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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 overexpression, while able to rescue partial loss of PPK-3 function, failed to rescue the ppk-3(mc46)  allele.(A) Expression of APL-1::GFP failed to rescue lethality of ppk-3  animals and failed to rescue vacuolation in apl-1::GFP; ppk-3(mc46) animals. Bar, 50μm. (B) Quantification of the relative vacuolated area in ppk-3(mc46) and apl-1::GFP; ppk-3(mc46) animals showed that APL-1 overexpression failed to rescue complete loss of PPK-3 function (n≥38, p = 0.73 (two-tailed t-test), suggesting that APL-1 functions upstream of PPK-3.
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pone.0130485.g004: APL-1 overexpression, while able to rescue partial loss of PPK-3 function, failed to rescue the ppk-3(mc46) allele.(A) Expression of APL-1::GFP failed to rescue lethality of ppk-3 animals and failed to rescue vacuolation in apl-1::GFP; ppk-3(mc46) animals. Bar, 50μm. (B) Quantification of the relative vacuolated area in ppk-3(mc46) and apl-1::GFP; ppk-3(mc46) animals showed that APL-1 overexpression failed to rescue complete loss of PPK-3 function (n≥38, p = 0.73 (two-tailed t-test), suggesting that APL-1 functions upstream of PPK-3.

Mentions: PIKfyve functions as part of a conserved protein complex together with its co-activators Vac14 and Fig 4, (also known as ArPIKfyve and Sac3, respectively) [23, 24]. Crucially, mouse Fig 4 loss-of-function mutations or Vac14 knock-out mutants not only reduce PI(3,5)P2 levels but also lead to profound neurodegeneration, resulting in perinatal death of the animals [21, 25]. Furthermore, mutations identified in the human Fig 4 gene lead to neurodegeneration in humans including Charcot-Marie-Tooth syndrome and Amyotrophic Lateral Sclerosis [21, 26].


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 overexpression, while able to rescue partial loss of PPK-3 function, failed to rescue the ppk-3(mc46)  allele.(A) Expression of APL-1::GFP failed to rescue lethality of ppk-3  animals and failed to rescue vacuolation in apl-1::GFP; ppk-3(mc46) animals. Bar, 50μm. (B) Quantification of the relative vacuolated area in ppk-3(mc46) and apl-1::GFP; ppk-3(mc46) animals showed that APL-1 overexpression failed to rescue complete loss of PPK-3 function (n≥38, p = 0.73 (two-tailed t-test), suggesting that APL-1 functions upstream of PPK-3.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0130485.g004: APL-1 overexpression, while able to rescue partial loss of PPK-3 function, failed to rescue the ppk-3(mc46) allele.(A) Expression of APL-1::GFP failed to rescue lethality of ppk-3 animals and failed to rescue vacuolation in apl-1::GFP; ppk-3(mc46) animals. Bar, 50μm. (B) Quantification of the relative vacuolated area in ppk-3(mc46) and apl-1::GFP; ppk-3(mc46) animals showed that APL-1 overexpression failed to rescue complete loss of PPK-3 function (n≥38, p = 0.73 (two-tailed t-test), suggesting that APL-1 functions upstream of PPK-3.
Mentions: PIKfyve functions as part of a conserved protein complex together with its co-activators Vac14 and Fig 4, (also known as ArPIKfyve and Sac3, respectively) [23, 24]. Crucially, mouse Fig 4 loss-of-function mutations or Vac14 knock-out mutants not only reduce PI(3,5)P2 levels but also lead to profound neurodegeneration, resulting in perinatal death of the animals [21, 25]. Furthermore, mutations identified in the human Fig 4 gene lead to neurodegeneration in humans including Charcot-Marie-Tooth syndrome and Amyotrophic Lateral Sclerosis [21, 26].

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