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PubMed Central (PMC3 - NLM DTD) (2,688,257 recursos)
Archive of life sciences journal literature at the U.S. National Institutes of Health (NIH), developed and managed by NIH's National Center for Biotechnology Information (NCBI) in the National Library of Medicine (NLM).

Mostrando recursos 1 - 20 de 982

1. Rab5 activation promotes focal adhesion disassembly, migration and invasiveness in tumor cells - Mendoza, Pablo; Ortiz, Rina; Díaz, Jorge; Quest, Andrew F. G.; Leyton, Lisette; Stupack, Dwayne; Torres, Vicente A.
Migration and invasion are essential steps associated with tumor cell metastasis and increasing evidence points towards endosome trafficking being essential in this process. Indeed, the small GTPase Rab5, a crucial regulator of early endosome dynamics, promotes cell migration in vitro and in vivo. Precisely how Rab5 participates in these events remains to be determined. Considering that focal adhesions represent structures crucial to cell migration, we specifically asked whether Rab5 activation promoted focal adhesion disassembly and thereby facilitated migration and invasion of metastatic cancer cells. Pulldown and biosensor assays revealed that Rab5-GTP loading increased at the leading edge of migrating tumor...

2. Meeting Report – Visualizing signaling nanoplatforms at a higher spatiotemporal resolution - Cambi, Alessandra; Lakadamyali, Melike; Lidke, Diane S.; Garcia-Parajo, Maria F.
The International Symposium entitled ‘Visualizing signaling nanoplatforms at a higher spatiotemporal resolution’ sponsored by the Institució Catalana de Recerca i Estudis Avançats (ICREA) was held on 29–31 May 2013 at the ICFO-Institute of Photonic Sciences, in Barcelona, Spain. The meeting brought together a multidisciplinary group of international leaders in the fields of super-resolution imaging (nanoscopy) and cell membrane biology, and served as a forum to further our understanding of the fundamental mechanisms that govern nanostructures and protein–function relationships at the cell membrane.

3. Phospholipid flippase ATP8A2 is required for normal visual and auditory function and photoreceptor and spiral ganglion cell survival - Coleman, Jonathan A.; Zhu, Xianjun; Djajadi, Hidayat R.; Molday, Laurie L.; Smith, Richard S.; Libby, Richard T.; John, Simon W. M.; Molday, Robert S.
ATP8A2 is a P4-ATPase that is highly expressed in the retina, brain, spinal cord and testes. In the retina, ATP8A2 is localized in photoreceptors where it uses ATP to transport phosphatidylserine (PS) and phosphatidylethanolamine (PE) from the exoplasmic to the cytoplasmic leaflet of membranes. Although mutations in ATP8A2 have been reported to cause mental retardation in humans and degeneration of spinal motor neurons in mice, the role of ATP8A2 in sensory systems has not been investigated. We have analyzed the retina and cochlea of ATP8A2-deficient mice to determine the role of ATP8A2 in visual and auditory systems. ATP8A2-deficient mice have...

4. The Mon1–Ccz1 GEF activates the Rab7 GTPase Ypt7 via a longin-fold–Rab interface and association with PI3P-positive membranes - Cabrera, Margarita; Nordmann, Mirjana; Perz, Angela; Schmedt, David; Gerondopoulos, Andreas; Barr, Francis; Piehler, Jacob; Engelbrecht-Vandré, Siegfried; Ungermann, Christian
To function in fusion and signaling, Rab GTPases need to be converted into their active GTP form. We previously identified the conserved Mon1–Ccz1 complex as the guanine nucleotide exchange factor (GEF) of the yeast Rab7 GTPase Ypt7. To address the possible GEF mechanism, we generated a homology model of the predicted longin domains of Mon1 and Ccz1 using the Rab-binding surface of the TRAPP complex as a template. On the basis of this, we identified mutations in both yeast Mon1 and Ccz1 that block Ypt7 activation, without affecting heterodimer formation and intracellular localization of Mon1 and Ccz1 at endosomes. Strikingly,...

5. Endoplasmic reticulum stress impairs IL-4/IL-13 signaling through C/EBPβ-mediated transcriptional suppression - Arensdorf, Angela M.; Thomas Rutkowski, D.
Activation of the unfolded protein response (UPR) by endoplasmic reticulum (ER) stress culminates in extensive gene regulation, with transcriptional upregulation of genes that improve the protein folding capacity of the organelle. However, a substantial number of genes are downregulated by ER stress, and the mechanisms that lead to this downregulation and its consequences on cellular function are poorly understood. We found that ER stress led to coordinated transcriptional suppression of diverse cellular processes, including those involved in cytokine signaling. Using expression of the IL-4/IL-13 receptor subunit Il4ra as a sentinel, we sought to understand the mechanism behind this suppression and...

6. The telomere-associated homeobox-containing protein TAH1/HMBOX1 participates in telomere maintenance in ALT cells - Feng, Xuyang; Luo, Zhenhua; Jiang, Shuai; Li, Feng; Han, Xin; Hu, Yang; Wang, Dan; Zhao, Yong; Ma, Wenbin; Liu, Dan; Huang, Junjiu; Songyang, Zhou
The majority of cancer cells rely on elevated telomerase expression and activity for rapid growth and proliferation. Telomerase-negative cancer cells, by contrast, often employ the alternative lengthening of telomeres (ALT) pathway to maintain telomeres. ALT cells are characterized by long and dynamic telomeres and the presence of ALT-associated promyelocytic leukemia (PML) bodies (APBs). Previous work has shown the importance of APBs to the ALT pathway, but their formation and precise role remain unclear. Here, we demonstrate that a homeobox-containing protein known as HMBOX1 can directly bind telomeric double-stranded DNA and associate with PML nuclear bodies. Hence, we renamed this protein...

7. Protective effects of matrix metalloproteinase-12 following corneal injury - Chan, Matilda F.; Li, Jing; Bertrand, Anthony; Casbon, Amy-Jo; Lin, Jeffrey H.; Maltseva, Inna; Werb, Zena
Corneal scarring due to injury is a leading cause of blindness worldwide and results from dysregulated inflammation and angiogenesis during wound healing. Here we demonstrate that the extracellular matrix metalloproteinase MMP12 (macrophage metalloelastase) is an important regulator of these repair processes. Chemical injury resulted in higher expression of the fibrotic markers α-smooth muscle actin and type I collagen, and increased levels of angiogenesis in corneas of Mmp12−/− mice compared with corneas of wild-type mice. In vivo, we observed altered immune cell dynamics in Mmp12−/− corneas by confocal imaging. We determined that the altered dynamics were the result of an altered...

8. The DNA damage checkpoint protein RAD9A is essential for male meiosis in the mouse - Vasileva, Ana; Hopkins, Kevin M.; Wang, Xiangyuan; Weisbach, Melissa M.; Friedman, Richard A.; Wolgemuth, Debra J.; Lieberman, Howard B.
In mitotic cells, RAD9A functions in repairing DNA double-strand breaks (DSBs) by homologous recombination and facilitates the process by cell cycle checkpoint control in response to DNA damage. DSBs occur naturally in the germline during meiosis but whether RAD9A participates in repairing such breaks is not known. In this study, we determined that RAD9A is indeed expressed in the male germ line with a peak of expression in late pachytene and diplotene stages, and the protein was found associated with the XY body. As complete loss of RAD9A is embryonic lethal, we constructed and characterized a mouse strain with Stra8-Cre...

9. The phosphorylation of ARPP19 by Greatwall renders the auto-amplification of MPF independently of PKA in Xenopus oocytes - Dupré, Aude; Buffin, Eulalie; Roustan, Chloé; Nairn, Angus C.; Jessus, Catherine; Haccard, Olivier
Entry into mitosis or meiosis relies on the coordinated action of kinases and phosphatases that ultimately leads to the activation of Cyclin-B–Cdk1, also known as MPF for M-phase promoting factor. Vertebrate oocytes are blocked in prophase of the first meiotic division, an arrest that is tightly controlled by high PKA activity. Re-entry into meiosis depends on activation of Cdk1, which obeys a two-step mechanism: a catalytic amount of Cdk1 is generated in a PKA and protein-synthesis-dependent manner; then a regulatory network known as the MPF auto-amplification loop is initiated. This second step is independent of PKA and protein synthesis. However,...

10. ZO-1 recruitment to α-catenin – a novel mechanism for coupling the assembly of tight junctions to adherens junctions - Maiers, Jessica L.; Peng, Xiao; Fanning, Alan S.; DeMali, Kris A.
The formation of a barrier between epithelial cells is a fundamental determinant of cellular homeostasis, protecting underlying cells against pathogens, dehydration and damage. Assembly of the tight junction barrier is dependent upon neighboring epithelial cells binding to one another and forming adherens junctions, but the mechanism for how these processes are linked is poorly understood. Using a knockdown and substitution system, we studied whether ZO-1 binding to α-catenin is required for coupling tight junction assembly to the formation of adherens junctions. We found that preventing ZO-1 binding to α-catenin did not appear to affect adherens junctions. Rather the assembly and...

11. Matched miRNA and mRNA signatures from an hESC-based in vitro model of pancreatic differentiation reveal novel regulatory interactions - Liao, Xiaoyan; Xue, Haipeng; Wang, Yu-Chieh; Nazor, Kristopher L.; Guo, Shuren; Trivedi, Neha; Peterson, Suzanne E.; Liu, Ying; Loring, Jeanne F.; Laurent, Louise C.
The differentiation of human pluripotent stem cells (hPSCs) to insulin-expressing beta islet-like cells is a promising in vitro model system for studying the molecular signaling pathways underlying beta cell differentiation, as well as a potential source of cells for the treatment of type 1 diabetes. MicroRNAs (miRNAs) are a class of small non-coding RNAs that regulate many biological processes, including cellular differentiation. We studied the miRNA and mRNA expression profiles of hPSCs at five stages of in vitro differentiation along the pancreatic beta cell lineage (definitive endoderm, primitive gut tube, posterior foregut, pancreatic progenitor and hormone-expressing endocrine cells) in the...

12. Syndecan-4 signaling at a glance - Elfenbein, Arye; Simons, Michael
Syndecan-4, a ubiquitous cell surface proteoglycan, mediates numerous cellular processes through signaling pathways that affect cellular proliferation, migration, mechanotransduction and endocytosis. These effects are achieved through syndecan-4 functioning as both a co-receptor for the fibroblast growth factor receptors (FGFR1–FGFR4) and its ability to independently activate signaling pathways upon ligand binding. As an FGFR co-receptor, syndecan-4 strengthens the duration and intensity of downstream signaling upon ligand binding; this is particularly evident with regard to mitogen-activated protein kinase (MAPK) signaling. In contrast, syndecan-4 also functions as an independent receptor for heparin-binding growth factors, such as fibroblast growth factors (FGFs), vascular endothelial growth...

13. Type VII collagen regulates expression of OATP1B3, promotes front-to-rear polarity and increases structural organisation in 3D spheroid cultures of RDEB tumour keratinocytes - Dayal, Jasbani H. S.; Cole, Clare L.; Pourreyron, Celine; Watt, Stephen A.; Lim, Yok Zuan; Salas-Alanis, Julio C.; Murrell, Dedee F.; McGrath, John A.; Stieger, Bruno; Jahoda, Colin; Leigh, Irene M.; South, Andrew P.
Type VII collagen is the main component of anchoring fibrils, structures that are integral to basement membrane homeostasis in skin. Mutations in the gene encoding type VII collagen COL7A1 cause recessive dystrophic epidermolysis bullosa (RDEB) an inherited skin blistering condition complicated by frequent aggressive cutaneous squamous cell carcinoma (cSCC). OATP1B3, which is encoded by the gene SLCO1B3, is a member of the OATP (organic anion transporting polypeptide) superfamily responsible for transporting a wide range of endogenous and xenobiotic compounds. OATP1B3 expression is limited to the liver in healthy tissues, but is frequently detected in multiple cancer types and is reported...

14. Plectin-containing, centrally localized focal adhesions exert traction forces in primary lung epithelial cells - Eisenberg, Jessica L.; Beaumont, Kristin G.; Takawira, Desire; Hopkinson, Susan B.; Mrksich, Milan; Budinger, G. R. Scott; Jones, Jonathan C. R.
Receptor clustering upon cell attachment to the substrate induces assembly of cytoplasmic protein complexes termed focal adhesions (FAs), which connect, albeit indirectly, the extracellular matrix to the cytoskeleton. A subset of cultured primary alveolar epithelial cells (AEC) display a unique pattern of vinculin/paxillin/talin-rich FAs in two concentric circles when cultured on glass and micropatterned substrates: one ring of FAs located at the cell periphery (pFAs), and another FA ring located centrally in the cell (cFAs). Unusually, cFAs associate with an aster-like actin array as well as keratin bundles. Moreover, cFAs show rapid paxillin turnover rates following fluorescence recovery after photobleaching...

15. TGFβ receptor I transactivation mediates stretch-induced Pak1 activation and CTGF upregulation in mesangial cells - Chen, Guang; Chen, Xing; Sukumar, Aravin; Gao, Bo; Curley, Jessica; Schnaper, H. William; Ingram, Alistair J.; Krepinsky, Joan C.
Increased intraglomerular pressure is an important pathogenic determinant of kidney fibrosis in the progression of chronic kidney disease, and can be modeled by exposing glomerular mesangial cells (MC) to mechanical stretch. MC produce extracellular matrix and profibrotic cytokines, including connective tissue growth factor (CTGF) when stretched. We show that p21-activated kinase 1 (Pak1) is activated by stretch in MC in culture and in vivo in a process marked by elevated intraglomerular pressures. Its activation is essential for CTGF upregulation. Rac1 is an upstream regulator of Pak1 activation. Stretch induces transactivation of the type I transforming growth factor β1 receptor (TβRI)...

16. The reprogrammed pancreatic progenitor-like intermediate state of hepatic cells is more susceptible to pancreatic beta cell differentiation - Wang, Qiwei; Wang, Hai; Sun, Yu; Li, Shi-Wu; Donelan, William; Chang, Lung-Ji; Jin, Shouguang; Terada, Naohiro; Cheng, Henrique; Reeves, Westley H.; Yang, Li-Jun
Induced pluripotent stem cells (iPSCs) hold great promise for cell therapy. However, their low efficiency of lineage-specific differentiation and tumorigenesis severely hinder clinical translation. We hypothesized that reprogramming of somatic cells into lineage-specific progenitor cells might allow for large-scale expansion, avoiding the tumorigenesis inherent with iPSCs and simultaneously facilitating lineage-specific differentiation. Here we aimed at reprogramming rat hepatic WB cells, using four Yamanaka factors, into pancreatic progenitor cells (PPCs) or intermediate (IM) cells that have characteristics of PPCs. IM clones were selected based on their specific morphology and alkaline phosphatase activity and stably passaged under defined culture conditions. IM cells...

17. αvβ3-integrin-mediated adhesion is regulated through an AAK1L- and EHD3-dependent rapid-recycling pathway - Waxmonsky, Nicole C.; Conner, Sean D.
Protein transport through the endosome is critical for maintaining proper integrin cell surface integrin distribution to support cell adhesion, motility and viability. Here we employ a live-cell imaging approach to evaluate the relationship between integrin function and transport through the early endosome. We discovered that two early endosome factors, AAK1L and EHD3, are critical for αvβ3-integrin-mediated cell adhesion in HeLa cells. siRNA-mediated depletion of either factor delays short-loop β3 integrin recycling from the early endosome back to the cell surface. Total internal reflection fluorescence-based colocalization analysis reveals that β3 integrin transits AAK1L- and EHD3-positive endosomes near the cell surface, a...

18. Non-invasive neural stem cells become invasive in vitro by combined FGF2 and BMP4 signaling - Sailer, Martin H. M.; Gerber, Alexandra; Tostado, Cristóbal; Hutter, Gregor; Cordier, Dominik; Mariani, Luigi; Ritz, Marie-Françoise
Neural stem cells (NSCs) typically show efficient self-renewal and selective differentiation. Their invasion potential, however, is not well studied. In this study, Sox2-positive NSCs from the E14.5 rat cortex were found to be non-invasive and showed only limited migration in vitro. By contrast, FGF2-expanded NSCs showed a strong migratory and invasive phenotype in response to the combination of FGF2 and BMP4. Invasive NSCs expressed Podoplanin (PDPN) and p75NGFR (Ngfr) at the plasma membrane after exposure to FGF2 and BMP4. FGF2 and BMP4 together upregulated the expression of Msx1, Snail1, Snail2, Ngfr, which are all found in neural crest (NC) cells...

19. A heterogeneous lineage origin underlies the phenotypic and molecular differences of white and beige adipocytes - Liu, Weiyi; Shan, Tizhong; Yang, Xin; Liang, Sandra; Zhang, Pengpeng; Liu, Yaqin; Liu, Xiaoqi; Kuang, Shihuan
A worldwide epidemic of obesity and its associated metabolic disorders raise the significance of adipocytes, their origins and characteristics. Our previous study has demonstrated that interscapular brown adipose tissue (BAT), but not intramuscular adipose, is derived from the Pax3-expressing cell lineage. Here, we show that various depots of subcutaneous (SAT) and visceral adipose tissue (VAT) are highly heterogeneous in the Pax3 lineage origin. Interestingly, the relative abundance of Pax3 lineage cells in SAT depots is inversely correlated to expression of BAT signature genes including Prdm16, Pgc1a (Ppargc1a) and Ucp1. FACS analysis further demonstrates that adipocytes differentiated from non-Pax3 lineage preadipocytes...

20. SA1 binds directly to DNA through its unique AT-hook to promote sister chromatid cohesion at telomeres - Bisht, Kamlesh K.; Daniloski, Zharko; Smith, Susan
Sister chromatid cohesion relies on cohesin, a complex comprising a tri-partite ring and a peripheral subunit Scc3, which is found as two related isoforms SA1 and SA2 in vertebrates. There is a division of labor between the vertebrate cohesin complexes; SA1-cohesin is required at telomeres and SA2-cohesin at centromeres. Depletion of SA1 has dramatic consequences for telomere function and genome integrity, but the mechanism by which SA1-cohesin mediates cohesion at telomeres is not well understood. Here we dissect the individual contribution of SA1 and the ring subunits to telomere cohesion and show that telomeres rely heavily on SA1 and to...

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