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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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Effects of cholesterol depletion on microdomain association of APP and segregation between syntaxin 1 and BACE1 in N2a cells. Mild reduction of cellular cholesterol levels (0.4 μM lovastatin and 1 mM MβCD) caused a switching of APP's microdomain association without changing segregation between BACE1 and syntaxin 1. Further reduction (0.4 μM lovastatin and 1.5 mM MβCD) induced a loss of BACE1 segregation from syntaxin 1, which is consistent with the requirement of intact cholesterol-dependent microdomains for BACE1 exclusion. Data are means + SD based on three independent experiments (n = 31–39). **, P < 0.01.
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fig7: Effects of cholesterol depletion on microdomain association of APP and segregation between syntaxin 1 and BACE1 in N2a cells. Mild reduction of cellular cholesterol levels (0.4 μM lovastatin and 1 mM MβCD) caused a switching of APP's microdomain association without changing segregation between BACE1 and syntaxin 1. Further reduction (0.4 μM lovastatin and 1.5 mM MβCD) induced a loss of BACE1 segregation from syntaxin 1, which is consistent with the requirement of intact cholesterol-dependent microdomains for BACE1 exclusion. Data are means + SD based on three independent experiments (n = 31–39). **, P < 0.01.

Mentions: To gain insight into the mechanism of BACE1 exclusion by syntaxin 1, we examined the effect of cholesterol depletion on BACE1–syntaxin 1 segregation (Fig. 7). Mild reduction of cellular cholesterol levels (Abad-Rodriguez et al., 2004) caused a shift in microdomain association of APP from syntaxin 1 to BACE1, whereas BACE1 and syntaxin 1 remained segregated. These changes are consistent with the failure of APP–X11–Munc18–syntaxin 1 complex formation demonstrated by the DRM analysis of cholesterol-depleted primary neurons (Fig. S2 b), probably because of the defective recruitment of APP into syntaxin 1 microdomains and subsequent stabilization by X11–Munc18. Further cholesterol depletion induced diminution of BACE1–syntaxin 1 segregation, indicating the requirement of intact cholesterol-dependent microdomains for BACE1–syntaxin 1 segregation.


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)

Effects of cholesterol depletion on microdomain association of APP and segregation between syntaxin 1 and BACE1 in N2a cells. Mild reduction of cellular cholesterol levels (0.4 μM lovastatin and 1 mM MβCD) caused a switching of APP's microdomain association without changing segregation between BACE1 and syntaxin 1. Further reduction (0.4 μM lovastatin and 1.5 mM MβCD) induced a loss of BACE1 segregation from syntaxin 1, which is consistent with the requirement of intact cholesterol-dependent microdomains for BACE1 exclusion. Data are means + SD based on three independent experiments (n = 31–39). **, P < 0.01.
© Copyright Policy
Related In: Results  -  Collection

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

fig7: Effects of cholesterol depletion on microdomain association of APP and segregation between syntaxin 1 and BACE1 in N2a cells. Mild reduction of cellular cholesterol levels (0.4 μM lovastatin and 1 mM MβCD) caused a switching of APP's microdomain association without changing segregation between BACE1 and syntaxin 1. Further reduction (0.4 μM lovastatin and 1.5 mM MβCD) induced a loss of BACE1 segregation from syntaxin 1, which is consistent with the requirement of intact cholesterol-dependent microdomains for BACE1 exclusion. Data are means + SD based on three independent experiments (n = 31–39). **, P < 0.01.
Mentions: To gain insight into the mechanism of BACE1 exclusion by syntaxin 1, we examined the effect of cholesterol depletion on BACE1–syntaxin 1 segregation (Fig. 7). Mild reduction of cellular cholesterol levels (Abad-Rodriguez et al., 2004) caused a shift in microdomain association of APP from syntaxin 1 to BACE1, whereas BACE1 and syntaxin 1 remained segregated. These changes are consistent with the failure of APP–X11–Munc18–syntaxin 1 complex formation demonstrated by the DRM analysis of cholesterol-depleted primary neurons (Fig. S2 b), probably because of the defective recruitment of APP into syntaxin 1 microdomains and subsequent stabilization by X11–Munc18. Further cholesterol depletion induced diminution of BACE1–syntaxin 1 segregation, indicating the requirement of intact cholesterol-dependent microdomains for BACE1–syntaxin 1 segregation.

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
Related in: MedlinePlus