title: Insights into MLC pathogenesis: GlialCAM is an MLC1 chaperone required for proper activation of volume-regulated anion currents.
abstract: Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare type of leukodystrophy caused by mutations in either MLC1 or GLIALCAM genes and is associated with myelin and astrocyte vacuolation. It has been suggested that MLC is caused by impaired cell volume regulation as a result of defective activation of astrocytic volume-regulated anion currents (VRAC). GlialCAM brings MLC1 and the ClC-2 Cl(-) channel to cell-cell junctions, even though the role of ClC-2 in MLC disease remains incompletely understood. To gain insights into the biological role of GlialCAM in the pathogenesis of MLC disease, here we analyzed the gain- and loss-of-function phenotypes of GlialCAM in Hela cells and primary astrocytes, focusing on its interaction with the MLC1 protein. Unexpectedly, GlialCAM ablation provoked intracellular accumulation and reduced expression of MLC1 at the plasma membrane. Conversely, over-expression of GlialCAM increased the cellular stability of mutant MLC1 variants. Reduction in GlialCAM expression resulted in defective activation of VRAC and augmented vacuolation, phenocopying MLC1 mutations. Importantly, over-expression of GlialCAM together with MLC1 containing MLC-related mutations was able to reactivate VRAC currents and to reverse the vacuolation caused in the presence of mutant MLC1. These results indicate a previously unrecognized role of GlialCAM in facilitating the biosynthetic maturation and cell surface expression of MLC1, and suggest that pharmacological strategies aimed to increase surface expression of MLC1 and/or VRAC activity may be beneficial for MLC patients.
authors.affiliation: Sección de Fisiología, Departamento de Ciencias Fisiológicas II and.
authors.forename: Xavier
authors.initials: X
authors.lastname: Capdevila-Nortes
authors.forename: Tania
authors.initials: T
authors.lastname: López-Hernández
authors.forename: Pirjo M
authors.initials: PM
authors.lastname: Apaja
authors.forename: Miguel
authors.initials: M
authors.lastname: López de Heredia
authors.forename: Sònia
authors.initials: S
authors.lastname: Sirisi
authors.forename: Gerard
authors.initials: G
authors.lastname: Callejo
authors.forename: Tanit
authors.initials: T
authors.lastname: Arnedo
authors.forename: Virginia
authors.initials: V
authors.lastname: Nunes
authors.forename: Gergely L
authors.initials: GL
authors.lastname: Lukacs
authors.forename: Xavier
authors.initials: X
authors.lastname: Gasull
authors.forename: Raúl
authors.initials: R
authors.lastname: Estévez
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000502:physiology* / Q000648:ultrastructure; D000090007:CLC-2 Chloride Channels; D018797:Cell Cycle Proteins; D018118:Chloride Channels / Q000502:physiology*; D003560:Cysts / Q000235:genetics / Q000503:physiopathology*; D014644:Genetic Variation; D006367:HeLa Cells; D020279:Hereditary Central Nervous System Demyelinating Diseases / Q000235:genetics / Q000503:physiopathology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D055550:Protein Stability; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D014617:Vacuoles / Q000502:physiology
chemical_list: D000090007:CLC-2 Chloride Channels; D018797:Cell Cycle Proteins; D018118:Chloride Channels; C487620:HEPACAM protein, human; C425069:MLC1 protein, human; D008565:Membrane Proteins; D018832:Molecular Chaperones; D011506:Proteins