7 activation. Recently, a gain-of-function variant, ClC-7<sup>Y715C</sup>, that yields larger ion currents upon heterologous expression, was identified in two patients with neurodegeneration, organomegaly and albinism. However, neither the patients nor a mouse model that carried the equivalent mutation developed osteopetrosis, although expression of ClC-7<sup>Y715C</sup> induced the formation of enlarged intracellular vacuoles. Here, we investigated how, in transfected cells with mutant ClC-7, the substitution of this tyrosine impinged on the morphology and function of lysosomes. Combinations of the tyrosine mutation with mutations that either uncouple Cl<sup>−</sup> from H<sup>+</sup> counter-transport or strongly diminish overall ion currents were used to show that increased ClC-7 Cl<sup>−</sup>/H<sup>+</sup> exchange activity is required for the formation of enlarged vacuoles by membrane fusion. Degradation of endocytosed material was reduced in these compartments and resulted in an accumulation of lysosomal storage material. In cells expressing the ClC-7 gain-of-function mutant, autophagic clearance was largely impaired, resulting in a build-up of autophagic material. |
| first_indexed | 2024-03-08T20:58:00Z |
| format | Article |
| id | doaj.art-b5fbd09b5fc84cbca5cf5b70335ee837 |
| institution | Directory Open Access Journal |
| issn | 2218-273X |
| language | English |
| last_indexed | 2024-03-08T20:58:00Z |
| publishDate | 2023-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Biomolecules |
| spelling | doaj.art-b5fbd09b5fc84cbca5cf5b70335ee8372023-12-22T13:56:09ZengMDPI AGBiomolecules2218-273X2023-12-011312179910.3390/biom13121799Impaired Autophagic Clearance with a Gain-of-Function Variant of the Lysosomal Cl<sup>−</sup>/H<sup>+</sup> Exchanger ClC-7Shroddha Bose0Cecilia de Heus1Mary E. Kennedy2Fan Wang3Thomas J. Jentsch4Judith Klumperman5Tobias Stauber6Institute for Molecular Medicine, MSH Medical School Hamburg, 20457 Hamburg, GermanyCenter for Molecular Medicine/Cell Biology, University Medical Center (UMC), 3584 CX Utrecht, The NetherlandsInstitute of Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, GermanyInstitute for Molecular Medicine, MSH Medical School Hamburg, 20457 Hamburg, GermanyLeibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, GermanyCenter for Molecular Medicine/Cell Biology, University Medical Center (UMC), 3584 CX Utrecht, The NetherlandsInstitute for Molecular Medicine, MSH Medical School Hamburg, 20457 Hamburg, GermanyClC-7 is a ubiquitously expressed voltage-gated Cl<sup>−</sup>/H<sup>+</sup> exchanger that critically contributes to lysosomal ion homeostasis. Together with its β-subunit Ostm1, ClC-7 localizes to lysosomes and to the ruffled border of osteoclasts, where it supports the acidification of the resorption lacuna. Loss of ClC-7 or Ostm1 leads to osteopetrosis accompanied by accumulation of storage material in lysosomes and neurodegeneration. Interestingly, not all osteopetrosis-causing <i>CLCN7</i> mutations from patients are associated with a loss of ion transport. Some rather result in an acceleration of voltage-dependent ClC-7 activation. Recently, a gain-of-function variant, ClC-7<sup>Y715C</sup>, that yields larger ion currents upon heterologous expression, was identified in two patients with neurodegeneration, organomegaly and albinism. However, neither the patients nor a mouse model that carried the equivalent mutation developed osteopetrosis, although expression of ClC-7<sup>Y715C</sup> induced the formation of enlarged intracellular vacuoles. Here, we investigated how, in transfected cells with mutant ClC-7, the substitution of this tyrosine impinged on the morphology and function of lysosomes. Combinations of the tyrosine mutation with mutations that either uncouple Cl<sup>−</sup> from H<sup>+</sup> counter-transport or strongly diminish overall ion currents were used to show that increased ClC-7 Cl<sup>−</sup>/H<sup>+</sup> exchange activity is required for the formation of enlarged vacuoles by membrane fusion. Degradation of endocytosed material was reduced in these compartments and resulted in an accumulation of lysosomal storage material. In cells expressing the ClC-7 gain-of-function mutant, autophagic clearance was largely impaired, resulting in a build-up of autophagic material.https://www.mdpi.com/2218-273X/13/12/1799autophagychloride/proton exchangeClC-7endo-lysosomeslysosomal storage disorderosmotic pressure |
| spellingShingle | Shroddha Bose Cecilia de Heus Mary E. Kennedy Fan Wang Thomas J. Jentsch Judith Klumperman Tobias Stauber Impaired Autophagic Clearance with a Gain-of-Function Variant of the Lysosomal Cl<sup>−</sup>/H<sup>+</sup> Exchanger ClC-7 Biomolecules autophagy chloride/proton exchange ClC-7 endo-lysosomes lysosomal storage disorder osmotic pressure |
| title | Impaired Autophagic Clearance with a Gain-of-Function Variant of the Lysosomal Cl<sup>−</sup>/H<sup>+</sup> Exchanger ClC-7 |
| title_full | Impaired Autophagic Clearance with a Gain-of-Function Variant of the Lysosomal Cl<sup>−</sup>/H<sup>+</sup> Exchanger ClC-7 |
| title_fullStr | Impaired Autophagic Clearance with a Gain-of-Function Variant of the Lysosomal Cl<sup>−</sup>/H<sup>+</sup> Exchanger ClC-7 |
| title_full_unstemmed | Impaired Autophagic Clearance with a Gain-of-Function Variant of the Lysosomal Cl<sup>−</sup>/H<sup>+</sup> Exchanger ClC-7 |
| title_short | Impaired Autophagic Clearance with a Gain-of-Function Variant of the Lysosomal Cl<sup>−</sup>/H<sup>+</sup> Exchanger ClC-7 |
| title_sort | impaired autophagic clearance with a gain of function variant of the lysosomal cl sup sup h sup sup exchanger clc 7 |
| topic | autophagy chloride/proton exchange ClC-7 endo-lysosomes lysosomal storage disorder osmotic pressure |
| url | https://www.mdpi.com/2218-273X/13/12/1799 |
| work_keys_str_mv | AT shroddhabose impairedautophagicclearancewithagainoffunctionvariantofthelysosomalclsupsuphsupsupexchangerclc7 AT ceciliadeheus impairedautophagicclearancewithagainoffunctionvariantofthelysosomalclsupsuphsupsupexchangerclc7 AT maryekennedy impairedautophagicclearancewithagainoffunctionvariantofthelysosomalclsupsuphsupsupexchangerclc7 AT fanwang impairedautophagicclearancewithagainoffunctionvariantofthelysosomalclsupsuphsupsupexchangerclc7 AT thomasjjentsch impairedautophagicclearancewithagainoffunctionvariantofthelysosomalclsupsuphsupsupexchangerclc7 AT judithklumperman impairedautophagicclearancewithagainoffunctionvariantofthelysosomalclsupsuphsupsupexchangerclc7 AT tobiasstauber impairedautophagicclearancewithagainoffunctionvariantofthelysosomalclsupsuphsupsupexchangerclc7 |