biostudies-literatureKhalil BTarget ALSNIA NIH HHSLiveLikeLou Center at the University of Pittsburgh Brain InstituteBrightFocus FoundationRobert E. Jacoby ProfessorshipNIHMayo Clinic VenturesRobert Packard Center for ALS Research, Johns Hopkins UniversityU.S. Department of DefenseNINDS NIH HHSRainwater Charitable FoundationCSR NIH HHSCureSMACenter for Scientific ReviewNIH HHSMayo Clinic Center for Biomedical Discovery80https://www.ebi.ac.uk/biostudies/studies/S-EPMC9733332biostudies-literatureUnknown17(1)<h4>Background</h4>Cytoplasmic mislocalization and aggregation of TAR DNA-binding protein-43 (TDP-43) is a hallmark of the amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD) disease spectrum, causing both nuclear loss-of-function and cytoplasmic toxic gain-of-function phenotypes. While TDP-43 proteinopathy has been associated with defects in nucleocytoplasmic transport, this process is still poorly understood. Here we study the role of karyopherin-β1 (KPNB1) and other nuclear import receptors in regulating TDP-43 pathology.<h4>Methods</h4>We used immunostaining, immunoprecipitation, biochemical and toxicity assays in cell lines, primary neuron and organotypic mouse brain slice cultures, to determine the impact of KPNB1 on the solubility, localization, and toxicity of pathological TDP-43 constructs. Postmortem patient brain and spinal cord tissue was stained to assess KPNB1 colocalization with TDP-43 inclusions. Turbidity assays were employed to study the dissolution and prevention of aggregation of recombinant TDP-43 fibrils in vitro. Fly models of TDP-43 proteinopathy were used to determine the effect of KPNB1 on their neurodegenerative phenotype in vivo.<h4>Results</h4>We discovered that several members of the nuclear import receptor protein family can reduce the formation of pathological TDP-43 aggregates. Using KPNB1 as a model, we found that its activity depends on the prion-like C-terminal region of TDP-43, which mediates the co-aggregation with phenylalanine and glycine-rich nucleoporins (FG-Nups) such as Nup62. KPNB1 is recruited into these co-aggregates where it acts as a molecular chaperone that reverses aberrant phase transition of Nup62 and TDP-43. These findings are supported by the discovery that Nup62 and KPNB1 are also sequestered into pathological TDP-43 aggregates in ALS/FTD postmortem CNS tissue, and by the identification of the fly ortholog of KPNB1 as a strong protective modifier in Drosophila models of TDP-43 proteinopathy. Our results show that KPNB1 can rescue all hallmarks of TDP-43 pathology, by restoring its solubility and nuclear localization, and reducing neurodegeneration in cellular and animal models of ALS/FTD.<h4>Conclusion</h4>Our findings suggest a novel NLS-independent mechanism where, analogous to its canonical role in dissolving the diffusion barrier formed by FG-Nups in the nuclear pore, KPNB1 is recruited into TDP-43/FG-Nup co-aggregates present in TDP-43 proteinopathies and therapeutically reverses their deleterious phase transition and mislocalization, mitigating neurodegeneration.Molecular neurodegenerationNuclear import receptors are recruited by FG-nucleoporins to rescue hallmarks of TDP-43 proteinopathy.PMC9733332R01NS105756P30AG072931LiveLikeLou Center at the University of Pittsburgh Brain InstituteR01AG077771R01NS127187Robert E. Jacoby ProfessorshipR35NS097273Mayo Clinic VenturesR21AG064940Robert Packard Center for ALS Research, Johns Hopkins UniversityP30 AG072931P30AG062677R01NS113943R01NS117461Rainwater Charitable FoundationR33 NS110960Mayo Clinic Center for Biomedical DiscoveryR01 AG077771R01AG059871Target ALSRF1 AG068581P01NS084974RF1AG068581R33NS110960T32 NS086749RF1 AG076122R21NS096647Audrey Lewis Young Investigator AwardR01NS097542U54NS123743W81XWH-19–1-0193A2021038SDickson DWDonnelly CJKhalil BZhang KGao JCroft CLSmith CLGolde TERossoll WWren MCPetrucelli LLee JHTsai CWChhangani DChen JGleixner AMShorter JBarmada SJOskarsson BLi XLim CKYoshimura SHRincon-Limas DEFortin GMorderer DPuttinger CLiu FChou CCfalseNuclear import receptors are recruited by FG-nucleoporins to rescue hallmarks of TDP-43 proteinopathy.<h4>Background</h4>Cytoplasmic mislocalization and aggregation of TAR DNA-binding protein-43 (TDP-43) is a hallmark of the amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD) disease spectrum, causing both nuclear loss-of-function and cytoplasmic toxic gain-of-function phenotypes. While TDP-43 proteinopathy has been associated with defects in nucleocytoplasmic transport, this process is still poorly understood. Here we study the role of karyopherin-β1 (KPNB1) and other nuclear import receptors in regulating TDP-43 pathology.<h4>Methods</h4>We used immunostaining, immunoprecipitation, biochemical and toxicity assays in cell lines, primary neuron and organotypic mouse brain slice cultures, to determine the impact of KPNB1 on the solubility, localization, and toxicity of pathological TDP-43 constructs. Postmortem patient brain and spinal cord tissue was stained to assess KPNB1 colocalization with TDP-43 inclusions. Turbidity assays were employed to study the dissolution and prevention of aggregation of recombinant TDP-43 fibrils in vitro. Fly models of TDP-43 proteinopathy were used to determine the effect of KPNB1 on their neurodegenerative phenotype in vivo.<h4>Results</h4>We discovered that several members of the nuclear import receptor protein family can reduce the formation of pathological TDP-43 aggregates. Using KPNB1 as a model, we found that its activity depends on the prion-like C-terminal region of TDP-43, which mediates the co-aggregation with phenylalanine and glycine-rich nucleoporins (FG-Nups) such as Nup62. KPNB1 is recruited into these co-aggregates where it acts as a molecular chaperone that reverses aberrant phase transition of Nup62 and TDP-43. These findings are supported by the discovery that Nup62 and KPNB1 are also sequestered into pathological TDP-43 aggregates in ALS/FTD postmortem CNS tissue, and by the identification of the fly ortholog of KPNB1 as a strong protective modifier in Drosophila models of TDP-43 proteinopathy. Our results show that KPNB1 can rescue all hallmarks of TDP-43 pathology, by restoring its solubility and nuclear localization, and reducing neurodegeneration in cellular and animal models of ALS/FTD.<h4>Conclusion</h4>Our findings suggest a novel NLS-independent mechanism where, analogous to its canonical role in dissolving the diffusion barrier formed by FG-Nups in the nuclear pore, KPNB1 is recruited into TDP-43/FG-Nup co-aggregates present in TDP-43 proteinopathies and therapeutically reverses their deleterious phase transition and mislocalization, mitigating neurodegeneration.2022-01-01T00:00:00Z2022 Dec2025-04-19T06:39:25.866Z2025-04-19T06:39:25.866ZS-EPMC97333323648242210.1186/s13024-022-00585-1