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The Amyloid Precursor Protein Controls PIKfyve Function.

Balklava Z, Niehage C, Currinn H, Mellor L, Guscott B, Poulin G, Hoflack B, Wassmer T - PLoS ONE (2015)

Bottom Line: Loss of PIKfyve function by mutation causes profound neurodegeneration in mammals.Using C. elegans genetics we demonstrate that APP functionally cooperates with PIKfyve in vivo.This regulation is required for maintaining endosomal and neuronal function.

View Article: PubMed Central - PubMed

Affiliation: Aston University, School of Life and Health Sciences, Aston Triangle, Birmingham, B4 7ET, United Kingdom.

ABSTRACT
While the Amyloid Precursor Protein (APP) plays a central role in Alzheimer's disease, its cellular function still remains largely unclear. It was our goal to establish APP function which will provide insights into APP's implication in Alzheimer's disease. Using our recently developed proteo-liposome assay we established the interactome of APP's intracellular domain (known as AICD), thereby identifying novel APP interactors that provide mechanistic insights into APP function. By combining biochemical, cell biological and genetic approaches we validated the functional significance of one of these novel interactors. Here we show that APP binds the PIKfyve complex, an essential kinase for the synthesis of the endosomal phosphoinositide phosphatidylinositol-3,5-bisphosphate. This signalling lipid plays a crucial role in endosomal homeostasis and receptor sorting. Loss of PIKfyve function by mutation causes profound neurodegeneration in mammals. Using C. elegans genetics we demonstrate that APP functionally cooperates with PIKfyve in vivo. This regulation is required for maintaining endosomal and neuronal function. Our findings establish an unexpected role for APP in the regulation of endosomal phosphoinositide metabolism with dramatic consequences for endosomal biology and important implications for our understanding of Alzheimer's disease.

No MeSH data available.


Related in: MedlinePlus

APL-1 interacts genetically with the PIKfyve complex genes vacl-14 and ppk-3.(A) Mutations in apl-1, ppk-3 and vacl-14 led to the formation of vacuoles in the C. elegans intestine and hypoderm (indicated by arrows) apparent in the anterior tips of the worms as observed by Differential Interference Contrast (DIC) microscopy. Combination of apl-1, ppk-3 and vacl-14 mutations in double mutant worms strongly enhanced this phenotype (* indicate very large vacuoles), particularly evident in the apl-1(yn5) ppk-3(n2668) double mutant. (B) Box plots demonstrated that the number of vacuoles in apl-1/ppk-3 and apl-1/vacl-14 double mutants is significantly increased compared to the single mutants (Wilcoxon rank test, p<0.01, n≥20 per strain), demonstrating that APL-1 functionally interacts with the PPK-3 complex. This showed that the C-terminal domain of APL-1 is necessary for suppressing vacuole formation induced by loss of PPK-3 and VACL-14 activity. Bar, 50 μm.
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pone.0130485.g002: APL-1 interacts genetically with the PIKfyve complex genes vacl-14 and ppk-3.(A) Mutations in apl-1, ppk-3 and vacl-14 led to the formation of vacuoles in the C. elegans intestine and hypoderm (indicated by arrows) apparent in the anterior tips of the worms as observed by Differential Interference Contrast (DIC) microscopy. Combination of apl-1, ppk-3 and vacl-14 mutations in double mutant worms strongly enhanced this phenotype (* indicate very large vacuoles), particularly evident in the apl-1(yn5) ppk-3(n2668) double mutant. (B) Box plots demonstrated that the number of vacuoles in apl-1/ppk-3 and apl-1/vacl-14 double mutants is significantly increased compared to the single mutants (Wilcoxon rank test, p<0.01, n≥20 per strain), demonstrating that APL-1 functionally interacts with the PPK-3 complex. This showed that the C-terminal domain of APL-1 is necessary for suppressing vacuole formation induced by loss of PPK-3 and VACL-14 activity. Bar, 50 μm.

Mentions: Reduced PPK-3 activity by partial loss of function mutations in ppk-3 or deletion of its activator VACL-14 led to the formation of large vacuoles that are most easily visible in hypodermal cells ([33] and Fig 2). Interestingly, when analysing the apl-1(yn5) mutant we observed hypodermal vacuolation similar to that of ppk-3 and vacl-14 mutants. This showed that the apl-1(yn5) mutant phenocopies the partial loss of PPK-3 function (Fig 2 and [32]).


The Amyloid Precursor Protein Controls PIKfyve Function.

Balklava Z, Niehage C, Currinn H, Mellor L, Guscott B, Poulin G, Hoflack B, Wassmer T - PLoS ONE (2015)

APL-1 interacts genetically with the PIKfyve complex genes vacl-14 and ppk-3.(A) Mutations in apl-1, ppk-3 and vacl-14 led to the formation of vacuoles in the C. elegans intestine and hypoderm (indicated by arrows) apparent in the anterior tips of the worms as observed by Differential Interference Contrast (DIC) microscopy. Combination of apl-1, ppk-3 and vacl-14 mutations in double mutant worms strongly enhanced this phenotype (* indicate very large vacuoles), particularly evident in the apl-1(yn5) ppk-3(n2668) double mutant. (B) Box plots demonstrated that the number of vacuoles in apl-1/ppk-3 and apl-1/vacl-14 double mutants is significantly increased compared to the single mutants (Wilcoxon rank test, p<0.01, n≥20 per strain), demonstrating that APL-1 functionally interacts with the PPK-3 complex. This showed that the C-terminal domain of APL-1 is necessary for suppressing vacuole formation induced by loss of PPK-3 and VACL-14 activity. Bar, 50 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488396&req=5

pone.0130485.g002: APL-1 interacts genetically with the PIKfyve complex genes vacl-14 and ppk-3.(A) Mutations in apl-1, ppk-3 and vacl-14 led to the formation of vacuoles in the C. elegans intestine and hypoderm (indicated by arrows) apparent in the anterior tips of the worms as observed by Differential Interference Contrast (DIC) microscopy. Combination of apl-1, ppk-3 and vacl-14 mutations in double mutant worms strongly enhanced this phenotype (* indicate very large vacuoles), particularly evident in the apl-1(yn5) ppk-3(n2668) double mutant. (B) Box plots demonstrated that the number of vacuoles in apl-1/ppk-3 and apl-1/vacl-14 double mutants is significantly increased compared to the single mutants (Wilcoxon rank test, p<0.01, n≥20 per strain), demonstrating that APL-1 functionally interacts with the PPK-3 complex. This showed that the C-terminal domain of APL-1 is necessary for suppressing vacuole formation induced by loss of PPK-3 and VACL-14 activity. Bar, 50 μm.
Mentions: Reduced PPK-3 activity by partial loss of function mutations in ppk-3 or deletion of its activator VACL-14 led to the formation of large vacuoles that are most easily visible in hypodermal cells ([33] and Fig 2). Interestingly, when analysing the apl-1(yn5) mutant we observed hypodermal vacuolation similar to that of ppk-3 and vacl-14 mutants. This showed that the apl-1(yn5) mutant phenocopies the partial loss of PPK-3 function (Fig 2 and [32]).

Bottom Line: Loss of PIKfyve function by mutation causes profound neurodegeneration in mammals.Using C. elegans genetics we demonstrate that APP functionally cooperates with PIKfyve in vivo.This regulation is required for maintaining endosomal and neuronal function.

View Article: PubMed Central - PubMed

Affiliation: Aston University, School of Life and Health Sciences, Aston Triangle, Birmingham, B4 7ET, United Kingdom.

ABSTRACT
While the Amyloid Precursor Protein (APP) plays a central role in Alzheimer's disease, its cellular function still remains largely unclear. It was our goal to establish APP function which will provide insights into APP's implication in Alzheimer's disease. Using our recently developed proteo-liposome assay we established the interactome of APP's intracellular domain (known as AICD), thereby identifying novel APP interactors that provide mechanistic insights into APP function. By combining biochemical, cell biological and genetic approaches we validated the functional significance of one of these novel interactors. Here we show that APP binds the PIKfyve complex, an essential kinase for the synthesis of the endosomal phosphoinositide phosphatidylinositol-3,5-bisphosphate. This signalling lipid plays a crucial role in endosomal homeostasis and receptor sorting. Loss of PIKfyve function by mutation causes profound neurodegeneration in mammals. Using C. elegans genetics we demonstrate that APP functionally cooperates with PIKfyve in vivo. This regulation is required for maintaining endosomal and neuronal function. Our findings establish an unexpected role for APP in the regulation of endosomal phosphoinositide metabolism with dramatic consequences for endosomal biology and important implications for our understanding of Alzheimer's disease.

No MeSH data available.


Related in: MedlinePlus