Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 298, Issue 1, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.jbc.2021.101438
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Funding
- Spastic Paraplegia Foundation
- Cellular, Biochemical, and Molecular Sciences (CMB) Predoctoral Training Grant Program from the NIH
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Hereditary spastic paraplegia (HSP) is a group of neuropathies that affect upper motor neurons and cause progressive gait disorder. Mutations in the gene SPG3A/atlastin-1 (ATL1), which encodes a dynamin superfamily member involved in membrane tethering and fusion, account for approximately 10% of HSP cases. This study reports a novel disease-causing insertion mutation in the ATL1 gene, leading to severe quadriplegia, dystonia, and thinning of the corpus callosum. The mutation affects a region in the protein vital for intramolecular interactions and conformational changes driven by GTP hydrolysis.
Hereditary spastic paraplegia (HSP) comprises a heterogeneous group of neuropathies affecting upper motor neurons and causing progressive gait disorder. Mutations in the gene SPG3A/atlastin-1 (ATL1), encoding a dynamin superfamily member, which utilizes the energy from GTP hydrolysis for membrane tethering and fusion to promote the formation of a highly branched, smooth endoplasmic reticulum (ER), account for approximately 10% of all HSP cases. The continued discovery and characterization of novel disease mutations are crucial for our understanding of HSP pathogenesis and potential treatments. Here, we report a novel disease-causing, in frame insertion in the ATL1 gene, leading to inclusion of an additional asparagine residue at position 417 (N417ins). This mutation correlates with complex, early-onset spastic quadriplegia affecting all four extremities, generalized dystonia, and a thinning of the corpus callosum. We show using limited proteolysis and FRET-based studies that this novel insertion affects a region in the protein central to intramolecular interactions and GTPase-driven conformational change, and that this insertion mutation is associated with an aberrant prehydrolysis state. While GTPase activity remains unaffected by the insertion, membrane tethering is increased, indicative of a gain-of-function disease mechanism uncommon for ATL1associated pathologies. In conclusion, our results identify a novel insertion mutation with altered membrane tethering activity that is associated with spastic quadriplegia, potentially uncovering a broad spectrum of molecular mechanisms that may affect neuronal function.
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