• AICD
• APP
• Alzheimer’s disease
• NPTY
• kinases

• Humans
• Amyloid beta-Protein Precursor/metabolism
• Amyloid beta-Peptides/metabolism
• Axonal Transport
• Alzheimer Disease/metabolism
• Axons/metabolism

• R01 NS023868 NINDS NIH HHS
• R01 NS041170 NINDS NIH HHS
• R01 NS023868 NIH HHS
• R01 NS041170 NIH HHS

• Allosteric modulation
• Aβ oligomers
• Catalytic pockets
• Drug discovery
• Proteolytic enzymes

• Aging
• Calcium homeostasis
• Neuromuscular disorder
• Oxidative stress
• SERCA
• Skeletal muscle

Background: Alzheimer’s disease (AD) is a devastating neurodegenerative disease without guidelines for early diagnosis or personalized treatment. Previous studies have highlighted a crucial role of increasing phosphorylation levels of the amyloid precursor protein (APP) Tyr682 residue in predicting neuronal deficits in AD patients. However, the lack of a method for the identification and quantification of Tyr682 phosphorylation levels prevents its potential clinical applications. Methods: Here we report a method to identify and quantify APP Tyr682 phosphorylation levels in blood mononuclear cells of AD patients by tandem mass spectrometry (tMS). Results: This method showed excellent sensitivity with detection and quantification limits set respectively at 0.035 and 0.082 ng injected for the phosphorylated peptide and at 0.02 and 0.215 ng injected for the non-phosphorylated peptide. The average levels of both peptides were quantified in transfected HELA cells (2.48 and 3.53 ng/μg of protein, respectively). Preliminary data on 3 AD patients showed quantifiable levels of phosphorylated peptide (0.10–0.15 ng/μg of protein) and below the LOQ level of non-phosphorylated peptide (0.13 ng/μg of protein). Conclusion: This method could allow the identification of patients with increased APP Tyr682 phosphorylation and allow early characterization of molecular changes prior to the appearance of clinical signs.

• APP Tyr682 phosphorylation
• Alzheimer’s disease
• targeted peptide analysis

• Amino Acid Sequence
• Amyloid beta-Protein Precursor/blood
• Amyloid beta-Protein Precursor/chemistry
• Calibration
• Cell Line
• Humans
• Leukocytes, Mononuclear/metabolism
• Phosphoproteins/metabolism
• Phosphorylation
• Reproducibility of Results
• Tandem Mass Spectrometry
• Tyrosine/metabolism

• Fyn tyrosine kinase
• Tyr682 residue
• YENPTY domain
• amyloid beta
• amyloid precursor protein

• Adult
• Aged
• Aged, 80 and over
• Alzheimer Disease/metabolism
• Alzheimer Disease/pathology
• Amyloid beta-Protein Precursor/genetics
• Amyloid beta-Protein Precursor/metabolism
• Biomarkers/metabolism
• Cells, Cultured
• Female
• Humans
• Induced Pluripotent Stem Cells/metabolism
• Male
• Middle Aged
• Neural Stem Cells/metabolism
• Neurons/metabolism
• Phosphorylation/drug effects
• Phosphorylation/genetics
• Protein Kinase Inhibitors/pharmacology
• Proto-Oncogene Proteins c-fyn/antagonists & inhibitors
• Proto-Oncogene Proteins c-fyn/genetics
• Proto-Oncogene Proteins c-fyn/metabolism
• Transfection
• Tyrosine/metabolism

• Alzheimer’s disease
• Amyloid precursor protein
• Aβ
• Fyn tyrosine kinase
• Tyr(682) residue phosphorylation
• Y(682)ENPTY(68)

• Alzheimer disease
• CD2AP
• CIN85
• Rab
• Rab7
• amyloid precursor protein (APP)
• endosome
• membrane trafficking
• protein degradation

• Cell Movement/physiology
• HEK293 Cells
• Humans
• Membrane Proteins/metabolism
• Nerve Tissue Proteins/metabolism
• Neurons/metabolism
• Protein Transport/physiology
• Receptors, Metabotropic Glutamate/metabolism

• APP trafficking
• Calsyntenin
• LRP1
• SorCS1c
• SorLA
• Sortilin

• APP
• Alzheimer's disease
• Fyn kinase
• Presenilin mutations
• Tyrosine phosphorylation

Following the discovery that the amyloid precursor protein (APP) is the source of β-amyloid peptides (Aβ) that accumulate in Alzheimer’s disease (AD), structural analyses suggested that the holoprotein resembles a transmembrane receptor. Initial studies using reconstituted membranes demonstrated that APP can directly interact with the heterotrimeric G protein Gαo (but not other G proteins) via an evolutionarily G protein-binding motif in its cytoplasmic domain. Subsequent investigations in cell culture showed that antibodies against the extracellular domain of APP could stimulate Gαo activity, presumably mimicking endogenous APP ligands. In addition, chronically activating wild type APP or overexpressing mutant APP isoforms linked with familial AD could provoke Go-dependent neurotoxic responses, while biochemical assays using human brain samples suggested that the endogenous APP-Go interactions are perturbed in AD patients. More recently, several G protein-dependent pathways have been implicated in the physiological roles of APP, coupled with evidence that APP interacts both physically and functionally with Gαo in a variety of contexts. Work in insect models has demonstrated that the APP ortholog APPL directly interacts with Gαo in motile neurons, whereby APPL-Gαo signaling regulates the response of migratory neurons to ligands encountered in the developing nervous system. Concurrent studies using cultured mammalian neurons and organotypic hippocampal slice preparations have shown that APP signaling transduces the neuroprotective effects of soluble sAPPα fragments via modulation of the PI3K/Akt pathway, providing a mechanism for integrating the stress and survival responses regulated by APP. Notably, this effect was also inhibited by pertussis toxin, indicating an essential role for Gαo/i proteins. Unexpectedly, C-terminal fragments (CTFs) derived from APP have also been found to interact with Gαs, whereby CTF-Gαs signaling can promote neurite outgrowth via adenylyl cyclase/PKA-dependent pathways. These reports offer the intriguing perspective that G protein switching might modulate APP-dependent responses in a context-dependent manner. In this review, we provide an up-to-date perspective on the model that APP plays a variety of roles as an atypical G protein-coupled receptor in both the developing and adult nervous system, and we discuss the hypothesis that disruption of these normal functions might contribute to the progressive neuropathologies that typify AD.

• APPL
• Alzheimer’s disease
• Drosophila
• Gαo
• Manduca
• amyloid precursor protein
• migration
• stress signaling

Mint/X11 is one of the four neuronal trafficking adaptors that interact with amyloid precursor protein (APP) and are linked with its cleavage to generate β‐amyloid peptide, a key player in the pathology of Alzheimer's disease. How APP switches between adaptors at different stages of the secretory pathway is poorly understood. Here, we show that tyrosine phosphorylation of Mint1 regulates the destination of APP. A canonical SH2‐binding motif (²⁰²YEEI) was identified in the N‐terminus of Mint1 that is phosphorylated on tyrosine by C‐Src and recruits the active kinase for sequential phosphorylation of further tyrosines (Y191 and Y187). A single Y202F mutation in the Mint1 N‐terminus inhibits C‐Src binding and tyrosine phosphorylation. Previous studies observed that co‐expression of wild‐type Mint1 and APP causes accumulation of APP in the trans‐Golgi. Unphosphorylatable Mint1 (Y202F) or pharmacological inhibition of Src reduced the accumulation of APP in the trans‐Golgi of heterologous cells. A similar result was observed in cultured rat hippocampal neurons where Mint1(Y202F) permitted the trafficking of APP to more distal neurites than the wild‐type protein. These data underline the importance of the tyrosine phosphorylation of Mint1 as a critical switch for determining the destination of APP.

The regulation of amyloid precursor protein (APP) trafficking is poorly understood. We have discovered that the APP adapter, Mint1, is phosphorylated by C‐Src kinase. Mint1 causes APP accumulation in the trans‐Golgi network, whereas inhibition of Src or mutation of Mint1‐Y202 permits APP recycling. The phosphorylation status of Mint1 could impact on the pathological trafficking of APP in Alzheimer's disease.

• Mint1
• Src
• amyloid precursor protein
• intracellular trafficking
• protein phosphorylation
• tyrosine kinase

XB130 and Tks5 interact endogenously and form a complex with Src tyrosine kinase. Tks5, like XB130, plays a role in cell proliferation and cell survival, and the interaction between XB130 and Tks5 is critical for regulation of Src-mediated cell proliferation and survival.

The scaffold protein XB130 regulates cell growth, survival, and migration. Yeast two-hybrid screening suggests that XB130 interacts with another scaffold protein, Tks5. We hypothesized that XB130 and Tks5 form a macromolecular complex to mediate signal transduction cascades for the regulation of cell growth and survival. Coimmunoprecipitation demonstrated that XB130 and Tks5 interact endogenously and form a complex with Src tyrosine kinase. Structure–function studies showed that the fifth SH3 domain of Tks5 binds to the N-terminus of XB130, which contains polyproline-rich motifs. Cell growth and survival studies revealed that down-regulation of XB130 and/or Tks5 reduced cell proliferation, resulting in cell cycle inhibition at the G1 phase and increased caspase 3 activity and apoptosis. Moreover, cell proliferation and survival were increased by overexpression of XB130 or Tks5 but decreased when XB130/Tks5 binding was disrupted by overexpression of XB130 N-terminal deleted mutant and/or Tks5 fifth SH3 domain W1108A mutant. Furthermore, down-regulation of XB130 and/or Tks5 inhibited serum- and growth factor–induced Src activation and downstream phosphorylation of PI3K and Akt. Our results suggest that Tks5, similar to XB130, plays a role in cell proliferation and cell survival and that the interaction between XB130 and Tks5 appears to be critical for regulation of Src-mediated cellular homeostasis.

• Fe65
• Jagged1
• Lysosome
• Neuralized-like 1
• Proteasome
• Protein degradation

The β-amyloid (Aβ) peptide has been postulated to be a key determinant in the pathogenesis of Alzheimer’s disease (AD). Aβ is produced through sequential cleavage of the β-amyloid precursor protein (APP) by β- and γ-secretases. APP and relevant secretases are transmembrane proteins and traffic through the secretory pathway in a highly regulated fashion. Perturbation of their intracellular trafficking may affect dynamic interactions among these proteins, thus altering Aβ generation and accelerating disease pathogenesis. Herein, we review recent progress elucidating the regulation of intracellular trafficking of these essential protein components in AD.

• A4 precursor protein-binding family B member 1
• ARF6
• Rac1
• amyloid-β
• neurons

The processing of Amyloid precursor protein (APP) is multifaceted, comprising of protein transport, internalization and sequential proteolysis. However, the exact mechanism of APP intracellular trafficking and distribution remains unclear. To determine the interaction between sortilin and APP and the effect of sortilin on APP trafficking and processing, we studied the binding site and its function by mapping experiments, colocalization, coimmunoprecipitation and sucrose gradient fractionation. We identified for the first time that sortilin interacts with APP at both N- and C-terminal regions. The sortilin-FLVHRY (residues 787–792) and APP-NPTYKFFE (residues 759–766) motifs are crucial for the C-terminal interaction. We also found that lack of the FLVHRY motif reduces APP lysosomal targeting and increases APP distribution in lipid rafts in co-transfected HEK293 cells. These results are consistent with our in vivo data where sortilin knockout mice showed a decrease of APP lysosomal distribution and an increase of APP in lipid rafts. We further confirmed that overexpression of sortilin-FLVHRY mutants failed to rescue the lysosomal degradation of APP. Thus, our data suggests that sortilin is implicated in APP lysosomal and lipid raft targeting via its carboxyl-terminal F/YXXXXF/Y motif. Our study provides new molecular insights into APP trafficking and processing.

Platelets are the first peripheral source of amyloid precursor protein (APP). They possess the proteolytic machinery to produce Aβ and fragments similar to those produced in neurons, and thus offer an ex-vivo model to study APP processing and changes associated with Alzheimer’s disease (AD). Platelet process APP mostly through the α-secretase pathway to release soluble APP (sAPP). They produce small amounts of Aβ, predominantly Aβ₄₀ over Aβ₄₂. sAPP and Aβ are stored in α-granules and are released upon platelet activation by thrombin and collagen, and agents inducing platelet degranulation. A small proportion of full-length APP is present at the platelet surface and this increases by 3-fold upon platelet activation. Immunoblotting of platelet lysates detects APP as isoforms of 130 kDa and 106-110 kDa. The ratio of these of APP isoforms is significantly lower in patients with AD and mild cognitive impairment (MCI) than in healthy controls. This ratio follows a decrease that parallels cognitive decline and can predict conversion from MCI to AD. Alterations in the levels of α-secretase ADAM10 and in the enzymatic activities of α- and β-secretase observed in platelets of patients with AD are consistent with increased processing through the amyloidogenic pathway. β-APP cleaving enzyme activity is increased by 24% in platelet membranes of patients with MCI and by 17% in those with AD. Reports of changes in platelet APP expression with MCI and AD have been promising so far and merit further investigation as the search for blood biomarkers in AD, in particular at the prodromal stage, remains a priority and a challenge.

• Alzheimer’s disease
• Platelet
• Biomarker
• Amyloid precursor protein
• Aβ amyloid
• β-amyloid precursor protein cleaving enzyme
• Secretase
• Protease-nexin 2

• alzheimers disease
• amyloid
• amyloid precursor protein
• intracellular trafficking
• secretases
• amyloid β
• er retrieval/retention
• γ-secretase
• rer1

• Adaptor Proteins, Vesicular Transport
• Alzheimer Disease/enzymology
• Alzheimer Disease/genetics
• Alzheimer Disease/metabolism
• Amyloid Precursor Protein Secretases/genetics
• Amyloid Precursor Protein Secretases/metabolism
• Amyloid beta-Peptides/genetics
• Amyloid beta-Peptides/metabolism
• Amyloid beta-Protein Precursor/genetics
• Amyloid beta-Protein Precursor/metabolism
• Endoplasmic Reticulum/genetics
• Endoplasmic Reticulum/metabolism
• HEK293 Cells
• Humans
• Membrane Glycoproteins/genetics
• Membrane Glycoproteins/metabolism
• Protein Transport

• P01 AG020206 NIA NIH HHS
• R01 AG033138 NIA NIH HHS
• AG020206 NIA NIH HHS
• AG033138 NIA NIH HHS

• app
• nae1
• alzheimer's disease
• parkinson's disease
• neurodegeneration
• proteasome
• neurogenesis
• ubiquitination
• neddylation
• differentiation

• Alzheimer Disease/genetics
• Alzheimer Disease/metabolism
• Alzheimer Disease/physiopathology
• Amyloid beta-Protein Precursor/metabolism
• Animals
• Cullin Proteins/metabolism
• DNA-Binding Proteins/metabolism
• Humans
• NEDD8 Protein
• Proteasome Endopeptidase Complex/metabolism
• Transcription Factors/metabolism
• Ubiquitin-Activating Enzymes/metabolism
• Ubiquitination
• Ubiquitins/metabolism

• R01 AG034980 NIA NIH HHS

Twenty-three years ago, numb was identified as a critical regulator in Drosophila sensory organ precursor cell asymmetric divisions. Beyond the recently recognized role in carcinogenesis, Numb seems to be important in Alzheimer’s disease. This assertion comes from the involvement in various processes such as synapse morphogenesis, amyloid precursor protein trafficking, notch signaling, and neurogenesis. The purpose of the present mini-review is to provide the current picture of Numb’s participation in mechanisms underlying Alzheimer’s disease pathogenesis and emphasize potential aspects for future research.

• Alzheimer’s disease
• neurogenesis
• notch signaling
• numb

• Alzheimer Disease/genetics
• Alzheimer Disease/pathology
• Amyloid beta-Protein Precursor/genetics
• Amyloid beta-Protein Precursor/therapeutic use
• Animals
• Axons/metabolism
• Axons/pathology
• Cells, Cultured
• Gene Expression Regulation, Developmental
• Gene Knockdown Techniques
• Humans
• Motor Neurons/metabolism
• Motor Neurons/pathology
• Mutation
• Phenotype
• Zebrafish/embryology
• Zebrafish/genetics

Amyloid-β-protein (Aβ), the key component of senile plaques in Alzheimer's disease (AD) brain, is produced from amyloid precursor protein (APP) by cleavage of β-secretase and then γ-secretase. APP adaptor proteins with phosphotyrosine-binding (PTB) domains, including Dab (gene: DAB) and Numb (gene: NUMB), can bind to and interact with the conserved YENPTY-motif in the APP C-terminus. Here we describe, for the first time, the effects of RNAi knock-down of Dab and Numb expression on APP processing and Aβ production. RNAi knock-down of Dab and Numb in H4 human neuroglioma cells stably transfected to express either FL-APP (H4-FL-APP cells) or APP-C99 (H4-APP-C99 cells) increased levels of APP-C-terminal fragments (APP-CTFs) and lowered Aβ levels in both cell lines by inhibiting γ-secretase cleavage of APP. Finally, RNAi knock-down of APP also reduced levels of Numb in H4-APP cells. These findings suggest that pharmacologically blocking interaction of APP with Dab and Numb may provide novel therapeutic strategies of AD. The notion of attenuating γ-secretase cleavage of APP via the APP adaptor proteins, Dab and Numb, is particularly attractive with regard to therapeutic potential, given that side effects of γ-secretase inhibition owing to impaired proteolysis of other γ-secretase substrates, e.g. Notch, might be avoided.

HD amino acid duplex has been found in the active center of many different enzymes. The dyad plays remarkably different roles in their catalytic processes that usually involve metal coordination. An HD motif is positioned directly on the amyloid beta fragment (Aβ) and on the carboxy-terminal region of the extracellular domain (CAED) of the human amyloid precursor protein (APP) and a taxonomically well defined group of APP orthologues (APPOs). In human Aβ HD is part of a presumed, RGD-like integrin-binding motif RHD; however, neither RHD nor RXD demonstrates reasonable conservation in APPOs. The sequences of CAEDs and the position of the HD are not particularly conserved either, yet we show with a novel statistical method using evolutionary modeling that the presence of HD on CAEDs cannot be the result of neutral evolutionary forces (p<0.0001). The motif is positively selected along the evolutionary process in the majority of APPOs, despite the fact that HD motif is underrepresented in the proteomes of all species of the animal kingdom. Position migration can be explained by high probability occurrence of multiple copies of HD on intermediate sequences, from which only one is kept by selective evolutionary forces, in a similar way as in the case of the “transcription binding site turnover.” CAED of all APP orthologues and homologues are predicted to bind metal ions including Amyloid-like protein 1 (APLP1) and Amyloid-like protein 2 (APLP2). Our results suggest that HDs on the CAEDs are most probably key components of metal-binding domains, which facilitate and/or regulate inter- or intra-molecular interactions in a metal ion-dependent or metal ion concentration-dependent manner. The involvement of naturally occurring mutations of HD (Tottori (D7N) and English (H6R) mutations) in early onset Alzheimer's disease gives additional support to our finding that HD has an evolutionary preserved function on APPOs.

HD amino acid duplex can be found in the active center of different metallo-enzymes. An HD motif is positioned directly on the amyloid beta (Aβ) fragment and on the carboxy-terminal region of the extracellular domain of the human amyloid precursor protein (APP) and a taxonomically well defined group of APP orthologues (APPOs). The conservation of the HD dyad is not position specific and it cannot be seen in a multiple alignment. Yet we show with a novel statistical method using evolutionary modeling that HD motif is positively selected by evolution on APPOs, despite the fact that HD dyad is underrepresented in the proteomes of all species of the animal kingdom. CAED of all APP orthologues and homologues are predicted to bind metal ions including Amyloid-like protein 1 (APLP1) and Amyloid-like protein 2 (APLP2). Our results suggest that HDs on the APPOs are most probably key components of metal-binding domains, which facilitate and/or regulate inter- or intra-molecular interactions in a metal ion-dependent or metal ion concentration-dependent manner. The involvement of naturally occurring mutations of HD (Tottori (D7N) and English (H6R)) in early onset Alzheimer's disease gives additional support to our finding that HD has an evolutionary preserved function on APPOs.

• aicd
• amyloid precursor protein
• fe65
• hirano body
• actin filaments
• alzheimer's disease
• neurodegenerative disease
• apoptosis

• Amyloid beta-Protein Precursor/metabolism
• Amyloid beta-Protein Precursor/physiology
• Apoptosis Regulatory Proteins/metabolism
• Apoptosis Regulatory Proteins/physiology
• Cell Line, Tumor
• Cytidine Deaminase/metabolism
• Cytidine Deaminase/physiology
• Down-Regulation/physiology
• HEK293 Cells
• Humans
• Inclusion Bodies/metabolism
• Nerve Tissue Proteins/metabolism
• Nerve Tissue Proteins/physiology
• Nuclear Proteins/metabolism
• Nuclear Proteins/physiology
• Protein Binding/physiology
• Transcriptional Activation/physiology

• R01 NS046451 NINDS NIH HHS
• R01 NS046451-01A2 NINDS NIH HHS
• 1R01-NS04645101 NINDS NIH HHS

• app
• aplp2
• fe65
• fe65l1
• nmda
• cortical neurons

• Amyloid beta-Peptides/metabolism
• Amyloid beta-Protein Precursor/metabolism
• Animals
• Axonal Transport/physiology
• Blotting, Western
• Calpain/pharmacology
• Cells, Cultured
• Electrophoresis, Polyacrylamide Gel
• Glycosylation
• Mice
• Mice, Inbred ICR
• Mice, Knockout
• Molecular Weight
• Nerve Tissue Proteins/genetics
• Nerve Tissue Proteins/physiology
• Neurons/metabolism
• Nuclear Proteins/genetics
• Nuclear Proteins/physiology
• Peptide Fragments/metabolism
• Phosphorylation
• Polysaccharides/chemistry
• Proteasome Endopeptidase Complex/drug effects
• Protein Processing, Post-Translational
• Receptors, N-Methyl-D-Aspartate/drug effects
• Receptors, N-Methyl-D-Aspartate/physiology
• Reverse Transcriptase Polymerase Chain Reaction

• R01 AG015903 NIA NIH HHS
• R01 AG015903-08 NIA NIH HHS
• AG15903 NIA NIH HHS

The amyloid precursor protein (APP) plays a central role in the pathophysiology of Alzheimer's disease in large part due to the sequential proteolytic cleavages that result in the generation of β-amyloid peptides (Aβ). Not surprisingly, the biological properties of APP have also been the subject of great interest and intense investigations. Since our 2006 review, the body of literature on APP continues to expand, thereby offering further insights into the biochemical, cellular and functional properties of this interesting molecule. Sophisticated mouse models have been created to allow in vivo examination of cell type-specific functions of APP together with the many functional domains. This review provides an overview and update on our current understanding of the pathobiology of APP.

Processing of Aβ-precursor protein (APP) plays an important role in Alzheimer's Disease (AD) pathogenesis. Thr residue at amino acid 668 of the APP intracellular domain (AID) is highly conserved. When phosphorylated, this residue generates a binding site for Pin1. The interaction of APP with Pin1 has been involved in AD pathogenesis.

To dissect the functions of this sequence in vivo, we created an APP knock-in allele, in which Thr⁶⁶⁸ is replaced by an Ala (T⁶⁶⁸A). Doubly deficient APP/APP-like protein 2 (APLP2) mice present postnatal lethality and neuromuscular synapse defects. Previous work has shown that the APP intracellular domain is necessary for preventing early lethality and neuromuscular junctions (NMJ) defects. Crossing the T⁶⁶⁸A allele into the APLP2 knockout background showed that mutation of Thr⁶⁶⁸ does not cause a defective phenotype. Notably, the T⁶⁶⁸A mutant APP is able to bind Mint1.

Our results argue against an important role of the Thr⁶⁶⁸ residue in the essential function of APP in developmental regulation. Furthermore, they indicate that phosphorylation at this residue is not functionally involved in those APP-mediated functions that prevent (NMJ) defects and early lethality in APLP2 null mice.

An important pathological feature of Alzheimer's disease (AD) is the presence of extracellular senile plaques in the brain. Senile plaques are composed of aggregations of small peptides called β-amyloid (Aβ). Multiple lines of evidence demonstrate that overproduction/aggregation of Aβ in the brain is a primary cause of AD and inhibition of Aβ generation has become a hot topic in AD research. Aβ is generated from β-amyloid precursor protein (APP) through sequential cleavages first by β-secretase and then by γ-secretase complex. Alternatively, APP can be cleaved by α-secretase within the Aβ domain to release soluble APPα and preclude Aβ generation. Cleavage of APP by caspases may also contribute to AD pathologies. Therefore, understanding the metabolism/processing of APP is crucial for AD therapeutics. Here we review current knowledge of APP processing regulation as well as the patho/physiological functions of APP and its metabolites.

• Amyloid/metabolism
• Amyloid beta-Peptides/metabolism
• Amyloid beta-Protein Precursor/genetics
• Amyloid beta-Protein Precursor/metabolism
• Animals
• Binding Sites/genetics
• Brain/metabolism
• Brain/pathology
• Cells, Cultured
• Gene Knock-In Techniques
• Immunoblotting
• Mice
• Mice, Inbred C57BL
• Mutation
• Neurons/metabolism
• Neurons/pathology
• Peptide Fragments/metabolism
• Reverse Transcriptase Polymerase Chain Reaction
• Synaptosomes/metabolism
• Tyrosine/genetics
• Tyrosine/metabolism

• R01AG033007 NIA NIH HHS
• R01 AG033007-02 NIA NIH HHS
• R01 AG033007-04 NIA NIH HHS
• T32 GM007288 NIGMS NIH HHS
• R01 AG033007-03S1 NIA NIH HHS
• T32 GM007491 NIGMS NIH HHS
• R01 AG033007 NIA NIH HHS
• R01 AG033007-03 NIA NIH HHS
• R01 AG033007-01A1 NIA NIH HHS

Alzheimer's disease (AD) is a neurodegenerative disorder primarily characterized by the deposition of β-amyloid plaques in the brain. Plaques are composed of the amyloid-β peptide derived from cleavage of the amyloid precursor protein (APP). Mutations in APP lead to the development of Familial Alzheimer's Disease (FAD), however, the normal function of this protein has proven elusive. The organism Caenorhabditis elegans is an attractive model as the amyloid precursor-like protein (APL-1) is the single ortholog of APP, and loss of apl-1 leads to a severe molting defect and early larval lethality.

We report here that lethality and molting can be rescued by full length APL-1, C-terminal mutations as well as a C-terminal truncation, suggesting that the extracellular region of the protein is essential for viability. RNAi knock-down of apl-1 followed by drug testing on the acetylcholinesterase inhibitor aldicarb showed that loss of apl-1 leads to aldicarb hypersensitivity, indicating a defect in synaptic function. The aldicarb hypersensitivity can be rescued by full length APL-1 in a dose dependent fashion. At the cellular level, kinesins UNC-104/KIF-1A and UNC-116/kinesin-1 are positive regulators of APL-1 expression in the neurons. Knock-down of the small GTPase rab-5 also leads to a dramatic decrease in the amount of apl-1 expression in neurons, suggesting that trafficking from the plasma membrane to the early endosome is important for apl-1 function. Loss of function of a different small GTPase, UNC-108, on the contrary, leads to the retention of APL-1 in the cell body.

Our results reveal novel insights into the intracellular trafficking of APL-1 and we report a functional role for APL-1 in synaptic transmission.

• Alzheimer Disease/genetics
• Alzheimer Disease/metabolism
• Amino Acid Motifs
• Animals
• Caenorhabditis elegans/chemistry
• Caenorhabditis elegans/genetics
• Caenorhabditis elegans/growth & development
• Caenorhabditis elegans/metabolism
• Caenorhabditis elegans Proteins/chemistry
• Caenorhabditis elegans Proteins/genetics
• Caenorhabditis elegans Proteins/metabolism
• Cell Membrane/chemistry
• Cell Membrane/genetics
• Cell Membrane/metabolism
• Disease Models, Animal
• Endosomes/chemistry
• Endosomes/genetics
• Endosomes/metabolism
• Humans
• Membrane Proteins/chemistry
• Membrane Proteins/genetics
• Membrane Proteins/metabolism
• Molting
• Monomeric GTP-Binding Proteins/genetics
• Monomeric GTP-Binding Proteins/metabolism
• Neurons/metabolism
• Protein Transport
• Synapses/chemistry
• Synapses/genetics
• Synapses/metabolism
• Synaptic Transmission

• R01 AG027498 NIA NIH HHS
• AG033467 NIA NIH HHS
• R01 AG033467 NIA NIH HHS
• AG027498 NIA NIH HHS
• AG032051 NIA NIH HHS
• R01 AG032051 NIA NIH HHS