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Differential interaction of Apolipoprotein-E isoforms with insulin receptors modulates brain insulin signaling in mutant human amyloid precursor protein transgenic mice.

Chan ES, Chen C, Cole GM, Wong BS - Sci Rep (2015)

Bottom Line: Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration.However, in the presence of Aβ42, insulin failed to elicit a downstream response only in ApoE4 hippocampal neurons.Taken together, our data show that ApoE genotypes can modulate this Aβ-mediated insulin signaling impairment.

View Article: PubMed Central - PubMed

Affiliation: Departments of Physiology Yong Loo Lin School of Medicine, National University of Singapore, Singapore.

ABSTRACT
It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer's disease (AD). Although Aβ levels can lead to insulin signaling impairment, these experiments were done in the absence of human ApoE. To examine ApoE role, we crossed the human ApoE-targeted replacement mice with mutant human amyloid precursor protein (APP) mice. In 26 week old mice with lower Aβ levels, the expression and phosphorylation of insulin signaling proteins remained comparable among APP, ApoE3xAPP and ApoE4xAPP mouse brains. When the mice aged to 78 weeks, these proteins were markedly reduced in APP and ApoE4xAPP mouse brains. While Aβ can bind to insulin receptor, how ApoE isoforms modulate this interaction remains unknown. Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration. In contrast, ApoE4 bound more Aβ42 with increasing peptide levels. Using primary hippocampal neurons, we showed that ApoE3 and ApoE4 neurons are equally sensitive to physiological levels of insulin. However, in the presence of Aβ42, insulin failed to elicit a downstream response only in ApoE4 hippocampal neurons. Taken together, our data show that ApoE genotypes can modulate this Aβ-mediated insulin signaling impairment.

No MeSH data available.


Related in: MedlinePlus

Immunoprecipitation ELISA shows ApoE3 binds to insulin receptor stronger than ApoE4.Total brain lysates from ApoE3 and ApoE4 targeted replacement mice were incubated with increasing concentrations of synthetic (A,B) Aβ42, or (C) scrambled Aβ42 before adding to ELISA pre-coated with anti-ApoE. The captured protein complexes were analyzed for insulin receptor (IR) in (A) and (C), and for Aβ in (B). Each value represents the mean ± SEM for individual mouse brain sample. Statistical comparison was made between ApoE3 and ApoE4 mouse brain sample at each Aβ42 concentration (*p < 0.05; **p < 0.001, using Student’s t-test; n = 4). The t-values for each comparison are shown in table S1.
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f4: Immunoprecipitation ELISA shows ApoE3 binds to insulin receptor stronger than ApoE4.Total brain lysates from ApoE3 and ApoE4 targeted replacement mice were incubated with increasing concentrations of synthetic (A,B) Aβ42, or (C) scrambled Aβ42 before adding to ELISA pre-coated with anti-ApoE. The captured protein complexes were analyzed for insulin receptor (IR) in (A) and (C), and for Aβ in (B). Each value represents the mean ± SEM for individual mouse brain sample. Statistical comparison was made between ApoE3 and ApoE4 mouse brain sample at each Aβ42 concentration (*p < 0.05; **p < 0.001, using Student’s t-test; n = 4). The t-values for each comparison are shown in table S1.

Mentions: As shown in Fig. 4A (Table S1), the level of IR bound to the captured ApoE3 was not significantly altered with increasing Aβ42 concentrations. On the other hand, ApoE3 and ApoE4 had similar abilities to associate with Aβ42 between 0–30 nM. However, ApoE4 associated with more Aβ42 as the concentrations increased beyond 30nM (Fig. 4B, Table S1). Incubation with scrambled Aβ did not affect ApoE3 binding to IR (Fig. 4C, Table S1).


Differential interaction of Apolipoprotein-E isoforms with insulin receptors modulates brain insulin signaling in mutant human amyloid precursor protein transgenic mice.

Chan ES, Chen C, Cole GM, Wong BS - Sci Rep (2015)

Immunoprecipitation ELISA shows ApoE3 binds to insulin receptor stronger than ApoE4.Total brain lysates from ApoE3 and ApoE4 targeted replacement mice were incubated with increasing concentrations of synthetic (A,B) Aβ42, or (C) scrambled Aβ42 before adding to ELISA pre-coated with anti-ApoE. The captured protein complexes were analyzed for insulin receptor (IR) in (A) and (C), and for Aβ in (B). Each value represents the mean ± SEM for individual mouse brain sample. Statistical comparison was made between ApoE3 and ApoE4 mouse brain sample at each Aβ42 concentration (*p < 0.05; **p < 0.001, using Student’s t-test; n = 4). The t-values for each comparison are shown in table S1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561911&req=5

f4: Immunoprecipitation ELISA shows ApoE3 binds to insulin receptor stronger than ApoE4.Total brain lysates from ApoE3 and ApoE4 targeted replacement mice were incubated with increasing concentrations of synthetic (A,B) Aβ42, or (C) scrambled Aβ42 before adding to ELISA pre-coated with anti-ApoE. The captured protein complexes were analyzed for insulin receptor (IR) in (A) and (C), and for Aβ in (B). Each value represents the mean ± SEM for individual mouse brain sample. Statistical comparison was made between ApoE3 and ApoE4 mouse brain sample at each Aβ42 concentration (*p < 0.05; **p < 0.001, using Student’s t-test; n = 4). The t-values for each comparison are shown in table S1.
Mentions: As shown in Fig. 4A (Table S1), the level of IR bound to the captured ApoE3 was not significantly altered with increasing Aβ42 concentrations. On the other hand, ApoE3 and ApoE4 had similar abilities to associate with Aβ42 between 0–30 nM. However, ApoE4 associated with more Aβ42 as the concentrations increased beyond 30nM (Fig. 4B, Table S1). Incubation with scrambled Aβ did not affect ApoE3 binding to IR (Fig. 4C, Table S1).

Bottom Line: Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration.However, in the presence of Aβ42, insulin failed to elicit a downstream response only in ApoE4 hippocampal neurons.Taken together, our data show that ApoE genotypes can modulate this Aβ-mediated insulin signaling impairment.

View Article: PubMed Central - PubMed

Affiliation: Departments of Physiology Yong Loo Lin School of Medicine, National University of Singapore, Singapore.

ABSTRACT
It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer's disease (AD). Although Aβ levels can lead to insulin signaling impairment, these experiments were done in the absence of human ApoE. To examine ApoE role, we crossed the human ApoE-targeted replacement mice with mutant human amyloid precursor protein (APP) mice. In 26 week old mice with lower Aβ levels, the expression and phosphorylation of insulin signaling proteins remained comparable among APP, ApoE3xAPP and ApoE4xAPP mouse brains. When the mice aged to 78 weeks, these proteins were markedly reduced in APP and ApoE4xAPP mouse brains. While Aβ can bind to insulin receptor, how ApoE isoforms modulate this interaction remains unknown. Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration. In contrast, ApoE4 bound more Aβ42 with increasing peptide levels. Using primary hippocampal neurons, we showed that ApoE3 and ApoE4 neurons are equally sensitive to physiological levels of insulin. However, in the presence of Aβ42, insulin failed to elicit a downstream response only in ApoE4 hippocampal neurons. Taken together, our data show that ApoE genotypes can modulate this Aβ-mediated insulin signaling impairment.

No MeSH data available.


Related in: MedlinePlus