bims-nucpor Biomed News
on Nuclear pore complex and nucleoporins in stress, aging and disease
Issue of 2023–05–14
six papers selected by
Sara Mingu, Johannes Gutenberg University
  1. TorsinA is essential for the timing and localization of neuronal nuclear pore complex biogenesis.
  2. Distinct domains in Ndc1 mediate its interaction with the Nup84 complex and the nuclear membrane.
  3. Peroxisome biogenesis initiated by protein phase separation.
  4. Centralspindlin proteins Pavarotti and Tumbleweed along with WASH regulate nuclear envelope budding.
  5. Molecular mechanisms of nuclear transport of the neuronal voltage-gated Ca2+ channel β3 auxiliary subunit.
  6. Repurposing FDA-Approved Drugs for Temozolomide-resistant IDH1 Mutant Glioma using High-Throughput Miniaturized Screening on Droplet Microarray Chip.
  1. bioRxiv. 2023 Apr 27. pii: 2023.04.26.538491. [Epub ahead of print]
    TorsinA is essential for the timing and localization of neuronal nuclear pore complex biogenesis.
    Sumin Kim, Sébastien Phan, Thomas R Shaw, Mark H Ellisman, Sarah L Veatch, Sami J Barmada, Samuel S Pappas, William T Dauer.
      Nuclear pore complexes (NPCs) regulate information transfer between the nucleus and cytoplasm. NPC defects are linked to several neurological diseases, but the processes governing NPC biogenesis and spatial organization are poorly understood. Here, we identify a temporal window of strongly upregulated NPC biogenesis during neuronal maturation. We demonstrate that the AAA+ protein torsinA, whose loss of function causes the neurodevelopmental movement disorder DYT-TOR1A (DYT1) dystonia, coordinates NPC spatial organization during this period without impacting total NPC density. Using a new mouse line in which endogenous Nup107 is Halo-Tagged, we find that torsinA is essential for correct localization of NPC formation. In the absence of torsinA, the inner nuclear membrane buds excessively at sites of mislocalized, nascent NPCs, and NPC assembly completion is delayed. Our work implies that NPC spatial organization and number are independently regulated and suggests that torsinA is critical for the normal localization and assembly kinetics of NPCs.
    DOI:  https://doi.org/10.1101/2023.04.26.538491
  2. J Cell Biol. 2023 Jun 05. pii: e202210059. [Epub ahead of print]222(6):
    Distinct domains in Ndc1 mediate its interaction with the Nup84 complex and the nuclear membrane.
    Ingo Amm, Marion Weberruss, Andrea Hellwig, Johannes Schwarz, Marianna Tatarek-Nossol, Christian Lüchtenborg, Martina Kallas, Britta Brügger, Ed Hurt, Wolfram Antonin.
      Nuclear pore complexes (NPCs) are embedded in the nuclear envelope and built from ∼30 different nucleoporins (Nups) in multiple copies, few are integral membrane proteins. One of these transmembrane nucleoporins, Ndc1, is thought to function in NPC assembly at the fused inner and outer nuclear membranes. Here, we show a direct interaction of Ndc1's transmembrane domain with Nup120 and Nup133, members of the pore membrane coating Y-complex. We identify an amphipathic helix in Ndc1's C-terminal domain binding highly curved liposomes. Upon overexpression, this amphipathic motif is toxic and dramatically alters the intracellular membrane organization in yeast. Ndc1's amphipathic motif functionally interacts with related motifs in the C-terminus of the nucleoporins Nup53 and Nup59, important for pore membrane binding and interconnecting NPC modules. The essential function of Ndc1 can be suppressed by deleting the amphipathic helix from Nup53. Our data indicate that nuclear membrane and presumably NPC biogenesis depends on a balanced ratio between amphipathic motifs in diverse nucleoporins.
    DOI:  https://doi.org/10.1083/jcb.202210059
  3. Nature. 2023 May 10.
    Peroxisome biogenesis initiated by protein phase separation.
    Rini Ravindran, Isabel O L Bacellar, Xavier Castellanos-Girouard, Haytham M Wahba, Zhenghao Zhang, James G Omichinski, Lydia Kisley, Stephen W Michnick.
      Peroxisomes are organelles that carry out β-oxidation of fatty acids and amino acids. Both rare and prevalent diseases are caused by their dysfunction1. Among disease-causing variant genes are those required for protein transport into peroxisomes. The peroxisomal protein import machinery, which also shares similarities with chloroplasts2, is unique in transporting folded and large, up to 10 nm in diameter, protein complexes into peroxisomes3. Current models postulate a large pore formed by transmembrane proteins4; however, so far, no pore structure has been observed. In the budding yeast Saccharomyces cerevisiae, the minimum transport machinery includes the membrane proteins Pex13 and Pex14 and the cargo-protein-binding transport receptor, Pex5. Here we show that Pex13 undergoes liquid-liquid phase separation (LLPS) with Pex5-cargo. Intrinsically disordered regions in Pex13 and Pex5 resemble those found in nuclear pore complex proteins. Peroxisomal protein import depends on both the number and pattern of aromatic residues in these intrinsically disordered regions, consistent with their roles as 'stickers' in associative polymer models of LLPS5,6. Finally, imaging fluorescence cross-correlation spectroscopy shows that cargo import correlates with transient focusing of GFP-Pex13 and GFP-Pex14 on the peroxisome membrane. Pex13 and Pex14 form foci in distinct time frames, suggesting that they may form channels at different saturating concentrations of Pex5-cargo. Our findings lead us to suggest a model in which LLPS of Pex5-cargo with Pex13 and Pex14 results in transient protein transport channels7.
    DOI:  https://doi.org/10.1038/s41586-023-06044-1
  4. J Cell Biol. 2023 Aug 07. pii: e202211074. [Epub ahead of print]222(8):
    Centralspindlin proteins Pavarotti and Tumbleweed along with WASH regulate nuclear envelope budding.
    Kerri A Davidson, Mitsutoshi Nakamura, Jeffrey M Verboon, Susan M Parkhurst.
      Nuclear envelope (NE) budding is a nuclear pore-independent nuclear export pathway, analogous to the egress of herpesviruses, and required for protein quality control, synapse development, and mitochondrial integrity. The physical formation of NE buds is dependent on the Wiskott-Aldrich Syndrome protein, Wash, its regulatory complex (SHRC), and Arp2/3, and requires Wash's actin nucleation activity. However, the machinery governing cargo recruitment and organization within the NE bud remains unknown. Here, we identify Pavarotti (Pav) and Tumbleweed (Tum) as new molecular components of NE budding. Pav and Tum interact directly with Wash and define a second nuclear Wash-containing complex required for NE budding. Interestingly, we find that the actin-bundling activity of Pav is required, suggesting a structural role in the physical and/or organizational aspects of NE buds. Thus, Pav and Tum are providing exciting new entry points into the physical machineries of this alternative nuclear export pathway for large cargos during cell differentiation and development.
    DOI:  https://doi.org/10.1083/jcb.202211074
  5. Neuroscience. 2023 May 09. pii: S0306-4522(23)00181-1. [Epub ahead of print]
    Molecular mechanisms of nuclear transport of the neuronal voltage-gated Ca2+ channel β3 auxiliary subunit.
    Alejandra Corzo-López, Margarita Leyva-Leyva, Valeria Castillo-Viveros, Miriam Fernández-Gallardo, David Muñoz-Herrera, Alejandro Sandoval, Ricardo González-Ramírez, Ricardo Felix.
      Previous studies have shown that in addition to its role within the voltage-gated calcium channel complex in the plasma membrane, the neuronal CaVβ subunit can translocate to the cell nucleus. However, little is known regarding the role this protein could play in the nucleus, nor the molecular mechanism used by CaVβ to enter this cell compartment. This report shows evidence that CaVβ3 has nuclear localization signals (NLS) that are not functional, suggesting that the protein does not use a classical nuclear import pathway. Instead, its entry into the nucleus could be associated with another protein that would function as a carrier, using a mechanism known as a piggyback. Mass spectrometry assays and bioinformatic analysis allowed the identification of proteins that could be participating in the entry of CaVβ3 into the nucleus. Likewise, through proximity ligation assays (PLA), it was found that members of the heterogeneous nuclear ribonucleoproteins (hnRNPs) and B56δ, a regulatory subunit of the protein phosphatase 2A (PP2A), could function as proteins that regulate this piggyback mechanism. On the other hand, bioinformatics and site-directed mutagenesis assays allowed the identification of a functional nuclear export signal (NES) that controls the exit of CaVβ3 from the nucleus, which would allow the completion of the nuclear transport cycle of the protein. These results reveal a novel mechanism for the nuclear transport cycle of the neuronal CaVβ3 subunit.
    Keywords:  B56δ; Ca(V)β(3) subunit; calcium channels; hnRNPs; piggyback
    DOI:  https://doi.org/10.1016/j.neuroscience.2023.04.015
  6. Adv Healthc Mater. 2023 May 10. e2300591
    Repurposing FDA-Approved Drugs for Temozolomide-resistant IDH1 Mutant Glioma using High-Throughput Miniaturized Screening on Droplet Microarray Chip.
    Haijun Cui, Xueyuan Sun, Marcel Schilling, Christel Herold-Mende, Markus Reischl, Pavel A Levkin, Anna A Popova, Şevin Turcan.
      To address the challenge of drug resistance and limited treatment options for recurrent gliomas with IDH1 mutations, a highly miniaturized screening of 2208 FDA-approved drugs is conducted using a high-throughput droplet microarray (DMA) platform. Two patient-derived temozolomide-resistant tumorspheres harboring endogenous IDH1 mutations (IDH1mut ) are utilized. Screening identifies over 20 drugs, including verteporfin (VP), that significantly affected tumorsphere formation and viability. Proteomics analysis reveals that nuclear pore complex may be a potential VP target, suggesting a new mechanism of action independent of its known effects on YAP1. Knockdown experiments exclude YAP1 as a drug target in tumorspheres. Pathway analysis shows that NUP107 is a potential upstream regulator associated with VP response. Analysis of publicly available genomics datasets shows a significant correlation between high NUP107 expression and decreased survival in IDH1mut astrocytoma, suggesting NUP107 could be a potential biomarker for VP response. This study demonstrates a miniaturized approach for cost-effective drug repurposing using 3D glioma models and identifies nuclear pore complex as a potential target for drug development. The findings provide preclinical evidence to support in vivo and clinical studies of VP and other identified compounds to treat IDH1mut gliomas, which may ultimately improve clinical outcomes for patients with this challenging disease. This article is protected by copyright. All rights reserved.
    Keywords:  IDH1 mutant; NUPs; droplet microarrays; drug repurposing; lower-grade gliomas; miniaturized high throughput screening; verteporfin
    DOI:  https://doi.org/10.1002/adhm.202300591
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