Title : The role of N-glycosylation in folding, trafficking, and functionality of lysosomal
protein CLN5 CLN5
Abstract :
- CLN5 is a soluble lysosomal protein with unknown function
- Mutations in CLN5 lead to neuronal ceroid lipofuscinosis, a group of inherited neurodegenerative disorders that mainly affect children
- CLN5 has eight potential N-glycosylation sites based on the Asn-X-Thr/Ser consensus sequence
- Through site-directed mutagenesis of individual asparagine residues to glutamine on each of the N-glycosylation consensus sites , we showed that all eight putative N-glycosylation sites are utilized in vivo
- Additionally , localization studies showed that the lack of N-glycosylation on certain sites ( N179, N252, N304 , or N320 ) caused CLN5 retention in the endoplasmic reticulum, indicating that glycosylation is important for protein folding
- Interestingly, one particular mutant, N401Q, is mislocalized to the Golgi, suggesting that N401 is not important for protein folding but essential for CLN5 trafficking to the lysosome
- Finally , we analyzed several patient mutations in which N-glycosylation is affected
- The N192S patient mutant is localized to the lysosome, indicating that this mutant has a functional defect in the lysosome
- Our results suggest that there are functional differences in various N-glycosylation sites of CLN5 which affect folding, trafficking, and lysosomal function of CLN5