How Morphological Constraints Affect Axonal Polarity in Mouse Neurons

Neuronal differentiation is under the tight control of both biochemical and physical information arising from neighboring cells and micro-environment. Here we wished to assay how external geometrical constraints applied to the cell body and/or the neurites of hippocampal neurons may modulate axonal polarization in vitro. Through the use of a panel of non-specific poly-L-lysine micropatterns, we manipulated the neuronal shape. By applying geometrical constraints on the cell body we provided evidence that centrosome location was not predictive of axonal polarization but rather follows axonal fate. When the geometrical constraints were applied to the neurites trajectories we demonstrated that axonal specification was inhibited by curved lines. Altogether these results indicated that intrinsic mechanical tensions occur during neuritic growth and that maximal tension was developed by the axon and expressed on straight trajectories. The strong inhibitory effect of curved lines on axon specification was further demonstrated by their ability to prevent formation of multiple axons normally induced by cytochalasin or taxol treatments. Finally we provided evidence that microtubules were involved in the tension-mediated axonal polarization, acting as curvature sensors during neuronal differentiation. Thus, biomechanics coupled to physical constraints might be the first level of regulation during neuronal development, primary to biochemical and guidance regulations

Human Ischaemic Cascade Studies Using SH-SY5Y Cells: a Systematic Review and Meta-Analysis

Low translational yield for stroke may reflect the focus of discovery science on rodents rather than humans. Just how little is known about human neuronal ischaemic responses is confirmed by systematic review and meta-analysis revealing that data for the most commonly used SH-SY5Y human cells comprises only 84 papers. Oxygen-glucose deprivation, H2O2, hypoxia, glucose-deprivation and glutamate excitotoxicity yielded − 58, − 61, − 29, − 45 and − 49% injury, respectively, with a dose-response relationship found only for H2O2 injury (R2 = 29.29%, p I2 = 99.36%, df = 132, p R2 = 44.77%, p R2 = 28.64%, p R2 = 4.13%, p p 2O2 injury reported only improvement. In studies using glucose deprivation, intervention generally worsened outcome. There was insufficient data to rank individual interventions, but of the studies reporting greatest improvement (> 90% effect size), 7/13 were of herbal medicine constituents (24.85% of the intervention dataset). We conclude that surprisingly little is known of the human neuronal response to ischaemic injury, and that the large impact of methodology on outcome indicates that further model validation is required. Lack of evidence for randomisation, blinding or power analysis suggests that the intervention data is at substantial risk of bias

SUGT1 controls susceptibility to HIV-1 infection by stabilizing microtubule plus-ends

International audienceUnderstanding the viral-host cell interface during HIV-1 infection is a prerequisite for the development of innovative antiviral therapies. Here we show that the suppressor of G2 allele of skp1 (SUGT1) is a permissive factor for human immunodeficiency virus (HIV)-1 infection. Expression of SUGT1 increases in infected cells on human brain sections and in permissive host cells. We found that SUGT1 determines the permissiveness to infection of lymphocytes and macrophages by modulating the nuclear import of the viral genome. More importantly, SUGT1 stabilizes the microtubule plus-ends (+MTs) of host cells (through the modulation of microtubule acetylation and the formation of end-binding protein 1 (EB1) comets). This effect on microtubules favors HIV-1 retrograde trafficking and replication. SUGT1 depletion impairs the replication of HIV-1 patient primary isolates and mutant virus that is resistant to raltegravir antiretroviral agent. Altogether our results identify SUGT1 as a cellular factor involved in the post-entry steps of HIV-1 infection that may be targeted for new therapeutic approaches

EB1 interacts with outwardly curved and straight regions of the microtubule lattice

EB1 is a microtubule plus-end tracking protein that recognizes GTP-tubulin dimers in microtubules and thus represents a unique probe to investigate the architecture of the GTP cap of growing microtubule ends. Here, we conjugated EB1 to gold nanoparticles (EB1-gold) and imaged by cryo-electron tomography its interaction with dynamic microtubules assembled in vitro from purified tubulin. EB1-gold forms comets at the ends of microtubules assembled in the presence of GTP, and interacts with the outer surface of curved and straight tubulin sheets as well as closed regions of the microtubule lattice. Microtubules assembled in the presence of GTP, different GTP analogues or cell extracts display similarly curved sheets at their growing ends, which gradually straighten as their protofilament number increases until they close into a tube. Together, our data provide unique structural information on the interaction of EB1 with growing microtubule ends. They further offer insights into the conformational changes that tubulin dimers undergo during microtubule assembly and the architecture of the GTP-cap region