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Reciprocal relationship between APP positioning relative to the membrane and PS1 conformation.

Uemura K, Farner KC, Nasser-Ghodsi N, Jones P, Berezovska O - Mol Neurodegener (2011)

Bottom Line: Several familial Alzheimer disease (FAD) mutations within the transmembrane region of the amyloid precursor protein (APP) increase the Aβ42/40 ratio without increasing total Aβ production.In the present study, we analyzed the impact of FAD mutations and γ-secretase modulators (GSMs) that alter the Aβ42/40 ratio on APP C-terminus (CT) positioning relative to the membrane, reasoning that changes in the alignment of the APP intramembranous domain and presenilin 1 (PS1) may impact the PS1/γ-secretase cleavage site on APP.Thus, we propose that there is a reciprocal relationship between APP-CT positioning relative to the membrane and PS1 conformation, suggesting that factors that modulate either APP positioning in the membrane or PS1 conformation could be exploited therapeutically.

View Article: PubMed Central - HTML - PubMed

Affiliation: Alzheimer Research Unit, MassGeneral Institute for Neurodegenerative Diseases, Massachusetts General Hospital, Charlestown, MA 02129, USA. oberezovska@partners.org.

ABSTRACT

Background: Several familial Alzheimer disease (FAD) mutations within the transmembrane region of the amyloid precursor protein (APP) increase the Aβ42/40 ratio without increasing total Aβ production. In the present study, we analyzed the impact of FAD mutations and γ-secretase modulators (GSMs) that alter the Aβ42/40 ratio on APP C-terminus (CT) positioning relative to the membrane, reasoning that changes in the alignment of the APP intramembranous domain and presenilin 1 (PS1) may impact the PS1/γ-secretase cleavage site on APP.

Results: By using a Förster resonance energy transfer (FRET)-based technique, fluorescent lifetime imaging microscopy (FLIM), we show that Aβ42/40 ratio-modulating factors which target either APP substrate or PS1/γ-secretase affect proximity of the APP-CT to the membrane and change PS1 conformation.

Conclusions: Thus, we propose that there is a reciprocal relationship between APP-CT positioning relative to the membrane and PS1 conformation, suggesting that factors that modulate either APP positioning in the membrane or PS1 conformation could be exploited therapeutically.

No MeSH data available.


Related in: MedlinePlus

FLIM analysis of the effect of GSMs and HP on APP-CT positioning relative to the membrane . A) APP/APLP2 dKO cells co-transfected with myrGFP and wild-type APP-RFP were treated with vehicle control, fenofibrate (FF), celecoxib (cele), ibuprofen (ibu), indomethacin (indo), or flurbiprofen (flurbi). The donor lifetime shortened in cells treated with FF and cele, and increased in cells treated with ibu, indo and flurbi, reflecting increased and decreased proximity between the APP-CT and membrane, respectively, compared to that in cells treated with the DMSO vehicle. mean ± SD; *p < 0.05; **p < 0.001, ANOVA; n = 42-84 cells analyzed per condition in three independent experiments. B) PS1/2 dKO cells were co-transfected with myrGFP and APP-RFP, and treated with fenofibrate or ibuprofen. Neither ibuprofen nor fenofibrate treatment significantly changed the myrGFP lifetime in PS1/2 dKO cells. C) PS1/2 dKO cells (green bar) and PS1/2 dKO + wild-type PS1 cells (black bars) co-transfected with myrGFP and APP-RFP were treated with either DMSO or HP to prevent APP-PS1 interactions. Three to five independent experiments were performed. Data from a representative experiment is shown. n: number of cells analyzed in the experiment (*p < 0.01; **p < 0.05; n.s. - not significant; ANOVA).
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Figure 2: FLIM analysis of the effect of GSMs and HP on APP-CT positioning relative to the membrane . A) APP/APLP2 dKO cells co-transfected with myrGFP and wild-type APP-RFP were treated with vehicle control, fenofibrate (FF), celecoxib (cele), ibuprofen (ibu), indomethacin (indo), or flurbiprofen (flurbi). The donor lifetime shortened in cells treated with FF and cele, and increased in cells treated with ibu, indo and flurbi, reflecting increased and decreased proximity between the APP-CT and membrane, respectively, compared to that in cells treated with the DMSO vehicle. mean ± SD; *p < 0.05; **p < 0.001, ANOVA; n = 42-84 cells analyzed per condition in three independent experiments. B) PS1/2 dKO cells were co-transfected with myrGFP and APP-RFP, and treated with fenofibrate or ibuprofen. Neither ibuprofen nor fenofibrate treatment significantly changed the myrGFP lifetime in PS1/2 dKO cells. C) PS1/2 dKO cells (green bar) and PS1/2 dKO + wild-type PS1 cells (black bars) co-transfected with myrGFP and APP-RFP were treated with either DMSO or HP to prevent APP-PS1 interactions. Three to five independent experiments were performed. Data from a representative experiment is shown. n: number of cells analyzed in the experiment (*p < 0.01; **p < 0.05; n.s. - not significant; ANOVA).

Mentions: It has been reported recently [18,19] that Aβ42/40 ratio-modulating GSMs could directly bind to the APP substrate. Thus, we tested whether GSMs affect the Aβ42/40 ratio by altering APP membrane positioning. For this, APP/APLP2 dKO cells co-transfected with myrGFP and wild-type APP-RFP were treated with either Aβ42-raising (fenofibrate, celecoxib) or Aβ42-lowering (ibuprofen, indomethacin, flurbiprofen) GSMs. We found that fenofibrate and celecoxib treatment significantly decreased the lifetime of myrGFP donor, compared to the vehicle control treatment, indicating that they changed positioning of the APP-CT relative to the membrane in the same direction as Aβ42/40 ratio-raising APP FAD mutations (Figure 2A). Conversely, treatment with Aβ42-lowering GSMs increased the donor lifetime (Figure 2A). These findings support the idea that change in the positioning of APP-CT to the membrane reflects a change in the Aβ42/40 ratio, with shorter distance between the APP-CT and membrane correlating with a higher, and longer distance with a lower Aβ42/40 ratio.


Reciprocal relationship between APP positioning relative to the membrane and PS1 conformation.

Uemura K, Farner KC, Nasser-Ghodsi N, Jones P, Berezovska O - Mol Neurodegener (2011)

FLIM analysis of the effect of GSMs and HP on APP-CT positioning relative to the membrane . A) APP/APLP2 dKO cells co-transfected with myrGFP and wild-type APP-RFP were treated with vehicle control, fenofibrate (FF), celecoxib (cele), ibuprofen (ibu), indomethacin (indo), or flurbiprofen (flurbi). The donor lifetime shortened in cells treated with FF and cele, and increased in cells treated with ibu, indo and flurbi, reflecting increased and decreased proximity between the APP-CT and membrane, respectively, compared to that in cells treated with the DMSO vehicle. mean ± SD; *p < 0.05; **p < 0.001, ANOVA; n = 42-84 cells analyzed per condition in three independent experiments. B) PS1/2 dKO cells were co-transfected with myrGFP and APP-RFP, and treated with fenofibrate or ibuprofen. Neither ibuprofen nor fenofibrate treatment significantly changed the myrGFP lifetime in PS1/2 dKO cells. C) PS1/2 dKO cells (green bar) and PS1/2 dKO + wild-type PS1 cells (black bars) co-transfected with myrGFP and APP-RFP were treated with either DMSO or HP to prevent APP-PS1 interactions. Three to five independent experiments were performed. Data from a representative experiment is shown. n: number of cells analyzed in the experiment (*p < 0.01; **p < 0.05; n.s. - not significant; ANOVA).
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Figure 2: FLIM analysis of the effect of GSMs and HP on APP-CT positioning relative to the membrane . A) APP/APLP2 dKO cells co-transfected with myrGFP and wild-type APP-RFP were treated with vehicle control, fenofibrate (FF), celecoxib (cele), ibuprofen (ibu), indomethacin (indo), or flurbiprofen (flurbi). The donor lifetime shortened in cells treated with FF and cele, and increased in cells treated with ibu, indo and flurbi, reflecting increased and decreased proximity between the APP-CT and membrane, respectively, compared to that in cells treated with the DMSO vehicle. mean ± SD; *p < 0.05; **p < 0.001, ANOVA; n = 42-84 cells analyzed per condition in three independent experiments. B) PS1/2 dKO cells were co-transfected with myrGFP and APP-RFP, and treated with fenofibrate or ibuprofen. Neither ibuprofen nor fenofibrate treatment significantly changed the myrGFP lifetime in PS1/2 dKO cells. C) PS1/2 dKO cells (green bar) and PS1/2 dKO + wild-type PS1 cells (black bars) co-transfected with myrGFP and APP-RFP were treated with either DMSO or HP to prevent APP-PS1 interactions. Three to five independent experiments were performed. Data from a representative experiment is shown. n: number of cells analyzed in the experiment (*p < 0.01; **p < 0.05; n.s. - not significant; ANOVA).
Mentions: It has been reported recently [18,19] that Aβ42/40 ratio-modulating GSMs could directly bind to the APP substrate. Thus, we tested whether GSMs affect the Aβ42/40 ratio by altering APP membrane positioning. For this, APP/APLP2 dKO cells co-transfected with myrGFP and wild-type APP-RFP were treated with either Aβ42-raising (fenofibrate, celecoxib) or Aβ42-lowering (ibuprofen, indomethacin, flurbiprofen) GSMs. We found that fenofibrate and celecoxib treatment significantly decreased the lifetime of myrGFP donor, compared to the vehicle control treatment, indicating that they changed positioning of the APP-CT relative to the membrane in the same direction as Aβ42/40 ratio-raising APP FAD mutations (Figure 2A). Conversely, treatment with Aβ42-lowering GSMs increased the donor lifetime (Figure 2A). These findings support the idea that change in the positioning of APP-CT to the membrane reflects a change in the Aβ42/40 ratio, with shorter distance between the APP-CT and membrane correlating with a higher, and longer distance with a lower Aβ42/40 ratio.

Bottom Line: Several familial Alzheimer disease (FAD) mutations within the transmembrane region of the amyloid precursor protein (APP) increase the Aβ42/40 ratio without increasing total Aβ production.In the present study, we analyzed the impact of FAD mutations and γ-secretase modulators (GSMs) that alter the Aβ42/40 ratio on APP C-terminus (CT) positioning relative to the membrane, reasoning that changes in the alignment of the APP intramembranous domain and presenilin 1 (PS1) may impact the PS1/γ-secretase cleavage site on APP.Thus, we propose that there is a reciprocal relationship between APP-CT positioning relative to the membrane and PS1 conformation, suggesting that factors that modulate either APP positioning in the membrane or PS1 conformation could be exploited therapeutically.

View Article: PubMed Central - HTML - PubMed

Affiliation: Alzheimer Research Unit, MassGeneral Institute for Neurodegenerative Diseases, Massachusetts General Hospital, Charlestown, MA 02129, USA. oberezovska@partners.org.

ABSTRACT

Background: Several familial Alzheimer disease (FAD) mutations within the transmembrane region of the amyloid precursor protein (APP) increase the Aβ42/40 ratio without increasing total Aβ production. In the present study, we analyzed the impact of FAD mutations and γ-secretase modulators (GSMs) that alter the Aβ42/40 ratio on APP C-terminus (CT) positioning relative to the membrane, reasoning that changes in the alignment of the APP intramembranous domain and presenilin 1 (PS1) may impact the PS1/γ-secretase cleavage site on APP.

Results: By using a Förster resonance energy transfer (FRET)-based technique, fluorescent lifetime imaging microscopy (FLIM), we show that Aβ42/40 ratio-modulating factors which target either APP substrate or PS1/γ-secretase affect proximity of the APP-CT to the membrane and change PS1 conformation.

Conclusions: Thus, we propose that there is a reciprocal relationship between APP-CT positioning relative to the membrane and PS1 conformation, suggesting that factors that modulate either APP positioning in the membrane or PS1 conformation could be exploited therapeutically.

No MeSH data available.


Related in: MedlinePlus