Cryo-EM structure of AAA + ATPase thorase reveals novel helical filament formation

Mohamad Aasif Dar; Robert Louder; Marisol Cortes; Rong Chen; Qianqian Ma; Mayukh Chakrabarti; George K E Umanah; Ted M Dawson; Valina L Dawson

doi:10.1016/j.csbj.2025.05.018

Cryo-EM structure of AAA + ATPase thorase reveals novel helical filament formation

Comput Struct Biotechnol J. 2025 May 23:27:2186-2198. doi: 10.1016/j.csbj.2025.05.018. eCollection 2025.

Authors

Mohamad Aasif Dar^{1

2}, Robert Louder³, Marisol Cortes^{1

2}, Rong Chen^{1

2}, Qianqian Ma⁴, Mayukh Chakrabarti⁵, George K E Umanah^{1

2}, Ted M Dawson^{1

2

6

7}, Valina L Dawson^{1

2

6

7

8}

Affiliations

¹ Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, United States.
² Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States.
³ Department of Molecular Biology & Genetics, The Johns Hopkins University School of Medicine, Baltimore, MD, United States.
⁴ Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD, United States.
⁵ Department of Biophysics and Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD, United States.
⁶ Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD, United States.
⁷ Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, United States.
⁸ Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States.

Abstract

The AAA+ (ATPases associated with a variety of cellular activities) ATPase, Thorase, also known as ATAD1, plays multiple roles in synaptic plasticity, mitochondrial quality control and mTOR signaling through disassembling protein complexes like AMPAR and mTORC1 in an ATP-dependent manner. The Oligomerization of Thorase is crucial for its disassembly and remodeling functions. We show that wild-type Thorase forms long helical filaments in vitro, dependent on ATP binding but not hydrolysis. We report the Cryogenic Electron Microscopy (cryo-EM) structure of the Thorase filament at a resolution of 4 Å, revealing the dimeric arrangement of the basic repeating unit that is formed through a distinct interface compared to the hexameric MSP1/Thorase E193Q assembly. Structure-guided mutagenesis confirms the role of critical amino acid residues required for filament formation, oligomerization and disassembly of mTORC1 protein complex. Together, our data reveal a new filament structure of Thorase, offering insights into the mechanism of Thorase filament formation and its potential role in the disassembly of the mTORC1 complex.

Keywords: Cryo-Electron microscopy; Disassembly; Mutagenesis; Oligomerization.