101
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Liu FL, Liu TY, Kung FL. FKBP12 regulates the localization and processing of amyloid precursor protein in human cell lines. J Biosci 2014; 39:85-95. [PMID: 24499793 DOI: 10.1007/s12038-013-9400-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
One of the pathological hallmarks of Alzheimer's disease is the presence of insoluble extracellular amyloid plaques. These plaques are mainly constituted of amyloid beta peptide (A beta), a proteolytic product of amyloid precursor protein (APP). APP processing also generates the APP intracellular domain (AICD). We have previously demonstrated that AICD interacts with FKBP12, a peptidyl-prolyl cis-trans isomerase (PPIase) ubiquitous in nerve systems. This interaction was interfered by FK506, a clinically used immunosuppressant that has recently been reported to be neuroprotective. To elucidate the roles of FKBP12 in the pathogenesis of Alzheimer's disease, the effect of FKBP12 overexpression on APP processing was evaluated. Our results revealed that APP processing was shifted towards the amyloidogenic pathway, accompanied by a change in the subcellular localization of APP, upon FKBP12 overexpression. This FKBP12-overexpression-induced effect was reverted by FK506. These findings support our hypothesis that FKBP12 may participate in the regulation of APP processing. FKBP12 overexpression may lead to the stabilization of a certain isomer (presumably the cis form) of the Thr668-Pro669 peptide bond in AICD, therefore change its affinity to flotillin-1 or other raft-associated proteins, and eventually change the localization pattern and cause a shift in the proteolytic processing of APP.
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Affiliation(s)
- Fan-Lun Liu
- School of Pharmacy, National Taiwan University, Taipei 10051, Taiwan, R.O.C
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102
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Zhou X, Yang C, Liu Y, Li P, Yang H, Dai J, Qu R, Yuan L. Lipid rafts participate in aberrant degradative autophagic-lysosomal pathway of amyloid-beta peptide in Alzheimer's disease. Neural Regen Res 2014; 9:92-100. [PMID: 25206748 PMCID: PMC4146310 DOI: 10.4103/1673-5374.125335] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/25/2013] [Indexed: 11/04/2022] Open
Abstract
Amyloid-beta peptide is the main component of amyloid plaques, which are found in Alzheimer's disease. The generation and deposition of amyloid-beta is one of the crucial factors for the onset and progression of Alzheimer's disease. Lipid rafts are glycolipid-rich liquid domains of the plasma membrane, where certain types of protein tend to aggregate and intercalate. Lipid rafts are involved in the generation of amyloid-beta oligomers and the formation of amyloid-beta peptides. In this paper, we review the mechanism by which lipid rafts disturb the aberrant degradative autophagic-lysosomal pathway of amyloid-beta, which plays an important role in the pathological process of Alzheimer's disease. Moreover, we describe this mechanism from the view of the Two-system Theory of fasciology and thus, suggest that lipid rafts may be a new target of Alzheimer's disease treatment.
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Affiliation(s)
- Xin Zhou
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guang-dong Province, China
| | - Chun Yang
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guang-dong Province, China
| | - Yufeng Liu
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guang-dong Province, China
| | - Peng Li
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guang-dong Province, China
| | - Huiying Yang
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guang-dong Province, China
| | - Jingxing Dai
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guang-dong Province, China
| | - Rongmei Qu
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guang-dong Province, China
| | - Lin Yuan
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guang-dong Province, China
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Nah J, Pyo JO, Jung S, Yoo SM, Kam TI, Chang J, Han J, Soo A An S, Onodera T, Jung YK. BECN1/Beclin 1 is recruited into lipid rafts by prion to activate autophagy in response to amyloid β 42. Autophagy 2014; 9:2009-21. [PMID: 24145555 DOI: 10.4161/auto.26118] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Prion protein (PRNP) has been implicated in various types of neurodegenerative diseases. Although much is known about prion diseases, the function of cellular PRNP remains cryptic. Here, we show that PRNP mediates amyloid β1–42 (Aβ42)-induced autophagy activation through its interaction with BECN1. Treatment with Aβ42 enhanced autophagy flux in neuronal cells. Aβ42-induced autophagy activation, however, was impaired in prnp-knockout primary cortical neurons and Prnp-knockdown or prnp-knockout neuronal cells. Immunoprecipitation assays revealed that PRNP interacted with BECN1 via the BCL2-binding domain of BECN1. This interaction promoted the subcellular localization of BECN1 into lipid rafts of the plasma membrane and enhanced activity of PtdIns3K (whose catalytic subunit is termed PIK3C3, mammalian ortholog of yeast VPS34) in lipid rafts by generating PtdIns3P in response to Aβ42. Further, the levels of lipid rafts that colocalized with BECN1, decreased in the brains of aged C57BL/6 mice, as did PRNP. These results suggested that PRNP interacts with BECN1 to recruit the PIK3C3 complex into lipid rafts and thus activates autophagy in response to Aβ42, defining a novel role of PRNP in the regulation of autophagy.
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104
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Specific antibody binding to the APP672-699 region shifts APP processing from α- to β-cleavage. Cell Death Dis 2014; 5:e1374. [PMID: 25118934 PMCID: PMC4454311 DOI: 10.1038/cddis.2014.336] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 07/02/2014] [Accepted: 07/09/2014] [Indexed: 12/13/2022]
Abstract
Alzheimer's disease (AD), a progressive neurodegenerative disorder that is the most common cause of dementia in the elderly, is characterized by the accumulation of amyloid-β (Aβ) plaques and neurofibrillary tangles, as well as a progressive loss of synapses and neurons in the brain. The major pertinacious component of amyloid plaques is Aβ, a variably sized peptide derived from the integral membrane protein amyloid precursor protein (APP). The Aβ region of APP locates partly within its ecto- and trans-membrane domains. APP is cleaved by three proteases, designated as α-, β-, and γ-secretases. Processing by β- and γ-secretase cleaves the N- and C-terminal ends of the Aβ region, respectively, releasing Aβ, whereas α-secretase cleaves within the Aβ sequence, releasing soluble APPα (sAPPα). The γ-secretase cleaves at several adjacent sites to yield Aβ species containing 39-43 amino acid residues. Both α- and β-cleavage sites of human wild-type APP are located in APP672-699 region (ectodomain of β-C-terminal fragment, ED-β-CTF or ED-C99). Therefore, the amino acid residues within or near this region are definitely pivotal for human wild-type APP function and processing. Here, we report that one ED-C99-specific monoclonal antibody (mAbED-C99) blocks human wild-type APP endocytosis and shifts its processing from α- to β-cleavage, as evidenced by elevated accumulation of cell surface full-length APP and β-CTF together with reduced sAPPα and α-CTF levels. Moreover, mAbED-C99 enhances the interactions of APP with cholesterol. Consistently, intracerebroventricular injection of mAbED-C99 to human wild-type APP transgenic mice markedly increases membrane-associated β-CTF. All these findings suggest that APP672-699 region is critical for human wild-type APP processing and may provide new clues for the pathogenesis of sporadic AD.
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Abstract
BACKGROUND The use of statin therapy in established Alzheimer's disease (AD) or vascular dementia (VaD) is a relatively unexplored area. In AD, β-amyloid protein (Aβ) is deposited in the form of extracellular plaques and previous studies have determined Aβ generation is cholesterol dependent. Hypercholesterolaemia has also been implicated in the pathogenesis of VaD. Due to the role of statins in cholesterol reduction, it is biologically plausible they may be efficacious in the treatment of AD and VaD. OBJECTIVES To assess the clinical efficacy and safety of statins in the treatment of AD and VaD. To evaluate if the efficacy of statins in the treatment of AD and VaD depends on cholesterol level, ApoE genotype or cognitive level. SEARCH METHODS We searched ALOIS, the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group, The Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL and LILACS, as well as many trials registries and grey literature sources (20 January 2014). SELECTION CRITERIA Double-blind, randomised controlled trials of statins given for at least six months in people with a diagnosis of dementia. DATA COLLECTION AND ANALYSIS Two independent authors extracted and assessed data against the inclusion criteria. We pooled data where appropriate and entered them into a meta-analysis. We used standard methodological procedures expected by The Cochrane Collaboration. MAIN RESULTS We identified four studies (1154 participants, age range 50 to 90 years). All participants had a diagnosis of probable or possible AD according to standard criteria and most participants were established on a cholinesterase inhibitor. The primary outcome in all studies was change in Alzheimer's Disease Assessment Scale - cognitive subscale (ADAS-Cog) from baseline. When we pooled data, there was no significant benefit from statin (mean difference -0.26, 95% confidence interval (CI) -1.05 to 0.52, P value = 0.51). All studies provided change in Mini Mental State Examination (MMSE) from baseline. There was no significant benefit from statins in MMSE when we pooled the data (mean difference -0.32, 95% CI -0.71 to 0.06, P value = 0.10). Three studies reported treatment-related adverse effects. When we pooled data, there was no significant difference between statins and placebo (odds ratio 1.09, 95% CI 0.58 to 2.06, P value = 0.78). There was no significant difference in behaviour, global function or activities of daily living in the statin and placebo groups. We assessed risk of bias as low for all studies. We found no studies assessing role of statins in treatment of VaD. AUTHORS' CONCLUSIONS Analyses from the studies available, including two large randomised controlled trials, indicate that statins have no benefit on the primary outcome measures of ADAS-Cog or MMSE.
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Affiliation(s)
- Bernadette McGuinness
- Belfast Health and Social Care TrustDepartment of Geriatric MedicineLisburn RoadBelfastCo AntrimUK
| | - David Craig
- Craigavon Area HospitalGeriatric MedicineCraigavonNorthern IrelandUK
| | - Roger Bullock
- Kingshill Research Centre, Victoria HospitalOkus RoadSwindonUKSN4 4HZ
| | - Reem Malouf
- University of OxfordNational Perinatal Epidemiology Unit (NPEU)Old Road CampusOxfordUKOX3 7LF
| | - Peter Passmore
- Queen's University BelfastCentre for Public HealthBlock B, ICSB, Grosvenor RoadBelfastNorthern IrelandUKBT12
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106
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Han J, Jung S, Jang J, Kam TI, Choi H, Kim BJ, Nah J, Jo DG, Nakagawa T, Nishimura M, Jung YK. OCIAD2 activates γ-secretase to enhance amyloid β production by interacting with nicastrin. Cell Mol Life Sci 2014; 71:2561-76. [PMID: 24270855 PMCID: PMC11113593 DOI: 10.1007/s00018-013-1515-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 10/31/2013] [Accepted: 11/07/2013] [Indexed: 02/06/2023]
Abstract
The gamma (γ)-secretase holoenzyme is composed of four core proteins and cleaves APP to generate amyloid beta (Aβ), a key molecule that causes major neurotoxicity during the early stage of Alzheimer's disease (AD). However, despite its important role in Aβ production, little is known about the regulation of γ-secretase. OCIAD2, a novel modulator of γ-secretase that stimulates Aβ production, and which was isolated from a genome-wide functional screen using cell-based assays and a cDNA library comprising 6,178 genes. Ectopic expression of OCIAD2 enhanced Aβ production, while reduction of OCIAD2 expression suppressed it. OCIAD2 expression facilitated the formation of an active γ-secretase complex and enhanced subcellular localization of the enzyme components to lipid rafts. OCIAD2 interacted with nicastrin to stimulate γ-secretase activity. OCIAD2 also increased the interaction of nicastrin with C99 and stimulated APP processing via γ-secretase activation, but did not affect Notch processing. In addition, a cell-permeable Tat-OCIAD2 peptide that interfered with the interaction of OCIAD2 with nicastrin interrupted the γ-secretase-mediated AICD production. Finally, OCIAD2 expression was significantly elevated in the brain of AD patients and PDAPP mice. This study identifies OCIAD2 as a selective activator of γ-secretase to increase Aβ generation.
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Affiliation(s)
- Jonghee Han
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
| | - Sunmin Jung
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
| | - Jiyeon Jang
- School of Pharmacy, Sungkyunkwan University, Suwon, Korea
| | - Tae-In Kam
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
| | - Hyunwoo Choi
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
| | - Byung-Ju Kim
- Department of Cell Biology, Albert Einstein College of Medicine, New York City, 10461 NY USA
| | - Jihoon Nah
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
| | - Dong-Gyu Jo
- School of Pharmacy, Sungkyunkwan University, Suwon, Korea
| | - Toshiyuki Nakagawa
- Department of Neurobiology, Gifu University Graduate School of Medicine, Gifu, Japan
| | - Masaki Nishimura
- Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Shiga Japan
| | - Yong-Keun Jung
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
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107
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High resolution imaging study of interactions between the 37 kDa/67 kDa laminin receptor and APP, beta-secretase and gamma-secretase in Alzheimer's disease. PLoS One 2014; 9:e100373. [PMID: 24972054 PMCID: PMC4074076 DOI: 10.1371/journal.pone.0100373] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 05/27/2014] [Indexed: 12/13/2022] Open
Abstract
Alzheimer's disease (AD) is the most prevalent form of dementia affecting the elderly. Neurodegeneration is caused by the amyloid beta (Aβ) peptide which is generated from the sequential proteolytic cleavage of the Amyloid Precursor Protein (APP) by the β– and γ- secretases. Previous reports revealed that the 37 kDa/67 kDa laminin receptor (LRP/LR) is involved in APP processing, however, the exact mechanism by which this occurs remains largely unclear. This study sought to assess whether LRP/LR interacted with APP, β- or γ-secretase. Detailed confocal microscopy revealed that LRP/LR showed a strong co-localisation with APP, β- and γ-secretase, respectively, at various sub-cellular locations. Superresolution Structured Illumination Microscopy (SR-SIM) showed that interactions were unlikely between LRP/LR and APP and β-secretase, respectively, while there was strong co-localisation between LRP/LR and γ-secretase at this 80 nm resolution. FRET was further employed to assess the possibility of protein-protein interactions and only an interaction between LRP/LR and γ-secretase was found. FLAG co-immunoprecipitation confirmed these findings as LRP/LR co-immunoprecipitated with γ-secretase, but failed to do so with APP. These findings indicate that LRP/LR exerts its influence on Aβ shedding via a direct interaction with the γ-secretase and possibly an indirect interaction with the β-secretase.
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108
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Anti-LRP/LR specific antibodies and shRNAs impede amyloid beta shedding in Alzheimer's disease. Sci Rep 2014; 3:2699. [PMID: 24048412 PMCID: PMC3776966 DOI: 10.1038/srep02699] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 09/02/2013] [Indexed: 01/14/2023] Open
Abstract
Alzheimer's disease (AD) is the most prevalent form of dementia. The amyloid beta (Aβ) peptide is the predominant candidate aetiological agent and is generated through the sequential proteolytic cleavage of the Amyloid Precursor Protein (APP) by beta (β) and gamma (γ) secretases. Since the cellular prion protein (PrPc) has been shown to regulate Aβ shedding, we investigated whether the cellular receptor for PrPc, namely the 37 kDa/67 kDa Laminin Receptor (LRP/LR) played a role in Aβ shedding. Here we show that LRP/LR co-localises with the AD relevant proteins APP, β- and γ-secretase, respectively. Antibody blockage and shRNA knock-down of LRP/LR reduces Aβ shedding, due to impediment of β-secretase activity, rather than alteration of APP, β- and γ-secretase levels. These findings indicate that LRP/LR contributes to Aβ shedding and recommend anti-LRP/LR specific antibodies and shRNAs as novel therapeutic tools for AD treatment.
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109
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Schwarzer R, Levental I, Gramatica A, Scolari S, Buschmann V, Veit M, Herrmann A. The cholesterol-binding motif of the HIV-1 glycoprotein gp41 regulates lateral sorting and oligomerization. Cell Microbiol 2014; 16:1565-81. [PMID: 24844300 DOI: 10.1111/cmi.12314] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/24/2014] [Accepted: 05/13/2014] [Indexed: 12/12/2022]
Abstract
Enveloped viruses often use membrane lipid rafts to assemble and bud, augment infection and spread efficiently. However, the molecular bases and functional consequences of the partitioning of viral glycoproteins into microdomains remain intriguing questions in virus biology. Here, we measured Foerster resonance energy transfer by fluorescence lifetime imaging microscopy (FLIM-FRET) to study the role of distinct membrane proximal regions of the human immunodeficiency virus glycoprotein gp41 for lipid raft partitioning in living Chinese hamster ovary cells (CHO-K1). Gp41 was labelled with a fluorescent protein at the exoplasmic face of the membrane, preventing any interference of the fluorophore with the proposed role of the transmembrane and cytoplasmic domains in lateral organization of gp41. Raft localization was deduced from interaction with an established raft marker, a fluorescently tagged glycophosphatidylinositol anchor and the cholesterol recognition amino acid consensus (CRAC) was identified as the crucial lateral sorting determinant in CHO-K1 cells. Interestingly, the raft association of gp41 indicates a substantial cell-to-cell heterogeneity of the plasma membrane microdomains. In complementary fluorescence polarization microscopy, a distinct CRAC requirement was found for the oligomerization of the gp41 variants. Our data provide further insight into the molecular basis and biological implications of the cholesterol dependent lateral sorting of viral glycoproteins for virus assembly at cellular membranes.
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Affiliation(s)
- Roland Schwarzer
- Department of Biology, Molecular Biophysics, Humboldt University, 10115, Berlin, Germany
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110
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Wong BX, Hung YH, Bush AI, Duce JA. Metals and cholesterol: two sides of the same coin in Alzheimer's disease pathology. Front Aging Neurosci 2014; 6:91. [PMID: 24860500 PMCID: PMC4030154 DOI: 10.3389/fnagi.2014.00091] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/28/2014] [Indexed: 11/13/2022] Open
Abstract
Alzheimer's disease (AD) is a multifactorial neurodegenerative disease. It begins years prior to the onset of clinical symptoms, such as memory loss and cognitive decline. Pathological hallmarks of AD include the accumulation of β-amyloid in plaques and hyperphosphorylated tau in neurofibrillary tangles. Copper, iron, and zinc are abnormally accumulated and distributed in the aging brain. These metal ions can adversely contribute to the progression of AD. Dysregulation of cholesterol metabolism has also been implicated in the development of AD pathology. To date, large bodies of research have been carried out independently to elucidate the role of metals or cholesterol on AD pathology. Interestingly, metals and cholesterol affect parallel molecular and biochemical pathways involved in AD pathology. The possible links between metal dyshomeostasis and altered brain cholesterol metabolism in AD are reviewed.
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Affiliation(s)
- Bruce X Wong
- Oxidation Biology Unit, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne Parkville, VIC, Australia
| | - Ya Hui Hung
- Oxidation Biology Unit, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne Parkville, VIC, Australia
| | - Ashley I Bush
- Oxidation Biology Unit, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne Parkville, VIC, Australia
| | - James A Duce
- Oxidation Biology Unit, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne Parkville, VIC, Australia ; School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds Leeds, North Yorkshire, UK
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111
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Sotelo P, Farfán P, Benitez ML, Bu G, Marzolo MP. Sorting nexin 17 regulates ApoER2 recycling and reelin signaling. PLoS One 2014; 9:e93672. [PMID: 24705369 PMCID: PMC3976305 DOI: 10.1371/journal.pone.0093672] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 03/10/2014] [Indexed: 11/30/2022] Open
Abstract
ApoER2 is a member of the low density-lipoprotein receptor (LDL-R) family. As a receptor for reelin, ApoER2 participates in neuronal migration during development as well as synaptic plasticity and survival in the adult brain. A previous yeast two-hybrid screen showed that ApoER2 is a binding partner of sorting nexin 17 (SNX17) - a cytosolic adaptor protein that regulates the trafficking of several membrane proteins in the endosomal pathway, including LRP1, P-selectin and integrins. However, no further studies have been performed to investigate the role of SNX17 in ApoER2 trafficking and function. In this study, we present evidence based on GST pull-down and inmunoprecipitation assays that the cytoplasmic NPxY endocytosis motif of ApoER2 interacts with the FERM domain of SNX17. SNX17 stimulates ApoER2 recycling in different cell lines including neurons without affecting its endocytic rate and also facilitates the transport of ApoER2 from the early endosomes to the recycling endosomes. The reduction of SNX17 was associated with accumulation of an ApoER2 carboxy-terminal fragment (CTF). In addition, in SNX17 knockdown cells, constitutive ApoER2 degradation was not modified, whereas reelin-induced ApoER2 degradation was increased, implying that SNX17 is a regulator of the receptor's half-life. Finally, in SNX17 silenced hippocampal and cortical neurons, we underscored a positive role of this endosomal protein in the development of the dendritic tree and reelin signaling. Overall, these results establish the role of SNX17 in ApoER2 trafficking and function and aid in identifying new links between endocytic trafficking and receptor signaling.
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Affiliation(s)
- Pablo Sotelo
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Millenium Nucleus for Renerative Biology (MINREB), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pamela Farfán
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Millenium Nucleus for Renerative Biology (MINREB), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - María Luisa Benitez
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Millenium Nucleus for Renerative Biology (MINREB), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Guojun Bu
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America
| | - María-Paz Marzolo
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Millenium Nucleus for Renerative Biology (MINREB), Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail:
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112
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Cellular membrane fluidity in amyloid precursor protein processing. Mol Neurobiol 2014; 50:119-29. [PMID: 24553856 DOI: 10.1007/s12035-014-8652-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 01/23/2014] [Indexed: 12/20/2022]
Abstract
The senile plaque is a pathologic hallmark of Alzheimer's disease (AD). Amyloid-β peptide (Aβ), the main constituent of senile plaques, is neurotoxic especially in its oligomeric form. Aβ is derived from the sequential cleavage of amyloid precursor protein (APP) by β- and γ-secretases in the amyloidogenic pathway. Alternatively, APP can be cleaved by α-secretases within the Aβ domain to produce neurotrophic and neuroprotective α-secretase-cleaved soluble APP (sAPPα) in the nonamyloidogenic pathway. Since APP and α-, β-, and γ-secretases are membrane proteins, APP processing should be highly dependent on the membrane composition and the biophysical properties of cellular membrane. In this review, we discuss the role of the biophysical properties of cellular membrane in APP processing, especially the effects of phospholipases A(2) (PLA(2)s), fatty acids, cholesterol, and Aβ on membrane fluidity in relation to their effects on APP processing.
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113
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García-Ayllón MS, Campanari ML, Montenegro MF, Cuchillo-Ibáñez I, Belbin O, Lleó A, Tsim K, Vidal CJ, Sáez-Valero J. Presenilin-1 influences processing of the acetylcholinesterase membrane anchor PRiMA. Neurobiol Aging 2014; 35:1526-36. [PMID: 24612677 DOI: 10.1016/j.neurobiolaging.2014.01.147] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Revised: 01/26/2014] [Accepted: 01/30/2014] [Indexed: 01/13/2023]
Abstract
Presenilin-1 (PS1) is the catalytic component of the γ-secretase complex. In this study, we explore if PS1 participates in the processing of the cholinergic acetylcholinesterase (AChE). The major AChE variant expressed in the brain is a tetramer (G(4)) bound to a proline-rich membrane anchor (PRiMA). Overexpression of the transmembrane PRiMA protein in Chinese hamster ovary cells expressing AChE and treated with the γ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester have enabled us to study whether, through its γ-secretase activity, PS1 participates in the processing of PRiMA-linked AChE. γ-Secretase inhibition led to a notable increase in the level of PRiMA-linked AChE, suggesting that γ-secretase is involved in the cleavage of PRiMA. We demonstrate that cleavage of PRiMA by γ-secretase results in a C-terminal PRiMA fragment. Immunofluorescence labeling allowed us to identify this PRiMA fragment in the nucleus. Moreover, we have determined changes in the proportion of the raft-residing AChE-PRiMA in a PS1 conditional knockout mouse. Our results are of interest as both enzymes have therapeutic relevance for Alzheimer's disease.
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Affiliation(s)
- María-Salud García-Ayllón
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas (CSIC), Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain; Unidad de Investigación, Hospital General Universitario de Elche, Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunitat Valenciana (FISABIO), Elche, Spain
| | - María-Letizia Campanari
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas (CSIC), Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - María-Fernanda Montenegro
- Departamento de Bioquímica y Biología Molecular-A, Universidad de Murcia, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Inmaculada Cuchillo-Ibáñez
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas (CSIC), Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Olivia Belbin
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain; Memory Unit, Neurology Department, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Alberto Lleó
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain; Memory Unit, Neurology Department, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Karl Tsim
- Division of Life Science and Center for Chinese Medicine, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Cecilio J Vidal
- Departamento de Bioquímica y Biología Molecular-A, Universidad de Murcia, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Javier Sáez-Valero
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas (CSIC), Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.
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Hu J, Popp R, Frömel T, Ehling M, Awwad K, Adams RH, Hammes HP, Fleming I. Müller glia cells regulate Notch signaling and retinal angiogenesis via the generation of 19,20-dihydroxydocosapentaenoic acid. ACTA ACUST UNITED AC 2014; 211:281-95. [PMID: 24446488 PMCID: PMC3920554 DOI: 10.1084/jem.20131494] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Cytochrome P450 (CYP) epoxygenases generate bioactive lipid epoxides which can be further metabolized to supposedly less active diols by the soluble epoxide hydrolase (sEH). As the role of epoxides and diols in angiogenesis is unclear, we compared retinal vasculature development in wild-type and sEH(-/-) mice. Deletion of the sEH significantly delayed angiogenesis, tip cell, and filopodia formation, a phenomenon associated with activation of the Notch signaling pathway. In the retina, sEH was localized in Müller glia cells, and Müller cell-specific sEH deletion reproduced the sEH(-/-) retinal phenotype. Lipid profiling revealed that sEH deletion decreased retinal and Müller cell levels of 19,20-dihydroxydocosapentaenoic acid (DHDP), a diol of docosahexenoic acid (DHA). 19,20-DHDP suppressed endothelial Notch signaling in vitro via inhibition of the γ-secretase and the redistribution of presenilin 1 from lipid rafts. Moreover, 19,20-DHDP, but not the parent epoxide, was able to rescue the defective angiogenesis in sEH(-/-) mice as well as in animals lacking the Fbxw7 ubiquitin ligase, which demonstrate strong basal activity of the Notch signaling cascade. These studies demonstrate that retinal angiogenesis is regulated by a novel form of neuroretina-vascular interaction involving the sEH-dependent generation of a diol of DHA in Müller cells.
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Affiliation(s)
- Jiong Hu
- Institute for Vascular Signaling, Centre for Molecular Medicine, Johann Wolfgang Goethe University and DZHK (German Centre for Cardiovascular Research) partner site Rhine-Main, 60590 Frankfurt, Germany
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115
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Groen AJ, Sancho-Andrés G, Breckels LM, Gatto L, Aniento F, Lilley KS. Identification of trans-golgi network proteins in Arabidopsis thaliana root tissue. J Proteome Res 2014; 13:763-76. [PMID: 24344820 PMCID: PMC3929368 DOI: 10.1021/pr4008464] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
![]()
Knowledge of protein
subcellular localization assists in the elucidation
of protein function and understanding of different biological mechanisms
that occur at discrete subcellular niches. Organelle-centric proteomics
enables localization of thousands of proteins simultaneously. Although
such techniques have successfully allowed organelle protein catalogues
to be achieved, they rely on the purification or significant enrichment
of the organelle of interest, which is not achievable for many organelles.
Incomplete separation of organelles leads to false discoveries, with
erroneous assignments. Proteomics methods that measure the distribution
patterns of specific organelle markers along density gradients are
able to assign proteins of unknown localization based on comigration
with known organelle markers, without the need for organelle purification.
These methods are greatly enhanced when coupled to sophisticated computational
tools. Here we apply and compare multiple approaches to establish
a high-confidence data set of Arabidopsis root tissue
trans-Golgi network (TGN) proteins. The method employed involves immunoisolations
of the TGN, coupled to probability-based organelle proteomics techniques.
Specifically, the technique known as LOPIT (localization of organelle
protein by isotope tagging), couples density centrifugation with quantitative
mass-spectometry-based proteomics using isobaric labeling and targeted
methods with semisupervised machine learning methods. We demonstrate
that while the immunoisolation method gives rise to a significant
data set, the approach is unable to distinguish cargo proteins and
persistent contaminants from full-time residents of the TGN. The LOPIT
approach, however, returns information about many subcellular niches
simultaneously and the steady-state location of proteins. Importantly,
therefore, it is able to dissect proteins present in more than one
organelle and cargo proteins en route to other cellular destinations
from proteins whose steady-state location favors the TGN. Using this
approach, we present a robust list of Arabidopsis TGN proteins.
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Affiliation(s)
- Arnoud J Groen
- Cambridge Centre for Proteomics, Cambridge Systems Biology Centre, Department of Biochemistry, University of Cambridge , 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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116
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Early onset Alzheimer's disease and oxidative stress. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2014; 2014:375968. [PMID: 24669286 PMCID: PMC3942075 DOI: 10.1155/2014/375968] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 11/18/2013] [Indexed: 01/30/2023]
Abstract
Alzheimer's disease (AD) is the most common cause of dementia in elderly adults. It is estimated that 10% of the world's population aged more than 60-65 years could currently be affected by AD, and that in the next 20 years, there could be more than 30 million people affected by this pathology. One of the great challenges in this regard is that AD is not just a scientific problem; it is associated with major psychosocial and ethical dilemmas and has a negative impact on national economies. The neurodegenerative process that occurs in AD involves a specific nervous cell dysfunction, which leads to neuronal death. Mutations in APP, PS1, and PS2 genes are causes for early onset AD. Several animal models have demonstrated that alterations in these proteins are able to induce oxidative damage, which in turn favors the development of AD. This paper provides a review of many, although not all, of the mutations present in patients with familial Alzheimer's disease and the association between some of these mutations with both oxidative damage and the development of the pathology.
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117
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Abstract
Ubiquitin-dependent proteolysis is a major mechanism that downregulates misfolded proteins or those that have finished a programmed task. In the last two decades, neddylation has emerged as a major regulatory pathway for ubiquitination. Central to the neddylation pathway is the amyloid precursor protein (APP)-binding protein APP-BP1, which together with Uba3, plays an analogous role to the ubiquitin-activating enzyme E1 in nedd8 activation. Activated nedd8 covalently modifies and activates a major class of ubiquitin ligases called Cullin-RING ligases (CRLs). New evidence suggests that neddylation also modifies Type-1 transmembrane receptors such as APP. Here we review the functions of neddylation and summarize evidence suggesting that dysfunction of neddylation is involved in Alzheimer's disease.
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Affiliation(s)
- Yuzhi Chen
- Department of Geriatrics and Department of Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
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118
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119
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Golde TE, Koo EH, Felsenstein KM, Osborne BA, Miele L. γ-Secretase inhibitors and modulators. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1828:2898-907. [PMID: 23791707 PMCID: PMC3857966 DOI: 10.1016/j.bbamem.2013.06.005] [Citation(s) in RCA: 210] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 06/04/2013] [Indexed: 12/11/2022]
Abstract
γ-Secretase is a fascinating, multi-subunit, intramembrane cleaving protease that is now being considered as a therapeutic target for a number of diseases. Potent, orally bioavailable γ-secretase inhibitors (GSIs) have been developed and tested in humans with Alzheimer's disease (AD) and cancer. Preclinical studies also suggest the therapeutic potential for GSIs in other disease conditions. However, due to inherent mechanism based-toxicity of non-selective inhibition of γ-secretase, clinical development of GSIs will require empirical testing with careful evaluation of benefit versus risk. In addition to GSIs, compounds referred to as γ-secretase modulators (GSMs) remain in development as AD therapeutics. GSMs do not inhibit γ-secretase, but modulate γ-secretase processivity and thereby shift the profile of the secreted amyloid β peptides (Aβ) peptides produced. Although GSMs are thought to have an inherently safe mechanism of action, their effects on substrates other than the amyloid β protein precursor (APP) have not been extensively investigated. Herein, we will review the current state of development of GSIs and GSMs and explore pertinent biological and pharmacological questions pertaining to the use of these agents for select indications. This article is part of a Special Issue entitled: Intramembrane Proteases.
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Affiliation(s)
- Todd E Golde
- Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610, USA.
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120
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Kim J, Yoon JH, Kim YS. HIV-1 Tat interacts with and regulates the localization and processing of amyloid precursor protein. PLoS One 2013; 8:e77972. [PMID: 24312169 PMCID: PMC3843664 DOI: 10.1371/journal.pone.0077972] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 09/07/2013] [Indexed: 12/22/2022] Open
Abstract
HIV-1 Tat protein plays various roles in virus proliferation and in the regulation of numerous host cell functions. Accumulating evidence suggests that HIV-1 Tat also plays an important role in HIV-associated neurocognitive disorders (HAND) by disrupting intracellular communication. Amyloid beta (Aβ) is generated from amyloid precursor protein (APP) and accumulates in the senile plaques of Alzheimer's disease patients. This study demonstrates that Tat interacts with APP both in vitro and in vivo, and increases the level of Aβ42 by recruiting APP into lipid rafts. Co-localization of Tat with APP in the cytosol was observed in U-87 MG cells that expressed high levels of Tat, and redistribution of APP into lipid rafts, a site of increased β- and γ-secretase activity, was demonstrated by discontinuous sucrose density gradient ultracentrifugation in the presence of Tat. Furthermore, Tat enhanced the cleavage of APP by β-secretase in vitro, resulting in 5.5-fold higher levels of Aβ42. This was consistent with increased levels of β-C-terminal fragment (β-CTF) and reduced levels of α-CTF. Moreover, stereotaxic injection of a lentiviral Tat expression construct into the hippocampus of APP/presenilin-1 (PS1) transgenic mice resulted in increased Tat-mediated production and processing of Aβ in vivo. Increased levels of Aβ42, as well as an increase in the number and size of Aβ plaques, were observed in the hippocampus following injection of Tat virus compared with mock virus. These results suggest that HIV-1 Tat may contribute to HAND by interacting with and modifying APP processing, thereby increasing Aβ production.
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Affiliation(s)
- Jiyoung Kim
- Indang Institute of Molecular Biology, Inje University, Jung-Gu, Seoul, Republic of Korea
| | - Jee-Hyun Yoon
- Department of Smart Foods and Drugs, Inje University, Jung-Gu, Seoul, Republic of Korea
| | - Yeon-Soo Kim
- Indang Institute of Molecular Biology, Inje University, Jung-Gu, Seoul, Republic of Korea
- Department of Smart Foods and Drugs, Inje University, Jung-Gu, Seoul, Republic of Korea
- * E-mail:
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Abstract
This article describes a procedure to prepare a raft-like intracellular membrane fraction enriched for the trans-Golgi network (TGN) and endosomal compartments. The initial step in this technique involves cell disruption by homogenization, followed by clearance of the plasma membrane, late endosomes, mitochondria and the endoplasmic reticulum by differential sedimentation. Carbonate treatment, sonication and sucrose density-gradient ultracentrifugation are subsequently used to isolate the target membranes. The isolated subcellular fraction contains less than 1% of the total cellular proteins, but it is highly enriched for syntaxin-6 and Rab11. Typically, 40-60% of the cellular pool of GM1 glycosphingolipid and 10-20% of the total cellular cholesterol cofractionate with this buoyant membrane fraction. Given the role of GM1 as a cell-surface receptor for the cholera toxin and that levels of both GM1 and cholesterol in the TGN-endosomal compartment are upregulated in some inherited diseases, this protocol can potentially be applied to the analysis of disease-associated changes to GM1-enriched intracellular membranes. The isolated membranes are very well separated from caveolin-rich domains of the plasma membrane, the TGN and recycling endosomes. The entire protocol can be completed in as little as 1 d.
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Affiliation(s)
- Mark G Waugh
- Institute for Liver and Digestive Health, University College London, Royal Free Campus, London, UK
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122
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Hoey SE, Buonocore F, Cox CJ, Hammond VJ, Perkinton MS, Williams RJ. AMPA receptor activation promotes non-amyloidogenic amyloid precursor protein processing and suppresses neuronal amyloid-β production. PLoS One 2013; 8:e78155. [PMID: 24205136 PMCID: PMC3813448 DOI: 10.1371/journal.pone.0078155] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 09/17/2013] [Indexed: 01/12/2023] Open
Abstract
Soluble oligomeric amyloid β peptide (Aβ) generated from processing of the amyloid precursor protein (APP) plays a central role in the pathogenesis of Alzheimer's Disease (AD) and through actions at glutamatergic synapses affects excitability and plasticity. The physiological control of APP processing is not fully understood but stimulation of synaptic NMDA receptors (NMDAR) can suppress Aβ levels through an ERK-dependent increase in α-secretase activity. AMPA-type glutamate receptors (AMPAR) couple to ERK phosphorylation independently of NMDAR activation raising the possibility that stimulation of AMPAR might similarly promote non-amyloidogenic APP processing. We have tested this hypothesis by investigating whether AMPAR directly regulate APP processing in cultured mouse cortical neurons, by analyzing APP C-terminal fragments (CTFs), soluble APP (sAPP), Aβ levels, and cleavage of an APP-GAL4 reporter protein. We report that direct stimulation of AMPAR increases non-amyloidogenic α-secretase-mediated APP processing and inhibits Aβ production. Processing was blocked by the matrix metalloproteinase inhibitor TAPI-1 but was only partially dependent on Ca2+ influx and ERK activity. AMPAR can therefore, be added to the repertoire of receptors that couple to non-amyloidogenic APP processing at glutamatergic synapses and thus pharmacological targeting of AMPAR could potentially influence the development and progression of Aβ pathology in AD.
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Affiliation(s)
- Sarah E. Hoey
- King's College London, Wolfson Centre for Age-Related Diseases, London, United Kingdom
| | - Federica Buonocore
- King's College London, Wolfson Centre for Age-Related Diseases, London, United Kingdom
| | - Carla J. Cox
- University of Bath, Department of Biology and Biochemistry, Bath, United Kingdom
| | - Victoria J. Hammond
- University of Bath, Department of Biology and Biochemistry, Bath, United Kingdom
| | - Michael S. Perkinton
- King's College London, Wolfson Centre for Age-Related Diseases, London, United Kingdom
| | - Robert J. Williams
- King's College London, Wolfson Centre for Age-Related Diseases, London, United Kingdom
- University of Bath, Department of Biology and Biochemistry, Bath, United Kingdom
- * E-mail:
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123
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Palmitoylation of amyloid precursor protein regulates amyloidogenic processing in lipid rafts. J Neurosci 2013; 33:11169-83. [PMID: 23825420 DOI: 10.1523/jneurosci.4704-12.2013] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Brains of patients affected by Alzheimer's disease (AD) contain large deposits of aggregated amyloid β-protein (Aβ). Only a small fraction of the amyloid precursor protein (APP) gives rise to Aβ. Here, we report that ∼10% of APP undergoes a post-translational lipid modification called palmitoylation. We identified the palmitoylation sites in APP at Cys¹⁸⁶ and Cys¹⁸⁷. Surprisingly, point mutations introduced into these cysteines caused nearly complete ER retention of APP. Thus, either APP palmitoylation or disulfide bridges involving these Cys residues appear to be required for ER exit of APP. In later compartments, palmitoylated APP (palAPP) was specifically enriched in lipid rafts. In vitro BACE1 cleavage assays using cell or mouse brain lipid rafts showed that APP palmitoylation enhanced BACE1-mediated processing of APP. Interestingly, we detected an age-dependent increase in endogenous mouse brain palAPP levels. Overexpression of selected DHHC palmitoyl acyltransferases increased palmitoylation of APP and doubled Aβ production, while two palmitoylation inhibitors reduced palAPP levels and APP processing. We have found previously that acyl-coenzyme A:cholesterol acyltransferase (ACAT) inhibition led to impaired APP processing. Here we demonstrate that pharmacological inhibition or genetic inactivation of ACAT decrease lipid raft palAPP levels by up to 76%, likely resulting in impaired APP processing. Together, our results indicate that APP palmitoylation enhances amyloidogenic processing by targeting APP to lipid rafts and enhancing its BACE1-mediated cleavage. Thus, inhibition of palAPP formation by ACAT or specific palmitoylation inhibitors would appear to be a valid strategy for prevention and/or treatment of AD.
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124
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Kang MS, Baek SH, Chun YS, Moore AZ, Landman N, Berman D, Yang HO, Morishima-Kawashima M, Osawa S, Funamoto S, Ihara Y, Di Paolo G, Park JH, Chung S, Kim TW. Modulation of lipid kinase PI4KIIα activity and lipid raft association of presenilin 1 underlies γ-secretase inhibition by ginsenoside (20S)-Rg3. J Biol Chem 2013; 288:20868-20882. [PMID: 23723072 PMCID: PMC3774358 DOI: 10.1074/jbc.m112.445734] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 05/20/2013] [Indexed: 01/09/2023] Open
Abstract
Amyloid β-peptide (Aβ) pathology is an invariant feature of Alzheimer disease, preceding any detectable clinical symptoms by more than a decade. To this end, we seek to identify agents that can reduce Aβ levels in the brain via novel mechanisms. We found that (20S)-Rg3, a triterpene natural compound known as ginsenoside, reduced Aβ levels in cultured primary neurons and in the brains of a mouse model of Alzheimer disease. The (20S)-Rg3 treatment induced a decrease in the association of presenilin 1 (PS1) fragments with lipid rafts where catalytic components of the γ-secretase complex are enriched. The Aβ-lowering activity of (20S)-Rg3 directly correlated with increased activity of phosphatidylinositol 4-kinase IIα (PI4KIIα), a lipid kinase that mediates the rate-limiting step in phosphatidylinositol 4,5-bisphosphate synthesis. PI4KIIα overexpression recapitulated the effects of (20S)-Rg3, whereas reduced expression of PI4KIIα abolished the Aβ-reducing activity of (20S)-Rg3 in neurons. Our results substantiate an important role for PI4KIIα and phosphoinositide modulation in γ-secretase activity and Aβ biogenesis.
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Affiliation(s)
- Min Suk Kang
- From the Department of Pathology and Cell Biology and Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, New York 10032
| | | | - Yoon Sun Chun
- Department of Physiology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea
| | - A Zenobia Moore
- From the Department of Pathology and Cell Biology and Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, New York 10032
| | - Natalie Landman
- From the Department of Pathology and Cell Biology and Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, New York 10032
| | - Diego Berman
- From the Department of Pathology and Cell Biology and Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, New York 10032
| | - Hyun Ok Yang
- Natural Products Research Center, Korea Institute of Science and Technology-Gangneung Institute, Gangneung, Gangwon-do 210-340, Korea
| | - Maho Morishima-Kawashima
- Department of Molecular Neuropathology, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Hokkaido 060-0808, Japan
| | - Satoko Osawa
- Department of Neuropathology, Faculty of Medicine, University of Tokyo, Tokyo 113-0033, Japan
| | - Satoru Funamoto
- Department of Neuropathology, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto 610-0394, Japan, and
| | - Yasuo Ihara
- Department of Neuropathology, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto 610-0394, Japan, and
| | - Gilbert Di Paolo
- From the Department of Pathology and Cell Biology and Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, New York 10032
| | - Jeong Hill Park
- Research Institute of Pharmaceutical Sciences, Seoul National University, College of Pharmacy, Seoul 151-742, Korea
| | - Sungkwon Chung
- Department of Physiology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea,.
| | - Tae-Wan Kim
- From the Department of Pathology and Cell Biology and Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, New York 10032,.
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125
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Urano Y, Ochiai S, Noguchi N. Suppression of amyloid‐β production by 24S‐hydroxycholesterol
via
inhibition of intracellular amyloid precursor protein trafficking. FASEB J 2013; 27:4305-15. [DOI: 10.1096/fj.13-231456] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Yasuomi Urano
- Department of Medical Life SystemsFaculty of Medical and Life SciencesDoshisha UniversityKyotoJapan
| | - Sachika Ochiai
- Department of Medical Life SystemsFaculty of Medical and Life SciencesDoshisha UniversityKyotoJapan
| | - Noriko Noguchi
- Department of Medical Life SystemsFaculty of Medical and Life SciencesDoshisha UniversityKyotoJapan
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126
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Schon EA, Area-Gomez E. Mitochondria-associated ER membranes in Alzheimer disease. Mol Cell Neurosci 2013; 55:26-36. [DOI: 10.1016/j.mcn.2012.07.011] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 07/26/2012] [Accepted: 07/27/2012] [Indexed: 01/03/2023] Open
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Danza G, Di Serio C, Ambrosio MR, Sturli N, Lonetto G, Rosati F, Rocca BJ, Ventimiglia G, del Vecchio MT, Prudovsky I, Marchionni N, Tarantini F. Notch3 is activated by chronic hypoxia and contributes to the progression of human prostate cancer. Int J Cancer 2013; 133:2577-86. [PMID: 23729168 DOI: 10.1002/ijc.28293] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 05/06/2013] [Indexed: 01/02/2023]
Abstract
Prostate cancer (PC) is still the second cause of cancer-related death among men. Although patients with metastatic presentation have an ominous outcome, the vast majority of PCs are diagnosed at an early stage. Nonetheless, even among patients with clinically localized disease the outcome may vary considerably. Other than androgen sensitivity, little is known about which other signaling pathways are deranged in aggressive, localized cancers. The elucidation of such pathways may help to develop innovative therapies aimed at specific molecular targets. We report that in a hormone-sensitive PC cell line, LNCaP, Notch3 was activated by hypoxia and sustained cell proliferation and colony formation in soft agar. Hypoxia also modulated cellular cholesterol content and the number and size of lipid rafts, causing a coalescence of small rafts into bigger clusters; under this experimental condition, Notch3 migrated from the non-raft into the raft compartment where it colocalized with the γ-secretase complex. We also looked at human PC biopsies and found that expression of Notch3 positively correlated with Gleason score and with expression of carbonic anhydrase IX, a marker of hypoxia. In conclusion, hypoxia triggers the activation of Notch3, which, in turn, sustains proliferation of PC cells. Notch3 pathway represents a promising target for adjuvant therapy in patients with PC.
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Affiliation(s)
- Giovanna Danza
- Endocrine Unit, Department of Clinical Physiopathology, University of Florence, Florence, Italy
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128
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Lagace TA, Ridgway ND. The role of phospholipids in the biological activity and structure of the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2499-510. [PMID: 23711956 DOI: 10.1016/j.bbamcr.2013.05.018] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 05/09/2013] [Accepted: 05/15/2013] [Indexed: 01/22/2023]
Abstract
The endoplasmic reticulum (ER) is an interconnected network of tubular and planar membranes that supports the synthesis and export of proteins, carbohydrates and lipids. Phospholipids, in particular phosphatidylcholine (PC), are synthesized in the ER where they have essential functions including provision of membranes required for protein synthesis and export, cholesterol homeostasis, and triacylglycerol storage and secretion. Coordination of these biological processes is essential, as highlighted by findings that link phospholipid metabolism in the ER with perturbations in lipid storage/secretion and stress responses, ultimately contributing to obesity/diabetes, atherosclerosis and neurological disorders. Phospholipid synthesis is not uniformly distributed in the ER but is localized at membrane interfaces or contact zones with other organelles, and in dynamic, proliferating ER membranes. The topology of phospholipid synthesis is an important consideration when establishing the etiology of diseases that arise from ER dysfunction. This review will highlight our current understanding of the contribution of phospholipid synthesis to proper ER function, and how alterations contribute to aberrant stress responses and disease. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
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Affiliation(s)
- Thomas A Lagace
- University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
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129
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Yang M, Virassamy B, Vijayaraj SL, Lim Y, Saadipour K, Wang YJ, Han YC, Zhong JH, Morales CR, Zhou XF. The intracellular domain of sortilin interacts with amyloid precursor protein and regulates its lysosomal and lipid raft trafficking. PLoS One 2013; 8:e63049. [PMID: 23704887 PMCID: PMC3660575 DOI: 10.1371/journal.pone.0063049] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 03/27/2013] [Indexed: 12/31/2022] Open
Abstract
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.
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Affiliation(s)
- Miao Yang
- School of Pharmacy and Medical Sciences, Sansom Institute, University of South Australia, Adelaide, Australia.
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130
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Hung YH, Bush AI, La Fontaine S. Links between copper and cholesterol in Alzheimer's disease. Front Physiol 2013; 4:111. [PMID: 23720634 PMCID: PMC3655288 DOI: 10.3389/fphys.2013.00111] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 04/30/2013] [Indexed: 01/01/2023] Open
Abstract
Altered copper homeostasis and hypercholesterolemia have been identified independently as risk factors for Alzheimer's disease (AD). Abnormal copper and cholesterol metabolism are implicated in the genesis of amyloid plaques and neurofibrillary tangles (NFT), which are two key pathological signatures of AD. Amyloidogenic processing of a sub-population of amyloid precursor protein (APP) that produces Aβ occurs in cholesterol-rich lipid rafts in copper deficient AD brains. Co-localization of Aβ and a paradoxical high concentration of copper in lipid rafts fosters the formation of neurotoxic Aβ:copper complexes. These complexes can catalytically oxidize cholesterol to generate H2O2, oxysterols and other lipid peroxidation products that accumulate in brains of AD cases and transgenic mouse models. Tau, the core protein component of NFTs, is sensitive to interactions with copper and cholesterol, which trigger a cascade of hyperphosphorylation and aggregation preceding the generation of NFTs. Here we present an overview of copper and cholesterol metabolism in the brain, and how their integrated failure contributes to development of AD.
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Affiliation(s)
- Ya Hui Hung
- Oxidation Biology Laboratory, Florey Institute of Neuroscience and Mental Health Parkville, VIC, Australia ; Centre for Neuroscience Research, The University of Melbourne Parkville, VIC, Australia
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131
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Inhibition of serine palmitoyltransferase reduces Aβ and tau hyperphosphorylation in a murine model: a safe therapeutic strategy for Alzheimer's disease. Neurobiol Aging 2013; 34:2037-51. [PMID: 23528227 DOI: 10.1016/j.neurobiolaging.2013.02.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Revised: 01/31/2013] [Accepted: 02/09/2013] [Indexed: 12/14/2022]
Abstract
The contribution of the autosomal dominant mutations to the etiology of familial Alzheimer's disease (AD) is well characterized. However, the molecular mechanisms contributing to sporadic AD are less well understood. Increased ceramide levels have been evident in AD patients. We previously reported that increased ceramide levels, regulated by increased serine palmitoyltransferase (SPT), directly mediate amyloid β (Aβ) levels. Therefore, we inhibited SPT in an AD mouse model (TgCRND8) through subcutaneous administration of L-cylcoserine. The cortical Aβ₄₂ and hyperphosphorylated tau levels were down-regulated with the inhibition of SPT/ceramide. Positive correlations were observed among cortical SPT, ceramide, and Aβ₄₂ levels. With no evident toxic effects observed, inhibition of SPT could be a safe therapeutic strategy to ameliorate the AD pathology. We previously observed that miR-137, -181c, -9, and 29a/b post-transcriptionally regulate SPT levels, and the corresponding miRNA levels in the blood sera are potential diagnostic biomarkers for AD. Here, we observe a negative correlation between cortical Aβ₄₂ and sera Aβ₄₂, and a positive correlation between cortical miRNA levels and sera miRNA levels suggesting their potential as noninvasive diagnostic biomarkers.
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132
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Effect of Different Phospholipids on α-Secretase Activity in the Non-Amyloidogenic Pathway of Alzheimer's Disease. Int J Mol Sci 2013; 14:5879-98. [PMID: 23485990 PMCID: PMC3634454 DOI: 10.3390/ijms14035879] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 01/19/2013] [Accepted: 03/01/2013] [Indexed: 12/29/2022] Open
Abstract
Alzheimer’s disease (AD) is characterized by extracellular accumulation of amyloid-β peptide (Aβ), generated by proteolytic processing of the amyloid precursor protein (APP) by β- and γ-secretase. Aβ generation is inhibited when the initial ectodomain shedding is caused by α-secretase, cleaving APP within the Aβ domain. Therefore, an increase in α-secretase activity is an attractive therapeutic target for AD treatment. APP and the APP-cleaving secretases are all transmembrane proteins, thus local membrane lipid composition is proposed to influence APP processing. Although several studies have focused on γ-secretase, the effect of the membrane lipid microenvironment on α-secretase is poorly understood. In the present study, we systematically investigated the effect of fatty acid (FA) acyl chain length (10:0, 12:0, 14:0, 16:0, 18:0, 20:0, 22:0, 24:0), membrane polar lipid headgroup (phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine), saturation grade and the FA double-bond position on α-secretase activity. We found that α-secretase activity is significantly elevated in the presence of FAs with short chain length and in the presence of polyunsaturated FAs, whereas variations in the phospholipid headgroups, as well as the double-bond position, have little or no effect on α-secretase activity. Overall, our study shows that local lipid membrane composition can influence α-secretase activity and might have beneficial effects for AD.
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133
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McGuinness B, O'Hare J, Craig D, Bullock R, Malouf R, Passmore P. Cochrane review on 'Statins for the treatment of dementia'. Int J Geriatr Psychiatry 2013; 28:119-26. [PMID: 22473869 DOI: 10.1002/gps.3797] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 02/16/2012] [Indexed: 12/31/2022]
Abstract
OBJECTIVES This review aimed to assess the clinical efficacy and tolerability of statins in the treatment of dementia. METHODS We searched the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group, The Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL and LILACS, as well as many trials registries and grey literature sources (27 October 2008). Double-blind, randomized controlled trials of statins given for at least 6 months in people with a diagnosis of dementia were included. Two independent authors extracted and assessed data independently against the inclusion criteria. Data were pooled where appropriate and entered into a meta-analysis. RESULTS Three studies were identified (748 participants, age range 50-90 years). All patients had a diagnosis of probable or possible Alzheimer's disease according to standard criteria, and most patients were established on a cholinesterase inhibitor. Change in Alzheimer's Disease Assessment Scale cognitive subscale from baseline was a primary outcome in three studies; when data were pooled, statins did not provide any beneficial effect in this cognitive measure (mean difference -1.12; 95% confidence interval -3.99, 1.75; p = 0.44). All studies provided a change in Mini-Mental State Examination from baseline; there was no significant benefit from statins in this cognitive measure when the data were pooled (mean difference -1.53; 95% confidence interval -3.28; 0.21, p = 0.08). There were no studies identified assessing the role of statins in treatment of vascular dementia. There was no evidence that statins were detrimental to cognition. CONCLUSIONS There is insufficient evidence to recommend statins for the treatment of dementia.
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134
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Phospholipids and Alzheimer's disease: alterations, mechanisms and potential biomarkers. Int J Mol Sci 2013; 14:1310-22. [PMID: 23306153 PMCID: PMC3565322 DOI: 10.3390/ijms14011310] [Citation(s) in RCA: 139] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 12/20/2012] [Accepted: 12/24/2012] [Indexed: 02/07/2023] Open
Abstract
Brain is one of the richest organs in lipid content. Phospholipids (glycerophospholipids and sphingolipids) are important building blocks of cell membranes, which provide an optimal environment for protein interactions, trafficking and function. Because of that, alterations in their cellular levels could lead to different pathogenic processes in the brain, such as in Alzheimer’s disease (AD), the most common type of dementia among older populations. There is increasing evidence that phospholipid changes occur during pathogenic processes in AD. It is known that lipids are tightly connected with metabolism of the Amyloid Precursor Protein (APP), which produces Amyloid-beta peptide (Aβ), the main component of senile plaques, which represent the main pathological hallmark of AD. However, the mechanism(s) of the lipid-effect on Aβ metabolism and AD pathogenesis is still not completely understood. This review summarizes the current knowledge on phospholipid changes occurring during normal aging and discusses phospholipid changes in the human brain associated with different stages of AD, as well changes in the cerebrospinal fluid and blood/plasma, which are interesting potential biomarkers for AD diagnosis and disease monitoring. At the end, we have discussed future perspectives of phospholipid changes as potential biomarkers and as targets for development of novel treatment strategies against AD.
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135
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Keeney JTR, Swomley AM, Förster S, Harris JL, Sultana R, Butterfield DA. Apolipoprotein A-I: insights from redox proteomics for its role in neurodegeneration. Proteomics Clin Appl 2013; 7:109-22. [PMID: 23027708 PMCID: PMC3760000 DOI: 10.1002/prca.201200087] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 09/03/2012] [Indexed: 01/03/2023]
Abstract
Proteomics has a wide range of applications, including determination of differences in the proteome in terms of expression and post-translational protein modifications. Redox proteomics allows the identification of specific targets of protein oxidation in a biological sample. Using proteomic techniques, apolipoprotein A-I (ApoA-I) has been found at decreased levels in subjects with a variety of neurodegenerative disorders including in the serum and cerebrospinal fluid (CSF) of Alzheimer disease (AD), Parkinson disease (PD), and Down syndrome (DS) with gout subjects. ApoA-I plays roles in cholesterol transport and regulation of inflammation. Redox proteomics further showed ApoA-I to be highly oxidatively modified and particularly susceptible to modification by 4-hydroxy-2-trans-nonenal (HNE), a lipid peroxidation product. In the current review, we discuss the consequences of oxidation of ApoA-I in terms of neurodegeneration. ROS-associated chemotherapy related ApoA-I oxidation leads to elevation of peripheral levels of tumor necrosis factor-α (TNF-α) that can cross the blood-brain barrier (BBB) causing a signaling cascade that can contribute to neuronal death, likely a contributor to what patients refer to as "chemobrain." Current evidence suggests ApoA-I to be a promising diagnostic marker as well as a potential target for therapeutic strategies in these neurodegenerative disorders.
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Affiliation(s)
- Jeriel T. R. Keeney
- Department of Chemistry, Center of Membrane Sciences, Sanders Brown Center on Aging, University of Kentucky, Lexington, KY 40506, USA
| | - Aaron M. Swomley
- Department of Chemistry, Center of Membrane Sciences, Sanders Brown Center on Aging, University of Kentucky, Lexington, KY 40506, USA
| | - Sarah Förster
- Department of Chemistry, Center of Membrane Sciences, Sanders Brown Center on Aging, University of Kentucky, Lexington, KY 40506, USA
- Institute of Animal Sciences, Department of Biochemistry, University of Bonn, 53115 Bonn, Germany
| | - Jessica L. Harris
- Department of Chemistry, Center of Membrane Sciences, Sanders Brown Center on Aging, University of Kentucky, Lexington, KY 40506, USA
| | - Rukhsana Sultana
- Department of Chemistry, Center of Membrane Sciences, Sanders Brown Center on Aging, University of Kentucky, Lexington, KY 40506, USA
| | - D. Allan Butterfield
- Department of Chemistry, Center of Membrane Sciences, Sanders Brown Center on Aging, University of Kentucky, Lexington, KY 40506, USA
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136
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γ-Secretase-Dependent Proteolysis of Transmembrane Domain of Amyloid Precursor Protein: Successive Tri- and Tetrapeptide Release in Amyloid β-Protein Production. Int J Alzheimers Dis 2012; 2012:591392. [PMID: 23346458 PMCID: PMC3549393 DOI: 10.1155/2012/591392] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 11/27/2012] [Accepted: 12/12/2012] [Indexed: 12/16/2022] Open
Abstract
γ-Secretase cleaves the carboxyl-terminal fragment (βCTF) of APP not only in the middle of the transmembrane domain (γ-cleavage), but also at sites close to the membrane/cytoplasm boundary (ε-cleavage), to produce the amyloid β protein (Aβ) and the APP intracellular domain (AICD), respectively. The AICD49–99 and AICD50–99 species were identified as counterparts of the long Aβ species Aβ48 and Aβ49, respectively. We found that Aβ40 and AICD50–99 were the predominant species in cells expressing wild-type APP and presenilin, whereas the production of Aβ42 and AICD49–99 was enhanced in cells expressing familial Alzheimer's disease mutants of APP and presenilin. These long Aβ species were identified in cell lysates and mouse brain extracts, which suggests that ε-cleavage is the first cleavage of βCTF to produce Aβ by γ-secretase. Here, we review the progress of research on the mechanism underlying the proteolysis of the APP transmembrane domain based on tri- and tetrapeptide release.
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137
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Thathiah A, Horré K, Snellinx A, Vandewyer E, Huang Y, Ciesielska M, De Kloe G, Munck S, De Strooper B. β-arrestin 2 regulates Aβ generation and γ-secretase activity in Alzheimer's disease. Nat Med 2012. [PMID: 23202293 DOI: 10.1038/nm.3023] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
β-arrestins are associated with numerous aspects of G protein-coupled receptor (GPCR) signaling and regulation and accordingly influence diverse physiological and pathophysiological processes. Here we report that β-arrestin 2 expression is elevated in two independent cohorts of individuals with Alzheimer's disease. Overexpression of β-arrestin 2 leads to an increase in amyloid-β (Aβ) peptide generation, whereas genetic silencing of Arrb2 (encoding β-arrestin 2) reduces generation of Aβ in cell cultures and in Arrb2(-/-) mice. Moreover, in a transgenic mouse model of Alzheimer's disease, genetic deletion of Arrb2 leads to a reduction in the production of Aβ(40) and Aβ(42). Two GPCRs implicated previously in Alzheimer's disease (GPR3 and the β(2)-adrenergic receptor) mediate their effects on Aβ generation through interaction with β-arrestin 2. β-arrestin 2 physically associates with the Aph-1a subunit of the γ-secretase complex and redistributes the complex toward detergent-resistant membranes, increasing the catalytic activity of the complex. Collectively, these studies identify β-arrestin 2 as a new therapeutic target for reducing amyloid pathology and GPCR dysfunction in Alzheimer's disease.
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Affiliation(s)
- Amantha Thathiah
- Vlaams Instituut voor Biotechnologie Center for the Biology of Disease, Leuven, Belgium
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138
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Hao CC, Sun RG, Zhang J. Interaction of Egg-Sphingomyelin with DOPC in Langmuir Monolayers. CHINESE J CHEM PHYS 2012. [DOI: 10.1088/1674-0068/25/06/691-696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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139
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Pernber Z, Blennow K, Bogdanovic N, Månsson JE, Blomqvist M. Altered distribution of the gangliosides GM1 and GM2 in Alzheimer's disease. Dement Geriatr Cogn Disord 2012; 33:174-88. [PMID: 22572791 DOI: 10.1159/000338181] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/05/2012] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Alzheimer's disease (AD) is a neurodegenerative disorder where β-amyloid tends to aggregate and form plaques. Lipid raft-associated ganglioside GM1 has been suggested to facilitate β-amyloid aggregation; furthermore, GM1 and GM2 are increased in lipid rafts isolated from cerebral cortex of AD cases. AIM/METHOD The distribution of GM1 and GM2 was studied by immunohistochemistry in the frontal and temporal cortex of AD cases. Frontotemporal dementia (FTD) was included as a contrast group. RESULTS The distribution of GM1 and GM2 changes during the process of AD (n = 5) and FTD (n = 3) compared to controls (n = 5). Altered location of the GM1-positive small circular structures seems to be associated with myelin degradation. In the grey matter, the staining of GM1-positive plasma membranes might reflect neuronal loss in the AD/FTD tissue. The GM1-positive compact bundles were only visible in cells located in the AD frontal grey matter, possibly reflecting raft formation of GM1 and thus a pathological connection. Furthermore, our results suggest GM2 to be enriched within vesicles of pyramidal neurons of the AD/FTD brain. CONCLUSION Our study supports the biochemical finding of ganglioside accumulation in cellular membranes of AD patients and shows a redistribution of these molecules.
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Affiliation(s)
- Z Pernber
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg University, Molndal, Sweden
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140
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Abstract
Intracellular membrane trafficking along endocytic and secretory transport pathways plays a critical role in diverse cellular functions including both developmental and pathological processes. Briefly, proteins and lipids destined for transport to distinct locations are collectively assembled into vesicles and delivered to their target site by vesicular fusion. SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins are required for these events, during which v-SNAREs (vesicle SNAREs) interact with t-SNAREs (target SNAREs) to allow transfer of cargo from donor vesicle to target membrane. Recently, the t-SNARE family member, syntaxin-6, has been shown to play an important role in the transport of proteins that are key to diverse cellular dynamic processes. In this paper, we briefly discuss the specific role of SNAREs in various mammalian cell types and comprehensively review the various roles of the Golgi- and endosome-localized t-SNARE, syntaxin-6, in membrane trafficking during physiological as well as pathological conditions.
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141
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Phosphatidylinositol 4-Kinases and PI4P Metabolism in the Nervous System: Roles in Psychiatric and Neurological Diseases. Mol Neurobiol 2012; 47:361-72. [DOI: 10.1007/s12035-012-8358-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 09/27/2012] [Indexed: 01/18/2023]
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142
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De Strooper B, Scorrano L. Close encounter: mitochondria, endoplasmic reticulum and Alzheimer's disease. EMBO J 2012; 31:4095-7. [PMID: 23047154 DOI: 10.1038/emboj.2012.279] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Bart De Strooper
- VIB Center for the Biology of Disease, VIB, KuLeuven, Center for Human Genetics, Leuven, Belgium.
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143
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Maulik M, Westaway D, Jhamandas JH, Kar S. Role of cholesterol in APP metabolism and its significance in Alzheimer's disease pathogenesis. Mol Neurobiol 2012; 47:37-63. [PMID: 22983915 DOI: 10.1007/s12035-012-8337-y] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 08/19/2012] [Indexed: 12/21/2022]
Abstract
Alzheimer's disease (AD) is a complex multifactorial neurodegenerative disorder believed to be initiated by accumulation of amyloid β (Aβ)-related peptides derived from proteolytic processing of amyloid precursor protein (APP). Research over the past two decades provided a mechanistic link between cholesterol and AD pathogenesis. Genetic polymorphisms in genes regulating the pivotal points in cholesterol metabolism have been suggested to enhance the risk of developing AD. Altered neuronal membrane cholesterol level and/or subcellular distribution have been implicated in aberrant formation, aggregation, toxicity, and degradation of Aβ-related peptides. However, the results are somewhat contradictory and we still do not have a complete understanding on how cholesterol can influence AD pathogenesis. In this review, we summarize our current understanding on the role of cholesterol in regulating the production/function of Aβ-related peptides and also examine the therapeutic potential of regulating cholesterol homeostasis in the treatment of AD pathology.
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Affiliation(s)
- M Maulik
- Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta, Canada, T6G 2M8
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144
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Abstract
Prion disease research has opened up the "black-box" of neurodegeneration, defining a key role for protein misfolding wherein a predominantly alpha-helical precursor protein, PrP (C), is converted to a disease-associated, β-sheet enriched isoform called PrP (Sc). In Alzheimer disease (AD) the Aβ peptide derived from the β-amyloid precuror protein APP folds in β-sheet amyloid. Early thoughts along the lines of overlap may have been on target, (1) but were eclipsed by a simultaneous (but now anachronistic) controversy over the role of PrP (Sc) in prion diseases. (2) (,) (3) Nonetheless, as prion diseases such as Creutzfeldt-Jakob Disease (CJD) are themselves rare and can include an overt infectious mode of transmission, and as familial prion diseases and familial AD involve different genes, an observer might reasonably have concluded that prion research could occasionally catalyze ideas in AD, but could never provide concrete overlaps at the mechanistic level. Surprisingly, albeit a decade or three down the road, several prion/AD commonalities can be found within the contemporary literature. One important prion/AD overlap concerns seeded spread of Aβ aggregates by intracerebral inoculation much like prions, (4) and, with a neuron-to-neuron 'spreading' also reported for pathologic forms of other misfolded proteins, Tau (5) (,) (6) and α-synuclein in the case of Parkinson Disease. (7) (,) (8) The concept of seeded spread has been discussed extensively elsewhere, sometimes under the rubric of "prionoids" (9), and lies outside the scope of this particular review where we will focus upon PrP (C). From this point the story can now be subdivided into four strands of investigation: (1) pathologic effects of Aβ can be mediated by binding to PrP (C), (10) (2) the positioning of endoproteolytic processing events of APP by pathologic (β-cleavage + γ-cleavage) and non-pathologic (α-cleavage + γ-cleavage) secretase pathways is paralleled by seemingly analogous α- and β-like cleavage of PrP (C) (Fig. 1) (3) similar lipid raft environments for PrP (C) and APP processing machinery, (11) (-) (13) and perhaps in consequence, overlaps in repertoire of the PrP (C) and APP protein interactors ("interactomes"), (14) (,) (15) and (4) rare kindreds with mixed AD and prion pathologies. (16) Here we discuss confounds, consensus and conflict associated with parameters that apply to these experimental settings.
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Affiliation(s)
- David Westaway
- Department of Medicine (Neurology); University of Alberta; Edmonton, AB Canada
- Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton, AB Canada
- Department of Biochemistry; University of Alberta; Edmonton, AB Canada
| | - Jack H. Jhamandas
- Department of Medicine (Neurology); University of Alberta; Edmonton, AB Canada
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145
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Upregulated function of mitochondria-associated ER membranes in Alzheimer disease. EMBO J 2012; 31:4106-23. [PMID: 22892566 PMCID: PMC3492725 DOI: 10.1038/emboj.2012.202] [Citation(s) in RCA: 459] [Impact Index Per Article: 38.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 06/28/2012] [Indexed: 12/12/2022] Open
Abstract
Alzheimer disease (AD) associated (gamma)-secretase components presenilin-1 and -2 accumulate in MAM, an LR-like ER subcompartment connected to mitochondria. MAM function increases in patients with familial or sporadic AD and may be linked to AD pathogenesis. Alzheimer disease (AD) is associated with aberrant processing of the amyloid precursor protein (APP) by γ-secretase, via an unknown mechanism. We recently showed that presenilin-1 and -2, the catalytic components of γ-secretase, and γ-secretase activity itself, are highly enriched in a subcompartment of the endoplasmic reticulum (ER) that is physically and biochemically connected to mitochondria, called mitochondria-associated ER membranes (MAMs). We now show that MAM function and ER–mitochondrial communication—as measured by cholesteryl ester and phospholipid synthesis, respectively—are increased significantly in presenilin-mutant cells and in fibroblasts from patients with both the familial and sporadic forms of AD. We also show that MAM is an intracellular detergent-resistant lipid raft (LR)-like domain, consistent with the known presence of presenilins and γ-secretase activity in rafts. These findings may help explain not only the aberrant APP processing but also a number of other biochemical features of AD, including altered lipid metabolism and calcium homeostasis. We propose that upregulated MAM function at the ER–mitochondrial interface, and increased cross-talk between these two organelles, may play a hitherto unrecognized role in the pathogenesis of AD.
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146
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Kadurin I, Alvarez-Laviada A, Ng SFJ, Walker-Gray R, D'Arco M, Fadel MG, Pratt WS, Dolphin AC. Calcium currents are enhanced by α2δ-1 lacking its membrane anchor. J Biol Chem 2012; 287:33554-66. [PMID: 22869375 PMCID: PMC3460456 DOI: 10.1074/jbc.m112.378554] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The accessory α(2)δ subunits of voltage-gated calcium channels are membrane-anchored proteins, which are highly glycosylated, possess multiple disulfide bonds, and are post-translationally cleaved into α(2) and δ. All α(2)δ subunits have a C-terminal hydrophobic, potentially trans-membrane domain and were described as type I transmembrane proteins, but we found evidence that they can be glycosylphosphatidylinositol-anchored. To probe further the function of membrane anchoring in α(2)δ subunits, we have now examined the properties of α(2)δ-1 constructs truncated at their putative glycosylphosphatidylinositol anchor site, located before the C-terminal hydrophobic domain (α(2)δ-1ΔC-term). We find that the majority of α(2)δ-1ΔC-term is soluble and secreted into the medium, but unexpectedly, some of the protein remains associated with detergent-resistant membranes, also termed lipid rafts, and is extrinsically bound to the plasma membrane. Furthermore, heterologous co-expression of α(2)δ-1ΔC-term with Ca(V)2.1/β1b results in a substantial enhancement of the calcium channel currents, albeit less than that produced by wild-type α(2)δ-1. These results call into question the role of membrane anchoring of α(2)δ subunits for calcium current enhancement.
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Affiliation(s)
- Ivan Kadurin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.
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147
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Gwon AR, Park JS, Arumugam TV, Kwon YK, Chan SL, Kim SH, Baik SH, Yang S, Yun YK, Choi Y, Kim S, Tang SC, Hyun DH, Cheng A, Dann CE, Bernier M, Lee J, Markesbery WR, Mattson MP, Jo DG. Oxidative lipid modification of nicastrin enhances amyloidogenic γ-secretase activity in Alzheimer's disease. Aging Cell 2012; 11:559-68. [PMID: 22404891 DOI: 10.1111/j.1474-9726.2012.00817.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The cause of elevated level of amyloid β-peptide (Aβ42) in common late-onset sporadic [Alzheimer's disease (AD)] has not been established. Here, we show that the membrane lipid peroxidation product 4-hydroxynonenal (HNE) is associated with amyloid and neurodegenerative pathologies in AD and that it enhances γ-secretase activity and Aβ42 production in neurons. The γ-secretase substrate receptor, nicastrin, was found to be modified by HNE in cultured neurons and in brain specimens from patients with AD, in which HNE-nicastrin levels were found to be correlated with increased γ-secretase activity and Aβ plaque burden. Furthermore, HNE modification of nicastrin enhanced its binding to the γ-secretase substrate, amyloid precursor protein (APP) C99. In addition, the stimulation of γ-secretase activity and Aβ42 production by HNE were blocked by an HNE-scavenging histidine analog in a 3xTgAD mouse model of AD. These findings suggest a specific molecular mechanism by which oxidative stress increases Aβ42 production in AD and identify HNE as a novel therapeutic target upstream of the γ-secretase cleavage of APP.
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Affiliation(s)
- A-Ryeong Gwon
- School of Pharmacy, Sungkyunkwan University, Suwon, Korea
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Mielke MM, Bandaru VVR, Haughey NJ, Xia J, Fried LP, Yasar S, Albert M, Varma V, Harris G, Schneider EB, Rabins PV, Bandeen-Roche K, Lyketsos CG, Carlson MC. Serum ceramides increase the risk of Alzheimer disease: the Women's Health and Aging Study II. Neurology 2012; 79:633-41. [PMID: 22815558 DOI: 10.1212/wnl.0b013e318264e380] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVES Previous studies have shown that high serum ceramides are associated with memory impairment and hippocampal volume loss, but have not examined dementia as an outcome. The aim of this study was to examine whether serum ceramides and sphingomyelins (SM) were associated with an increased risk of all-cause dementia and Alzheimer disease (AD). METHODS Participants included 99 women without dementia aged 70-79, with baseline serum SM and ceramides, enrolled in a longitudinal population-based study and followed for up to 6 visits over 9 years. Baseline lipids, in tertiles, were examined in relation to all-cause dementia and AD using discrete time Cox proportional survival analysis. Lipids were analyzed using electrospray ionization tandem mass spectrometry. RESULTS Twenty-seven (27.3%) of the 99 women developed incident dementia. Of these, 18 (66.7%) were diagnosed with probable AD. Higher baseline serum ceramides, but not SM, were associated with an increased risk of AD; these relationships were stronger than with all-cause dementia. Compared to the lowest tertile, the middle and highest tertiles of ceramide d18:1-C16:0 were associated with a 10-fold (95% confidence interval [CI] 1.2-85.1) and 7.6-fold increased risk of AD (95% CI 0.9-62.1), respectively. The highest tertiles of ceramide d18:1-C24:0 (hazard ratio [HR] = 5.1, 95% CI 1.1-23.6) and lactosylceramide (HR = 9.8, 95% CI 1.2-80.1) were also associated with risk of AD. Total and high-density lipoprotein cholesterol and triglycerides were not associated with dementia or AD. CONCLUSIONS Results from this preliminary study suggest that particular species of serum ceramides are associated with incident AD and warrant continued examination in larger studies.
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Affiliation(s)
- Michelle M Mielke
- Division of Epidemiology, College of Medicine, Mayo Clinic, Rochester, MN, USA.
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Abstract
The Alzheimer's disease (AD)-associated amyloid-β protein precursor (AβPP) is cleaved by α-, β-, and presenilin (PS)/γ-secretases through sequential regulated proteolysis. These proteolytic events control the generation of the pathogenic amyloid-β (Aβ) peptide, which excessively accumulates in the brains of individuals afflicted by AD. A growing number of additional proteins cleaved by PS/γ-secretase continue to be discovered. Similarly to AβPP, most of these proteins are type-I transmembrane proteins involved in vital signaling functions regulating cell fate, adhesion, migration, neurite outgrowth, or synaptogenesis. All the identified proteins share common structural features, which are typical for their proteolysis. The consequences of the PS/γ-secretase-mediated cleavage on the function of many of these proteins are largely unknown. Here, we review the current literature on the proteolytic processing mediated by the versatile PS/γ-secretase complex. We begin by discussing the steps of AβPP processing and PS/γ-secretase complex composition and localization, which give clues to how and where the processing of other PS/γ-secretase substrates may take place. Then we summarize the typical features of PS/γ-secretase-mediated protein processing. Finally, we recapitulate the current knowledge on the possible physiological function of PS/γ-secretase-mediated cleavage of specific substrate proteins.
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Affiliation(s)
- Annakaisa Haapasalo
- Institute of Clinical Medicine-Neurology, University of Eastern Finland, Kuopio, Finland.
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Endolysosome involvement in LDL cholesterol-induced Alzheimer's disease-like pathology in primary cultured neurons. Life Sci 2012; 91:1159-68. [PMID: 22580286 DOI: 10.1016/j.lfs.2012.04.039] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Revised: 04/19/2012] [Accepted: 04/24/2012] [Indexed: 12/26/2022]
Abstract
AIMS Elevated levels of circulating cholesterol are extrinsic factors contributing to the pathogenesis of sporadic Alzheimer's disease (AD). We showed previously that rabbits fed a cholesterol-enriched diet exhibited blood-brain barrier (BBB) dysfunction, increased accumulation of apolipoprotein B (ApoB) in brain neurons, and endolysosomes in brain had disturbed structures and functions. These effects were linked to increased amyloid beta (Aβ) production, increased tau-pathology, and disrupted synaptic integrity. Because pathological changes to endolysosomes represent a very early event in sporadic AD, we determined here the extent to which ApoB-containing LDL cholesterol altered the structure and function of endolysosomes and contributed to the development of AD-like pathology in primary cultured neurons. MAIN METHODS Cholesterol distribution and endolysosome morphology were determined histologically. Endolysosome pH was measured ratio-metrically with LysoSensor dye. Endolysosome enzyme activity was measured for acid phosphatase, cathepsins B and D, and beta-site APP cleaving enzyme 1 (BACE-1). AD-like pathologies, including increased production of Aβ, increased tau-pathology, and disrupted synaptic integrity were determined using ELISA, immunoblotting, and immunostaining techniques. KEY FINDINGS Treatment of neurons with ApoB-containing LDL cholesterol increased endolysosome accumulation of cholesterol, enlarged endolysosomes, and elevated endolysosome pH. In addition, ApoB-containing LDL cholesterol increased endolysosome accumulation of BACE-1, enhanced BACE-1 activity, increased Aβ levels, increased levels of phosphorylated tau, and decreased levels of synaptophysin. SIGNIFICANCE Our findings suggest strongly that alterations in the structure and function of endolysosomes play a key role in the exhibition of pathological features of AD that result from neuronal exposure to ApoB-containing LDL cholesterol.
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