Spatial Actin Structure Does Not Correlate With Nuclear Organization

2013 ◽  
Author(s):  
Shin-Min Wen ◽  
Pen-hsiu Grace Chao
Keyword(s):  
Actin Cytoskeleton ◽  
Chromatin Condensation ◽  
Nuclear Shape ◽  
Nuclear Deformation ◽  
Linc Complex ◽  
Mechanical Coupling ◽  
Actin Structure ◽  
Actomyosin Cytoskeleton ◽  
Chromatin Density

Cells in situ exhibit a great variety of morphologies that intimately relates to phenotypic controls. Cell morphology regulates cytoskeletal organization, which in turn influences nuclear shape and organization [1–4]. The actomyosin cytoskeleton is connected to a structure known as the linker of nucleoskeleton and cytoskeleton (LINC) complex located on the nuclear membrane. LINC is believed to transmit deformation of the actin cytoskeleton into the nucleus and nucleoskeleton, change nuclear shape as well as chromatin conformation, and modulate gene expression [5, 6]. Khatau and coworkers reported a structure of apical actin dome, called the actin cap, that controls nuclear deformation through LINC [7]. In addition, actin stress fibers hves been shown to compress the nucleus laterally and increase chromatin condensation [4]. Based on these findings, we hypothesize that there is a spatial correlation between the actin cytoskeleton and chromatin density. In the current study, we investigated the role of actin cytoskeleton in nuclear deformation with respect to the z-axis. We found no spatial relationships between actin structure and nuclear deformation or chromatin condensation, suggesting that the actomyosin cytoskeleton acts globally to influence nuclear structure and additional structural components may contribute to the actin-nucleus mechanical coupling.

scholarly journals Changes in Nuclear Shape and Gene Expression in Response to Simulated Microgravity Are LINC Complex-Dependent

2020 ◽  
Vol 21 (18) ◽  
pp. 6762
Author(s):  
Srujana Neelam ◽  
Brian Richardson ◽  
Richard Barker ◽  
Ceasar Udave ◽  
Simon Gilroy ◽  
...  
Keyword(s):  
Gene Expression ◽  
Simulated Microgravity ◽  
Focal Adhesions ◽  
Nuclear Shape ◽  
Microgravity Environment ◽  
Dependent Manner ◽  
Linc Complex ◽  
Expression Of Genes ◽  
Differential Gene

Microgravity is known to affect the organization of the cytoskeleton, cell and nuclear morphology and to elicit differential expression of genes associated with the cytoskeleton, focal adhesions and the extracellular matrix. Although the nucleus is mechanically connected to the cytoskeleton through the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, the role of this group of proteins in these responses to microgravity has yet to be defined. In our study, we used a simulated microgravity device, a 3-D clinostat (Gravite), to investigate whether the LINC complex mediates cellular responses to the simulated microgravity environment. We show that nuclear shape and differential gene expression are both responsive to simulated microgravity in a LINC-dependent manner and that this response changes with the duration of exposure to simulated microgravity. These LINC-dependent genes likely represent elements normally regulated by the mechanical forces imposed by gravity on Earth.

scholarly journals Depletion of nucleophosmin leads to distortion of nucleolar and nuclear structures in HeLa cells

2008 ◽  
Vol 415 (3) ◽  
pp. 345-351 ◽  
Author(s):  
Mohammed Abdullahel Amin ◽  
Sachihiro Matsunaga ◽  
Susumu Uchiyama ◽  
Kiichi Fukui
Keyword(s):  
Cell Cycle ◽  
Hela Cells ◽  
Ribosome Biogenesis ◽  
Three Dimensional ◽  
Nuclear Shape ◽  
Nucleolar Structure ◽  
Cellular Processes ◽  
Actin Structure ◽  
Nuclear Structures

NPM (nucleophosmin; also known as B23) is an abundantly and ubiquitously expressed multifunctional nucleolar phosphoprotein, which is involved in numerous cellular processes, including ribosome biogenesis, protein chaperoning and centrosome duplication; however, the role of NPM in the cell cycle still remains unknown. In the present study, we show dynamic localization of NPM throughout the cell cycle of HeLa cells. Using a combination of RNAi (RNA interference) and three-dimensional microscopy we show that NPM is localized at the chromosome periphery during mitosis. We also demonstrate that depletion of NPM causes distortion of nucleolar structure as expected and leads to unexpected dramatic changes in nuclear morphology with multiple micronuclei formation. The defect in nuclear shape of NPM-depleted cells, which is clearly observed by live-cell imaging, is due to the distortion of cytoskeletal (α-tubulin and β-actin) structure, resulting from the defects in centrosomal microtubule nucleation. These results indicate that NPM is an essential protein not only for the formation of normal nucleolar structure, but also for the maintenance of regular nuclear shape in HeLa cells.

scholarly journals Junctional ER Organization Affects Mechanotransduction at Cadherin-Mediated Adhesions

2021 ◽  
Vol 9 ◽  
Author(s):  
Michelle Joy-Immediato ◽  
Manuel J. Ramirez ◽  
Mauricio Cerda ◽  
Yusuke Toyama ◽  
Andrea Ravasio ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Actin Cytoskeleton ◽  
Structural Organization ◽  
Adherens Junctions ◽  
Conformational State ◽  
Microtubule Network ◽  
Close Proximity ◽  
Actomyosin Cytoskeleton

Cadherin-mediated adhesions (also known as adherens junctions) are adhesive complexes that connect neighboring cells in a tissue. While the role of the actin cytoskeleton in withstanding tension at these sites of contact is well documented, little is known about the involvement of microtubules and the associated endoplasmic reticulum (ER) network in cadherin mechanotransduction. Therefore, we investigated how the organization of ER extensions in close proximity of cadherin-mediated adhesions can affect such complexes, and vice versa. Here, we show that the extension of the ER to cadherin-mediated adhesions is tension dependent and appears to be cadherin-type specific. Furthermore, the different structural organization of the ER/microtubule network seems to affect the localization of ER-bound PTP1B at cadherin-mediated adhesions. This phosphatase is involved in the modulation of vinculin, a molecular clutch which enables differential engagement of the cadherin-catenin layer with the actomyosin cytoskeleton in response to tension. This suggests a link between structural organization of the ER/microtubule network around cadherin-specific adhesions, to control the mechanotransduction of adherens junctions by modulation of vinculin conformational state.

Magnesium Chloride is an Effective Therapeutic Agent for Prostate Cancer

2018 ◽  
Vol 8 (1) ◽  
pp. 62 ◽  
Author(s):  
Julianna Maria Santos ◽  
Fazle Hussain
Keyword(s):  
Prostate Cancer ◽  
Magnesium Chloride ◽  
Epithelial Mesenchymal Transition ◽  
Chromatin Condensation ◽  
Myosin Ii ◽  
In Vivo Studies ◽  
Migration Speed ◽  
Mesenchymal Transition

Background: Reduced levels of magnesium can cause several diseases and increase cancer risk. Motivated by magnesium chloride’s (MgCl2) non-toxicity, physiological importance, and beneficial clinical applications, we studied its action mechanism and possible mechanical, molecular, and physiological effects in prostate cancer with different metastatic potentials.Methods: We examined the effects of MgCl2, after 24 and 48 hours, on apoptosis, cell migration, expression of epithelial mesenchymal transition (EMT) markers, and V-H+-ATPase, myosin II (NMII) and the transcription factor NF Kappa B (NFkB) expressions.Results: MgCl2 induces apoptosis, and significantly decreases migration speed in cancer cells with different metastatic potentials.  MgCl2 reduces the expression of V-H+-ATPase and myosin II that facilitates invasion and metastasis, suppresses the expression of vimentin and increases expression of E-cadherin, suggesting a role of MgCl2 in reversing the EMT. MgCl2 also significantly increases the chromatin condensation and decreases NFkB expression.Conclusions: These results suggest a promising preventive and therapeutic role of MgCl2 for prostate cancer. Further studies should explore extending MgCl2 therapy to in vivo studies and other cancer types.Keywords: Magnesium chloride, prostate cancer, migration speed, V-H+-ATPase, and EMT.

Membrane Homeostasis: The Role of Actin Cytoskeleton

2021 ◽  
Vol 101 (1) ◽  
pp. 81-95
Author(s):  
Arikta Biswas ◽  
Rinku Kumar ◽  
Bidisha Sinha
Keyword(s):  
Actin Cytoskeleton

scholarly journals Interactions between the WEE-1.3 kinase and the PAM-1 aminopeptidase in oocyte maturation and the early C. elegans embryo

2021 ◽  
Author(s):  
Dorothy Benton ◽  
Eva C Jaeger ◽  
Arielle Kilner ◽  
Ashley Kimble ◽  
Josh Lowry ◽  
...  
Keyword(s):  
Missense Mutation ◽  
Oocyte Maturation ◽  
Protective Role ◽  
C Elegans ◽  
Direct Target ◽  
The One ◽  
Actomyosin Cytoskeleton ◽  
Embryonic Viability ◽  
Anterior Posterior

Abstract Puromycin-sensitive aminopeptidases are found across phyla and are known to regulate the cell-cycle and play a protective role in neurodegenerative disease. PAM-1 is a puromycin-sensitive aminopeptidase important for meiotic exit and polarity establishment in the one-cell Caenorhabditis elegans embryo. Despite conservation of this aminopeptidase, little is known about its targets during development. In order to identify novel interactors, we conducted a suppressor screen and isolated four suppressing mutations in three genes that partially rescued the maternal-effect lethality of pam-1 mutants. Suppressed strains show improved embryonic viability and polarization of the anterior-posterior axis. We identified a missense mutation in wee-1.3 in one of these suppressed strains. WEE-1.3 is an inhibitory kinase that regulates maturation promoting factor. While the missense mutation suppressed polarity phenotypes in pam-1, it does so without restoring centrosome-cortical contact or altering the cortical actomyosin cytoskeleton. To see if PAM-1 and WEE-1.3 interact in other processes, we examined oocyte maturation. While depletion of wee-1.3 causes sterility due to precocious oocyte maturation, this effect was lessened in pam-1 worms, suggesting that PAM-1 and WEE-1.3 interact in this process. Levels of WEE-1.3 were comparable between wild-type and pam-1 strains, suggesting that WEE-1.3 is not a direct target of the aminopeptidase. Thus, we have established an interaction between PAM-1 and WEE-1.3 in multiple developmental processes and have identified suppressors that are likely to further our understanding of the role of puromycin-sensitive aminopeptidases during development.

scholarly journals AIF3 splicing switch triggers neurodegeneration

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Shuiqiao Liu ◽  
Mi Zhou ◽  
Zhi Ruan ◽  
Yanan Wang ◽  
Calvin Chang ◽  
...  
Keyword(s):  
Cell Death ◽  
Neurodegenerative Diseases ◽  
Mitochondrial Dysfunction ◽  
Nuclear Translocation ◽  
Chromatin Condensation ◽  
Neuronal Cell ◽  
Adult Brain ◽  
Postmortem Brain ◽  
Mitochondrial Functions

Abstract Background Apoptosis-inducing factor (AIF), as a mitochondrial flavoprotein, plays a fundamental role in mitochondrial bioenergetics that is critical for cell survival and also mediates caspase-independent cell death once it is released from mitochondria and translocated to the nucleus under ischemic stroke or neurodegenerative diseases. Although alternative splicing regulation of AIF has been implicated, it remains unknown which AIF splicing isoform will be induced under pathological conditions and how it impacts mitochondrial functions and neurodegeneration in adult brain. Methods AIF splicing induction in brain was determined by multiple approaches including 5′ RACE, Sanger sequencing, splicing-specific PCR assay and bottom-up proteomic analysis. The role of AIF splicing in mitochondria and neurodegeneration was determined by its biochemical properties, cell death analysis, morphological and functional alterations and animal behavior. Three animal models, including loss-of-function harlequin model, gain-of-function AIF3 knockin model and conditional inducible AIF splicing model established using either Cre-loxp recombination or CRISPR/Cas9 techniques, were applied to explore underlying mechanisms of AIF splicing-induced neurodegeneration. Results We identified a nature splicing AIF isoform lacking exons 2 and 3 named as AIF3. AIF3 was undetectable under physiological conditions but its expression was increased in mouse and human postmortem brain after stroke. AIF3 splicing in mouse brain caused enlarged ventricles and severe neurodegeneration in the forebrain regions. These AIF3 splicing mice died 2–4 months after birth. AIF3 splicing-triggered neurodegeneration involves both mitochondrial dysfunction and AIF3 nuclear translocation. We showed that AIF3 inhibited NADH oxidase activity, ATP production, oxygen consumption, and mitochondrial biogenesis. In addition, expression of AIF3 significantly increased chromatin condensation and nuclear shrinkage leading to neuronal cell death. However, loss-of-AIF alone in harlequin or gain-of-AIF3 alone in AIF3 knockin mice did not cause robust neurodegeneration as that observed in AIF3 splicing mice. Conclusions We identified AIF3 as a disease-inducible isoform and established AIF3 splicing mouse model. The molecular mechanism underlying AIF3 splicing-induced neurodegeneration involves mitochondrial dysfunction and AIF3 nuclear translocation resulting from the synergistic effect of loss-of-AIF and gain-of-AIF3. Our study provides a valuable tool to understand the role of AIF3 splicing in brain and a potential therapeutic target to prevent/delay the progress of neurodegenerative diseases.

scholarly journals Integrative and Comprehensive Pancancer Analysis of Regulator of Chromatin Condensation 1 (RCC1)

2021 ◽  
Vol 22 (14) ◽  
pp. 7374
Author(s):  
Changwu Wu ◽  
Yingjuan Duan ◽  
Siming Gong ◽  
Sonja Kallendrusch ◽  
Nikolas Schopow ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromatin Condensation ◽  
Treatment Strategies ◽  
Enrichment Analysis ◽  
Tissue Expression ◽  
The Cancer Genome Atlas ◽  
Malignant Neoplasms ◽  
Nucleotide Exchange ◽  
Genome Database

Regulator of Chromatin Condensation 1 (RCC1) is the only known guanine nucleotide exchange factor that acts on the Ras-like G protein Ran and plays a key role in cell cycle regulation. Although there is growing evidence to support the relationship between RCC1 and cancer, detailed pancancer analyses have not yet been performed. In this genome database study, based on The Cancer Genome Atlas, Genotype-Tissue Expression and Gene Expression Omnibus databases, the potential role of RCC1 in 33 tumors’ entities was explored. The results show that RCC1 is highly expressed in most human malignant neoplasms in contrast to healthy tissues. RCC1 expression is closely related to the prognosis of a broad variety of tumor patients. Enrichment analysis showed that some tumor-related pathways such as “cell cycle” and “RNA transport” were involved in the functional mechanism of RCC1. In particular, the conducted analysis reveals the relation of RCC1 to multiple immune checkpoint genes and suggests that the regulation of RCC1 is closely related to tumor infiltration of cancer-associated fibroblasts and CD8+ T cells. Coherent data demonstrate the association of RCC1 with the tumor mutation burden and microsatellite instability in various tumors. These findings provide new insights into the role of RCC1 in oncogenesis and tumor immunology in various tumors and indicate its potential as marker for therapy prognosis and targeted treatment strategies.

scholarly journals Prolactin and Male Fertility: The Long and Short Feedback Regulation

2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
M. K. Gill-Sharma
Keyword(s):  
Chromatin Condensation ◽  
Feedback Regulation ◽  
Pituitary Hormones ◽  
Feedback Mechanism ◽  
Reproductive Hormones ◽  
Male Rats ◽  
Normal Men

In the last 20 years, a pituitary-hypothalamus tissue culture system with intact neural and portal connections has been developed in our lab and used to understand the feedback mechanisms that regulate the secretions of adenohypophyseal hormones and fertility of male rats. In the last decade, several in vivo rat models have also been developed in our lab with a view to substantiate the in vitro findings, in order to delineate the role of pituitary hormones in the regulation of fertility of male rats. These studies have relied on both surgical and pharmacological interventions to modulate the secretions of gonadotropins and testosterone. The interrelationship between the circadian release of reproductive hormones has also been ascertained in normal men. Our studies suggest that testosterone regulates the secretion of prolactin through a long feedback mechanism, which appears to have been conserved from rats to humans. These studies have filled in a major lacuna pertaining to the role of prolactin in male reproductive physiology by demonstrating the interdependence between testosterone and prolactin. Systemic levels of prolactin play a deterministic role in the mechanism of chromatin condensation during spermiogenesis.

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