1
|
Rad SK, Arya A, Karimian H, Madhavan P, Rizwan F, Koshy S, Prabhu G. Mechanism involved in insulin resistance via accumulation of β-amyloid and neurofibrillary tangles: link between type 2 diabetes and Alzheimer's disease. Drug Des Devel Ther 2018; 12:3999-4021. [PMID: 30538427 PMCID: PMC6255119 DOI: 10.2147/dddt.s173970] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The pathophysiological link between type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) has been suggested in several reports. Few findings suggest that T2DM has strong link in the development process of AD, and the complete mechanism is yet to be revealed. Formation of amyloid plaques (APs) and neurofibrillary tangles (NFTs) are two central hallmarks in the AD. APs are the dense composites of β-amyloid protein (Aβ) which accumulates around the nerve cells. Moreover, NFTs are the twisted fibers containing hyperphosphorylated tau proteins present in certain residues of Aβ that build up inside the brain cells. Certain factors contribute to the aetiogenesis of AD by regulating insulin signaling pathway in the brain and accelerating the formation of neurotoxic Aβ and NFTs via various mechanisms, including GSK3β, JNK, CamKII, CDK5, CK1, MARK4, PLK2, Syk, DYRK1A, PPP, and P70S6K. Progression to AD could be influenced by insulin signaling pathway that is affected due to T2DM. Interestingly, NFTs and APs lead to the impairment of several crucial cascades, such as synaptogenesis, neurotrophy, and apoptosis, which are regulated by insulin, cholesterol, and glucose metabolism. The investigation of the molecular cascades through insulin functions in brain contributes to probe and perceive progressions of diabetes to AD. This review elaborates the molecular insights that would help to further understand the potential mechanisms linking T2DM and AD.
Collapse
Affiliation(s)
- Sima Kianpour Rad
- Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Aditya Arya
- Department of Pharmacology and Therapeutics, School of Medicine, Faculty of Health and Medical Sciences, Taylor's University, Subang Jaya, Malaysia,
- Department of Pharmacology and Therapeutics, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, Australia,
- Malaysian Institute of Pharmaceuticals and Nutraceuticals (IPharm), Bukit Gambir, Gelugor, Pulau Pinang, Malaysia,
| | - Hamed Karimian
- Department of Pharmacology and Therapeutics, School of Medicine, Faculty of Health and Medical Sciences, Taylor's University, Subang Jaya, Malaysia,
| | - Priya Madhavan
- School of Medicine, Faculty of Health and Medical Sciences, Taylor's University, Subang Jaya, Malaysia
| | - Farzana Rizwan
- School of Medicine, Faculty of Health and Medical Sciences, Taylor's University, Subang Jaya, Malaysia
| | - Shajan Koshy
- School of Medicine, Faculty of Health and Medical Sciences, Taylor's University, Subang Jaya, Malaysia
| | - Girish Prabhu
- School of Medicine, Faculty of Health and Medical Sciences, Taylor's University, Subang Jaya, Malaysia
| |
Collapse
|
2
|
Walker KR, Tesco G. Molecular mechanisms of cognitive dysfunction following traumatic brain injury. Front Aging Neurosci 2013; 5:29. [PMID: 23847533 PMCID: PMC3705200 DOI: 10.3389/fnagi.2013.00029] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 06/18/2013] [Indexed: 12/12/2022] Open
Abstract
Traumatic brain injury (TBI) results in significant disability due to cognitive deficits particularly in attention, learning and memory, and higher-order executive functions. The role of TBI in chronic neurodegeneration and the development of neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic Lateral Sclerosis (ALS) and most recently chronic traumatic encephalopathy (CTE) is of particular importance. However, despite significant effort very few therapeutic options exist to prevent or reverse cognitive impairment following TBI. In this review, we present experimental evidence of the known secondary injury mechanisms which contribute to neuronal cell loss, axonal injury, and synaptic dysfunction and hence cognitive impairment both acutely and chronically following TBI. In particular we focus on the mechanisms linking TBI to the development of two forms of dementia: AD and CTE. We provide evidence of potential molecular mechanisms involved in modulating Aβ and Tau following TBI and provide evidence of the role of these mechanisms in AD pathology. Additionally we propose a mechanism by which Aβ generated as a direct result of TBI is capable of exacerbating secondary injury mechanisms thereby establishing a neurotoxic cascade that leads to chronic neurodegeneration.
Collapse
Affiliation(s)
- Kendall R Walker
- Alzheimer's Disease Research Laboratory, Department of Neuroscience, Tufts University School of Medicine Boston, MA, USA
| | | |
Collapse
|
3
|
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]
|
4
|
Cross-linking of cell surface amyloid precursor protein leads to increased β-amyloid peptide production in hippocampal neurons: implications for Alzheimer's disease. J Neurosci 2012; 32:10674-85. [PMID: 22855816 DOI: 10.1523/jneurosci.6473-11.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The accumulation of the β-amyloid peptide (Aβ) in Alzheimer's disease (AD) is thought to play a causative role in triggering synaptic dysfunction in neurons, leading to their eventual demise through apoptosis. Aβ is produced and secreted upon sequential cleavage of the amyloid precursor protein (APP) by β-secretases and γ-secretases. However, while Aβ levels have been shown to be increased in the brains of AD patients, little is known about how the cleavage of APP and the subsequent generation of Aβ is influenced, or whether the cleavage process changes over time. It has been proposed that Aβ can bind APP and promote amyloidogenic processing of APP, further enhancing Aβ production. Proof of this idea has remained elusive because a clear mechanism has not been identified, and the promiscuous nature of Aβ binding complicates the task of demonstrating the idea. To work around these problems, we used an antibody-mediated approach to bind and cross-link cell-surface APP in cultured rat primary hippocampal neurons. Here we show that cross-linking of APP is sufficient to raise the levels of Aβ in viable neurons with a concomitant increase in the levels of the β-secretase BACE1. This appears to occur as a result of a sorting defect that stems from the caspase-3-mediated inactivation of a key sorting adaptor protein, namely GGA3, which prevents the lysosomal degradation of BACE1. Together, our data suggest the occurrence of a positive pathogenic feedback loop involving Aβ and APP in affected neurons possibly allowing Aβ to spread to nearby healthy neurons.
Collapse
|
5
|
Kandimalla RJL, Wani WY, Binukumar BK, Gill KD. siRNA against presenilin 1 (PS1) down regulates amyloid β42 production in IMR-32 cells. J Biomed Sci 2012; 19:2. [PMID: 22214483 PMCID: PMC3282656 DOI: 10.1186/1423-0127-19-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Accepted: 01/03/2012] [Indexed: 11/18/2022] Open
Abstract
Background One of the pathological hallmarks of Alzheimer's disease (AD) is the deposition of the ~4 kDa amyloid β protein (Aβ) within lesions known as senile plaques. Aβ is also deposited in the walls of cerebral blood vessels in many cases of AD. A substantial proportion of the Aβ that accumulates in the AD brain is deposited as Amyloid, which is highly insoluble, proteinaceous material with a β-pleated-sheet conformation and deposited extracellularly in the form of 5-10 nm wide straight fibrils. As γ-secretase catalyzes the final cleavage that releases the Aβ42 or 40 from amyloid β -protein precursor (APP), therefore, it is a potential therapeutic target for the treatment of AD. γ-Secretase cleavage is performed by a high molecular weight protein complex containing presenilins (PSs), nicastrin, Aph-1 and Pen-2. Previous studies have demonstrated that the presenilins (PS1 and PS2) are critical components of a large enzyme complex that performs γ-secretase cleavage. Methods In this study we used RNA interference (RNAi) technology to examine the effects of small-interfering RNA (siRNA) against PS1 on expression levels of PS1 and Aβ42 in IMR-32 Cells using RTPCR, western blotting and immunofluorescence techniques. Results The results of the present study showed down regulation of PS1 and Aβ42 in IMR32 cells transfected with siRNA against PS1. Conclusion Our results substantiate the concept that PS1 is involved in γ-secretase activity and provides the rationale for therapeutic strategies aimed at influencing Aβ42 production.
Collapse
Affiliation(s)
- Ramesh J L Kandimalla
- Department of Biochemistry, Post Graduate Institute of Medical Education and Research, Chandigarh, India
| | | | | | | |
Collapse
|
6
|
Prostate apoptosis response 4 (Par-4), a novel substrate of caspase-3 during apoptosis activation. Mol Cell Biol 2011; 32:826-39. [PMID: 22184067 DOI: 10.1128/mcb.06321-11] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prostate apoptosis response 4 (Par-4) is a ubiquitously expressed proapoptotic tumor suppressor protein. Here, we show for the first time, that Par-4 is a novel substrate of caspase-3 during apoptosis. We found that Par-4 is cleaved during cisplatin-induced apoptosis in human normal and cancer cell lines. Par-4 cleavage generates a C-terminal fragment of ~25 kDa, and the cleavage of Par-4 is completely inhibited by a caspase-3 inhibitor, suggesting that caspase-3 is directly involved in the cleavage of Par-4. Caspase-3-deficient MCF-7 cells do not show Par-4 cleavage in response to cisplatin treatment, and restoration of caspase-3 in MCF-7 cells produces a decrease in Par-4 levels, with the appearance of a cleaved fragment. Additionally, knockdown of Par-4 reduces caspase-3 activation and apoptosis induction. Site-directed mutagenesis reveals that Par-4 cleavage by caspase-3 occurs at an unconventional site, EEPD(131)↓G. Interestingly, overexpression of wild-type Par-4 but not the Par-4 D131A mutant sensitizes cells to cisplatin-induced apoptosis. Upon caspase-3 cleavage, the cleaved fragment of Par-4 accumulates in the nucleus and displays increased apoptotic activity. Overexpression of the cleaved fragment of Par-4 inhibits IκBα phosphorylation and blocks NF-κB nuclear translocation. We have identified a novel specific caspase-3 cleavage site in Par-4, and the cleaved fragment of Par-4 retains proapoptotic activity.
Collapse
|
7
|
Abstract
Melatonin plays a neuroprotective role in models of neurodegenerative diseases. However, the molecular mechanisms underlying neuroprotection by melatonin are not well understood. Apoptotic cell death in the central nervous system is a feature of neurodegenerative diseases. The intrinsic and extrinsic apoptotic pathways and the antiapoptotic survival signal pathways play critical roles in neurodegeneration. This review summarizes the reports to date showing inhibition by melatonin of the intrinsic apoptotic pathways in neurodegenerative diseases including stroke, Alzheimer disease, Parkinson disease, Huntington disease, and amyotrophic lateral sclerosis. Furthermore, the activation of survival signal pathways by melatonin in neurodegenerative diseases is discussed.
Collapse
Affiliation(s)
- Xin Wang
- Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
8
|
Koryakina A, Aeberhard J, Kiefer S, Hamburger M, Küenzi P. Regulation of secretases by all-trans-retinoic acid. FEBS J 2009; 276:2645-55. [DOI: 10.1111/j.1742-4658.2009.06992.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
|
9
|
Abstract
Par-4 is a tumor suppressor protein with a pro-apoptotic function. Epigenetic silencing of Par-4 is seen in diverse tumors and Par-4 knockout mice develop spontaneous tumors in various tissues. Endogenous Par-4 is essential for sensitization of cells to diverse apoptotic stimuli, whereas ectopic expression of Par-4 can selectively induce apoptosis in cancer cells. The cancer-specific pro-apoptotic action of Par-4 resides in its centrally located SAC domain. This review emphasizes the role of Par-4/SAC in apoptosis and tumor resistance. SAC transgenic mice display normal development and life span, and, most importantly, are resistant to spontaneous, as well as oncogene-induced, autochthonous tumors. The tumor resistant phenotype and undetectable toxicity of SAC in vivo suggests the SAC domain possesses tremendous therapeutic potential.
Collapse
Affiliation(s)
- Yanming Zhao
- Department of Radiation Medicine, University of Kentucky, Lexington, Kentucky 40536, USA
| | | |
Collapse
|
10
|
Tsirigotis M, Baldwin RM, Tang MY, Lorimer IAJ, Gray DA. Activation of p38MAPK contributes to expanded polyglutamine-induced cytotoxicity. PLoS One 2008; 3:e2130. [PMID: 18461158 PMCID: PMC2330164 DOI: 10.1371/journal.pone.0002130] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Accepted: 03/27/2008] [Indexed: 01/30/2023] Open
Abstract
Background The signaling pathways that may modulate the pathogenesis of diseases induced by expanded polyglutamine proteins are not well understood. Methodologies/Principal Findings Herein we demonstrate that expanded polyglutamine protein cytotoxicity is mediated primarily through activation of p38MAPK and that the atypical PKC iota (PKCι) enzyme antagonizes polyglutamine-induced cell death through induction of the ERK signaling pathway. We show that pharmacological blockade of p38MAPK rescues cells from polyglutamine-induced cell death whereas inhibition of ERK recapitulates the sensitivity observed in cells depleted of PKCι by RNA interference. We provide evidence that two unrelated proteins with expanded polyglutamine repeats induce p38MAPK in cultured cells, and demonstrate induction of p38MAPK in an in vivo model of neurodegeneration (spinocerebellar ataxia 1, or SCA-1). Conclusions/Significance Taken together, our data implicate activated p38MAPK in disease progression and suggest that its inhibition may represent a rational strategy for therapeutic intervention in the polyglutamine disorders.
Collapse
Affiliation(s)
- Maria Tsirigotis
- Centre for Cancer Therapeutics, Ottawa Health Research Institute, Ottawa, Ontario, Canada
| | - R. Mitchell Baldwin
- Centre for Cancer Therapeutics, Ottawa Health Research Institute, Ottawa, Ontario, Canada
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - Matthew Y. Tang
- Centre for Cancer Therapeutics, Ottawa Health Research Institute, Ottawa, Ontario, Canada
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - Ian A. J. Lorimer
- Centre for Cancer Therapeutics, Ottawa Health Research Institute, Ottawa, Ontario, Canada
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - Douglas A. Gray
- Centre for Cancer Therapeutics, Ottawa Health Research Institute, Ottawa, Ontario, Canada
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada
- * E-mail:
| |
Collapse
|
11
|
Tesco G, Koh YH, Kang E, Cameron A, Das S, Sena-Esteves M, Hiltunen M, Yang SH, Zhong Z, Shen Y, Simpkins J, Tanzi RE. Depletion of GGA3 stabilizes BACE and enhances beta-secretase activity. Neuron 2007; 54:721-37. [PMID: 17553422 PMCID: PMC1973166 DOI: 10.1016/j.neuron.2007.05.012] [Citation(s) in RCA: 288] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Revised: 04/27/2007] [Accepted: 05/03/2007] [Indexed: 11/16/2022]
Abstract
Beta-site APP-cleaving enzyme (BACE) is required for production of the Alzheimer's disease (AD)-associated Abeta protein. BACE levels are elevated in AD brain, and increasing evidence reveals BACE as a stress-related protease that is upregulated following cerebral ischemia. However, the molecular mechanism responsible is unknown. We show that increases in BACE and beta-secretase activity are due to posttranslational stabilization following caspase activation. We also found that during cerebral ischemia, levels of GGA3, an adaptor protein involved in BACE trafficking, are reduced, while BACE levels are increased. RNAi silencing of GGA3 also elevated levels of BACE and Abeta. Finally, in AD brain samples, GGA3 protein levels were significantly decreased and inversely correlated with increased levels of BACE. In summary, we have elucidated a GGA3-dependent mechanism regulating BACE levels and beta-secretase activity. This mechanism may explain increased cerebral levels of BACE and Abeta following cerebral ischemia and existing in AD.
Collapse
Affiliation(s)
- Giuseppina Tesco
- Genetics and Aging Research Unit, Massachusetts General Hospital, Charlestown, MA 02129
- To whom correspondence should be addressed: Giuseppina Tesco, Genetics and Aging Research Unit, Massachusetts General Hospital, Building 114, 16 Street C3900, Charlestown, MA, 02129-4404, Tel: (617) 724 9850, Fax: (617) 724 1823, ; Rudolph E. Tanzi, Genetics and Aging Research Unit, Massachusetts General Hospital, Building 114, 16 Street C3009, Charlestown, MA, 02129-4404, Tel: (617) 726 6845, Fax: (617) 724 1949,
| | - Young Ho Koh
- Genetics and Aging Research Unit, Massachusetts General Hospital, Charlestown, MA 02129
| | - Eugene Kang
- Genetics and Aging Research Unit, Massachusetts General Hospital, Charlestown, MA 02129
| | - Andrew Cameron
- Genetics and Aging Research Unit, Massachusetts General Hospital, Charlestown, MA 02129
| | - Shinjita Das
- Genetics and Aging Research Unit, Massachusetts General Hospital, Charlestown, MA 02129
| | - Miguel Sena-Esteves
- Neuroscience Center at Massachusetts General Hospital, Charlestown, MA 02129
| | - Mikko Hiltunen
- Genetics and Aging Research Unit, Massachusetts General Hospital, Charlestown, MA 02129
| | - Shao-Hua Yang
- Department of Pharmacology & Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107
| | - Zhenyu Zhong
- Sun Health Research Institute, Sun City, AZ, USA
| | - Yong Shen
- Sun Health Research Institute, Sun City, AZ, USA
| | - James Simpkins
- Department of Pharmacology & Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107
| | - Rudolph E. Tanzi
- Genetics and Aging Research Unit, Massachusetts General Hospital, Charlestown, MA 02129
- To whom correspondence should be addressed: Giuseppina Tesco, Genetics and Aging Research Unit, Massachusetts General Hospital, Building 114, 16 Street C3900, Charlestown, MA, 02129-4404, Tel: (617) 724 9850, Fax: (617) 724 1823, ; Rudolph E. Tanzi, Genetics and Aging Research Unit, Massachusetts General Hospital, Building 114, 16 Street C3009, Charlestown, MA, 02129-4404, Tel: (617) 726 6845, Fax: (617) 724 1949,
| |
Collapse
|
12
|
Xie J, Guo Q. Apoptosis antagonizing transcription factor protects renal tubule cells against oxidative damage and apoptosis induced by ischemia-reperfusion. J Am Soc Nephrol 2006; 17:3336-46. [PMID: 17065240 DOI: 10.1681/asn.2006040311] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Apoptosis antagonizing transcription factor (AATF) is a leucine zipper domain-containing protein that has antiapoptotic properties. AATF is expressed in several organs and tissues, including the kidney. AATF may participate in inhibition of proapoptotic pathways and/or activation of antiapoptotic pathways. Ischemia/reperfusion-induced renal injury (IRI) is clinically important because it typically damages renal tubular epithelial cells and glomerular cells and is the most common cause of acute renal failure. It now is reported that AATF is expressed in human kidney proximal tubule (HK-2) cells and in mouse primary renal tubule epithelial cells. Levels of AATF expression were altered significantly in these cells in a well-established in vitro model of renal IRI. In transfected HK-2 cells, RNA interference-mediated silencing of AATF exacerbated whereas overexpression of the full-length AATF ameliorated mitochondrial dysfunction, accumulation of superoxide and peroxynitrite, lipid peroxidation, caspase-3 activation, and apoptotic death that were induced by IRI. In primary renal tubule epithelial cells, overexpression of AATF mediated by recombinant adeno-associated virus (AAV) vectors resulted in significant antiapoptotic activity, whereas knockdown of AATF by small interference RNA led to exacerbated cell death after IRI. These results identify AATF as a novel cytoprotective factor against oxidative and apoptotic damage in renal tubular cells. AATF may represent a potential candidate for therapeutic application in IRI.
Collapse
Affiliation(s)
- Jun Xie
- Department of Physiology, The University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73104, USA
| | | |
Collapse
|
13
|
Michel V, Yuan Z, Ramsubir S, Bakovic M. Choline transport for phospholipid synthesis. Exp Biol Med (Maywood) 2006; 231:490-504. [PMID: 16636297 DOI: 10.1177/153537020623100503] [Citation(s) in RCA: 230] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Choline is an essential nutrient for all cells because it plays a role in the synthesis of the membrane phospholipid components of the cell membranes, as a methyl-group donor in methionine metabolism as well as in the synthesis of the neurotransmitter acetylcholine. Choline deficiency affects the expression of genes involved in cell proliferation, differentiation, and apoptosis, and it has been associated with liver dysfunction and cancer. Abnormal choline transport and metabolism have been implicated in a number of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. Therefore, the study of choline transport and the characteristics of choline transporters are of central importance to understanding the mechanisms that underlie membrane integrity and cell signaling in such disorders. Kinetic studies with radiolabeled choline and inhibitors distinguish three systems for choline transport: (i) low-affinity facilitated diffusion, (ii) high-affinity, Na+-dependent transport, and (iii) intermediate-affinity, Na+-independent transport. It is only recently, however, that the proteins having transport characteristics of at least one of these systems have been identified. They include (i) polyspecific organic cation transporters (OCTs) with low affinity for choline, (ii) high-affinity choline transporters (CHT1s), and (iii) intermediate-affinity choline transporter-like (CTL1) proteins. CHT1 and CTL1 but not OCT transporters are selectively inhibited with hemicholinium-3 and essentially display characteristics of specialized transporters for targeted choline metabolism. CHT1 is abundant in neurons and almost exclusively supplies choline for acetyl-choline synthesis. The focus here is more on newly-discovered CTL1 choline transporters. They are expressed in different organisms and cell types, apparently not for the biosynthesis of acetylcholine but for the production of the most abundant metabolite of choline, the membrane lipid phosphatidylcholine.
Collapse
Affiliation(s)
- Vera Michel
- Department of Human Health and Nutritional Sciences, Animal Science and Nutrition Building, Rm. 346, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | | | | | | |
Collapse
|
14
|
Feng Z, Zhang JT. Long-term melatonin or 17beta-estradiol supplementation alleviates oxidative stress in ovariectomized adult rats. Free Radic Biol Med 2005; 39:195-204. [PMID: 15964511 DOI: 10.1016/j.freeradbiomed.2005.03.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2004] [Revised: 02/25/2005] [Accepted: 03/07/2005] [Indexed: 01/11/2023]
Abstract
Melatonin is an endogenously generated potent antioxidant. Our previous results indicated that melatonin improved learning and memory deficits in the transgenic mouse model of Alzheimer's disease (AD) and ovariectomized (OVX) rats by improving cholinergic nerve system dysfunction, preventing apoptosis. In this study we aim to investigate the antioxidative effects of melatonin or estradiol in the brains of ovariectomized rats. OVX Sprague-Dawley rats received daily injections of melatonin (5, 10, or 20 mg/kg), 17beta-estradiol (80 microg/kg), or sesame oil for 16 weeks. We found an increase in brain mitochondrial thiobarbituric acid-reactive substances (TBARS) levels, a decrease in mitochondrial glutathione (GSH) content as well as mitochondrial superoxide dismutase (SOD) activity and upregulation of the apoptotic-related factors, such as Bax, Caspase-3, and Prostate apoptosis response-4 (Par-4) in the frontal cortex of OVX rats. In addition to oxidative stress, OVX also caused decreased activities of mitochondrial respiration complex I and complex IV, which implicated mitochondrial dysfunction. Melatonin or 17beta-estradiol antagonized the detrimental effects induced by OVX. Furthermore, immunohistochemistry results revealed that the abnormal upregulation of the apoptotic related factor such as Bax, Caspase-3, and (Par-4) greatly reduced expression after melatonin or 17beta-estradiol supplement action. These findings demonstrate the important effects of melatonin or 17beta-estradiol on postmenopausal neuropathy and support the potential application of melatonin in the treatment of dementia in postmenopausal women. Early, long-term melatonin application is a promising strategy which could potentially be applied in a clinical setting.
Collapse
Affiliation(s)
- Zheng Feng
- Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences, Peking Union Medical College, No.1 Xiannong Tan Street, Beijing 10050, People's Republic of China
| | | |
Collapse
|
15
|
Xie J, Guo Q. PAR-4 is involved in regulation of beta-secretase cleavage of the Alzheimer amyloid precursor protein. J Biol Chem 2005; 280:13824-32. [PMID: 15671026 DOI: 10.1074/jbc.m411933200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mounting evidence indicates that aberrant production and aggregation of amyloid beta-peptide (Abeta)-(1-42) play a central role in the pathogenesis of Alzheimer disease (AD). Abeta is produced when amyloid precursor protein (APP) is cleaved by beta- and gamma-secretases at the N and C termini of the Abeta domain, respectively. The beta-secretase is membrane-bound aspartyl protease, most commonly known as BACE1. Because BACE1 cleaves APP at the N terminus of the Abeta domain, it catalyzes the first step in Abeta generation. PAR-4 (prostate apoptosis response-4) is a leucine zipper protein that was initially identified to be associated with neuronal degeneration and aberrant Abeta production in models of AD. We now report that the C-terminal domain of PAR-4 is necessary for forming a complex with the cytosolic tail of BACE1 in co-immunoprecipitation assays and in vitro pull-down experiments. Overexpression of PAR-4 significantly increased, whereas silencing of PAR-4 expression by RNA interference significantly decreased, beta-secretase cleavage of APP. These results suggest that PAR-4 may be directly involved in regulating the APP cleavage activity of BACE1. Because the increased BACE1 activity observed in AD patients does not seem to arise from genetic mutations or polymorphisms in BACE1, the identification of PAR-4 as an endogenous regulator of BACE1 activity may have significant implications for developing novel therapeutic strategies for AD.
Collapse
Affiliation(s)
- Jun Xie
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | | |
Collapse
|
16
|
Abstract
Evidence from human amyotrophic lateral sclerosis (ALS) patients and ALS-linked Cu/Zn superoxide dismutase (Cu/Zn-SOD) transgenic mice bearing the mutation of glycine to alanine at position 93 (G93A) suggests that the pro-apoptotic protein prostate apoptosis response-4 (Par-4) might be a critical link in the chain of events leading to motor neuron degeneration. We now report that Par-4 is enriched in synaptosomes and post-synaptic density from the ventral horn of the spinal cord. Levels of Par-4 in synaptic compartments increased significantly during rapid and slow declining stages of muscle strength in hSOD1 G93A mutant mice. In the pre-muscle weakness stage, hSOD1 G93A mutation sensitized synaptosomes from the ventral horn of the spinal cord to increased levels of Par-4 expression following excitotoxic and apoptotic insults. In ventral spinal synaptosomes, Par-4-mediated production of pro-apoptotic cytosolic factor(s) was significantly enhanced by the hSOD1 G93A mutation. RNA interference (RNAi) knockdown of Par-4 inhibited mitochondrial dysfunction and caspase-3 activation induced by G93A mutation in synaptosomes from the ventral horn of the spinal cord, and protected spinal motor neurons from apoptosis. These results identify the synapse as a crucial cellular site for the cell death promoting actions of Par-4 in motor neurons, and suggest that targeted inhibition of Par-4 by RNAi may prove to be a neuroprotective strategy for motor neuron degeneration.
Collapse
Affiliation(s)
- Jun Xie
- Department of Physiology, the University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | | | | |
Collapse
|
17
|
Xie J, Guo Q. AATF protects neural cells against oxidative damage induced by amyloid beta-peptide. Neurobiol Dis 2004; 16:150-7. [PMID: 15207272 DOI: 10.1016/j.nbd.2004.02.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2003] [Revised: 01/29/2004] [Accepted: 02/12/2004] [Indexed: 01/30/2023] Open
Abstract
Extensive loss of neurons and synapses in vulnerable regions of the brain is one of the most important pathological features of Alzheimer's disease (AD). Increased oxidative stress has been shown to contribute to the neurodegenerative process in AD. Aggregation of amyloid beta-peptide (Abeta) in amyloid plaques is one of the defining features of Alzheimer's disease. Indeed, Abeta has been shown to induce oxidative stress and apoptosis in many in vivo and in vitro models of AD. We now report that AATF (apoptosis-antagonizing transcription factor), a leucine zipper protein initially identified as an interaction partner of DAP like kinase (Dlk, a member of the pro-apoptotic Death-Associated Protein kinase family), is expressed in cortical neurons and in neural PC12 cells. Abeta induces alterations in AATF expression in cortical neurons. Inhibition of AATF induction sensitizes neurons to Abeta toxicity. Overexpression of AATF suppressed superoxide production, inhibited peroxynitrite formation and membrane lipid peroxidation, and protected against Abeta-induced apoptosis in PC12 cells. These results suggest that AATF is a novel neuroprotective factor and it may protect against Abeta-induced apoptosis through its effects on suppressing the production of reactive oxygen species (ROS). AATF may therefore represent a potential candidate for therapeutic intervention of neurodegeneration in both sporadic and familial forms of AD.
Collapse
Affiliation(s)
- Jun Xie
- Department of Physiology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | | |
Collapse
|
18
|
Xie J, Guo Q. Par-4 Inhibits Choline Uptake by Interacting with CHT1 and Reducing Its Incorporation on the Plasma Membrane. J Biol Chem 2004; 279:28266-75. [PMID: 15090548 DOI: 10.1074/jbc.m401495200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CHT1 is a Na(+)- and Cl(-)-dependent, hemicholinium-3 (HC-3)-sensitive, high affinity choline transporter. Par-4 (prostate apoptosis response-4) is a leucine zipper protein involved in neuronal degeneration and cholinergic signaling in Alzheimer's disease. We now report that Par-4 is a negative regulator of CHT1 choline uptake activity. Transfection of neural IMR-32 cells with human CHT1 conferred Na(+)-dependent, HC-3-sensitive choline uptake that was effectively inhibited by cotransfection of Par-4. Mapping studies indicated that the C-terminal half of Par-4 was physically involved in interacting with CHT1, and the absence of Par-4.CHT1 complex formation precluded the loss of CHT1-mediated choline uptake induced by Par-4, indicating that Par-4.CHT1 complex formation is essential. Kinetic and cell-surface biotinylation assays showed that Par-4 inhibited CHT1-mediated choline uptake by reducing CHT1 expression in the plasma membrane without significantly altering the affinity of CHT1 for choline or HC-3. These results suggest that Par-4 is directly involved in regulating choline uptake by interacting with CHT1 and by reducing its incorporation on the cell surface.
Collapse
Affiliation(s)
- Jun Xie
- Department of Physiology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73104, USA
| | | |
Collapse
|
19
|
Romano A, Serafino A, Krasnowska E, Ciotti MT, Calissano P, Ruberti F, Galli C. Neuronal fibrillogenesis: amyloid fibrils from primary neuronal cultures impair long-term memory in the crab Chasmagnathus. Behav Brain Res 2004; 147:73-82. [PMID: 14659572 DOI: 10.1016/s0166-4328(03)00118-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amyloid beta protein (Abeta) fibrillogenesis is considered one of the crucial steps of Alzheimer's disease (AD) pathogenesis. The effect of endogenous neuronal amyloid fibrils on memory processes is unknown. To investigate this issue, we first characterised the Abeta fibrillar aggregates secreted by cerebellar granule cells and then we evaluated the effect of neuronal fibrils on an invertebrate model of memory. An increase of fibril formation, assessed by Thioflavin T (ThT) fluorescence, was observed in the conditioned medium of apoptotic neurons during 48 h of the apoptotic process. Moreover, the depolarisation-stimulated secretion of cerebellar granule cells contains monomers of endogenous Abeta, which undergo cell-free fibrillogenesis over several days of incubation. The pattern of single endogenous fibrils, examined by electron microscopy, was similar to that of synthetic Abeta while a tighter and more complex interfibrillar organization was observed in endogenous fibrils. The biological effect of neuronal fibrils was studied in a long-term memory (LTM) paradigm, namely the context-signal learning of the crab Chasmagnathus. Pre-training injection of neuronal fibril extract (protein concentration, 1 microg/ml) induced amnesia in a dose-dependent manner. On the contrary, no effect on retention was observed with the administration of two orders higher doses (100 microg/ml) of synthetic Abeta1-40. These results indicate that only naturally secreted fibrils, but not synthetic Abeta, clearly interfere with memory process.
Collapse
Affiliation(s)
- Arturo Romano
- Laboratorio de Neurobiología de la Memoria, Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428, Argentina
| | | | | | | | | | | | | |
Collapse
|
20
|
Guo Q, Xie J. AATF Inhibits Aberrant Production of Amyloid β Peptide 1-42 by Interacting Directly with Par-4. J Biol Chem 2004; 279:4596-603. [PMID: 14627703 DOI: 10.1074/jbc.m309811200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Aggregation of the neurotoxic amyloid beta peptide 1-42 (Abeta-(1-42)) in the brain is considered to be an early event in the pathogenesis of Alzheimer's disease (AD). Par-4 (prostate apoptosis response-4) is a leucine zipper protein that is pro-apoptotic and associated with neuronal degeneration in AD. Overexpression of Par-4 significantly increased production of Abeta-(1-42) after initiation of apoptotic cascades, indicating factors regulating apoptotic pathways may also affect processing of beta-amyloid precursor protein (APP). AATF (apoptosis-antagonizing transcription factor) was recently identified as an interaction partner of DAP-like kinase (Dlk), a member of the DAP (death-associated protein) kinase family. AATF antagonizes apoptosis induced by Par-4, suggesting that AATF might directly or indirectly participate in regulation of Par-4 activity. We now report that AATF colocalizes with Par-4 in both cytoplasmic and nuclear compartments, and it interacts directly and selectively with Par-4 via the leucine zipper domain in neural cells. Par-4 induced an aberrant production and secretion of Abeta in neuroblastoma IMR-32 cells after apoptotic cascades are initiated. Co-expression of AATF completely blocked aberrant production and secretion of Abeta-(1-42) induced by Par-4, and AATF/Par-4 complex formation was essential for the inhibitory effect of AATF on aberrant Abeta secretion. These results indicate that AATF is an endogenous antagonist of Par-4 activity and an effective inhibitor of aberrant Abeta production and secretion under apoptotic conditions.
Collapse
Affiliation(s)
- Qing Guo
- Department of Physiology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
| | | |
Collapse
|
21
|
Abstract
In dividing cells, cyclin-dependent kinases (Cdks) are cell cycle-associated protein kinases that regulate proliferation, differentiation, senescence, and apoptosis. In neurons that no longer divide, deregulation of Cdks, especially Cdk5, occurs in many neurological disorders, including Alzheimer's disease (AD) and Parkinson's disease (PD). Cdk5 is a unique member of the Cdk family because it does not play a critical role in cell cycle progression, and it is not activated by a cyclin. Instead, Cdk5 normally is activated by the regulatory protein p35. This Cdk5/p35 activity has emerged as an important regulator of proper development of the mammalian central nervous system. In vitro studies suggest that aberrant activation of Cdk5 by an endogenous truncated version (p25) of p35 might be a key event in the process of neurodegeneration. One enzyme responsible for cleavage of p35 to form p25 is calpain, a calcium-activated protease that has been shown to be involved in neuronal cell death. Recent studies provided important in vivo evidence that hyperactivation and redistribution of Cdk5 by p25 plays an essential role in the phosphorylation of "pathological" substrates (such as tau) and the cell death of neurons in experimental models of AD and PD. Because amyloid beta peptide, the primary neurotoxic component of amyloid plaques in AD, has been shown to increase the conversion of p35 to p25, aberrant activation of Cdk5 by p25 might be a pathway connecting amyloid beta toxicity to tau hyperphosphorylation in AD.
Collapse
Affiliation(s)
- Qing Guo
- Department of Physiology, University of Oklahoma Health Sciences Center, College of Medicine, Oklahoma City, OK 73104, USA.
| |
Collapse
|
22
|
Abstract
Prostate apoptosis response-4 (par-4) is a pro-apoptotic gene identified in prostate cancer cells undergoing apoptosis. Par-4 protein, which contains a leucine zipper domain at the carboxy-terminus, functions as a transcriptional repressor in the nucleus. Par-4 selectively induces apoptosis in androgen-independent prostate cancer cells and Ras-transformed cells but not in androgen-dependent prostate cancer cells or normal cells. Cells that are resistant to apoptosis by Par-4 alone, however, are greatly sensitized by Par-4 to the action of other pro-apoptotic insults such as growth factor withdrawal, tumor necrosis factor, ionizing radiation, intracellular calcium elevation, or those involved in neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, and stroke. Apoptosis induction by Par-4 involves a complex mechanism that requires activation of the Fas death receptor signaling pathway and coparallel inhibition of cell survival NF-kappaB transcription activity. The unique ability of Par-4 to induce apoptosis in cancer cells but not normal cells and the ability of Par-4 antisense or dominant-negative mutant to abrogate apoptosis in neurodegenerative disease paradigms makes it an appealing candidate for molecular therapy of cancer and neuronal diseases.
Collapse
Affiliation(s)
- Nadia El-Guendy
- Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, KY 40536, USA
| | | |
Collapse
|
23
|
Xie J, Chang X, Zhang X, Guo Q. Aberrant induction of Par-4 is involved in apoptosis of hippocampal neurons in presenilin-1 M146V mutant knock-in mice. Brain Res 2001; 915:1-10. [PMID: 11578614 DOI: 10.1016/s0006-8993(01)02803-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Mutations in presenilin-1 (PS-1) have been shown to increase neuronal vulnerability to apoptosis in Alzheimer's disease (AD). Par-4 is a novel cell-death-promoting protein associated with neuronal degeneration in AD. We previously reported that, in transfected PC12 cells, Par-4 seems to be involved in the neurodegenerative mechanisms of PS-1 mutations. However, direct evidence for a necessary role of Par-4 in the pathogenic mechanisms of PS-1 mutations in neurons is lacking. We recently generated and characterized presenilin-1 mutant M146V knock-in (PS-1 M146V KI) mice. We now report that expression of the mutant presenilin-1 in these mice induces early and exaggerated increase in Par-4 expression in hippocampal neurons following glucose deprivation (an insult relevant to the pathogenesis of AD). Importantly, inhibition of Par-4 expression by antisense par-4 oligonucleotide treatment counteracts neuronal apoptosis promoted by M146V mutation of PS-1. Mitochondrial dysfunction and caspase-3 activity induced by glucose deprivation was significantly exacerbated in hippocampal neurons expressing the mutant PS-1. Antisense par-4 treatment largely suppressed the adverse effect of the mutant PS-1 on mitochondrial dysfunction and caspase activation. These results provide evidence in hippocampal neurons that Par-4 is involved in the neurodegenerative cascades associated with PS-1 M146V mutation by acting relatively early in the apoptotic process before mitochondrial dysfunction and caspase-3 activation. Since levels of Par-4 are significantly increased in the hippocampus in human AD brain, the results of this study may provide a significant link between aberrant induction of Par-4 and the neurodegenerative cascades promoted by PS-1 mutations in AD.
Collapse
Affiliation(s)
- J Xie
- Department of Neurobiology and Pharmacology, Northeastern Ohio Universities College of Medicine, 4209 State Route 44, P.O. Box 95, Rootstown, OH 44272-0095, USA
| | | | | | | |
Collapse
|