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A minimal construct of nuclear-import receptor Karyopherin-β2 defines the regions critical for chaperone and disaggregation activity

2022; Elsevier BV; Volume: 299; Issue: 2 Linguagem: Inglês

10.1016/j.jbc.2022.102806

ISSN

1083-351X

Autores

Charlotte M. Fare, Kevin Rhine, Andrew Lam, Sua Myong, James Shorter,

Tópico(s)

Neurogenetic and Muscular Disorders Research

Resumo

Karyopherin-β2 (Kapβ2) is a nuclear-import receptor that recognizes proline-tyrosine nuclear localization signals of diverse cytoplasmic cargo for transport to the nucleus. Kapβ2 cargo includes several disease-linked RNA-binding proteins with prion-like domains, such as FUS, TAF15, EWSR1, hnRNPA1, and hnRNPA2. These RNA-binding proteins with prion-like domains are linked via pathology and genetics to debilitating degenerative disorders, including amyotrophic lateral sclerosis, frontotemporal dementia, and multisystem proteinopathy. Remarkably, Kapβ2 prevents and reverses aberrant phase transitions of these cargoes, which is cytoprotective. However, the molecular determinants of Kapβ2 that enable these activities remain poorly understood, particularly from the standpoint of nuclear-import receptor architecture. Kapβ2 is a super-helical protein comprised of 20 HEAT repeats. Here, we design truncated variants of Kapβ2 and assess their ability to antagonize FUS aggregation and toxicity in yeast and FUS condensation at the pure protein level and in human cells. We find that HEAT repeats 8 to 20 of Kapβ2 recapitulate all salient features of Kapβ2 activity. By contrast, Kapβ2 truncations lacking even a single cargo-binding HEAT repeat display reduced activity. Thus, we define a minimal Kapβ2 construct for delivery in adeno-associated viruses as a potential therapeutic for amyotrophic lateral sclerosis/frontotemporal dementia, multisystem proteinopathy, and related disorders. Karyopherin-β2 (Kapβ2) is a nuclear-import receptor that recognizes proline-tyrosine nuclear localization signals of diverse cytoplasmic cargo for transport to the nucleus. Kapβ2 cargo includes several disease-linked RNA-binding proteins with prion-like domains, such as FUS, TAF15, EWSR1, hnRNPA1, and hnRNPA2. These RNA-binding proteins with prion-like domains are linked via pathology and genetics to debilitating degenerative disorders, including amyotrophic lateral sclerosis, frontotemporal dementia, and multisystem proteinopathy. Remarkably, Kapβ2 prevents and reverses aberrant phase transitions of these cargoes, which is cytoprotective. However, the molecular determinants of Kapβ2 that enable these activities remain poorly understood, particularly from the standpoint of nuclear-import receptor architecture. Kapβ2 is a super-helical protein comprised of 20 HEAT repeats. Here, we design truncated variants of Kapβ2 and assess their ability to antagonize FUS aggregation and toxicity in yeast and FUS condensation at the pure protein level and in human cells. We find that HEAT repeats 8 to 20 of Kapβ2 recapitulate all salient features of Kapβ2 activity. By contrast, Kapβ2 truncations lacking even a single cargo-binding HEAT repeat display reduced activity. Thus, we define a minimal Kapβ2 construct for delivery in adeno-associated viruses as a potential therapeutic for amyotrophic lateral sclerosis/frontotemporal dementia, multisystem proteinopathy, and related disorders. Karyopherin-β2 (Kapβ2; also known as Transportin 1) is a nuclear-import receptor (NIR) that transports proteins bearing a proline-tyrosine nuclear localization signal (PY-NLS) from the cytoplasm to the nucleus (1Lee B.J. Cansizoglu A.E. Suel K.E. Louis T.H. Zhang Z. Chook Y.M. Rules for nuclear localization sequence recognition by Karyopherin beta 2.Cell. 2006; 126: 543-558Abstract Full Text Full Text PDF PubMed Scopus (423) Google Scholar, 2Soniat M. Chook Y.M. Nuclear localization signals for four distinct Karyopherin-beta nuclear import systems.Biochem. J. 2015; 468: 353-362Crossref PubMed Scopus (115) Google Scholar, 3Wing C.E. Fung H.Y.J. Chook Y.M. Karyopherin-mediated nucleocytoplasmic transport.Nat. Rev. Mol. 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Kapβ2 has a low affinity for Ran-GDP, which permits Kapβ2 interactions with cargo in the cytoplasm (3Wing C.E. Fung H.Y.J. Chook Y.M. Karyopherin-mediated nucleocytoplasmic transport.Nat. Rev. Mol. Cell Biol. 2022; 23: 307-328Crossref PubMed Scopus (21) Google Scholar, 7Chook Y.M. Blobel G. Structure of the nuclear transport complex Karyopherin-beta2-Ran x GppNHp.Nature. 1999; 399: 230-237Crossref PubMed Scopus (291) Google Scholar). Once in the nucleus, Kapβ2 is engaged tightly by Ran-GTP, which elicits a conformational change in Kapβ2 that releases cargo and liberates Kapβ2 for repeated rounds of nuclear import (3Wing C.E. Fung H.Y.J. Chook Y.M. Karyopherin-mediated nucleocytoplasmic transport.Nat. Rev. Mol. Cell Biol. 2022; 23: 307-328Crossref PubMed Scopus (21) Google Scholar, 7Chook Y.M. Blobel G. Structure of the nuclear transport complex Karyopherin-beta2-Ran x GppNHp.Nature. 1999; 399: 230-237Crossref PubMed Scopus (291) Google Scholar, 8Nakielny S. Dreyfuss G. 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