201
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Targeting the mTOR Signaling Network for Alzheimer’s Disease Therapy. Mol Neurobiol 2013; 49:120-35. [DOI: 10.1007/s12035-013-8505-8] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Accepted: 07/01/2013] [Indexed: 12/29/2022]
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202
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Miyata Y, Li X, Lee HF, Jinwal UK, Srinivasan SR, Seguin SP, Young ZT, Brodsky JL, Dickey CA, Sun D, Gestwicki JE. Synthesis and initial evaluation of YM-08, a blood-brain barrier permeable derivative of the heat shock protein 70 (Hsp70) inhibitor MKT-077, which reduces tau levels. ACS Chem Neurosci 2013; 4:930-9. [PMID: 23472668 DOI: 10.1021/cn300210g] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The molecular chaperone, heat shock protein 70 (Hsp70), is an emerging drug target for treating neurodegenerative tauopathies. We recently found that one promising Hsp70 inhibitor, MKT-077, reduces tau levels in cellular models. However, MKT-077 does not penetrate the blood-brain barrier (BBB), limiting its use as either a clinical candidate or probe for exploring Hsp70 as a drug target in the central nervous system (CNS). We hypothesized that replacing the cationic pyridinium moiety in MKT-077 with a neutral pyridine might improve its clogP and enhance its BBB penetrance. To test this idea, we designed and synthesized YM-08, a neutral analogue of MKT-077. Like the parent compound, YM-08 bound to Hsp70 in vitro and reduced phosphorylated tau levels in cultured brain slices. Pharmacokinetic evaluation in CD1 mice showed that YM-08 crossed the BBB and maintained a brain/plasma (B/P) value of ∼0.25 for at least 18 h. Together, these studies suggest that YM-08 is a promising scaffold for the development of Hsp70 inhibitors suitable for use in the CNS.
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Affiliation(s)
| | | | | | - Umesh K. Jinwal
- Department of Molecular Medicine, University of South Florida, Tampa, Florida, United
States
| | | | - Sandlin P. Seguin
- Department of Biological
Sciences, University of Pittsburgh, Pittsburgh,
Pennsylvania,
United States
| | | | - Jeffrey L. Brodsky
- Department of Biological
Sciences, University of Pittsburgh, Pittsburgh,
Pennsylvania,
United States
| | - Chad A. Dickey
- Department of Molecular Medicine, University of South Florida, Tampa, Florida, United
States
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203
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Bulic B, Pickhardt M, Mandelkow E. Progress and developments in tau aggregation inhibitors for Alzheimer disease. J Med Chem 2013; 56:4135-55. [PMID: 23484434 DOI: 10.1021/jm3017317] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Pharmacological approaches directed toward Alzheimer disease are diversifying in parallel with a growing number of promising targets. Investigations on the microtubule-associated protein tau yielded innovative targets backed by recent findings about the central role of tau in numerous neurodegenerative diseases. In this review, we summarize the recent evolution in the development of nonpeptidic small molecules tau aggregation inhibitors (TAGIs) and their advancement toward clinical trials. The compounds are classified according to their chemical structures, providing correlative insights into their pharmacology. Overall, shared structure-activity traits are emerging, as well as specific binding modes related to their ability to engage in hydrogen bonding. Medicinal chemistry efforts on TAGIs together with encouraging in vivo data argue for successful translation to the clinic.
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Affiliation(s)
- Bruno Bulic
- Laboratory of Organic Synthesis of Functional Systems, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
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204
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Ramachandran G, Udgaonkar JB. Mechanistic studies unravel the complexity inherent in tau aggregation leading to Alzheimer's disease and the tauopathies. Biochemistry 2013; 52:4107-26. [PMID: 23721410 DOI: 10.1021/bi400209z] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The aggregation of the protein tau into amyloid fibrils is known to be involved in the causation of the neurodegenerative tauopathies and the progression of cognitive decline in Alzheimer's disease. This review surveys the mechanism of tau aggregation with special emphasis on the information obtained from biochemical and biophysical studies. First, tau is described from a structure-function perspective. Subsequently, the connection of tau to neurodegeneration is explained, and a description of the tau amyloid fibril is provided. Lastly, studies of the mechanism of tau fibril formation are reviewed, and the physiological significance of these studies with reference to how they can clarify many aspects of disease progression is described. The aim of this review is to underscore how mechanistic studies reveal the complexity of the tau fibril formation pathway and the plethora of species populated on or off the pathway of aggregation, and how this information can be beneficial in the design of inhibitors or drugs that ameliorate neurodegeneration.
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Affiliation(s)
- Gayathri Ramachandran
- National Centre for Biological Sciences, Tata Institute of Fundamental Research , Bangalore 560065, India
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205
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Miyata Y, Rauch JN, Jinwal UK, Thompson AD, Srinivasan S, Dickey CA, Gestwicki JE. Cysteine reactivity distinguishes redox sensing by the heat-inducible and constitutive forms of heat shock protein 70. ACTA ACUST UNITED AC 2013. [PMID: 23177194 DOI: 10.1016/j.chembiol.2012.07.026] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The heat shock protein 70 (Hsp70) family of molecular chaperones has important functions in maintaining proteostasis under stress conditions. Several Hsp70 isoforms, especially Hsp72 (HSPA1A), are dramatically upregulated in response to stress; however, it is unclear whether these family members have biochemical properties that are specifically adapted to these scenarios. The redox-active compound, methylene blue (MB), has been shown to inhibit the ATPase activity of Hsp72 in vitro, and it promotes degradation of the Hsp72 substrate, tau, in cellular and animal models. Here, we report that MB irreversibly inactivates Hsp72 but not the nearly identical, constitutively expressed isoform, heat shock cognate 70 (Hsc70; HSPA8). Mass spectrometry results show that MB oxidizes Cys306, which is not conserved in Hsc70. Molecular models suggested that oxidation of Cys306 exposes Cys267 to modification and that both events contribute to loss of ATP binding in response to MB. Consistent with this model, mutating Cys267 and Cys306 to serine made Hsp72 largely resistant to MB in vitro, and overexpression of the C306S mutant blocked MB-mediated loss of tau in a cellular model. Furthermore, mutating Cys267 and Cys306 to the pseudo-oxidation mimic, aspartic acid, mirrored MB treatment: the C267D and C306D mutants had reduced ATPase activity in vitro, and overexpression of the C267/306D double mutant significantly reduced tau levels in cells. Together, these results suggest that redox sensing by specific cysteine residues in Hsp72, but not Hsc70, may be an important component of the chaperone response to oxidative stress.
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Affiliation(s)
- Yoshinari Miyata
- Department of Pathology, Department of Biological Chemistry, and the Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA
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206
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Xie L, Li W, Winters A, Yuan F, Jin K, Yang S. Methylene blue induces macroautophagy through 5' adenosine monophosphate-activated protein kinase pathway to protect neurons from serum deprivation. Front Cell Neurosci 2013; 7:56. [PMID: 23653592 PMCID: PMC3642497 DOI: 10.3389/fncel.2013.00056] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 04/12/2013] [Indexed: 12/25/2022] Open
Abstract
Methylene blue has been shown to be neuroprotective in multiple experimental neurodegenerative disease models. However, the mechanisms underlying the neuroprotective effects have not been fully elucidated. Previous studies have shown that macroautophagy has multiple beneficial roles for maintaining normal cellular homeostasis and that induction of macroautophagy after myocardial ischemia is protective. In the present study we demonstrated that methylene blue could protect HT22 hippocampal cell death induced by serum deprivation, companied by induction of macroautophagy. We also found that methylene blue-mediated neuroprotection was abolished by macroautophagy inhibition. Interestingly, 5' adenosine monophosphate-activated protein kinase (AMPK) signaling, but not inhibition of mammalian target of rapamycin signaling, was activated at 12 and 24 h after methylene blue treatment in a dose-dependent manner. Methylene blue-induced macroautophagy was blocked by AMPK inhibitor. Consistent with in vitro data, macroautophagy was induced in the cortex and hippocampus of mouse brains treated with methylene blue. Our findings suggest that methylene blue-induced neuroprotection is mediated, at least in part, by macroautophagy though activation of AMPK signaling.
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Affiliation(s)
- Luokun Xie
- Department of Pharmacology and Neuroscience, Institute for Alzheimer's Disease and Aging Research, University of North Texas Health Science Center at FortWorth FortWorth, TX, USA
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207
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Autophagy modulation for Alzheimer's disease therapy. Mol Neurobiol 2013; 48:702-14. [PMID: 23625314 DOI: 10.1007/s12035-013-8457-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 04/09/2013] [Indexed: 01/01/2023]
Abstract
Autophagy is an essential and conserved lysosomal degradation pathway that controls the quality of cytoplasm by eliminating the intracellular aggregated proteins and damaged organelles. Autophagy works in mammalian target of rapamycin (mTOR)-dependent pathway or mTOR-independent pathway to keep the neuronal homeostasis. Mounting evidence has implicated the importance of defective autophagy in the pathogenesis of aging and neurodegenerative diseases, especially in Alzheimer's disease (AD). It has also demonstrated a neuroprotective role of autophagy in mediating the degradation of amyloid beta and tau which are major factors of AD. Amounts of molecules function in either mTOR-dependent pathway or mTOR-independent pathway to induce autophagy, which maybe a potential treatment for AD. In this review, we summarize the latest studies concerning the role of autophagy in AD and explore autophagy modulation as a potential therapeutic strategy for AD. However, to date, little of the researches on autophagy have been performed to investigate the modulation in AD; more investigations need to be confirmed in the future.
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208
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Rodríguez-Martín T, Cuchillo-Ibáñez I, Noble W, Nyenya F, Anderton BH, Hanger DP. Tau phosphorylation affects its axonal transport and degradation. Neurobiol Aging 2013; 34:2146-57. [PMID: 23601672 PMCID: PMC3684773 DOI: 10.1016/j.neurobiolaging.2013.03.015] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 02/15/2013] [Accepted: 03/11/2013] [Indexed: 11/24/2022]
Abstract
Phosphorylated forms of microtubule-associated protein tau accumulate in neurofibrillary tangles in Alzheimer's disease. To investigate the effects of specific phosphorylated tau residues on its function, wild type or phosphomutant tau was expressed in cells. Elevated tau phosphorylation decreased its microtubule binding and bundling, and increased the number of motile tau particles, without affecting axonal transport kinetics. In contrast, reducing tau phosphorylation enhanced the amount of tau bound to microtubules and inhibited axonal transport of tau. To determine whether differential tau clearance is responsible for the increase in phosphomimic tau, we inhibited autophagy in neurons which resulted in a 3-fold accumulation of phosphomimic tau compared with wild type tau, and endogenous tau was unaffected. In autophagy-deficient mouse embryonic fibroblasts, but not in neurons, proteasomal degradation of phosphomutant tau was also reduced compared with wild type tau. Therefore, autophagic and proteasomal pathways are involved in tau degradation, with autophagy appearing to be the primary route for clearing phosphorylated tau in neurons. Defective autophagy might contribute to the accumulaton of tau in neurodegenerative diseases.
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209
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Lee MJ, Lee JH, Rubinsztein DC. Tau degradation: the ubiquitin-proteasome system versus the autophagy-lysosome system. Prog Neurobiol 2013; 105:49-59. [PMID: 23528736 DOI: 10.1016/j.pneurobio.2013.03.001] [Citation(s) in RCA: 257] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Revised: 03/03/2013] [Accepted: 03/13/2013] [Indexed: 01/01/2023]
Abstract
The ubiquitin-proteasome system (UPS) and the autophagy-lysosome system are two major protein quality control mechanisms in eukaryotic cells. While the UPS has been considered for decades as the critical regulator in the degradation of various aggregate-prone proteins, autophagy has more recently been shown to be an important pathway implicated in neuronal health and disease. The two hallmark lesions of Alzheimer's disease (AD) are extracellular β-amyloid plaques and intracellular tau tangles. It has been suggested that tau accumulation is pathologically more relevant to the development of neurodegeneration and cognitive decline in AD patients than β-amyloid plaques. Here, we review the UPS and autophagy-mediated tau clearance mechanisms and outline the biochemical connections between these two processes. In addition, we discuss pharmacological methods that target these degradation systems for the treatment and prevention of AD.
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Affiliation(s)
- Min Jae Lee
- Department of Applied Chemistry, College of Applied Sciences, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Republic of Korea.
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210
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Ryu HW, Oh WK, Jang IS, Park J. Amurensin G induces autophagy and attenuates cellular toxicities in a rotenone model of Parkinson's disease. Biochem Biophys Res Commun 2013; 433:121-6. [PMID: 23485458 DOI: 10.1016/j.bbrc.2013.02.053] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 02/08/2013] [Indexed: 01/24/2023]
Abstract
Although Parkinson's disease is a common neurodegenerative disorder its cause is still unknown. Recently, several reports showed that inducers of autophagy attenuate cellular toxicities in Parkinson's disease models. In this report we screened HEK293 cells that stably express GFP-LC3, a marker of autophagy, for autophagy inducers and identified amurensin G, a compound isolated from the wild grape (Vitis amurensis). Amurensin G treatment induced punctate cytoplasmic expression of GFP-LC3 and increased the expression level of endogenous LC3-II. Incubation of human dopaminergic SH-SY5Y cells with amurensin G attenuated the cellular toxicities of rotenone in a model of Parkinson's disease. Amurensin G inhibited rotenone-induced apoptosis and interfered with rotenone-induced G2/M cell cycle arrest. In addition, knockdown of beclin1, a regulator of autophagy, abolished the effect of amurensin G. These data collectively indicate that amurensin G attenuates cellular toxicities through the induction of autophagy.
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Affiliation(s)
- Hyun-Wook Ryu
- Division of Biological Science and Technology, Yonsei University, Wonju, Republic of Korea
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211
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Crowe A, James MJ, Lee VMY, Smith AB, Trojanowski JQ, Ballatore C, Brunden KR. Aminothienopyridazines and methylene blue affect Tau fibrillization via cysteine oxidation. J Biol Chem 2013; 288:11024-37. [PMID: 23443659 DOI: 10.1074/jbc.m112.436006] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Alzheimer disease and several other neurodegenerative disorders are characterized by the accumulation of intraneuronal fibrils comprised of the protein Tau. Tau is normally a soluble protein that stabilizes microtubules, with splice isoforms that contain either three (3-R) or four (4-R) microtubule binding repeats. The formation of Tau fibrils is thought to result in neuronal damage, and inhibitors of Tau fibrillization may hold promise as therapeutic agents. The process of Tau fibrillization can be replicated in vitro, and a number of small molecules have been identified that inhibit Tau fibril formation. However, little is known about how these molecules affect Tau fibrillization. Here, we examined the mechanism by which the previously described aminothieno pyridazine (ATPZ) series of compounds inhibit Tau fibrillization. Active ATPZs were found to promote the oxidation of the two cysteine residues within 4-R Tau by a redox cycling mechanism, resulting in the formation of a disulfide-containing compact monomer that was refractory to fibrillization. Moreover, the ATPZs facilitated intermolecular disulfide formation between 3-R Tau monomers, leading to dimers that were capable of fibrillization. The ATPZs also caused cysteine oxidation in molecules unrelated to Tau. Interestingly, methylene blue, an inhibitor of Tau fibrillization under evaluation in Alzheimer disease clinical trials, caused a similar oxidation of cysteines in Tau and other molecules. These findings reveal that the ATPZs and methylene blue act by a mechanism that may affect their viability as potential therapeutic agents.
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Affiliation(s)
- Alex Crowe
- Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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212
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Steele JW, Fan E, Kelahmetoglu Y, Tian Y, Bustos V. Modulation of Autophagy as a Therapeutic Target for Alzheimer's Disease. POSTDOC JOURNAL : A JOURNAL OF POSTDOCTORAL RESEARCH AND POSTDOCTORAL AFFAIRS 2013; 1:21-34. [PMID: 28286801 PMCID: PMC5342246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Macroautophagy (autophagy) is a conserved cellular pathway that regulates the degradation of long-lived proteins, protein aggregates, and cellular organelles. Autophagy is essential for maintaining neuronal homeostasis; however, neuronal autophagic efficiency decreases with age. Therefore, aging is one of the greatest risk factors for development of Alzheimer's disease (AD), a slowly progressing form of neurodegeneration that develops over the course of 10-20 years prior to the onset of overt clinical symptoms. AD is defined neuropathologically by the presence of extracellular aggregates of the amyloidogenic protein amyloid-β (Aβ) and intracellular accumulation of the microtubule-associated protein tau. At end-stage Alzheimer's disease, abnormal autophagic pathology has been reported in human brain and in multiple mouse models of AD, suggesting that an intimate association may exist between neuronal autophagy stasis and Alzheimer's-related pathology. Here, we highlight recent evidence that the autophagic pathway plays a role in both the generation and clearance of the pathogenic Aβ protein and its precursors. The primary focus of this review is to examine the compelling research that highlights the autophagic pathway as a therapeutic target for AD and to discuss the therapeutic space around autophagy-regulating programs for AD. Finally, we propose that programs targeting autophagy regulation for AD ought to consider prophylactic or early stage intervention trials based on evidence against druggability of this pathway in late-stage disease.
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Affiliation(s)
- John W Steele
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10065
| | - Emily Fan
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10065
| | - Yildiz Kelahmetoglu
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10065
| | - Yuan Tian
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10065
| | - Victor Bustos
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10065
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213
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Assimon VA, Gillies AT, Rauch JN, Gestwicki JE. Hsp70 protein complexes as drug targets. Curr Pharm Des 2013; 19:404-17. [PMID: 22920901 PMCID: PMC3593251 DOI: 10.2174/138161213804143699] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 08/15/2012] [Indexed: 12/22/2022]
Abstract
Heat shock protein 70 (Hsp70) plays critical roles in proteostasis and is an emerging target for multiple diseases. However, competitive inhibition of the enzymatic activity of Hsp70 has proven challenging and, in some cases, may not be the most productive way to redirect Hsp70 function. Another approach is to inhibit Hsp70's interactions with important co-chaperones, such as J proteins, nucleotide exchange factors (NEFs) and tetratricopeptide repeat (TPR) domain-containing proteins. These co-chaperones normally bind Hsp70 and guide its many diverse cellular activities. Complexes between Hsp70 and co-chaperones have been shown to have specific functions, including roles in pro-folding, pro-degradation and pro-trafficking pathways. Thus, a promising strategy may be to block protein- protein interactions between Hsp70 and its co-chaperones or to target allosteric sites that disrupt these contacts. Such an approach might shift the balance of Hsp70 complexes and re-shape the proteome and it has the potential to restore healthy proteostasis. In this review, we discuss specific challenges and opportunities related to these goals. By pursuing Hsp70 complexes as drug targets, we might not only develop new leads for therapeutic development, but also discover new chemical probes for use in understanding Hsp70 biology.
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Affiliation(s)
- Victoria A Assimon
- Department of Pathology, Life Sciences Institute, University of Michigan, 210 Washtenaw Ave., Ann Arbor, MI 48109-2216, USA
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214
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Hosokawa M, Arai T, Masuda-Suzukake M, Nonaka T, Yamashita M, Akiyama H, Hasegawa M. Methylene blue reduced abnormal tau accumulation in P301L tau transgenic mice. PLoS One 2012; 7:e52389. [PMID: 23285020 PMCID: PMC3527507 DOI: 10.1371/journal.pone.0052389] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 11/14/2012] [Indexed: 11/24/2022] Open
Abstract
In neurodegenerative disorders, abnormally hyperphosphorylated and aggregated tau accumulates intracellularly, a mechanism which is thought to induce neuronal cell death. Methylene blue, a type of phenothiazine, has been reported to inhibit tau aggregation in vitro. However, the effect of methylene blue in vivo has remained unknown. Therefore, we examined whether methylene blue suppresses abnormal tau accumulation using P301L tau transgenic mice. At 8 to 11 months of age, these mice were orally administered methylene blue for 5 months. Subsequent results of Western blotting analysis revealed that this agent reduced detergent-insoluble phospho-tau. Methylene blue may have potential as a drug candidate for the treatment of tauopathy.
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Affiliation(s)
- Masato Hosokawa
- Department of Dementia and Higher Brain Function, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
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215
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Abstract
Tau aggregates are present in several neurodegenerative diseases and correlate with the severity of memory deficit in AD (Alzheimer's disease). However, the triggers of tau aggregation and tau-induced neurodegeneration are still elusive. The impairment of protein-degradation systems might play a role in such processes, as these pathways normally keep tau levels at a low level which may prevent aggregation. Some proteases can process tau and thus contribute to tau aggregation by generating amyloidogenic fragments, but the complete clearance of tau mainly relies on the UPS (ubiquitin-proteasome system) and the ALS (autophagy-lysosome system). In the present paper, we focus on the regulation of the degradation of tau by the UPS and ALS and its relation to tau aggregation. We anticipate that stimulation of these two protein-degradation systems might be a potential therapeutic strategy for AD and other tauopathies.
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216
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Abstract
Frontotemporal dementia (FTD) is a common dementia syndrome in patients under the age of 65 years with many features overlapping with amyotrophic lateral sclerosis (ALS). The link between FTD and ALS has been strengthened by the discovery that a hexanucleotide repeat expansion in a non-coding region of the C9ORF72 gene causes both familial and sporadic types of these two diseases. As we begin to understand the pathophysiological mechanisms by which this mutation leads to FTD and ALS (c9FTD/ALS), new targets for disease-modifying therapies will likely be unveiled. Putative C9ORF72 expansion pathogenic mechanisms include loss of C9ORF72 protein function, sequestration of nucleic acid binding proteins due to expanded hexanucleotide repeats, or a combination of the two. New animal models and other research tools informed by work in other repeat expansion neurodegenerative diseases such as the spinocerebellar ataxias will help to elucidate the mechanisms of C9ORF72-mediated disease. Similarly, re-examining previous studies of drugs developed to treat ALS in light of this new mutation may identify novel FTD treatments. Ultimately, research consortiums incorporating animal models and well-characterized clinical populations will be necessary to fully understand the natural history of the c9FTD/ALS clinical phenotypes and identify biomarkers and therapeutic agents that can cure the most common form of genetically determined FTD and ALS.
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Affiliation(s)
- Sharon J Sha
- University of California, San Francisco, Memory and Aging Center, Box 1207, San Francisco, CA 94143-1207, USA
| | - Adam Boxer
- University of California, San Francisco, Memory and Aging Center, Box 1207, San Francisco, CA 94143-1207, USA
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217
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Wu JW, Herman M, Liu L, Simoes S, Acker CM, Figueroa H, Steinberg JI, Margittai M, Kayed R, Zurzolo C, Di Paolo G, Duff KE. Small misfolded Tau species are internalized via bulk endocytosis and anterogradely and retrogradely transported in neurons. J Biol Chem 2012. [PMID: 23188818 DOI: 10.1074/jbc.m112.394528] [Citation(s) in RCA: 370] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The accumulation of Tau into aggregates is associated with key pathological events in frontotemporal lobe degeneration (FTD-Tau) and Alzheimer disease (AD). Recent data have shown that misfolded Tau can be internalized by cells in vitro (Frost, B., Jacks, R. L., and Diamond, M. I. (2009) J. Biol. Chem. 284, 12845-12852) and propagate pathology in vivo (Clavaguera, F., Bolmont, T., Crowther, R. A., Abramowski, D., Frank, S., Probst, A., Fraser, G., Stalder, A. K., Beibel, M., Staufenbiel, M., Jucker, M., Goedert, M., and Tolnay, M. (2009) Nat. Cell Biol. 11, 909-913; Lasagna-Reeves, C. A., Castillo-Carranza, D. L., Sengupta, U., Guerrero-Munoz, M. J., Kiritoshi, T., Neugebauer, V., Jackson, G. R., and Kayed, R. (2012) Sci. Rep. 2, 700). Here we show that recombinant Tau misfolds into low molecular weight (LMW) aggregates prior to assembly into fibrils, and both extracellular LMW Tau aggregates and short fibrils, but not monomers, long fibrils, nor long filaments purified from brain extract are taken up by neurons. Remarkably, misfolded Tau can be internalized at the somatodendritic compartment, or the axon terminals and it can be transported anterogradely, retrogradely, and can enhance tauopathy in vivo. The internalized Tau aggregates co-localize with dextran, a bulk-endocytosis marker, and with the endolysosomal compartments. Our findings demonstrate that exogenous Tau can be taken up by cells, uptake depends on both the conformation and size of the Tau aggregates and once inside cells, Tau can be transported. These data provide support for observations that tauopathy can spread trans-synaptically in vivo, via cell-to-cell transfer.
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Affiliation(s)
- Jessica W Wu
- Department of Pathology and Cell Biology, Taub Institute for Alzheimer's Disease Research, Columbia University, New York, New York 10032, USA
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218
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Thompson AD, Scaglione KM, Prensner J, Gillies AT, Chinnaiyan A, Paulson HL, Jinwal UK, Dickey CA, Gestwicki JE. Analysis of the tau-associated proteome reveals that exchange of Hsp70 for Hsp90 is involved in tau degradation. ACS Chem Biol 2012; 7:1677-86. [PMID: 22769591 PMCID: PMC3477299 DOI: 10.1021/cb3002599] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The microtubule associated protein tau (MAPT/tau) aberrantly accumulates in 15 neurodegenerative diseases, termed tauopathies. One way to treat tauopathies may be to accelerate tau clearance, but the molecular mechanisms governing tau stability are not yet clear. We recently identified chemical probes that markedly accelerate the clearance of tau in cellular and animal models. In the current study, we used one of these probes in combination with immunoprecipitation and mass spectrometry to identify 48 proteins whose association with tau changes during the first 10 min after treatment. These proteins included known modifiers of tau proteotoxicity, such as ILF-2 (NFAT), ILF-3, and ataxin-2. A striking observation from the data set was that tau binding to heat shock protein 70 (Hsp70) decreased, whereas binding to Hsp90 significantly increased. Both chaperones have been linked to tau homeostasis, but their mechanisms have not been established. Using peptide arrays and binding assays, we found that Hsp70 and Hsp90 appeared to compete for binding to shared sites on tau. Further, the Hsp90-bound complex proved to be important in initiating tau clearance in cells. These results suggest that the relative levels of Hsp70 and Hsp90 may help determine whether tau is retained or degraded. Consistent with this model, analysis of reported microarray expression data from Alzheimer's disease patients and age-matched controls showed that the levels of Hsp90 are reduced in the diseased hippocampus. These studies suggest that Hsp70 and Hsp90 work together to coordinate tau homeostasis.
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Affiliation(s)
- Andrea D. Thompson
- Department of Pathology, University of Michigan, Ann Arbor, MI 48103
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48103
| | | | - John Prensner
- Department of Pathology, University of Michigan, Ann Arbor, MI 48103
| | - Anne T. Gillies
- Department of Pathology, University of Michigan, Ann Arbor, MI 48103
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48103
| | - Arul Chinnaiyan
- Department of Pathology, University of Michigan, Ann Arbor, MI 48103
| | - Henry L. Paulson
- Department of Neurology, University of Michigan, Ann Arbor, MI 48103
| | - Umesh K. Jinwal
- Department of Pharmaceutical Sciences, University of South Florida, Tampa, FL 33613
| | - Chad A. Dickey
- Department of Molecular Medicine, University of South Florida, Tampa, FL 33613
| | - Jason E. Gestwicki
- Department of Pathology, University of Michigan, Ann Arbor, MI 48103
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48103
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48103
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219
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Inhibition of amyloid-beta peptide aggregation rescues the autophagic deficits in the TgCRND8 mouse model of Alzheimer disease. Biochim Biophys Acta Mol Basis Dis 2012; 1822:1629-37. [PMID: 22800931 DOI: 10.1016/j.bbadis.2012.07.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 07/06/2012] [Accepted: 07/09/2012] [Indexed: 02/02/2023]
Abstract
scyllo-Inositol (SI) is an endogenous inositol stereoisomer known to inhibit aggregation and fibril formation of the amyloid-beta peptide (Aβ). Human clinical trials using SI to treat Alzheimer disease (AD) patients have shown potential benefits. In light of the growing therapeutic potential of SI, the objective of our study was to gain a more thorough understanding of the mechanism of action. In addition to Aβ plaques, a prominent pathological feature of AD is the extensive accumulation of autophagic vacuoles (AVs) suggesting dysfunction in this degradation pathway. Using the TgCRND8 mouse model for AD, we examined SI treatment effects on various components of the autophagic pathway. Autophagy impairment in TgCRND8 mice occurs in the latter stages of the pathway where AV-lysosome fusion and lysosomal degradation take place. SI treatment attenuated this impairment with a decrease in the size and the number of accumulated AVs. We propose that the beneficial effects of SI-Aβ interactions may resolve autophagic deficiencies in the AD brains.
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220
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Himmelstein DS, Ward SM, Lancia JK, Patterson KR, Binder LI. Tau as a therapeutic target in neurodegenerative disease. Pharmacol Ther 2012; 136:8-22. [PMID: 22790092 DOI: 10.1016/j.pharmthera.2012.07.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 06/22/2012] [Indexed: 01/16/2023]
Abstract
Tau is a microtubule-associated protein thought to help modulate the stability of neuronal microtubules. In tauopathies, including Alzheimer's disease and several frontotemporal dementias, tau is abnormally modified and misfolded resulting in its disassociation from microtubules and the generation of pathological lesions characteristic for each disease. A recent surge in the population of people with neurodegenerative tauopathies has highlighted the immense need for disease-modifying therapies for these conditions, and new attention has focused on tau as a potential target for intervention. In the current work we summarize evidence linking tau to disease pathogenesis and review recent therapeutic approaches aimed at ameliorating tau dysfunction. The primary therapeutic tactics considered include kinase inhibitors and phosphatase activators, immunotherapies, small molecule inhibitors of protein aggregation, and microtubule-stabilizing agents. Although the evidence for tau-based treatments is encouraging, additional work is undoubtedly needed to optimize each treatment strategy for the successful development of safe and effective therapeutics.
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Affiliation(s)
- Diana S Himmelstein
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Tarry 8-754, 300 E. Superior St., Chicago, IL 60611, USA
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