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BDNF-induced recruitment of TrkB receptor into neuronal lipid rafts: roles in synaptic modulation.

Suzuki S, Numakawa T, Shimazu K, Koshimizu H, Hara T, Hatanaka H, Mei L, Lu B, Kojima M - J. Cell Biol. (2004)

Bottom Line: Moreover, disruption of lipid rafts prevented potentiating effects of BDNF on transmitter release in cultured neurons and synaptic response to tetanus in hippocampal slices.In contrast, lipid rafts are not required for BDNF regulation of neuronal survival.Thus, ligand-induced TrkB translocation into lipid rafts may represent a signaling mechanism selective for synaptic modulation by BDNF in the central nervous system.

View Article: PubMed Central - PubMed

Affiliation: Research Institute for Cell Engineering, National Institute for Advanced Industrial Science and Technology, Ikeda, Osaka, Japan.

ABSTRACT
Brain-derived neurotrophic factor (BDNF) plays an important role in synaptic plasticity but the underlying signaling mechanisms remain unknown. Here, we show that BDNF rapidly recruits full-length TrkB (TrkB-FL) receptor into cholesterol-rich lipid rafts from nonraft regions of neuronal plasma membranes. Translocation of TrkB-FL was blocked by Trk inhibitors, suggesting a role of TrkB tyrosine kinase in the translocation. Disruption of lipid rafts by depleting cholesterol from cell surface blocked the ligand-induced translocation. Moreover, disruption of lipid rafts prevented potentiating effects of BDNF on transmitter release in cultured neurons and synaptic response to tetanus in hippocampal slices. In contrast, lipid rafts are not required for BDNF regulation of neuronal survival. Thus, ligand-induced TrkB translocation into lipid rafts may represent a signaling mechanism selective for synaptic modulation by BDNF in the central nervous system.

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Effects of raft depletion on BDNF regulation of dendritic growth and cell survival. Cultured cortical neurons were treated with or without 10 μM mevastatin (Meva) or 10 μM pravastatin (Prava) in the absence or presence of 200 ng/ml BDNF. Membrane cholesterol content, cell survival, or the number of primary dendrites was measured 3 d later. (A) Effect of mevastatin or pravastatin on membrane cholesterol levels. The data are expressed as the percentage of control (nontreated cultures). *Indicates significantly lower than control; P < 0.001 (t test). n = 5 cultures in each group. (B) Effect of mevastatin or pravastatin on cell viability. Viability of cortical neurons was measured by the WST-1 colorimetric assay, and expressed as OD450. t test; *P < 0.05, **P < 0.01. (C) Effect of mevastatin or pravastatin on the number of MAP-positive neurons. Data are expressed as the percentage of control (nontreated cultures). *P < 0.01, **P < 0.05. In both B and C, the number associated with each column represents the number of cultures used in a single experiment, and three independent experiments were performed. No difference was found between the “+BDNF” groups, nor between the “−BDNF” groups (ANOVA test). (D) The effect of mevastatin on BDNF modulation of dendritic growth. (Left) Representative images of MAP2-stained neurons. After 3-d incubation with BDNF and/or Meva, cells were stained with anti-MAP2 antibody. Note that the number of primary dendrites (arrowheads) is increased by BDNF treatment, and that the effect is completely blocked by mevastatin. Bar, 10 μm. (Right) The number of primary dendrites was quantified and normalized to that of the control. *Indicates significantly higher than all other groups; ANOVA followed by post hoc test; P < 0.00002. The number associated with each column indicates the number of neurons measured in a single experiment, and three independent experiments were performed.
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fig8: Effects of raft depletion on BDNF regulation of dendritic growth and cell survival. Cultured cortical neurons were treated with or without 10 μM mevastatin (Meva) or 10 μM pravastatin (Prava) in the absence or presence of 200 ng/ml BDNF. Membrane cholesterol content, cell survival, or the number of primary dendrites was measured 3 d later. (A) Effect of mevastatin or pravastatin on membrane cholesterol levels. The data are expressed as the percentage of control (nontreated cultures). *Indicates significantly lower than control; P < 0.001 (t test). n = 5 cultures in each group. (B) Effect of mevastatin or pravastatin on cell viability. Viability of cortical neurons was measured by the WST-1 colorimetric assay, and expressed as OD450. t test; *P < 0.05, **P < 0.01. (C) Effect of mevastatin or pravastatin on the number of MAP-positive neurons. Data are expressed as the percentage of control (nontreated cultures). *P < 0.01, **P < 0.05. In both B and C, the number associated with each column represents the number of cultures used in a single experiment, and three independent experiments were performed. No difference was found between the “+BDNF” groups, nor between the “−BDNF” groups (ANOVA test). (D) The effect of mevastatin on BDNF modulation of dendritic growth. (Left) Representative images of MAP2-stained neurons. After 3-d incubation with BDNF and/or Meva, cells were stained with anti-MAP2 antibody. Note that the number of primary dendrites (arrowheads) is increased by BDNF treatment, and that the effect is completely blocked by mevastatin. Bar, 10 μm. (Right) The number of primary dendrites was quantified and normalized to that of the control. *Indicates significantly higher than all other groups; ANOVA followed by post hoc test; P < 0.00002. The number associated with each column indicates the number of neurons measured in a single experiment, and three independent experiments were performed.

Mentions: To test whether lipid rafts are also involved in long-term effects of BDNF, we treated cultures with cholesterol synthesis inhibitors, mevastatin or pravastatin, which effectively deplete rafts from cortical neurons over days (Hering et al., 2003). The cholesterol level was significantly reduced in mevastatin- or pravastatin-treated cortical neurons (Fig. 8 A). We first examined the effect of these lipid raft disrupters on BDNF regulation of neuronal survival, using the WST-1 assay, which quantitatively determines cell viability based on the cleavage activity of a soluble tetrazolium salt WST-1 by mitochondrial dehydrogenases, and by counting the number of MAP2-positive neurons in culture. 3-d treatment with BDNF significantly enhanced the survival of cortical neurons in serum-free medium (Fig. 8, B and C, left; Yamada et al., 2001). Both mevastatin and pravastatin, however, failed to block this effect of BDNF (Fig. 8, B and C, middle and right), indicating that lipid rafts are not required for the regulatory effect of BDNF on cortical neuron survival.


BDNF-induced recruitment of TrkB receptor into neuronal lipid rafts: roles in synaptic modulation.

Suzuki S, Numakawa T, Shimazu K, Koshimizu H, Hara T, Hatanaka H, Mei L, Lu B, Kojima M - J. Cell Biol. (2004)

Effects of raft depletion on BDNF regulation of dendritic growth and cell survival. Cultured cortical neurons were treated with or without 10 μM mevastatin (Meva) or 10 μM pravastatin (Prava) in the absence or presence of 200 ng/ml BDNF. Membrane cholesterol content, cell survival, or the number of primary dendrites was measured 3 d later. (A) Effect of mevastatin or pravastatin on membrane cholesterol levels. The data are expressed as the percentage of control (nontreated cultures). *Indicates significantly lower than control; P < 0.001 (t test). n = 5 cultures in each group. (B) Effect of mevastatin or pravastatin on cell viability. Viability of cortical neurons was measured by the WST-1 colorimetric assay, and expressed as OD450. t test; *P < 0.05, **P < 0.01. (C) Effect of mevastatin or pravastatin on the number of MAP-positive neurons. Data are expressed as the percentage of control (nontreated cultures). *P < 0.01, **P < 0.05. In both B and C, the number associated with each column represents the number of cultures used in a single experiment, and three independent experiments were performed. No difference was found between the “+BDNF” groups, nor between the “−BDNF” groups (ANOVA test). (D) The effect of mevastatin on BDNF modulation of dendritic growth. (Left) Representative images of MAP2-stained neurons. After 3-d incubation with BDNF and/or Meva, cells were stained with anti-MAP2 antibody. Note that the number of primary dendrites (arrowheads) is increased by BDNF treatment, and that the effect is completely blocked by mevastatin. Bar, 10 μm. (Right) The number of primary dendrites was quantified and normalized to that of the control. *Indicates significantly higher than all other groups; ANOVA followed by post hoc test; P < 0.00002. The number associated with each column indicates the number of neurons measured in a single experiment, and three independent experiments were performed.
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Related In: Results  -  Collection

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fig8: Effects of raft depletion on BDNF regulation of dendritic growth and cell survival. Cultured cortical neurons were treated with or without 10 μM mevastatin (Meva) or 10 μM pravastatin (Prava) in the absence or presence of 200 ng/ml BDNF. Membrane cholesterol content, cell survival, or the number of primary dendrites was measured 3 d later. (A) Effect of mevastatin or pravastatin on membrane cholesterol levels. The data are expressed as the percentage of control (nontreated cultures). *Indicates significantly lower than control; P < 0.001 (t test). n = 5 cultures in each group. (B) Effect of mevastatin or pravastatin on cell viability. Viability of cortical neurons was measured by the WST-1 colorimetric assay, and expressed as OD450. t test; *P < 0.05, **P < 0.01. (C) Effect of mevastatin or pravastatin on the number of MAP-positive neurons. Data are expressed as the percentage of control (nontreated cultures). *P < 0.01, **P < 0.05. In both B and C, the number associated with each column represents the number of cultures used in a single experiment, and three independent experiments were performed. No difference was found between the “+BDNF” groups, nor between the “−BDNF” groups (ANOVA test). (D) The effect of mevastatin on BDNF modulation of dendritic growth. (Left) Representative images of MAP2-stained neurons. After 3-d incubation with BDNF and/or Meva, cells were stained with anti-MAP2 antibody. Note that the number of primary dendrites (arrowheads) is increased by BDNF treatment, and that the effect is completely blocked by mevastatin. Bar, 10 μm. (Right) The number of primary dendrites was quantified and normalized to that of the control. *Indicates significantly higher than all other groups; ANOVA followed by post hoc test; P < 0.00002. The number associated with each column indicates the number of neurons measured in a single experiment, and three independent experiments were performed.
Mentions: To test whether lipid rafts are also involved in long-term effects of BDNF, we treated cultures with cholesterol synthesis inhibitors, mevastatin or pravastatin, which effectively deplete rafts from cortical neurons over days (Hering et al., 2003). The cholesterol level was significantly reduced in mevastatin- or pravastatin-treated cortical neurons (Fig. 8 A). We first examined the effect of these lipid raft disrupters on BDNF regulation of neuronal survival, using the WST-1 assay, which quantitatively determines cell viability based on the cleavage activity of a soluble tetrazolium salt WST-1 by mitochondrial dehydrogenases, and by counting the number of MAP2-positive neurons in culture. 3-d treatment with BDNF significantly enhanced the survival of cortical neurons in serum-free medium (Fig. 8, B and C, left; Yamada et al., 2001). Both mevastatin and pravastatin, however, failed to block this effect of BDNF (Fig. 8, B and C, middle and right), indicating that lipid rafts are not required for the regulatory effect of BDNF on cortical neuron survival.

Bottom Line: Moreover, disruption of lipid rafts prevented potentiating effects of BDNF on transmitter release in cultured neurons and synaptic response to tetanus in hippocampal slices.In contrast, lipid rafts are not required for BDNF regulation of neuronal survival.Thus, ligand-induced TrkB translocation into lipid rafts may represent a signaling mechanism selective for synaptic modulation by BDNF in the central nervous system.

View Article: PubMed Central - PubMed

Affiliation: Research Institute for Cell Engineering, National Institute for Advanced Industrial Science and Technology, Ikeda, Osaka, Japan.

ABSTRACT
Brain-derived neurotrophic factor (BDNF) plays an important role in synaptic plasticity but the underlying signaling mechanisms remain unknown. Here, we show that BDNF rapidly recruits full-length TrkB (TrkB-FL) receptor into cholesterol-rich lipid rafts from nonraft regions of neuronal plasma membranes. Translocation of TrkB-FL was blocked by Trk inhibitors, suggesting a role of TrkB tyrosine kinase in the translocation. Disruption of lipid rafts by depleting cholesterol from cell surface blocked the ligand-induced translocation. Moreover, disruption of lipid rafts prevented potentiating effects of BDNF on transmitter release in cultured neurons and synaptic response to tetanus in hippocampal slices. In contrast, lipid rafts are not required for BDNF regulation of neuronal survival. Thus, ligand-induced TrkB translocation into lipid rafts may represent a signaling mechanism selective for synaptic modulation by BDNF in the central nervous system.

Show MeSH
Related in: MedlinePlus