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The nuclear lamina is a dense network of intermediate filaments beneath the inner nuclear membrane. Composed of A-type lamins (lamin A/C) and B-type lamins (lamins B1 and B2), the nuclear lamina provides a scaffold for the nuclear envelope and chromatin, thereby maintaining the structural integrity of the nucleus. A-type lamins are also found inside the nucleus where they interact with chromatin and participate in gene regulation. Viruses replicating in the cell nucleus have to overcome the nuclear envelope during the initial phase of infection and during the nuclear egress of viral progeny. Here, we focused on the role of lamins in the replication cycle of a dsDNA virus, mouse polyomavirus. We detected accumulation of the major capsid protein VP1 at the nuclear periphery, defects in nuclear lamina staining and different lamin A/C phosphorylation patterns in the late phase of mouse polyomavirus infection, but the nuclear envelope remained intact. An absence of lamin A/C did not affect the formation of replication complexes but did slow virus propagation. Based on our findings, we propose that the nuclear lamina is a scaffold for replication complex formation and that lamin A/C has a crucial role in the early phases of infection with mouse polyomavirus.

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Senescence of nondividing neurons remains an immature concept, with especially the regulatory molecular mechanisms of senescence-like phenotypes and the role of proteins associated with neurodegenerative diseases in triggering neuronal senescence remaining poorly explored. In this study, we reveal that the nucleolar polyglutamine binding protein 3 (PQBP3; also termed NOL7), which has been linked to polyQ neurodegenerative diseases, regulates senescence as a gatekeeper of cytoplasmic DNA leakage. PQBP3 directly binds PSME3 (proteasome activator complex subunit 3), a subunit of the 11S proteasome regulator complex, decreasing PSME3 interaction with Lamin B1 and thereby preventing Lamin B1 degradation and senescence. Depletion of endogenous PQBP3 causes nuclear membrane instability and release of genomic DNA from the nucleus to the cytosol. Among multiple tested polyQ proteins, ataxin-1 (ATXN1) partially sequesters PQBP3 to inclusion bodies, reducing nucleolar PQBP3 levels. Consistently, knock-in mice expressing mutant Atxn1 exhibit decreased nuclear PQBP3 and a senescence phenotype in Purkinje cells of the cerebellum. Collectively, these results suggest homologous roles of the nucleolar protein PQBP3 in cellular senescence and neurodegeneration.

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Annexin A11 mutations are a rare cause of amyotrophic lateral sclerosis (ALS), wherein replicated protein variants P36R, G38R, D40G and D40Y are located in a small-alpha helix within the long, disordered N-terminus. To elucidate disease mechanisms, we characterised the phenotypes induced by a genetic loss of function (LoF) and by misexpression of G38R and D40G in vivo. Loss of Annexin A11 results in a low-penetrant behavioural phenotype and aberrant axonal morphology in zebrafish homozygous knockout larvae, which is rescued by human WT Annexin A11. Both Annexin A11 knockout/down and ALS variants trigger nuclear dysfunction characterised by Lamin B2 mis-localisation. The Lamin B2 signature also presented in anterior horn, spinal cord neurons from post-mortem ALS+/-FTD patient tissue possessing G38R and D40G protein variants. These findings suggest mutant Annexin A11 acts as a dominant negative, revealing a potential early nucleopathy highlighting nuclear envelope abnormalities preceding behavioural abnormality in animal models.

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Epigenetic modifications play an important role in cellular senescence, and enhancer of zeste homolog 2 (EZH2) is a key methyltransferase involved in epigenetic remodeling in multiple myeloma (MM) cells. We have previously demonstrated that GSK126, a specific EZH2 inhibitor, exhibits anti-MM therapeutic efficacy and safety in vivo and in vitro; however, its specific mechanism remains unclear. This study shows that GSK126 induces cellular senescence in MM, which is characterized by the accumulation of senescence-associated heterochromatin foci (SAHF) and p21, and increased senescence-associated ß galactosidase activity. Furthermore, EZH2 is inhibited in ribonucleotide reductase regulatory subunit M2 (RRM2)-overexpressing OCI-MY5 and RPMI-8226 cells. RRM2 overexpression inhibits the methyltransferase function of EZH2 and promotes its degradation through the ubiquitin-proteasome pathway, thereby inducing cellular senescence. In this senescence model, Lamin B1, a key component of the nuclear envelope and a marker of senescence, does not decrease but instead undergoes aberrant accumulation. Meanwhile, phosphorylation of extracellular signal-regulated protein kinase (ERK1/2) is significantly increased. The inhibition of ERK1/2 phosphorylation in turn partially restores Lamin B1 level and alleviates senescence. These findings suggest that EZH2 inhibition increases Lamin B1 level and induces senescence by promoting ERK1/2 phosphorylation. These data indicate that EZH2 plays an important role in MM cellular senescence and provide insights into the relationships among Lamin B1, p-ERK1/2, and cellular senescence.

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Cellular immortalization is a complex process that requires multiple genetic alterations to overcome restricting barriers, including senescence. Not surprisingly, many of these alterations are associated with cancer; two tumor suppressor pathways, the cellular tumor antigen p53 and p16-Retinoblastoma (RB) pathways, are the best-characterized examples, but their mutations alone are known to be insufficient to drive full immortalization. En et al. identified a role for the lamin B receptor (LBR) in promoting cellular proliferation and immortalization in p53- and RB-deficient cells by maintaining their genome integrity and suppressing senescence. Thus, modulation of LBR could be exploited to treat cancer and potentially also to promote cell rejuvenation.

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Platycodi radix is a widely used herbal medicine that contains numerous phytochemicals beneficial to health. The health and biological benefits of P. radix have been found across various diseases. The utilization of umbilical cord stromal stem cells, derived from Wharton's jelly of the human umbilical cord, has emerged as a promising approach for treating degenerative diseases. Nevertheless, growing evidence indicates that the function of stem cells declines with age, thereby limiting their regenerative capacity. The primary objective in this study is to investigate the beneficial effects of P. radix in senescent stem cells. We conducted experiments to showcase that diminished levels of Lamin B1 and Sox-2, along with an elevation in p21, which serve as indicative markers for the senescent stem cells. Our findings revealed the loss of Lamin B1 and Sox-2, coupled with an increase in p21, in umbilical cord stromal stem cells subjected to a low-dose (0.1 µM) doxorubicin (Dox) stimulation. However, P. radix restored the Dox-damage in the umbilical cord stromal stem cells. P. radix reversed the senescent conditions when the umbilical cord stromal stem cells exposed to Dox-induced reactive oxygen species (ROS) and mitochondrial membrane potential are significantly changed. In Dox-challenged aged umbilical cord stromal stem cells, P. radix reduced senescence, increased longevity, prevented mitochondrial dysfunction and ROS and protected against senescence-associated apoptosis. This study suggests that P. radix might be as a therapeutic and rescue agent for the aging effect in stem cells. Inhibition of cell death, mitochondrial dysfunction and aging-associated ROS with P. radix provides additional insights into the underlying molecular mechanisms.

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Human papillomavirus (HPV) infection is a primary cause of cervical and head-and-neck cancers. The HPV genome enters the nucleus during mitosis when the nuclear envelope disassembles. Given that lamins maintain nuclear integrity during interphase, we asked to what extent their loss would affect early HPV infection. To address this question, we infected human cervical cancer cells and keratinocytes lacking the major lamins with a HPV16 pseudovirus (HP-PsV) encoding an EGFP reporter. We found that a sustained reduction or complete loss of lamin B1 significantly increased HP-PsV infection rate. A corresponding greater nuclear HP-PsV load in LMNB1 knockout cells was directly related to their prolonged mitotic window and extensive nuclear rupture propensity. Despite the increased HP-PsV presence, EGFP transcript levels remained virtually unchanged, indicating an additional defect in protein turnover. Further investigation revealed that LMNB1 knockout led to a substantial decrease in autophagic capacity, possibly linked to the persistent activation of cGAS by cytoplasmic chromatin exposure. Thus, the attrition of lamin B1 increases nuclear perviousness and attenuates autophagic capacity, creating an environment conducive to unrestrained accumulation of HPV capsids. Our identification of lower lamin B1 levels and nuclear BAF foci in the basal epithelial layer of several human cervix samples suggests that this pathway may contribute to an increased individual susceptibility to HPV infection.

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Mammalian somatic cells undergo terminal proliferation arrest after a limited number of cell divisions, a phenomenon termed cellular senescence. However, cells acquire the ability to proliferate infinitely (cellular immortalization) through multiple genetic alterations. Inactivation of tumor suppressor genes such as p53, RB and p16 is important for cellular immortalization, although additional molecular alterations are required for cellular immortalization to occur. Here, we aimed to gain insights into these molecular alterations. Given that cellular immortalization is the escape of cells from cellular senescence, genes that regulate cellular senescence are likely to be involved in cellular immortalization. Because senescent cells show altered heterochromatin organization, we investigated the implications of lamin A/C, lamin B1 and lamin B receptor (LBR), which regulate heterochromatin organization, in cellular immortalization. We employed human immortalized cell lines, KMST-6 and SUSM-1, and found that expression of LBR was upregulated upon cellular immortalization and downregulated upon cellular senescence. In addition, knockdown of LBR induced cellular senescence with altered chromatin configuration. Additionally, enforced expression of LBR increased cell proliferation likely through suppression of genome instability in human primary fibroblasts that expressed the simian virus 40 large T antigen (TAg), which inactivates p53 and RB. Furthermore, expression of TAg or knockdown of p53 led to upregulated LBR expression. These observations suggested that expression of LBR might be upregulated to suppress genome instability in TAg-expressing cells, and, consequently, its upregulated expression assisted the proliferation of TAg-expressing cells (i.e. p53/RB-defective cells). Our findings suggest a crucial role for LBR in the process of cellular immortalization.

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Recent studies have shown that nucleophagy can mitigate DNA damage by selectively degrading nuclear components protruding from the nucleus. However, little is known about the role of nucleophagy in neurons after spinal cord injury (SCI). Western blot analysis and immunofluorescence were performed to evaluate the nucleophagy after nuclear DNA damage and leakage in SCI neurons in vivo and NSC34 expression in primary neurons cultured with oxygen-glucose deprivation (OGD) in vitro, as well as the interaction and colocalization of autophagy protein LC3 with nuclear lamina protein Lamin B1. The effect of UBC9, a Small ubiquitin-related modifier (SUMO) E2 ligase, on Lamin B1 SUMOylation and nucleophagy was examined by siRNA transfection or 2-D08 (a small-molecule inhibitor of UBC9), immunoprecipitation, and immunofluorescence. In SCI and OGD injured NSC34 or primary cultured neurons, neuronal nuclear DNA damage induced the SUMOylation of Lamin B1, which was required by the nuclear Lamina accumulation of UBC9. Furthermore, LC3/Atg8, an autophagy-related protein, directly bound to SUMOylated Lamin B1, and delivered Lamin B1 to the lysosome. Knockdown or suppression of UBC9 with siRNA or 2-D08 inhibited SUMOylation of Lamin B1 and subsequent nucleophagy and protected against neuronal death. Upon neuronal DNA damage and leakage after SCI, SUMOylation of Lamin B1 is induced by nuclear Lamina accumulation of UBC9. Furthermore, it promotes LC3-Lamin B1 interaction to trigger nucleophagy that protects against neuronal DNA damage.

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The prevalence of periodontitis increases with physiological aging. However, whether bacteria associated with periodontal diseases foster aging and the mechanisms by which they may do so are unknown. Herein, we hypothesize that Fusobacterium nucleatum, a microorganism associated with periodontitis and several other age-related disorders, triggers senescence, a chief hallmark of aging responsible to reduce tissue repair capacity. Our study analyzed the senescence response of gingival epithelial cells and their reparative capacity upon long-term exposure to F. nucleatum. Specifically, we assessed (a) cell cycle arrest by analyzing the cyclin-dependent kinase inhibitors p16INK4a and p14ARF and their downstream cascade (pRb, p53, and p21) at both gene and protein levels, (b) lysosomal mediated dysfunction by using assays targeting the expression and activity of the senescence-associated ß-galactosidase (SA-ß-Gal) enzyme, and (c) nuclear envelope breakdown by assessing the expression of Lamin-B1. The consequences of the senescence phenotype mediated by F. nucleatum were further assessed using wound healing assays. Our results revealed that prolonged exposure to F. nucleatum promotes an aging-like phenotype as evidenced by the increased expression of pro-senescence markers (p16INK4a , p21, and pRb) and SA-ß-Gal activity and reduced expression of the counter-balancing cascade (p14ARF and p53) and Lamin-B1. Furthermore, we also noted impaired wound healing capacity of gingival epithelial cells upon prolong bacterial exposure, which was consistent with the senescence-induced phenotype. Together, our findings provide a proof-of-concept evidence that F. nucleatum triggers a pro-senescence response in gingival epithelial cells. This might affect periodontal tissue homeostasis by reducing its repair capacity and, consequently, increasing susceptibility to periodontitis during aging.

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Infrapatellar fat pad (IPFP) is closely associated with the development and progression of knee osteoarthritis (OA), but the underlying mechanism remains unclear. Here, it is find that IPFP from OA patients can secret small extracellular vesicles (sEVs) and deliver them into articular chondrocytes. Inhibition the release of endogenous osteoarthritic IPFP-sEVs by GW4869 significantly alleviated IPFP-sEVs-induced cartilage destruction. Functional assays in vitro demonstrated that IPFP-sEVs significantly promoted chondrocyte extracellular matrix (ECM) catabolism and induced cellular senescence. It is further demonstrated that IPFP-sEVs induced ECM degradation in human and mice cartilage explants and aggravated the progression of experimental OA in mice. Mechanistically, highly enriched let-7b-5p and let-7c-5p in IPFP-sEVs are essential to mediate detrimental effects by directly decreasing senescence negative regulator, lamin B receptor (LBR). Notably, intra-articular injection of antagomirs inhibiting let-7b-5p and let-7c-5p in mice increased LBR expression, suppressed chondrocyte senescence and ameliorated the progression of experimental OA model. This study uncovers the function and mechanism of the IPFP-sEVs in the progression of OA. Targeting IPFP-sEVs cargoes of let-7b-5p and let-7c-5p can provide a potential strategy for OA therapy.

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Aim To investigate the effect of quercetin on the aging model of bone marrow mesenchymal stem cells established under microgravity. Methods Using 3D gyroscope, a aging model of bone marrow mesenchymal stem cells was constructed, and after receiving quercetin and microgravity treatment, the anti-aging effect of the quercetin was evaluated by detecting related proteins and oxidation indexes. Results Compared to the control group, the expressions of age-related proteins p21, pi6, p53 and RB in the microgravity group significantly increased, while the expressions of cyclin D1 and lamin B1 significantly decreased, with statistical significance (P<0.05). In the microgravity group, mitochondrial membrane potential significantly decreased (P<0.05), ROS accumulation significantly increased (P <0.05), SOD content significantly decreased and MDA content significantly increased (P<0.05). Compared to the microgravity group, the expressions of age-related proteins p21, pi6, p53 and RB in the quercetin group significantly decreased, while the expressions of cyclin D1 and lamin B1 significantly increased, with statistical significance (P<0.05). In the quercetin group, mitochondrial membrane potential significantly increased (P<0.05), ROS accumulation significantly decreased (P<0.05), SOD content significantly increased and MDA content significantly decreased (P<0.05). Conclusions Quercetin can resist oxidation, protect mitochondrial function and normal cell cycle, thus delaying the aging of bone marrow mesenchymal stem cells induced by microgravity.

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Aging is the result of a gradual functional decline at the cellular, and ultimately, organismal level, resulting in an increased risk of developing a variety of chronic illnesses, such as cardiovascular disease, stroke, cancer and diabetes. The skin is the largest organ of the human body, and the site where signs of aging are most visible. These signs include thin and dry skin, sagging, loss of elasticity, wrinkles, as well as aberrant pigmentation. The appearance of these features is accelerated by exposure to extrinsic factors such as ultraviolet (UV) radiation or pollution, as well as intrinsic factors including time, genetics, and hormonal changes. At the cellular level, aging is associated with impaired proteostasis and an accumulation of macromolecular damage, genomic instability, chromatin reorganization, telomere shortening, remodelling of the nuclear lamina, proliferation defects and premature senescence. Cellular senescence is a state of permanent growth arrest and a key hallmark of aging in many tissues. Due to their inability to proliferate, senescent cells no longer contribute to tissue repair or regeneration. Moreover, senescent cells impair tissue homeostasis, promote inflammation and extracellular matrix (ECM) degradation by secreting molecules collectively known as the "senescence-associated secretory phenotype" (SASP). Senescence can be triggered by a number of different stimuli such as telomere shortening, oncogene expression, or persistent activation of DNA damage checkpoints. As a result, these cells accumulate in aging tissues, including human skin. In this review, we focus on the role of cellular senescence during skin aging and the development of age-related skin pathologies, and discuss potential strategies to rejuvenate aged skin.

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Colorectal cancer (CRC) is among the most common malignancies worldwide. Although a recent study has shown that E3 ubiquitin ligases play a major role in regulating the occurrence and development of CRC, there are few reports on the role of the E3 ubiquitin ligase HECW2(HECT, C2 and WW domain containing E3 ubiquitin protein ligase 2) in CRC progression and chemoresistance. We found that HECW2 is highly expressed in CRC tissues. HECW2 knockdown inhibits CRC progression and chemoresistance, whereas HECW2 overexpression has the opposite effect. Mechanistically, HECW2 activates the AKT/mTOR signaling pathway by mediating the ubiquitin-proteasome degradation of lamin B1, thereby promoting CRC progression and chemoresistance. Our findings suggest that HECW2 may be a promising novel therapeutic target for CRC treatment.

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Forkhead box D1 (FOXD1) expression is upregulated in various types of human cancer. To the best of our knowledge, the roles of FOXD1 in prostate cancer (PC) remain largely unknown. The Cancer Genome Atlas dataset was used for the bioinformatics analysis of FOXD1 in PC. FOXD1 expression levels in normal immortalized human prostate epithelial cells (RWPE-1) and prostate cancer cells were detected by reverse transcription-quantitative PCR. PC cell viability was detected using Cell Counting Kit-8 assay. Transwell assays were performed to assess the migration and invasion of PC cells. Luciferase reporter gene assay was used to validate the association between FOXD1 and lamin (LMN)B1. LMNB1 is an important part of the cytoskeleton, which serves an important role in the process of tumor occurrence and development, regulating apoptosis and DNA repair. FOXD1 expression was upregulated in PC tissues, with its high expression being associated with clinical stage and survival in PC. Knockdown of FOXD1 inhibited viability, migration and invasion of PC cells. FOXD1 positively regulated LMNB1 expression. The effect of FOXD1 knockdown on PC cells was reversed by LMNB1 overexpression. In conclusion, FOXD1, positively regulated by LMNB1, served as an oncogene in PC and may be a potential biomarker and treatment target for PC.

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The role of lamin B1 in human health and aging has attracted increasing attention as mounting evidence reveals its significance in diverse cellular processes. Both upregulation and downregulation of lamin B1 have been implicated in age-associated organ dysfunctions and various human diseases, including central nervous system disorders. Additionally, lamin B1 levels undergo alterations in cancer cells, and a tumor-specific association exists between lamin B1 abundance and cancer aggressiveness. Investigating the connectivity between lamin B1 abundance and human health is of utmost importance for further research. This review presents recent advancements in understanding lamin B1's role in nuclear lamina function and its implications for human health.

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Lamin B1 is an essential protein of the nuclear lamina that plays a crucial role in nuclear function and organization. It has been demonstrated that lamin B1 is essential for organogenesis and particularly brain development. The important role of lamin B1 in physiological brain development and aging has only recently been at the epicenter of attention and is yet to be fully elucidated. Regarding the development of brain, glial cells that have long been considered as supporting cells to neurons have overturned this representation and current findings have displayed their active roles in neurogenesis and cerebral development. Although lamin B1 has increased levels during the differentiation of the brain cells, during aging these levels drop leading to senescent phenotypes and inciting neurodegenerative disorders such as Alzheimer's and Parkinson's disease. On the other hand, overexpression of lamin B1 leads to the adult-onset neurodegenerative disease known as Autosomal Dominant Leukodystrophy. This review aims at highlighting the importance of balancing lamin B1 levels in glial cells and neurons from brain development to aging.

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Autosomal dominant leukodystrophy (ADLD) is an ultra-rare, slowly progressive, and fatal neurodegenerative disorder associated with the loss of white matter in the central nervous system (CNS). Several years after its first clinical description, ADLD was found to be caused by coding and non-coding variants in the LMNB1 gene that cause its overexpression in at least the brain of patients. LMNB1 encodes for Lamin B1, a protein of the nuclear lamina. Lamin B1 regulates many cellular processes such as DNA replication, chromatin organization, and senescence. However, its functions have not been fully characterized yet. Nevertheless, Lamin B1 together with the other lamins that constitute the nuclear lamina has firstly the key role of maintaining the nuclear structure. Being the nucleus a dynamic system subject to both biochemical and mechanical regulation, it is conceivable that changes to its structural homeostasis might translate into functional alterations. Under this light, this review aims at describing the pieces of evidence that to date have been obtained regarding the effects of LMNB1 overexpression on cellular morphology and functionality. Moreover, we suggest that further investigation on ADLD morpho-functional consequences is essential to better understand this complex disease and, possibly, other neurological disorders affecting CNS myelination.

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To facilitate survival, replication, and dissemination, the intracellular pathogen Legionella pneumophila relies on its unique type IVB secretion system (T4SS) to deliver over 330 effectors to hijack host cell pathways in a spatiotemporal manner. The effectors and their host targets are largely unexplored due to their low sequence identity to the known proteins and functional redundancy. The T4SS effector SidN (Lpg1083) is secreted into host cells during the late infection period. However, to the best of our knowledge, the molecular characterization of SidN has not been studied. Herein, we identified SidN as a nuclear envelope-localized effector. Its structure adopts a novel fold, and the N-terminal domain is crucial for its specific subcellular localization. Furthermore, we found that SidN is transported by eukaryotic karyopherin Importin-13 into the nucleus, where it attaches to the N-terminal region of Lamin-B2 to interfere with the integrity of the nuclear envelope, causing nuclear membrane disruption and eventually cell death. Our work provides new insights into the structure and function of an L. pneumophila effector protein, and suggests a potential strategy utilized by the pathogen to promote host cell death and then escape from the host for secondary infection.

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