Marazza, Alessandro Galli, Carmela Fasana, Elisa Sgrignani, Jacopo Burda, Patricie Enrico M. A. Fassi Matthias Baumgartner Andrea Cavalli Maurizio Molinari 2019 Hunter’s syndrome (mucopolysaccharidosis type II) is a rare X-linked lysosomal storage disorder caused by mutations in the iduronate 2-sulfatase (IDS) gene. Motivated by the case of a child affected by this syndrome, we compared the intracellular fate of wild type IDS (IDSWT) and of four nonsense mutations of IDS (IDSL482X, IDSY452X, IDSR443X and IDSW337X) generating progressively shorter forms of IDS associated with mild to severe forms of the disease. Our analyses revealed formylation of all forms of IDS at cysteine 84, which is a pre-requisite for enzymatic activity. After formylation, IDSWT was transported within lysosomes, where it was processed in the mature form of the enzyme. The length of disease-causing deletions correlated with gravity of the folding and transport phenotype, which was anticipated by molecular dynamics analyses. The shortest form of IDS, IDSW337X, was retained in the endoplasmic reticulum (ER) and degraded by the ubiquitin-proteasome system. IDSR443X, IDSY452X, IDSL482X passed ER quality control, were transported to the lysosomes, but failed lysosomal quality control resulting in their rapid clearance and in loss-of-function phenotype. Failure of ER quality control inspection is an established cause of loss-of-function observed in protein misfolding diseases. Our data reveal that fulfillment of ER requirements might not be sufficient, highlight lysosomal quality control as the distal station to control lysosomal enzymes fitness and pave the way for alternative therapeutic interventions. application/pdf https://n2t.net/ark:/12658/srd1319181 https://susi.usi.ch/global/documents/319181 https://susi.usi.ch/documents/319181/files/Marazza_preprint_2019.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1089/dna.2019.5221 info:eu-repo/semantics/altIdentifier/ark/12658/srd1319181 info:eu-repo/semantics/openAccess License undefined Endoplasmic reticulum Formylation Glycosaminoglycans Hunter’s disease Iduronate-2 sulfatase Nonsense mutations Lysosomal storage diseases Lysosome Molecular dynamics Mucopolysaccharidosis type II info:eu-repo/classification/udc/57 Endoplasmic reticulum and lysosomal quality control of four nonsense mutants of iduronate 2-sulfatase linked to Hunter’s syndrome http://purl.org/coar/resource_type/c_816b