MLC1 trafficking and membrane expression in astrocytes: role of caveolin-1 and phosphorylation.
Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare congenital leukodystrophy caused by mutations in the MLC1 gene that encodes a membrane protein of unknown function. In the brain MLC1 protein is mainly expressed in astrocyte end-feet, localizes in lipid rafts and associates with the dystrophin glycoprotein complex (DGC). Using pull-down and co-fractionation assays in cultured human and rat astrocytes, we show here that MLC1 intracellular domains pull-down the DGC proteins syntrophin, dystrobrevin, Kir4.1 and caveolin-1, the structural protein of caveolae, thereby supporting a role for DGC and caveolar structures in MLC1 function. By immunostaining and subcellular fractionation of cultured rat or human astrocytes treated with agents modulating caveolin-mediated trafficking, we demonstrate that MLC1 is also expressed in intracellular vesicles and endoplasmic reticulum and undergoes caveolae/raft-mediated endocytosis. Inhibition of endocytosis, cholesterol lowering and protein kinases A- and C-mediated MLC1 phosphorylation favour the expression of membrane-associated MLC1. Because pathological mutations prevent MLC1 membrane expression, the identification of substances regulating MLC1 intracellular trafficking is potentially relevant for the therapy of MLC.
Lanciotti
Angela
A
Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
Brignone
Maria Stefania
MS
Camerini
Serena
S
Serafini
Barbara
B
Macchia
Gianfranco
G
Raggi
Carla
C
Molinari
Paola
P
Crescenzi
Marco
M
Musumeci
Marco
M
Sargiacomo
Massimo
M
Aloisi
Francesca
F
Petrucci
Tamara Corinna
TC
Ambrosini
Elena
E
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000378:metabolism*; D001921:Brain / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D021941:Caveolae / Q000378:metabolism* / Q000648:ultrastructure; D051242:Caveolin 1 / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000378:metabolism / Q000648:ultrastructure; D049028:Dystrophin-Associated Protein Complex / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D056784:Leukoencephalopathies / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D021962:Membrane Microdomains / Q000378:metabolism / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D051381:Rats
D051242:Caveolin 1; D049028:Dystrophin-Associated Protein Complex; C425069:MLC1 protein, human; D008565:Membrane Proteins; D002784:Cholesterol; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C