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The Journal of Cell Biology Dec 2019Mammalian cells frequently migrate through tight spaces during normal embryogenesis, wound healing, diapedesis, or in pathological situations such as metastasis. Nuclear...
Mammalian cells frequently migrate through tight spaces during normal embryogenesis, wound healing, diapedesis, or in pathological situations such as metastasis. Nuclear size and shape are important factors in regulating the mechanical properties of cells during their migration through such tight spaces. At the onset of migratory behavior, cells often initiate the expression of vimentin, an intermediate filament protein that polymerizes into networks extending from a juxtanuclear cage to the cell periphery. However, the role of vimentin intermediate filaments (VIFs) in regulating nuclear shape and mechanics remains unknown. Here, we use wild-type and vimentin-null mouse embryonic fibroblasts to show that VIFs regulate nuclear shape and perinuclear stiffness, cell motility in 3D, and the ability of cells to resist large deformations. These changes increase nuclear rupture and activation of DNA damage repair mechanisms, which are rescued by exogenous reexpression of vimentin. Our findings show that VIFs provide mechanical support to protect the nucleus and genome during migration.
Topics: Animals; Cell Movement; Cell Nucleus; Collagen; Cytoskeleton; DNA Damage; Fibroblasts; Intermediate Filament Proteins; Intermediate Filaments; Mice; Microscopy, Atomic Force; Microscopy, Confocal; Necrosis; Vimentin
PubMed: 31676718
DOI: 10.1083/jcb.201902046 -
BioEssays : News and Reviews in... Feb 2024Transport of macromolecules from the nucleus to the cytoplasm is essential for nearly all cellular and developmental events, and when mis-regulated, is associated with...
Transport of macromolecules from the nucleus to the cytoplasm is essential for nearly all cellular and developmental events, and when mis-regulated, is associated with diseases, tumor formation/growth, and cancer progression. Nuclear Envelope (NE)-budding is a newly appreciated nuclear export pathway for large macromolecular machineries, including those assembled to allow co-regulation of functionally related components, that bypasses canonical nuclear export through nuclear pores. In this pathway, large macromolecular complexes are enveloped by the inner nuclear membrane, transverse the perinuclear space, and then exit through the outer nuclear membrane to release its contents into the cytoplasm. NE-budding is a conserved process and shares many features with nuclear egress mechanisms used by herpesviruses. Despite its biological importance and clinical relevance, little is yet known about the regulatory and structural machineries that allow NE-budding to occur in any system. Here we summarize what is currently known or proposed for this intriguing nuclear export process.
Topics: Nuclear Envelope; Active Transport, Cell Nucleus; Herpesviridae; Cytoplasm; Cell Nucleus
PubMed: 38044581
DOI: 10.1002/bies.202300182 -
Investigative Ophthalmology & Visual... Apr 2024To undertake the first ultrastructural characterization of human retinal pigment epithelial (RPE) differentiation from fetal development to adolescence.
PURPOSE
To undertake the first ultrastructural characterization of human retinal pigment epithelial (RPE) differentiation from fetal development to adolescence.
METHODS
Ten fetal eyes and three eyes aged six, nine, and 17 years were examined in the temporal retina adjacent to the optic nerve head by transmission electron microscopy. The area, number, and distribution of RPE organelles were quantified and interpreted within the context of adjacent photoreceptors, Bruch's membrane, and choriocapillaris maturation.
RESULTS
Between eight to 12 weeks' gestation (WG), pseudostratified columnar epithelia with apical tight junctions differentiate to a simple cuboidal epithelium with random distribution of melanosomes and mitochondria. Between 12 to 26 WG, cells enlarge and show long apical microvilli and apicolateral junctional complexes. Coinciding with eye opening at 26 WG, melanosomes migrate apically whereas mitochondria distribute to perinuclear regions, with the first appearance of phagosomes, complex granules, and basolateral extracellular space (BES) formation. Significantly, autophagy and heterophagy, as evidenced by organelle recycling, and the gold standard of ultrastructural evidence for autophagy of double-membrane autophagosomes and mitophagosomes were evident from 32 WG, followed by basal infoldings of RPE cell membrane at 36 WG. Lipofuscin formation and deposition into the BES evident at six years increased at 17 years.
CONCLUSIONS
We provide compelling ultrastructural evidence that heterophagy and autophagy begins in the third trimester of human fetal development and that deposition of cellular byproducts into the extracellular space of RPE takes place via exocytosis. Transplanted RPE cells must also demonstrate the capacity to subserve autophagic and heterophagic functions for effective disease mitigation.
Topics: Humans; Retinal Pigment Epithelium; Adolescent; Autophagy; Microscopy, Electron, Transmission; Child; Lipofuscin; Exocytosis; Extracellular Space; Gestational Age; Female; Male; Fetal Development; Mitochondria; Cell Differentiation
PubMed: 38648041
DOI: 10.1167/iovs.65.4.32 -
Journal of Virology May 2022This study developed a system consisting of two rounds of screening cellular proteins involved in the nuclear egress of herpes simplex virus 1 (HSV-1). Using this...
This study developed a system consisting of two rounds of screening cellular proteins involved in the nuclear egress of herpes simplex virus 1 (HSV-1). Using this system, we first screened cellular proteins that interacted with the HSV-1 nuclear egress complex (NEC) consisting of UL34 and UL31 in HSV-1-infected cells, which are critical for the nuclear egress of HSV-1, by tandem affinity purification coupled with mass spectrometry-based proteomics technology. Next, we performed CRISPR/Cas9-based screening of live HSV-1-infected reporter cells under fluorescence microscopy using single guide RNAs targeting the cellular proteins identified in the first proteomic screening to detect the mislocalization of the lamin-associated protein emerin, which is a phenotype for defects in HSV-1 nuclear egress. This study focused on a cellular orphan transporter SLC35E1, one of the cellular proteins identified by the screening system. Knockout of SLC35E1 reduced HSV-1 replication and induced membranous invaginations containing perinuclear enveloped virions (PEVs) adjacent to the nuclear membrane (NM), aberrant accumulation of PEVs in the perinuclear space between the inner and outer NMs and the invagination structures, and mislocalization of the NEC. These effects were similar to those of previously reported mutation(s) in HSV-1 proteins and depletion of cellular proteins that are important for HSV-1 de-envelopment, one of the steps required for HSV-1 nuclear egress. Our newly established screening system enabled us to identify a novel cellular protein required for efficient HSV-1 de-envelopment. The identification of cellular protein(s) that interact with viral effector proteins and function in important viral procedures is necessary for enhancing our understanding of the mechanics of various viral processes. In this study, we established a new system consisting of interactome screening for the herpes simplex virus 1 (HSV-1) nuclear egress complex (NEC), followed by loss-of-function screening to target the identified putative NEC-interacting cellular proteins to detect a defect in HSV-1 nuclear egress. This newly established system identified SLC35E1, an orphan transporter, as a novel cellular protein required for efficient HSV-1 de-envelopment, providing an insight into the mechanisms involved in this viral procedure.
Topics: Animals; CRISPR-Cas Systems; Chlorocebus aethiops; Gene Knockout Techniques; HEK293 Cells; HeLa Cells; Herpesvirus 1, Human; Humans; Membrane Transport Proteins; Nuclear Envelope; Nuclear Proteins; Proteomics; Vero Cells; Viral Proteins; Virus Release
PubMed: 35475666
DOI: 10.1128/jvi.00306-22 -
ELife Dec 2020The inner nuclear membrane is functionalized by diverse transmembrane proteins that associate with nuclear lamins and/or chromatin. When cells enter mitosis,...
The inner nuclear membrane is functionalized by diverse transmembrane proteins that associate with nuclear lamins and/or chromatin. When cells enter mitosis, membrane-chromatin contacts must be broken to allow for proper chromosome segregation; yet how this occurs remains ill-understood. Unexpectedly, we observed that an imbalance in the levels of the lamina-associated polypeptide 1 (LAP1), an activator of ER-resident Torsin AAA+-ATPases, causes a failure in membrane removal from mitotic chromatin, accompanied by chromosome segregation errors and changes in post-mitotic nuclear morphology. These defects are dependent on a hitherto unknown chromatin-binding region of LAP1 that we have delineated. LAP1-induced NE abnormalities are efficiently suppressed by expression of wild-type but not ATPase-deficient Torsins. Furthermore, a dominant-negative Torsin induces chromosome segregation defects in a LAP1-dependent manner. These results indicate that association of LAP1 with chromatin in the nucleus can be modulated by Torsins in the perinuclear space, shedding new light on the LAP1-Torsin interplay.
Topics: Adenosine Triphosphatases; Carrier Proteins; Cell Line, Tumor; Chromatin; Chromosome Segregation; Gene Knockout Techniques; HCT116 Cells; HSC70 Heat-Shock Proteins; HeLa Cells; Hep G2 Cells; Humans; Mitosis; Molecular Chaperones; Nuclear Envelope
PubMed: 33320087
DOI: 10.7554/eLife.63614 -
Cells Mar 2020Newly assembled herpesvirus nucleocapsids traverse the intact nuclear envelope by a vesicle-mediated nucleo-cytoplasmic transport for final virion maturation in the...
Newly assembled herpesvirus nucleocapsids traverse the intact nuclear envelope by a vesicle-mediated nucleo-cytoplasmic transport for final virion maturation in the cytoplasm. For this, they bud at the inner nuclear membrane resulting in primary enveloped particles in the perinuclear space (PNS) followed by fusion of the primary envelope with the outer nuclear membrane (ONM). While the conserved viral nuclear egress complex orchestrates the first steps, effectors of fusion of the primary virion envelope with the ONM are still mostly enigmatic but might include cellular proteins like SUN2 or ESCRT-III components. Here, we analyzed the influence of the only known AAA+ ATPases located in the endoplasmic reticulum and the PNS, the Torsins (Tor), on nuclear egress of the alphaherpesvirus pseudorabies virus. For this overexpression of wild type and mutant proteins as well as CRISPR/Cas9 genome editing was applied. Neither single overexpression nor gene knockout (KO) of TorA or TorB had a significant impact. However, TorA/B double KO cells showed decreased viral titers at early time points of infection and an accumulation of primary virions in the PNS pointing to a delay in capsid release during nuclear egress.
Topics: ATPases Associated with Diverse Cellular Activities; Active Transport, Cell Nucleus; Animals; Cell Nucleus; Cytoplasm; Herpesvirus 1, Suid; Molecular Chaperones; Nuclear Envelope; Rabbits; Viral Proteins; Virus Release
PubMed: 32192107
DOI: 10.3390/cells9030738 -
Breast Cancer Research : BCR May 2022CCR5 is a motility chemokine receptor implicated in tumor progression, whose activation and subsequent endocytosis may identify highly aggressive breast cancer cell...
BACKGROUND
CCR5 is a motility chemokine receptor implicated in tumor progression, whose activation and subsequent endocytosis may identify highly aggressive breast cancer cell subtypes likely to spread into the circulatory system.
METHODS
The MDA-MB-231 cell line was used to model and visualize CCR5 activation by stimulation with RANTES, in an effort to quantify CCR5 endocytosis from the cell surface to the perinuclear space. CCR5 expression was then examined in tumor-associated cells (TACs), consisting of circulating tumor cells and circulating stromal cells, isolated from the peripheral blood of 54 metastatic breast cancer (mBC) patients to evaluate these CCR5 pooling patterns as they relate to progression and survival over 2 years.
RESULTS
In MB231 experiments, it was observed that CCR5 formed ~ 1 micron clusters identified as "CCR5 pools" on the surface of the cell, which in the presence of RANTES were endocytosed and translocated to the cell cytoplasm. When TACs from patients were analyzed, CCR5 pools were observed on the cell surface and translocating to the nuclear area, with CCR5 also having a positive statistical correlation between increased numbers of TACs and increased CCR5 pools on the cells. Further, it was determined that patients with very high numbers of CCR5 (> 10 CCR5 pools), specifically in the circulating stromal cells, were associated with worse progression-free survival (hazard ratio = 4.5, p = 0.002) and worse overall survival (hazard ratio = 3.7, p = 0.014).
CONCLUSIONS
Using a liquid biopsy approach, we evaluated two populations of tumor-associated cells emanating from primary tumors, with data suggesting that upregulation of the motility chemokine CCR5 in TACs provides clinically relevant opportunities for treating and tracking drug targetable receptors in mBC.
Topics: Breast Neoplasms; Chemokine CCL5; Endocytosis; Female; Humans; Neoplastic Cells, Circulating; Receptors, CCR5
PubMed: 35606863
DOI: 10.1186/s13058-022-01528-w -
The Journal of Clinical Investigation Aug 2019Deciphering novel pathways regulating liver lipid content has profound implications for understanding the pathophysiology of nonalcoholic fatty liver disease and...
Deciphering novel pathways regulating liver lipid content has profound implications for understanding the pathophysiology of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Recent evidence suggests that the nuclear envelope is a site of regulation of lipid metabolism but there is limited appreciation of the responsible mechanisms and molecular components within this organelle. We showed that conditional hepatocyte deletion of the inner nuclear membrane protein lamina-associated polypeptide 1 (LAP1) caused defective VLDL secretion and steatosis, including intranuclear lipid accumulation. LAP1 binds to and activates torsinA, an AAA+ ATPase that resides in the perinuclear space and continuous main ER. Deletion of torsinA from mouse hepatocytes caused even greater reductions in VLDL secretion and profound steatosis. Both of these mutant mouse lines developed hepatic steatosis and subsequent steatohepatitis on a regular chow diet in the absence of whole-body insulin resistance or obesity. Our results establish an essential role for the nuclear envelope-localized torsinA-LAP1 complex in hepatic VLDL secretion and suggest that the torsinA pathway participates in the pathophysiology of nonalcoholic fatty liver disease.
Topics: Animals; Carrier Proteins; Hepatocytes; Lipid Metabolism; Lipoproteins, VLDL; Membrane Proteins; Mice; Mice, Knockout; Molecular Chaperones; Non-alcoholic Fatty Liver Disease; Nuclear Envelope
PubMed: 31408437
DOI: 10.1172/JCI129769 -
Rheumatology International Jul 2023The objective of this study was to investigate the effects of prolonged exposure to the oxidative agent NaClO on histopathological changes in the lung tissues of...
The objective of this study was to investigate the effects of prolonged exposure to the oxidative agent NaClO on histopathological changes in the lung tissues of laboratory animals. Specifically, the study aimed to examine morphological changes in the pulmonary microcirculation and the level of vascular cell adhesion molecule-1 (VCAM-1) as a functional activity indicator of endothelial cells in animals with induced systemic sclerosis (SSc). A laboratory animal model was used to assess the impact of long-term exposure to NaClO on lung tissues. The animals were divided into three groups: the experimental group (25 rats) was exposed to NaClO, while the control group (20 rats) received an isotonic solution, and the intact group (15 animals) was without any exposure. The concentration of VCAM-1 in the serum of the animals was measured using an enzyme-linked immunosorbent assay. Histopathological analysis of lung tissue specimens was performed using both light and electron microscopy. The concentration of VCAM-1 in the serum of the animals in the experimental group was significantly higher than that of the control group (91.25 [85.63-143.75] vs 19.50 [13.53-22.20], p < 0.05). The histopathological analysis revealed significant abnormalities in the lung tissue specimens from the experimental group, including disruption in the structure of the hemocapillaries of the lungs, narrowing of the microvessel lumen, and perivascular infiltration by polymorphonuclear cells. The electron microscopic analysis showed several ultrastructural changes in the endotheliocytes of the hemocapillaries, including uneven expansion of the perinuclear space, swollen mitochondria, and fragmentation of the membranes of the granular endoplasmic reticulum. Additionally, the basement membrane of hemocapillaries showed uneven thickening with indistinct contours, and the peripheral parts of endotheliocytes were marked by numerous micropinocytotic vesicles and vacuoles. Erythrocyte aggregates and leukocyte adhesion were identified in the lumen of many hemocapillaries, while adhesion and aggregation of platelets were also observed in several hemocapillaries. Long-term exposure to NaClO can cause significant histopathological changes in lung tissues, including damage to the hemocapillaries and disruption in the structure of endotheliocytes.
Topics: Rats; Animals; Endothelial Cells; Vascular Cell Adhesion Molecule-1; Lung; Neutrophils; Scleroderma, Systemic
PubMed: 37071178
DOI: 10.1007/s00296-023-05328-z -
Acta Histochemica Jul 2021Iron deficiency anemia (IDA) is a global health problem affecting various body systems and tissues including the cardiovascular system. Several literatures described the...
Iron deficiency anemia (IDA) is a global health problem affecting various body systems and tissues including the cardiovascular system. Several literatures described the associated physiological and clinical changes in the cardiovascular system and heart. However, the associated structural changes were poorly investigated. Therefore, the main aim of the present work was to elucidate whether IDA induces structural changes and alterations in the VEGF, CD34 and ASMA immunoexpression in the myocardium of albino rats. Thirty adult male albino rats were divided into two groups (fifteen rats each); control and anemic. Hematological data for all animals were assessed weekly and statistically analyzed. Three weeks later, animals were sacrificed, and heart specimens were obtained and processed for light and electron microscopy. All hematological parameters showed a statistically significant decrease in the anemic group. Structurally, the anemic group showed markedly degenerated, disrupted and disorganized cardiomyocytes in addition to markedly congested blood vessels, fibroblasts, collagen fibers deposition and perivascular cellular infiltration were noted. Also, positive immunostaining for VEGF, CD34 and ASMA was observed. Ultra-structurally, the myocardium of the anemic group showed disrupted and degenerated myofibrils with degenerated nuclei, perinuclear edema, widened interstitial spaces and marked collagen deposition. Mitochondria markedly increased with abnormal shapes. IDA induced myocardial injury that may propagate to regeneration through activated CD34 progenitor cells and increased VEGF or to degeneration and fibrosis through collagen fibers deposition and enhanced ASMA. So, early diagnosis and treatment of IDA is mandatory to avoid the associated myocardial structural changes.
Topics: Actins; Anemia, Iron-Deficiency; Animals; Antigens, CD34; Cell Differentiation; Collagen; Male; Mitochondria; Muscle, Smooth; Myocardium; Rats; Rats, Sprague-Dawley; Regeneration; Vascular Endothelial Growth Factor A
PubMed: 34052675
DOI: 10.1016/j.acthis.2021.151731