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Y682G Mutation of Amyloid Precursor Protein Promotes Endo-Lysosomal Dysfunction by Disrupting APP-SorLA Interaction.

La Rosa LR, Perrone L, Nielsen MS, Calissano P, Andersen OM, Matrone C - Front Cell Neurosci (2015)

Bottom Line: Here, we report that Y682G mutation affects formation of the APP complex with sortilin-related receptor (SorLA), resulting in endo-lysosomal dysfunctions and neuronal degeneration.These results might open new possibilities in comprehending the role played by SorLA in its interaction with APP and in the progression of neuronal degeneration.In addition, they further underline the crucial role played by Y682 residue in controlling APP trafficking in neurons.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cellular Biology and Neurobiology, National Council of Research of Rome , Rome , Italy.

ABSTRACT
The intracellular transport and localization of amyloid precursor protein (APP) are critical determinants of APP processing and β-amyloid peptide production, thus crucially important for the pathophysiology of Alzheimer's disease (AD). Notably, the C-terminal Y682ENPTY687 domain of APP binds to specific adaptors controlling APP trafficking and sorting in neurons. Mutation on the Y682 residue to glycine (Y682G) leads to altered APP sorting in hippocampal neurons that favors its accumulation in intracellular compartments and the release of soluble APPα. Such alterations induce premature aging and learning and cognitive deficits in APP Y682G mutant mice (APP (YG/YG) ). Here, we report that Y682G mutation affects formation of the APP complex with sortilin-related receptor (SorLA), resulting in endo-lysosomal dysfunctions and neuronal degeneration. Moreover, disruption of the APP/SorLA complex changes the trafficking pathway of SorLA, with its consequent increase in secretion outside neurons. Mutations in the SorLA gene are a prognostic factor in AD, and changes in SorLA levels in cerebrospinal fluid are predictive of AD in humans. These results might open new possibilities in comprehending the role played by SorLA in its interaction with APP and in the progression of neuronal degeneration. In addition, they further underline the crucial role played by Y682 residue in controlling APP trafficking in neurons.

No MeSH data available.


Related in: MedlinePlus

Lysosome activity is impaired in APPYG/YG hippocampal neurons. (A) Western blot analysis of cathepsin D in hippocampi from WT and APPYG/YG (YG) mice and (B) the corresponding densitometric analysis. The data were normalized to the corresponding GADPH values. The optical density (OD) is expressed as a percentage (mean ± SEM) of the proCD values from WT samples. n = 3. *p < 0.05. (C) Cathepsin D (CD) and cathepsin B (CB) cysteine protease activity in WT and APPYG/YG (YG) hippocampal neurons. The samples were collected and analyzed according to the procedure suggested by the manufacturer and described in the Section “Materials and Methods.” The relative activity is expressed as fluorescent units (FU)/mg protein. The data are expressed as mean ± SEM. n = 3. *p < 0.05.
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Figure 3: Lysosome activity is impaired in APPYG/YG hippocampal neurons. (A) Western blot analysis of cathepsin D in hippocampi from WT and APPYG/YG (YG) mice and (B) the corresponding densitometric analysis. The data were normalized to the corresponding GADPH values. The optical density (OD) is expressed as a percentage (mean ± SEM) of the proCD values from WT samples. n = 3. *p < 0.05. (C) Cathepsin D (CD) and cathepsin B (CB) cysteine protease activity in WT and APPYG/YG (YG) hippocampal neurons. The samples were collected and analyzed according to the procedure suggested by the manufacturer and described in the Section “Materials and Methods.” The relative activity is expressed as fluorescent units (FU)/mg protein. The data are expressed as mean ± SEM. n = 3. *p < 0.05.

Mentions: We next investigated whether the observed accumulation of APP in Lamp1-positive vesicles leads to a defect in lysosomal activity. To test for lysosomal activity, we used western blotting (WB) to detect the conversion of immature to mature cathepsin D (CD), a lysosomal protease that is used as an indirect marker of lysosomal function (Luzio et al., 2007). The WB analysis of homogenates from WT and APPYG/YG neurons showed a significant decrease in the level of the two CD active fragments, which migrate at 32 and 14 kDa (CDm; Figures 3A,B). Furthermore, the enzymatic activity of CD and cathepsin B (CB) confirmed a significant reduction of lysosomal activity in neurons isolated from APPYG/YG mice (Figure 3C). These data clearly suggest impairment in the lysosomal machinery and a key role played by the Y682ENPTY687 domain in controlling APP trafficking in neurons and preventing lysosomal dysfunction. These results are also interesting when considering that a reduction of CD activity has been previously reported in brains from AD patients (Yang et al., 2011).


Y682G Mutation of Amyloid Precursor Protein Promotes Endo-Lysosomal Dysfunction by Disrupting APP-SorLA Interaction.

La Rosa LR, Perrone L, Nielsen MS, Calissano P, Andersen OM, Matrone C - Front Cell Neurosci (2015)

Lysosome activity is impaired in APPYG/YG hippocampal neurons. (A) Western blot analysis of cathepsin D in hippocampi from WT and APPYG/YG (YG) mice and (B) the corresponding densitometric analysis. The data were normalized to the corresponding GADPH values. The optical density (OD) is expressed as a percentage (mean ± SEM) of the proCD values from WT samples. n = 3. *p < 0.05. (C) Cathepsin D (CD) and cathepsin B (CB) cysteine protease activity in WT and APPYG/YG (YG) hippocampal neurons. The samples were collected and analyzed according to the procedure suggested by the manufacturer and described in the Section “Materials and Methods.” The relative activity is expressed as fluorescent units (FU)/mg protein. The data are expressed as mean ± SEM. n = 3. *p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4388009&req=5

Figure 3: Lysosome activity is impaired in APPYG/YG hippocampal neurons. (A) Western blot analysis of cathepsin D in hippocampi from WT and APPYG/YG (YG) mice and (B) the corresponding densitometric analysis. The data were normalized to the corresponding GADPH values. The optical density (OD) is expressed as a percentage (mean ± SEM) of the proCD values from WT samples. n = 3. *p < 0.05. (C) Cathepsin D (CD) and cathepsin B (CB) cysteine protease activity in WT and APPYG/YG (YG) hippocampal neurons. The samples were collected and analyzed according to the procedure suggested by the manufacturer and described in the Section “Materials and Methods.” The relative activity is expressed as fluorescent units (FU)/mg protein. The data are expressed as mean ± SEM. n = 3. *p < 0.05.
Mentions: We next investigated whether the observed accumulation of APP in Lamp1-positive vesicles leads to a defect in lysosomal activity. To test for lysosomal activity, we used western blotting (WB) to detect the conversion of immature to mature cathepsin D (CD), a lysosomal protease that is used as an indirect marker of lysosomal function (Luzio et al., 2007). The WB analysis of homogenates from WT and APPYG/YG neurons showed a significant decrease in the level of the two CD active fragments, which migrate at 32 and 14 kDa (CDm; Figures 3A,B). Furthermore, the enzymatic activity of CD and cathepsin B (CB) confirmed a significant reduction of lysosomal activity in neurons isolated from APPYG/YG mice (Figure 3C). These data clearly suggest impairment in the lysosomal machinery and a key role played by the Y682ENPTY687 domain in controlling APP trafficking in neurons and preventing lysosomal dysfunction. These results are also interesting when considering that a reduction of CD activity has been previously reported in brains from AD patients (Yang et al., 2011).

Bottom Line: Here, we report that Y682G mutation affects formation of the APP complex with sortilin-related receptor (SorLA), resulting in endo-lysosomal dysfunctions and neuronal degeneration.These results might open new possibilities in comprehending the role played by SorLA in its interaction with APP and in the progression of neuronal degeneration.In addition, they further underline the crucial role played by Y682 residue in controlling APP trafficking in neurons.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cellular Biology and Neurobiology, National Council of Research of Rome , Rome , Italy.

ABSTRACT
The intracellular transport and localization of amyloid precursor protein (APP) are critical determinants of APP processing and β-amyloid peptide production, thus crucially important for the pathophysiology of Alzheimer's disease (AD). Notably, the C-terminal Y682ENPTY687 domain of APP binds to specific adaptors controlling APP trafficking and sorting in neurons. Mutation on the Y682 residue to glycine (Y682G) leads to altered APP sorting in hippocampal neurons that favors its accumulation in intracellular compartments and the release of soluble APPα. Such alterations induce premature aging and learning and cognitive deficits in APP Y682G mutant mice (APP (YG/YG) ). Here, we report that Y682G mutation affects formation of the APP complex with sortilin-related receptor (SorLA), resulting in endo-lysosomal dysfunctions and neuronal degeneration. Moreover, disruption of the APP/SorLA complex changes the trafficking pathway of SorLA, with its consequent increase in secretion outside neurons. Mutations in the SorLA gene are a prognostic factor in AD, and changes in SorLA levels in cerebrospinal fluid are predictive of AD in humans. These results might open new possibilities in comprehending the role played by SorLA in its interaction with APP and in the progression of neuronal degeneration. In addition, they further underline the crucial role played by Y682 residue in controlling APP trafficking in neurons.

No MeSH data available.


Related in: MedlinePlus