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Zhou M, Tang J, Fan J, Wen X, Shen J, Jia R, Chai P, Fan X. Recent progress in retinoblastoma: Pathogenesis, presentation, diagnosis and management. Asia Pac J Ophthalmol (Phila) 2024; 13:100058. [PMID: 38615905 DOI: 10.1016/j.apjo.2024.100058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 03/05/2024] [Accepted: 03/08/2024] [Indexed: 04/16/2024] Open
Abstract
Retinoblastoma, the primary ocular malignancy in pediatric patients, poses a substantial threat to mortality without prompt and effective management. The prognosis for survival and preservation of visual acuity hinges upon the disease severity at the time of initial diagnosis. Notably, retinoblastoma has played a crucial role in unraveling the genetic foundations of oncogenesis. The process of tumorigenesis commonly begins with the occurrence of biallelic mutation in the RB1 tumor suppressor gene, which is then followed by a cascade of genetic and epigenetic alterations that correspond to the clinical stage and pathological features of the tumor. The RB1 gene, recognized as a tumor suppressor, encodes the retinoblastoma protein, which plays a vital role in governing cellular replication through interactions with E2F transcription factors and chromatin remodeling proteins. The diagnosis and treatment of retinoblastoma necessitate consideration of numerous factors, including disease staging, germline mutation status, family psychosocial factors, and the resources available within the institution. This review has systematically compiled and categorized the latest developments in the diagnosis and treatment of retinoblastoma which enhanced the quality of care for this pediatric malignancy.
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Affiliation(s)
- Min Zhou
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China
| | - Jieling Tang
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China
| | - Jiayan Fan
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China
| | - Xuyang Wen
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China
| | - Jianfeng Shen
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China
| | - Renbing Jia
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China
| | - Peiwei Chai
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China.
| | - Xianqun Fan
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 20025, People's Republic of China.
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Zhou L, Ng DSC, Yam JC, Chen LJ, Tham CC, Pang CP, Chu WK. Post-translational modifications on the retinoblastoma protein. J Biomed Sci 2022; 29:33. [PMID: 35650644 PMCID: PMC9161509 DOI: 10.1186/s12929-022-00818-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 05/26/2022] [Indexed: 11/21/2022] Open
Abstract
The retinoblastoma protein (pRb) functions as a cell cycle regulator controlling G1 to S phase transition and plays critical roles in tumour suppression. It is frequently inactivated in various tumours. The functions of pRb are tightly regulated, where post-translational modifications (PTMs) play crucial roles, including phosphorylation, ubiquitination, SUMOylation, acetylation and methylation. Most PTMs on pRb are reversible and can be detected in non-cancerous cells, playing an important role in cell cycle regulation, cell survival and differentiation. Conversely, altered PTMs on pRb can give rise to anomalies in cell proliferation and tumourigenesis. In this review, we first summarize recent findings pertinent to how individual PTMs impinge on pRb functions. As many of these PTMs on pRb were published as individual articles, we also provide insights on the coordination, either collaborations and/or competitions, of the same or different types of PTMs on pRb. Having a better understanding of how pRb is post-translationally modulated should pave the way for developing novel and specific therapeutic strategies to treat various human diseases.
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Affiliation(s)
- Linbin Zhou
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Danny Siu-Chun Ng
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Jason C Yam
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China
| | - Li Jia Chen
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China
| | - Clement C Tham
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China
| | - Chi Pui Pang
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China
| | - Wai Kit Chu
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China.
- Hong Kong Hub of Paediatric Excellence, The Chinese University of Hong Kong, Hong Kong, China.
- Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong, China.
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Baicalin Attenuated Aβ1-42-Induced Apoptosis in SH-SY5Y Cells by Inhibiting the Ras-ERK Signaling Pathway. BIOMED RESEARCH INTERNATIONAL 2022; 2022:9491755. [PMID: 35528169 PMCID: PMC9068334 DOI: 10.1155/2022/9491755] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 02/26/2022] [Accepted: 03/28/2022] [Indexed: 11/24/2022]
Abstract
Alzheimer's disease (AD) is a serious neurodegenerative disease. It is widely believed that the accumulation of amyloid beta (Aβ) in neurons around neurofibrillary plaques is the main pathological characteristic of AD; however, the molecular mechanism underlying these pathological changes is not clear. Baicalin is a flavonoid extracted from the dry root of Scutellaria baicalensis Georgi. Studies have shown that baicalin exerts excellent anti-inflammatory and neuroprotective effects. In this study, an AD cell model was established by exposing SH-SY5Y cells to Aβ1-42 and treating them with baicalin. Cell survival, cell cycle progression, and apoptosis were measured by MTT, flow cytometry, and immunofluorescence assays, respectively. The expression levels of Ras, ERK/ERK phosphorylation (p-ERK), and cyclin D1 were measured by Western blotting. In addition, whether the MEK activator could reverse the regulatory effect of baicalin on Ras-ERK signaling was investigated using Western blotting. We found that baicalin improved the survival, promoted the proliferation, and inhibited the apoptosis of SH-SY5Y cells after Aβ1-42 treatment. Baicalin also ameliorated Aβ1-42-induced cell cycle arrest at the S phase and induced apoptosis. Furthermore, baicalin inhibited the levels of Ras, p-ERK, and cyclin D1 induced by Aβ, and this effect could be reversed by the MEK activator. Therefore, we suggest that baicalin may regulate neuronal cell cycle progression and apoptosis in Aβ1-42-treated SH-SY5Y cells by inhibiting the Ras-ERK signaling pathway. This study suggested that baicalin might be a useful therapeutic agent for senile dementia, especially AD.
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Catlin JP, Marziali LN, Rein B, Yan Z, Feltri ML, Schaner Tooley CE. Age-related neurodegeneration and cognitive impairments of NRMT1 knockout mice are preceded by misregulation of RB and abnormal neural stem cell development. Cell Death Dis 2021; 12:1014. [PMID: 34711807 PMCID: PMC8553844 DOI: 10.1038/s41419-021-04316-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 10/07/2021] [Accepted: 10/11/2021] [Indexed: 01/02/2023]
Abstract
N-terminal methylation is an important posttranslational modification that regulates protein/DNA interactions and plays a role in many cellular processes, including DNA damage repair, mitosis, and transcriptional regulation. Our generation of a constitutive knockout mouse for the N-terminal methyltransferase NRMT1 demonstrated its loss results in severe developmental abnormalities and premature aging phenotypes. As premature aging is often accompanied by neurodegeneration, we more specifically examined how NRMT1 loss affects neural pathology and cognitive behaviors. Here we find that Nrmt1-/- mice exhibit postnatal enlargement of the lateral ventricles, age-dependent striatal and hippocampal neurodegeneration, memory impairments, and hyperactivity. These morphological and behavior abnormalities are preceded by alterations in neural stem cell (NSC) development. Early expansion and differentiation of the quiescent NSC pool in Nrmt1-/- mice is followed by its subsequent depletion and many of the resulting neurons remain in the cell cycle and ultimately undergo apoptosis. These cell cycle phenotypes are reminiscent to those seen with loss of the NRMT1 target retinoblastoma protein (RB). Accordingly, we find misregulation of RB phosphorylation and degradation in Nrmt1-/- mice, and significant de-repression of RB target genes involved in cell cycle. We also identify novel de-repression of Noxa, an RB target gene that promotes apoptosis. These data identify Nα-methylation as a novel regulatory modification of RB transcriptional repression during neurogenesis and indicate that NRMT1 and RB work together to promote NSC quiescence and prevent neuronal apoptosis.
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Affiliation(s)
- James P Catlin
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Leandro N Marziali
- Departments of Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, Hunter James Kelly Research Institute, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Benjamin Rein
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Zhen Yan
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - M Laura Feltri
- Departments of Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, Hunter James Kelly Research Institute, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA.
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Lee TK, Kim DW, Lee JC, Park CW, Sim H, Ahn JH, Park JH, Shin MC, Cho JH, Lee CH, Won MH, Choi SY. Changes in Cyclin D1, cdk4, and Their Associated Molecules in Ischemic Pyramidal Neurons in Gerbil Hippocampus after Transient Ischemia and Neuroprotective Effects of Ischemic Preconditioning by Keeping the Molecules in the Ischemic Neurons. BIOLOGY 2021; 10:biology10080719. [PMID: 34439951 PMCID: PMC8389197 DOI: 10.3390/biology10080719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 07/17/2021] [Accepted: 07/23/2021] [Indexed: 11/16/2022]
Abstract
Simple Summary Cyclin D1 and cyclin-dependent kinase 4 (cdk4) is implicated in neuronal death induced by various pathological conditions. Ischemic preconditioning (IPC) confers neuroprotective effect, but underlying mechanisms have been poorly addressed. In this study, IPC protected pyramidal neurons (cells) in gerbil hippocampus after transient ischemia. Additionally, IPC controlled expressions of cyclin D1, cdk4, phosphorylated retinoblastoma (p-Rb), and E2 promoter binding factor 1 (E2F1). In particular, the expression of p16INK4a was not different by IPC. These findings indicate that cyclin D1/cdk4-related signals may play important roles in events in neurons related to damage/death following ischemic insults. Especially, the preservation of p16INK4a by IPC may be crucial in attenuating neuronal death/damage or protecting neurons after brain ischemic insults. Abstract Inadequate activation of cell cycle proteins including cyclin D1 and cdk4 is involved in neuronal cell death induced by diverse pathological stresses, including transient global brain ischemia. The neuroprotective effect of ischemic preconditioning is well-established, but the underlying mechanism is still unknown. In this study, we examined changes in cyclin D1, cdk4, and related molecules in cells or neurons located in Cornu Ammonis 1 (CA1) of gerbil hippocampus after transient ischemia for 5 min (ischemia and reperfusion) and investigated the effects of IPC on these molecules after ischemia. Four groups were used in this study as follows: sham group, ischemia group, IPC plus (+) sham group, and IPC+ischemia group. IPC was developed by inducing 2-min ischemia at 24 h before 5-min ischemia (real ischemia). Most pyramidal cells located in CA1 of the ischemia group died five days after ischemia. CA1 pyramidal cells in the IPC+ischemia group were protected. In the ischemia group, the expressions of cyclin D1, cdk4, phosphorylated retinoblastoma (p-Rb), and E2F1 (a transcription factor regulated by p-Rb) were significantly altered in the pyramidal cells with time after ischemia; in the IPC+ischemia group, they were controlled at the level shown in the sham group. In particular, the expression of p16INK4a (an endogenous cdk inhibitor) in the ischemia group was reversely altered in the pyramidal cells; in the IPC+TI group, the expression of p16INK4a was not different from that shown in the sham group. Our current results indicate that cyclin D1/cdk4-related signals may have important roles in events in neurons related to damage/death following ischemia and reperfusion. In particular, the preservation of p16INK4a by IPC may be crucial in attenuating neuronal death/damage or protecting neurons after brain ischemic insults.
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Affiliation(s)
- Tae-Kyeong Lee
- Department of Biomedical Science and Research Institute of Bioscience and Biotechnology, Hallym University, Chuncheon 24252, Korea;
| | - Dae Won Kim
- Department of Biochemistry and Molecular Biology and Research Institute of Oral Sciences, College of Dentistry, Kangnung-Wonju National University, Gangneung 25457, Korea;
| | - Jae-Chul Lee
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea; (J.-C.L.); (C.W.P.); (H.S.); (J.H.A.)
| | - Cheol Woo Park
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea; (J.-C.L.); (C.W.P.); (H.S.); (J.H.A.)
| | - Hyejin Sim
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea; (J.-C.L.); (C.W.P.); (H.S.); (J.H.A.)
| | - Ji Hyeon Ahn
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea; (J.-C.L.); (C.W.P.); (H.S.); (J.H.A.)
- Department of Physical Therapy, College of Health Science, Youngsan University, Yangsan 50510, Korea
| | - Joon Ha Park
- Department of Anatomy, College of Korean Medicine, Dongguk University, Gyeongju 38066, Korea;
| | - Myoung Cheol Shin
- Department of Emergency Medicine, Kangwon National University Hospital, School of Medicine, Kangwon National University, Chuncheon 24289, Korea; (M.C.S.); (J.H.C.)
| | - Jun Hwi Cho
- Department of Emergency Medicine, Kangwon National University Hospital, School of Medicine, Kangwon National University, Chuncheon 24289, Korea; (M.C.S.); (J.H.C.)
| | - Choong-Hyun Lee
- Department of Pharmacy, College of Pharmacy, Dankook University, Cheonan 31116, Korea;
| | - Moo-Ho Won
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea; (J.-C.L.); (C.W.P.); (H.S.); (J.H.A.)
- Correspondence: (M.-H.W.); (S.Y.C.); Tel.: +82-33-250-8891 (M.-H.W.); +82-33-248-2112 (S.Y.C.); Fax: +82-33-256-1614 (M.-H.W.); +82-33-241-1463 (S.Y.C.)
| | - Soo Young Choi
- Department of Biomedical Science and Research Institute of Bioscience and Biotechnology, Hallym University, Chuncheon 24252, Korea;
- Correspondence: (M.-H.W.); (S.Y.C.); Tel.: +82-33-250-8891 (M.-H.W.); +82-33-248-2112 (S.Y.C.); Fax: +82-33-256-1614 (M.-H.W.); +82-33-241-1463 (S.Y.C.)
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Marlier Q, D'aes T, Verteneuil S, Vandenbosch R, Malgrange B. Core cell cycle machinery is crucially involved in both life and death of post-mitotic neurons. Cell Mol Life Sci 2020; 77:4553-4571. [PMID: 32476056 PMCID: PMC11105064 DOI: 10.1007/s00018-020-03548-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 04/23/2020] [Accepted: 05/12/2020] [Indexed: 12/12/2022]
Abstract
A persistent dogma in neuroscience supported the idea that terminally differentiated neurons permanently withdraw from the cell cycle. However, since the late 1990s, several studies have shown that cell cycle proteins are expressed in post-mitotic neurons under physiological conditions, indicating that the cell cycle machinery is not restricted to proliferating cells. Moreover, many studies have highlighted a clear link between cell cycle-related proteins and neurological disorders, particularly relating to apoptosis-induced neuronal death. Indeed, cell cycle-related proteins can be upregulated or overactivated in post-mitotic neurons in case of acute or degenerative central nervous system disease. Given the considerable lack of effective treatments for age-related neurological disorders, new therapeutic approaches targeting the cell cycle machinery might thus be considered. This review aims at summarizing current knowledge about the role of the cell cycle machinery in post-mitotic neurons in healthy and pathological conditions.
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Affiliation(s)
- Quentin Marlier
- Developmental Neurobiology Unit, GIGA Stem Cells/Neurosciences, University of Liège, Quartier Hopital (CHU), Avenue Hippocrate, 15, 4000, Liege, Belgium
| | - Tine D'aes
- Developmental Neurobiology Unit, GIGA Stem Cells/Neurosciences, University of Liège, Quartier Hopital (CHU), Avenue Hippocrate, 15, 4000, Liege, Belgium
| | - Sébastien Verteneuil
- Developmental Neurobiology Unit, GIGA Stem Cells/Neurosciences, University of Liège, Quartier Hopital (CHU), Avenue Hippocrate, 15, 4000, Liege, Belgium
| | - Renaud Vandenbosch
- Developmental Neurobiology Unit, GIGA Stem Cells/Neurosciences, University of Liège, Quartier Hopital (CHU), Avenue Hippocrate, 15, 4000, Liege, Belgium
| | - Brigitte Malgrange
- Developmental Neurobiology Unit, GIGA Stem Cells/Neurosciences, University of Liège, Quartier Hopital (CHU), Avenue Hippocrate, 15, 4000, Liege, Belgium.
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Joseph C, Mangani AS, Gupta V, Chitranshi N, Shen T, Dheer Y, Kb D, Mirzaei M, You Y, Graham SL, Gupta V. Cell Cycle Deficits in Neurodegenerative Disorders: Uncovering Molecular Mechanisms to Drive Innovative Therapeutic Development. Aging Dis 2020; 11:946-966. [PMID: 32765956 PMCID: PMC7390532 DOI: 10.14336/ad.2019.0923] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 09/23/2019] [Indexed: 12/12/2022] Open
Abstract
Cell cycle dysregulation has been implicated in the pathogenesis of neurodegenerative disorders. Specialised function obligates neuronal cells to subsist in a quiescent state of cell cycle once differentiated and therefore the circumstances and mechanisms underlying aberrant cell cycle activation in post-mitotic neurons in physiological and disease conditions remains an intriguing area of research. There is a strict requirement of concurrence to cell cycle regulation for neurons to ensure intracellular biochemical conformity as well as interrelationship with other cells within neural tissues. This review deliberates on various mechanisms underlying cell cycle regulation in neuronal cells and underscores potential implications of their non-compliance in neural pathology. Recent research suggests that successful duplication of genetic material without subsequent induction of mitosis induces inherent molecular flaws that eventually assert as apoptotic changes. The consequences of anomalous cell cycle activation and subsequent apoptosis are demonstrated by the increased presence of molecular stress response and apoptotic markers. This review delineates cell cycle events under normal physiological conditions and deficits amalgamated by alterations in protein levels and signalling pathways associated with cell-division are analysed. Cell cycle regulators essentially, cyclins, CDKs, cip/kip family of inhibitors, caspases, bax and p53 have been identified to be involved in impaired cell cycle regulation and associated with neural pathology. The pharmacological modulators of cell cycle that are shown to impart protection in various animal models of neurological deficits are summarised. Greater understanding of the molecular mechanisms that are indispensable to cell cycle regulation in neurons in health and disease conditions will facilitate targeted drug development for neuroprotection.
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Affiliation(s)
- Chitra Joseph
- 1Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | | | - Veer Gupta
- 2School of Medicine, Deakin University, Melbourne, VIC, Australia
| | - Nitin Chitranshi
- 1Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Ting Shen
- 1Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Yogita Dheer
- 1Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Devaraj Kb
- 1Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Mehdi Mirzaei
- 3Department of Molecular Sciences, Macquarie University, North Ryde, NSW 2109, Australia
| | - Yuyi You
- 1Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia.,4Save Sight Institute, Sydney University, Sydney, NSW 2109, Australia
| | - Stuart L Graham
- 1Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia.,4Save Sight Institute, Sydney University, Sydney, NSW 2109, Australia
| | - Vivek Gupta
- 1Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
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Aberrant activation of neuronal cell cycle caused by dysregulation of ubiquitin ligase Itch results in neurodegeneration. Cell Death Dis 2020; 11:441. [PMID: 32513985 PMCID: PMC7280246 DOI: 10.1038/s41419-020-2647-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/25/2020] [Accepted: 05/27/2020] [Indexed: 12/15/2022]
Abstract
It is critical for the neuronal cell cycle to remain suppressed in terminally differentiated neurons as its activation results in aberrant cell cycle re-entry that causes neuronal apoptosis (CRNA), which has been observed in several neurodegenerative disorders like Alzheimer's disease (AD). In the present study, we report that E3 ubiquitin ligase Itch is a major regulator of CRNA and elucidated the mechanism via which it is regulated in this process. Neurotoxic amyloid peptide Aβ42-treated neurons or neurons from an AD transgenic mouse model (TgAD) exhibited aberrant activation of the JNK pathway which resulted in the hyperphosphorylation of Itch. The phosphorylation of Itch primes it for autoubiquitination, which is necessary for its activation. These post-translational modifications of Itch facilitate its interaction with TAp73 resulting in its degradation. These series of events are critical for Itch-mediated CRNA and its phosphorylation and autoubiquitination site mutants reversed this process and were neuroprotective. These studies unravel a novel pathway via which neurodegeneration in AD and possibly other related disorders may be regulated by aberrant regulation of the neuronal cell cycle.
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Zhang Y, Song X, Herrup K. Context-Dependent Functions of E2F1: Cell Cycle, Cell Death, and DNA Damage Repair in Cortical Neurons. Mol Neurobiol 2020; 57:2377-2390. [PMID: 32062842 DOI: 10.1007/s12035-020-01887-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 01/29/2020] [Indexed: 01/17/2023]
Abstract
DNA damage has been reported to induce cell cycle-related neuronal death. This is significant as aberrant cell cycle re-entry of mature, post-mitotic neurons contributes to neurodegeneration. In this study, we investigate how DNA damage elicited by exposure to the topoisomerase I inhibitor camptothecin (CPT) leads to cycle-related death of cultured cortical neurons and examine the function of E2F1 in this process. CPT treatment induced cell cycle initiation of cortical neurons and elevated the expression of certain cell cycle components (e.g., cyclin D1, CDK4, E2F1) but failed to drive S phase entry or DNA synthesis. The arrest in the cell cycle is explained by the elevated expression of the CDK inhibitor p21Cip1. Though its level was increased after CPT treatment, E2F1 did not drive treated neurons into the G1-S phase transition. E2F1 overexpression led to cell cycle activation and acute neuronal apoptosis without detectable entry of the neurons into S phase. ChIPseq analysis demonstrated that E2F1 predominantly occupies positions on or near the promoters of cell cycle related genes. Instead, in CPT-treated neurons, E2F1 preferentially regulated DNA repair related genes. Our study reveals that the functions of E2F1 in postmitotic neurons are context-dependent and offers novel insights into the role of E2F1 in DNA damage induced cycle-related neuronal death.
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Affiliation(s)
- Yang Zhang
- Division of Life Science and the State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Xuan Song
- Division of Life Science and the State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Karl Herrup
- Division of Life Science and the State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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Lyu P, Huang Z, Feng Q, Su Y, Zheng M, Hong Y, Cai X, Lu Z. Unveiling the transcriptome alteration of POMC neuron in diet-induced obesity. Exp Cell Res 2020; 389:111848. [PMID: 31954693 DOI: 10.1016/j.yexcr.2020.111848] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/09/2020] [Accepted: 01/11/2020] [Indexed: 01/24/2023]
Abstract
Loss of neuron homeostasis in the arcuate nucleus (ARC) is responsible for diet-induced-obesity (DIO). We previously reported that loss of Rb1 gene compromised the homeostasis of anorexigenic POMC neurons in ARC and induced obesity in mice. To evaluate the development of DIO, we propose to analyze the transcriptomic alteration of POMC neurons in mice following high fat diet (HFD) feeding. We isolated these neurons from established DIO mice and performed transcriptomic profiling using RNA-seq. In total, 1066 genes (628 upregulated and 438 downregulated) were identified as differentially expressed genes (DEGs). Pathway enrichment analysis with these DEGs further revealed that "cell cycle," "apoptosis," "chemokine signaling," and "sphingolipid metabolism" pathways were correlated with DIO development. Moreover, we validated that the pRb protein, a key regulator of "cell cycle pathway," was inactivated by phosphorylation in POMC neurons by HFD feeding. Importantly, the reversal of deregulated cell cycle by stereotaxic delivering of the unphosphorylated pRbΔP in ARC significantly meliorated the DIO. Collectively, our study provides insights into the mechanisms related to the loss of homeostasis of POMC neurons in DIO, and suggests pRb phosphorylation as a potential intervention target to treat DIO.
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Affiliation(s)
- Peng Lyu
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, 350108, China
| | - Zhishun Huang
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, 350108, China
| | - Qingjun Feng
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, 350108, China
| | - Yongfu Su
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, 350108, China
| | - Mengying Zheng
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, 350108, China
| | - Yannv Hong
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, 350108, China
| | - Xiang Cai
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, 350108, China
| | - Zhonglei Lu
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, 350108, China.
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11
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Iqbal N, Zhu LI, Chua SC. Neuronal Cell Cycle Events Link Caloric Intake to Obesity. Trends Endocrinol Metab 2020; 31:46-52. [PMID: 31629614 PMCID: PMC7064044 DOI: 10.1016/j.tem.2019.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 09/03/2019] [Accepted: 09/05/2019] [Indexed: 02/03/2023]
Abstract
Obesity is a neurological disorder that operates by favoring energy storage within adipose depots and increased caloric intake. Most cases of human obesity are acquired without any underlying genetic basis. Here, we suggest that obesity can impair the function of some hypothalamic neurons critical to body weight regulation. Genetic ablation of the retinoblastoma (Rb) gene within pro-opiomelanocortin (POMC) neurons leads to death of the neurons and subsequent obesity. The Rb protein (pRb), a key inhibitor of the cell cycle, can also be inactivated by cyclin dependent kinase (CDK)-mediated phosphorylation. Extensive development led to the production of FDA-approved CDK4/6 inhibitors. Based on our own results, we propose that maintaining or re-instating pRb function using CDK4/6 inhibitors are potentially effective treatments of diet-induced obesity (DIO).
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Affiliation(s)
- Niloy Iqbal
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10462, USA
| | - LIang Zhu
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10462, USA
| | - Streamson C Chua
- Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10462, USA; Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10462, USA.
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12
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Zhao D, Qin XP, Chen SF, Liao XY, Cheng J, Liu R, Lei Y, Zhang ZF, Wan Q. PTEN Inhibition Protects Against Experimental Intracerebral Hemorrhage-Induced Brain Injury Through PTEN/E2F1/β-Catenin Pathway. Front Mol Neurosci 2019; 12:281. [PMID: 31866820 PMCID: PMC6906195 DOI: 10.3389/fnmol.2019.00281] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 11/04/2019] [Indexed: 12/26/2022] Open
Abstract
Intracerebral hemorrhage (ICH) is a subtype of stroke with highest mortality and morbidity. We have previously demonstrated that dipotassium bisperoxo (picolinato) oxovanadate (V), (bpV[pic]) inhibits phosphatase and tensin homolog (PTEN) and activates extracellular signal-regulated kinase (ERK)1/2. In this study, we examined the effect of bpV[pic] in the rat ICH model in vivo and the hemin-induced injury model in rat cortical cultures. The rat model of ICH was created by injecting autologous blood into the striatum, and bpV[pic] was intraperitoneally injected. The effects of bpV[pic] were evaluated by neurological tests, Fluoro-Jade C (FJC) staining, and Nissl staining. We demonstrate that bpV[pic] attenuates ICH-induced brain injury in vivo and hemin-induced neuron injury in vitro. The expression of E2F1 was increased, but β-catenin expression was decreased after ICH, and the altered expressions of E2F1 and β-catenin after ICH were blocked by bpV[pic] treatment. Our results further show that bpV[pic] increases β-catenin expression through downregulating E2F1 in cortical neurons and prevents hemin-induced neuronal damage through E2F1 downregulation and subsequent upregulation of β-catenin. By testing the effect of PTEN-siRNA, PTEN cDNA, or combined use of ERK1/2 inhibitor and bpV[pic] in cultured cortical neurons after hemin-induced injury, we provide evidence suggesting that PTEN inhibition by bpV[pic] confers neuroprotection through E2F1 and β-catenin pathway, but the neuroprotective role of ERK1/2 activation by bpV[pic] cannot be excluded.
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Affiliation(s)
- Dan Zhao
- Department of Physiology, School of Basic Medical Sciences, Hubei University of Medicine, Shiyan, China
| | - Xing-Ping Qin
- Department of Neurosurgery, Renmin Hospital of Wuhan University, Wuhan, China
| | - Song-Feng Chen
- Department of Physiology, Collaborative Innovation Center for Brain Science, School of Basic Medical Sciences, Wuhan University School of Medicine, Wuhan, China
| | - Xin-Yu Liao
- Department of Physiology, Collaborative Innovation Center for Brain Science, School of Basic Medical Sciences, Wuhan University School of Medicine, Wuhan, China
| | - Jing Cheng
- Department of Physiology, Collaborative Innovation Center for Brain Science, School of Basic Medical Sciences, Wuhan University School of Medicine, Wuhan, China
| | - Rui Liu
- Department of Physiology, Collaborative Innovation Center for Brain Science, School of Basic Medical Sciences, Wuhan University School of Medicine, Wuhan, China
| | - Yang Lei
- Department of Physiology, Collaborative Innovation Center for Brain Science, School of Basic Medical Sciences, Wuhan University School of Medicine, Wuhan, China
| | - Zhi-Feng Zhang
- Department of Physiology, School of Basic Medical Sciences, Hubei University of Medicine, Shiyan, China
| | - Qi Wan
- Institute of Neuroregeneration and Neurorehabilitation, Department of Neurosurgery of the Affiliated Hospital, Qingdao University, Qingdao, China
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13
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Huang T, González YR, Qu D, Huang E, Safarpour F, Wang E, Joselin A, Im DS, Callaghan SM, Boonying W, Julian L, Dunwoodie SL, Slack RS, Park DS. The pro-death role of Cited2 in stroke is regulated by E2F1/4 transcription factors. J Biol Chem 2019; 294:8617-8629. [PMID: 30967472 DOI: 10.1074/jbc.ra119.007941] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 03/25/2019] [Indexed: 11/06/2022] Open
Abstract
We previously reported that the cell cycle-related cyclin-dependent kinase 4-retinoblastoma (RB) transcriptional corepressor pathway is essential for stroke-induced cell death both in vitro and in vivo However, how this signaling pathway induces cell death is unclear. Previously, we found that the cyclin-dependent kinase 4 pathway activates the pro-apoptotic transcriptional co-regulator Cited2 in vitro after DNA damage. In the present study, we report that Cited2 protein expression is also dramatically increased following stroke/ischemic insult. Critically, utilizing conditional knockout mice, we show that Cited2 is required for neuronal cell death, both in culture and in mice after ischemic insult. Importantly, determining the mechanism by which Cited2 levels are regulated, we found that E2F transcription factor (E2F) family members participate in Cited2 regulation. First, E2F1 expression induced Cited2 transcription, and E2F1 deficiency reduced Cited2 expression. Moreover, determining the potential E2F-binding regions on the Cited2 gene regulatory sequence by ChIP analysis, we provide evidence that E2F1/4 proteins bind to this DNA region. A luciferase reporter assay to probe the functional outcomes of this interaction revealed that E2F1 activates and E2F4 inhibits Cited2 transcription. Moreover, we identified the functional binding motif for E2F1 in the Cited2 gene promoter by demonstrating that mutation of this site dramatically reduces E2F1-mediated Cited2 transcription. Finally, E2F1 and E2F4 regulated Cited2 expression in neurons after stroke-related insults. Taken together, these results indicate that the E2F-Cited2 regulatory pathway is critically involved in stroke injury.
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Affiliation(s)
- Tianwen Huang
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Department of Neurology, and Fujian Key Laboratory of Molecular Neurology, Fujian Medical University Union Hospital, Fuzhou, 350001 Fujian, China
| | - Yasmilde Rodríguez González
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Dianbo Qu
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Hotchkiss Brain Institute, Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - En Huang
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Farzaneh Safarpour
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Eugene Wang
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Alvin Joselin
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Hotchkiss Brain Institute, Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Doo Soon Im
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Hotchkiss Brain Institute, Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Steve M Callaghan
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Wassamon Boonying
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Lisa Julian
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Sally L Dunwoodie
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia; Faculties of Medicine and Science University of New South Wales, Kensington, New South Wales 2033, Australia
| | - Ruth S Slack
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - David S Park
- University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Hotchkiss Brain Institute, Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
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14
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Tiernan CT, Ginsberg SD, He B, Ward SM, Guillozet-Bongaarts AL, Kanaan NM, Mufson EJ, Counts SE. Pretangle pathology within cholinergic nucleus basalis neurons coincides with neurotrophic and neurotransmitter receptor gene dysregulation during the progression of Alzheimer's disease. Neurobiol Dis 2018; 117:125-136. [PMID: 29859871 PMCID: PMC6278831 DOI: 10.1016/j.nbd.2018.05.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 05/30/2018] [Indexed: 01/22/2023] Open
Abstract
Cholinergic basal forebrain neurons of the nucleus basalis of Meynert (nbM) regulate attentional and memory function and are exquisitely prone to tau pathology and neurofibrillary tangle (NFT) formation during the progression of Alzheimer's disease (AD). nbM neurons require the neurotrophin nerve growth factor (NGF), its cognate receptor TrkA, and the pan-neurotrophin receptor p75NTR for their maintenance and survival. Additionally, nbM neuronal activity and cholinergic tone are regulated by the expression of nicotinic (nAChR) and muscarinic (mAChR) acetylcholine receptors as well as receptors modulating glutamatergic and catecholaminergic afferent signaling. To date, the molecular and cellular relationships between the evolution of tau pathology and nbM neuronal survival remain unknown. To address this knowledge gap, we profiled cholinotrophic pathway genes within nbM neurons immunostained for pS422, a pretangle phosphorylation event preceding tau C-terminal truncation at D421, or dual-labeled for pS422 and TauC3, a later stage tau neo-epitope revealed by this same C-terminal truncation event, via single-population custom microarray analysis. nbM neurons were obtained from postmortem tissues from subjects who died with an antemortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI), or mild/moderate AD. Quantitative analysis revealed significant downregulation of mRNAs encoding TrkA as well as TrkB, TrkC, and the Trk-mediated downstream pro-survival kinase Akt in pS422+ compared to unlabeled, pS422-negative nbM neurons. In addition, pS422+ neurons displayed a downregulation of transcripts encoding NMDA receptor subunit 2B, metabotropic glutamate receptor 2, D2 dopamine receptor, and β1 adrenoceptor. By contrast, transcripts encoding p75NTR were downregulated in dual-labeled pS422+/TauC3+ neurons. Appearance of the TauC3 epitope was also associated with an upregulation of the α7 nAChR subunit and differential downregulation of the β2 nAChR subunit. Notably, we found that gene expression patterns for each cell phenotype did not differ with clinical diagnosis. However, linear regression revealed that global cognition and Braak stage were predictors of select transcript changes within both unlabeled and pS422+/TauC3- neurons. Taken together, these cell phenotype-specific gene expression profiling data suggest that dysregulation of neurotrophic and neurotransmitter signaling is an early pathogenic mechanism associated with NFT formation in vulnerable nbM neurons and cognitive decline in AD, which may be amenable to therapeutic intervention early in the disease process.
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Affiliation(s)
- Chelsea T Tiernan
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI, USA
| | - Stephen D Ginsberg
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY, USA; Department of Psychiatry, NYU Langone School of Medicine, New York, NY, USA; Department of Physiology & Neuroscience, NYU Langone School of Medicine, New York, NY, USA; NYU Neuroscience Institute, NYU Langone School of Medicine, New York, NY, USA
| | - Bin He
- Department of Neurobiology, Barrow Neurological Institute, Phoenix, AZ, USA
| | - Sarah M Ward
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI, USA
| | | | - Nicholas M Kanaan
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI, USA; Hauenstein Neurosciences Center, Mercy Health Saint Mary's Hospital, Grand Rapids, MI, USA
| | - Elliott J Mufson
- Department of Neurobiology, Barrow Neurological Institute, Phoenix, AZ, USA
| | - Scott E Counts
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI, USA; Hauenstein Neurosciences Center, Mercy Health Saint Mary's Hospital, Grand Rapids, MI, USA; Department of Family Medicine, Michigan State University, Grand Rapids, MI, USA; Michigan Alzheimer's Disease Core Center, Ann Arbor, MI, USA.
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15
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Jackson DP, Ting JH, Pozniak PD, Meurice C, Schleidt SS, Dao A, Lee AH, Klinman E, Jordan-Sciutto KL. Identification and characterization of two novel alternatively spliced E2F1 transcripts in the rat CNS. Mol Cell Neurosci 2018; 92:1-11. [PMID: 29936143 DOI: 10.1016/j.mcn.2018.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 06/05/2018] [Accepted: 06/19/2018] [Indexed: 10/28/2022] Open
Abstract
E2F1 is a transcription factor classically known to regulate G0/G1 to S phase progression in the cell cycle. In addition, E2F1 also regulates a wide range of apoptotic genes and thus has been well studied in the context of neuronal death and neurodegenerative diseases. However, its function and regulation in the mature central nervous system are not well understood. Alternative splicing is a well-conserved post-transcriptional mechanism common in cells of the CNS and is necessary to generate diverse functional modifications to RNA or protein products from genes. Heretofore, physiologically significant alternatively spliced E2F1 transcripts have not been reported. In the present study, we report the identification of two novel alternatively spliced E2F1 transcripts: E2F1b, an E2F1 transcript retaining intron 5, and E2F1c, an E2F1 transcript excluding exon 6. These alternatively spliced transcripts are observed in the brain and neural cell types including neurons, astrocytes, and undifferentiated oligodendrocytes. The expression of these E2F1 transcripts is distinct during maturation of primary hippocampal neuroglial cells. Pharmacologically-induced global translation inhibition with cycloheximide, anisomycin or thapsigargin lead to significantly reduced expression of E2F1a, E2F1b and E2F1c. Conversely, increasing neuronal activity by elevating the concentration of potassium chloride selectively increased the expression of E2F1b. Furthermore, experiments expressing these variants in vitro show the transcripts can be translated to generate a protein product. Taken together, our data suggest that the alternatively spliced E2F1 transcript behave differently than the E2F1a transcript, and our results provide a foundation for future investigation of the function of E2F1 splice variants in the CNS.
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Affiliation(s)
- Dan P Jackson
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St, Philadelphia, PA 19104, USA
| | - Jenhao H Ting
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St, Philadelphia, PA 19104, USA
| | - Paul D Pozniak
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St, Philadelphia, PA 19104, USA
| | - Claire Meurice
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St, Philadelphia, PA 19104, USA; Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Stephanie S Schleidt
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St, Philadelphia, PA 19104, USA
| | - Anh Dao
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St, Philadelphia, PA 19104, USA
| | - Amy H Lee
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St, Philadelphia, PA 19104, USA
| | - Eva Klinman
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kelly L Jordan-Sciutto
- Department of Pathology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St, Philadelphia, PA 19104, USA.
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16
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Kozlov S, Afonin A, Evsyukov I, Bondarenko A. Alzheimer's disease: as it was in the beginning. Rev Neurosci 2018; 28:825-843. [PMID: 28704198 DOI: 10.1515/revneuro-2017-0006] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 05/19/2017] [Indexed: 01/09/2023]
Abstract
Since Alzheimer's disease was first described in 1907, many attempts have been made to reveal its main cause. Nowadays, two forms of the disease are known, and while the hereditary form of the disease is clearly caused by mutations in one of several genes, the etiology of the sporadic form remains a mystery. Both forms share similar sets of neuropathological and molecular manifestations, including extracellular deposition of amyloid-beta, intracellular accumulation of hyperphosphorylated tau protein, disturbances in both the structure and functions of mitochondria, oxidative stress, metal ion metabolism disorders, impairment of N-methyl-D-aspartate receptor-related signaling pathways, abnormalities of lipid metabolism, and aberrant cell cycle reentry in some neurons. Such a diversity of symptoms led to proposition of various hypotheses for explaining the development of Alzheimer's disease, the amyloid hypothesis, which postulates the key role of amyloid-beta in Alzheimer's disease development, being the most prominent. However, this hypothesis does not fully explain all of the molecular abnormalities and is therefore heavily criticized. In this review, we propose a hypothetical model of Alzheimer's disease progression, assuming a key role of age-related mitochondrial dysfunction, as was postulated in the mitochondrial cascade hypothesis. Our model explains the connections between all the symptoms of Alzheimer's disease, with particular attention to autophagy, metal metabolism disorders, and aberrant cell cycle re-entry in neurons. Progression of the Alzheimer's disease appears to be a complex process involving aging and too many protective mechanisms affecting one another, thereby leading to even greater deleterious effects.
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17
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Manickam V, Dhakshinamoorthy V, Perumal E. Iron Oxide Nanoparticles Induces Cell Cycle-Dependent Neuronal Apoptosis in Mice. J Mol Neurosci 2018; 64:352-362. [PMID: 29368134 DOI: 10.1007/s12031-018-1030-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 01/11/2018] [Indexed: 01/09/2023]
Abstract
Iron oxide (Fe2O3) nanoparticles (NPs) with its unique magnetic and paramagnetic properties are popular in biomedical applications. Some of their neurotoxic mechanisms due to repeated administration are proven. However, we speculate that the neuronal damage might be due to apoptosis resulting from unusual cell cycle entry. Moreover, iron accumulation has been shown to be closely associated with most of the neurodegenerative disorders. Thus, in the current study, mice were orally (po) treated with the Fe2O3-NPs to investigate cell cycle-associated events/components and occurrence of apoptosis. A subsequent increase in oxidant levels was observed with the iron accumulation due to Fe2O3-NPs exposure. The accumulated β-amyloid and reduced level of cdk5 seem to aid in the cell cycle entry and forcing progression towards apoptosis. Expression of Cyclin D1 and pRb (Ser 795) indicate the cell cycle re-entry of neurons. Overexpression of RNA Pol II and PARP cleavage suggests DNA damage due to Fe2O3-NPs exposure. Further, hyperphosphorylation of p38 (Thr 180/Tyr 182) confirms the activation of DNA damage-dependent checkpoint. Expression patterns of pro- and anti-apoptotic markers, TUNEL and TEM indicate the occurrences of apoptosis.
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Affiliation(s)
- Vijayprakash Manickam
- Molecular Toxicology Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, Tamil Nadu, 641 046, India
| | - Vasanth Dhakshinamoorthy
- Molecular Toxicology Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, Tamil Nadu, 641 046, India
| | - Ekambaram Perumal
- Molecular Toxicology Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, Tamil Nadu, 641 046, India.
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18
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Huang P, Tong D, Sun J, Li Q, Zhang F. Generation and characterization of a human oral squamous carcinoma cell line SCC-9 with CRISPR/Cas9-mediated deletion of the p75 neurotrophin receptor. Arch Oral Biol 2017; 82:223-232. [PMID: 28654784 DOI: 10.1016/j.archoralbio.2017.06.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 06/03/2017] [Accepted: 06/05/2017] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To investigate the importance of the p75 neurotrophin receptor (p75NTR) in human tongue squamous carcinoma cells, we exploited the CRISPR/Cas9 technology to establish a p75NTR-knockout SCC-9 cell line and to explore the effect on biological functions. MATERIALS AND METHODS The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated endonuclease (Cas9) system was used to generate genomic deletion mutants of p75NTR in the tongue squamous carcinoma cell lines SCC-9. Single-guide RNA (sgRNA) sequences were designed to target the p75NTR genomic sequence and were cloned into plasmid pGK1.1. The linearized vector was electroporated into SCC-9 cells and p75NTR deletion was confirmed using Cruiser™ enzyme digestion and PCR amplification. SCC-9 clones with successful deletion of p75NTR were identified and verified by sequencing and selected for functional testing in cell proliferation, invasion, migration, and colony-forming assays. RESULTS Compared with control cells, p75NTR-knockout SCC-9 cells showed significantly diminished abilities to proliferate, invade, migrate, and form colonies, indicating a reduction in pro-tumorigenic behavior. CONCLUSION These data demonstrate, first, that the CRISPR/Cas9 system is a simplified method for generating p75NTR knockouts with relatively high efficiency, and second, that deletion of p75NTR suppresses several tumor-promoting properties of SCC-9 cells, suggesting that p75NTR is a potential target for the development of novel therapies for tongue cancer.
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Affiliation(s)
- Ping Huang
- Department of Gynecology, Qilu Hospital, Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, PR China
| | - Dongdong Tong
- Department of Oral and Maxillofacial Surgery, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, PR China
| | - Jing Sun
- Department of Bone Metabolism, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, PR China
| | - Qing Li
- Department of Oral and Maxillofacial Surgery, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, PR China
| | - Fenghe Zhang
- Department of Oral and Maxillofacial Surgery, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, PR China.
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19
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Tong D, Sun J, Huang P, Li M, Zhang F. p75 neurotrophin receptor: A potential surface marker of tongue squamous cell carcinoma stem cells. Mol Med Rep 2017; 15:2521-2529. [PMID: 28447720 PMCID: PMC5428397 DOI: 10.3892/mmr.2017.6291] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 11/03/2016] [Indexed: 11/27/2022] Open
Abstract
The present study detected p75 neurotrophin receptor (p75NTR) expression in tongue squamous cell carcinoma (TSCC) cell lines, in order to define the biological properties of p75NTR+ cells and to confirm the use of p75NTR+ as a surface marker for TSCC stem cells. p75NTR+ cells were separated from Tca-8113 and CAL-27 TSCC cells by fluorescence-activated cell sorting. Colony formation, MTT and scratch assays, and a tumorigenicity analysis were performed to measure self-renewal and proliferation, multidirectional differentiation, and tumorigenicity of p75NTR+ cells. p75NTR+ cells comprised 3.1 and 1.9% of Tca-8113 and CAL-27 cells (mean of three experiments), respectively, and were more able to form colonies compared with non-sorted cells (P<0.01). In addition, the proportion of p75NTR+ cells generated from monoclonal p75NTR+ cells decreased to 14.5 (Tca-8113) and 5.8% (CAL-27) of cells within 2 weeks, thus suggesting that p75NTR+ cells are able to generate p75NTR+ and p75NTR− cells. Furthermore, p75NTR+ cells exhibited increased proliferation, as evidenced by MTT assay (P<0.01) and had greater metastatic ability according to the scratch assay (P<0.01), compared with non-sorted cells. p75NTR+ cells also exhibited a greater tumorigenic capacity compared with non-sorted cells. In conclusion, p75NTR+ cells isolated from TSCC cell lines possess the characteristics of cancer stem cells; therefore, p75NTR may be considered a useful surface marker for the identification of TSCC stem cells.
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Affiliation(s)
- Dongdong Tong
- Department of Oral and Maxillofacial Surgery, School of Stomatology, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, P.R. China
| | - Jing Sun
- Department of Bone Metabolism, School of Stomatology, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, P.R. China
| | - Ping Huang
- Department of Gynecology, Qilu Hospital, Shandong University, Jinan, Shandong 250012, P.R. China
| | - Minqi Li
- Department of Bone Metabolism, School of Stomatology, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, P.R. China
| | - Fenghe Zhang
- Department of Oral and Maxillofacial Surgery, School of Stomatology, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Shandong University, Jinan, Shandong 250012, P.R. China
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20
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Abstract
Elucidating the mechanisms that regulate the life versus death of mammalian neurons is important not only for our understanding of the normal biology of the nervous system but also for our efforts to devise approaches to maintain neuronal survival in the face of traumatic injury or neurodegenerative disorders. Here, we review the emerging evidence that a key survival/death checkpoint in both peripheral and central neurons involves the p53 tumor suppressor and its newly discovered family members, p73 and p63. The full-length isoforms of these proteins function as proapoptotic proteins, whereas naturally occurring N-terminal truncated variants of p73 and p63 act as prosurvival proteins, at least partially by antagonizing the full-length family members. The authors propose that together, these isoforms comprise an upstream rheostat that sums different environmental cues to ultimately determine neuronal survival during development, during neuronal maintenance in adult animals, and even following traumatic injury.
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Affiliation(s)
- W Bradley Jacobs
- Developmental Biology and Cancer Research, Hospital for Sick Children, Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
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21
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Abstract
The local extension of cancer cells along nerves is a frequent clinical finding for various tumours. Traditionally, nerve invasion was assumed to occur via the path of least resistance; however, recent animal models and human studies have revealed that cancer cells have an innate ability to actively migrate along axons in a mechanism called neural tracking. The tendency of cancer cells to track along nerves is supported by various cell types in the perineural niche that secrete multiple growth factors and chemokines. We propose that the perineural niche should be considered part of the tumour microenvironment, describe the molecular cues that facilitate neural tracking and suggest methods for its inhibition.
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Affiliation(s)
- Moran Amit
- Laboratory for Applied Cancer Research, Department of Otolaryngology Head and Neck Surgery, Head and Neck Center, Rambam Healthcare Campus, Clinical Research Institute at Rambam, Rappaport Institute of Medicine and Research, The Technion-Israel Institute of Technology, Haalia Street No. 8, Haifa, Israel
| | - Shorook Na'ara
- Laboratory for Applied Cancer Research, Department of Otolaryngology Head and Neck Surgery, Head and Neck Center, Rambam Healthcare Campus, Clinical Research Institute at Rambam, Rappaport Institute of Medicine and Research, The Technion-Israel Institute of Technology, Haalia Street No. 8, Haifa, Israel
| | - Ziv Gil
- Laboratory for Applied Cancer Research, Department of Otolaryngology Head and Neck Surgery, Head and Neck Center, Rambam Healthcare Campus, Clinical Research Institute at Rambam, Rappaport Institute of Medicine and Research, The Technion-Israel Institute of Technology, Haalia Street No. 8, Haifa, Israel
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22
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Srikumar T, Padmanabhan J. Potential Use of Flavopiridol in Treatment of Chronic Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 929:209-228. [PMID: 27771926 DOI: 10.1007/978-3-319-41342-6_9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This chapter describes the potential use of flavopiridol, a CDK inhibitor with anti-inflammatory and anti-proliferative activities, in the treatment of various chronic diseases. Flavopiridol arrests cell cycle progression in the G1 or G2 phase by inhibiting the kinase activities of CDK1, CDK2, CDK4/6, and CDK7. Additionally, it binds tightly to CDK9, a component of the P-TEFb complex (CDK9/cyclin T), and interferes with RNA polymerase II activation and associated transcription. This in turn inhibits expression of several pro-survival and anti-apoptotic genes, and enhances cytotoxicity in transformed cells or differentiation in growth-arrested cells. Recent studies indicate that flavopiridol elicits anti-inflammatory activity via CDK9 and NFκB-dependent signaling. Overall, these effects of flavopiridol potentiate its ability to overcome aberrant cell cycle activation and/or inflammatory stimuli, which are mediators of various chronic diseases.
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Affiliation(s)
- Thejal Srikumar
- Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA
| | - Jaya Padmanabhan
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA. .,USF Health Byrd Alzheimer's Institute, University of South Florida, 4001 E. Fletcher Ave., Tampa, Florida, 33613, USA.
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23
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Abstract
Neurons are usually regarded as postmitotic cells that undergo apoptosis in response to cell cycle reactivation. Nevertheless, recent evidence indicates the existence of a defined developmental program that induces DNA replication in specific populations of neurons, which remain in a tetraploid state for the rest of their adult life. Similarly, de novo neuronal tetraploidization has also been described in the adult brain as an early hallmark of neurodegeneration. The aim of this review is to integrate these recent developments in the context of cell cycle regulation and apoptotic cell death in neurons. We conclude that a variety of mechanisms exists in neuronal cells for G1/S and G2/M checkpoint regulation. These mechanisms, which are connected with the apoptotic machinery, can be modulated by environmental signals and the neuronal phenotype itself, thus resulting in a variety of outcomes ranging from cell death at the G1/S checkpoint to full proliferation of differentiated neurons.
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Key Words
- AD, Alzheimer disease
- BDNF, brain-derived neurotrophic factor
- BrdU, 5-bromo-2′-deoxyuridine
- CKI, Cdk-inhibitor
- CNS, central nervous system
- Cdk, cyclin-dependent kinase
- Cip/Kip, cyclin inhibitor protein/kinase inhibitor protein
- G0, quiescent state
- G1, growth phase 1
- G2, growth phase 2
- Ink, inhibitor of kinase
- Mcm2, minichromosome maintenance 2
- PCNA, proliferating cell nuclear antigen
- PD, Parkinson disease
- RGCs, retinal ganglion cells
- Rb, Retinoblastoma
- S-phase
- S-phase, synthesis phase.
- apoptosis
- cell cycle re-entry
- mitosis
- neuron
- p38MAPK, p38 mitogen-activated protein kinase
- p75NTR, neurotrophin receptor p75
- tetraploid
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Affiliation(s)
- José M Frade
- a Department of Molecular, Cellular and Developmental Neurobiology; Instituto Cajal; Consejo Superior de Investigaciones Científicas (IC-CSIC) ; Madrid , Spain
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Silencing of Id2 attenuates hypoxia/ischemia-induced neuronal injury via inhibition of neuronal apoptosis. Behav Brain Res 2015; 292:528-36. [PMID: 26187693 DOI: 10.1016/j.bbr.2015.07.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 07/03/2015] [Accepted: 07/05/2015] [Indexed: 11/21/2022]
Abstract
Cerebral ischemic stroke has long been recognized as a prevalent and serious neurological disease that was associated with high mortality and morbidity. However, the current therapeutic protocols remain suboptimal with major mechanisms underlying stroke urgently warranted. Inhibitor of DNA binding/differentiation 2 (Id2) is found to be up-regulated in neuronal cells following hypoxia/ischemia (H/I). This study was aimed to investigate whether knockdown of Id2 in neuronal cells could protect them from hypoxic and ischemic injury both in vitro and in vivo. Flow cytometric analysis was employed to assess neuronal apoptosis in CoCl2-treated neuroblastoma B35 cells engineered to overexpress or knockdown Id2 expression. In vivo knockdown of Id2 was performed in Sprague-Dawley rats by a single intracerebroventricular injection of Cy3-labeled and cholesterol-modified Id2-siRNA. We found that knockdown of Id2 attenuated H/I-induced neuronal apoptosis in vitro while overexpression of Id2 produced an opposite effect. In a rat model of middle cerebral artery occlusion (MCAO), in vivo knockdown of Id2 significantly improved neurological deficits, reduced the volume of ischemic infarction and diminished the neuronal apoptosis in the penumbra area. Double immunofluorescence staining showed less co-localization of retinoblastoma tumor suppressor protein (Rb)-Id2 but greater co-localization of Rb-E2F1 in the penumbra area. Cell cycle assay further demonstrated that Id2 knockdown induced G0/G1 cell cycle arrest in CoCl2-treated B35 cells. The present data support the implication of Id2 in the modulation of H/I-induced neuronal apoptosis and may provide a potential therapeutic option to protect brain tissues from ischemic injury by inhibition of its expression.
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25
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Marathe S, Liu S, Brai E, Kaczarowski M, Alberi L. Notch signaling in response to excitotoxicity induces neurodegeneration via erroneous cell cycle reentry. Cell Death Differ 2015; 22:1775-84. [PMID: 25822340 DOI: 10.1038/cdd.2015.23] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Revised: 01/26/2015] [Accepted: 02/11/2015] [Indexed: 02/06/2023] Open
Abstract
Neurological disorders such as Alzheimer's disease, stroke and epilepsy are currently marred by the lack of effective treatments to prevent neuronal death. Erroneous cell cycle reentry (CCR) is hypothesized to have a causative role in neurodegeneration. We show that forcing S-phase reentry in cultured hippocampal neurons is sufficient to induce neurodegeneration. We found that kainic-acid treatment in vivo induces erroneous CCR and neuronal death through a Notch-dependent mechanism. Ablating Notch signaling in neurons provides neuroprotection against kainic acid-induced neuronal death. We further show that kainic-acid treatment activates Notch signaling, which increases the bioavailability of CyclinD1 through Akt/GSK3β pathway, leading to aberrant CCR via activation of CyclinD1-Rb-E2F1 axis. In addition, pharmacological blockade of this pathway at critical steps is sufficient to confer resistance to kainic acid-induced neurotoxicity in mice. Taken together, our results demonstrate that excitotoxicity leads to neuronal death in a Notch-dependent manner through erroneous CCR.
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Affiliation(s)
- S Marathe
- Department of Medicine, Institute of Anatomy, University of Fribourg, Fribourg, Switzerland
| | - S Liu
- Receptor Biology Section, NINDS/NIH, Bethesda, MD, USA
| | - E Brai
- Department of Medicine, Institute of Anatomy, University of Fribourg, Fribourg, Switzerland
| | - M Kaczarowski
- Department of Medicine, Institute of Anatomy, University of Fribourg, Fribourg, Switzerland
| | - L Alberi
- Department of Medicine, Institute of Anatomy, University of Fribourg, Fribourg, Switzerland
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26
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Padmanabhan J, Brown KR, Padilla A, Shelanski ML. Functional role of RNA polymerase II and P70 S6 kinase in KCl withdrawal-induced cerebellar granule neuron apoptosis. J Biol Chem 2015; 290:5267-79. [PMID: 25568312 DOI: 10.1074/jbc.m114.575225] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
KCl withdrawal-induced apoptosis in cerebellar granule neurons is associated with aberrant cell cycle activation, and treatment with cyclin-dependent kinase (Cdk) inhibitors protects cells from undergoing apoptosis. Because the Cdk inhibitor flavopiridol is known to inhibit RNA polymerase II (Pol II)-dependent transcription elongation by inhibiting the positive transcription elongation factor b (P-TEFb, a complex of CDK9 and cyclin T), we examined whether inhibition of RNA Pol II protects neurons from apoptosis. Treatment of neurons with 5, 6-dichloro-1-β-D-ribobenzimidazole (DRB), an RNA Pol II-dependent transcription elongation inhibitor, and flavopiridol inhibited phosphorylation and activation of Pol II and protected neurons from undergoing apoptosis. In addition to Pol II, neurons subjected to KCl withdrawal showed increased phosphorylation and activation of p70 S6 kinase, which was inhibited by both DRB and flavopiridol. Immunostaining analysis of the neurons deprived of KCl showed increased nuclear levels of phospho-p70 S6 kinase, and neurons protected with DRB and flavopiridol showed accumulation of the kinase into large spliceosome assembly factor-positive speckle domains within the nuclei. The formation of these foci corresponded with cell survival, and removal of the inhibitors resulted in dispersal of the speckles into smaller foci with subsequent apoptosis induction. Because p70 S6 kinase is known to induce translation of mRNAs containing a 5'-terminal oligopyrimidine tract, our data suggest that transcription and translation of this subset of mRNAs may contribute to KCl withdrawal-induced apoptosis in neurons.
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Affiliation(s)
- Jaya Padmanabhan
- From the Department of Molecular Medicine, University of South Florida Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613 and
| | - Kristy R Brown
- the Department of Pathology and Cell Biology, Taub Center for Alzheimer's Disease, College of Physicians and Surgeons, Columbia University, New York, New York 10032
| | - Amelia Padilla
- From the Department of Molecular Medicine, University of South Florida Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613 and
| | - Michael L Shelanski
- the Department of Pathology and Cell Biology, Taub Center for Alzheimer's Disease, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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27
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Wang TC, Luo SJ, Lin CL, Chang PJ, Chen MF. Modulation of p75 neurotrophin receptor under hypoxic conditions induces migration and invasion of C6 glioma cells. Clin Exp Metastasis 2014; 32:73-81. [PMID: 25527128 DOI: 10.1007/s10585-014-9692-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 12/08/2014] [Indexed: 01/07/2023]
Abstract
p75 neurotrophin receptor (p75NTR) has been reported to play important roles in various cancer types. However, the exact mechanism of tumorigenesis involving p75NTR is unknown. In this study, we investigated the relationship between the expression of p75NTR in malignant glioma and the impact on tumor cell migration and invasion. p75NTR and hypoxia-inducible factor-1α (HIF-1α) expression was down-regulated by short-hairpin RNA and up-regulated with expression vectors. By immunohistochemical staining and Western blot analysis, we found that p75NTR was expressed in both human and rat malignant gliomas. Knockdown of p75NTR increased the expression of vimentin, vascular endothelial growth factor, Matrix metalloproteinase 9, and TWIST, and enhanced the invasion and migration abilities assessed by transwell assay in the C6 tumor cells. Inverse expressions of p75NTR and HIF-1α were detected in glioma cell lines under hypoxic conditions, while increased HIF-1α significantly downregulated the expression of p75NTR, suggesting a HIF-1α-p75NTR-EMT pathway that may regulate glioma cells invasion and migration. Downregulation of p75NTR increased phosphorylation of Src, focal adhesion kinase (FAK) and paxillin. Knockdown of p75NTR also dysregulated β-catenin-mediated cell junctions, and up-regulated the expressions of fibronectin and L1CAM in the cell-cell junctions, thus suggesting that p75NTR knockdown contributed to a more aggressive migration phenotype via FAK signaling pathway. Our studies suggested that modulation of p75NTR under hypoxic condition could enhance C6 cells migration and invasion by induction of EMT, and activation of the FAK pathway. The HIF-1α-p75NTR-EMT axis may play a central role in glioma tumorigenesis.
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Affiliation(s)
- Ting-Chung Wang
- Division of Neurosurgery, Department of Surgery, Chang Gung Memorial Hospital, Chiayi, Taiwan
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28
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Repair of spinal cord injury by inhibition of astrocyte growth and inflammatory factor synthesis through local delivery of flavopiridol in PLGA nanoparticles. Biomaterials 2014; 35:6585-94. [DOI: 10.1016/j.biomaterials.2014.04.042] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 04/14/2014] [Indexed: 12/30/2022]
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29
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Galan A, Dergham P, Escoll P, de-la-Hera A, D'Onofrio PM, Magharious MM, Koeberle PD, Frade JM, Saragovi HU. Neuronal injury external to the retina rapidly activates retinal glia, followed by elevation of markers for cell cycle re-entry and death in retinal ganglion cells. PLoS One 2014; 9:e101349. [PMID: 24983470 PMCID: PMC4077807 DOI: 10.1371/journal.pone.0101349] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 06/05/2014] [Indexed: 11/22/2022] Open
Abstract
Retinal ganglion cells (RGCs) are neurons that relay visual signals from the retina to the brain. The RGC cell bodies reside in the retina and their fibers form the optic nerve. Full transection (axotomy) of the optic nerve is an extra-retinal injury model of RGC degeneration. Optic nerve transection permits time-kinetic studies of neurodegenerative mechanisms in neurons and resident glia of the retina, the early events of which are reported here. One day after injury, and before atrophy of RGC cell bodies was apparent, glia had increased levels of phospho-Akt, phospho-S6, and phospho-ERK1/2; however, these signals were not detected in injured RGCs. Three days after injury there were increased levels of phospho-Rb and cyclin A proteins detected in RGCs, whereas these signals were not detected in glia. DNA hyperploidy was also detected in RGCs, indicative of cell cycle re-entry by these post-mitotic neurons. These events culminated in RGC death, which is delayed by pharmacological inhibition of the MAPK/ERK pathway. Our data show that a remote injury to RGC axons rapidly conveys a signal that activates retinal glia, followed by RGC cell cycle re-entry, DNA hyperploidy, and neuronal death that is delayed by preventing glial MAPK/ERK activation. These results demonstrate that complex and variable neuro-glia interactions regulate healthy and injured states in the adult mammalian retina.
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Affiliation(s)
- Alba Galan
- Lady Davis Institute-Jewish General Hospital, Montreal, Quebec, Canada
| | - Pauline Dergham
- Lady Davis Institute-Jewish General Hospital, Montreal, Quebec, Canada
| | - Pedro Escoll
- Department of Medicine, Molecular Medicine Institute (IMMPA CSIC/UAH), School of Medicine, Alcalá University, Alcalá de Henares, Madrid, Spain
| | - Antonio de-la-Hera
- Department of Medicine, Molecular Medicine Institute (IMMPA CSIC/UAH), School of Medicine, Alcalá University, Alcalá de Henares, Madrid, Spain
| | - Philippe M. D'Onofrio
- Graduate Department of Rehabilitation Sciences, University of Toronto, Toronto, ON, Canada
| | - Mark M. Magharious
- Graduate Department of Rehabilitation Sciences, University of Toronto, Toronto, ON, Canada
| | | | - José María Frade
- Department of Molecular, Cellular and Developmental Neurobiology, Cajal Institute, CSIC, Madrid, Spain
| | - H. Uri Saragovi
- Lady Davis Institute-Jewish General Hospital, Montreal, Quebec, Canada
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
- Department of Oncology and the Cancer Center, McGill University, Montreal, Quebec, Canada
- * E-mail:
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30
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Wang H, Liao Z, Sun X, Shi Q, Huo G, Xie Y, Tang X, Zhi X, Tang Z. Intravenous administration of Honokiol provides neuroprotection and improves functional recovery after traumatic brain injury through cell cycle inhibition. Neuropharmacology 2014; 86:9-21. [PMID: 24973706 DOI: 10.1016/j.neuropharm.2014.06.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Revised: 06/14/2014] [Accepted: 06/16/2014] [Indexed: 01/30/2023]
Abstract
Recently, increasing evidence has shown that cell cycle activation is a key factor of neuronal death and neurological dysfunction after traumatic brain injury (TBI). This study aims to investigate the effects of Honokiol, a cell cycle inhibitor, on attenuating the neuronal damage and facilitating functional recovery after TBI in rats, in an attempt to unveil its underlying molecular mechanisms in TBI. This study suggested that delayed intravenous administration of Honokiol could effectively ameliorate TBI-induced sensorimotor and cognitive dysfunctions. Meanwhile, Honokiol treatment could also reduce the lesion volume and increase the neuronal survival in the cortex and hippocampus. The neuronal degeneration and apoptosis in the cortex and hippocampus were further significantly attenuated by Honokiol treatment. In addition, the expression of cell cycle-related proteins, including cyclin D1, CDK4, pRb and E2F1, was significantly increased and endogenous cell cycle inhibitor p27 was markedly decreased at different time points after TBI. And these changes were significantly reversed by post-injury Honokiol treatment. Furthermore, the expression of some of the key cell cycle proteins such as cyclin D1 and E2F1 and the associated apoptosis in neurons were both remarkably attenuated by Honokiol treatment. These results show that delayed intravenous administration of Honokiol could effectively improve the functional recovery and attenuate the neuronal cell death, which is probably, at least in part, attributed to its role as a cell cycle inhibitior. This might give clues to developing attractive therapies for future clinical trials.
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Affiliation(s)
- Haiquan Wang
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Chongqing 400016, China
| | - Zhengbu Liao
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Chongqing 400016, China
| | - Xiaochuan Sun
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Chongqing 400016, China
| | - Quanhong Shi
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Chongqing 400016, China
| | - Gang Huo
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Chongqing 400016, China
| | - Yanfeng Xie
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Chongqing 400016, China
| | - Xiaolan Tang
- Laboratory of Medical Molecular Biology, Medical College of Qinghai University, No.16 Kunlun Road, Xining 810000, Qinghai Province, China; Department of Cardiology, Medical College of Qinghai University, No.16 Kunlun Road, Xining 810000, Qinghai Province, China
| | - Xinggang Zhi
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Chongqing 400016, China
| | - Zhaohua Tang
- Department of Neurosurgery, The First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi Road, Chongqing 400016, China.
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31
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Jin G, Cao Z, Sun X, Wang K, Huang T, Shen B. Protein O-glucosyltransferase 1 overexpression downregulates p16 in BT474 human breast cancer cells. Oncol Lett 2014; 8:594-600. [PMID: 25009645 PMCID: PMC4081438 DOI: 10.3892/ol.2014.2197] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Accepted: 05/07/2014] [Indexed: 01/16/2023] Open
Abstract
Protein O-glucosyltransferase 1 (POGLUT1) is a novel gene that was initially isolated and identified from the bone marrow cells of patients with myelodysplastic syndrome/acute myeloid leukemia. Previous findings have suggested that POGLUT1 promotes the proliferation of U937 human tissue lymphoma cells. Furthermore, POGLUT1 has been identified in other tissues, including the mammary glands, lymph nodes, intestine, liver and spleen. In the present study, in order to investigate the function and target of POGLUT1 in BT474 breast cancer cells, the effect of POGLUT1 on cell proliferation, differentiation, apoptosis and key proteins in the transforming growth factor (TGF)-β1 signaling pathway was investigated in BT474 cells. The overexpression of POGLUT1 in the presence of TGF-β1 was found to significantly enhance cell viability. Flow cytometric and quantitative polymerase chain reaction analyses revealed that POGLUT1 had an effect on the cell cycle and inhibited the TGF-β1-induced transcriptional upregulation of p16, a major cyclin-dependent kinase inhibitor (CDKI). Furthermore, phosphorylated (p)-Smad3, which has a key role in mediating the TGF-β antiproliferative response, was greatly inhibited by exogenous POGLUT1, suggesting a role for POGLUT1 in the TGF-β1-mediated signaling pathway in the BT474 cell cycle. However, no significant changes were observed in the expression of other CDKIs or in cell apoptosis. The findings of the present study show that the increase in BT474 cell viabilty induced by POGLUT1 is associated with POGLUT1-induced inhibition of the transcriptional upregulation of p16 by TGF-β1, which may be a result of the inhibition of p-Smad3.
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Affiliation(s)
- Gang Jin
- Department of Medical Imaging, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China ; The No. 211 Hospital of the People's Liberation Army, Harbin, Heilongjiang 150086, P.R. China
| | - Zhigang Cao
- The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Xilin Sun
- Department of Medical Imaging, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Kai Wang
- Department of Medical Imaging, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Tao Huang
- Department of Medical Imaging, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Baozhong Shen
- Department of Medical Imaging, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
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32
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Iyirhiaro GO, Zhang Y, Estey C, O'Hare MJ, Safarpour F, Parsanejad M, Wang S, Abdel-Messih E, Callaghan SM, During MJ, Slack RS, Park DS. Regulation of ischemic neuronal death by E2F4-p130 protein complexes. J Biol Chem 2014; 289:18202-13. [PMID: 24828495 DOI: 10.1074/jbc.m114.574145] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inappropriate activation of cell cycle proteins, in particular cyclin D/Cdk4, is implicated in neuronal death induced by various pathologic stresses, including DNA damage and ischemia. Key targets of Cdk4 in proliferating cells include members of the E2F transcription factors, which mediate the expression of cell cycle proteins as well as death-inducing genes. However, the presence of multiple E2F family members complicates our understanding of their role in death. We focused on whether E2F4, an E2F member believed to exhibit crucial control over the maintenance of a differentiated state of neurons, may be critical in ischemic neuronal death. We observed that, in contrast to E2F1 and E2F3, which sensitize to death, E2F4 plays a crucial protective role in neuronal death evoked by DNA damage, hypoxia, and global ischemic insult both in vitro and in vivo. E2F4 occupies promoter regions of proapoptotic factors, such as B-Myb, under basal conditions. Following stress exposure, E2F4-p130 complexes are lost rapidly along with the presence of E2F4 at E2F-containing B-Myb promoter sites. In contrast, the presence of E2F1 at B-Myb sites increases with stress. Furthermore, B-Myb and C-Myb expression increases with ischemic insult. Taken together, we propose a model by which E2F4 plays a protective role in neurons from ischemic insult by forming repressive complexes that prevent prodeath factors such as Myb from being expressed.
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Affiliation(s)
- Grace O Iyirhiaro
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Yi Zhang
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Carmen Estey
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Michael J O'Hare
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Farzaneh Safarpour
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Mohammad Parsanejad
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Suzi Wang
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Elizabeth Abdel-Messih
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Steve M Callaghan
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Matthew J During
- the Department of Molecular Virology, Immunology, and Medical Genetics, Neurological Surgery, College of Medicine, The Ohio State University, Columbus, Ohio 43210
| | - Ruth S Slack
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - David S Park
- From the Department of Cellular and Molecular Medicine and Neuroscience, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
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33
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Ting JH, Marks DR, Schleidt SS, Wu JN, Zyskind JW, Lindl KA, Blendy JA, Pierce RC, Jordan-Sciutto KL. Targeted gene mutation of E2F1 evokes age-dependent synaptic disruption and behavioral deficits. J Neurochem 2014; 129:850-63. [PMID: 24460902 DOI: 10.1111/jnc.12655] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 11/21/2013] [Accepted: 01/10/2014] [Indexed: 02/05/2023]
Abstract
Aberrant expression and activation of the cell cycle protein E2F1 in neurons has been implicated in many neurodegenerative diseases. As a transcription factor regulating G1 to S phase progression in proliferative cells, E2F1 is often up-regulated and activated in models of neuronal death. However, despite its well-studied functions in neuronal death, little is known regarding the role of E2F1 in the mature brain. In this study, we used a combined approach to study the effect of E2F1 gene disruption on mouse behavior and brain biochemistry. We identified significant age-dependent olfactory and memory-related deficits in E2f1 mutant mice. In addition, we found that E2F1 exhibits punctated staining and localizes closely to the synapse. Furthermore, we found a mirroring age-dependent loss of post-synaptic protein-95 in the hippocampus and olfactory bulb as well as a global loss of several other synaptic proteins. Coincidently, E2F1 expression is significantly elevated at the ages, in which behavioral and synaptic perturbations were observed. Finally, we show that deficits in adult neurogenesis persist late in aged E2f1 mutant mice which may partially contribute to the behavior phenotypes. Taken together, our data suggest that the disruption of E2F1 function leads to specific age-dependent behavioral deficits and synaptic perturbations. E2F1 is a transcription factor regulating cell cycle progression and apoptosis. Although E2F1 dysregulation under toxic conditions can lead to neuronal death, little is known about its physiologic activity in the healthy brain. Here, we report significant age-dependent olfactory and memory deficits in mice with dysfunctional E2F1. Coincident with these behavioral changes, we also found age-matched synaptic disruption and persisting reduction in adult neurogenesis. Our study demonstrates that E2F1 contributes to physiologic brain structure and function.
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Affiliation(s)
- Jenhao H Ting
- Department of Pathology, University of Pennsylvania, School of Dental Medicine, Philadelphia, Pennsylvania, USA
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Wu J, Raver C, Piao C, Keller A, Faden AI. Cell cycle activation contributes to increased neuronal activity in the posterior thalamic nucleus and associated chronic hyperesthesia after rat spinal cord contusion. Neurotherapeutics 2013; 10:520-38. [PMID: 23775067 PMCID: PMC3701760 DOI: 10.1007/s13311-013-0198-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Spinal cord injury (SCI) causes not only sensorimotor and cognitive deficits, but frequently also severe chronic pain that is difficult to treat (SCI pain). We previously showed that hyperesthesia, as well as spontaneous pain induced by electrolytic lesions in the rat spinothalamic tract, is associated with increased spontaneous and sensory-evoked activity in the posterior thalamic nucleus (PO). We have also demonstrated that rodent impact SCI increases cell cycle activation (CCA) in the injury region and that post-traumatic treatment with cyclin dependent kinase inhibitors reduces lesion volume and motor dysfunction. Here we examined whether CCA contributes to neuronal hyperexcitability of PO and hyperpathia after rat contusion SCI, as well as to microglial and astroglial activation (gliopathy) that has been implicated in delayed SCI pain. Trauma caused enhanced pain sensitivity, which developed weeks after injury and was correlated with increased PO neuronal activity. Increased CCA was found at the thoracic spinal lesion site, the lumbar dorsal horn, and the PO. Increased microglial activation and cysteine-cysteine chemokine ligand 21 expression was also observed in the PO after SCI. In vitro, neurons co-cultured with activated microglia showed up-regulation of cyclin D1 and cysteine-cysteine chemokine ligand 21 expression. In vivo, post-injury treatment with a selective cyclin dependent kinase inhibitor (CR8) significantly reduced cell cycle protein induction, microglial activation, and neuronal activity in the PO nucleus, as well as limiting chronic SCI-induced hyperpathia. These results suggest a mechanistic role for CCA in the development of SCI pain, through effects mediated in part by the PO nucleus. Moreover, cell cycle modulation may provide an effective therapeutic strategy to improve reduce both hyperpathia and motor dysfunction after SCI.
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Affiliation(s)
- Junfang Wu
- Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, National Study Center for Trauma and EMS, University of Maryland, School of Medicine, Bressler Research Building, 655 W. Baltimore Street, Room #6-009, Baltimore, MD 21201, USA.
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35
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Andrusiak MG, Vandenbosch R, Dick FA, Park DS, Slack RS. LXCXE-independent chromatin remodeling by Rb/E2f mediates neuronal quiescence. Cell Cycle 2013; 12:1416-23. [PMID: 23574720 DOI: 10.4161/cc.24527] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Neuronal survival is dependent upon the retinoblastoma family members, Rb1 (Rb) and Rb2 (p130). Rb is thought to regulate gene repression, in part, through direct recruitment of chromatin modifying enzymes to its conserved LXCXE binding domain. We sought to examine the mechanisms that Rb employs to mediate cell cycle gene repression in terminally differentiated cortical neurons. Here, we report that Rb loss converts chromatin at the promoters of E2f-target genes to an activated state. We established a mouse model system in which Rb-LXCXE interactions could be induciblely disabled. Surprisingly, this had no effect on survival or gene silencing in neuronal quiescence. Absence of the Rb LXCXE-binding domain in neurons is compatible with gene repression and long-term survival, unlike Rb deficiency. Finally, we are able to show that chromatin activation following Rb deletion occurs at the level of E2fs. Blocking E2f-mediated transcription downstream of Rb loss is sufficient to maintain chromatin in an inactive state. Taken together our results suggest a model whereby Rb-E2f interactions are sufficient to maintain gene repression irrespective of LXCXE-dependent chromatin remodeling.
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Affiliation(s)
- Matthew G Andrusiak
- Department of Cellular & Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
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36
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Altered processing of amyloid precursor protein in cells undergoing apoptosis. PLoS One 2013; 8:e57979. [PMID: 23469123 PMCID: PMC3585261 DOI: 10.1371/journal.pone.0057979] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 01/30/2013] [Indexed: 01/25/2023] Open
Abstract
Altered proteolysis of amyloid precursor protein is an important determinant of pathology development in Alzheimer's disease. Here, we describe the detection of two novel fragments of amyloid precursor protein in H4 neuroglioma cells undergoing apoptosis. Immunoreactivity of these 25-35 kDa fragments to two different amyloid precursor protein antibodies suggests that they contain the amyloid-β region and an epitope near the C-terminus of amyloid precursor protein. Generation of these fragments is associated with cleavage of caspase-3 and caspase-7, suggesting activation of these caspases. Studies in neurons undergoing DNA damage-induced apoptosis also showed similar results. Inclusion of caspase inhibitors prevented the generation of these novel fragments, suggesting that they are generated by a caspase-dependent mechanism. Molecular weight prediction and immunoreactivity of the fragments generated suggested that such fragments could not be generated by cleavage at any previously identified caspase, secretase, or calpain site on amyloid precursor protein. Bioinformatic analysis of the amino acid sequence of amyloid precursor protein revealed that fragments fitting the observed size and immunoreactivity could be generated by either cleavage at a novel, hitherto unidentified, caspase site or at a previously identified matrix metalloproteinase site in the extracellular domain. Proteolytic cleavage at any of these sites leads to a decrease in the generation of α-secretase cleaved secreted APP, which has both anti-apoptotic and neuroprotective properties, and thus may contribute to neurodegeneration in Alzheimer's disease.
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37
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Retinal degeneration depends on Bmi1 function and reactivation of cell cycle proteins. Proc Natl Acad Sci U S A 2013; 110:E593-601. [PMID: 23359713 DOI: 10.1073/pnas.1108297110] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The epigenetic regulator Bmi1 controls proliferation in many organs. Reexpression of cell cycle proteins such as cyclin-dependent kinases (CDKs) is a hallmark of neuronal apoptosis in neurodegenerative diseases. Here we address the potential role of Bmi1 as a key regulator of cell cycle proteins during neuronal apoptosis. We show that several cell cycle proteins are expressed in different models of retinal degeneration and required in the Rd1 photoreceptor death process. Deleting E2f1, a downstream target of CDKs, provided temporary protection in Rd1 mice. Most importantly, genetic ablation of Bmi1 provided extensive photoreceptor survival and improvement of retinal function in Rd1 mice, mediated by a decrease in cell cycle markers and regulators independent of p16(Ink4a) and p19(Arf). These data reveal that Bmi1 controls the cell cycle-related death process, highlighting this pathway as a promising therapeutic target for neuroprotection in retinal dystrophies.
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Wu J, Kharebava G, Piao C, Stoica BA, Dinizo M, Sabirzhanov B, Hanscom M, Guanciale K, Faden AI. Inhibition of E2F1/CDK1 pathway attenuates neuronal apoptosis in vitro and confers neuroprotection after spinal cord injury in vivo. PLoS One 2012; 7:e42129. [PMID: 22848730 PMCID: PMC3405037 DOI: 10.1371/journal.pone.0042129] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 07/03/2012] [Indexed: 11/18/2022] Open
Abstract
Apoptosis of post-mitotic neurons plays a significant role in secondary tissue damage following traumatic spinal cord injury (SCI). Activation of E2F1-dependent transcription promotes expression of pro-apoptotic factors, including CDK1; this signal transduction pathway is believed to represent an important mechanism for the physiological or pathological neuronal cell death. However, a specific role for this pathway in neuronal apoptosis induced by SCI has not yet been reported. Here we demonstrate up-regulation of the E2F1/CDK1 pathway that is associated with neuronal apoptosis following impact SCI in rats. Expression of E2F1 and CDK1 were robustly up-regulated as early as 15 min after injury and sustained until 3 days post-injury. CDK1 activity and E2F1 downstream targets bim and c-Myb were significantly increased after SCI. Activation of E2F1/CDK1 signaling also was associated with death of neurons in vitro; this was attenuated by shRNA knockdown or pharmacological inhibition of the E2F1/CDK1 pathway. CR8, a novel and potent CDK1 inhibitor, blocked apoptosis of primary cortical neurons at low-micromolar concentrations. Moreover, SCI-induced up-regulation of E2F1/CDK1 and associated neuronal apoptosis was significantly attenuated by systemic injection of CR8 (1 mg/kg, i.p.) at 5 min after injury. CR8 significantly decreased posttraumatic elevation of biochemical markers of apoptosis, such as products of caspase-3 and α–fodrin cleavage, as well as neuronal cell death, as indicated by TUNEL staining. Importantly, CR8 treatment also increased the number of surviving neurons at 5 weeks after injury. Together, these findings indicate that activation of the E2F1/CDK1 pathway contributes to the pathophysiology of SCI and that selective inhibition of this signaling cascade may represent an attractive therapeutic strategy.
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Affiliation(s)
- Junfang Wu
- Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
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39
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Modi PK, Komaravelli N, Singh N, Sharma P. Interplay between MEK-ERK signaling, cyclin D1, and cyclin-dependent kinase 5 regulates cell cycle reentry and apoptosis of neurons. Mol Biol Cell 2012; 23:3722-30. [PMID: 22833568 PMCID: PMC3442418 DOI: 10.1091/mbc.e12-02-0125] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In response to neurotoxic signals, postmitotic neurons make attempts to reenter the cell cycle, which results in their death. Although several cell cycle proteins have been implicated in cell cycle-related neuronal apoptosis (CRNA), the molecular mechanisms that underlie this important event are poorly understood. Here, we demonstrate that neurotoxic agents such as β-amyloid peptide cause aberrant activation of mitogen-activated kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) signaling, which promotes the entry of neurons into the cell cycle, resulting in their apoptosis. The MEK-ERK pathway regulates CRNA by elevating the levels of cyclin D1. The increase in cyclin D1 attenuates the activation of cyclin-dependent kinase 5 (cdk5) by its neuronal activator p35. The inhibition of p35-cdk5 activity results in enhanced MEK-ERK signaling, leading to CRNA. These studies highlight how neurotoxic signals reprogram and alter the neuronal signaling machinery to promote their entry into the cell cycle, which eventually leads to neuronal cell death.
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Affiliation(s)
- Prashant Kumar Modi
- Eukaryotic Gene Expression Laboratory, National Institute of Immunology, New Delhi 110067, India
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40
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Wu J, Stoica BA, Dinizo M, Pajoohesh-Ganji A, Piao C, Faden AI. Delayed cell cycle pathway modulation facilitates recovery after spinal cord injury. Cell Cycle 2012; 11:1782-95. [PMID: 22510563 DOI: 10.4161/cc.20153] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Traumatic spinal cord injury (SCI) causes tissue loss and associated neurological dysfunction through mechanical damage and secondary biochemical and physiological responses. We have previously described the pathobiological role of cell cycle pathways following rat contusion SCI by examining the effects of early intrathecal cell cycle inhibitor treatment initiation or gene knockout on secondary injury. Here, we delineate changes in cell cycle pathway activation following SCI and examine the effects of delayed (24 h) systemic administration of flavopiridol, an inhibitor of major cyclin-dependent kinases (CDKs), on functional recovery and histopathology in a rat SCI contusion model. Immunoblot analysis demonstrated a marked upregulation of cell cycle-related proteins, including pRb, cyclin D1, CDK4, E2F1 and PCNA, at various time points following SCI, along with downregulation of the endogenous CDK inhibitor p27. Treatment with flavopiridol reduced induction of cell cycle proteins and increased p27 expression in the injured spinal cord. Functional recovery was significantly improved after SCI from day 7 through day 28. Treatment significantly reduced lesion volume and the number of Iba-1(+) microglia in the preserved tissue and increased the myelinated area of spared white matter as well as the number of CC1(+) oligodendrocytes. Furthermore, flavopiridol attenuated expression of Iba-1 and glactin-3, associated with microglial activation and astrocytic reactivity by reduction of GFAP, NG2, and CHL1 expression. Our current study supports the role of cell cycle activation in the pathophysiology of SCI and by using a clinically relevant treatment model, provides further support for the therapeutic potential of cell cycle inhibitors in the treatment of human SCI.
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Affiliation(s)
- Junfang Wu
- Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD, USA.
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41
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Lopes JP, Agostinho P. Cdk5: multitasking between physiological and pathological conditions. Prog Neurobiol 2011; 94:49-63. [PMID: 21473899 DOI: 10.1016/j.pneurobio.2011.03.006] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 03/28/2011] [Accepted: 03/28/2011] [Indexed: 01/11/2023]
Abstract
Cyclin-dependent kinase 5 (Cdk5) is a peculiar proline-directed serine/threonine kinase. Unlike the other members of the Cdk family, Cdk5 is not directly involved in cell cycle regulation, being normally associated with neuronal processes such as migration, cortical layering and synaptic plasticity. This kinase is present mainly in post-mitotic neurons and its activity is tightly regulated by the interaction with the specific activators, p35 and p39. Despite its pivotal role in CNS development, Cdk5 dysregulation has been implicated in different pathologies, such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and, most recently, prion-related encephalopathies (PRE). In these neurodegenerative conditions, Cdk5 overactivation and relocalization occurs upon association with p25, a truncated form of the normal activator p35. This activator switching will cause a shift in the phosphorylative pattern of Cdk5, with an alteration both in targets and activity, ultimately leading to neuronal demise. In AD and PRE, two disorders that share clinical and neuropathological features, Cdk5 dysregulation is a linking event between the major neuropathological markers: amyloid plaques, tau hyperphosphorylation and synaptic and neuronal loss. Moreover, this kinase was shown to be involved in abortive cell cycle re-entry, a feature recently proposed as a possible step in the neuronal apoptosis mechanism of several neurological diseases. This review focuses on the role of Cdk5 in neurons, namely in the regulation of cytoskeletal dynamics, synaptic function and cell survival, both in physiological and in pathological conditions, highlighting the relevance of Cdk5 in the main mechanisms of neurodegeneration in Alzheimer's disease and other brain pathologies.
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Affiliation(s)
- Joao P Lopes
- Center for Neuroscience and Cell Biology, Faculty of Medicine, Biochemistry Institute, University of Coimbra, 3004 Coimbra, Portugal.
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42
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Abstract
Traumatic spinal cord injury (SCI) evokes a complex cascade of events with initial mechanical damage leading to secondary injury processes that contribute to further tissue loss and functional impairment. Growing evidence suggests that the cell cycle is activated following SCI. Up-regulation of cell cycle proteins after injury appears to contribute not only to apoptotic cell death of postmitotic cells, including neurons and oligodendrocytes, but also to post-traumatic gliosis and microglial activation. Inhibition of key cell cycle regulatory pathways reduces injury-induced cell death, as well as microglial and astroglial proliferation both in vitro and in vivo. Treatment with cell cycle inhibitors in rodent SCI models prevents neuronal cell death and reduces inflammation, as well as the surrounding glial scar, resulting in markedly reduced lesion volumes and improved motor recovery. Here we review the effects of SCI on cell cycle pathways, as well as the therapeutic potential and mechanism of action of cell cycle inhibitors for this disorder.
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Affiliation(s)
- Junfang Wu
- Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
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43
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Delston RB, Matatall KA, Sun Y, Onken MD, Harbour JW. p38 phosphorylates Rb on Ser567 by a novel, cell cycle-independent mechanism that triggers Rb-Hdm2 interaction and apoptosis. Oncogene 2010; 30:588-99. [PMID: 20871633 PMCID: PMC3012146 DOI: 10.1038/onc.2010.442] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The retinoblastoma protein (Rb) inhibits both cell division and apoptosis, but the mechanism by which Rb alternatively regulates these divergent outcomes remains poorly understood. Cyclin dependent kinases (Cdks) promote cell division by phosphorylating and reversibly inactivating Rb by a hierarchical series of phosphorylation events and sequential conformational changes. The stress-regulated mitogen activated protein kinase (MAPK) p38 also phosphorylates Rb, but it does so in a cell cycle-independent manner that is associated with apoptosis rather than with cell division. Here, we show that p38 phosphorylates Rb by a novel mechanism that is distinct from that of Cdks. p38 bypasses the cell cycle-associated hierarchical phosphorylation and directly phosphorylates Rb on Ser567, which is not phosphorylated during the normal cell cycle. Phosphorylation by p38, but not Cdks, triggers an interaction between Rb and the human homologue of murine double minute 2 (Hdm2), leading to degradation of Rb, release of E2F1 and cell death. These findings provide a mechanistic explanation for how Rb regulates cell division and apoptosis through different kinases, and reveal how Hdm2 may functionally link the tumor suppressors Rb and p53.
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Affiliation(s)
- R B Delston
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, MO, USA
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44
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Lopes JP, Oliveira CR, Agostinho P. Neurodegeneration in an Abeta-induced model of Alzheimer's disease: the role of Cdk5. Aging Cell 2010; 9:64-77. [PMID: 19895631 DOI: 10.1111/j.1474-9726.2009.00536.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Cdk5 dysregulation is a major event in the neurodegenerative process of Alzheimer's disease (AD). In vitro studies using differentiated neurons exposed to Abeta exhibit Cdk5-mediated tau hyperphosphorylation, cell cycle re-entry and neuronal loss. In this study we aimed to determine the role of Cdk5 in neuronal injury occurring in an AD mouse model obtained through the intracerebroventricular (icv) injection of the Abeta(1-40) synthetic peptide. In mice icv-injected with Abeta, Cdk5 activator p35 is cleaved by calpains, leading to p25 formation and Cdk5 overactivation. Subsequently, there was an increase in tau hyperphosphorylation, as well as decreased levels of synaptic markers. Cell cycle reactivation and a significant neuronal loss were also observed. These neurotoxic events in Abeta-injected mice were prevented by blocking calpain activation with MDL28170, which was administered intraperitoneally (ip). As MDL prevents p35 cleavage and subsequent Cdk5 overactivation, it is likely that this kinase is involved in tau hyperphosphorylation, cell cycle re-entry, synaptic loss and neuronal death triggered by Abeta. Altogether, these data demonstrate that Cdk5 plays a pivotal role in tau phosphorylation, cell cycle induction, synaptotoxicity, and apoptotic death in postmitotic neurons exposed to Abeta peptides in vivo, acting as a link between diverse neurotoxic pathways of AD.
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Affiliation(s)
- Joao P Lopes
- Center for Neuroscience and Cell Biology, Faculty of Medicine, Biochemistry Institute, University of Coimbra, 3004 Coimbra, Portugal
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45
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Zhang Y, Parsanejad M, Huang E, Qu D, Aleyasin H, Rousseaux MWC, Gonzalez YR, Cregan SP, Slack RS, Park DS. Pim-1 kinase as activator of the cell cycle pathway in neuronal death induced by DNA damage. J Neurochem 2009; 112:497-510. [PMID: 19895669 DOI: 10.1111/j.1471-4159.2009.06476.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
DNA damage is a critical component of neuronal death underlying neurodegenerative diseases and injury. Neuronal death evoked by DNA damage is characterized by inappropriate activation of multiple cell cycle components. However, the mechanism regulating this activation is not fully understood. We demonstrated previously that the cell division cycle (Cdc) 25A phosphatase mediates the activation of cyclin-dependent kinases and neuronal death evoked by the DNA damaging agent camptothecin. We also showed that Cdc25A activation is blocked by constitutive checkpoint kinase 1 activity under basal conditions in neurons. Presently, we report that an additional factor is central to regulation of Cdc25A phosphatase in neuronal death. In a gene array screen, we first identified Pim-1 as a potential factor up-regulated following DNA damage. We confirmed the up-regulation of Pim-1 transcript, protein and kinase activity following DNA damage. This induction of Pim-1 is regulated by the nuclear factor kappa beta (NF-kappaB) pathway as Pim-1 expression and activity are significantly blocked by siRNA-mediated knockdown of NF-kappaB or NF-kappaB pharmacological inhibitors. Importantly, Pim-1 activity is critical for neuronal death in this paradigm and its deficiency blocks camptothecin-mediated neuronal death. It does so by activating Cdc25A with consequent activation of cyclin D1-associated kinases. Taken together, our results demonstrate that Pim-1 kinase plays a central role in DNA damage-evoked neuronal death by regulating aberrant neuronal cell cycle activation.
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Affiliation(s)
- Yi Zhang
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
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46
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Cell Cycle Activation and CNS Injury. Neurotox Res 2009; 16:221-37. [PMID: 19526282 DOI: 10.1007/s12640-009-9050-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 03/26/2009] [Accepted: 03/26/2009] [Indexed: 12/28/2022]
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47
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The involvement of upregulation and translocation of phospho-Rb in early neuronal apoptosis following focal cerebral ischemia in rats. Neurochem Res 2009; 34:1113-9. [PMID: 19123049 DOI: 10.1007/s11064-008-9887-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2008] [Indexed: 10/21/2022]
Abstract
The aim of this study was to investigate the temporal and spatial relationship between phospho-Rb (ser 795) and neuronal apoptotic death in rats subjected to transient focal cerebral ischemia. We found increased phosphorylation of Rb and translocation from neuronal nucleus to cytoplasm in the penumbra zone at 12 h, 1 day, 3 days and 7 days after middle cerebral artery occlusion (MCAO)/reperfusion, compared with sham-operated controls. At 12 h and 1 day, phospho-Rb appeared to be colocalizated with TUNEL staining in neurons, but staining was not colocalizated at 3 days and 7 days. These results demonstrated that cytoplasmic translocation of phospho-Rb from nucleus of neurons occurs in potential apoptotic neurons in the early stages of ischemia/reperfusion, suggesting that the Rb pathway may only be involved in early neuronal apoptosis and may be not an apoptotic signal in the late stages of transient cerebral ischemia.
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48
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Abstract
Although the concepts of secondary injury and neuroprotection after neurotrauma are experimentally well supported, clinical trials of neuroprotective agents in traumatic brain injury or spinal cord injury have been disappointing. Most strategies to date have used drugs directed toward a single pathophysiological mechanism that contributes to early necrotic cell death. Given these failures, recent research has increasingly focused on multifunctional (i.e., multipotential, pluripotential) agents that target multiple injury mechanisms, particularly those that occur later after the insult. Here we review two such approaches that show particular promise in experimental neurotrauma: cell cycle inhibitors and small cyclized peptides. Both show extended therapeutic windows for treatment and appear to share at least one important target.
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Affiliation(s)
- Bogdan Stoica
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA.
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49
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Cell cycle activation in striatal neurons from Huntington's disease patients and rats treated with 3-nitropropionic acid. Int J Dev Neurosci 2008; 26:665-71. [PMID: 18768156 DOI: 10.1016/j.ijdevneu.2008.07.016] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 07/28/2008] [Accepted: 07/28/2008] [Indexed: 01/10/2023] Open
Abstract
This study was undertaken to investigate the potential role of cell cycle re-entry in an experimental model of Huntington's disease and in human brain samples. We found that after treatment of rats with the mitochondrial neurotoxin 3-nitropropionic acid, the expression of cell cycle markers of G1 phase measured by immunohistochemistry was induced in the striatal brain region. Furthermore, we detected an increase in the nuclear and also cytoplasmatic E2F-1 expression, suggesting that this protein could activate the apoptotic cascade in rat brain. Western blot analysis of post-mortem brain samples from patients also showed an increase in the expression of E2F-1 and cyclin D1 in comparison with control samples. These results indicate that cell cycle re-entry is activated in Huntington's disease and may contribute to the neurodegenerative process.
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50
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Abstract
Mitochondria undergo continuous fission and fusion events in physiological situations. Fragmentation of mitochondria during cell death has been shown to play a key role in cell death progression, including release of the mitochondrial apoptotic proteins. Ultrastructural changes in mitochondria, such as cristae remodeling, is also involved in cell death initiation. Here, we emphasize the important role of mitochondrial fission/fusion machinery in neuronal cell death. Unlike many other cell types such as immortalized cell lines, neurons are distinct morphologically and functionally. We will discuss how this uniqueness presents special challenges in the cellular response to neurotoxic stresses, and how this affects the mitochondrial dynamics in the regulation of cell death in neurons.
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Affiliation(s)
- Eric C C Cheung
- University of Ottawa, Department of Cellular Molecular Medicine, Ottawa Health Research Institute, 451 Smyth Road, Ottawa, Ontario, Canada
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