Vesicular Zinc Promotes Presynaptic and Inhibits Postsynaptic Long-Term Potentiation of Mossy Fiber-CA3 Synapse

The presence of zinc in glutamatergic synaptic vesicles of excitatory neurons of mammalian cerebral cortex suggests that zinc might regulate plasticity of synapses formed by these neurons. Long-term potentiation (LTP) is a form of synaptic plasticity that may underlie learning and memory. We tested the hypothesis that zinc within vesicles of mossy fibers (mf) contributes to mf-LTP, a classical form of presynaptic LTP. We synthesized an extracellular zinc chelator with selectivity and kinetic properties suitable for study of the large transient of zinc in the synaptic cleft induced by mf stimulation. We found that vesicular zinc is required for presynaptic mf-LTP. Unexpectedly, vesicular zinc also inhibits a form of postsynaptic mf-LTP. Because the mf-CA3 synapse provides a major source of excitatory input to the hippocampus, regulating its efficacy by these dual actions, vesicular zinc is critical to proper function of hippocampal circuitry in health and disease.National Institute of General Medical Sciences (U.S.) (Grant GM065519

Vesicular Zinc Promotes Presynaptic and Inhibits Postsynaptic Long-Term Potentiation of Mossy Fiber-CA3 Synapse

The presence of zinc in glutamatergic synaptic vesicles of excitatory neurons of mammalian cerebral cortex suggests that zinc might regulate plasticity of synapses formed by these neurons. Long-term potentiation (LTP) is a form of synaptic plasticity that may underlie learning and memory. We tested the hypothesis that zinc within vesicles of mossy fibers (mf) contributes to mf-LTP, a classical form of presynaptic LTP. We synthesized an extracellular zinc chelator with selectivity and kinetic properties suitable for study of the large transient of zinc in the synaptic cleft induced by mf stimulation. We found that vesicular zinc is required for presynaptic mf-LTP. Unexpectedly, vesicular zinc also inhibits a form of postsynaptic mf-LTP. Because the mf-CA3 synapse provides a major source of excitatory input to the hippocampus, regulating its efficacy by these dual actions, vesicular zinc is critical to proper function of hippocampal circuitry in health and disease.National Institute of General Medical Sciences (U.S.) (Grant GM065519

Disruption of TrkB-Mediated Phospholipase C gamma Signaling Inhibits Limbic Epileptogenesis

The BDNF receptor, TrkB, is critical to limbic epileptogenesis, but the responsible downstream signaling pathways are unknown. We hypothesized that TrkB-dependent activation of phospholipase Cgamma1 (PLCgamma1) signaling is the key pathway and tested this in trkB(PLC/PLC) mice carrying a mutation (Y816F) that uncouples TrkB from PLCgamma1. Biochemical measures revealed activation of both TrkB and PLCgamma1 in hippocampi in the pilocarpine and kindling models in wild-type mice. PLCgamma1 activation was decreased in hippocampi isolated from trkB(PLC/PLC) compared with control mice. Epileptogenesis assessed by development of kindling was inhibited in trkB(PLC/PLC) compared with control mice. Long-term potentiation of the mossy fiber-CA3 pyramid synapse was impaired in slices of trkB(PLC/PLC) mice. We conclude that TrkB-dependent activation of PLCgamma1 signaling is an important molecular mechanism of limbic epileptogenesis. Elucidating signaling pathways activated by a cell membrane receptor in animal models of CNS disorders promises to reveal novel targets for specific and effective therapeutic intervention

Irradiation induced molecular and phenotypic changes of EMT.

<p>(A) Radiation cell survival curves and the clonogenic figures of the control KYSE-150 cells without irradiation and radioresistance subclone KYSE-150/RR cells. (B) Morphology of KYSE-150 and KYSE-150/RR cells was examined with phase-contrast microscopy. (C) Expression of EMT markers (E-cadherin and vimentin) and transcription repressors of E-cadherin (Snail and Slug) were detected by qRT-PCR, data shown as mean ±SD, *<i>P</i> <0.05. Data represent means with standard deviation from three independent experiments. (D) Representative western blots of E-cadherin, vimentin, Snail and Slug were showed.</p

PTEN decreased Snail expression through inactivation of PI3K/Akt/GSK-3β signaling.

<p>(A) Expression of Snail and Slug detected by western blot analysis in KYSE-150 cells transfected with siPTEN or vehicle, or KYSE-150/RR cells transfected with pcDNA-PTEN or pcDNA3.0. (B) Expression of Snail were detected by qRT-PCR, data shown as mean±SD. (C) Representative western blot analysis showed expression of Akt, p-Akt, GSK-3β and p-GSK-3β. Data shown represent three different experiments. siPTEN is short for siRNA-PTEN. (D) Representative western blot analysis showed expression of Akt, p-Akt, GSK-3β, p-GSK-3β, Snail and E-cadherin in KYSE-150/RR cells with or without the phosphatidylinositol 3 kinase (PI3K) inhibitor, LY294002 (40 μM).</p

Irradiation-induced EMT enhanced cellular mobility.

<p>(A) KYSE-150 cells were subjected to a wound-healing assay with or without radiation at 100× magnification. Representative images were photographed right and 24 h after the scratch. (B) Representative images of migration assay and invasion assay of KYSE-150 cells with or without radiation were photographed after 24 h with crystal violet stain. (C) Summary graphs for migration and invasion (data shown as mean ±SD, * <i>P</i> <0.05).</p