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Membrane microdomain switching: a regulatory mechanism of amyloid precursor protein processing.

Sakurai T, Kaneko K, Okuno M, Wada K, Kashiyama T, Shimizu H, Akagi T, Hashikawa T, Nukina N - J. Cell Biol. (2008)

Bottom Line: However, the molecular mechanisms underlying this effect remain to be elucidated.We found syntaxin 1 as a key molecule for activity-dependent regulation of APP processing in cholesterol-dependent microdomains.We propose that microdomain switching is a mechanism of cholesterol- and activity-dependent regulation of APP processing in neurons.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.

ABSTRACT
Neuronal activity has an impact on beta cleavage of amyloid precursor protein (APP) by BACE1 to generate amyloid-beta peptide (Abeta). However, the molecular mechanisms underlying this effect remain to be elucidated. Cholesterol dependency of beta cleavage prompted us to analyze immunoisolated APP-containing detergent-resistant membranes from rodent brains. We found syntaxin 1 as a key molecule for activity-dependent regulation of APP processing in cholesterol-dependent microdomains. In living cells, APP associates with syntaxin 1-containing microdomains through X11-Munc18, which inhibits the APP-BACE1 interaction and beta cleavage via microdomain segregation. Phosphorylation of Munc18 by cdk5 causes a shift of APP to BACE1-containing microdomains. Neuronal hyperactivity, implicated in Abeta overproduction, promotes the switching of APP microdomain association as well as beta cleavage in a partially cdk5-dependent manner. We propose that microdomain switching is a mechanism of cholesterol- and activity-dependent regulation of APP processing in neurons.

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Overexpression of p25 promotes microdomain switching in primary neurons. At 3 DIV, hippocampal neurons were transfected with human APP, syntaxin 1–HA, BACE1AA, and p25. At 6 DIV, patch formation was induced by mouse anti–human APPex, rat anti-HA, and rabbit anti-BACE1ex. (a) Coexpression of p25 caused a reduction of APP–syntaxin 1 copatching on axons. Copatching is indicated by arrowheads. Bar, 5 μm. (b) Quantification of copatching on axons demonstrates a cdk5-induced switching of microdomain association of APP in a similar way to N2a cells. Data are means + SD based on three independent experiments (n = 30–38). ***, P < 0.001.
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fig8: Overexpression of p25 promotes microdomain switching in primary neurons. At 3 DIV, hippocampal neurons were transfected with human APP, syntaxin 1–HA, BACE1AA, and p25. At 6 DIV, patch formation was induced by mouse anti–human APPex, rat anti-HA, and rabbit anti-BACE1ex. (a) Coexpression of p25 caused a reduction of APP–syntaxin 1 copatching on axons. Copatching is indicated by arrowheads. Bar, 5 μm. (b) Quantification of copatching on axons demonstrates a cdk5-induced switching of microdomain association of APP in a similar way to N2a cells. Data are means + SD based on three independent experiments (n = 30–38). ***, P < 0.001.

Mentions: A recent study has implicated prolonged hyperactivity of cdk5 caused by p25 in the enhanced Aβ generation in neurons (Cruz et al., 2006). Although modulations in axonal transport or BACE1 protein levels (Wen et al., 2008) were suggested as possible mechanisms, microdomain switching may also be involved. We tested the effects of p25-induced cdk5 activation on microdomain association of APP in primary cultured neurons (Fig. 8). On axons of transfected neurons with APP, syntaxin 1–HA, and BACE1AA, we observed preferential copatching between APP and syntaxin 1 but segregation between APP and BACE1 in a similar way to N2a cells. Cotransfection of p25 caused a shift of APP association from syntaxin 1 to BACE1, suggesting an involvement of microdomain switching in β cleavage promotion by cdk5 in neurons.


Membrane microdomain switching: a regulatory mechanism of amyloid precursor protein processing.

Sakurai T, Kaneko K, Okuno M, Wada K, Kashiyama T, Shimizu H, Akagi T, Hashikawa T, Nukina N - J. Cell Biol. (2008)

Overexpression of p25 promotes microdomain switching in primary neurons. At 3 DIV, hippocampal neurons were transfected with human APP, syntaxin 1–HA, BACE1AA, and p25. At 6 DIV, patch formation was induced by mouse anti–human APPex, rat anti-HA, and rabbit anti-BACE1ex. (a) Coexpression of p25 caused a reduction of APP–syntaxin 1 copatching on axons. Copatching is indicated by arrowheads. Bar, 5 μm. (b) Quantification of copatching on axons demonstrates a cdk5-induced switching of microdomain association of APP in a similar way to N2a cells. Data are means + SD based on three independent experiments (n = 30–38). ***, P < 0.001.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2568028&req=5

fig8: Overexpression of p25 promotes microdomain switching in primary neurons. At 3 DIV, hippocampal neurons were transfected with human APP, syntaxin 1–HA, BACE1AA, and p25. At 6 DIV, patch formation was induced by mouse anti–human APPex, rat anti-HA, and rabbit anti-BACE1ex. (a) Coexpression of p25 caused a reduction of APP–syntaxin 1 copatching on axons. Copatching is indicated by arrowheads. Bar, 5 μm. (b) Quantification of copatching on axons demonstrates a cdk5-induced switching of microdomain association of APP in a similar way to N2a cells. Data are means + SD based on three independent experiments (n = 30–38). ***, P < 0.001.
Mentions: A recent study has implicated prolonged hyperactivity of cdk5 caused by p25 in the enhanced Aβ generation in neurons (Cruz et al., 2006). Although modulations in axonal transport or BACE1 protein levels (Wen et al., 2008) were suggested as possible mechanisms, microdomain switching may also be involved. We tested the effects of p25-induced cdk5 activation on microdomain association of APP in primary cultured neurons (Fig. 8). On axons of transfected neurons with APP, syntaxin 1–HA, and BACE1AA, we observed preferential copatching between APP and syntaxin 1 but segregation between APP and BACE1 in a similar way to N2a cells. Cotransfection of p25 caused a shift of APP association from syntaxin 1 to BACE1, suggesting an involvement of microdomain switching in β cleavage promotion by cdk5 in neurons.

Bottom Line: However, the molecular mechanisms underlying this effect remain to be elucidated.We found syntaxin 1 as a key molecule for activity-dependent regulation of APP processing in cholesterol-dependent microdomains.We propose that microdomain switching is a mechanism of cholesterol- and activity-dependent regulation of APP processing in neurons.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.

ABSTRACT
Neuronal activity has an impact on beta cleavage of amyloid precursor protein (APP) by BACE1 to generate amyloid-beta peptide (Abeta). However, the molecular mechanisms underlying this effect remain to be elucidated. Cholesterol dependency of beta cleavage prompted us to analyze immunoisolated APP-containing detergent-resistant membranes from rodent brains. We found syntaxin 1 as a key molecule for activity-dependent regulation of APP processing in cholesterol-dependent microdomains. In living cells, APP associates with syntaxin 1-containing microdomains through X11-Munc18, which inhibits the APP-BACE1 interaction and beta cleavage via microdomain segregation. Phosphorylation of Munc18 by cdk5 causes a shift of APP to BACE1-containing microdomains. Neuronal hyperactivity, implicated in Abeta overproduction, promotes the switching of APP microdomain association as well as beta cleavage in a partially cdk5-dependent manner. We propose that microdomain switching is a mechanism of cholesterol- and activity-dependent regulation of APP processing in neurons.

Show MeSH