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Sun Y, Islam S, Gao Y, Nakamura T, Tomita T, Michikawa M, Zou K. Presenilin deficiency enhances tau phosphorylation and its secretion. J Neurochem 2024. [PMID: 38946496 DOI: 10.1111/jnc.16155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 05/09/2024] [Accepted: 05/20/2024] [Indexed: 07/02/2024]
Abstract
Alzheimer's disease (AD) is characterized by the accumulation of abnormally folded amyloid β-protein (Aβ) in the brain parenchyma and phosphorylated tau in neurons. Presenilin (PS, PSEN) 1 and PS2 are essential components of γ-secretase, which is responsible for the cleavage of amyloid precursor protein (APP) to generate Aβ. PSEN mutations are associated with tau aggregation in frontotemporal dementia, regardless of the presence or absence of Aβ pathology. However, the mechanism by which PS regulates tau aggregation is still unknown. Here, we found that tau phosphorylation and secretion were significantly increased in PS double-knock-out (PS1/2-/-) fibroblasts compared with wild-type fibroblasts. Tau-positive vesicles in the cytoplasm were significantly increased in PS1/2-/- fibroblasts. Active GSK-3β was increased in PS1/2-/- fibroblasts, and inhibiting GSK3β activity in PS1/2-/- fibroblasts resulted in decreased tau phosphorylation and secretion. Transfection of WT human PS1 and PS2 reduced the secretion of phosphorylated tau and active GSK-3β in PS1/2-/- fibroblasts. However, PS1D257A without γ-secretase activity did not decrease the secretion of phosphorylated tau. Furthermore, nicastrin deficiency also increased tau phosphorylation and secretion. These results suggest that deficient PS complex maturation may increase tau phosphorylation and secretion. Thus, our studies discover a new pathway by which PS regulates tau phosphorylation/secretion and pathology independent of Aβ and suggest that PS serves as a potential therapeutic target for treating neurodegenerative diseases involving tau aggregation.
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Affiliation(s)
- Yang Sun
- Department of Biochemistry, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Sadequl Islam
- Department of Biochemistry, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Yuan Gao
- Department of Biochemistry, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Tomohisa Nakamura
- Department of Biochemistry, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Taisuke Tomita
- Laboratory of Neuropathology and Neuroscience, Faculty of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Makoto Michikawa
- Department of Geriatric Medicine, School of Life Dentistry at Niigata, The Nippon Dental University, Niigata, Japan
| | - Kun Zou
- Department of Biochemistry, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
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2
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Presenilin and APP Regulate Synaptic Kainate Receptors. J Neurosci 2022; 42:9253-9262. [PMID: 36288945 PMCID: PMC9761675 DOI: 10.1523/jneurosci.0297-22.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 08/25/2022] [Accepted: 09/27/2022] [Indexed: 02/02/2023] Open
Abstract
Kainate receptors (KARs) form a family of ionotropic glutamate receptors that regulate the activity of neuronal networks by both presynaptic and postsynaptic mechanisms. Their implication in pathologies is well documented for epilepsy. The higher prevalence of epileptic symptoms in Alzheimer's disease (AD) patients questions the role of KARs in AD. Here we investigated whether the synaptic expression and function of KARs was impaired in mouse models of AD. We addressed this question by immunostaining and electrophysiology at synapses between mossy fibers and CA3 pyramidal cells, in which KARs are abundant and play a prominent physiological role. We observed a decrease of the immunostaining for GluK2 in the stratum lucidum in CA3, and of the amplitude and decay time of synaptic currents mediated by GluK2-containing KARs in an amyloid mouse model (APP/PS1) of AD. Interestingly, a similar phenotype was observed in CA3 pyramidal cells in male and female mice with a genetic deletion of either presenilin or APP/APLP2 as well as in organotypic cultures treated with γ-secretase inhibitors. Finally, the GluK2 protein interacts with full-length and C-terminal fragments of APP. Overall, our data suggest that APP stabilizes KARs at synapses, possibly through a transsynaptic mechanism, and this interaction is under the control the γ-secretase proteolytic activity of presenilin.SIGNIFICANCE STATEMENT Synaptic impairment correlates strongly with cognitive deficits in Alzheimer's disease (AD). In this context, many studies have addressed the dysregulation of AMPA and NMDA ionotropic glutamate receptors. Kainate receptors (KARs), which form the third family of iGluRs, represent an underestimated actor in the regulation of neuronal circuits and have not yet been examined in the context of AD. Here we provide evidence that synaptic KARs are markedly impaired in a mouse model of AD. Additional experiments indicate that the γ-secretase activity of presenilin acting on the amyloid precursor protein controls synaptic expression of KAR. This study clearly indicates that KARs should be taken into consideration whenever addressing synaptic dysfunction and related cognitive deficits in the context of AD.
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3
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Jordà‐Siquier T, Petrel M, Kouskoff V, Smailovic U, Cordelières F, Frykman S, Müller U, Mulle C, Barthet G. APP accumulates with presynaptic proteins around amyloid plaques: A role for presynaptic mechanisms in Alzheimer's disease? Alzheimers Dement 2022; 18:2099-2116. [PMID: 35076178 PMCID: PMC9786597 DOI: 10.1002/alz.12546] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 09/21/2021] [Accepted: 10/25/2021] [Indexed: 01/31/2023]
Abstract
In Alzheimer's disease (AD), the distribution of the amyloid precursor protein (APP) and its fragments other than amyloid beta, has not been fully characterized. Here, we investigate the distribution of APP and its fragments in human AD brain samples and in mouse models of AD in reference to its proteases, synaptic proteins, and histopathological features characteristic of the AD brain, by combining an extensive set of histological and analytical tools. We report that the prominent somatic distribution of APP observed in control patients remarkably vanishes in human AD patients to the benefit of dense accumulations of extra-somatic APP, which surround dense-core amyloid plaques enriched in APP-Nter. These features are accentuated in patients with familial forms of the disease. Importantly, APP accumulations are enriched in phosphorylated tau and presynaptic proteins whereas they are depleted of post-synaptic proteins suggesting that the extra-somatic accumulations of APP are of presynaptic origin. Ultrastructural analyses unveil that APP concentrates in autophagosomes and in multivesicular bodies together with presynaptic vesicle proteins. Altogether, alteration of APP distribution and its accumulation together with presynaptic proteins around dense-core amyloid plaques is a key histopathological feature in AD, lending support to the notion that presynaptic failure is a strong physiopathological component of AD.
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Affiliation(s)
- Tomàs Jordà‐Siquier
- University Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297BordeauxFrance
| | - Melina Petrel
- University Bordeaux, CNRS, INSERM, Bordeaux Imaging Center, BIC, UMS 3420, US 4BordeauxFrance
| | - Vladimir Kouskoff
- University Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297BordeauxFrance
| | - Una Smailovic
- Division of Neurogeriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and SocietyKarolinska InstitutetSolnaSweden
| | - Fabrice Cordelières
- University Bordeaux, CNRS, INSERM, Bordeaux Imaging Center, BIC, UMS 3420, US 4BordeauxFrance
| | - Susanne Frykman
- Division of Neurogeriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and SocietyKarolinska InstitutetSolnaSweden
| | - Ulrike Müller
- Institute for Pharmacy and Molecular BiotechnologyHeidelbergGermany
| | - Christophe Mulle
- University Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297BordeauxFrance
| | - Gaël Barthet
- University Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297BordeauxFrance
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4
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Crite M, DiMaio D. Human Papillomavirus L2 Capsid Protein Stabilizes γ-Secretase during Viral Infection. Viruses 2022; 14:804. [PMID: 35458534 PMCID: PMC9027364 DOI: 10.3390/v14040804] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 04/08/2022] [Accepted: 04/11/2022] [Indexed: 02/04/2023] Open
Abstract
Intracellular trafficking of human papillomavirus (HPV) during virus entry requires γ-secretase, a cellular protease consisting of a complex of four cellular transmembrane (TM) proteins. γ-secretase typically cleaves substrate proteins but it plays a non-canonical role during HPV entry. γ-secretase binds to the HPV minor capsid protein L2 and facilitates its insertion into the endosomal membrane. After insertion, L2 protrudes into the cytoplasm, which allows HPV to bind other cellular factors required for proper virus trafficking into the retrograde transport pathway. Here, we further characterize the interaction between γ-secretase and HPV L2. We show that γ-secretase is required for cytoplasmic protrusion of L2 and that L2 associates strongly with the PS1 catalytic subunit of γ-secretase and stabilizes the γ-secretase complex. Mutational studies revealed that a putative TM domain in HPV16 L2 cannot be replaced by a foreign TM domain, that infectivity of HPV TM mutants is tightly correlated with γ-secretase binding and stabilization, and that the L2 TM domain is required for protrusion of the L2 protein into the cytoplasm. These results provide new insight into the interaction between γ-secretase and L2 and highlight the importance of the native HPV L2 TM domain for proper virus trafficking during entry.
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Affiliation(s)
- Mac Crite
- Department of Microbial Pathogenesis, Yale University, New Haven, CT 06511, USA;
| | - Daniel DiMaio
- Department of Genetics, Yale University, New Haven, CT 06511, USA
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5
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Yoon Y, Voloudakis G, Doran N, Zhang E, Dimovasili C, Chen L, Shao Z, Darmanis S, Tang C, Tang J, Wang VX, Hof PR, Robakis NK, Georgakopoulos A. PS1 FAD mutants decrease ephrinB2-regulated angiogenic functions, ischemia-induced brain neovascularization and neuronal survival. Mol Psychiatry 2021; 26:1996-2012. [PMID: 32541930 PMCID: PMC7736163 DOI: 10.1038/s41380-020-0812-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 05/29/2020] [Accepted: 06/04/2020] [Indexed: 12/12/2022]
Abstract
Microvascular pathology and ischemic lesions contribute substantially to neuronal dysfunction and loss that lead to Alzheimer disease (AD). To facilitate recovery, the brain stimulates neovascularization of damaged tissue via sprouting angiogenesis, a process regulated by endothelial cell (EC) sprouting and the EphB4/ephrinB2 system. Here, we show that in cultures of brain ECs, EphB4 stimulates the VE-cadherin/Rok-α angiogenic complexes known to mediate sprouting angiogenesis. Importantly, brain EC cultures expressing PS1 FAD mutants decrease the EphB4-stimulated γ-secretase cleavage of ephrinB2 and reduce production of the angiogenic peptide ephrinB2/CTF2, the VE-cadherin angiogenic complexes and EC sprouting and tube formation. These data suggest that FAD mutants may attenuate ischemia-induced brain angiogenesis. Supporting this hypothesis, ischemia-induced VE-cadherin angiogenic complexes, levels of neoangiogenesis marker Endoglin, vascular density, and cerebral blood flow recovery, are all decreased in brains of mouse models expressing PS1 FAD mutants. Ischemia-induced brain neuronal death and cognitive deficits also increase in these mice. Furthermore, a small peptide comprising the C-terminal sequence of peptide ephrinB2/CTF2 rescues angiogenic functions of brain ECs expressing PS1 FAD mutants. Together, our data show that PS1 FAD mutations impede the EphB4/ephrinB2-mediated angiogenic functions of ECs and impair brain neovascularization, neuronal survival and cognitive recovery following ischemia. Furthermore, our data reveal a novel brain angiogenic mechanism targeted by PS1 FAD mutants and a potential therapeutic target for ischemia-induced neurodegeneration. Importantly, FAD mutant effects occur in absence of neuropathological hallmarks of AD, supporting that such hallmarks may form downstream of mutant effects on neoangiogenesis and neuronal survival.
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Affiliation(s)
- YoneJung Yoon
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Georgios Voloudakis
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Nathan Doran
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Emily Zhang
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Christina Dimovasili
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Lei Chen
- Department of Physiology, Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY, 40536, USA
| | - Zhiping Shao
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Spyros Darmanis
- Departments of Bioengineering and Applied Physics, Stanford University and Chan Zuckerberg Biohub, Stanford, CA, 94305, USA
| | - Cheuk Tang
- Department of Radiology, Neuroscience and Psychiatry Translational and Molecular Imaging Institute at Mount Sinai, New York, NY, USA
| | - Jun Tang
- Department of Radiology, Neuroscience and Psychiatry Translational and Molecular Imaging Institute at Mount Sinai, New York, NY, USA
| | - Victoria X Wang
- Department of Radiology, Translational and Molecular Imaging Institute at Mount Sinai, New York, NY, USA
| | - Patrick R Hof
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Nikolaos K Robakis
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| | - Anastasios Georgakopoulos
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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6
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Bartolomé A, Liang J, Wang P, Ho DD, Pajvani UB. Angiotensin converting enzyme 2 is a novel target of the γ-secretase complex. Sci Rep 2021; 11:9803. [PMID: 33963249 PMCID: PMC8105332 DOI: 10.1038/s41598-021-89379-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 04/21/2021] [Indexed: 02/08/2023] Open
Abstract
Angiotensin converting enzyme 2 (ACE2) is a key regulator of the renin-angiotensin system, but also the functional receptor of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Based on structural similarity with other γ-secretase (γS) targets, we hypothesized that ACE2 may be affected by γS proteolytic activity. We found that after ectodomain shedding, ACE2 is targeted for intramembrane proteolysis by γS, releasing a soluble ACE2 C-terminal fragment. Consistently, chemical or genetic inhibition of γS results in the accumulation of a membrane-bound fragment of ectodomain-deficient ACE2. Although chemical inhibition of γS does not alter SARS-CoV-2 cell entry, these data point to a novel pathway for cellular ACE2 trafficking.
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Affiliation(s)
- Alberto Bartolomé
- Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Jiani Liang
- Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Pengfei Wang
- Aaron Diamond AIDS Research Center, Columbia University Irving Medical Center, New York, NY, USA
| | - David D Ho
- Aaron Diamond AIDS Research Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Utpal B Pajvani
- Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA.
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7
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Lechuga GC, Napoleão-Pêgo P, Bottino CCG, Pinho RT, Provance-Jr DW, De-Simone SG. Trypanosoma cruzi Presenilin-Like Transmembrane Aspartyl Protease: Characterization and Cellular Localization. Biomolecules 2020; 10:biom10111564. [PMID: 33212923 PMCID: PMC7698364 DOI: 10.3390/biom10111564] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 02/08/2023] Open
Abstract
The increasing detection of infections of Trypanosoma cruzi, the etiological agent of Chagas disease, in non-endemic regions beyond Latin America has risen to be a major public health issue. With an impact in the millions of people, current treatments rely on antiquated drugs that produce severe side effects and are considered nearly ineffective for the chronic phase. The minimal progress in the development of new drugs highlights the need for advances in basic research on crucial biochemical pathways in T. cruzi to identify new targets. Here, we report on the T. cruzi presenilin-like transmembrane aspartyl enzyme, a protease of the aspartic class in a unique phylogenetic subgroup with T. vivax separate from protozoans. Computational analyses suggest it contains nine transmembrane domains and an active site with the characteristic PALP motif of the A22 family. Multiple linear B-cell epitopes were identified by SPOT-synthesis analysis with Chagasic patient sera. Two were chosen to generate rabbit antisera, whose signal was primarily localized to the flagellar pocket, intracellular vesicles, and endoplasmic reticulum in parasites by whole-cell immunofluorescence. The results suggest that the parasitic presenilin-like enzyme could have a role in the secretory pathway and serve as a target for the generation of new therapeutics specific to the T. cruzi.
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Affiliation(s)
- Guilherme C. Lechuga
- Center for Technological Development in Health/National Institute of Science and Technology for Innovation on Diseases of Neglected Population (INCT-IDPN), FIOCRUZ, Rio de Janeiro 21040-900, Brazil; (G.C.L.); (P.N.-P.); (C.C.G.B.); (D.W.P.-J.)
- Cellular Ultrastructure Laboratory, FIOCRUZ, Oswaldo Cruz Institute, Rio de Janeiro 21040-900, Brazil
| | - Paloma Napoleão-Pêgo
- Center for Technological Development in Health/National Institute of Science and Technology for Innovation on Diseases of Neglected Population (INCT-IDPN), FIOCRUZ, Rio de Janeiro 21040-900, Brazil; (G.C.L.); (P.N.-P.); (C.C.G.B.); (D.W.P.-J.)
| | - Carolina C. G. Bottino
- Center for Technological Development in Health/National Institute of Science and Technology for Innovation on Diseases of Neglected Population (INCT-IDPN), FIOCRUZ, Rio de Janeiro 21040-900, Brazil; (G.C.L.); (P.N.-P.); (C.C.G.B.); (D.W.P.-J.)
| | - Rosa T. Pinho
- Clinical Immunology Laboratory, FIOCRUZ, Oswaldo Cruz Institute, Rio de Janeiro 21040-900, Brazil;
| | - David W. Provance-Jr
- Center for Technological Development in Health/National Institute of Science and Technology for Innovation on Diseases of Neglected Population (INCT-IDPN), FIOCRUZ, Rio de Janeiro 21040-900, Brazil; (G.C.L.); (P.N.-P.); (C.C.G.B.); (D.W.P.-J.)
- Interdisciplinary Medical Research Laboratory, FIOCRUZ, Oswaldo Cruz Institute, Rio de Janeiro 21040-900, Brazil
| | - Salvatore G. De-Simone
- Center for Technological Development in Health/National Institute of Science and Technology for Innovation on Diseases of Neglected Population (INCT-IDPN), FIOCRUZ, Rio de Janeiro 21040-900, Brazil; (G.C.L.); (P.N.-P.); (C.C.G.B.); (D.W.P.-J.)
- Department of Molecular and Cellular Biology, Federal Fluminense University, Niterói 24220-008, Brazil
- Correspondence: ; Tel.: +55-21-3865-8183
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8
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Bartolomé A, Liang J, Wang P, Ho DD, Pajvani UB. Angiotensin converting enzyme 2 is a novel target of the γ-secretase complex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2020. [PMID: 32908985 DOI: 10.1101/2020.09.01.277954] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Angiotensin converting enzyme 2 (ACE2) is a key regulator of the renin-angiotensin system, but also the functional receptor of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Based on structural similarity with other γ-secretase (γS) targets, we hypothesized that ACE2 may be affected by γS proteolytic activity. We found that after ectodomain shedding, ACE2 is targeted for intramembrane proteolysis by γS, releasing a soluble ACE2 C-terminal fragment. Consistently, chemical or genetic inhibition of γS results in the accumulation of a membrane-bound fragment of ectodomain-deficient ACE2. Although chemical inhibition of γS does not alter SARS-CoV-2 cell entry, these data point to a novel pathway for cellular ACE2 trafficking.
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9
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Barthet G, Mulle C. Presynaptic failure in Alzheimer's disease. Prog Neurobiol 2020; 194:101801. [PMID: 32428558 DOI: 10.1016/j.pneurobio.2020.101801] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/24/2020] [Accepted: 04/03/2020] [Indexed: 12/14/2022]
Abstract
Synaptic loss is the best correlate of cognitive deficits in Alzheimer's disease (AD). Extensive experimental evidence also indicates alterations of synaptic properties at the early stages of disease progression, before synapse loss and neuronal degeneration. A majority of studies in mouse models of AD have focused on post-synaptic mechanisms, including impairment of long-term plasticity, spine structure and glutamate receptor-mediated transmission. Here we review the literature indicating that the synaptic pathology in AD includes a strong presynaptic component. We describe the evidence indicating presynaptic physiological functions of the major molecular players in AD. These include the amyloid precursor protein (APP) and the two presenilin (PS) paralogs PS1 or PS2, genetically linked to the early-onset form of AD, in addition to tau which accumulates in a pathological form in the AD brain. Three main mechanisms participating in presynaptic functions are highlighted. APP fragments bind to presynaptic receptors (e.g. nAChRs and GABAB receptors), presenilins control Ca2+ homeostasis and Ca2+-sensors, and tau regulates the localization of presynaptic molecules and synaptic vesicles. We then discuss how impairment of these presynaptic physiological functions can explain or forecast the hallmarks of synaptic impairment and associated dysfunction of neuronal circuits in AD. Beyond the physiological roles of the AD-related proteins, studies in AD brains also support preferential presynaptic alteration. This review features presynaptic failure as a strong component of pathological mechanisms in AD.
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Affiliation(s)
- Gael Barthet
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, University of Bordeaux, France
| | - Christophe Mulle
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, University of Bordeaux, France.
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10
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Presenilin-mediated cleavage of APP regulates synaptotagmin-7 and presynaptic plasticity. Nat Commun 2018; 9:4780. [PMID: 30429473 PMCID: PMC6235831 DOI: 10.1038/s41467-018-06813-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 09/19/2018] [Indexed: 11/09/2022] Open
Abstract
Mutations of the intramembrane protease presenilin (PS) or of its main substrate, the amyloid precursor protein (APP), cause early-onset form of Alzheimer disease. PS and APP interact with proteins of the neurotransmitter release machinery without identified functional consequences. Here we report that genetic deletion of PS markedly decreases the presynaptic levels of the Ca2+ sensor synaptotagmin-7 (Syt7) leading to impaired synaptic facilitation and replenishment of synaptic vesicles. The regulation of Syt7 expression by PS occurs post-transcriptionally and depends on γ-secretase proteolytic activity. It requires the substrate APP as revealed by the combined genetic invalidation of APP and PS1, and in particular the APP-Cterminal fragments which interact with Syt7 and accumulate in synaptic terminals under pharmacological or genetic inhibition of γ-secretase. Thus, we uncover a role of PS in presynaptic mechanisms, through APP cleavage and regulation of Syt7, that highlights aberrant synaptic vesicle processing as a possible new pathway in AD. Mutations in presenilin, which cleaves amyloid precursor protein, cause familial Alzheimer’s Disease. Here, the authors show that loss of presenilin leads to loss of synaptotagmin 7, leading to impaired presynaptic release.
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11
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Huang Q, Voloudakis G, Ren Y, Yoon Y, Zhang E, Kajiwara Y, Shao Z, Xuan Z, Lebedev D, Georgakopoulos A, Robakis NK. Presenilin1/γ-secretase protects neurons from glucose deprivation-induced death by regulating miR-212 and PEA15. FASEB J 2018; 32:243-253. [PMID: 28855274 PMCID: PMC5731132 DOI: 10.1096/fj.201700447rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 08/21/2017] [Indexed: 01/01/2023]
Abstract
Reduced cerebral glucose utilization is found in aged individuals and often is an early sign of neurodegeneration. Here, we show that under glucose deprivation (GD) conditions, decreased expression of presenilin 1 (PS1) results in decreased neuronal survival, whereas increased PS1 increases neuronal survival. Inhibition of γ-secretase also decreases neuronal survival under GD conditions, which suggests the PS1/γ-secretase system protects neurons from GD-induced death. We also show that neuronal levels of the survival protein, phosphoprotein enriched in astrocytes at ∼15 kDa (PEA15), and its mRNA are regulated by PS1/γ-secretase. Furthermore, down-regulation of PEA15 decreases neuronal survival under reduced glucose conditions, whereas exogenous PEA15 increases neuronal survival even in the absence of PS1, which indicates that PEA15 promotes neuronal survival under GD conditions. The absence or reduction of PS1, as well as γ-secretase inhibitors, increases neuronal miR-212, which targets PEA15 mRNA. PS1/γ-secretase activates the transcription factor, cAMP response element-binding protein, regulating miR-212, which targets PEA15 mRNA. Taken together, our data show that under conditions of reduced glucose, the PS1/γ-secretase system decreases neuronal losses by suppressing miR-212 and increasing its target survival factor, PEA15. These observations have implications for mechanisms of neuronal death under conditions of reduced glucose and may provide targets for intervention in neurodegenerative disorders.-Huang, Q., Voloudakis, G., Ren, Y., Yoon, Y., Zhang, E., Kajiwara, Y., Shao, Z., Xuan, Z., Lebedev, D., Georgakopoulos, A., Robakis, N. K. Presenilin1/γ-secretase protects neurons from glucose deprivation-induced death by regulating miR-212 and PEA15.
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Affiliation(s)
- Qian Huang
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Georgios Voloudakis
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,School of Medicine, University of Crete, Heraklion, Crete, Greece
| | - Yimin Ren
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Yonejung Yoon
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Emily Zhang
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Yuji Kajiwara
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Zhiping Shao
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Zhao Xuan
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Denis Lebedev
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Anastasios Georgakopoulos
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Nikolaos K. Robakis
- Department of Psychiatry, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Department of Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA;,Correspondence: Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, One Gustave Levy Pl., New York, NY 10029, USA. E-mail:
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Ward J, Wang H, Saunders AJ, Tanzi RE, Zhang C. Mechanisms that synergistically regulate η-secretase processing of APP and Aη-α protein levels: relevance to pathogenesis and treatment of Alzheimer's disease. DISCOVERY MEDICINE 2017; 23:121-128. [PMID: 28371615 PMCID: PMC5524192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The pathophysiology of Alzheimer's disease (AD) is characterized by the formation of cerebral β-amyloid plaque from a small peptide amyloid-β (Aβ). Aβ is generated from the canonical amyloid-β precursor protein (APP) proteolysis pathway through β- and γ-secretases. Decreasing Aβ levels through targeting APP processing is a very promising direction in clinical trials for AD. A novel APP processing pathway was recently identified, in which η-secretase processing of APP occurs and results in the generation of the carboxy-terminal fragment-η (CTF-η or η-CTF) (Wang et al., 2015) and Aη-α peptide (Willem et al., 2015). η-Secretase processing of APP may be up-regulated by at least two mechanisms: either through inhibition of lysosomal-cathepsin degradation pathway (Wang et al., 2015) or through inhibition of BACE1 that competes with η-secretase cleavage of APP (Willem et al., 2015). A thorough characterization of η-processing of APP is critical for a better understanding of AD pathogenesis and insights into results of clinical trials of AD. Here we further investigated η-secretase processing of APP using well-characterized cell models of AD. We found that these two mechanisms act synergistically toward increasing η-secretase processing of APP and Aη-α levels. Furthermore, we evaluated the effects of several other known secretase modulators on η-processing of APP. The results of our study should advance the understanding of pathophysiology of AD, as well as enhance the knowledge in developing effective AD treatments or interventions related to η-secretase processing of APP.
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Affiliation(s)
- Joseph Ward
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Department of Neurology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Haizhi Wang
- Department of Biology, College of Art and Sciences, Drexel University, Philadelphia, PA 19104, USA
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA 19104, USA
| | - Aleister J. Saunders
- Department of Biology, College of Art and Sciences, Drexel University, Philadelphia, PA 19104, USA
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA 19104, USA
- Department of Biochemistry and Molecular Biology, College of Medicine, Drexel University, Philadelphia, PA 19104, USA
| | - Rudolph E. Tanzi
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Department of Neurology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Can Zhang
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Department of Neurology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
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13
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Elad N, De Strooper B, Lismont S, Hagen W, Veugelen S, Arimon M, Horré K, Berezovska O, Sachse C, Chávez-Gutiérrez L. The dynamic conformational landscape of gamma-secretase. J Cell Sci 2016; 128:589-98. [PMID: 25501811 PMCID: PMC4311135 DOI: 10.1242/jcs.164384] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The structure and function of the gamma-secretase proteases are of great interest because of their crucial roles in cellular and disease processes. We established a novel purification protocol for the gamma-secretase complex that involves a conformation- and complex-specific nanobody, yielding highly pure and active enzyme. Using single particle electron microscopy, we analyzed the gamma-secretase structure and its conformational variability. Under steady-state conditions, the complex adopts three major conformations, which differ in overall compactness and relative position of the nicastrin ectodomain. Occupancy of the active or substrate-binding sites by inhibitors differentially stabilizes subpopulations of particles with compact conformations, whereas a mutation linked to familial Alzheimer disease results in enrichment of extended-conformation complexes with increased flexibility. Our study presents the csecretase complex as a dynamic population of interconverting conformations, involving rearrangements at the nanometer scale and a high level of structural interdependence between subunits. The fact that protease inhibition or clinical mutations, which affect amyloid beta (Abeta) generation, enrich for particular subpopulations of conformers indicates the functional relevance of the observed dynamic changes, which are likely to be instrumental for highly allosteric behavior of the enzyme.
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Affiliation(s)
- Nadav Elad
- VIB Center for the Biology of Disease, 3000 Leuven, Belgium
- Center of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, and Leuven Research Institute for Neuroscience and Disease (LIND), 3000 Leuven, Belgium
| | - Bart De Strooper
- VIB Center for the Biology of Disease, 3000 Leuven, Belgium
- Center of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, and Leuven Research Institute for Neuroscience and Disease (LIND), 3000 Leuven, Belgium
- UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
- Authors for correspondence (; ; )
| | - Sam Lismont
- VIB Center for the Biology of Disease, 3000 Leuven, Belgium
- Center of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, and Leuven Research Institute for Neuroscience and Disease (LIND), 3000 Leuven, Belgium
| | - Wim Hagen
- European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse1, 69117 Heidelberg, Germany
| | - Sarah Veugelen
- VIB Center for the Biology of Disease, 3000 Leuven, Belgium
- Center of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, and Leuven Research Institute for Neuroscience and Disease (LIND), 3000 Leuven, Belgium
| | - Muriel Arimon
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Katrien Horré
- VIB Center for the Biology of Disease, 3000 Leuven, Belgium
- Center of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, and Leuven Research Institute for Neuroscience and Disease (LIND), 3000 Leuven, Belgium
| | - Oksana Berezovska
- European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse1, 69117 Heidelberg, Germany
| | - Carsten Sachse
- European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse1, 69117 Heidelberg, Germany
- Authors for correspondence (; ; )
| | - Lucía Chávez-Gutiérrez
- VIB Center for the Biology of Disease, 3000 Leuven, Belgium
- Center of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, and Leuven Research Institute for Neuroscience and Disease (LIND), 3000 Leuven, Belgium
- Authors for correspondence (; ; )
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14
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Bruban J, Voloudakis G, Huang Q, Kajiwara Y, Al Rahim M, Yoon Y, Shioi J, Gama Sosa MA, Shao Z, Georgakopoulos A, Robakis NK. Presenilin 1 is necessary for neuronal, but not glial, EGFR expression and neuroprotection via γ-secretase-independent transcriptional mechanisms. FASEB J 2015; 29:3702-12. [PMID: 25985800 DOI: 10.1096/fj.15-270645] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 05/04/2015] [Indexed: 11/11/2022]
Abstract
Epidermal growth factor receptor (EGFR) plays pivotal roles in cell proliferation, differentiation, and tissue development, while EGFs protect neurons from toxic insults by binding EGFR and stimulating survival signaling. Furthermore, recent evidence implicates this receptor in neurometabolic disorders like Alzheimer disease and aging. Here we show that absence of presenilin 1 (PS1) results in dramatic decrease (>95%) of neuronal EGFR and that PS1-null (PS1(-/-)) brains have reduced amounts of this receptor. PS1(-/-) cortical neurons contain little EGFR and show no epidermal growth factor-induced survival signaling or protection against excitotoxicity, but exogenous EGFR rescues both functions even in absence of PS1. EGFR mRNA is greatly reduced (>95%) in PS1(-/-) neurons, and PS1(-/-) brains contain decreased amounts of this mRNA, although PS1 affects the stability of neither EGFR nor its mRNA. Exogenous PS1 increases neuronal EGFR mRNA, while down-regulation of PS1 decreases this mRNA. These effects are neuron specific, as PS1 affects the EGFR of neither glial nor fibroblast cells. In addition, PS1 controls EGFR through novel mechanisms shared with neither γ-secretase nor PS2. Our data reveal that PS1 functions as a positive transcriptional regulator of neuronal EGFR controlling its expression in a cell-specific manner. Severe downregulation of EGFR may contribute to developmental abnormalities and lethal phenotype found in PS1, but not PS2, null mice. Furthermore, PS1 may affect neuroprotection and Alzheimer disease by controlling survival signaling of neuronal EGFR.
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Affiliation(s)
- Julien Bruban
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Georgios Voloudakis
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Qian Huang
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Yuji Kajiwara
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Md Al Rahim
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Yonejung Yoon
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Junichi Shioi
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Miguel A Gama Sosa
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Zhiping Shao
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Anastasios Georgakopoulos
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
| | - Nikolaos K Robakis
- *Departments of Psychiatry and Neuroscience, Center for Molecular Biology and Genetics of Neurodegeneration, Icahn School of Medicine at Mount Sinai, New York, New York, USA; School of Medicine, University of Crete, Heraklion, Crete, Greece; and James J. Peters Department of Veterans Affairs Medical Center, General Medical Research Service, Bronx, New York, USA
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15
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Li Y, Bohm C, Dodd R, Chen F, Qamar S, Schmitt-Ulms G, Fraser PE, St George-Hyslop PH. Structural biology of presenilin 1 complexes. Mol Neurodegener 2014; 9:59. [PMID: 25523933 PMCID: PMC4326451 DOI: 10.1186/1750-1326-9-59] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 12/12/2014] [Indexed: 11/17/2022] Open
Abstract
The presenilin genes were first identified as the site of missense mutations causing early onset autosomal dominant familial Alzheimer's disease. Subsequent work has shown that the presenilin proteins are the catalytic subunits of a hetero-tetrameric complex containing APH1, nicastrin and PEN-2. This complex (variously termed presenilin complex or gamma-secretase complex) performs an unusual type of proteolysis in which the transmembrane domains of Type I proteins are cleaved within the hydrophobic compartment of the membrane. This review describes some of the molecular and structural biology of this unusual enzyme complex. The presenilin complex is a bilobed structure. The head domain contains the ectodomain of nicastrin. The base domain contains a central cavity with a lateral cleft that likely provides the route for access of the substrate to the catalytic cavity within the centre of the base domain. There are reciprocal allosteric interactions between various sites in the complex that affect its function. For instance, binding of Compound E, a peptidomimetic inhibitor to the PS1 N-terminus, induces significant conformational changes that reduces substrate binding at the initial substrate docking site, and thus inhibits substrate cleavage. However, there is a reciprocal allosteric interaction between these sites such that prior binding of the substrate to the initial docking site paradoxically increases the binding of the Compound E peptidomimetic inhibitor. Such reciprocal interactions are likely to form the basis of a gating mechanism that underlies access of substrate to the catalytic site. An increasingly detailed understanding of the structural biology of the presenilin complex is an essential step towards rational design of substrate- and/or cleavage site-specific modulators of presenilin complex function.
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Affiliation(s)
| | | | | | | | | | | | | | - Peter H St George-Hyslop
- Cambridge Institute for Medical Research, Wellcome Trust MRC Building, Addenbrookes Hospital, Hills Road, Cambridge CB2 0XY, UK.
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16
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Roher AE, Maarouf CL, Kokjohn TA, Whiteside CM, Kalback WM, Serrano G, Belden C, Liebsack C, Jacobson SA, Sabbagh MN, Beach TG. Neuropathological and biochemical assessments of an Alzheimer's disease patient treated with the γ-secretase inhibitor semagacestat. AMERICAN JOURNAL OF NEURODEGENERATIVE DISEASE 2014; 3:115-133. [PMID: 25628963 PMCID: PMC4299724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 10/05/2014] [Indexed: 06/04/2023]
Abstract
Amyloid deposition has been implicated as the key determinant of Alzheimer's disease (AD) pathogenesis. Interventions to antagonize amyloid accumulation and mitigate dementia are now under active investigation. We conducted a combined clinical, biochemical and neuropathological assessment of a participant in a clinical trial of the γ-secretase inhibitor, semagacestat. This patient received a daily oral dose of 140 mg of semagacestat for approximately 76 weeks. Levels of brain amyloid-β (Aβ) peptides were quantified using enzyme-linked immunosorbent assays (ELISA). Western blot/scanning densitometry was performed to reveal BACE1, presenilin1, amyloid precursor protein (APP) and its proteolysis-produced C-terminal peptides APP-CT99 and APP-CT83 as well as several γ-secretase substrates. To serve as a frame of reference, the ELISA and Western analyses were performed in parallel on samples from neuropathologically confirmed non-demented control (NDC) and AD subjects who did not receive semagacestat. Neuropathology findings confirmed a diagnosis of AD with frequent amyloid deposits and neurofibrillary tangles in most areas of the cortex and subcortical nuclei as well as cerebellar amyloid plaques. Mean levels of Tris-soluble Aβ40 and glass-distilled formic acid (GDFA)/guanidine hydrochloride (GHCl)-extractable Aβ40 in the frontal lobe and GDFA/GHCl-soluble Aβ40 in the temporal lobe were increased 4.2, 9.5 and 7.7-fold, respectively, in the semagacestat-treated subject compared to those observed in the non-treated AD group. In addition, GDFA/GHCl-extracted Aβ42 was increased 2-fold in the temporal lobe relative to non-treated AD cases. No major changes in APP, β- and γ-secretase and CT99/CT83 were observed between the semagacestat-treated subject compared to either NDC or AD cases. Furthermore, the levels of γ-secretase substrates in the semagacestat-treated subject and the reference groups were also similar. Interestingly, there were significant alterations in the levels of several γ-secretase substrates between the NDC and non-treated AD subjects. This is the first reported case study of an individual enrolled in the semagacestat clinical trial. The subject of this study remained alive for ~7 months after treatment termination, therefore it is difficult to conclude whether the outcomes observed represent a consequence of semagacestat therapy. Additional evaluations of trial participants, including several who expired during the course of treatment, may provide vital clarification regarding the impacts and aftermath of γ-secretase inhibition.
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Affiliation(s)
- Alex E Roher
- The Longtine Center for Neurodegenerative Biochemistry, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
| | - Chera L Maarouf
- The Longtine Center for Neurodegenerative Biochemistry, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
| | - Tyler A Kokjohn
- Department of Microbiology, Midwestern University19555 North 59 Ave., Glendale, AZ 85308
| | - Charisse M Whiteside
- The Longtine Center for Neurodegenerative Biochemistry, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
| | - Walter M Kalback
- The Longtine Center for Neurodegenerative Biochemistry, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
| | - Geidy Serrano
- Laboratory for Neuropathology, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
| | - Christine Belden
- Cleo Roberts Center for Clinical Research, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
| | - Carolyn Liebsack
- Cleo Roberts Center for Clinical Research, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
| | - Sandra A Jacobson
- Cleo Roberts Center for Clinical Research, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
- University of Arizona College of Medicine-Phoenix550 E. Van Buren St. Phoenix, AZ 85004
| | - Marwan N Sabbagh
- Cleo Roberts Center for Clinical Research, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
| | - Thomas G Beach
- Laboratory for Neuropathology, Banner Sun Health Research Institute10515 W. Santa Fe Dr., Sun City, AZ 85351
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17
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Vorobyeva AG, Lee R, Miller S, Longen C, Sharoni M, Kandelwal PJ, Kim FJ, Marenda DR, Saunders AJ. Cyclopamine modulates γ-secretase-mediated cleavage of amyloid precursor protein by altering its subcellular trafficking and lysosomal degradation. J Biol Chem 2014; 289:33258-74. [PMID: 25281744 DOI: 10.1074/jbc.m114.591792] [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] [Indexed: 12/21/2022] Open
Abstract
Alzheimer disease (AD) is a progressive neurodegenerative disease leading to memory loss. Numerous lines of evidence suggest that amyloid-β (Aβ), a neurotoxic peptide, initiates a cascade that results in synaptic dysfunction, neuronal death, and eventually cognitive deficits. Aβ is generated by the proteolytic processing of the amyloid precursor protein (APP), and alterations to this processing can result in Alzheimer disease. Using in vitro and in vivo models, we identified cyclopamine as a novel regulator of γ-secretase-mediated cleavage of APP. We demonstrate that cyclopamine decreases Aβ generation by altering APP retrograde trafficking. Specifically, cyclopamine treatment reduced APP-C-terminal fragment (CTF) delivery to the trans-Golgi network where γ-secretase cleavage occurs. Instead, cyclopamine redirects APP-CTFs to the lysosome. These data demonstrate that cyclopamine treatment decreases γ-secretase-mediated cleavage of APP. In addition, cyclopamine treatment decreases the rate of APP-CTF degradation. Together, our data demonstrate that cyclopamine alters APP processing and Aβ generation by inducing changes in APP subcellular trafficking and APP-CTF degradation.
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Affiliation(s)
- Anna G Vorobyeva
- From the Department of Biology, Drexel University, Philadelphia, Pennsylvania 19104 and
| | - Randall Lee
- From the Department of Biology, Drexel University, Philadelphia, Pennsylvania 19104 and
| | - Sean Miller
- From the Department of Biology, Drexel University, Philadelphia, Pennsylvania 19104 and
| | | | - Michal Sharoni
- From the Department of Biology, Drexel University, Philadelphia, Pennsylvania 19104 and
| | - Preeti J Kandelwal
- From the Department of Biology, Drexel University, Philadelphia, Pennsylvania 19104 and
| | - Felix J Kim
- the Departments of Pharmacology and Physiology
| | - Daniel R Marenda
- From the Department of Biology, Drexel University, Philadelphia, Pennsylvania 19104 and Neurobiology and Anatomy, and
| | - Aleister J Saunders
- From the Department of Biology, Drexel University, Philadelphia, Pennsylvania 19104 and Neurobiology and Anatomy, and Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102
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18
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Evidence of a novel mechanism for partial γ-secretase inhibition induced paradoxical increase in secreted amyloid β protein. PLoS One 2014; 9:e91531. [PMID: 24658363 PMCID: PMC3962361 DOI: 10.1371/journal.pone.0091531] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 02/12/2014] [Indexed: 02/02/2023] Open
Abstract
BACE1 (β-secretase) and α-secretase cleave the Alzheimer's amyloid β protein (Aβ) precursor (APP) to C-terminal fragments of 99 aa (CTFβ) and 83 aa (CTFα), respectively, which are further cleaved by γ-secretase to eventually secrete Aβ and Aα (a.k.a. P3) that terminate predominantly at residues 40 and 42. A number of γ-secretase inhibitors (GSIs), such as N-[N-(3,5-Difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT), have been developed with the goal of reducing Aβ to treat Alzheimer's disease (AD). Although most studies show that DAPT inhibits Aβ in a dose-dependent manner several studies have also detected a biphasic effect with an unexpected increase at low doses of DAPT in cell cultures, animal models and clinical trials. In this article, we confirm the increase in Aβ40 and Aβ42 in SH-SY5Y human neuroblastoma cells treated with low doses of DAPT and identify one of the mechanisms for this paradox. We studied the pathway by first demonstrating that stimulation of Aβ, a product of γ-secretase, was accompanied by a parallel increase of its substrate CTFβ, thereby demonstrating that the inhibitor was not anomalously stimulating enzyme activity at low levels. Secondly, we have demonstrated that inhibition of an Aβ degrading activity, endothelin converting enzyme (ECE), yielded more Aβ, but abolished the DAPT-induced stimulation. Finally, we have demonstrated that Aα, which is generated in the secretory pathway before endocytosis, is not subject to the DAPT-mediated stimulation. We therefore conclude that impairment of γ-secretase can paradoxically increase Aβ by transiently skirting Aβ degradation in the endosome. This study adds to the growing body of literature suggesting that preserving γ-secretase activity, rather than inhibiting it, is important for prevention of neurodegeneration.
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19
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Almenar-Queralt A, Kim SN, Benner C, Herrera CM, Kang DE, Garcia-Bassets I, Goldstein LSB. Presenilins regulate neurotrypsin gene expression and neurotrypsin-dependent agrin cleavage via cyclic AMP response element-binding protein (CREB) modulation. J Biol Chem 2013; 288:35222-36. [PMID: 24145027 DOI: 10.1074/jbc.m113.513705] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Presenilins, the catalytic components of the γ-secretase complex, are upstream regulators of multiple cellular pathways via regulation of gene transcription. However, the underlying mechanisms and the genes regulated by these pathways are poorly characterized. In this study, we identify Tequila and its mammalian ortholog Prss12 as genes negatively regulated by presenilins in Drosophila larval brains and mouse embryonic fibroblasts, respectively. Prss12 encodes the serine protease neurotrypsin, which cleaves the heparan sulfate proteoglycan agrin. Altered neurotrypsin activity causes serious synaptic and cognitive defects; despite this, the molecular processes regulating neurotrypsin expression and activity are poorly understood. Using γ-secretase drug inhibitors and presenilin mutants in mouse embryonic fibroblasts, we found that a mature γ-secretase complex was required to repress neurotrypsin expression and agrin cleavage. We also determined that PSEN1 endoproteolysis or processing of well known γ-secretase substrates was not essential for this process. At the transcriptional level, PSEN1/2 removal induced cyclic AMP response element-binding protein (CREB)/CREB-binding protein binding, accumulation of activating histone marks at the neurotrypsin promoter, and neurotrypsin transcriptional and functional up-regulation that was dependent on GSK3 activity. Upon PSEN1/2 reintroduction, this active epigenetic state was replaced by a methyl CpG-binding protein 2 (MeCP2)-containing repressive state and reduced neurotrypsin expression. Genome-wide analysis revealed hundreds of other mouse promoters in which CREB binding is similarly modulated by the presence/absence of presenilins. Our study thus identifies Tequila and neurotrypsin as new genes repressed by presenilins and reveals a novel mechanism used by presenilins to modulate CREB signaling based on controlling CREB recruitment.
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20
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Xuan Z, Barthet G, Shioi J, Xu J, Georgakopoulos A, Bruban J, Robakis NK. Presenilin-1/γ-secretase controls glutamate release, tyrosine phosphorylation, and surface expression of N-methyl-D-aspartate receptor (NMDAR) subunit GluN2B. J Biol Chem 2013; 288:30495-30501. [PMID: 24025330 DOI: 10.1074/jbc.m113.499004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Abnormally high concentrations of extracellular glutamate in the brain may cause neuronal damage via excitotoxicity. Thus, tight regulation of glutamate release is critical to neuronal function and survival. Excitotoxicity is caused mainly by overactivation of the extrasynaptic NMDA receptor (NMDAR) and results in specific cellular changes, including calcium-induced activation of calpain proteases. Here, we report that presenilin-1 (PS1) null mouse cortical neuronal cultures have increased amounts of calpain-dependent spectrin breakdown products (SBDPs) compared with WT cultures. NMDAR antagonists blocked accumulation of SBDPs, suggesting abnormal activation of this receptor in PS1 null cultures. Importantly, an increase in SBDPs was detected in cultures of at least 7 days in vitro but not in younger cultures. Conditioned medium from PS1 null neuronal cultures at 8 days in vitro contained higher levels of glutamate than medium from WT cultures and stimulated production of SBDPs when added to WT cultures. Use of glutamate reuptake inhibitors indicated that accumulation of this neurotransmitter in the media of PS1 null cultures was due to increased rates of release. PS1 null neurons showed decreased cell surface expression and phosphorylation of the GluN2B subunit of NMDAR, indicating decreased amounts of extrasynaptic NMDAR in the absence of PS1. Inhibition of γ-secretase activity in WT neurons caused changes similar to those observed in PS1 null neurons. Together, these data indicate that the PS1/γ-secretase system regulates release of glutamate, tyrosine phosphorylation, and surface expression of GluN2B-containing NMDARs.
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Affiliation(s)
- Zhao Xuan
- From the Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Gael Barthet
- From the Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Junichi Shioi
- From the Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Jindong Xu
- From the Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Anastasios Georgakopoulos
- From the Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Julien Bruban
- From the Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Nikolaos K Robakis
- From the Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029.
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21
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Nalivaeva NN, Turner AJ. The amyloid precursor protein: a biochemical enigma in brain development, function and disease. FEBS Lett 2013; 587:2046-54. [PMID: 23684647 DOI: 10.1016/j.febslet.2013.05.010] [Citation(s) in RCA: 170] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 05/06/2013] [Accepted: 05/06/2013] [Indexed: 12/11/2022]
Abstract
For 20 years the amyloid cascade hypothesis of Alzheimer disease (AD) has placed the amyloid-β peptide (Aβ), formed from the amyloid precursor protein (APP), centre stage in the process of neurodegeneration. However, no new therapeutic agents have reached the clinic through exploitation of the hypothesis. The APP metabolites, including Aβ, generated by its proteolytic processing, have distinct physiological functions. In particular, the cleaved intracellular domain of APP (AICD) regulates expression of several genes, including APP itself, the β-secretase BACE-1 and the Aβ-degrading enzyme, neprilysin and this transcriptional regulation involves direct promoter binding of AICD. Of the three major splice isoforms of APP (APP695, APP751, APP770), APP695 is the predominant neuronal form, from which Aβ and transcriptionally-active AICD are preferentially generated by selective processing through the amyloidogenic pathway. Despite intensive research, the normal functions of the APP isoforms remain an enigma. APP plays an important role in brain development, memory and synaptic plasticity and secreted forms of APP are neuroprotective. A fuller understanding of the physiological and pathological actions of APP and its metabolic and gene regulatory network could provide new therapeutic opportunities in neurodegeneration, including AD.
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Affiliation(s)
- Natalia N Nalivaeva
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
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22
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Robakis NK. Cell signaling abnormalities may drive neurodegeneration in familial Alzheimer disease. Neurochem Res 2013; 39:570-5. [PMID: 23436150 DOI: 10.1007/s11064-013-1003-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Revised: 02/04/2013] [Accepted: 02/11/2013] [Indexed: 11/28/2022]
Abstract
Presenilins (PSs) are catalytic components of the γ-secretase complex that produces Aβ peptides. Substrates of γ-secretase are membrane-bound protein fragments deriving from the cleavage of extracellular sequence of cell surface proteins. APP-derived γ-secretase substrates are cleaved at gamma (γ) sites to produce Aβ while cleavage at the epsilon (ε) site produces AICD proposed to function in transcription. In addition to APP, γ-secretase promotes the ε-cleavage of a large number of cell surface proteins producing cytosolic peptides shown to function in cell signaling. A common hypothesis suggests that Alzheimer's disease (AD) is caused by Aβ peptides or their products. Treatment of patients with inhibitors of Aβ production however, showed no therapeutic benefits while inducing cytotoxicity. Similarly, treatments with anti-Aβ antibodies yielded disappointing results. Importantly, recent evidence shows that PS familial AD (FAD) mutations cause a loss of γ-secretase cleavage activity at ε site of substrates thus inhibiting production of biologically important cell signaling peptides while promoting accumulation of membrane-bound cytotoxic substrates. These data support a hypothesis that FAD mutations may increase neurotoxicity by inhibiting the γ-secretase-catalyzed ε cleavage of substrates thus interfering with cell signaling while also promoting accumulation of cytotoxic peptides. Similar mechanisms may explain γ-secretase inhibitor-associated toxicities observed in clinical trials. Here we discuss evidence that FAD neurodegeneration may be caused by loss of γ-secretase cleavage function at ε sites of substrates.
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Affiliation(s)
- Nikolaos K Robakis
- Departments of Psychiatry and Neuroscience, Mount Sinai School of Medicine, New York University, One Gustave Levy Pl., Box 1229, New York, NY, 10029, USA,
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23
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Ortega F, Stott J, Visser SAG, Bendtsen C. Interplay between α-, β-, and γ-secretases determines biphasic amyloid-β protein level in the presence of a γ-secretase inhibitor. J Biol Chem 2012; 288:785-92. [PMID: 23152503 PMCID: PMC3543028 DOI: 10.1074/jbc.m112.419135] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Amyloid-β (Aβ) is produced by the consecutive cleavage of amyloid precursor protein (APP) first by β-secretase, generating C99, and then by γ-secretase. APP is also cleaved by α-secretase. It is hypothesized that reducing the production of Aβ in the brain may slow the progression of Alzheimer disease. Therefore, different γ-secretase inhibitors have been developed to reduce Aβ production. Paradoxically, it has been shown that low to moderate inhibitor concentrations cause a rise in Aβ production in different cell lines, in different animal models, and also in humans. A mechanistic understanding of the Aβ rise remains elusive. Here, a minimal mathematical model has been developed that quantitatively describes the Aβ dynamics in cell lines that exhibit the rise as well as in cell lines that do not. The model includes steps of APP processing through both the so-called amyloidogenic pathway and the so-called non-amyloidogenic pathway. It is shown that the cross-talk between these two pathways accounts for the increase in Aβ production in response to inhibitor, i.e. an increase in C99 will inhibit the non-amyloidogenic pathway, redirecting APP to be cleaved by β-secretase, leading to an additional increase in C99 that overcomes the loss in γ-secretase activity. With a minor extension, the model also describes plasma Aβ profiles observed in humans upon dosing with a γ-secretase inhibitor. In conclusion, this mechanistic model rationalizes a series of experimental results that spans from in vitro to in vivo and to humans. This has important implications for the development of drugs targeting Aβ production in Alzheimer disease.
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Affiliation(s)
- Fernando Ortega
- Computational Biology, Discovery Sciences, AstraZeneca, Alderley Park, Macclesfield SK10 4TG, United Kingdom
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24
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Gael B, Georgakopoulos A, Robakis NK. Cellular mechanisms of γ-secretase substrate selection, processing and toxicity. Prog Neurobiol 2012; 98:166-75. [PMID: 22622135 PMCID: PMC3404154 DOI: 10.1016/j.pneurobio.2012.05.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 04/12/2012] [Accepted: 05/08/2012] [Indexed: 01/04/2023]
Abstract
Presenilins (PSs) are catalytic components of the γ-secretase proteolytic complexes that produce Aβ and cell signaling peptides. γ-Secretase substrates are mostly membrane-bound peptides derived following proteolytic cleavage of the extracellular domain of type I transmembrane proteins. Recent work reveals that γ-secretase substrate processing is regulated by proteins termed γ-secretase substrate recruiting factors (γSSRFs) that bridge substrates to γ-secretase complexes. These factors constitute novel targets for pharmacological control of specific γ-secretase products, such as Aβ and signaling peptides. PS familial Alzheimer's disease (FAD) mutants cause a loss of γ-secretase cleavage function at epsilon sites of substrates thus inhibiting production of cell signaling peptides while promoting accumulation of uncleaved toxic substrates. Importantly, γ-secretase inhibitors may cause toxicity in vivo by similar mechanisms. Here we review novel mechanisms that control γ-secretase substrate selection and cleavage and examine their relevance to AD.
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Affiliation(s)
- Barthet Gael
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Mount Sinai School of Medicine, New York, NY 10029
| | - Anastasios Georgakopoulos
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Mount Sinai School of Medicine, New York, NY 10029
| | - Nikolaos K. Robakis
- Center for Molecular Biology and Genetics of Neurodegeneration, Departments of Psychiatry and Neuroscience, Mount Sinai School of Medicine, New York, NY 10029
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25
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Oikawa N, Goto M, Ikeda K, Taguchi R, Yanagisawa K. The γ-secretase inhibitor DAPT increases the levels of gangliosides at neuritic terminals of differentiating PC12 cells. Neurosci Lett 2012; 525:49-53. [PMID: 22867970 DOI: 10.1016/j.neulet.2012.07.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 06/13/2012] [Accepted: 07/12/2012] [Indexed: 11/17/2022]
Abstract
Mutations in presenilins are the major cause of early onset familial Alzheimer disease. It has recently been argued that clinical presenilin mutations work as loss-of-function but not toxic gain-of-function. To investigate whether presenilins are involved in the regulation of the distribution of neuronal membrane lipids, we treated neuronally differentiated PC12 cells with DAPT, an inhibitor of presenilin-dependent γ-secretase, and performed lipid analyses of neuritic terminals, which is an initial site of Aβ deposition in brains, using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) in combination with multiple reaction monitoring (MRM). With DAPT treatment, levels of sphingomyelin, phosphatidylcholine, and cholesterol remained unchanged. However, DAPT treatment increased the ganglioside levels in PC12 neuritic terminals. Together with a previous finding that accumulation of gangliosides at neuritic terminals facilitates Aβ assembly and deposition, the present data suggest that the loss-of-function of presenilins, i.e., a decrease in γ-secretase activity, has an impact on neuronal membrane architecture in a way that eventually exacerbates Alzheimer pathology.
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Affiliation(s)
- Naoto Oikawa
- Department of Drug Discovery, Center for Development of Advanced Medicine for Dementia, Research Institute, National Center for Geriatrics and Gerontology, Obu 474-8522, Japan
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