Nucleocytoplasmic Transport Of Proteins Research Articles

Multiple types of nuclear localization signals in Entamoeba histolytica

Entamoeba histolytica is a protozoan parasite that belongs to the Amoebozoa supergroup whose study related to the nucleocytoplasmic transport of proteins through the nucleus is poorly studied. In this work, we have performed in silico predictions of the potential nuclear localization signals (NLS) corresponding to the proteome of 8201 proteins from Entamoeba histolytica annotated in the AmoebaDB database. We have found the presence of monopartite nuclear localization signals (MNLSs), bipartite nuclear localization signals (BNLSs), and non-canonical monopartite NLSs with lengths exceeding 20 amino acid residues. Additionally, we detected a new type of NLS consisting of multiple juxtaposed bipartite NLSs (JNLSs) that have not been described in any eukaryotic organism. Also, we have generated consensus sequences for the nuclear import of proteins with the NLSs obtained. Docking experiments between EhImportin α and an MNLS, BNLS, and JNLS outlined the interacting residues between the Importin and cargo proteins, emphasizing their putative roles in nuclear import. By transfecting HA-tagged protein constructs, we assessed the nuclear localization of MNLS (U1A and U2AF1), JMNLS (U2AF2), and non-canonical NLS (N-terminus of Pol ll) in vivo. Our data provide the basis for understanding the nuclear transport process in E. histolytica.

Single-nucleus proteomics identifies regulators of protein transport.

The physiological response of a cell to stimulation depends on its proteome configuration. Therefore, the abundance variation of regulatory proteins across unstimulated single cells can be associatively linked with their response to stimulation. Here we developed an approach that leverages this association across individual cells and nuclei to systematically identify potential regulators of biological processes, followed by targeted validation. Specifically, we applied this approach to identify regulators of nucleocytoplasmic protein transport in macrophages stimulated with lipopolysaccharide (LPS). To this end, we quantified the proteomes of 3,412 individual nuclei, sampling the dynamic response to LPS treatment, and linking functional variability to proteomic variability. Minutes after the stimulation, the protein transport in individual nuclei correlated strongly with the abundance of known protein transport regulators, thus revealing the impact of natural protein variability on functional cellular response. We found that simple biophysical constraints, such as the quantity of nuclear pores, partially explain the variability in LPS-induced nucleocytoplasmic transport. Among the many proteins newly identified to be associated with the response, we selected 16 for targeted validation by knockdown. The knockdown phenotypes confirmed the inferences derived from natural protein and functional variation of single nuclei, thus demonstrating the potential of (sub-)single-cell proteomics to infer functional regulation. We expect this approach to generalize to broad applications and enhance the functional interpretability of single-cell omics data.

Mechanical asymmetry in nucleocytoplasmic protein transport

Mechanical asymmetry in nucleocytoplasmic protein transport

Abstract 7269: Karyopherin α-2, a nuclear export protein, promotes cancer progression in lung adenocarcinoma

Abstract Introduction: Karyopherin α-2 (KPNA2), a nucleocytoplasmic transport protein, regulates the nuclear import of macromolecules and contributes to carcinogenesis. Actually, KPNA2 is upregulated in various types of cancer tissues and serum from cancer patients. In particular, it is associated with cancer invasiveness and poor prognosis in patient. Here, we tried to present the molecular mechanism and clinical significance of KPNA2 in lung cancer progression and metastasis. Method: First, we retrospectively analyzed the data extracted from EMR for patients with non-small cell lung cancer receiving curative surgical resection in Uijeongbu and Bucheon St. Mary’s Hospitals (n=165). Immunohistochemistry staining was performed on the tumor microarray samples using antibodies against KPNA2. The functional assay and gene silencing was conducted. Result: The clinical and pathological information of the experimental group is as follows. Based on the TMA staining, mean KPNA2 score was 36.5 [0-240] and median value was 10. Based on the TMA staining, patients with high KPNA2 expression were related to lymphatic invasion (p = 0.00782), advanced stage (p = 0.0202), and current smoker (p = 0.0074). KPNA2 expression was higher in squamous cell carcinoma than in adenocarcinoma histotype. Patients with high KPNA2 expression showed shorter survival than those with low KPNA2 (median OS (months), 72.8 vs 42.2, P < 0.0001; median RFS (months), 72.8 vs 32.1, P < 0.0011) and relevant to high recurrence (recurrence rate (%), 24.7 vs 44.7, p = 0.007). Further, high KPNA2 expression was associated with poor survival outcomes. Knockdown of KPNA2 in lung cancer cells suppressed the invasion and migration of lung cancer cells and inhibited metastasis in a mouse model of lung cancer. Inversely, KPNA2 overexpression promoted cancer cell growth, invasion, and migration. Moreover, ectopic expression of KPNA2 made lung cancer cells less sensitive to anticancer drugs, Talazoparib and Olaparib, indicating that KPNA2 enhances drug resistance in lung cancer cells. Conclusion: Collectively, this study suggest that KPNA2 promotes invasiveness and metastasis and is associated with poor patient outcomes; therefore, KPNA2 will be a good therapeutic target or a biomarker in lung adenocarcinoma. Citation Format: Inyoung Cheon, Seoree Kim, Sengran Cho, Heejin Lee, Jung-Sook Yoon, Ji Hyun Lee, Sang Hoon Chun, Hye Sung Won, Soon Auck Hong, Yoon Ho Ko, Young-Ho Ahn. Karyopherin α-2, a nuclear export protein, promotes cancer progression in lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7269.

Identifying novel inhibitors targeting Exportin-1 for the potential treatment of COVID-19.

The nuclear export protein 1 (XPO1) mediates the nucleocytoplasmic transport of proteins and ribonucleic acids (RNAs) and plays a prominent role in maintaining cellular homeostasis. XPO1 has emerged as a promising therapeutic approach to interfere with the lifecycle of many viruses. In our earlier study, we proved the inhibition of XPO1 as a therapeutic strategy for managing SARS-COV-2 and its variants. In this study, we have utilized pharmacophore-assisted computational methods to identify prominent XPO1 inhibitors. After several layers of screening, a few molecules were shortlisted for further experimental validation on the in vitro SARS-CoV-2 cell infection model. It was observed that these compounds reduced spike positivity, suggesting inhibition of SARS-COV-2 infection. The outcome of this study could be considered further for developing novel antiviral therapeutic strategies against SARS-CoV-2.

Dynamics of nuclear export of pre-ribosomal subunits revealed by high-speed single-molecule microscopy in live cells

We present a study on the nuclear export efficiency and time of pre-ribosomal subunits in live mammalian cells, using high-speed single-molecule tracking and single-molecule fluorescence resonance energy transfer techniques. Our findings reveal that pre-ribosomal particles exhibit significantly higher nuclear export efficiency compared to other large cargos like mRNAs, with around two-thirds of interactions between the pre-60S or pre-40S and the nuclear pore complexes (NPCs) resulting in successful export to the cytoplasm. We also demonstrate that nuclear transport receptor (NTR) chromosomal maintenance 1 (CRM1) plays a crucial role in nuclear export efficiency, with pre-60S and pre-40S particle export efficiency decreasing by 11-17-fold when CRM1 is inhibited. Our results suggest that multiple copies of CRM1 work cooperatively to chaperone pre-ribosomal subunits through the NPC, thus increasing export efficiency and decreasing export time. Significantly, this cooperative NTR mechanism extends beyond pre-ribosomal subunits, as evidenced by the enhanced nucleocytoplasmic transport of proteins.

Identification and characterization of karyopherin a-2, a nuclear export protein in lung adenocarcinoma.

e21025 Background: It is emerging that the Karyopherin a-2 (KPNA2), a nucleocytoplasmic transport protein, regulates the nuclear import of macromolecules and contributes to carcinogenesis and changes in cellular phenotype. In particular, it can be a poor prognostic marker by causing aberrant subcellular localization of DNA damage response proteins or OCT4-c MYC pathway molecules depending on the type of carcinoma and inducing anticancer resistance. In some carcinomas, an association with the p53 oncogenic pathway has been reported, showing good prognostic values. We aimed to investigate the clinical significance and metabolic pathway of stable cancer associated fibroblast (CAF) and cancer cells for KPNA2. Methods: We retrospectively analyzed the data extracted from EMR for NSCLC patients receiving curative surgical resection in Uijeongbu and Bucheon St. Mary’s Hospitals (n = 165). Immunohistochemistry staining was performed on the tumor microarray samples using antibodies against KPNA2. The functional assay and gene silencing was conducted. Results: Based on the TMA staining, mean KPNA2 score was 36.5 [0-240] and median value was 10. The clinical and pathological information of the experimental group is as follows. Table 1. Scatter plots and correlation between KPNA2 expression levels and tumor invasiveness markers reveals that high KPNA2 expressor was related to lymphatic invasion (p = 0.00782), advanced stage (p = 0.0202) and current smoker (p = 0.0074). KPNA2 expression was higher in squamous cell carcinoma(SqCC) histotype than in adenocarcinoma (SqCC ratio (%), 13.5 vs 43.4 in Low exp vs High exp; p = 0.007). Patients with high expression of KPNA2 showed shorter survival than other patients (median OS (months), 72.8 vs 42.2, P < 0.0001; median RFS (months), 72.8 vs 32.1, P < 0.0011) and relevant to high recurrence (recurrence rate (%), 24.7 vs 44.7, p = 0.007). Further, high KPNA2 expression was associated with poor survival outcomes. To test the effect of KPNA2 on cancer cell invasion, we knocked down Kpna2 via shRNA. Spheroids composed of H1299, Calu-6, A549, HCC827 lung cancer cells with either Kpna2-overexpression or Kpna2-knockdown, and spheroid invasion was then monitored for two days. Eminently, the 3-D invasion of spheroids was suppressed via Kpna2 knockdown. In addition, Kpna2-overexpressing cells promoted cancer invasion to a greater extent than control. Conclusions: In conclusion, our results suggest that KPNA2 protein expression has a poor prognostic association, revealed by its association with survival outcome or invasiveness markers. Its clinical significance as an oncogenic target molecule is emerging, and further evaluation using an organoid model is in progress.

Activin and BMP Signalling in Human Testicular Cancer Cell Lines, and a Role for the Nucleocytoplasmic Transport Protein Importin-5 in Their Crosstalk.

Testicular germ cell tumours (TGCTs) are the most common malignancy in young men. Originating from foetal testicular germ cells that fail to differentiate correctly, TGCTs appear after puberty as germ cell neoplasia in situ cells that transform through unknown mechanisms into distinct seminoma and non-seminoma tumour types. A balance between activin and BMP signalling may influence TGCT emergence and progression, and we investigated this using human cell line models of seminoma (TCam-2) and non-seminoma (NT2/D1). Activin A- and BMP4-regulated transcripts measured at 6 h post-treatment by RNA-sequencing revealed fewer altered transcripts in TCam-2 cells but a greater responsiveness to activin A, while BMP4 altered more transcripts in NT2/D1 cells. Activin significantly elevated transcripts linked to pluripotency, cancer, TGF-β, Notch, p53, and Hippo signalling in both lines, whereas BMP4 altered TGF-β, pluripotency, Hippo and Wnt signalling components. Dose-dependent antagonism of BMP4 signalling by activin A in TCam-2 cells demonstrated signalling crosstalk between these two TGF-β superfamily arms. Levels of the nuclear transport protein, IPO5, implicated in BMP4 and WNT signalling, are highly regulated in the foetal mouse germline. IPO5 knockdown in TCam-2 cells using siRNA blunted BMP4-induced transcript changes, indicating that IPO5 levels could determine TGF-β signalling pathway outcomes in TGCTs.

ACA-28, an anticancer compound, induces Pap1 nuclear accumulation via ROS-dependent and -independent mechanisms in fission yeast.

The nucleocytoplasmic transport of proteins is an important mechanism to control cell fate. Pap1 is a fission yeast nucleocytoplasmic shuttling transcription factor of which localization is redox regulated. The nuclear export factor Crm1/exportin negatively regulates Pap1 by exporting it from the nucleus to the cytoplasm. Here, we describe the effect of an anti-cancer compound ACA-28, an improved derivative of 1'-acetoxychavicol acetate (ACA), on the subcellular distribution of Pap1. ACA-28 induced nuclear accumulation of Pap1 more strongly than did ACA. ROS inhibitor N-acetyl-L-cysteine (NAC) partly antagonized the Pap1 nuclear accumulation induced by ACA-28. NAC almost abolished Pap1 nuclear localization upon H 2 O 2 , whereas leptomycin B (LMB)-mediated inhibition of Pap1 nuclear export was resistant to NAC. Collectively, ACA-28-mediated apoptosis in cancer cells may involve ROS-dependent and -independent mechanisms.

Comprehensive maturity of nuclear pore complexes regulates zygotic genome activation

Nuclear pore complexes (NPCs) are channels for nucleocytoplasmic transport of proteins and RNAs. However, it remains unclear whether composition, structure, and permeability of NPCs dynamically change during the cleavage period of vertebrate embryos and affect embryonic development. Here, we report that the comprehensive NPC maturity (CNM) controls the onset of zygotic genome activation (ZGA) during zebrafish early embryogenesis. We show that more nucleoporin proteins are recruited to and assembled into NPCs with development, resulting in progressive increase of NPCs in size and complexity. Maternal transcription factors (TFs) transport into nuclei more efficiently with increasing CNM. Deficiency or dysfunction of Nup133 or Ahctf1/Elys impairs NPC assembly, maternal TFs nuclear transport, and ZGA onset, while nup133 overexpression promotes these processes. Therefore, CNM may act as a molecular timer for ZGA by controlling nuclear transport of maternal TFs that reach nuclear concentration thresholds at a given time to initiate ZGA.

IPO7 Promotes Odontoblastic Differentiation and Inhibits Osteoblastic Differentiation Through Regulation of RUNX2 Expression and Translocation.

RUNX2, an important transcriptional factor for both odontoblastic and osteoblastic differentiation, is upregulated during osteoblastic differentiation, but downregulated during late odontoblastic differentiation. However, the specific mechanism of the different RUNX2 expression in bone and dentin remains largely unknown. Importin 7 (IPO7), a member of the karyopherin β-superfamily, mediates nucleocytoplasmic transport of proteins. In this study, we found that IPO7 was increasingly expressed from pre-odontoblasts to mature odontoblasts. IPO7 expression was increased with odontoblastic differentiation of mouse dental papilla cells (mDPCs) and knockdown of IPO7-inhibited cell differentiation. While in MC3T3-E1 cells, IPO7 was decreased during osteoblastic differentiation and knockdown of IPO7-promoted cell differentiation. In mPDCs, IPO7 was able to bind with some odontoblastic transcription factors, and imported them into the nucleus, but not with RUNX2. Furthermore, IPO7 inhibited the total RUNX2 expression by promoting HDAC6 nuclear localization during odontoblastic differentiation. However, in MC3T3-E1 cells, IPO7 inhibited the nuclear distribution of RUNX2 but did not affect the total protein level of RUNX2. In conclusion, we found that IPO7 promotes odontoblastic differentiation and inhibits osteoblastic differentiation through regulating RUNX2 expression and translocation differently.

Nuclear pore complexes - a doorway to neural injury in neurodegeneration.

The genetic underpinnings and end-stage pathological hallmarks of neurodegenerative diseases are increasingly well defined, but the cellular pathophysiology of disease initiation and propagation remains poorly understood, especially in sporadic forms of these diseases. Altered nucleocytoplasmic transport is emerging as a prominent pathomechanism of multiple neurodegenerative diseases, including amyotrophic lateral sclerosis, Alzheimer disease, frontotemporal dementia and Huntington disease. The nuclear pore complex (NPC) and interactions between its individual nucleoporin components and nuclear transport receptors regulate nucleocytoplasmic transport, as well as genome organization and gene expression. Specific nucleoporin abnormalities have been identified in sporadic and familial forms of neurodegenerative disease, and these alterations are thought to contribute to disrupted nucleocytoplasmic transport. The specific nucleoporins and nucleocytoplasmic transport proteins that have been linked to different neurodegenerative diseases are partially distinct, suggesting that NPC injury contributes to the cellular specificity of neurodegenerative disease and could be an early initiator of the pathophysiological cascades that underlie neurodegenerative disease. This concept is consistent with the fact that rare genetic mutations in some nucleoporins cause cell-type-specific neurological disease. In this Review, we discuss nucleoporin and NPC disruptions and consider their impact on cellular function and the pathophysiology of neurodegenerative disease.

Molecular crowding and RNA synergize to promote phase separation, microtubule interaction, and seeding of Tau condensates.

Biomolecular condensation of the neuronal microtubule‐associated protein Tau (MAPT) can be induced by coacervation with polyanions like RNA, or by molecular crowding. Tau condensates have been linked to both functional microtubule binding and pathological aggregation in neurodegenerative diseases. We find that molecular crowding and coacervation with RNA, two conditions likely coexisting in the cytosol, synergize to enable Tau condensation at physiological buffer conditions and to produce condensates with a strong affinity to charged surfaces. During condensate‐mediated microtubule polymerization, their synergy enhances bundling and spatial arrangement of microtubules. We further show that different Tau condensates efficiently induce pathological Tau aggregates in cells, including accumulations at the nuclear envelope that correlate with nucleocytoplasmic transport deficits. Fluorescent lifetime imaging reveals different molecular packing densities of Tau in cellular accumulations and a condensate‐like density for nuclear‐envelope Tau. These findings suggest that a complex interplay between interaction partners, post‐translational modifications, and molecular crowding regulates the formation and function of Tau condensates. Conditions leading to prolonged existence of Tau condensates may induce the formation of seeding‐competent Tau and lead to distinct cellular Tau accumulations.

Downstream events initiated by expression of FSHD-associated DUX4: Studies of nucleocytoplasmic transport, γH2AX accumulation, and Bax/Bak-dependence

ABSTRACTAbnormal expression in skeletal muscle of the double homeobox transcription factor DUX4 underlies pathogenesis in facioscapulohumeral muscular dystrophy (FSHD). Though multiple changes are known to be initiated by aberrant DUX4 expression, the downstream events initiated by DUX4 remain incompletely understood. In this study, we examined plausible downstream events initiated by DUX4. First, we found that nucleocytoplasmic protein export appeared to be decreased upon DUX4 expression as indicated by nuclear accumulation of a shuttle-GFP reporter. Second, building on studies from other labs, we showed that phospho(Ser139)-H2AX (γH2AX), an indicator of double-strand DNA breaks, accumulated both in human FSHD1 myotube nuclei upon endogenous DUX4 expression and in Bax-/-;Bak-/- (double knockout), SV40-immortalized mouse embryonic fibroblasts upon exogenous DUX4 expression. In contrast, DUX4-induced caspase 3/7 activation was prevented in Bax-/-;Bak-/- double knockout SV40-MEFs, but not by single knockouts of Bax, Bak, or Bid. Thus, aberrant DUX4 expression appeared to alter nucleocytoplasmic protein transport and generate double-strand DNA breaks in FSHD1 myotube nuclei, and the Bax/Bak pathway is required for DUX4-induced caspase activation but not γH2AX accumulation. These results add to our knowledge of downstream events induced by aberrant DUX4 expression and suggest possibilities for further mechanistic investigation.

The interaction between S100A2 and KPNA2 mediates NFYA nuclear import and is a novel therapeutic target for colorectal cancer metastasis.

Nucleocytoplasmic transport of proteins is disrupted and dysregulated in cancer cells. Nuclear pore complexes and cargo proteins are two main transportation regulators. However, the mechanism regulating nucleocytoplasmic transport in cancer remains elusive. Here, we identified a S100A2/KPNA2 cotransport complex that transports the tumor-associated transcription factor NFYA in colorectal cancer (CRC). Through the S100A2/KNPA2 complex, depending on its interaction with S100A2, NFYA is transported to the nucleus and inhibits the transcriptional activity of E-cadherin, which in turn promotes CRC metastasis. Targeting the S100A2/KPNA2 binding sites with the specific inhibitor delanzomib is a potential therapeutic approach for CRC.

Systemic Profiling of KDM5 Subfamily Signature in Non-Small-Cell Lung Cancer.

BackgroundDespite improvements in diagnosis and treatment, lung cancer is one of the most lethal human diseases, with a dismal 5-year relative survival rate of only 5% for patients diagnosed with advanced metastatic disease. Accumulating evidence supports that epigenetic aberration of histone demethylase-KDM5 subfamily is linked to human pan-cancer. However, the detailed functions of KDM5 proteins in lung cancer, especially in non-small-cell lung cancer (NSCLC), remain poorly understand.MethodsUALCAN, GEPIA, Kaplan–Meier plotter, cBioPortal, TIMER, TISIDB, and STRING databases were utilized in this investigation.ResultsWe detected varying degrees of gene mutations of KDM5 subfamily members and found that KDM5B/C were remarkably overexpressed in LUAD and LUSC compared to normal tissues. Different from KDM5D, positive relationship was shown between overall survival and mRNA expression of KDM5A/B/C in lung cancer. We determined that KDM5A/B/C expression levels were positively correlated with CD4+ T cells infiltration, especially immunological markers of Tregs and Th17 cells. Moreover, LUAD and LUSC were separately rich in inflammatory and wound healing subtypes after immunogenomics analyzing with respect to KDM5 subfamily overexpression. And with their 120 co-expressed genes, we revealed that nucleocytoplasmic transport and cellular protein localization-related genes were closely connected to KDM5 subfamily alterations, next to chromatin remodeling genes.ConclusionWe formulated the immune-infiltrating and prognostic value of KDM5 subfamily and highlighted its promising role in immune-inflammatory interaction with tumour microenvironment in NSCLC.

Mislocalization of Nucleocytoplasmic Transport Proteins in Human Huntington's Disease PSC-Derived Striatal Neurons.

Huntington’s disease (HD) is an inherited neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin gene (HTT). Disease progression is characterized by the loss of vulnerable neuronal populations within the striatum. A consistent phenotype across HD models is disruption of nucleocytoplasmic transport and nuclear pore complex (NPC) function. Here we demonstrate that high content imaging is a suitable method for detecting mislocalization of lamin-B1, RAN and RANGAP1 in striatal neuronal cultures thus allowing a robust, unbiased, highly powered approach to assay nuclear pore deficits. Furthermore, nuclear pore deficits extended to the selectively vulnerable DARPP32 + subpopulation neurons, but not to astrocytes. Striatal neuron cultures are further affected by changes in gene and protein expression of RAN, RANGAP1 and lamin-B1. Lowering total HTT using HTT-targeted anti-sense oligonucleotides partially restored gene expression, as well as subtly reducing mislocalization of proteins involved in nucleocytoplasmic transport. This suggests that mislocalization of RAN, RANGAP1 and lamin-B1 cannot be normalized by simply reducing expression of CAG-expanded HTT in the absence of healthy HTT protein.

Formation of Non-Nucleoplasmic Proteasome Foci during the Late Stage of Hyperosmotic Stress.

Cellular stress induces the formation of membraneless protein condensates in both the nucleus and cytoplasm. The nucleocytoplasmic transport of proteins mainly occurs through nuclear pore complexes (NPCs), whose efficiency is affected by various stress conditions. Here, we report that hyperosmotic stress compartmentalizes nuclear 26S proteasomes into dense nuclear foci, independent of signaling cascades. Most of the proteasome foci were detected between the condensed chromatin mass and inner nuclear membrane. The proteasome-positive puncta were not colocalized with other types of nuclear bodies and were reversibly dispersed when cells were returned to the isotonic medium. The structural integrity of 26S proteasomes in the nucleus was slightly affected under the hyperosmotic condition. We also found that these insulator-body-like proteasome foci were possibly formed through disrupted nucleus-to-cytosol transport, which was mediated by the sequestration of NPC components into osmostress-responding stress granules. These data suggest that phase separation in both the nucleus and cytosol may be a major cell survival mechanism during hyperosmotic stress conditions.

Multiple pathways of toxicity induced by C9orf72 dipeptide repeat aggregates and G4C2 RNA in a cellular model.

The most frequent genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia is a G4C2 repeat expansion in the C9orf72 gene. This expansion gives rise to translation of aggregating dipeptide repeat (DPR) proteins, including poly-GA as the most abundant species. However, gain of toxic function effects have been attributed to either the DPRs or the pathological G4C2 RNA. Here, we analyzed in a cellular model the relative toxicity of DPRs and RNA. Cytoplasmic poly-GA aggregates, generated in the absence of G4C2 RNA, interfered with nucleocytoplasmic protein transport, but had little effect on cell viability. In contrast, nuclear poly-GA was more toxic, impairing nucleolar protein quality control and protein biosynthesis. Production of the G4C2 RNA strongly reduced viability independent of DPR translation and caused pronounced inhibition of nuclear mRNA export and protein biogenesis. Thus, while the toxic effects of G4C2 RNA predominate in the cellular model used, DPRs exert additive effects that may contribute to pathology.

Traumatic injury compromises nucleocytoplasmic transport and leads to TDP-43 pathology.

Traumatic brain injury (TBI) is a predisposing factor for many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and chronic traumatic encephalopathy (CTE). Although defects in nucleocytoplasmic transport (NCT) is reported ALS and other neurodegenerative diseases, whether defects in NCT occur in TBI remains unknown. We performed proteomic analysis on Drosophila exposed to repeated TBI and identified resultant alterations in several novel molecular pathways. TBI upregulated nuclear pore complex (NPC) and nucleocytoplasmic transport (NCT) proteins as well as alter nucleoporin stability. Traumatic injury disrupted RanGAP1 and NPC protein distribution in flies and a rat model and led to coaggregation of NPC components and TDP-43. In addition, trauma-mediated NCT defects and lethality are rescued by nuclear export inhibitors. Importantly, genetic upregulation of nucleoporins in vivo and in vitro triggered TDP-43 cytoplasmic mislocalization, aggregation, and altered solubility and reduced motor function and lifespan of animals. We also found NUP62 pathology and elevated NUP62 concentrations in postmortem brain tissues of patients with mild or severe CTE as well as co-localization of NUP62 and TDP-43 in CTE. These findings indicate that TBI leads to NCT defects, which potentially mediate the TDP-43 pathology in CTE.