GNPTAB missense mutations cause loss of GlcNAc-1-phosphotransferase activity in mucolipidosis type II through distinct mechanisms.

5 years ago

GNPTAB missense mutations cause loss of GlcNAc-1-phosphotransferase activity in mucolipidosis type II through distinct mechanisms.

Sperb-Ludwig F, Braulke T, Lourenço CM, Schwartz IVD, Gandelman Horovitz DD, Kim C, Ludwig NF, Rodovalho-Doriqui MJ, Acosta AX, Velho RV, Ribeiro EM, Santos ES, Boy R, Pohl S

Mucolipidoses (ML) II and III alpha/beta are lysosomal storage diseases caused by pathogenic mutations in GNPTAB encoding the α⁄β-subunit precursor of GlcNAc-1-phosphotransferase. To determine genotype-phenotype correlation and functional analysis of mutant GlcNAc-1-phosphotransferase, 13 Brazilian patients clinically and biochemical diagnosed for MLII or III alpha/beta were studied. By sequencing of genomic GNPTAB of the MLII and MLIII alpha/beta patients we identified six novel mutations: p.D76G, p.S385L, p.Q278Kfs*3, p.H588Qfs*27, p.N642Lfs*10 and p.Y1111*. Expression analysis by western blotting and immunofluorescence microscopy revealed that the mutant α⁄β-subunit precursor p.D76G is retained in the endoplasmic reticulum whereas the mutant p.S385L is correctly transported to the cis-Golgi apparatus and proteolytically processed. Both mutations lead to complete loss of GlcNAc-1-phosphotransferase activity, consistent with the severe clinical MLII phenotype of the patients. Our study expands the genotypic spectrum of MLII and provides novel insights into structural requirements to ensure GlcNAc-1-phosphotransferase activity.

Publisher URL: https://www.ncbi.nlm.nih.gov/pubmed/28918368

DOI: PubMed:28918368