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LRP1 Downregulates the Alzheimer's β-Secretase BACE1 by Modulating Its Intraneuronal Trafficking(1,2,3).

Tanokashira D, Motoki K, Minegishi S, Hosaka A, Mamada N, Tamaoka A, Okada T, Lakshmana MK, Araki W - eNeuro (2015)

Bottom Line: Here, we present evidence that low-density lipoprotein receptor-related protein 1 (LRP1), a multi-functional receptor, has a previously unrecognized function to regulate BACE1 in neurons.We show that deficiency of LRP1 exerts promotive effects on the protein expression and function of BACE1, whereas expression of LRP-L4, a functional LRP1 mini-receptor, specifically decreases BACE1 levels in both human embryonic kidney (HEK) 293 cells and rat primary neurons, leading to reduced Aβ production.Our subsequent analyses further demonstrate that (1) both endogenous and exogenous BACE1 and LRP1 interact with each other and are colocalized in soma and neurites of primary neurons, (2) LRP1 reduces the protein stability and cell-surface expression of BACE1, and (3) LRP1 facilitates the shift in intracellular localization of BACE1 from early to late endosomes, thereby promoting lysosomal degradation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Demyelinating Disease and Aging, National Institute of Neuroscience , NCNP, Kodaira, Tokyo 187-8502, Japan.

ABSTRACT
The β-secretase called BACE1 is a membrane-associated protease that initiates the generation of amyloid β-protein (Aβ), a key event in Alzheimer's disease (AD). However, the mechanism of intraneuronal regulation of BACE1 is poorly understood. Here, we present evidence that low-density lipoprotein receptor-related protein 1 (LRP1), a multi-functional receptor, has a previously unrecognized function to regulate BACE1 in neurons. We show that deficiency of LRP1 exerts promotive effects on the protein expression and function of BACE1, whereas expression of LRP-L4, a functional LRP1 mini-receptor, specifically decreases BACE1 levels in both human embryonic kidney (HEK) 293 cells and rat primary neurons, leading to reduced Aβ production. Our subsequent analyses further demonstrate that (1) both endogenous and exogenous BACE1 and LRP1 interact with each other and are colocalized in soma and neurites of primary neurons, (2) LRP1 reduces the protein stability and cell-surface expression of BACE1, and (3) LRP1 facilitates the shift in intracellular localization of BACE1 from early to late endosomes, thereby promoting lysosomal degradation. These findings establish that LRP1 specifically downregulates BACE1 by modulating its intraneuronal trafficking and stability through protein interaction and highlight LRP1 as a potential therapeutic target in AD.

No MeSH data available.


Related in: MedlinePlus

Subcellular localization of endogenous BACE1 and LRP1 in neurons. A, Primary neurons grown on coverslips were analyzed by triple-immunofluorescence staining with anti-BACE1 (red), anti-LRP1 (blue), and anti-EEA1 (green), as described in Materials and Methods. Overlapping immunoreactivities were significantly observed in both soma and neurites of neurons. B, Triple-immunofluorescence staining with anti-BACE1, anti-LRP1, and anti-rab7 exhibited overlapping immunoreactivities mainly in soma of neurons. C, Triple-immunofluorescence staining with anti-BACE1, anti-LRP1, and anti-GM130 displayed only limited overlapping immunoreactivities in soma of neurons. Scale bars, 20 μm.
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Figure 6: Subcellular localization of endogenous BACE1 and LRP1 in neurons. A, Primary neurons grown on coverslips were analyzed by triple-immunofluorescence staining with anti-BACE1 (red), anti-LRP1 (blue), and anti-EEA1 (green), as described in Materials and Methods. Overlapping immunoreactivities were significantly observed in both soma and neurites of neurons. B, Triple-immunofluorescence staining with anti-BACE1, anti-LRP1, and anti-rab7 exhibited overlapping immunoreactivities mainly in soma of neurons. C, Triple-immunofluorescence staining with anti-BACE1, anti-LRP1, and anti-GM130 displayed only limited overlapping immunoreactivities in soma of neurons. Scale bars, 20 μm.

Mentions: Finally, we used triple immunofluorescence staining to analyze the subcellular localization of endogenous BACE1 and LRP1 in neurons. The results revealed that both endogenous BACE1 and LRP1 immmunoreactivities were clearly colocalized with EEA1 in soma and neurites and partially with rab7 mainly in soma (Fig. 6A,B). In contrast, only limited colocalization of endogenous BACE1, LRP1, and GM130 (a Golgi marker) was observed in soma (Fig. 6C). These data clearly suggest the association of endogenous BACE1 and LRP1 in endosomal compartments, particularly early endosomes, of neurons.


LRP1 Downregulates the Alzheimer's β-Secretase BACE1 by Modulating Its Intraneuronal Trafficking(1,2,3).

Tanokashira D, Motoki K, Minegishi S, Hosaka A, Mamada N, Tamaoka A, Okada T, Lakshmana MK, Araki W - eNeuro (2015)

Subcellular localization of endogenous BACE1 and LRP1 in neurons. A, Primary neurons grown on coverslips were analyzed by triple-immunofluorescence staining with anti-BACE1 (red), anti-LRP1 (blue), and anti-EEA1 (green), as described in Materials and Methods. Overlapping immunoreactivities were significantly observed in both soma and neurites of neurons. B, Triple-immunofluorescence staining with anti-BACE1, anti-LRP1, and anti-rab7 exhibited overlapping immunoreactivities mainly in soma of neurons. C, Triple-immunofluorescence staining with anti-BACE1, anti-LRP1, and anti-GM130 displayed only limited overlapping immunoreactivities in soma of neurons. Scale bars, 20 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4596091&req=5

Figure 6: Subcellular localization of endogenous BACE1 and LRP1 in neurons. A, Primary neurons grown on coverslips were analyzed by triple-immunofluorescence staining with anti-BACE1 (red), anti-LRP1 (blue), and anti-EEA1 (green), as described in Materials and Methods. Overlapping immunoreactivities were significantly observed in both soma and neurites of neurons. B, Triple-immunofluorescence staining with anti-BACE1, anti-LRP1, and anti-rab7 exhibited overlapping immunoreactivities mainly in soma of neurons. C, Triple-immunofluorescence staining with anti-BACE1, anti-LRP1, and anti-GM130 displayed only limited overlapping immunoreactivities in soma of neurons. Scale bars, 20 μm.
Mentions: Finally, we used triple immunofluorescence staining to analyze the subcellular localization of endogenous BACE1 and LRP1 in neurons. The results revealed that both endogenous BACE1 and LRP1 immmunoreactivities were clearly colocalized with EEA1 in soma and neurites and partially with rab7 mainly in soma (Fig. 6A,B). In contrast, only limited colocalization of endogenous BACE1, LRP1, and GM130 (a Golgi marker) was observed in soma (Fig. 6C). These data clearly suggest the association of endogenous BACE1 and LRP1 in endosomal compartments, particularly early endosomes, of neurons.

Bottom Line: Here, we present evidence that low-density lipoprotein receptor-related protein 1 (LRP1), a multi-functional receptor, has a previously unrecognized function to regulate BACE1 in neurons.We show that deficiency of LRP1 exerts promotive effects on the protein expression and function of BACE1, whereas expression of LRP-L4, a functional LRP1 mini-receptor, specifically decreases BACE1 levels in both human embryonic kidney (HEK) 293 cells and rat primary neurons, leading to reduced Aβ production.Our subsequent analyses further demonstrate that (1) both endogenous and exogenous BACE1 and LRP1 interact with each other and are colocalized in soma and neurites of primary neurons, (2) LRP1 reduces the protein stability and cell-surface expression of BACE1, and (3) LRP1 facilitates the shift in intracellular localization of BACE1 from early to late endosomes, thereby promoting lysosomal degradation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Demyelinating Disease and Aging, National Institute of Neuroscience , NCNP, Kodaira, Tokyo 187-8502, Japan.

ABSTRACT
The β-secretase called BACE1 is a membrane-associated protease that initiates the generation of amyloid β-protein (Aβ), a key event in Alzheimer's disease (AD). However, the mechanism of intraneuronal regulation of BACE1 is poorly understood. Here, we present evidence that low-density lipoprotein receptor-related protein 1 (LRP1), a multi-functional receptor, has a previously unrecognized function to regulate BACE1 in neurons. We show that deficiency of LRP1 exerts promotive effects on the protein expression and function of BACE1, whereas expression of LRP-L4, a functional LRP1 mini-receptor, specifically decreases BACE1 levels in both human embryonic kidney (HEK) 293 cells and rat primary neurons, leading to reduced Aβ production. Our subsequent analyses further demonstrate that (1) both endogenous and exogenous BACE1 and LRP1 interact with each other and are colocalized in soma and neurites of primary neurons, (2) LRP1 reduces the protein stability and cell-surface expression of BACE1, and (3) LRP1 facilitates the shift in intracellular localization of BACE1 from early to late endosomes, thereby promoting lysosomal degradation. These findings establish that LRP1 specifically downregulates BACE1 by modulating its intraneuronal trafficking and stability through protein interaction and highlight LRP1 as a potential therapeutic target in AD.

No MeSH data available.


Related in: MedlinePlus