| Functional aspect | Key findings | Evidence type | Key sources with year + DOI URL |
|---|---|---|---|
| Gene/protein identity | Human **ATAD1** = **Thorase**, ortholog of yeast **Msp1**; UniProt Q8NBU5. Literature consistently matches a membrane-anchored AAA+ ATPase/extractase rather than an unrelated gene symbol. Belongs to the MSP1 subfamily and functions in outer mitochondrial membrane protein quality control (pqac-00000000, pqac-00000002, pqac-00000005) | Review, structure, database-aligned annotation | Wang & Walter 2020, doi: https://doi.org/10.1146/annurev-cellbio-031220-015840; Wang et al. 2022, doi: https://doi.org/10.7554/elife.73941 |
| Localization | ATAD1 is anchored by a single N-terminal transmembrane helix in the **outer mitochondrial membrane (OMM)** with the AAA domain exposed to the cytosol; several sources also note localization/function at **peroxisomes** for tail-anchored protein proofreading (pqac-00000000, pqac-00000001, pqac-00000004) | Review, cell biology, structural interpretation | Wang & Walter 2020, doi: https://doi.org/10.1146/annurev-cellbio-031220-015840; Chen et al. 2014, doi: https://doi.org/10.15252/embj.201487943 |
| Domain/oligomeric architecture | Human ATAD1 is a **hexameric AAA+ ATPase** that forms a right-handed spiral/lock-washer assembly during substrate engagement. Conserved pore loops and a C-terminal helix adapt it for membrane protein extraction (pqac-00000005, pqac-00000021, pqac-00000022) | Cryo-EM structure, mutagenesis | Wang et al. 2022, doi: https://doi.org/10.7554/elife.73941; Wang et al. 2020, doi: https://doi.org/10.7554/elife.54031 |
| Primary molecular activity | ATAD1 is an **ATP-driven membrane protein extractase/translocase** that removes mislocalized membrane proteins and proteins stalled in the mitochondrial import machinery; ATP hydrolysis is required for direct substrate removal from membranes (pqac-00000000, pqac-00000003, pqac-00000007) | Review, biochemical reconstitution, cell biology | Wang & Walter 2020, doi: https://doi.org/10.1146/annurev-cellbio-031220-015840; Winter et al. 2022, doi: https://doi.org/10.7554/elife.82860 |
| Foundational substrate class: mistargeted tail-anchored proteins | The founding quality-control role is extraction of **mislocalized tail-anchored (TA) proteins** from mitochondria. In yeast, Pex15 and Gos1 are canonical substrates; mammalian conservation is supported by increased mitochondrial localization of **PEX26** and **GOS28** after ATAD1 depletion/knockdown (pqac-00000009, pqac-00000011, pqac-00000013) | Genetics, substrate-trap biochemistry, microscopy | Chen et al. 2014, doi: https://doi.org/10.15252/embj.201487943 |
| Proofreading/rerouting pathway | Msp1/ATAD1-dependent extraction can **reroute mislocalized TA proteins from mitochondria to the ER** via the **GET/TRC pathway**, establishing an intracellular proofreading system rather than simple destruction in all cases (pqac-00000008, pqac-00000014, pqac-00000020) | Time-lapse imaging, co-IP, review | Matsumoto et al. 2019, doi: https://doi.org/10.1016/j.molcel.2019.07.006; Matsumoto 2023, doi: https://doi.org/10.1093/jb/mvad025 |
| Degradation pathway coupling | For some substrates, extraction precedes **ubiquitination and proteasomal degradation**; evidence places Msp1/ATAD1 upstream of ubiquitin-dependent Cdc48/proteasome clearance for mislocalized TA substrates (pqac-00000010) | Genetics, inhibitor studies, biochemistry | Matsumoto 2023, doi: https://doi.org/10.1093/jb/mvad025 |
| Import-stress / translocase quality control | Beyond TA proteins, ATAD1/Msp1 extracts **stuck import substrates** from the mitochondrial outer membrane/translocase system, helping maintain mitochondrial protein import capacity and linking the protein to mitoCPR/import-stress pathways (pqac-00000000, pqac-00000005, pqac-00000015) | Review, genetics, mechanistic studies | Wang & Walter 2020, doi: https://doi.org/10.1146/annurev-cellbio-031220-015840; Castanzo et al. 2020, doi: https://doi.org/10.1073/pnas.1920109117 |
| Mechanism of substrate engagement | Structural work shows substrate threading through a **hydrophobic/aromatic central pore**. Human ATAD1 uses pore-loop residues including **W166/Y167** to grip substrate; mutations impair activity or peptide binding by >100-fold in some assays (pqac-00000021, pqac-00000022) | Cryo-EM, mutagenesis, peptide-binding assays | Wang et al. 2022, doi: https://doi.org/10.7554/elife.73941 |
| Processive unfoldase/translocase behavior | Msp1/ATAD1-family enzymes act as **processive protein translocases/unfoldases** that thread substrates through the pore; ATPase activity depends on oligomeric state, supporting a mechanical extraction model for hydrophobic membrane proteins (pqac-00000015) | Biochemical reconstitution, EM | Castanzo et al. 2020, doi: https://doi.org/10.1073/pnas.1920109117 |
| Human apoptotic substrate: BIM | A key human ATAD1-specific finding is direct, specific extraction of **BIM** from membranes/mitochondria to inactivate this pro-apoptotic factor. In liposome assays, extraction is **ATP-dependent**, requires membrane anchoring, and is lost with the catalytic **E193Q** mutant (pqac-00000003, pqac-00000007, pqac-00000025) | Reconstituted biochemistry, co-IP, genetics, figure-level assay evidence | Winter et al. 2022, doi: https://doi.org/10.7554/elife.82860 |
| Substrate selectivity in apoptosis | ATAD1 extraction is **selective**, not universal for BH3-only proteins: in the reported reconstitution, ATAD1 extracted **BIM** but not **BIK**, **PUMA**, or yeast **Fis1** under the same conditions (pqac-00000007, pqac-00000025) | Reconstituted biochemistry, figure quantification | Winter et al. 2022, doi: https://doi.org/10.7554/elife.82860 |
| Cancer relevance / collateral lethality | **ATAD1 is adjacent to PTEN on 10q23** and is often co-deleted with PTEN in tumors. ATAD1 loss sensitizes cells and xenografts to **proteasome inhibitors** by increasing BIM-dependent apoptotic priming, suggesting a therapeutic vulnerability in ATAD1-null cancers (pqac-00000003, pqac-00000007) | Cancer genetics, cell biology, xenografts | Winter et al. 2022, doi: https://doi.org/10.7554/elife.82860 |
| Disease/application concept | Proposed application: exploit **proteasome dysfunction/proteasome inhibitor sensitivity** in cancers with ATAD1 loss; this is a preclinical therapeutic concept rather than an approved ATAD1-targeted therapy (pqac-00000003) | Preclinical translational study | Winter et al. 2022, doi: https://doi.org/10.7554/elife.82860 |
| Mitochondrial dynamics (newer role) | A 2023 study of the homolog **Yta4/ATAD1** identified a role in **inhibiting mitochondrial fission** by acting on divisome components (**Fis1, Mdv1, Dnm1**), expanding the conceptual landscape of ATAD1-family biology beyond proteostasis alone (pqac-00000023) | Genetics, interaction assays, in vitro assembly assays | He et al. 2023, doi: https://doi.org/10.1371/journal.pbio.3002247 |
| 2023 conceptual update on proofreading | 2023 synthesis emphasized Msp1/ATAD1 as a **proofreading system** for TA protein localization, integrating extraction, GET-mediated rerouting, and selective degradation as a multilayer quality-control network (pqac-00000006, pqac-00000020) | Review | Matsumoto 2023, doi: https://doi.org/10.1093/jb/mvad025 |
| 2023-2024 reconstituted assay advance | New quantitative reconstituted assays using split-luciferase/defined proteoliposomes enabled controlled testing of **substrate selectivity** and membrane determinants of extraction, creating a more rigorous platform for ATAD1/Msp1 mechanism studies (pqac-00000016, pqac-00000018) | Method development, reconstitution | Fresenius et al. 2024, doi: https://doi.org/10.1101/2023.07.11.548587 |
| 2024 substrate-recognition model | 2024 work proposed that substrate recognition depends strongly on **hydrophobic mismatch** between the substrate transmembrane segment and the surrounding bilayer; extraction of a substrate TMD from the membrane appears to be the **rate-limiting step** (pqac-00000016, pqac-00000019) | Reconstituted biochemistry, membrane engineering | Fresenius et al. 2024, doi: https://doi.org/10.1101/2023.07.11.548587 |
| 2024 energetic/mechanistic direction | Emerging 2024 linked-dimer/energetic studies indicate a **minimum ATP hydrolysis rate** is needed for efficient TMH extraction and suggest **mechanistic plasticity** in subunit coordination during extraction; relevant to ATAD1 by homology but not yet a direct human ATAD1 paper in the retrieved evidence set (pqac-00000016) | Preprint mechanistic biochemistry (family-level inference) | Smith et al. 2024, doi: https://doi.org/10.1101/2024.09.23.614443 |
| Synaptic regulation | ATAD1/Thorase also has a noncanonical neuronal role in **AMPA receptor trafficking**. It forms complexes with **GluR2 and GRIP1**, can disassemble the GluR2–GRIP1 complex in an **ATP-dependent** manner, and is required for activity-dependent AMPAR internalization/downscaling (pqac-00000000, pqac-00000028) | Biochemistry, neuronal cell biology, mouse genetics | Wang & Walter 2020, doi: https://doi.org/10.1146/annurev-cellbio-031220-015840 |
| Neurological phenotypes | ATAD1 loss/function compromise is associated with **seizures**, impaired fear conditioning, worsened post-stroke deficits in mice, and severe human **encephalopathy/stiffness/arthrogryposis** in homozygous mutation cases; AMPAR antagonists reportedly ameliorated some defects (pqac-00000027, pqac-00000028) | Mouse genetics, clinical association, review | Wang & Walter 2020, doi: https://doi.org/10.1146/annurev-cellbio-031220-015840 |
| Other disease associations / databases | Open Targets lists ATAD1 associations with **hereditary hyperekplexia/hyperekplexia 4** and broader neurodegenerative phenotypes, but these database-level links should be interpreted as hypothesis-generating unless supported by primary studies (pqac-00000024) | Database | Open Targets platform query (context evidence) |
| Organelle-disease modifier role | In Zellweger-spectrum models, **ATAD1 overexpression** was reported to rescue aspects of mitochondrial dysfunction caused by mislocalized peroxisomal proteins, suggesting a disease-modifier role in organelle proteostasis (pqac-00000001) | Cell biology, disease-model study | Nuebel et al. 2021, doi: https://doi.org/10.15252/embr.202051991 |
| Overall functional annotation | Best-supported primary annotation for human ATAD1 is: **outer mitochondrial membrane AAA+ extractase/translocase that removes mislocalized TA proteins and stalled import substrates, coupling ATP hydrolysis to membrane protein extraction; additional metazoan-specialized roles include apoptosis control via BIM extraction and neuronal AMPAR trafficking** (pqac-00000000, pqac-00000003, pqac-00000005, pqac-00000028) | Integrated review of structure, biochemistry, genetics, disease evidence | Chen et al. 2014, doi: https://doi.org/10.15252/embj.201487943; Wang & Walter 2020, doi: https://doi.org/10.1146/annurev-cellbio-031220-015840; Wang et al. 2022, doi: https://doi.org/10.7554/elife.73941; Winter et al. 2022, doi: https://doi.org/10.7554/elife.82860 |


*Table: This table summarizes the main functional annotation evidence for human ATAD1/Thorase (UniProt Q8NBU5), spanning localization, molecular mechanism, substrates, pathways, disease relevance, and translational implications. It highlights both foundational studies and newer 2023-2024 developments in substrate recognition and membrane-extraction mechanism.*