ResearchPad - 37 https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Vimentin protects cells against nuclear rupture and DNA damage during migration]]> https://www.researchpad.co/article/elastic_article_15324 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.

]]>
<![CDATA[Mechanosensing during directed cell migration requires dynamic actin polymerization at focal adhesions]]> https://www.researchpad.co/article/elastic_article_15317 The mechanical properties of a cell’s microenvironment influence many aspects of cellular behavior, including cell migration. Durotaxis, the migration toward increasing matrix stiffness, has been implicated in processes ranging from development to cancer. During durotaxis, mechanical stimulation by matrix rigidity leads to directed migration. Studies suggest that cells sense mechanical stimuli, or mechanosense, through the acto-myosin cytoskeleton at focal adhesions (FAs); however, FA actin cytoskeletal remodeling and its role in mechanosensing are not fully understood. Here, we show that the Ena/VASP family member, Ena/VASP-like (EVL), polymerizes actin at FAs, which promotes cell-matrix adhesion and mechanosensing. Importantly, we show that EVL regulates mechanically directed motility, and that suppression of EVL expression impedes 3D durotactic invasion. We propose a model in which EVL-mediated actin polymerization at FAs promotes mechanosensing and durotaxis by maturing, and thus reinforcing, FAs. These findings establish dynamic FA actin polymerization as a central aspect of mechanosensing and identify EVL as a crucial regulator of this process.

]]>
<![CDATA[Confinement hinders motility by inducing RhoA-mediated nuclear influx, volume expansion, and blebbing]]> https://www.researchpad.co/article/elastic_article_15302 Cells migrate in vivo through complex confining microenvironments, which induce significant nuclear deformation that may lead to nuclear blebbing and nuclear envelope rupture. While actomyosin contractility has been implicated in regulating nuclear envelope integrity, the exact mechanism remains unknown. Here, we argue that confinement-induced activation of RhoA/myosin-II contractility, coupled with LINC complex-dependent nuclear anchoring at the cell posterior, locally increases cytoplasmic pressure and promotes passive influx of cytoplasmic constituents into the nucleus without altering nuclear efflux. Elevated nuclear influx is accompanied by nuclear volume expansion, blebbing, and rupture, ultimately resulting in reduced cell motility. Moreover, inhibition of nuclear efflux is sufficient to increase nuclear volume and blebbing on two-dimensional surfaces, and acts synergistically with RhoA/myosin-II contractility to further augment blebbing in confinement. Cumulatively, confinement regulates nuclear size, nuclear integrity, and cell motility by perturbing nuclear flux homeostasis via a RhoA-dependent pathway.

]]>
<![CDATA[Beyond proteases: Basement membrane mechanics and cancer invasion]]> https://www.researchpad.co/article/N63e701df-c906-4411-81fa-7d0382f224c2

Chang and Chaudhuri discuss basement membrane mechanics and how cells use both proteolytic and physical mechanisms to invade basement membranes during cancer progression.

]]>
<![CDATA[The therapeutic effect of switching from tacrolimus to low-dose cyclosporine A in renal transplant recipients with BK virus nephropathy]]> https://www.researchpad.co/article/5c94bd6ad5eed0c4846131e3

Background: There is no effective therapy for BK virus (BKV) nephropathy (BKVN). Cyclosporine A (CsA) has a lower immunosuppressive effect than tacrolimus. In vitro studies have shown that CsA inhibits BKV replication. The present study aimed to evaluate the effectiveness of switching from tacrolimus to low-dose CsA in renal transplant recipients with BKVN. Methods: Twenty-four patients diagnosed with BKVN between January 2015 and December 2016 were included. Tacrolimus was switched to low-dose CsA, and patients were followed for 24 months. Primary end points were BKV clearance in blood and graft. Secondary end points were urine specific gravity, serum creatinine, and graft loss. Results: The viremia in all patients cleared at a mean of 2.7 ± 2.0 months after switching to CsA. Urine specific gravity at 3 months after switching to CsA increased significantly compared with that at diagnosis (P=0.002). The timing and trend of urine specific gravity increase was consistent with the timing and trend of blood and urine viral load decrease. Repeated biopsies at a median of 11.2 months (range: 9.1–12.5 months) after switching to CsA showed that 8 patients (42.1%) were negative for BKV, and 11 patients (58.9%) had a decrease in BKV load (P<0.001). There was no statistical difference in the serum creatinine level between the time of diagnosis and 24 months of CsA therapy (P=0.963). The graft survival rate was 100%. Only two patients (8.3%) suffered from acute rejection. Conclusion: Switching from tacrolimus to low-dose CsA may be an effective therapy for BKVN.

]]>
<![CDATA[Influenza virus N-linked glycosylation and innate immunity]]> https://www.researchpad.co/article/5c4b941ed5eed0c48487de5a

Influenza viruses cause seasonal epidemics and sporadic pandemics in humans. The virus’s ability to change its antigenic nature through mutation and recombination, and the difficulty in developing highly effective universal vaccines against it, make it a serious global public health challenge. Influenza virus’s surface glycoproteins, hemagglutinin and neuraminidase, are all modified by the host cell’s N-linked glycosylation pathways. Host innate immune responses are the first line of defense against infection, and glycosylation of these major antigens plays an important role in the generation of host innate responses toward the virus. Here, we review the principal findings in the analytical techniques used to study influenza N-linked glycosylation, the evolutionary dynamics of N-linked glycosylation in seasonal versus pandemic and zoonotic strains, its role in host innate immune responses, and the prospects for lectin-based therapies. As the efficiency of innate immune responses is a critical determinant of disease severity and adaptive immunity, the study of influenza glycobiology is of clinical as well as research interest.

]]>
<![CDATA[DNA-linked inhibitor antibody assay (DIANA) as a new method for screening influenza neuraminidase inhibitors]]> https://www.researchpad.co/article/5c2d42a0d5eed0c484e05b83

Influenza neuraminidase is responsible for the escape of new viral particles from the infected cell surface. Several neuraminidase inhibitors are used clinically to treat patients or stockpiled for emergencies. However, the increasing development of viral resistance against approved inhibitors has underscored the need for the development of new antivirals effective against resistant influenza strains. A facile, sensitive, and inexpensive screening method would help achieve this goal. Recently, we described a multiwell plate-based DNA-linked inhibitor antibody assay (DIANA). This highly sensitive method can quantify femtomolar concentrations of enzymes. DIANA also has been applied to high-throughput enzyme inhibitor screening, allowing the evaluation of inhibition constants from a single inhibitor concentration. Here, we report the design, synthesis, and structural characterization of a tamiphosphor derivative linked to a reporter DNA oligonucleotide for the development of a DIANA-type assay to screen potential influenza neuraminidase inhibitors. The neuraminidase is first captured by an immobilized antibody, and the test compound competes for binding to the enzyme with the oligo-linked detection probe, which is then quantified by qPCR. We validated this novel assay by comparing it with the standard fluorometric assay and demonstrated its usefulness for sensitive neuraminidase detection as well as high-throughput screening of potential new neuraminidase inhibitors.

]]>
<![CDATA[Overexpression of the nucleocapsid protein of Middle East respiratory syndrome coronavirus up-regulates CXCL10]]> https://www.researchpad.co/article/5c129c10d5eed0c4848ca3ca

Middle East respiratory syndrome coronavirus (MERS-CoV) causes respiratory diseases in humans and has a high mortality rate. During infection, MERS-CoV regulates several host cellular processes including antiviral response genes. In order to determine if the nucleocapsid protein of MERS-CoV (MERS-N) plays a role in viral–host interactions, a murine monoclonal antibody was generated so as to allow detection of the protein in infected cells as well as in overexpression system. Then, MERS-N was stably overexpressed in A549 cells, and a PCR array containing 84 genes was used to screen for genes transcriptionally regulated by it. Several up-regulated antiviral genes, namely TNF, IL6, IL8, and CXCL10, were selected for independent validation in transiently transfected 293FT cells. Out of these, the overexpression of MERS-N was found to up-regulate CXCL10 at both transcriptional and translational levels. Interestingly, CXCL10 has been reported to be up-regulated in MERS-CoV infected airway epithelial cells and lung fibroblast cells, as well as monocyte-derived macrophages and dendritic cells. High secretions and persistent increase of CXCL10 in MERS-CoV patients have been also associated with severity of disease. To our knowledge, this is the first report showing that the MERS-N protein is one of the contributing factors for CXCL10 up-regulation during infection. In addition, our results showed that a fragment consisting of residues 196–413 in MERS-N is sufficient to up-regulate CXCL10, while the N-terminal domain and serine-arginine (SR)-rich motif of MERS-N do not play a role in this up-regulation.

]]>
<![CDATA[SUV420H2 is an epigenetic regulator of epithelial/mesenchymal states in pancreatic cancer]]> https://www.researchpad.co/article/5b711265463d7e23c22140d2

Epithelial-to-mesenchymal transition is implicated in metastasis. Viotti et al. show that the histone methyltransferase SUV420H2 favors the mesenchymal identity in pancreatic tumor cells by silencing key drivers of the epithelial state. High levels of SUV420H2 also correlate with a loss of epithelial characteristics in invasive cancer.

]]>
<![CDATA[Fanconi anemia FANCD2 and FANCI proteins regulate the nuclear dynamics of splicing factors]]> https://www.researchpad.co/article/5c01f900d5eed0c4842bf801

Moriel-Carretero et al. show that the Fanconi anemia proteins FANCI and FANCD2 associate with the splicing factor SF3B1 and that DNA replication stress induces the FANCI-dependent release of SF3B1 from nuclear speckles. FANCI and FANCD2 prevent accumulation of postcatalytic intron lariats, suggesting that they help coordinate DNA replication and transcription.

]]>
<![CDATA[Rac3 regulates breast cancer invasion and metastasis by controlling adhesion and matrix degradation]]> https://www.researchpad.co/article/5c01f914d5eed0c4842bfe2c

Donnelly et al. demonstrate that invasion and metastasis of breast cancer cells depend on Rac3-GTPase signaling at invadopodia. Using a novel FRET biosensor, they show that Rac3 activity is regulated by the spatial organization of two RhoGEFs. Rac3 balances the proteolytic and adhesive activities necessary for invasion by integrating extracellular matrix adhesion and MT1-MMP presentation at invadopodia.

]]>
<![CDATA[Regulation of NOTCH signaling by RAB7 and RAB8 requires carboxyl methylation by ICMT]]> https://www.researchpad.co/article/5c01f8f5d5eed0c4842bf51b

Some prenylated proteins such as RAS require carboxyl methylation by ICMT for proper association with cellular membranes. Court et al. show that RAB7 and RAB8 are among these proteins and that by affecting vesicular transport, these GTPases regulate NOTCH signaling in an ICMT-dependent fashion.

]]>
<![CDATA[Receptor tyrosine kinase activation of RhoA is mediated by AKT phosphorylation of DLC1]]> https://www.researchpad.co/article/5c01f90bd5eed0c4842bfb6a

A new common mechanism for increasing RhoA-GTP is identified in Tripathi et al. The increased RhoA-GTP results from signaling mechanisms that phosphorylate and attenuate the DLC1 tumor suppressor, which encodes RhoGAP. The potentially reversible nature of this attenuation may have therapeutic relevance in cancer.

]]>
<![CDATA[BAG3 directly stabilizes Hexokinase 2 mRNA and promotes aerobic glycolysis in pancreatic cancer cells]]> https://www.researchpad.co/article/5c01f8f7d5eed0c4842bf59e

Cancer cells frequently exhibit aerobic glycolysis, known as the Warburg effect. An et al. identify a novel RNA regulatory activity of BAG3, a protein implicated in various cancers. BAG3 enhances posttranscriptionally the expression of Hexokinase 2, the first enzyme involved in glycolysis, and it reprograms glucose metabolism by pancreatic cancer cells.

]]>
<![CDATA[The α6β4 integrin promotes resistance to ferroptosis]]> https://www.researchpad.co/article/5c01f8ffd5eed0c4842bf76f

Lipid peroxidation in the plasma membrane can cause ferroptosis, a form of regulated necrosis. Brown et al. show that matrix detachment can induce ferroptosis, and the α6β4 integrin impedes that process by suppressing expression of the proferroptotic enzyme ACSL4.

]]>
<![CDATA[PDGFRβ translocates to the nucleus and regulates chromatin remodeling via TATA element–modifying factor 1]]> https://www.researchpad.co/article/5c129a74d5eed0c4848c823f

PDGFRβ translocates to the nucleus in a ligand-dependent manner tethered by TATA element–modifying factor 1 (TMF-1). Papadopoulos et al. show that PDGFRβ interacts with TMF-1 and Fer kinase in the nucleus, regulating chromatin remodeling by the SWI–SNF complex and controlling proliferation via a p21-dependent mechanism.

]]>
<![CDATA[Prevalences of overweight, obesity, hyperglycaemia, hypertension and dyslipidaemia in the Gulf: systematic review]]> https://www.researchpad.co/article/5abc8d53463d7e4213e3ca37

Objectives

To examine the prevalence of risk factors for diabetes and its complications in the Co-operation Council of the Arab States of the Gulf (GCC) region.

Design

Systematic review.

Setting

Co-operation Council of the Arab States of the Gulf (GCC) states (United Arab Emirates, Bahrain, Saudi Arabia, Oman, Qatar, Kuwait).

Participants

Residents of the GCC states participating in studies on the prevalence of overweight and obesity, hyperglycaemia, hypertension and dyslipidaemia.

Main outcome measures

Prevalences of overweight, obesity and hyperglycaemia, hypertension and hyperlipidaemia.

Results

Forty-five studies were included in the review. Reported prevalences of overweight and obesity in adults were 25–50% and 13–50%, respectively. Prevalence appeared higher in women and to hold a non-linear association with age. Current prevalence of impaired glucose tolerance was estimated to be 10–20%. Prevalence appears to have been increasing in recent years. Estimated prevalences of hypertension and dyslipidaemia were few and used varied definitions of abnormality, making review difficult, but these also appeared to be high and increasing,

Conclusions

There are high prevalences of risk factors for diabetes and diabetic complications in the GCC region, indicative that their current management is suboptimal. Enhanced management will be critical if escalation of diabetes-related problems is to be averted as industrialization, urbanization and changing population demographics continue.

]]>