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Olesen MA, Quintanilla RA. Pathological Impact of Tau Proteolytical Process on Neuronal and Mitochondrial Function: a Crucial Role in Alzheimer's Disease. Mol Neurobiol 2023; 60:5691-5707. [PMID: 37332018 DOI: 10.1007/s12035-023-03434-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 06/06/2023] [Indexed: 06/20/2023]
Abstract
Tau protein plays a pivotal role in the central nervous system (CNS), participating in microtubule stability, axonal transport, and synaptic communication. Research interest has focused on studying the role of post-translational tau modifications in mitochondrial failure, oxidative damage, and synaptic impairment in Alzheimer's disease (AD). Soluble tau forms produced by its pathological cleaved induced by caspases could lead to neuronal injury contributing to oxidative damage and cognitive decline in AD. For example, the presence of tau cleaved by caspase-3 has been suggested as a relevant factor in AD and is considered a previous event before neurofibrillary tangles (NFTs) formation.Interestingly, we and others have shown that caspase-cleaved tau in N- or C- terminal sites induce mitochondrial bioenergetics defects, axonal transport impairment, neuronal injury, and cognitive decline in neuronal cells and murine models. All these abnormalities are considered relevant in the early neurodegenerative manifestations such as memory and cognitive failure reported in AD. Therefore, in this review, we will discuss for the first time the importance of truncated tau by caspases activation in the pathogenesis of AD and how its negative actions could impact neuronal function.
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Affiliation(s)
- Margrethe A Olesen
- Laboratory of Neurodegenerative Diseases, Facultad de Ciencias de La Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, El Llano Subercaseaux 2801, 5to Piso, San Miguel, 8910060, Santiago, Chile
| | - Rodrigo A Quintanilla
- Laboratory of Neurodegenerative Diseases, Facultad de Ciencias de La Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, El Llano Subercaseaux 2801, 5to Piso, San Miguel, 8910060, Santiago, Chile.
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Choi SB, Kwon S, Kim JH, Ahn NH, Lee JH, Yang SH. The Molecular Mechanisms of Neuroinflammation in Alzheimer's Disease, the Consequence of Neural Cell Death. Int J Mol Sci 2023; 24:11757. [PMID: 37511515 PMCID: PMC10380735 DOI: 10.3390/ijms241411757] [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: 06/20/2023] [Revised: 07/17/2023] [Accepted: 07/20/2023] [Indexed: 07/30/2023] Open
Abstract
Alzheimer's disease (AD) is accompanied by neural cell loss and memory deficit. Neural cell death, occurring via apoptosis and autophagy, is widely observed in the AD brain in addition to neuroinflammation mediated by necroptosis and the NLRP3 inflammasome. Neurotoxicity induced by amyloid-beta (Aβ) and tau aggregates leads to excessive neural cell death and neuroinflammation in the AD brain. During AD progression, uncontrolled neural cell death results in the dysregulation of cellular activity and synaptic function. Apoptosis mediated by pro-apoptotic caspases, autophagy regulated by autophagy-related proteins, and necroptosis controlled by the RIPK/MLKL axis are representative of neural cell death occurred during AD. Necroptosis causes the release of cellular components, contributing to the pro-inflammatory environment in the AD brain. Inordinately high levels of neural cell death and pro-inflammatory events lead to the production of pro-inflammatory cytokines and feed-forward hyper neuroinflammation. Thus, neural cell death and neuroinflammation cause synaptic dysfunction and memory deficits in the AD brain. In this review, we briefly introduce the mechanisms of neural cell death and neuroinflammation observed in the AD brain. Combined with a typical strategy for targeting Aβ and tau, regulation of neural cell death and neuroinflammation may be effective for the amelioration of AD pathologies.
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Affiliation(s)
- Su-Bin Choi
- Department of Biomedical Engineering, College of Life Science and Biotechnology, Dongguk University, Seoul 04620, Republic of Korea
| | - Sehee Kwon
- Department of Biomedical Engineering, College of Life Science and Biotechnology, Dongguk University, Seoul 04620, Republic of Korea
| | - Ji-Hye Kim
- Department of Biomedical Engineering, College of Life Science and Biotechnology, Dongguk University, Seoul 04620, Republic of Korea
| | - Na-Hyun Ahn
- Department of Biomedical Engineering, College of Life Science and Biotechnology, Dongguk University, Seoul 04620, Republic of Korea
| | - Joo-Hee Lee
- Department of Biomedical Engineering, College of Life Science and Biotechnology, Dongguk University, Seoul 04620, Republic of Korea
| | - Seung-Hoon Yang
- Department of Biomedical Engineering, College of Life Science and Biotechnology, Dongguk University, Seoul 04620, Republic of Korea
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Gao X, Li S, Liu X, Cong C, Zhao L, Liu H, Xu L. Neuroprotective effects of Tiaogeng decoction against H 2O 2-induced oxidative injury and apoptosis in PC12 cells via Nrf2 and JNK signaling pathways. JOURNAL OF ETHNOPHARMACOLOGY 2021; 279:114379. [PMID: 34216727 DOI: 10.1016/j.jep.2021.114379] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/22/2021] [Accepted: 06/26/2021] [Indexed: 06/13/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Tiaogeng decoction (TGD), a mixture of 10 traditional Chinese herbs, has been used clinically for over 30 years in treating menopause-related symptoms such as cognitive changes, mood disorders, vasomotor symptoms, and sleep disorders. These central nervous system symptoms are closely associated with declined ovarian function, which dramatically increases the risk of neurodegenerative disease. Previous studies revealed that TGD may have anti-oxidative and anti-apoptotic properties, potentially preventing neurodegenerative conditions; however, the underlying pharmacological mechanism remains unclear. AIM OF THE STUDY This study aimed to examine whether TGD could activate the Nrf2 and C-Jun N-terminal kinase (JNK) signaling pathways to effectively reduce oxidative injury and apoptosis in PC12 cells and elucidate the mechanism by which this medicine may prevent neurodegenerative disease. MATERIALS AND METHODS PC12 cells were exposed to different concentrations of TGD (125, 250, 500 μg/mL) and H2O2 (150 μM). 17β-estradiol (0.05 μg/mL) was used as the positive control. A cell counting kit-8 (CCK-8) and a lactate dehydrogenase (LDH) assay were used to detect cell viability and cytotoxicity, while Hoechst and flow cytometry were performed to evaluate apoptosis levels. Mitochondrial function was assessed by measuring mitochondrial membrane potential (MMP), and superoxide dismutase (SOD), and reactive oxygen species (ROS) levels were used to measure oxidative stress (OS). Western blot analysis was used to identify the levels of Nrf2, phospho-JNK (p-JNK), phospho-mitogen-activated protein kinase kinase 7 (p-MKK7), Kelch-like ECH-associated protein 1 (Keap1), heme oxygenase-1 (HO-1), Caspase3 (Casp3), Caspase9 (Casp9), Bax, and Bcl-2 proteins. Moreover, JNK agonist anisomycin and Nrf2 inhibitor ML385 were used to validate pathways. RESULTS TGD pretreatment significantly alleviated H2O2-induced cytotoxicity, apoptosis, MMP, and OS levels. H2O2 stimulated the activation of Nrf2 and JNK signaling pathways, but TGD increased the extent of Nrf2 antioxidant activation, decreased the activation of JNK, and eventually reversed the H2O2-induced protein expression of p-MKK7, Keap1, HO-1, Cleaved Caspase3 (CL-Casp3), Cleaved Caspase9 (CL-Casp9), Bax, and Bcl-2. CONCLUSIONS This study's findings suggest that TGD may attenuate oxidative injury and apoptosis via the Nrf2 and JNK signaling pathways, making it a potential therapeutic candidate for neurodegenerative diseases.
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Affiliation(s)
- Xianwei Gao
- Department of Gynecology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China.
| | - Shengnan Li
- Department of Gynecology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China.
| | - Xiaofei Liu
- Department of Gynecology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China.
| | - Chao Cong
- Department of Gynecology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China.
| | - Li Zhao
- Department of Gynecology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China.
| | - Huicong Liu
- Department of Gynecology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China.
| | - Lianwei Xu
- Department of Gynecology, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China.
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Qin C, Li Y, Wang K. Functional Mechanism of Bone Marrow-Derived Mesenchymal Stem Cells in the Treatment of Animal Models with Alzheimer's Disease: Inhibition of Neuroinflammation. J Inflamm Res 2021; 14:4761-4775. [PMID: 34566422 PMCID: PMC8456430 DOI: 10.2147/jir.s327538] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 08/18/2021] [Indexed: 12/27/2022] Open
Abstract
The transplantation of bone marrow-derived mesenchymal stem cells (BMMSCs) alleviates neuropathology and improves cognitive deficits in animal models with Alzheimer’s disease. However, the underlying mechanisms remain to be determined. Available data demonstrate transplanted BMMSCs can inhibit neuroinflammation, which may be related to microglial M1/M2 polarization and is regulated by the secretion of autocrine and paracrine cytokines. BMMSCs also mitigate Aβ plaques and Tau tangles in the brain, which may be associated with the recruitment of peripheral blood monocytes and the subsequent comprehensive effects. The therapeutic effects of stem cells involve potential mechanisms such as immunomodulation, apoptosis, and proliferation. BMMSC-mediated functional reconstruction through dynamic remodeling develops a novel balance. Herein, present review recapitulates the molecular basis of BMMSC-assisted biological processes and summarizes the possible mechanisms related to the interaction between BMMSCs and microglia. The transplanted BMMSCs can suppress neuroinflammation that plays a key role in the pathogenesis of Alzheimer’s disease.
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Affiliation(s)
- Chuan Qin
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences & Comparative Medical Center, Peking Union Medical College, Beijing, 100021, People's Republic of China
| | - Yongning Li
- Department of International Medical Service & Department of Neurosurgery, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100730, People's Republic of China
| | - Kewei Wang
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences & Comparative Medical Center, Peking Union Medical College, Beijing, 100021, People's Republic of China
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Wang Y, Wang M, Fan K, Li T, Yan T, Wu B, Bi K, Jia Y. Protective effects of Alpinae Oxyphyllae Fructus extracts on lipopolysaccharide-induced animal model of Alzheimer's disease. JOURNAL OF ETHNOPHARMACOLOGY 2018; 217:98-106. [PMID: 29447949 DOI: 10.1016/j.jep.2018.02.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Revised: 02/09/2018] [Accepted: 02/10/2018] [Indexed: 06/08/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Alpinae Oxyphyllae Fructus (AOF) with warming and tonifying the kidney and spleen, anti-salivation, anti-polyuria and anti-diarrhea functions is the dried ripe fruits of Alpinia oxyphylla Miq. (Zingiberaceae). As a traditional Chinese medicine, its application history is very long. AIMS OF THE STUDY The purpose of our study is to investigate the effects of different solvent extracts from AOF on lipopolysaccharide (LPS)-induced animal model of Alzheimer's disease (AD) to elucidate the traditional medical theories with modern pharmacological methods and provide a reference for further clarifying its active components and mechanisms. MATERIALS AND METHODS The method of stepwise screening was adopted in this paper. The animals were divided into 9 groups, including control (CT) group, model (MD) group, donepezil (DPZ) group, total extract (TT) group, petroleum ether extract (PE) group, chloroform extract (CF) group, ethyl acetate extract (EA) group, n-butanol extract (NB) group and water extract (WT) group. The anti-amnesic effects of different solvent extracts from AOF were measured in LPS-induced memory deficits mice by Y maze test and Morris water maze (MWM) test. Hematoxylin eosin (HE) staining was applied to observe pathological changes in hippocampus and cerebral cortex tissue of different groups. Biochemical indicators including ionized calcium-binding adaptor molecule 1 (IBA-1), interleukin beta 1 (IL-1β), Aβ1-42 and hyperphosphorylated tau proteins (p-tau) in hippocampus and cortex after treatment with LPS were measured according to the manufacturer's instructions of ELISA kits. HPLC was used to evaluate the major components of different extracts. RESULTS It was found that successive intragastric administration of AOF (360 mg/kg) extracts for 14 days showed different degrees of improvement on LPS-induced AD model as measured by Y-maze test, Morris water maze test, and Histopathological examination. Moreover, the results of ELISA suggested petroleum ether (PE) extracts were worth recommending for inhibiting the high level of IBA-1, IL-1β, Aβ1-42 and p-tau in hippocampus and cortex after treatment with LPS. CONCLUSIONS The present study demonstrated for the first time that AOF attenuated LPS-induced learning and memory impairment, which may be associated with its inhibitory effect on neuroinflammation, amyloids-β (Aβ) deposition and p-tau. This research provided a theoretical basis for elucidating the traditional theory of AOF, and was also the stepping stone to the next step.
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Affiliation(s)
- Yunlong Wang
- School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang 110016, China
| | - Mengshi Wang
- School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang 110016, China
| | - Kaiyue Fan
- School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang 110016, China
| | - Tongde Li
- School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang 110016, China
| | - Tingxu Yan
- School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang 110016, China
| | - Bo Wu
- School of Functional Food and Wine, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang 110016, China
| | - Kaishun Bi
- School of Pharmacy, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang 110016, China
| | - Ying Jia
- School of Functional Food and Wine, Shenyang Pharmaceutical University, Wenhua Road 103, Shenyang 110016, China.
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Kim SI, Lee HJ, Kim SS, Kwon YS, Chun W. Sequestration of sorcin by aberrant forms of tau results in the defective calcium homeostasis. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2016; 20:387-97. [PMID: 27382355 PMCID: PMC4930907 DOI: 10.4196/kjpp.2016.20.4.387] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 03/23/2016] [Accepted: 04/09/2016] [Indexed: 11/15/2022]
Abstract
Neurofi brillary tangles (NFTs) of microtubule-associated protein tau are a pathological hallmark of Alzheimer's disease (AD). Endoplasmic reticulum (ER) stress has been known to be involved in the pathogenesis of AD. However, the exact role of ER stress in tau pathology has not yet been clearly elucidated. In present study, the possible relationship between tau pathology and ER stress was examined in terms of sorcin, which is a calcium binding protein and plays an important role in calcium homeostasis. Our previous yeast two hybrid study showed that sorcin is a novel tau interacting protein. Caspase-3-cleaved tau (T4C3) showed significantly increased tau-sorcin interaction compared to wild type tau (T4). Thapsigargin-induced ER stress and co-expression of constitutively active GSK3β (GSK3β-S9A) also exhibited significantly increased tau-sorcin interactions. T4C3-expressing cells showed potentiated thapsigargin-induced apoptosis and disruption of intracellular calcium homeostasis compared to T4-expressing cells. Overexpression of sorcin signifi cantly attenuated thapsigargin-induced apoptosis and disruption of calcium homeostasis. In contrary, siRNA-mediated knock-down of sorcin showed significantly increased thapsigargin-induced apoptosis and disruption of calcium homeostasis. These data strongly suggest that sequestration of sorcin by aberrant forms of tau compromises the function of sorcin, such as calcium homeostasis and cellular resistance by ER stress, which may consequently result in the contribution to the progression of AD.
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Affiliation(s)
- Song-In Kim
- Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea
| | - Hee Jae Lee
- Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea
| | - Sung-Soo Kim
- Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea
| | - Yong-Soo Kwon
- School of Pharmacy, Kangwon National University, Chuncheon 24341, Korea
| | - Wanjoo Chun
- Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea
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Involvement of caspase-3/PTEN signaling pathway in isoflurane-induced decrease of self-renewal capacity of hippocampal neural precursor cells. Brain Res 2015; 1625:275-86. [PMID: 26367448 DOI: 10.1016/j.brainres.2015.08.047] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 08/23/2015] [Accepted: 08/24/2015] [Indexed: 01/14/2023]
Abstract
Evidence has shown that children exposed to isoflurane anesthesia in early childhood display long-term cognitive abnormalities, and decreased self-renewal capacity of hippocampal neural precursor cells (NPCs), which are associated with cognition impairment. Caspase-3 has long been considered as a mediator in isoflurane-induced neuroapoptosis. However, accumulating data indicate that caspase-3 also plays a non-apoptotic negative regulatory role in NPCs self-renewal. In this study we used in vitro NPC cultures to test whether caspase-3 and its downstream signaling effectors were involved in isoflurane-induced impairment of the self-renewal capacity of hippocampal NPCs. We showed that isoflurane exposure induced a decrease in the self-renewal capacity of hippocampal NPCs by decreasing proliferation and increasing neuronal differentiation. Furthermore, we found that isoflurane exposure significantly increased the levels of active caspase-3 and decreased the levels of phospho-PTEN under both proliferation and differentiation conditions. Inhibition of either caspase-3 with Z-DEVD-fmk or PTEN with BPV (phen) in NPCs, attenuated the isoflurane-induced decrease of their proliferation and increase of neuronal differentiation. Application of Z-DEVD-fmk also attenuated isoflurane-induced decrease in phospho-PTEN expression. Taken together, our in vitro results reveal a previously uncharacterized involvement of caspase-3/PTEN signaling in the isoflurane-induced impairment of NPCs self-renewal, and contribute to the identification of novel targets for maintaining NPCs self-renewal in isoflurane-induced cognitive dysfunction.
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Ahmadian SS, Rezvanian A, Peterson M, Weintraub S, Bigio EH, Mesulam MM, Geula C. Loss of calbindin-D28K is associated with the full range of tangle pathology within basal forebrain cholinergic neurons in Alzheimer's disease. Neurobiol Aging 2015; 36:3163-3170. [PMID: 26417681 DOI: 10.1016/j.neurobiolaging.2015.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 09/01/2015] [Accepted: 09/02/2015] [Indexed: 01/21/2023]
Abstract
Basal forebrain cholinergic neurons (BFCN) are selectively vulnerable in Alzheimer's disease (AD). We have shown that most of the BFCN in the human brain contain the calcium-binding protein calbindin-D28K (CB), a large proportion lose their CB in the course of normal aging, and the BFCN which degenerate in AD lack CB. Here, we investigated the relationship between CB in the BFCN and the process of tangle formation in AD using antibodies to tau epitopes that appear early, intermediate or late in the process of tangle formation. Very small percentages (0%-3.7%) of CB-positive BFCN contained pretangles and/or tangles, and very small percentages (0%-5%) of the total BFCN pretangles and/or tangles were in CB-immunoreactive neurons. The number of CB-positive BFCN which contained tau immunoreactivity was highest for the early epitope and lower for intermediate epitopes. A late appearing epitope was absent from CB-positive BFCN. Age-related loss of CB appears to coincide with tangle formation in the BFCN and is associated with the full range of tau pathology, including late appearing epitopes.
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Affiliation(s)
- Saman S Ahmadian
- Laboratory for Cognitive and Molecular Morphometry, Cognitive Neurology and Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago IL, USA
| | - Aras Rezvanian
- Laboratory for Cognitive and Molecular Morphometry, Cognitive Neurology and Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago IL, USA
| | - Melanie Peterson
- Laboratory for Cognitive and Molecular Morphometry, Cognitive Neurology and Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago IL, USA
| | - Sandra Weintraub
- Laboratory for Cognitive and Molecular Morphometry, Cognitive Neurology and Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago IL, USA
| | - Eileen H Bigio
- Laboratory for Cognitive and Molecular Morphometry, Cognitive Neurology and Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago IL, USA
| | - Marek-Marsel Mesulam
- Laboratory for Cognitive and Molecular Morphometry, Cognitive Neurology and Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago IL, USA
| | - Changiz Geula
- Laboratory for Cognitive and Molecular Morphometry, Cognitive Neurology and Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago IL, USA.
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Yun N, Lee YM, Kim C, Shibayama H, Tanimura A, Hamanaka Y, Kanakura Y, Park IS, Jo A, Shin JH, Ju C, Kim WK, Oh YJ. Anamorsin, a novel caspase-3 substrate in neurodegeneration. J Biol Chem 2014; 289:22183-95. [PMID: 24973211 PMCID: PMC4139231 DOI: 10.1074/jbc.m114.552679] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 06/24/2014] [Indexed: 11/06/2022] Open
Abstract
Activated caspases play a central role in the execution of apoptosis by cleaving endogenous substrates. Here, we developed a high throughput screening method to identify novel substrates for caspase-3 in a neuronal cell line. Critical steps in our strategy consist of two-dimensional electrophoresis-based protein separation and in vitro caspase-3 incubation of immobilized proteins to sort out direct substrates. Among 46 putative substrates identified in MN9D neuronal cells, we further evaluated whether caspase-3-mediated cleavage of anamorsin, a recently recognized cell death-defying factor in hematopoiesis, is a general feature of apoptosis. In vitro and cell-based cleavage assays indicated that anamorsin was specifically cleaved by caspase-3 but not by other caspases, generating 25- and 10-kDa fragments. Thus, in apoptosis of neuronal and non-neuronal cells induced by various stimuli including staurosporine, etoposide, or 6-hydroxydopamine, the cleavage of anamorsin was found to be blocked in the presence of caspase inhibitor. Among four tetrapeptide consensus DXXD motifs existing in anamorsin, we mapped a specific cleavage site for caspase-3 at DSVD(209)↓L. Intriguingly, the 25-kDa cleaved fragment of anamorsin was also detected in post-mortem brains of Alzheimer and Parkinson disease patients. Although the RNA interference-mediated knockdown of anamorsin rendered neuronal cells more vulnerable to staurosporine treatment, reintroduction of full-length anamorsin into an anamorsin knock-out stromal cell line made cells resistant to staurosporine-induced caspase activation, indicating the antiapoptotic function of anamorsin. Taken together, our approach seems to be effective to identify novel substrates for caspases and has the potential to provide meaningful insights into newly identified substrates involved in neurodegenerative processes.
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Affiliation(s)
- Nuri Yun
- From the Department of Systems Biology, Yonsei University College of Life Science and Biotechnology, Seoul 120-749, Korea
| | - Young Mook Lee
- From the Department of Systems Biology, Yonsei University College of Life Science and Biotechnology, Seoul 120-749, Korea
| | - Chiho Kim
- From the Department of Systems Biology, Yonsei University College of Life Science and Biotechnology, Seoul 120-749, Korea
| | - Hirohiko Shibayama
- Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Akira Tanimura
- Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Yuri Hamanaka
- Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Yuzuru Kanakura
- Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Il-Seon Park
- Department of Cellular and Molecular Medicine, College of Medicine, Chosun University, Gwangju 501-759, Korea
| | - Areum Jo
- Division of Pharmacology, Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Gyeonggi-do, Korea, and
| | - Joo-Ho Shin
- Division of Pharmacology, Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Gyeonggi-do, Korea, and
| | - Chung Ju
- Department of Neuroscience, College of Medicine, Korea University, Seoul 136-705, Korea
| | - Won-Ki Kim
- Department of Neuroscience, College of Medicine, Korea University, Seoul 136-705, Korea
| | - Young J Oh
- From the Department of Systems Biology, Yonsei University College of Life Science and Biotechnology, Seoul 120-749, Korea,
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LeBlanc AC. Caspase-6 as a novel early target in the treatment of Alzheimer's disease. Eur J Neurosci 2013; 37:2005-18. [DOI: 10.1111/ejn.12250] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 04/01/2013] [Accepted: 04/06/2013] [Indexed: 12/16/2022]
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Liu J, Yan X, Li L, Zhu Y, Qin K, Zhou L, Sun D, Zhang X, Ye R, Zhao G. Ginsennoside rd attenuates cognitive dysfunction in a rat model of Alzheimer's disease. Neurochem Res 2012; 37:2738-47. [PMID: 22903450 DOI: 10.1007/s11064-012-0866-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 07/16/2012] [Accepted: 08/01/2012] [Indexed: 01/02/2023]
Abstract
Alzheimer's disease is a neurodegenerative disease characterized by the production of β-amyloid proteins and hyperphosphorylation of tau protein. Inflammation and apoptotic severity were highly correlated with earlier age at onset of Alzheimer's disease and were also associated with cognitive decline. This study aims to examine whether the traditional Chinese medicine ginsennoside Rd could prevent cognitive deficit and take neuroprotective effects in β-amyloid peptide 1-40-induced rat model of Alzheimer's disease. To produce Alzheimer's disease animal model, aggregated β-amyloid peptide 1-40 injected into hippocampus bilaterally. Ginsennoside Rd protected their cognitive impairment and improved their memory function by daily intraperitoneal injection for 30 days consecutively. In addition, ginsennoside Rd alleviated the inflammation induced by β-amyloid peptide 1-40. Furthermore, ginsennoside Rd played a role in the down-regulation of caspase-3 proteins and reduced the apoptosis that normally followed β-amyloid peptide 1-40 injection. The results of this study showed that the pretreatment of ginsennoside Rd had neuroprotective effects in β-amyloid peptide 1-40-induced AD model rat.
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Affiliation(s)
- Juanfang Liu
- Department of Neurology, Xijing Hospital, Fourth Military Medical University, 127 West Changle Road, Xi'an 710032, People's Republic of China
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Lee JH, Won SM, Suh J, Son SJ, Moon GJ, Park UJ, Gwag BJ. Induction of the unfolded protein response and cell death pathway in Alzheimer's disease, but not in aged Tg2576 mice. Exp Mol Med 2010; 42:386-94. [PMID: 20368688 DOI: 10.3858/emm.2010.42.5.040] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
The endoplasmic reticulum (ER) stress results from disrupted protein folding triggered by protein mutation or oxidation, reduced proteasome activity, and altered Ca2+ homeostasis. ER stress is accompanied by activation of the unfolded protein response (UPR) and cell death pathway. We examined if the UPR and cell death pathway would be activated in Alzheimer's disease (AD). RT-PCR experiments revealed increased splicing of X-box binding protein-1 (XBP-1), an UPR transcription factor, in AD compared with age-matched control. Among target genes of XBP-1, expression of protein disulfide isomerase (PDI), but not glucose-regulated protein 78 (GRP78), was increased in AD, suggesting disturbed activation of the UPR in AD. C/EBP homologous protein (CHOP), caspase-3, caspase-4, and caspase-12, downstream mediators of cell death pathway, were activated in AD. Neither the UPR nor cell death pathway was induced in aged Tg2576 mice, a transgenic mouse model of Alzheimer's disease that reveals both plaque pathology and some cognitive deficits. The present study suggests that disturbed induction of the UPR and activation of the pro-apoptotic proteins contribute to neuropathological process in AD irrespective of amyloid beta and senile plaque.
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Affiliation(s)
- Jin Hwan Lee
- Department of Neuroscience, Ajou University School of Medicine, Suwon 442-749, Korea
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13
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Bulat N, Widmann C. Caspase substrates and neurodegenerative diseases. Brain Res Bull 2009; 80:251-67. [DOI: 10.1016/j.brainresbull.2009.07.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Revised: 07/08/2009] [Accepted: 07/08/2009] [Indexed: 02/08/2023]
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14
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Mondragón-Rodríguez S, Basurto-Islas G, Binder LI, García-Sierra F. Conformational changes and cleavage; are these responsible for the tau aggregation in Alzheimer’s disease? FUTURE NEUROLOGY 2009. [DOI: 10.2217/14796708.4.1.39] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In the past, post-translational modifications of tau protein, such as phosphorylation, cleavage and conformational changes, have long been implicated in the pathogenesis of Alzheimer’s disease. Unfortunately, the accurate role and relationship between these pathological modifications during tau aggregation remains under extensive study. We had proposed a chronological model of tau pathological processing during Alzheimer´s disease, in which phosphorylation and cleavage could lead to conformational changes causing aggregation and therefore, cell toxicity. We discuss this issue and review in vitro and in situ evidence that supports the relevance of tau modifications that cause its pathological conformations and toxic aggregation. Thus, we offer a brief discussion regarding conformational change and cleavage as future clinical targets.
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Affiliation(s)
- Siddhartha Mondragón-Rodríguez
- Department of Cell Biology, Center of Research & Advanced Studies of the National Politechnical Institute Av., Instituto Politecnico Nacional 2508, CP 07360, Mexico City, Mexico
| | - Gustavo Basurto-Islas
- Department of Cell Biology, Center of Research & Advanced Studies of the National Politechnical Institute Av., Instituto Politecnico Nacional 2508, CP 07360, Mexico City, Mexico
| | - Lester I Binder
- Department of Cell & Molecular Biology, Northwestern University Medical School, W129, Tarry 8-754, 303 E Chicago Av., Chicago, IL 60611, USA
| | - Francisco García-Sierra
- Department of Cell Biology, Center of Research & Advanced Studies of the National Politechnical Institute, Av. Instituto Politecnico Nacional 2508, CP 07360, Mexico City, Mexico
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15
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Accumulation of aspartic acid421- and glutamic acid391-cleaved tau in neurofibrillary tangles correlates with progression in Alzheimer disease. J Neuropathol Exp Neurol 2008; 67:470-83. [PMID: 18431250 DOI: 10.1097/nen.0b013e31817275c7] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Truncations of tau protein at aspartic acid421 (D421) and glutamic acid391 (E391) residues are associated with neurofibrillary tangles (NFTs) in the brains of Alzheimer disease (AD) patients. Using immunohistochemistry with antibodies to D421- and E391-truncated tau (Tau-C3 and MN423, respectively), we correlated the presence of NFTs composed of these truncated tau proteins with clinical and neuropathologic parameters in 17 AD and 23 non-AD control brains. The densities of NFTs composed of D421- or E391-truncated tau correlated with clinical dementia index and Braak staging in AD. Glutamic acid391 tau truncation was prominent in the entorhinal cortex, whereas D421 truncation was prominent in the subiculum, suggesting that NFTs composed of either D421- or E391-truncated tau may be formed mutually exclusively in these areas. Both truncations were associated with the prevalence of the apolipoprotein E epsilon4 allele. By double labeling, intact tau in NFTs was commonly associated with D421-cleaved tau but not with E391-truncated tau; D421-cleaved tau was never associated with E391-truncated tau. These results indicate that tau is not randomly proteolyzed at different domains, and that proteolysis occurs sequentially from the C-terminus to inner regions of tau in AD progression. Identification of NFTs composed of tau at different stages of truncation may facilitate assessment of neurofibrillary pathology in AD.
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16
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Salloway S, Mintzer J, Weiner MF, Cummings JL. Disease-modifying therapies in Alzheimer's disease. Alzheimers Dement 2008; 4:65-79. [PMID: 18631951 DOI: 10.1016/j.jalz.2007.10.001] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Accepted: 10/24/2007] [Indexed: 12/22/2022]
Abstract
Alzheimer's disease (AD) is a chronic, progressive, neurodegenerative disorder that places a substantial burden on patients, their families, and society. The disease affects approximately 5 million individuals in the United States, with an annual cost of care greater than $100 billion. During the past dozen years, several agents have been approved that enhance cognition and global function of AD patients, and recent advances in understanding AD pathogenesis has led to the development of numerous compounds that might modify the disease process. A wide array of antiamyloid and neuroprotective therapeutic approaches are under investigation on the basis of the hypothesis that amyloid beta (A beta) protein plays a pivotal role in disease onset and progression and that secondary consequences of A beta generation and deposition, including tau hyperphosphorylation and neurofibrillary tangle formation, oxidation, inflammation, and excitotoxicity, contribute to the disease process. Interventions in these processes with agents that reduce amyloid production, limit aggregation, or increase removal might block the cascade of events comprising AD pathogenesis. Reducing tau hyperphosphorylation, limiting oxidation and excitotoxicity, and controlling inflammation might be beneficial disease-modifying strategies. Potentially neuroprotective and restorative treatments such as neurotrophins, neurotrophic factor enhancers, and stem cell-related approaches are also under investigation.
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Affiliation(s)
- Stephen Salloway
- Department of Clinical Neuroscience, Division of Biology and Medicine, Brown Medical School, Providence, RI, USA.
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17
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Chun W, Waldo GS, Johnson GVW. Split GFP complementation assay: a novel approach to quantitatively measure aggregation of tau in situ: effects of GSK3beta activation and caspase 3 cleavage. J Neurochem 2007; 103:2529-39. [PMID: 17908237 DOI: 10.1111/j.1471-4159.2007.04941.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
To quantitatively measure tau aggregation in situ, we established a cell model system using a split green fluorescence protein (GFP) complementation assay. In this assay the more aggregated the protein of interest the lower the GFP fluorescence. Tau microtubule-binding domain constructs, whose aggregation characteristics have been described previously (Khlistunova et al. 2006), were used to validate the assay. The aggregation-prone construct exhibited the lowest GFP intensity whereas the aggregation-resistant construct showed the highest GFP intensity. To examine the role of glycogen synthase kinase 3beta (GSK3beta) activity and caspase 3 cleavage on tau aggregation, GFP complementation of full length (T4), caspase-cleaved (T4C3), and pseudophosphorylated at S396/S404 (T4-2EC) tau was examined in the presence of an active or a kinase-dead GSK3beta. Extensive phosphorylation of T4 by GSK3beta resulted in increased GFP intensity. T4C3 showed neither efficient phosphorylation nor a significant GFP intensity change by GSK3beta. The GFP intensity of T4-2EC was significantly reduced by GSK3beta accompanying its presence in the sarkosyl-insoluble fraction, thus demonstrating that T4-2EC was partitioning into aggregates. This indicates that if the majority of tau is phosphorylated at S396/S404, in combination with increased GSK3beta activity, tau aggregation is favored. These data demonstrate that split GFP complementation may be a valuable approach to determine the aggregation process in living cells.
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Affiliation(s)
- Wanjoo Chun
- Department of Psychiatry, University of Alabama at Birmingham School of Medicine, Alabama, USA
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18
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Chun W, Johnson GVW. Activation of Glycogen Synthase Kinase 3β Promotes the Intermolecular Association of Tau. J Biol Chem 2007; 282:23410-7. [PMID: 17565981 DOI: 10.1074/jbc.m703706200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Tau is hyperphosphorylated and undergoes proteolysis in Alzheimer disease brain. Caspase-cleaved tau efficiently forms fibrillary structures in vitro and in situ. Glycogen synthase kinase 3beta (GSK3beta) phosphorylates tau and induces the aggregation of caspase-cleaved tau in situ. Given the hypothesis that increased association of tau precedes the formation of fibrillar structures, we generated a cell model to quantitate the extent of tau association in situ using fluorescence resonance energy transfer (FRET) microscopy. The cyan and yellow fluorescent proteins were attached to full-length (T4) and caspase-cleaved (T4C3) tau at either the N or C termini, and a pair of cyan and yellow fluorescent protein-tagged tau were co-transfected into human embryonic kidney cells. The FRET efficiency was examined in the presence of a constitutively active or a kinase-dead GSK3beta. Active GSK3beta significantly increased FRET efficiency with both T4 and T4C3, indicating that GSK3beta activation resulted in an increase in the self-association of both T4 and T4C3, but interestingly only T4 is efficiently phosphorylated by GSK3beta. There was no significant difference in FRET efficiency between T4 and T4C3, although only T4C3 in the presence of active GSK3beta leads to the formation of Sarkosyl-insoluble inclusions. These FRET studies demonstrate that GSK3beta facilitates the association of T4 and T4C3, and the presence of caspase-cleaved tau is necessary for the evolution of tau oligomers into Sarkosyl-insoluble inclusions even though it is not extensively phosphorylated. These data imply that increased association of tau should not be regarded as a direct indicator of the formation of insoluble tau aggregates.
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Affiliation(s)
- Wanjoo Chun
- Department of Psychiatry, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama 35294, USA
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Abstract
Alzheimer's disease (AD) is the most common form of dementia in industrialized nations. If more effective therapies are not developed that either prevent AD or block progression of the disease in its very early stages, the economic and societal cost of caring for AD patients will be devastating. Only two types of drugs are currently approved for the treatment of AD: inhibitors of acetyl cholinesterase, which symptomatically enhance cognitive state to some degree but are not disease modifying; and the adamantane derivative, memantine. Memantine preferentially blocks excessive NMDA receptor activity without disrupting normal receptor activity and is thought to be a neuroprotective agent that blocks excitotoxicty. Memantine therefore may have a potentially disease modifying effect in multiple neurodegenerative conditions. An improved understanding of the pathogeneses of AD has now led to the identification of numerous therapeutic targets designed to alter amyloid beta protein (Abeta) or tau accumulation. Therapies that alter Abeta and tau through these various targets are likely to have significant disease modifying effects. Many of these targets have been validated in proof of concept studies in preclinical animal models, and some potentially disease modifying therapies targeting Abeta or tau are being tested in the clinic. This review will highlight both the promise of and the obstacles to developing such disease modifying AD therapies.
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Affiliation(s)
- Todd E Golde
- Mayo Clinic College of Medicine, Department of Neuroscience, Mayo Clinic Jacksonville 4500 San Pablo Road., Jacksonville, Florida 32224, USA.
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Guillozet-Bongaarts AL, Cahill ME, Cryns VL, Reynolds MR, Berry RW, Binder LI. Pseudophosphorylation of tau at serine 422 inhibits caspase cleavage: in vitro evidence and implications for tangle formation in vivo. J Neurochem 2006; 97:1005-14. [PMID: 16606369 DOI: 10.1111/j.1471-4159.2006.03784.x] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The tangles of Alzheimer's disease (AD) are comprised of the tau protein displaying numerous alterations, including phosphorylation at serine 422 (S422) and truncation at aspartic acid 421 (D421). Truncation at the latter site appears to result from activation of caspases, a class of proteases that cleave specifically at aspartic acid residues. It has been proposed that phosphorylation at or near caspase cleavage sites could regulate the ability of the protease to cleave at those sites. Here, we use tau pseudophosphorylated at S422 (S422E) to examine the effects of tau phosphorylation on its cleavage by caspase 3. We find that S422E tau is more resistant to proteolysis by caspase 3 than non-pseudophosphorylated tau. Additionally, we use antibodies directed against the phosphorylation site and against the truncation epitope to assess the presence of these epitopes in neurofibrillary tangles in the aged human brain. We show that phosphorylation precedes truncation during tangle maturation. Moreover, the distribution of the two epitopes suggests that a significant length of time (perhaps as much as two decades) elapses between S422 phosphorylation and cleavage at D421. We further conclude that tau phosphorylation at S422 may be a protective mechanism that inhibits cleavage in vivo.
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Affiliation(s)
- Angela L Guillozet-Bongaarts
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
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Matsui T, Ramasamy K, Ingelsson M, Fukumoto H, Conrad C, Frosch MP, Irizarry MC, Yuan J, Hyman BT. Coordinated Expression of Caspase 8, 3 and 7 mRNA in Temporal Cortex of Alzheimer Disease: Relationship to Formic Acid Extractable Aβ42 Levels. J Neuropathol Exp Neurol 2006; 65:508-15. [PMID: 16772874 DOI: 10.1097/01.jnen.0000229238.05748.12] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Recent studies support the hypothesis that Alzheimer disease (AD)-associated amyloid-beta protein (Abeta) may induce apoptosis mediated by a caspase cascade. To assess whether mRNA levels of caspase-3, 7, 8 and 9 change in AD brain, and whether these changes correlate with neurofibrillary tangles, Abeta40 or Abeta42 protein levels or senile plaques, 25 AD and 21 non-demented control brains were examined. Elevated mRNA levels of caspases-7 and 8 measured by a quantitative PCR method were observed in the AD temporal neocortex as compared to the control brains. No significant differences were noticed in levels of caspases-3 or 9 between AD and control brains. Multiple regression analysis demonstrated that, within subjects, the mRNA levels of caspase-8 strongly correlated with both caspse-3 and caspase-7 independently of postmortem interval. Further, there was a strong positive correlation of caspase-8 levels with formic acid extractable Abeta42 levels. Our results suggest that the transcriptional activation of key components of the apoptotic cascade correlates with accumulation of Abeta 42. Thus, a principal caspase pathway from caspase-8 to caspase-3 and/or 7 may contribute to neuron loss in AD brain.
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Affiliation(s)
- Toshifumi Matsui
- Alzheimer Research Unit, Mass General Institute for Neurodegenerative Disease, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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Yin H, Kuret J. C-terminal truncation modulates both nucleation and extension phases of τ fibrillization. FEBS Lett 2005; 580:211-5. [PMID: 16364303 DOI: 10.1016/j.febslet.2005.11.077] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Accepted: 11/30/2005] [Indexed: 11/16/2022]
Abstract
Proteolytic post-translational modification has been proposed as an early stage event in the aggregation of tau protein and formation of neurofibrillary lesions in Alzheimer's disease. Caspases and other proteases cleave tau in vivo at discrete locations including Asp421 and Glu391. Both cleavage products are prone to aggregation relative to wild-type, full-length tau protein. To determine the mechanism underlying this effect, the fibrillization of tau truncated after Asp421 and Glu391 residues was characterized in a full-length four-repeat tau background using quantitative electron microscopy methods under homogeneous nucleation conditions. Both C-terminal truncations decreased critical concentration relative to full-length tau, resulting in more filament mass at reaction plateau. Moreover, truncation directly augmented the efficiency of the nucleation reaction. The results suggest the mechanism through which C-terminal proteolysis can modulate tau filament accumulation depending on whether it precedes or follows nucleation.
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Affiliation(s)
- Haishan Yin
- Ohio State Biochemistry Program, The Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA
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