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In JoVE (1)
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Articles by Patricia T. Yam in JoVE
Разбор и культуры спаечный Нейроны из эмбриональных спинного мозга
Sébastien D. Langlois*1,2, Steves Morin*1, Patricia T. Yam1,3,4, Frédéric Charron1,2,5,6,7
1Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal, 2Division of Experimental Medicine and Program in Neuroengineering, McGill University, 3Program in Neuroengineering, McGill University, 4Montreal Neurological Institute, 5Department of Anatomy and Cell Biology, McGill University, 6Department of Biology, McGill University, 7Department of Medicine, Universite de Montreal - University of Montreal
Это видео демонстрирует метод препарировать и культуры спаечный нейроны от E13 крысы спинной спинного мозга. Расхождение между спаечный нейроны полезно изучать клеточные и молекулярные механизмы роста аксонов и руководство.
Other articles by Patricia T. Yam on PubMed
Nature Immunology. Aug, 2002 | Pubmed ID: 12089508
CD4, a member of the immunoglobulin superfamily of receptors that mediates cell-cell interactions in the immune system, is the primary receptor for HIV-1. The extracellular portion of CD4 is a concatenation of four immunoglobulin-like domains, D1 to D4. The D1, D2 and D4 domains each contain a disulfide bond. We show here that the D2 disulfide bond is redox-active. The redox state of the thiols (disulfide versus dithiol) appeared to be regulated by thioredoxin, which is secreted by CD4(+) T cells. Locking the CD4 and the thioredoxin active-site dithiols in the reduced state with a hydrophilic trivalent arsenical blocked entry of HIV-1 into susceptible cells. These findings indicate that redox changes in CD4 D2 are important for HIV-1 entry and represent a new target for HIV-1 entry inhibitors.
Molecular Biology of the Cell. Dec, 2004 | Pubmed ID: 15456901
We have found that early in infection of the intracellular pathogen Listeria monocytogenes in Madin-Darby canine kidney epithelial cells expressing actin conjugated to green fluorescent protein, F-actin rapidly assembles (approximately 25 s) and disassembles (approximately 30 s) around the bacteria, a phenomenon we call flashing. L. monocytogenes strains unable to perform actin-based motility or unable to escape the phagosome were capable of flashing, suggesting that the actin assembly occurs on the phagosome membrane. Cycles of actin assembly and disassembly could occur repeatedly on the same phagosome. Indirect immunofluorescence showed that most bacteria were fully internalized when flashing occurred, suggesting that actin flashing does not represent phagocytosis. Escherichia coli expressing invA, a gene product from Yersinia pseudotuberculosis that mediates cellular invasion, also induced flashing. Furthermore, polystyrene beads coated with E-cadherin or transferrin also induced flashing after internalization. This suggests that flashing occurs downstream of several distinct molecular entry mechanisms and may be a general consequence of internalization of large objects by epithelial cells.
Actin-myosin Network Reorganization Breaks Symmetry at the Cell Rear to Spontaneously Initiate Polarized Cell Motility
The Journal of Cell Biology. Sep, 2007 | Pubmed ID: 17893245
We have analyzed the spontaneous symmetry breaking and initiation of actin-based motility in keratocytes (fish epithelial cells). In stationary keratocytes, the actin network flow was inwards and radially symmetric. Immediately before motility initiation, the actin network flow increased at the prospective cell rear and reoriented in the perinuclear region, aligning with the prospective axis of movement. Changes in actin network flow at the cell front were detectable only after cell polarization. Inhibition of myosin II or Rho kinase disrupted actin network organization and flow in the perinuclear region and decreased the motility initiation frequency, whereas increasing myosin II activity with calyculin A increased the motility initiation frequency. Local stimulation of myosin activity in stationary cells by the local application of calyculin A induced directed motility initiation away from the site of stimulation. Together, these results indicate that large-scale actin-myosin network reorganization and contractility at the cell rear initiate spontaneous symmetry breaking and polarized motility of keratocytes.
Neuron. May, 2009 | Pubmed ID: 19447091
Sonic hedgehog (Shh) plays essential roles in developmental events such as cell fate specification and axon guidance. Shh induces cell fate specification through canonical Shh signaling, mediated by transcription. However, the mechanism by which Shh guides axons is unknown. To study this, we developed an in vitro assay for axon guidance, in which neurons can be imaged while responding to a defined gradient of a chemical cue. Axons of dissociated commissural neurons placed in a Shh gradient turned rapidly toward increasing concentrations of Shh. Consistent with this rapid response, we showed that attraction by Shh does not require transcription. Instead, Shh stimulates the activity of Src family kinase (SFK) members in a Smoothened-dependent manner. Moreover, SFK activity is required for Shh-mediated guidance of commissural axons, but not for induction of Gli transcriptional reporter activity. Together, these results indicate that Shh acts via a rapidly acting, noncanonical signaling pathway to guide axons.
Nature Cell Biology. Oct, 2009 | Pubmed ID: 19767741
Cytosolic fluid dynamics have been implicated in cell motility because of the hydrodynamic forces they induce and because of their influence on transport of components of the actin machinery to the leading edge. To investigate the existence and the direction of fluid flow in rapidly moving cells, we introduced inert quantum dots into the lamellipodia of fish epithelial keratocytes and analysed their distribution and motion. Our results indicate that fluid flow is directed from the cell body towards the leading edge in the cell frame of reference, at about 40% of cell speed. We propose that this forward-directed flow is driven by increased hydrostatic pressure generated at the rear of the cell by myosin contraction, and show that inhibition of myosin II activity by blebbistatin reverses the direction of fluid flow and leads to a decrease in keratocyte speed. We present a physical model for fluid pressure and flow in moving cells that quantitatively accounts for our experimental data.
Nature. May, 2010 | Pubmed ID: 20485438
Crawling locomotion of eukaryotic cells is achieved by a process dependent on the actin cytoskeleton: protrusion of the leading edge requires assembly of a network of actin filaments, which must be disassembled at the cell rear for sustained motility. Although ADF/cofilin proteins have been shown to contribute to actin disassembly, it is not clear how activity of these locally acting proteins could be coordinated over the distance scale of the whole cell. Here we show that non-muscle myosin II has a direct role in actin network disassembly in crawling cells. In fish keratocytes undergoing motility, myosin II is concentrated in regions at the rear with high rates of network disassembly. Activation of myosin II by ATP in detergent-extracted cytoskeletons results in rear-localized disassembly of the actin network. Inhibition of myosin II activity and stabilization of actin filaments synergistically impede cell motility, suggesting the existence of two disassembly pathways, one of which requires myosin II activity. Our results establish the importance of myosin II as an enzyme for actin network disassembly; we propose that gradual formation and reorganization of an actomyosin network provides an intrinsic destruction timer, enabling long-range coordination of actin network treadmilling in motile cells.
The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Oct, 2010 | Pubmed ID: 20962227
Growth cones regulate the speed and direction of neuronal outgrowth during development and regeneration. How the growth cone spatially and temporally regulates signals from guidance cues is poorly understood. Through a proteomic analysis of purified growth cones we identified isoforms of the 14-3-3 family of adaptor proteins as major constituents of the growth cone. Disruption of 14-3-3 via the R18 antagonist or knockdown of individual 14-3-3 isoforms switches nerve growth factor- and myelin-associated glycoprotein-dependent repulsion to attraction in embryonic day 13 chick and postnatal day 5 rat DRG neurons. These effects are reminiscent of switching responses observed in response to elevated cAMP. Intriguingly, R18-dependent switching is blocked by inhibitors of protein kinase A (PKA), suggesting that 14-3-3 proteins regulate PKA. Consistently, 14-3-3 proteins interact with PKA and R18 activates PKA by dissociating its regulatory and catalytic subunits. Thus, 14-3-3 heterodimers regulate the PKA holoenzyme and this activity plays a critical role in modulating neuronal responses to repellent cues.