Small, S.A. et al. Model-guided microarray implicates the retromer complex in Alzheimer's disease. Ann. Neurol. 58, 909-919
ABSTRACT Although, in principle, gene expression profiling is well suited to isolate pathogenic molecules associated with Alzheimer's disease (AD), techniques such as microarray present unique analytic challenges when applied to disorders of the brain. Here, we addressed these challenges by first constructing a spatiotemporal model, predicting a priori how a molecule underlying AD should behave anatomically and over time. Then, guided by the model, we generated gene expression profiles of the entorhinal cortex and the dentate gyrus, harvested from the brains of AD cases and controls covering a broad age span. Among many expression differences, the retromer trafficking molecule VPS35 best conformed to the spatiotemporal model of AD. Western blotting confirmed the abnormality, establishing that VPS35 levels are reduced in brain regions selectively vulnerable to AD. VPS35 is the core molecule of the retromer trafficking complex and further analysis revealed that VPS26, another member of the complex, is also downregulated in AD. Cell culture studies, using small interfering RNAs or expression vectors, showed that VPS35 regulates Abeta peptide levels, establishing the relevance of the retromer complex to AD. Reviewing our findings in the context of recent studies suggests how downregulation of the retromer complex in AD can regulate local levels of Abeta peptide.
- SourceAvailable from: Prasanna Sakha
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- "However, only GGA3 silencing had a strong effect on Aβ levels. There are controversial reports on how VPS35 silencing affects Aβ secretion; both increase  and decrease  of Aβ40 generation has been reported. These discrepancies may be explained by differences between cell lines or other experimental conditions, such as transfection and gene silencing efficiency, used in various studies. "
ABSTRACT: Amyloid-β precursor protein (APP) plays a central role in pathogenesis of Alzheimer's disease. APP has a short half-life and undergoes complex proteolytic processing that is highly responsive to various stimuli such as changes in cellular lipid or energy homeostasis. Cellular trafficking of APP is controlled by its large protein interactome, including dozens of cytosolic adaptor proteins, and also by interactions with lipids. Currently, cellular regulation of APP is mostly studied based on appearance of APP-derived proteolytic fragments to conditioned media and cellular extracts. Here, we have developed a novel live-cell assay system based on several indirect measures that reflect altered APP trafficking and processing in cells. Protein-fragment complementation assay technology for detection of APP-BACE1 protein-protein interaction forms the core of the new assay. In a multiplex form, the assay can measure four endpoints: total cellular APP level, total secreted sAPP level in media, APP-BACE1 interaction in cells and in exosomes released by the cells. Functional validation of the assay with pharmacological and genetic tools revealed distinct patterns of cellular fates of APP, with immediate mechanistic implications. This new technology will facilitate functional genomics studies of late-onset Alzheimer's disease, drug discovery efforts targeting APP and characterization of the physiological functions of APP and its proteolytic fragments.PLoS ONE 06/2014; 9(6):e98619. DOI:10.1371/journal.pone.0098619 · 3.23 Impact Factor
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- "The retromer complex (e.g., Vps35 and Vps26) is decreased in the postmortem hippocampus of AD patients . In Vps35 or Vps26 deficient animals, the major culprit of AD, β-amyloid (Aβ), is increased in the hippocampus [7,9]. In addition, Vps35 haploinsufficiency in Tg2576 mouse model of AD enhances Aβ-associated neuropathology . "
ABSTRACT: VPS35 (vacuolar protein sorting 35) is a major component of retromer that selectively promotes endosome-to-Golgi retrieval of transmembrane proteins. Dysfunction of retromer is a risk factor for the pathogenesis of Parkinson's disease (PD) and Alzheimer's disease (AD), both neuro-degeneration disorders. However, VPS35/retromer's function in retina or the contribution of Vps35-deficiency to retinal neuro-degenerative disorders has not been investigated. Here we provide evidence for a role of VPS35 in mouse retinal ganglion cell (RGC) survival and regeneration. VPS35 is selectively expressed in developing mouse RGCs. RGCs from young adult Vps35 heterozygotes (Vps35+/m) show degenerative-like features, such as dystrophic dendrites, reduced axon fibers, and increased TUNEL labeled RGCs. Additionally, gliosis in the optic nerve is transiently elevated in neonatal, but reduced in aged Vps35+/m mice. Optic nerve injury-induced gliosis is also attenuated in Vps35+/m mice. These results suggest that Vps35 is necessary for mouse RGC survival and regeneration, and Vps35-deficiency may contribute to the pathogenesis of retinal ganglion neuro-degeneration, a critical pathology leading to the blindness of many retinal degenerative disorders.Molecular Brain 02/2014; 7(1):10. DOI:10.1186/1756-6606-7-10 · 4.90 Impact Factor
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- "Similarly, downregulation of another retromer component VPS26 induces the accumulation of BACE1 in endosome . Coincidently, the levels of VPS35 and VPS26 are found to be downregulated in AD . "
ABSTRACT: The beta-amyloid (Abeta) peptide has been postulated to be a key determinant in the pathogenesis of Alzheimer's disease (AD). Abeta is produced through sequential cleavage of the beta-amyloid precursor protein (APP) by beta- and gamma-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 Abeta generation and accelerating disease pathogenesis. Herein, we review recent progress elucidating the regulation of intracellular trafficking of these essential protein components in AD.Molecular Neurodegeneration 01/2014; 9(1):6. DOI:10.1186/1750-1326-9-6 · 6.56 Impact Factor