title: Mucolipidosis II is caused by mutations in GNPTA encoding the alpha/beta GlcNAc-1-phosphotransferase.
abstract: Mucolipidosis II (ML II) is a fatal lysosomal storage disorder resulting from defects in the multimeric GlcNAc-1-phosphotransferase responsible for the initial step in the generation of the mannose 6-phosphate (M6P) recognition marker. M6P residues on oligosaccharides of newly synthesized lysosomal enzymes are essential for efficient receptor-mediated transport to lysosomes. We used the recombinant GlcNAc-1-phosphotransferase gamma subunit as an affinity matrix to purify an unknown protein identified as the product of GNPTA (encoding GNPTA, previously known as MGC4170). The cDNA encodes a protein of 1,256 amino acids with two putative transmembrane domains and a complex preserved modular structure comprising at least six domains. The N-terminal domain of GNPTA, interrupted by a long insertion, shows similarities to bacterial capsule biosynthesis proteins. We identified seven mutations in GNPTA that lead to premature translational termination in six individuals with ML II. Retroviral transduction of fibroblasts from an individual with ML II resulted in the expression and localization of GNPTA in the Golgi apparatus, accompanied by the correction of hypersecretion of lysosomal enzymes. Our results provide evidence that GNPTA encodes a subunit of GlcNAc-1-phosphotransferase defective in individuals with ML II.
authors.affiliation: Department of Biochemistry, Children's Hospital, University of Hamburg, Martinistr. 52, 20246 Hamburg, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Tiede
authors.forename: Stephan
authors.initials: S
authors.lastname: Storch
authors.forename: Torben
authors.initials: T
authors.lastname: Lübke
authors.forename: Bernard
authors.initials: B
authors.lastname: Henrissat
authors.forename: Ruth
authors.initials: R
authors.lastname: Bargal
authors.forename: Annick
authors.initials: A
authors.lastname: Raas-Rothschild
authors.forename: Thomas
authors.initials: T
authors.lastname: Braulke
mesh_terms: D000595:Amino Acid Sequence; D005347:Fibroblasts; D006801:Humans; D008969:Molecular Sequence Data; D009081:Mucolipidoses / Q000201:enzymology / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D017855:Transferases (Other Substituted Phosphate Groups) / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D017855:Transferases (Other Substituted Phosphate Groups); C505859:alpha-beta GlcNAc-1-phosphotransferase, human