The Impairment of TorsinA's Binding to and Interactions With Its Activator: An Atomistic Molecular Dynamics Study of Primary Dystonia

Primary dystonia's prolonged muscle contractions and the associated abnormal postures and twisting movements remain incurable. Genetic mutation/deletion of GAG from TorsonA's gene resulting in Delta E303 (which weakens the binding between TorsinA and its activator, such as LULL1) primarily cause this neurodegenerative disorder. We studied TorsinA-LULL1 (or TorsinA Delta E303-LULL1) bindings and interactions. For the first time, we show the atomic details of TorsinA-LULL1 dynamic interactions and TorsinA Delta E303-LULL1 dynamic interactions and their binding affinities. Our results show extensive effects of Delta E303 on TorsinA Delta E303-LULL1 interactions, and suggest that the differences between TorsinA-LULL1 interactions and TorsinA Delta E303-LULL1 interactions are non-subtle. Delta E303 significantly weakens TorsinA Delta E303-LULL1's binding affinity. We present pieces of evidence proving that the effects of Delta E303 (on the differences between TorsinA-LULL1 interactions and TorsinA Delta E303-LULL1 interactions) are more pronounced than previously suggested, and that the nanobody used for achieving the X-ray crystallization in the previous study attenuated the differences between TorsinA-LULL1 and TorsinA Delta E303-LULL1 interactions. Our accounts of the dynamic interactions between TorsinA and LULL1 and between TorsinA Delta E303 and LULL1 and the detailed effects of Delta E303 on TorsinA-/TorsinA Delta E303-LULL1 build on previous findings and offer new insights for a better understanding of the molecular basis of Primary Dystonia. Our results have long-term potentials of guiding the development of medications for the disease.