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Tay–Sachs disease mutations in HEXA target the α chain of hexosaminidase A to endoplasmic reticulum–associated degradation
Loss of function of the enzyme β-hexosaminidase A (HexA) causes the lysosomal storage disorder Tay–Sachs disease (TSD). It has been proposed that mutations in the α chain of HexA can impair folding, enzyme assembly, and/or trafficking, yet there is surprisingly little known about the mechanisms of t...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
The American Society for Cell Biology
2016
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5170605/ https://www.ncbi.nlm.nih.gov/pubmed/27682588 http://dx.doi.org/10.1091/mbc.E16-01-0012 |
Sumario: | Loss of function of the enzyme β-hexosaminidase A (HexA) causes the lysosomal storage disorder Tay–Sachs disease (TSD). It has been proposed that mutations in the α chain of HexA can impair folding, enzyme assembly, and/or trafficking, yet there is surprisingly little known about the mechanisms of these potential routes of pathogenesis. We therefore investigated the biosynthesis and trafficking of TSD-associated HexA α mutants, seeking to identify relevant cellular quality control mechanisms. The α mutants E482K and G269S are defective in enzymatic activity, unprocessed by lysosomal proteases, and exhibit altered folding pathways compared with wild-type α. E482K is more severely misfolded than G269S, as observed by its aggregation and inability to associate with the HexA β chain. Importantly, both mutants are retrotranslocated from the endoplasmic reticulum (ER) to the cytosol and are degraded by the proteasome, indicating that they are cleared via ER-associated degradation (ERAD). Leveraging these discoveries, we observed that manipulating the cellular folding environment or ERAD pathways can alter the kinetics of mutant α degradation. Additionally, growth of patient fibroblasts at a permissive temperature or with chemical chaperones increases cellular Hex activity by improving mutant α folding. Therefore modulation of the ER quality control systems may be a potential therapeutic route for improving some forms of TSD. |
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