Two di-leucine motifs regulate trafficking of mucolipin-1 to lysosomes.
Mutations in the mucolipin-1 gene have been linked to mucolipidosis type IV, a lysosomal storage disorder characterized by severe neurological and ophthalmologic abnormalities. Mucolipin-1 is a membrane protein containing six putative transmembrane domains with both its N- and C-termini localized facing the cytosol. To gain information on the sorting motifs that mediate the trafficking of this protein to lysosomes, we have generated chimeras in which the N- and C- terminal tail portions of mucolipin-1 were fused to a reporter gene. In this article, we report the identification of two separate di-leucine-type motifs that co-operate to regulate the transport of mucolipin-1 to lysosomes. One di-leucine motif is positioned at the N-terminal cytosolic tail and mediates direct transport to lysosomes, whereas the other di-leucine motif is found at the C-terminal tail and functions as an adaptor protein 2-dependent internalization motif. We have also found that the C-terminal tail of mucolipin-1 is palmitoylated and that this modification might regulate the efficiency of endocytosis. Finally, the mutagenesis of both di-leucine motifs abrogated lysosomal accumulation and resulted in cell-surface redistribution of mucolipin-1. Taken together, these results reveal novel information regarding the motifs that regulate mucolipin-1 trafficking and suggest a role for palmitoylation in protein sorting.
Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Silvia
S
Vergarajauregui
Rosa
R
Puertollano
D000409:Alanine / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D003545:Cysteine / Q000737:chemistry; D003600:Cytosol / Q000378:metabolism; D004705:Endocytosis; D019084:Fluorescent Antibody Technique, Indirect; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007930:Leucine / Q000737:chemistry*; D008247:Lysosomes / Q000378:metabolism*; D018613:Microscopy, Confocal; D008956:Models, Chemical; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019308:Palmitic Acid / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D050053:TRPM Cation Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050051:Transient Receptor Potential Channels
C416674:MCOLN1 protein, human; D011994:Recombinant Proteins; D050053:TRPM Cation Channels; D050051:Transient Receptor Potential Channels; D049452:Green Fluorescent Proteins; D019308:Palmitic Acid; D007930:Leucine; D003545:Cysteine; D000409:Alanine