Analyses of disease-related GNPTAB mutations define a novel GlcNAc-1-phosphotransferase interaction domain and an alternative site-1 protease cleavage site
Abstract
Mucolipidosis II (MLII) and III alpha/beta are autosomal-recessive diseases of childhood caused by mutations in GNPTAB encoding the α/β-subunit precursor protein of the GlcNAc-1-phosphotransferase complex. This enzyme modifies lysosomal hydrolases with mannose 6-phosphate targeting signals. Upon arrival in the Golgi apparatus, the newly synthesized α/β-subunit precursor is catalytically activated by site-1 protease (S1P). Here we performed comprehensive expression studies of GNPTAB mutations, including two novel mutations T644M and T1223del, identified in Brazilian MLII/MLIII alpha/beta patients. We show that the frameshift E757KfsX1 and the non-sense R587X mutations result in the retention of enzymatically inactive truncated precursor proteins in the endoplasmic reticulum (ER) due to loss of cytosolic ER exit motifs consistent with a severe clinical phenotype in homozygosity. The luminal missense mutations, C505Y, G575R and T644M, partially impaired ER exit and proteolytic activation in accordance with less severe MLIII alpha/beta disease symptoms. Analogous to the previously characterized S399F mutant, we found that the missense mutation I403T led to retention in the ER and loss of catalytic activity. Substitution of further ...Continue Reading
References
Mucolipidosis II is caused by mutations in GNPTA encoding the alpha/beta GlcNAc-1-phosphotransferase
Citations
Datasets Mentioned
Methods Mentioned
Software Mentioned
Related Concepts
Related Feeds
Alzheimer's Disease: APP
Amyloid precursor protein (APP) proteolysis is critical for the development of Alzheimer's disease, a neurodegenerative disease associated with accumulation of amyloid plaques in the brain. Here is the latest research on APP and Alzheimer's disease.