1
|
Shishioh N, Kiryu-Seo S, Abe-Dohmae S, Yokoyama S, Kiyama H. Expression of ATP-binding cassette transporter A1 is induced by nerve injury and its deficiency affects neurite tip morphology and elongation in cultured neurons. J Chem Neuroanat 2022; 125:102164. [PMID: 36122678 DOI: 10.1016/j.jchemneu.2022.102164] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/12/2022] [Accepted: 09/15/2022] [Indexed: 11/28/2022]
Abstract
Axonal regeneration requires changes in the lipid dynamics of the axon membrane for growth and extension. Here, we examined the expression of genes associated with lipid transport after nerve injury. The expression of ATP-binding cassette transporter-A1 (ABCA1), which participates in the transport of cholesterol from the plasma membrane, was markedly upregulated in motor and sensory neurons after nerve injury. Stimulation of PC12 cells with the nerve growth factor induced neurite extension and ABCA1 expression predominantly in regions proximal to the neurite tip. To clarify the functional role of ABCA1 in neurite elongation, we examined the morphology of neurons cultured from conditionally-injured dorsal root ganglia from ABCA1-deficient mice. We found a significant increase in neurite branch formation in these neurons. In addition, the neurite tips of ABCA1-deficient neurons appeared excessively ruffled, and the direction of neurite elongation was unsteady. In contrast, the neurite tips of wild-type neurons were not excessively ruffled, and the neurites elongated rapidly in a stable directionally-oriented manner. Together, these findings suggest that ABCA1 plays an important role in regulating the membrane lipid composition of injured neurons and in axonal regeneration following nerve injury.
Collapse
Affiliation(s)
- Nobue Shishioh
- Department of Functional Anatomy & Neuroscience, Nagoya University, Graduate School of Medicine, Nagoya 466-8550, Japan; Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga 526-0829, Japan
| | - Sumiko Kiryu-Seo
- Department of Functional Anatomy & Neuroscience, Nagoya University, Graduate School of Medicine, Nagoya 466-8550, Japan.
| | - Sumiko Abe-Dohmae
- Food and Nutritional Sciences, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501, Japan
| | - Shinji Yokoyama
- Food and Nutritional Sciences, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501, Japan
| | - Hiroshi Kiyama
- Department of Functional Anatomy & Neuroscience, Nagoya University, Graduate School of Medicine, Nagoya 466-8550, Japan.
| |
Collapse
|
2
|
Cheng H, Huang Y, Qian J, Meng F, Fan Y. Organic photovoltaic device enhances the neural differentiation of rat bone marrow-derived mesenchymal stem cells. MEDICINE IN NOVEL TECHNOLOGY AND DEVICES 2022. [DOI: 10.1016/j.medntd.2022.100176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
3
|
Marosi M, Nenov MN, Di Re J, Dvorak NM, Alshammari M, Laezza F. Inhibition of the Akt/PKB Kinase Increases Na v1.6-Mediated Currents and Neuronal Excitability in CA1 Hippocampal Pyramidal Neurons. Int J Mol Sci 2022; 23:ijms23031700. [PMID: 35163623 PMCID: PMC8836202 DOI: 10.3390/ijms23031700] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 01/21/2022] [Accepted: 01/28/2022] [Indexed: 02/07/2023] Open
Abstract
In neurons, changes in Akt activity have been detected in response to the stimulation of transmembrane receptors. However, the mechanisms that lead to changes in neuronal function upon Akt inhibition are still poorly understood. In the present study, we interrogate how Akt inhibition could affect the activity of the neuronal Nav channels with while impacting intrinsic excitability. To that end, we employed voltage-clamp electrophysiological recordings in heterologous cells expressing the Nav1.6 channel isoform and in hippocampal CA1 pyramidal neurons in the presence of triciribine, an inhibitor of Akt. We showed that in both systems, Akt inhibition resulted in a potentiation of peak transient Na+ current (INa) density. Akt inhibition correspondingly led to an increase in the action potential firing of the CA1 pyramidal neurons that was accompanied by a decrease in the action potential current threshold. Complementary confocal analysis in the CA1 pyramidal neurons showed that the inhibition of Akt is associated with the lengthening of Nav1.6 fluorescent intensity along the axonal initial segment (AIS), providing a mechanism for augmented neuronal excitability. Taken together, these findings provide evidence that Akt-mediated signal transduction might affect neuronal excitability in a Nav1.6-dependent manner.
Collapse
Affiliation(s)
- Mate Marosi
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX 77555, USA; (M.M.); (M.N.N.); (J.D.R.); (N.M.D.); (M.A.)
| | - Miroslav N. Nenov
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX 77555, USA; (M.M.); (M.N.N.); (J.D.R.); (N.M.D.); (M.A.)
| | - Jessica Di Re
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX 77555, USA; (M.M.); (M.N.N.); (J.D.R.); (N.M.D.); (M.A.)
| | - Nolan M. Dvorak
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX 77555, USA; (M.M.); (M.N.N.); (J.D.R.); (N.M.D.); (M.A.)
| | - Musaad Alshammari
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX 77555, USA; (M.M.); (M.N.N.); (J.D.R.); (N.M.D.); (M.A.)
- Department of Pharmacology, College of Pharmacy, King Saud University, Riyadh P.O. Box 145111, Saudi Arabia
| | - Fernanda Laezza
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX 77555, USA; (M.M.); (M.N.N.); (J.D.R.); (N.M.D.); (M.A.)
- Center for Addiction Research, Center for Biomedical Engineering and Mitchell, Center for Neurodegenerative Diseases, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
- Correspondence: ; Tel.: +1-(409)-772-9672; Fax: +1-(409)-772-9642
| |
Collapse
|
4
|
Bhowmick S, Abdul-Muneer PM. PTEN Blocking Stimulates Corticospinal and Raphespinal Axonal Regeneration and Promotes Functional Recovery After Spinal Cord Injury. J Neuropathol Exp Neurol 2021; 80:169-181. [PMID: 33367790 DOI: 10.1093/jnen/nlaa147] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The long-term disabilities associated with spinal cord injury (SCI) are primarily due to the absence of robust neuronal regeneration and functional plasticity. The inability of the axon to regenerate after SCI is contributed by several intrinsic factors that trigger a cascade of molecular growth program and modulates axonal sprouting. Phosphatase and tensin homolog (PTEN) is one of the intrinsic factors contributing to growth failure after SCI, however, the underlying mechanism is not well known. Here, we developed a novel therapeutic approach for treating SCI by suppressing the action of PTEN in a mouse model of hemisection SCI. We have used a novel peptide, PTEN antagonistic peptide (PAP) to block the critical domains of PTEN to demonstrate its ability to potentially promote axon growth. PAP treatment not only enhanced regeneration of corticospinal axons into the caudal spinal cord but also promoted the regrowth of descending serotonergic axons in SCI mice. Furthermore, expression levels of p-mTOR, p-S6, p-Akt, p-Erk, p-GSK, p-PI3K downstream of PTEN signaling pathway were increased significantly in the spinal cord of SCI mice systemically treated with PAP than control TAT peptide-treated mice. Our novel strategy of administering deliverable compounds postinjury may facilitate translational feasibility for central nervous system injury.
Collapse
Affiliation(s)
- Saurav Bhowmick
- From the Laboratory of CNS Injury and Molecular Therapy, JFK Neuroscience Institute, Hackensack Meridian Health JFK University Medical Center, Edison, New Jersey
| | - P M Abdul-Muneer
- Department of Neurology, Hackensack Meridian School of Medicine, Nutley, New Jersey
| |
Collapse
|
5
|
Cheng H, Huang Y, Chen W, Che J, Liu T, Na J, Wang R, Fan Y. Cyclic Strain and Electrical Co-stimulation Improve Neural Differentiation of Marrow-Derived Mesenchymal Stem Cells. Front Cell Dev Biol 2021; 9:624755. [PMID: 34055769 PMCID: PMC8150581 DOI: 10.3389/fcell.2021.624755] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 03/23/2021] [Indexed: 12/26/2022] Open
Abstract
The current study investigated the combinatorial effect of cyclic strain and electrical stimulation on neural differentiation potential of rat bone marrow-derived mesenchymal stem cells (BMSCs) under epidermal growth factor (EGF) and fibroblast growth factor 2 (FGF2) inductions in vitro. We developed a prototype device which can provide cyclic strain and electrical signal synchronously. Using this system, we demonstrated that cyclic strain and electrical co-stimulation promote the differentiation of BMCSs into neural cells with more branches and longer neurites than strain or electrical stimulation alone. Strain and electrical co-stimulation can also induce a higher expression of neural markers in terms of transcription and protein level. Neurotrophic factors and the intracellular cyclic AMP (cAMP) are also upregulated with co-stimulation. Importantly, the co-stimulation further enhances the calcium influx of neural differentiated BMSCs when responding to acetylcholine and potassium chloride (KCl). Finally, the phosphorylation of extracellular-signal-regulated kinase (ERK) 1 and 2 and protein kinase B (AKT) was elevated under co-stimulation treatment. The present work suggests a synergistic effect of the combination of cyclic strain and electrical stimulation on BMSC neuronal differentiation and provides an alternative approach to physically manipulate stem cell differentiation into mature and functional neural cells in vitro.
Collapse
Affiliation(s)
- Hong Cheng
- Beijing Advanced Innovation Center for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Yan Huang
- Beijing Advanced Innovation Center for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Wei Chen
- Beijing Advanced Innovation Center for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Jifei Che
- Beijing Advanced Innovation Center for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Taidong Liu
- Beijing Advanced Innovation Center for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Jing Na
- Beijing Advanced Innovation Center for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Ruojin Wang
- Beijing Advanced Innovation Center for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Yubo Fan
- Beijing Advanced Innovation Center for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, School of Biological Science and Medical Engineering, Beihang University, Beijing, China.,School of Engineering Medicine, Beihang University, Beijing, China
| |
Collapse
|
6
|
Guo Y, Chen H, Wang QJ, Qi X, Li Q, Fu W, Huang J, Yao CY, Liu ZY, Wang MZ, An L, Tian JH, Wu ZH. Prolonged melatonin treatment promote testicular recovery by enhancing RAC1-mediated apoptotic cell clearance and cell junction-dependent spermatogensis after heat stress. Theriogenology 2020; 162:22-31. [PMID: 33418161 DOI: 10.1016/j.theriogenology.2020.12.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 12/08/2020] [Accepted: 12/12/2020] [Indexed: 12/13/2022]
Abstract
INTRODUCTION A decline in semen quality caused by global warming and torrid working conditions is a major cause of human male infertility, and heat stress-induced decreases in male reproductive ability results in economic losses in livestock husbandry. Increasing evidence suggests that melatonin exerts protective effects on stress-induced DNA damage and apoptosis in germ cells. However, few studies have assessed the effects of melatonin on testicular recovery during post-heat stress and the underlying mechanisms. METHODS AND RESULTS In vivo studies using 8-week-old male CD-1 mice revealed that melatonin pretreatment (50 mg/kg for 5 days) did not alleviate heat stress-induced germ cell loss and disrupted testicular histomorphology, however, long-term melatonin administration after heat stress accelerated germ cell apoptosis, spermatogenic cell regeneration, and testicular weight recovery. In vitro studies demonstrated that melatonin enhanced RAC1 activity, resulting in increased phagocytosis of apoptotic germ cells by Sertoli cells. In addition, melatonin restored gap junctions and tight junctions after heat stress, thereby promoting hollow seminiferous tubule filling. DISCUSSION Long-term melatonin administration accelerated testicular recovery after heat stress by enhancing the phagocytotic activity of Sertoli cells and the regeneration of spermatogenic cells. This finding suggests that melatonin is a potential therapeutic for heat stress-induced male infertility.
Collapse
Affiliation(s)
- Yao Guo
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Hui Chen
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, 071000, China
| | - Qiang-Jun Wang
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Xin Qi
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Qin Li
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Wei Fu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Jie Huang
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Chun-Yan Yao
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Zhong-Ying Liu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Mei-Zhi Wang
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Lei An
- National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Jian-Hui Tian
- National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Zhong-Hong Wu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China.
| |
Collapse
|
7
|
Igarashi M, Honda A, Kawasaki A, Nozumi M. Neuronal Signaling Involved in Neuronal Polarization and Growth: Lipid Rafts and Phosphorylation. Front Mol Neurosci 2020; 13:150. [PMID: 32922262 PMCID: PMC7456915 DOI: 10.3389/fnmol.2020.00150] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 07/16/2020] [Indexed: 12/17/2022] Open
Abstract
Neuronal polarization and growth are developmental processes that occur during neuronal cell differentiation. The molecular signaling mechanisms involved in these events in in vivo mammalian brain remain unclear. Also, cellular events of the neuronal polarization process within a given neuron are thought to be constituted of many independent intracellular signal transduction pathways (the "tug-of-war" model). However, in vivo results suggest that such pathways should be cooperative with one another among a given group of neurons in a region of the brain. Lipid rafts, specific membrane domains with low fluidity, are candidates for the hotspots of such intracellular signaling. Among the signals reported to be involved in polarization, a number are thought to be present or translocated to the lipid rafts in response to extracellular signals. As part of our analysis, we discuss how such novel molecular mechanisms are combined for effective regulation of neuronal polarization and growth, focusing on the significance of the lipid rafts, including results based on recently introduced methods.
Collapse
Affiliation(s)
- Michihiro Igarashi
- Department of Neurochemistry and Molecular Cell Biology, Niigata University School of Medicine and Graduate School of Medical/Dental Sciences, Niigata, Japan
| | - Atsuko Honda
- Department of Neurochemistry and Molecular Cell Biology, Niigata University School of Medicine and Graduate School of Medical/Dental Sciences, Niigata, Japan
| | - Asami Kawasaki
- Department of Neurochemistry and Molecular Cell Biology, Niigata University School of Medicine and Graduate School of Medical/Dental Sciences, Niigata, Japan
| | - Motohiro Nozumi
- Department of Neurochemistry and Molecular Cell Biology, Niigata University School of Medicine and Graduate School of Medical/Dental Sciences, Niigata, Japan
| |
Collapse
|
8
|
Nathan FM, Ohtake Y, Wang S, Jiang X, Sami A, Guo H, Zhou FQ, Li S. Upregulating Lin28a Promotes Axon Regeneration in Adult Mice with Optic Nerve and Spinal Cord Injury. Mol Ther 2020; 28:1902-1917. [PMID: 32353321 DOI: 10.1016/j.ymthe.2020.04.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 03/16/2020] [Accepted: 04/09/2020] [Indexed: 12/22/2022] Open
Abstract
Severed CNS axons fail to regenerate in adult mammals and there are no effective regenerative strategies to treat patients with CNS injuries. Several genes, including phosphatase and tensin homolog (PTEN) and Krüppel-like factors, regulate intrinsic growth capacity of mature neurons. The Lin28 gene is essential for cell development and pluripotency in worms and mammals. In this study, we evaluated the role of Lin28a in regulating regenerative capacity of diverse populations of CNS neurons in adult mammals. Using a neuron-specific Thy1 promoter, we generated transgenic mice that overexpress Lin28a protein in multiple populations of projection neurons, including corticospinal tracts and retinal ganglion cells. We demonstrate that upregulation of Lin28a in transgenic mice induces significant long distance regeneration of both corticospinal axons and the optic nerve in adult mice. Importantly, overexpression of Lin28a by post-injury treatment with adeno-associated virus type 2 (AAV2) vector stimulates dramatic regeneration of descending spinal tracts and optic nerve axons after lesions. Upregulation of Lin28a also enhances activity of the Akt signaling pathway in mature CNS neurons. Therefore, Lin28a is critical for regulating growth capacity of multiple CNS neurons and may become an important molecular target for treating CNS injuries.
Collapse
Affiliation(s)
- Fatima M Nathan
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA; Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Yosuke Ohtake
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA; Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Shuo Wang
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA; Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Xinpei Jiang
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA; Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Armin Sami
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA; Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Hua Guo
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA; Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Feng-Quan Zhou
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Shuxin Li
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA; Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA.
| |
Collapse
|
9
|
Hunter GL, Giniger E. Phosphorylation and Proteolytic Cleavage of Notch in Canonical and Noncanonical Notch Signaling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1227:51-68. [DOI: 10.1007/978-3-030-36422-9_4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
|
10
|
Wang S, Zhang Z, Almenar-Queralt A, Leem J, DerMardirossian C, Roth DM, Patel PM, Patel HH, Head BP. Caveolin-1 Phosphorylation Is Essential for Axonal Growth of Human Neurons Derived From iPSCs. Front Cell Neurosci 2019; 13:324. [PMID: 31379509 PMCID: PMC6650578 DOI: 10.3389/fncel.2019.00324] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 07/01/2019] [Indexed: 01/02/2023] Open
Abstract
Proper axonal growth and guidance is essential for neuron differentiation and development. Abnormal neuronal development due to genetic or epigenetic influences can contribute to neurological and mental disorders such as Down syndrome, Rett syndrome, and autism. Identification of the molecular targets that promote proper neuronal growth and differentiation may restore structural and functional neuroplasticity, thus improving functional performance in neurodevelopmental disorders. Using differentiated human neuronal progenitor cells (NPCs) derived from induced pluripotent stem cells (iPSCs), the present study demonstrates that during early stage differentiation of human NPCs, neuron-targeted overexpression constitutively active Rac1 (Rac1CA) and constitutively active Cdc42 (Cdc42CA) enhance expression of P-Cav-1, T-Cav-1, and P-cofilin and increases axonal growth. Similarly, neuron-targeted over-expression of Cav-1 (termed SynCav1) increases axonal development by increasing both axon length and volume. Moreover, inhibition of Cav-1(Y14A) phosphorylation blunts Rac1/Cdc42-mediated both axonal growth and differentiation of human NPCs and SynCav1(Y14A)-treated NPCs exhibited blunted axonal growth. These results suggest that: (1) SynCav1-mediated dendritic and axonal growth in human NPCs is dependent upon P-Cav-1, (2) P-Cav-1 is necessary for proper axonal growth during early stages of neuronal differentiation, and (3) Rac1/Cdc42CA-mediated neuronal growth is in part dependent upon P-Cav-1. In conclusion, Cav-1 phosphorylation is essential for human neuronal axonal growth during early stages of neuronal differentiation.
Collapse
Affiliation(s)
- Shanshan Wang
- Veterans Affairs San Diego Healthcare System, San Diego, CA, United States.,Department of Anesthesiology, UC San Diego, La Jolla, CA, United States
| | - Zheng Zhang
- Veterans Affairs San Diego Healthcare System, San Diego, CA, United States.,Department of Anesthesiology, UC San Diego, La Jolla, CA, United States
| | - Angels Almenar-Queralt
- Department of Cellular and Molecular Medicine, Sanford Consortium for Regenerative Medicine, La Jolla, CA, United States
| | - Joseph Leem
- Veterans Affairs San Diego Healthcare System, San Diego, CA, United States.,Department of Anesthesiology, UC San Diego, La Jolla, CA, United States
| | - Celine DerMardirossian
- Department of Immunology and Microbial Sciences, The Scripps Research Institute, La Jolla, CA, United States.,Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA, United States
| | - David M Roth
- Veterans Affairs San Diego Healthcare System, San Diego, CA, United States.,Department of Anesthesiology, UC San Diego, La Jolla, CA, United States
| | - Piyush M Patel
- Veterans Affairs San Diego Healthcare System, San Diego, CA, United States.,Department of Anesthesiology, UC San Diego, La Jolla, CA, United States
| | - Hemal H Patel
- Veterans Affairs San Diego Healthcare System, San Diego, CA, United States.,Department of Anesthesiology, UC San Diego, La Jolla, CA, United States
| | - Brian P Head
- Veterans Affairs San Diego Healthcare System, San Diego, CA, United States.,Department of Anesthesiology, UC San Diego, La Jolla, CA, United States
| |
Collapse
|
11
|
Abstract
Polyphosphoinositides (PPIn) are essential signaling phospholipids that make remarkable contributions to the identity of all cellular membranes and signaling cascades in mammalian cells. They exert regulatory control over membrane homeostasis via selective interactions with cellular proteins at the membrane–cytoplasm interface. This review article briefly summarizes our current understanding of the key roles that PPIn play in orchestrating and regulating crucial electrical and chemical signaling events in mammalian neurons and the significant neuro-pathophysiological conditions that arise following alterations in their metabolism.
Collapse
Affiliation(s)
- Eamonn James Dickson
- Department Physiology and Membrane Biology, University of California, Davis, CA, 95616, USA
| |
Collapse
|
12
|
Ibarra-Lecue I, Mollinedo-Gajate I, Meana JJ, Callado LF, Diez-Alarcia R, Urigüen L. Chronic cannabis promotes pro-hallucinogenic signaling of 5-HT2A receptors through Akt/mTOR pathway. Neuropsychopharmacology 2018; 43:2028-2035. [PMID: 29748632 PMCID: PMC6098160 DOI: 10.1038/s41386-018-0076-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 04/13/2018] [Accepted: 04/15/2018] [Indexed: 01/28/2023]
Abstract
Long-term use of potent cannabis during adolescence increases the risk of developing schizophrenia later in life, but to date, the mechanisms involved remain unknown. Several findings suggest that the functional selectivity of serotonin 2A receptor (5-HT2AR) through inhibitory G-proteins is involved in the molecular mechanisms responsible for psychotic symptoms. Moreover, this receptor is dysregulated in the frontal cortex of schizophrenia patients. In this context, studies involving cannabis exposure and 5-HT2AR are scarce. Here, we tested in mice the effect of an early chronic Δ9-tetrahydrocannabinol (THC) exposure on cortical 5-HT2AR expression, as well as on its in vivo and in vitro functionality. Long-term exposure to THC induced a pro-hallucinogenic molecular conformation of the 5-HT2AR and exacerbated schizophrenia-like responses, such as prepulse inhibition disruption. Supersensitive coupling of 5-HT2AR toward inhibitory Gαi1-, Gαi3-, Gαo-, and Gαz-proteins after chronic THC exposure was observed, without changes in the canonical Gαq/11-protein pathway. In addition, we found that inhibition of Akt/mTOR pathway by rapamycin blocks the changes in 5-HT2AR signaling pattern and the supersensitivity to schizophrenia-like effects induced by chronic THC. The present study provides the first evidence of a mechanistic explanation for the relationship between chronic cannabis exposure in early life and increased risk of developing psychosis-like behaviors in adulthood.
Collapse
Affiliation(s)
- Inés Ibarra-Lecue
- Department of Pharmacology, University of the Basque Country UPV/EHU and Centro de Investigación Biomédica en Red de Salud Mental CIBERSAM, Leioa, Spain
| | - Irene Mollinedo-Gajate
- Department of Pharmacology, University of the Basque Country UPV/EHU and Centro de Investigación Biomédica en Red de Salud Mental CIBERSAM, Leioa, Spain
| | - J Javier Meana
- Department of Pharmacology, University of the Basque Country UPV/EHU and Centro de Investigación Biomédica en Red de Salud Mental CIBERSAM, Leioa, Spain
- Biocruces Health Research Institute, Bizkaia, Spain
| | - Luis F Callado
- Department of Pharmacology, University of the Basque Country UPV/EHU and Centro de Investigación Biomédica en Red de Salud Mental CIBERSAM, Leioa, Spain
- Biocruces Health Research Institute, Bizkaia, Spain
| | - Rebeca Diez-Alarcia
- Department of Pharmacology, University of the Basque Country UPV/EHU and Centro de Investigación Biomédica en Red de Salud Mental CIBERSAM, Leioa, Spain
- Biocruces Health Research Institute, Bizkaia, Spain
| | - Leyre Urigüen
- Department of Pharmacology, University of the Basque Country UPV/EHU and Centro de Investigación Biomédica en Red de Salud Mental CIBERSAM, Leioa, Spain.
- Biocruces Health Research Institute, Bizkaia, Spain.
| |
Collapse
|
13
|
mTOR-Dependent Cell Proliferation in the Brain. BIOMED RESEARCH INTERNATIONAL 2017; 2017:7082696. [PMID: 29259984 PMCID: PMC5702949 DOI: 10.1155/2017/7082696] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 10/22/2017] [Indexed: 02/08/2023]
Abstract
The mammalian Target of Rapamycin (mTOR) is a molecular complex equipped with kinase activity which controls cell viability being key in the PI3K/PTEN/Akt pathway. mTOR acts by integrating a number of environmental stimuli to regulate cell growth, proliferation, autophagy, and protein synthesis. These effects are based on the modulation of different metabolic pathways. Upregulation of mTOR associates with various pathological conditions, such as obesity, neurodegeneration, and brain tumors. This is the case of high-grade gliomas with a high propensity to proliferation and tissue invasion. Glioblastoma Multiforme (GBM) is a WHO grade IV malignant, aggressive, and lethal glioma. To date, a few treatments are available although the outcome of GBM patients remains poor. Experimental and pathological findings suggest that mTOR upregulation plays a major role in determining an aggressive phenotype, thus determining relapse and chemoresistance. Among several activities, mTOR-induced autophagy suppression is key in GBM malignancy. In this article, we discuss recent evidence about mTOR signaling and its role in normal brain development and pathological conditions, with a special emphasis on its role in GBM.
Collapse
|
14
|
Love JM, Bober BG, Orozco E, White AT, Bremner SN, Lovering RM, Schenk S, Shah SB. mTOR regulates peripheral nerve response to tensile strain. J Neurophysiol 2017; 117:2075-2084. [PMID: 28250148 PMCID: PMC5434482 DOI: 10.1152/jn.00257.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 02/09/2017] [Accepted: 02/25/2017] [Indexed: 01/26/2023] Open
Abstract
While excessive tensile strain can be detrimental to nerve function, strain can be a positive regulator of neuronal outgrowth. We used an in vivo rat model of sciatic nerve strain to investigate signaling mechanisms underlying peripheral nerve response to deformation. Nerves were deformed by 11% and did not demonstrate deficits in compound action potential latency or amplitude during or after 6 h of strain. As revealed by Western blotting, application of strain resulted in significant upregulation of mammalian target of rapamycin (mTOR) and S6 signaling in nerves, increased myelin basic protein (MBP) and β-actin levels, and increased phosphorylation of neurofilament subunit H (NF-H) compared with unstrained (sham) contralateral nerves (P < 0.05 for all comparisons, paired two-tailed t-test). Strain did not alter neuron-specific β3-tubulin or overall nerve tubulin levels compared with unstrained controls. Systemic rapamycin treatment, thought to selectively target mTOR complex 1 (mTORC1), suppressed mTOR/S6 signaling, reduced levels of MBP and overall tubulin, and decreased NF-H phosphorylation in nerves strained for 6 h, revealing a role for mTOR in increasing MBP expression and NF-H phosphorylation, and maintaining tubulin levels. Consistent with stretch-induced increases in MBP, immunolabeling revealed increased S6 signaling in Schwann cells of stretched nerves compared with unstretched nerves. In addition, application of strain to cultured adult dorsal root ganglion neurons showed an increase in axonal protein synthesis based on a puromycin incorporation assay, suggesting that neuronal translational pathways also respond to strain. This work has important implications for understanding mechanisms underlying nerve response to strain during development and regeneration.NEW & NOTEWORTHY Peripheral nerves experience tensile strain (stretch) during development and movement. Excessive strain impairs neuronal function, but moderate strains are accommodated by nerves and can promote neuronal growth; mechanisms underlying these phenomena are not well understood. We demonstrated that levels of several structural proteins increase following physiological levels of nerve strain and that expression of a subset of these proteins is regulated by mTOR. Our work has important implications for understanding nerve development and strain-based regenerative strategies.
Collapse
Affiliation(s)
- James M Love
- Fischell Department of Bioengineering, University of Maryland, College Park, Maryland
| | - Brian G Bober
- Department of Bioengineering, University of California-San Diego, La Jolla, California
| | - Elisabeth Orozco
- Department of Orthopaedic Surgery, University of California-San Diego, La Jolla, California.,Veterans Affairs San Diego Healthcare System, San Diego, California; and
| | - Amanda T White
- Department of Orthopaedic Surgery, University of California-San Diego, La Jolla, California
| | - Shannon N Bremner
- Department of Orthopaedic Surgery, University of California-San Diego, La Jolla, California.,Veterans Affairs San Diego Healthcare System, San Diego, California; and
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland
| | - Simon Schenk
- Department of Orthopaedic Surgery, University of California-San Diego, La Jolla, California
| | - Sameer B Shah
- Department of Bioengineering, University of California-San Diego, La Jolla, California; .,Department of Orthopaedic Surgery, University of California-San Diego, La Jolla, California.,Veterans Affairs San Diego Healthcare System, San Diego, California; and
| |
Collapse
|
15
|
Neuritin Mediates Activity-Dependent Axonal Branch Formation in Part via FGF Signaling. J Neurosci 2016; 36:4534-48. [PMID: 27098696 DOI: 10.1523/jneurosci.1715-15.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Accepted: 03/09/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Aberrant branch formation of granule cell axons (mossy fiber sprouting) is observed in the dentate gyrus of many patients with temporal lobe epilepsy and in animal models of epilepsy. However, the mechanisms underlying mossy fiber sprouting remain elusive. Based on the hypothesis that seizure-mediated gene expression induces abnormal mossy fiber growth, we screened activity-regulated genes in the hippocampus and found that neuritin, an extracellular protein anchored to the cell surface, was rapidly upregulated after electroconvulsive seizures. Overexpression of neuritin in the cultured rat granule cells promoted their axonal branching. Also, kainic acid-dependent axonal branching was abolished in the cultured granule cells fromneuritinknock-out mice, suggesting that neuritin may be involved in activity-dependent axonal branching. Moreover,neuritinknock-out mice showed less-severe seizures in chemical kindling probably by reduced mossy fiber sprouting and/or increased seizure resistance. We found that inhibition of the fibroblast growth factor (FGF) receptor attenuated the neuritin-dependent axonal branching. FGF administration also increased branching in granule neurons, whereasneuritinknock-out mice did not show FGF-dependent axonal branching. In addition, FGF and neuritin treatment enhanced the recruitment of FGF receptors to the cell surface. These findings suggest that neuritin and FGF cooperate in inducing mossy fiber sprouting through FGF signaling. Together, these results suggest that FGF and neuritin-mediated axonal branch induction are involved in the aggravation of epilepsy. SIGNIFICANCE STATEMENT This study reveals the molecular mechanism underlying mossy fiber sprouting. Mossy fiber sprouting is the aberrant axonal branching of granule neurons in the hippocampus, which is observed in patients with epilepsy. Excess amounts of neuritin, a protein upregulated by neural activity, promoted axonal branching in granule neurons. A deficiency of neuritin suppressed mossy fiber sprouting and resulted in mitigation of seizure severity. Neuritin and fibroblast growth factor (FGF) cooperated in stimulating FGF signaling and enhancing axonal branching. Neuritin is necessary for FGF-mediated recruitment of FGF receptors to the cell surface. The recruitment of FGF receptors would promote axonal branching. The discovery of this new mechanism should contribute to the development of novel antiepileptic drugs to inhibit axonal branching via neuritin-FGF signaling.
Collapse
|
16
|
Calabrese F, Riva MA, Molteni R. Synaptic alterations associated with depression and schizophrenia: potential as a therapeutic target. Expert Opin Ther Targets 2016; 20:1195-207. [PMID: 27167520 DOI: 10.1080/14728222.2016.1188080] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
INTRODUCTION In recent years, the concept of 'synaptopathy' has been extended from neurodegenerative and neurological disorders to psychiatric diseases. According to this nascent line of research, disruption in synaptic structure and function acts as the main determinant of mental illness. Therefore, molecular systems and processes crucial for synaptic activity may represent promising therapeutic targets. AREAS COVERED We review data on synaptic structural alterations in depression and schizophrenia and on specific molecular systems and/or mechanisms important for the maintenance of proper synaptic function. Specifically, we examine the involvement of the neuroligin system, the local protein translation, and the neurotrophin BDNF by reviewing clinical and preclinical studies, with particular attention to results provided by using animal models based on the role of stress in psychiatric diseases. Finally, we also discuss the impact of pharmacological treatment on these molecular systems/mechanisms. EXPERT OPINION The relevance of synaptic dysfunctions in psychiatric diseases is undoubted and the potential to normalize, ameliorate, and shape such alterations by acting on molecular systems crucial to ensure synaptic function property is fascinating. However, future studies are required to elucidate several open issues.
Collapse
Affiliation(s)
- Francesca Calabrese
- a Dipartimento di Scienze Farmacologiche e Biomolecolari , Università degli Studi di Milano , Milan , Italy
| | - Marco A Riva
- a Dipartimento di Scienze Farmacologiche e Biomolecolari , Università degli Studi di Milano , Milan , Italy
| | - Raffaella Molteni
- a Dipartimento di Scienze Farmacologiche e Biomolecolari , Università degli Studi di Milano , Milan , Italy
| |
Collapse
|
17
|
The glucagon-like peptide 1 (GLP) receptor as a therapeutic target in Parkinson's disease: mechanisms of action. Drug Discov Today 2016; 21:802-18. [DOI: 10.1016/j.drudis.2016.01.013] [Citation(s) in RCA: 188] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/03/2015] [Accepted: 01/25/2016] [Indexed: 02/06/2023]
|
18
|
Shi Y, Tan SH, Ng S, Zhou J, Yang ND, Koo GB, McMahon KA, Parton RG, Hill MM, Del Pozo MA, Kim YS, Shen HM. Critical role of CAV1/caveolin-1 in cell stress responses in human breast cancer cells via modulation of lysosomal function and autophagy. Autophagy 2016; 11:769-84. [PMID: 25945613 DOI: 10.1080/15548627.2015.1034411] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
CAV1 (caveolin 1, caveolae protein, 22kDa) is well known as a principal scaffolding protein of caveolae, a specialized plasma membrane structure. Relatively, the caveolae-independent function of CAV1 is less studied. Autophagy is a process known to involve various membrane structures, including autophagosomes, lysosomes, and autolysosomes for degradation of intracellular proteins and organelles. Currently, the function of CAV1 in autophagy remains largely elusive. In this study, we demonstrate for the first time that CAV1 deficiency promotes both basal and inducible autophagy. Interestingly, the promoting effect was found mainly in the late stage of autophagy via enhancing lysosomal function and autophagosome-lysosome fusion. Notably, the regulatory function of CAV1 in lysosome and autophagy was found to be caveolae-independent, and acts through lipid rafts. Furthermore, the elevated autophagy level induced by CAV1 deficiency serves as a cell survival mechanism under starvation. Importantly, downregulation of CAV1 and enhanced autophagy level were observed in human breast cancer cells and tissues. Taken together, our data reveal a novel function of CAV1 and lipid rafts in breast cancer development via modulation of lysosomal function and autophagy.
Collapse
Key Words
- ATP6V0D1, ATPase H+ transporting lysosomal 38kDa, V0 subunit d1
- Baf, bafilomycin A1
- CAV1, caveolin 1
- CHO, water-soluble cholesterol
- CQ, choloroquine
- CTSL, cathepsin L
- CTxB, cholera toxin subunit B
- DRF, detergent-resistant fraction
- DSF, detergent-soluble fraction
- EGF, epidermal growth factor
- KO, knockout
- LAMP1, lysosomal-associated membrane protein 1
- MAP1LC3/LC3, microtubule-associated protein 1 light chain 3
- MBCD, methyl-β-cyclodextrin
- MEF, mouse embryonic fibroblasts
- MTOR, mechanistic target of rapamycin
- PBS, phosphate-buffered saline
- PI, propidium iodide
- PLA, proximity ligation assay
- PTRF, polymerase I and transcript release factor
- TFRC, transferrin receptor
- TSC, tuberous sclerosis complex
- WT, wild type.
- autophagy
- breast cancer
- caveolin 1
- lipid rafts
- lysosome
- tfLC3B, mRFP-GFP tandem fluorescent-tagged LC3B
Collapse
Affiliation(s)
- Yin Shi
- a Department of Physiology; Yong Loo Lin School of Medicine; National University of Singapore ; Singapore
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
The intrinsic growth ability of all the neurons declines during development although some may grow better than others. Numerous intracellular signaling proteins and transcription factors have been shown to regulate the intrinsic growth capacity in mature neurons. Among them, PI3 kinase/Akt pathway is important for controlling axon elongation. As a negative regulator of this pathway, the tumor suppressor phosphatase and tensin homolog (PTEN) appears critical to control the regenerative ability of young and adult neurons. This review will focus on recent research progress in axon regeneration and neural repair by PTEN inhibition and therapeutic potential of blocking this phosphatase for neurological disorders. Inhibition of PTEN by deletion in conditional knockout mice, knockdown by short-hairpin RNA, or blockade by pharmacological approaches, including administration of selective PTEN antagonist peptides, stimulates various degrees of axon regrowth in juvenile or adult rodents with central nervous system injuries. Importantly, post-injury PTEN suppression could enhance axonal growth and functional recovery in adult central nervous system after injury.
Collapse
Affiliation(s)
- Yosuke Ohtake
- Shriners Hospitals Pediatric Research Center, Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, USA
| | - Umar Hayat
- Shriners Hospitals Pediatric Research Center, Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, USA
| | - Shuxin Li
- Shriners Hospitals Pediatric Research Center, Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, USA
| |
Collapse
|
20
|
Expressing Constitutively Active Rheb in Adult Neurons after a Complete Spinal Cord Injury Enhances Axonal Regeneration beyond a Chondroitinase-Treated Glial Scar. J Neurosci 2015; 35:11068-80. [PMID: 26245968 DOI: 10.1523/jneurosci.0719-15.2015] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
UNLABELLED After a spinal cord injury (SCI), CNS axons fail to regenerate, resulting in permanent deficits. This is due to: (1) the presence of inhibitory molecules, e.g., chondroitin sulfate proteoglycans (CSPG), in the glial scar at the lesion; and (2) the diminished growth capacity of adult neurons. We sought to determine whether expressing a constitutively active form of the GTPase Rheb (caRheb) in adult neurons after a complete SCI in rats improves intrinsic growth potential to result in axon regeneration out of a growth-supportive peripheral nerve grafted (PNG) into the SCI cavity. We also hypothesized that treating the glial scar with chondroitinase ABC (ChABC), which digests CSPG, would further allow caRheb-transduced neurons to extend axons across the distal graft interface. We found that targeting this pathway at a clinically relevant post-SCI time point improves both sprouting and regeneration of axons. CaRheb increased the number of axons, but not the number of neurons, that projected into the PNG, indicative of augmented sprouting. We also saw that caRheb enhanced sprouting far rostral to the injury. CaRheb not only increased growth rostral and into the graft, it also resulted in significantly more regrowth of axons across a ChABC-treated scar into caudal spinal cord. CaRheb(+) neurons had higher levels of growth-associated-43, suggestive of a newly identified mechanism for mTOR-mediated enhancement of regeneration. Thus, we demonstrate for the first time that simultaneously addressing intrinsic and scar-associated, extrinsic impediments to regeneration results in significant regrowth beyond an extremely challenging, complete SCI site. SIGNIFICANCE STATEMENT After spinal cord injury (SCI), CNS axons fail to regenerate, resulting in permanent deficits. This is due to the diminished growth capacity of adult neurons and the presence of inhibitory molecules in the scar at the lesion. We sought to simultaneously counter both of these obstacles to achieve more robust regeneration after complete SCI. We transduced neurons postinjury to express a constitutively active Rheb to enhance their intrinsic growth potential, transplanted a growth supporting peripheral nerve graft into the lesion cavity, and enzymatically modulated the inhibitory glial scar distal to the graft. We demonstrate, for the first time, that simultaneously addressing neuron-related, intrinsic deficits in axon regrowth and extrinsic, scar-associated impediments to regeneration results in significant regeneration after SCI.
Collapse
|
21
|
Stamatakou E, Hoyos-Flight M, Salinas PC. Wnt Signalling Promotes Actin Dynamics during Axon Remodelling through the Actin-Binding Protein Eps8. PLoS One 2015; 10:e0134976. [PMID: 26252776 PMCID: PMC4529215 DOI: 10.1371/journal.pone.0134976] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 07/07/2015] [Indexed: 11/26/2022] Open
Abstract
Upon arrival at their synaptic targets, axons slow down their growth and extensively remodel before the assembly of presynaptic boutons. Wnt proteins are target-derived secreted factors that promote axonal remodelling and synaptic assembly. In the developing spinal cord, Wnts secreted by motor neurons promote axonal remodelling of NT-3 responsive dorsal root ganglia neurons. Axon remodelling induced by Wnts is characterised by growth cone pausing and enlargement, processes that depend on the re-organisation of microtubules. However, the contribution of the actin cytoskeleton has remained unexplored. Here, we demonstrate that Wnt3a regulates the actin cytoskeleton by rapidly inducing F-actin accumulation in growth cones from rodent DRG neurons through the scaffold protein Dishevelled-1 (Dvl1) and the serine-threonine kinase Gsk3β. Importantly, these changes in actin cytoskeleton occurs before enlargement of the growth cones is evident. Time-lapse imaging shows that Wnt3a increases lamellar protrusion and filopodia velocity. In addition, pharmacological inhibition of actin assembly demonstrates that Wnt3a increases actin dynamics. Through a yeast-two hybrid screen, we identified the actin-binding protein Eps8 as a direct interactor of Dvl1, a scaffold protein crucial for the Wnt signalling pathway. Gain of function of Eps8 mimics Wnt-mediated axon remodelling, whereas Eps8 silencing blocks the axon remodelling activity of Wnt3a. Importantly, blockade of the Dvl1-Eps8 interaction completely abolishes Wnt3a-mediated axonal remodelling. These findings demonstrate a novel role for Wnt-Dvl1 signalling through Eps8 in the regulation of axonal remodeling.
Collapse
Affiliation(s)
- Eleanna Stamatakou
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, United Kingdom
| | - Monica Hoyos-Flight
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, United Kingdom
| | - Patricia C. Salinas
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, United Kingdom
- * E-mail:
| |
Collapse
|
22
|
Increase in Neuropilin-1 on the Surface of Growth Cones and Putative Raft Domains in Neuronal NG108-15 Cells Co-Cultured with Vascular Smooth Muscle SM-3 Cells. J Membr Biol 2014; 248:171-8. [DOI: 10.1007/s00232-014-9754-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 11/11/2014] [Indexed: 12/18/2022]
|
23
|
McMahon JJ, Yu W, Yang J, Feng H, Helm M, McMahon E, Zhu X, Shin D, Huang Y. Seizure-dependent mTOR activation in 5-HT neurons promotes autism-like behaviors in mice. Neurobiol Dis 2014; 73:296-306. [PMID: 25315683 DOI: 10.1016/j.nbd.2014.10.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 09/23/2014] [Accepted: 10/01/2014] [Indexed: 11/15/2022] Open
Abstract
Epilepsy and autism spectrum disorder (ASD) are common comorbidities of one another. Despite the prevalent correlation between the two disorders, few studies have been able to elucidate a mechanistic link. We demonstrate that forebrain specific Tsc1 deletion in mice causes epilepsy and autism-like behaviors, concomitant with disruption of 5-HT neurotransmission. We find that epileptiform activity propagates to the raphe nuclei, resulting in seizure-dependent hyperactivation of mTOR in 5-HT neurons. To dissect whether mTOR hyperactivity in 5-HT neurons alone was sufficient to recapitulate an autism-like phenotype we utilized Tsc1flox/flox;Slc6a4-cre mice, in which mTOR is restrictively hyperactivated in 5-HT neurons. Tsc1flox/flox;Slc6a4-cre mice displayed alterations of the 5-HT system and autism-like behaviors, without causing epilepsy. Rapamycin treatment in these mice was sufficient to rescue the phenotype. We conclude that the spread of seizure activity to the brainstem is capable of promoting hyperactivation of mTOR in the raphe nuclei, which in turn promotes autism-like behaviors. Thus our study provides a novel mechanism describing how epilepsy can contribute to the development of autism-like behaviors, suggesting new therapeutic strategies for autism.
Collapse
Affiliation(s)
- John J McMahon
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA
| | - Wilson Yu
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA
| | - Jun Yang
- Center for Cardiovascular Sciences, Albany Medical College, Albany, NY 12208, USA
| | - Haihua Feng
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA
| | - Meghan Helm
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA
| | - Elizabeth McMahon
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA
| | - Xinjun Zhu
- Center for Cardiovascular Sciences, Albany Medical College, Albany, NY 12208, USA
| | - Damian Shin
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA
| | - Yunfei Huang
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA.
| |
Collapse
|
24
|
Neu3 sialidase-mediated ganglioside conversion is necessary for axon regeneration and is blocked in CNS axons. J Neurosci 2014; 34:2477-92. [PMID: 24523539 DOI: 10.1523/jneurosci.4432-13.2014] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
PNS axons have a high intrinsic regenerative ability, whereas most CNS axons show little regenerative response. We show that activation of Neu3 sialidase, also known as Neuraminidase-3, causing conversion of GD1a and GT1b to GM1 ganglioside, is an essential step in regeneration occurring in PNS (sensory) but not CNS (retinal) axons in adult rat. In PNS axons, axotomy activates Neu3 sialidase, increasing the ratio of GM1/GD1a and GM1/GT1b gangliosides immediately after injury in vitro and in vivo. No change in the GM1/GD1a ratio after axotomy was observed in retinal axons (in vitro and in vivo), despite the presence of Neu3 sialidase. Externally applied sialidase converted GD1a ganglioside to GM1 and rescued axon regeneration in CNS axons and in PNS axons after Neu3 sialidase blockade. Neu3 sialidase activation in DRGs is initiated by an influx of extracellular calcium, activating P38MAPK and then Neu3 sialidase. Ganglioside conversion by Neu3 sialidase further activates the ERK pathway. In CNS axons, P38MAPK and Neu3 sialidase were not activated by axotomy.
Collapse
|
25
|
Abstract
Development of the nervous system requires efficient extension and guidance of axons and dendrites culminating in synapse formation. Axonal growth and navigation during embryogenesis are controlled by extracellular cues. Many of the same extracellular signals also regulate axonal branching. The emergence of collateral branches from the axon augments the complexity of nervous system innervation and provides an additional mechanism for target selection. Rho-family GTPases play an important role in regulating intracellular cytoskeletal and signaling pathways that facilitate axonal morphological changes. RhoA/G and Rac1 GTPase functions are complex and they can induce or inhibit branch formation, depending on neuronal type, cell context or signaling mechanisms. Evidence of a role of Cdc42 in axon branching is mostly lacking. In contrast, Rac3 has thus far been implicated in the regulation of axon branching. Future analysis of the upstream regulators and downstream effectors mediating the effects of Rho-family GTPase will provide insights into the cellular processes effected, and shed light on the sometimes opposing roles of these GTPases in the regulation of axon branching.
Collapse
Affiliation(s)
- Mirela Spillane
- Shriners Hospitals Pediatric Research Center; Center for Neural Repair and Rehabilitation; Temple University; Department of Anatomy and Cell Biology; Philadelphia, PA USA
| | - Gianluca Gallo
- Shriners Hospitals Pediatric Research Center; Center for Neural Repair and Rehabilitation; Temple University; Department of Anatomy and Cell Biology; Philadelphia, PA USA
| |
Collapse
|
26
|
Yadav RS, Tiwari NK. Lipid integration in neurodegeneration: an overview of Alzheimer's disease. Mol Neurobiol 2014; 50:168-76. [PMID: 24590317 DOI: 10.1007/s12035-014-8661-5] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 02/11/2014] [Indexed: 12/14/2022]
Abstract
Various types of lipids and their metabolic products associated with the biological membrane play a crucial role in signal transduction, modulation, and activation of receptors and as precursors of bioactive lipid mediators. Dysfunction in the lipid homeostasis in the brain could be a risk factor for the many types of neurodegenerative disorders, including Alzheimer's disease, Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis. These neurodegenerative disorders are marked by extensive neuronal apoptosis, gliosis, and alteration in the differentiation, proliferation, and development of neurons. Sphingomyelin, a constituent of plasma membrane, as well as its primary metabolite ceramide acts as a potential lipid second messenger molecule linked with the modulation of various cellular signaling pathways. Excessive production of reactive oxygen species associated with enhanced oxidative stress has been implicated with these molecules and involved in the regulation of a variety of different neurodegenerative and neuroinflammatory disorders. Studies have shown that alterations in the levels of plasma lipid/cholesterol concentration may result to neurodegenerative diseases. Alteration in the levels of inflammatory cytokines and mediators in the brain has also been found to be implicated in the pathophysiology of neurodegenerative diseases. Although several mechanisms involved in neuronal apoptosis have been described, the molecular mechanisms underlying the correlation between lipid metabolism and the neurological deficits are not clearly understood. In the present review, an attempt has been made to provide detailed information about the association of lipids in neurodegeneration especially in Alzheimer's disease.
Collapse
Affiliation(s)
- Rajesh Singh Yadav
- Department of Criminology and Forensic Science, School of Applied Sciences, Dr. Harisingh Gour Central University, Sagar, MP, 470003, India
| | | |
Collapse
|
27
|
Gururajan A, van den Buuse M. Is the mTOR-signalling cascade disrupted in Schizophrenia? J Neurochem 2013; 129:377-87. [PMID: 24266366 DOI: 10.1111/jnc.12622] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 11/07/2013] [Accepted: 11/10/2013] [Indexed: 02/01/2023]
Abstract
The mammalian target of rapamycin (mTOR) signalling cascade is involved in the intracellular regulation of protein synthesis, specifically for proteins involved in controlling neuronal morphology and facilitating synaptic plasticity. Research has revealed that the activity of the mTOR cascade is influenced by several extracellular and environmental factors that have been implicated in schizophrenia. Therefore, there is reason to believe that one of the downstream consequences of dysfunction or hypofunction of these factors in schizophrenia is disrupted mTOR signalling and hence impaired protein synthesis. This results in abnormal neurodevelopment and deficient synaptic plasticity, outcomes which could underlie some of the positive, negative and cognitive symptoms of schizophrenia. This review will discuss the functional roles of the mTOR cascade and present evidence in support of a novel mTOR-based hypothesis of the neuropathology of schizophrenia. During neurodevelopment, genetic and epigenetic factors can disrupt mTOR signalling which affects synthesis of proteins essential for correct neuronal growth and network connectivity. This renders the CNS particularly vulnerable to the effects of secondary factors during adolescence which increases the risk of developing schizophrenia in adulthood. This review discusses the functional roles of the mTOR cascade and presents evidence in support of a novel mTOR-based hypothesis of the neuropathology of schizophrenia. Testing this hypothesis will advance our understanding of the aetiology of this illness and reveal novel therapeutic targets.
Collapse
Affiliation(s)
- Anand Gururajan
- Behavioural Neuroscience Laboratory, The Florey Institute of Neuroscience & Mental Health, Parkville, Vic., Australia
| | | |
Collapse
|
28
|
Sonnino S, Aureli M, Grassi S, Mauri L, Prioni S, Prinetti A. Lipid Rafts in Neurodegeneration and Neuroprotection. Mol Neurobiol 2013; 50:130-48. [DOI: 10.1007/s12035-013-8614-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 12/08/2013] [Indexed: 11/28/2022]
|
29
|
Lee HG, Zhao N, Campion BK, Nguyen MM, Selleck SB. Akt regulates glutamate receptor trafficking and postsynaptic membrane elaboration at the Drosophila neuromuscular junction. Dev Neurobiol 2013; 73:723-43. [PMID: 23592328 PMCID: PMC4352336 DOI: 10.1002/dneu.22086] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 03/16/2013] [Accepted: 04/12/2013] [Indexed: 12/21/2022]
Abstract
The Akt family of serine-threonine kinases integrates a myriad of signals governing cell proliferation, apoptosis, glucose metabolism, and cytoskeletal organization. Akt affects neuronal morphology and function, influencing dendrite growth and the expression of ion channels. Akt is also an integral element of PI3Kinase-target of rapamycin (TOR)-Rheb signaling, a pathway that affects synapse assembly in both vertebrates and Drosophila. Our recent findings demonstrated that disruption of this pathway in Drosophila is responsible for a number of neurodevelopmental deficits that may also affect phenotypes associated with tuberous sclerosis complex, a disorder resulting from mutations compromising the TSC1/TSC2 complex, an inhibitor of TOR (Dimitroff et al., 2012). Therefore, we examined the role of Akt in the assembly and physiological function of the Drosophila neuromuscular junction (NMJ), a glutamatergic synapse that displays developmental and activity-dependent plasticity. The single Drosophila Akt family member, Akt1 selectively altered the postsynaptic targeting of one glutamate receptor subunit, GluRIIA, and was required for the expansion of a specialized postsynaptic membrane compartment, the subsynaptic reticulum (SSR). Several lines of evidence indicated that Akt1 influences SSR assembly by regulation of Gtaxin, a Drosophila t-SNARE protein (Gorczyca et al., 2007) in a manner independent of the mislocalization of GluRIIA. Our findings show that Akt1 governs two critical elements of synapse development, neurotransmitter receptor localization, and postsynaptic membrane elaboration.
Collapse
Affiliation(s)
- Hyun-Gwan Lee
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802
| | | | | | | | | |
Collapse
|
30
|
Interaction of membrane/lipid rafts with the cytoskeleton: impact on signaling and function: membrane/lipid rafts, mediators of cytoskeletal arrangement and cell signaling. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:532-45. [PMID: 23899502 DOI: 10.1016/j.bbamem.2013.07.018] [Citation(s) in RCA: 378] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 05/14/2013] [Accepted: 07/16/2013] [Indexed: 12/14/2022]
Abstract
The plasma membrane in eukaryotic cells contains microdomains that are enriched in certain glycosphingolipids, gangliosides, and sterols (such as cholesterol) to form membrane/lipid rafts (MLR). These regions exist as caveolae, morphologically observable flask-like invaginations, or as a less easily detectable planar form. MLR are scaffolds for many molecular entities, including signaling receptors and ion channels that communicate extracellular stimuli to the intracellular milieu. Much evidence indicates that this organization and/or the clustering of MLR into more active signaling platforms depends upon interactions with and dynamic rearrangement of the cytoskeleton. Several cytoskeletal components and binding partners, as well as enzymes that regulate the cytoskeleton, localize to MLR and help regulate lateral diffusion of membrane proteins and lipids in response to extracellular events (e.g., receptor activation, shear stress, electrical conductance, and nutrient demand). MLR regulate cellular polarity, adherence to the extracellular matrix, signaling events (including ones that affect growth and migration), and are sites of cellular entry of certain pathogens, toxins and nanoparticles. The dynamic interaction between MLR and the underlying cytoskeleton thus regulates many facets of the function of eukaryotic cells and their adaptation to changing environments. Here, we review general features of MLR and caveolae and their role in several aspects of cellular function, including polarity of endothelial and epithelial cells, cell migration, mechanotransduction, lymphocyte activation, neuronal growth and signaling, and a variety of disease settings. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
Collapse
|
31
|
Varea O, Escoll M, Diez H, Garrido J, Wandosell F. Oestradiol signalling through the Akt–mTORC1–S6K1. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:1052-64. [DOI: 10.1016/j.bbamcr.2012.12.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 12/11/2012] [Accepted: 12/26/2012] [Indexed: 12/12/2022]
|
32
|
Nerve growth factor-induced formation of axonal filopodia and collateral branches involves the intra-axonal synthesis of regulators of the actin-nucleating Arp2/3 complex. J Neurosci 2013; 32:17671-89. [PMID: 23223289 DOI: 10.1523/jneurosci.1079-12.2012] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Nerve growth factor (NGF) induces collateral branching along sensory axons by promoting the formation of axonal filopodia dependent on the actin-nucleating Arp2/3 complex. This study shows that chicken embryonic sensory axons contain mRNAs for the actin-nucleating Arp2/3 complex activator WAVE1 and the complex stabilizer cortactin. NGF increases the axonal levels of WAVE1 and cortactin through localized protein synthesis even in axons isolated from the cell body. Inhibition of protein synthesis in severed axons impairs NGF-induced branching, the formation of axonal filopodia, and the initiation of Arp2/3-dependent axonal actin patches, which serve as precursors to the emergence of filopodia. Overexpression of WAVE1 or cortactin in axons not treated with NGF increased the rate of actin patch formation and the frequency of the emergence of filopodia from actin patches, respectively. Antisense inhibition of cortactin mRNA translation in isolated axons blocked NGF-induced filopodia. NGF also activated the Rac1 GTPase, which drives WAVE1 activity, in a protein synthesis-independent manner. Similarly, inhibition of protein synthesis did not impair the effects of NGF on the axonal microtubule cytoskeleton during branching. The effects of NGF on Rac1 activity and increases in axonal levels of WAVE1 and cortactin were both dependent on phosphoinositide 3-kinase (PI3K) signaling. Collectively, the data indicate that NGF promotes sensory axon branching through regulation of the actin cytoskeleton using both canonical signaling mechanisms and intra-axonal protein synthesis downstream of PI3K signaling. Finally, we present experimental evidence of axonal mRNA translation in sensory axons in the living embryonic spinal cord.
Collapse
|
33
|
Plexin A3 and turnout regulate motor axonal branch morphogenesis in zebrafish. PLoS One 2013; 8:e54071. [PMID: 23349787 PMCID: PMC3549987 DOI: 10.1371/journal.pone.0054071] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 12/10/2012] [Indexed: 02/01/2023] Open
Abstract
During embryogenesis motor axons navigate to their target muscles, where individual motor axons develop complex branch morphologies. The mechanisms that control axonal branching morphogenesis have been studied intensively, yet it still remains unclear when branches begin to form or how branch locations are determined. Live cell imaging of individual zebrafish motor axons reveals that the first axonal branches are generated at the ventral extent of the myotome via bifurcation of the growth cone. Subsequent branches are generated by collateral branching restricted to their synaptic target field along the distal portion of the axon. This precisely timed and spatially restricted branching process is disrupted in turnout mutants we identified in a forward genetic screen. Molecular genetic mapping positioned the turnout mutation within a 300 kb region encompassing eight annotated genes, however sequence analysis of all eight open reading frames failed to unambiguously identify the turnout mutation. Chimeric analysis and single cell labeling reveal that turnout function is required cell non-autonomously for intraspinal motor axon guidance and peripheral branch formation. turnout mutant motor axons form the first branch on time via growth cone bifurcation, but unlike wild-type they form collateral branches precociously, when the growth cone is still navigating towards the ventral myotome. These precocious collateral branches emerge along the proximal region of the axon shaft typically devoid of branches, and they develop into stable, permanent branches. Furthermore, we find that null mutants of the guidance receptor plexin A3 display identical motor axon branching defects, and time lapse analysis reveals that precocious branch formation in turnout and plexin A3 mutants is due to increased stability of otherwise short-lived axonal protrusions. Thus, plexin A3 dependent intrinsic and turnout dependent extrinsic mechanisms suppress collateral branch morphogenesis by destabilizing membrane protrusions before the growth cone completes navigation into the synaptic target field.
Collapse
|
34
|
Hicks DA, Nalivaeva NN, Turner AJ. Lipid rafts and Alzheimer's disease: protein-lipid interactions and perturbation of signaling. Front Physiol 2012; 3:189. [PMID: 22737128 PMCID: PMC3381238 DOI: 10.3389/fphys.2012.00189] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 05/21/2012] [Indexed: 12/16/2022] Open
Abstract
Lipid rafts are membrane domains, more ordered than the bulk membrane and enriched in cholesterol and sphingolipids. They represent a platform for protein-lipid and protein–protein interactions and for cellular signaling events. In addition to their normal functions, including membrane trafficking, ligand binding (including viruses), axonal development and maintenance of synaptic integrity, rafts have also been implicated in the pathogenesis of several neurodegenerative diseases including Alzheimer’s disease (AD). Lipid rafts promote interaction of the amyloid precursor protein (APP) with the secretase (BACE-1) responsible for generation of the amyloid β peptide, Aβ. Rafts also regulate cholinergic signaling as well as acetylcholinesterase and Aβ interaction. In addition, such major lipid raft components as cholesterol and GM1 ganglioside have been directly implicated in pathogenesis of the disease. Perturbation of lipid raft integrity can also affect various signaling pathways leading to cellular death and AD. In this review, we discuss modulation of APP cleavage by lipid rafts and their components, while also looking at more recent findings on the role of lipid rafts in signaling events.
Collapse
Affiliation(s)
- David A Hicks
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds Leeds, UK
| | | | | |
Collapse
|
35
|
Steketee MB, Goldberg JL. Signaling endosomes and growth cone motility in axon regeneration. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2012; 106:35-73. [PMID: 23211459 DOI: 10.1016/b978-0-12-407178-0.00003-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
During development and regeneration, growth cones guide neurites to their targets by altering their motility in response to extracellular guidance cues. One class of cues critical to nervous system development is the neurotrophins. Neurotrophin binding to their cognate receptors stimulates their endocytosis into signaling endosomes. Current data indicate that the spatiotemporal localization of signaling endosomes can direct diverse processes regulating cell motility, including membrane trafficking, cytoskeletal remodeling, adhesion dynamics, and local translation. Recent experiments manipulating signaling endosome localization in neuronal growth cones support these views and place the neurotrophin signaling endosome in a central role regulating growth cone motility during axon growth and regeneration.
Collapse
|
36
|
Kidani Y, Ohshima KI, Sakai H, Kohno T, Baba A, Hattori M. Differential localization of sphingomyelin synthase isoforms in neurons regulates sphingomyelin cluster formation. Biochem Biophys Res Commun 2011; 417:1014-7. [PMID: 22209789 DOI: 10.1016/j.bbrc.2011.12.079] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 12/15/2011] [Indexed: 10/14/2022]
Abstract
Sphingomyelin (SM) plays important roles in regulating structure and function of plasma membrane, but how intracellular localization of SM is regulated in neuronal cells is not understood. Here we show that two isoforms of SM synthase (SMS) are differentially expressed in neuronal subtypes and that only SMS2 proteins localize in neurites of hippocampal neurons. Moreover, SMS proteins induce Lysenin-binding SM clusters exclusively in their vicinity although neurons hardly contain such cluster under control condition. These findings indicate three important notions about SM metabolism in neurons. First, the activity of SMS is the rate-limiting step of SM cluster formation. Second, the SM content or clustering can be modulated by SMS activity. Third, SMS1 and SMS2 play distinct roles in regulating local SM clustering. Particularly, SMS2, rather than SMS1, is likely to be the major enzyme that is important for SM synthesis in the long neurites and its tip, the growth cone.
Collapse
Affiliation(s)
- Yujiro Kidani
- Department of Biomedical Science, Graduate School of Pharmaceutical Sciences, Nagoya City University, Aichi, Japan
| | | | | | | | | | | |
Collapse
|
37
|
Abstract
Axon branching is a complex morphological process, the regulation of which we are just beginning to understand. Many factors known to be important for axon growth and guidance have emerged as key regulators of axon branching. The extrinsic factors implicated in axon branching include traditional axon guidance cues such as the slits, semaphorins, and ephrins; neurotrophins such as BDNF; the secreted glycoprotein Wnt; the extracellular matrix protein anosmin-1; and certain transmembrane cell adhesion molecules--as well as sensory experience and neuronal activity. Although less is known about the intracellular control of axon branching, in recent years significant advances have been made in this area. Kinases and their regulators, Rho GTPases and their regulators, transcription factors, ubiquitin ligases, and several microtubule and actin-binding proteins are now implicated in the control of axon branching. It is likely that many more branching regulators remain to be discovered, as do the links between extrinsic cues and intracellular signaling proteins in the control of axon branching.
Collapse
Affiliation(s)
- Parizad M Bilimoria
- Department of Neurobiology and Program in Neuroscience, Harvard Medical School, Boston, MA, USA
| | | |
Collapse
|
38
|
Abstract
During development, axons are guided to their appropriate targets by a variety of guidance factors. On arriving at their synaptic targets, or while en route, axons form branches. Branches generated de novo from the main axon are termed collateral branches. The generation of axon collateral branches allows individual neurons to make contacts with multiple neurons within a target and with multiple targets. In the adult nervous system, the formation of axon collateral branches is associated with injury and disease states and may contribute to normally occurring plasticity. Collateral branches are initiated by actin filament– based axonal protrusions that subsequently become invaded by microtubules, thereby allowing the branch to mature and continue extending. This article reviews the current knowledge of the cellular mechanisms of the formation of axon collateral branches. The major conclusions of this review are (1) the mechanisms of axon extension and branching are not identical; (2) active suppression of protrusive activity along the axon negatively regulates branching; (3) the earliest steps in the formation of axon branches involve focal activation of signaling pathways within axons, which in turn drive the formation of actin-based protrusions; and (4) regulation of the microtubule array by microtubule-associated and severing proteins underlies the development of branches. Linking the activation of signaling pathways to specific proteins that directly regulate the axonal cytoskeleton underlying the formation of collateral branches remains a frontier in the field.
Collapse
Affiliation(s)
- Gianluca Gallo
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, Pennsylvania 19129, USA.
| |
Collapse
|
39
|
Sakagami K, Chen B, Nusinowitz S, Wu H, Yang XJ. PTEN regulates retinal interneuron morphogenesis and synaptic layer formation. Mol Cell Neurosci 2011; 49:171-83. [PMID: 22155156 DOI: 10.1016/j.mcn.2011.11.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 11/21/2011] [Accepted: 11/26/2011] [Indexed: 11/15/2022] Open
Abstract
The lipid phosphatase PTEN is a critical negative regulator of extracellular signal-induced PI3K activities, yet the roles of PTEN in the neural retina remain poorly understood. Here, we investigate the function of PTEN during retinal development. Deletion of Pten at the onset of neurogenesis in retinal progenitors results in the reduction of retinal ganglion cells and rod photoreceptors, but increased Müller glial genesis. In addition, PTEN deficiency leads to elevated phosphorylation of Akt, especially in the developing inner plexiform layer, where high levels of PTEN are normally expressed. In Pten mutant retinas, various subtypes of amacrine cells show severe dendritic overgrowth, causing specific expansion of the inner plexiform layer. However, the outer plexiform layer remains relatively undisturbed in the Pten deficient retina. Physiological analysis detects reduced rod function and augmented oscillatory potentials originating from amacrine cells in Pten mutants. Furthermore, deleting Pten or elevating Akt activity in individual amacrine cells is sufficient to disrupt dendritic arborization, indicating that Pten activity is required cell autonomously to control neuronal morphology. Moreover, inhibiting endogenous Akt activity attenuates inner plexiform layer formation in vitro. Together, these findings demonstrate that suppression of PI3K/Akt signaling by PTEN is crucial for proper neuronal differentiation and normal retinal network formation.
Collapse
Affiliation(s)
- Kiyo Sakagami
- Jules Stein Eye Institute, University of California, Los Angeles, CA 90095, USA
| | | | | | | | | |
Collapse
|
40
|
Sunnen CN, Brewster AL, Lugo JN, Vanegas F, Turcios E, Mukhi S, Parghi D, D'Arcangelo G, Anderson AE. Inhibition of the mammalian target of rapamycin blocks epilepsy progression in NS-Pten conditional knockout mice. Epilepsia 2011; 52:2065-75. [PMID: 21973019 DOI: 10.1111/j.1528-1167.2011.03280.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE Increased activity of mTOR Complex 1 (mTORC1) has been demonstrated in cortical dysplasia and tuberous sclerosis complex, as well as in animal models of epilepsy. Recent studies in such models revealed that inhibiting mTORC1 with rapamycin effectively suppressed seizure activity. However, seizures can recur after treatment cessation, and continuous rapamycin exposure can adversely affect animal growth and health. Here, we evaluated the efficacy of an intermittent rapamycin treatment protocol on epilepsy progression using neuron subset-specific-Pten (NS-Pten) conditional knockout mice. METHODS NS-Pten knockouts were treated with a single course of rapamycin during postnatal weeks 4 and 5, or intermittently over a period of 5 months. Epileptiform activity was monitored using video-electroencephalography (EEG) recordings, and mossy fiber sprouting was evaluated using Timm staining. Survival and body weight were assessed in parallel. KEY FINDINGS NS-Pten knockouts treated with a single course of rapamycin had recurrence of epilepsy 4-7 weeks after treatment ended. In contrast, epileptiform activity remained suppressed, and survival increased if knockout mice received additional rapamycin during weeks 10-11 and 16-17. Aberrant mossy fiber sprouting, present by 4 weeks of age and progressing in parallel with epileptiform activity, was also blocked by rapamycin. SIGNIFICANCE These findings demonstrate that a single course of rapamycin treatment suppresses epileptiform activity and mossy fiber sprouting for several weeks before epilepsy recurs. However, additional intermittent treatments with rapamycin prevented this recurrence and enhanced survival without compromising growth. Therefore, these studies add to the growing body of evidence implicating an important role for mTORC1 signaling in epilepsy.
Collapse
Affiliation(s)
- C Nicole Sunnen
- The Cain Foundation Laboratories and The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Greene LA, Levy O, Malagelada C. Akt as a victim, villain and potential hero in Parkinson's disease pathophysiology and treatment. Cell Mol Neurobiol 2011; 31:969-78. [PMID: 21547489 PMCID: PMC3678379 DOI: 10.1007/s10571-011-9671-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 02/24/2011] [Indexed: 12/25/2022]
Abstract
There are two major purposes of this essay. The first is to summarize existing evidence that irrespective of the initiating causes, neuron death and degeneration in Parkinson's disease (PD) are due to the common feature of failure of signaling by Akt, a kinase involved in neuron survival and maintenance of synaptic contacts. The second is to consider possible means by which such a failure of Akt signaling might be benignly prevented or reversed in neurons affected by PD, so as to treat PD symptoms, block disease progression, and potentially, promote recovery.
Collapse
Affiliation(s)
- Lloyd A Greene
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, 630W. 168th Street, New York, NY 10032, USA.
| | | | | |
Collapse
|
42
|
Du J, Xu R, Hu Z, Tian Y, Zhu Y, Gu L, Zhou L. PI3K and ERK-induced Rac1 activation mediates hypoxia-induced HIF-1α expression in MCF-7 breast cancer cells. PLoS One 2011; 6:e25213. [PMID: 21980400 PMCID: PMC3181265 DOI: 10.1371/journal.pone.0025213] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 08/29/2011] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Hypoxia-inducible factor 1 (HIF-1α) expression induced by hypoxia plays a critical role in promoting tumor angiogenesis and metastasis. However, the molecular mechanisms underlying the induction of HIF-1α in tumor cells remain unknown. METHODOLOGY/PRINCIPAL FINDINGS In this study, we reported that hypoxia could induce HIF-1α and VEGF expression accompanied by Rac1 activation in MCF-7 breast cancer cells. Blockade of Rac1 activation with ectopic expression of an inactive mutant form of Rac1 (T17N) or Rac1 siRNA downregulated hypoxia-induced HIF-1α and VEGF expression. Furthermore, Hypoxia increased PI3K and ERK signaling activity. Both PI3K inhibitor LY294002 and ERK inhibitor U0126 suppressed hypoxia-induced Rac1 activation as well as HIF-1α expression. Moreover, hypoxia treatment resulted in a remarkable production of reactive oxygen species (ROS). N-acetyl-L-cysteine, a scavenger of ROS, inhibited hypoxia-induced ROS generation, PI3K, ERK and Rac1 activation as well as HIF-1α expression. CONCLUSIONS/SIGNIFICANCE Taken together, our study demonstrated that hypoxia-induced HIF-1α expression involves a cascade of signaling events including ROS generation, activation of PI3K and ERK signaling, and subsequent activation of Rac1.
Collapse
Affiliation(s)
- Jun Du
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Rui Xu
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
- Department of Physiology, Nanjing Medical University, Nanjing, China
| | - Zhenzhen Hu
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
- Department of Physiology, Nanjing Medical University, Nanjing, China
| | - Yinhui Tian
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
- Department of Physiology, Nanjing Medical University, Nanjing, China
| | - Yichao Zhu
- Cancer Center, Nanjing Medical University, Nanjing, China
| | - Luo Gu
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
- Cancer Center, Nanjing Medical University, Nanjing, China
| | - Lei Zhou
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| |
Collapse
|
43
|
Buckmaster PS, Wen X. Rapamycin suppresses axon sprouting by somatostatin interneurons in a mouse model of temporal lobe epilepsy. Epilepsia 2011; 52:2057-64. [PMID: 21883182 DOI: 10.1111/j.1528-1167.2011.03253.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
PURPOSE In temporal lobe epilepsy many somatostatin interneurons in the dentate gyrus die. However, some survive and sprout axon collaterals that form new synapses with granule cells. The functional consequences of γ-aminobutyric acid (GABA)ergic synaptic reorganization are unclear. Development of new methods to suppress epilepsy-related interneuron axon sprouting might be useful experimentally. METHODS Status epilepticus was induced by systemic pilocarpine treatment in green fluorescent protein (GFP)-expressing inhibitory nerurons (GIN) mice in which a subset of somatostatin interneurons expresses GFP. Beginning 24 h later, mice were treated with vehicle or rapamycin (3 mg/kg intraperitoneally) every day for 2 months. Stereologic methods were then used to estimate numbers of GFP-positive hilar neurons per dentate gyrus and total length of GFP-positive axon in the molecular layer plus granule cell layer. GFP-positive axon density was calculated. The number of GFP-positive axon crossings of the granule cell layer was measured. Regression analyses were performed to test for correlations between GFP-positive axon length versus number of granule cells and dentate gyrus volume. KEY FINDINGS After pilocarpine-induced status epilepticus, rapamycin- and vehicle-treated mice had approximately half as many GFP-positive hilar neurons as did control animals. Despite neuron loss, vehicle-treated mice had over twice the GFP-positive axon length per dentate gyrus as controls, consistent with GABAergic axon sprouting. In contrast, total GFP-positive axon length was similar in rapamycin-treated mice and controls. GFP-positive axon length correlated most closely with dentate gyrus volume. SIGNIFICANCE These findings suggest that rapamycin suppressed axon sprouting by surviving somatostatin/GFP-positive interneurons after pilocarpine-induced status epilepticus in GIN mice. It is unclear whether the effect of rapamycin on axon length was on interneurons directly or secondary, for example, by suppressing growth of granule cell dendrites, which are synaptic targets of interneuron axons. The mammalian target of rapamycin (mTOR) signaling pathway might be a useful drug target for influencing GABAergic synaptic reorganization after epileptogenic treatments, but additional side effects of rapamycin treatment must be considered carefully.
Collapse
Affiliation(s)
- Paul S Buckmaster
- Department of Comparative Medicine, Stanford University, Stanford, California 94305, USA.
| | | |
Collapse
|
44
|
Head BP, Hu Y, Finley JC, Saldana MD, Bonds JA, Miyanohara A, Niesman IR, Ali SS, Murray F, Insel PA, Roth DM, Patel HH, Patel PM. Neuron-targeted caveolin-1 protein enhances signaling and promotes arborization of primary neurons. J Biol Chem 2011; 286:33310-21. [PMID: 21799010 DOI: 10.1074/jbc.m111.255976] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Decreased expression of prosurvival and progrowth-stimulatory pathways, in addition to an environment that inhibits neuronal growth, contribute to the limited regenerative capacity in the central nervous system following injury or neurodegeneration. Membrane/lipid rafts, plasmalemmal microdomains enriched in cholesterol, sphingolipids, and the protein caveolin (Cav) are essential for synaptic development/stabilization and neuronal signaling. Cav-1 concentrates glutamate and neurotrophin receptors and prosurvival kinases and regulates cAMP formation. Here, we show that primary neurons that express a synapsin-driven Cav-1 vector (SynCav1) have increased raft formation, neurotransmitter and neurotrophin receptor expression, NMDA- and BDNF-mediated prosurvival kinase activation, agonist-stimulated cAMP formation, and dendritic growth. Moreover, expression of SynCav1 in Cav-1 KO neurons restores NMDA- and BDNF-mediated signaling and enhances dendritic growth. The enhanced dendritic growth occurred even in the presence of inhibitory cytokines (TNFα, IL-1β) and myelin-associated glycoproteins (MAG, Nogo). Targeting of Cav-1 to neurons thus enhances prosurvival and progrowth signaling and may be a novel means to repair the injured and neurodegenerative brain.
Collapse
Affiliation(s)
- Brian P Head
- Department of Anesthesiology, University of California, San Diego, La Jolla, California 92093, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Rapamycin suppresses mossy fiber sprouting but not seizure frequency in a mouse model of temporal lobe epilepsy. J Neurosci 2011; 31:2337-47. [PMID: 21307269 DOI: 10.1523/jneurosci.4852-10.2011] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Temporal lobe epilepsy is prevalent and can be difficult to treat effectively. Granule cell axon (mossy fiber) sprouting is a common neuropathological finding in patients with mesial temporal lobe epilepsy, but its role in epileptogenesis is unclear and controversial. Focally infused or systemic rapamycin inhibits the mammalian target of rapamycin (mTOR) signaling pathway and suppresses mossy fiber sprouting in rats. We tested whether long-term systemic treatment with rapamycin, beginning 1 d after pilocarpine-induced status epilepticus in mice, would suppress mossy fiber sprouting and affect the development of spontaneous seizures. Mice that had experienced status epilepticus and were treated for 2 months with rapamycin displayed significantly less mossy fiber sprouting (42% of vehicle-treated animals), and the effect was dose dependent. However, behavioral and video/EEG monitoring revealed that rapamycin- and vehicle-treated mice displayed spontaneous seizures at similar frequencies. These findings suggest mossy fiber sprouting is neither pro- nor anti-convulsant; however, there are caveats. Rapamycin treatment also reduced epilepsy-related hypertrophy of the dentate gyrus but did not significantly affect granule cell proliferation, hilar neuron loss, or generation of ectopic granule cells. These findings are consistent with the hypotheses that hilar neuron loss and ectopic granule cells might contribute to temporal lobe epileptogenesis.
Collapse
|
46
|
Latanoprost Promotes Neurite Outgrowth in Differentiated RGC-5 Cells via the PI3K-Akt-mTOR Signaling Pathway. Cell Mol Neurobiol 2011; 31:597-604. [DOI: 10.1007/s10571-011-9653-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 01/12/2011] [Indexed: 12/21/2022]
|
47
|
Head BP, Peart JN, Panneerselvam M, Yokoyama T, Pearn ML, Niesman IR, Bonds JA, Schilling JM, Miyanohara A, Headrick J, Ali SS, Roth DM, Patel PM, Patel HH. Loss of caveolin-1 accelerates neurodegeneration and aging. PLoS One 2010; 5:e15697. [PMID: 21203469 PMCID: PMC3009734 DOI: 10.1371/journal.pone.0015697] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 11/29/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The aged brain exhibits a loss in gray matter and a decrease in spines and synaptic densities that may represent a sequela for neurodegenerative diseases such as Alzheimer's. Membrane/lipid rafts (MLR), discrete regions of the plasmalemma enriched in cholesterol, glycosphingolipids, and sphingomyelin, are essential for the development and stabilization of synapses. Caveolin-1 (Cav-1), a cholesterol binding protein organizes synaptic signaling components within MLR. It is unknown whether loss of synapses is dependent on an age-related loss of Cav-1 expression and whether this has implications for neurodegenerative diseases such as Alzheimer's disease. METHODOLOGY/PRINCIPAL FINDINGS We analyzed brains from young (Yg, 3-6 months), middle age (Md, 12 months), aged (Ag, >18 months), and young Cav-1 KO mice and show that localization of PSD-95, NR2A, NR2B, TrkBR, AMPAR, and Cav-1 to MLR is decreased in aged hippocampi. Young Cav-1 KO mice showed signs of premature neuronal aging and degeneration. Hippocampi synaptosomes from Cav-1 KO mice showed reduced PSD-95, NR2A, NR2B, and Cav-1, an inability to be protected against cerebral ischemia-reperfusion injury compared to young WT mice, increased Aβ, P-Tau, and astrogliosis, decreased cerebrovascular volume compared to young WT mice. As with aged hippocampi, Cav-1 KO brains showed significantly reduced synapses. Neuron-targeted re-expression of Cav-1 in Cav-1 KO neurons in vitro decreased Aβ expression. CONCLUSIONS Therefore, Cav-1 represents a novel control point for healthy neuronal aging and loss of Cav-1 represents a non-mutational model for Alzheimer's disease.
Collapse
Affiliation(s)
- Brian P. Head
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
- VA San Diego Healthcare System, San Diego, California, United States of America
| | - Jason N. Peart
- Heart Foundation Research Centre, Griffith University, Gold Coast, Queensland, Australia
| | - Mathivadhani Panneerselvam
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
| | - Takaakira Yokoyama
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
| | - Matthew L. Pearn
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
| | - Ingrid R. Niesman
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
| | - Jacqueline A. Bonds
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
| | - Jan M. Schilling
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
- VA San Diego Healthcare System, San Diego, California, United States of America
| | - Atsushi Miyanohara
- Gene Therapy Program, University of California San Diego, La Jolla, California, United States of America
| | - John Headrick
- Heart Foundation Research Centre, Griffith University, Gold Coast, Queensland, Australia
| | - Sameh S. Ali
- Department of Medicine, University of California, La Jolla, California, United States of America
| | - David M. Roth
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
- VA San Diego Healthcare System, San Diego, California, United States of America
| | - Piyush M. Patel
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
- VA San Diego Healthcare System, San Diego, California, United States of America
| | - Hemal H. Patel
- Department of Anesthesiology, University of California San Diego, La Jolla, California, United States of America
- VA San Diego Healthcare System, San Diego, California, United States of America
| |
Collapse
|
48
|
Prion protein interaction with stress-inducible protein 1 enhances neuronal protein synthesis via mTOR. Proc Natl Acad Sci U S A 2010; 107:13147-52. [PMID: 20615969 DOI: 10.1073/pnas.1000784107] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Transmissible spongiform encephalopathies are fatal neurodegenerative diseases caused by the conversion of prion protein (PrP(C)) into an infectious isoform (PrP(Sc)). How this event leads to pathology is not fully understood. Here we demonstrate that protein synthesis in neurons is enhanced via PrP(C) interaction with stress-inducible protein 1 (STI1). We also show that neuroprotection and neuritogenesis mediated by PrP(C)-STI1 engagement are dependent upon the increased protein synthesis mediated by PI3K-mTOR signaling. Strikingly, the translational stimulation mediated by PrP(C)-STI1 binding is corrupted in neuronal cell lines persistently infected with PrP(Sc), as well as in primary cultured hippocampal neurons acutely exposed to PrP(Sc). Consistent with this, high levels of eukaryotic translation initiation factor 2alpha (eIF2alpha) phosphorylation were found in PrP(Sc)-infected cells and in neurons acutely exposed to PrP(Sc). These data indicate that modulation of protein synthesis is critical for PrP(C)-STI1 neurotrophic functions, and point to the impairment of this process during PrP(Sc) infection as a possible contributor to neurodegeneration.
Collapse
|
49
|
Nemoto T, Satoh S, Maruta T, Kanai T, Yoshikawa N, Miyazaki S, Yanagita T, Wada A. Homologous posttranscriptional regulation of insulin-like growth factor-I receptor level via glycogen synthase kinase-3beta and mammalian target of rapamycin in adrenal chromaffin cells: effect on tau phosphorylation. Neuropharmacology 2010; 58:1097-108. [PMID: 20144629 DOI: 10.1016/j.neuropharm.2010.01.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2009] [Revised: 01/02/2010] [Accepted: 01/29/2010] [Indexed: 01/03/2023]
Abstract
In cultured bovine adrenal chromaffin cells, approximately 24 h-treatment with insulin-like growth factor-I (IGF-I) decreased cell surface (125)I-IGF-I binding capacity and IGF-I receptor protein level by approximately 64% (EC(50) = 5.0 nM; t(1/2) = approximately 7 h). IGF-I-induced IGF-I receptor decrease was abolished by LY294002 (phosphoinositide 3-kinase inhibitor) and partially attenuated by rapamycin (an inhibitor of mammalian target of rapamycin [mTOR]). SB216763 (an inhibitor of glycogen synthase kinase-3 [GSK-3]) down-regulated IGF-I receptor, which was further decreased by IGF-I. IGF-I increased inhibitory Ser(9)-phosphorylation of GSK-3beta and stimulatory Ser(2448)-phosphorylation of mTOR. l-leucine increased phosphorylation of mTOR (but not GSK-3beta), and down-regulated IGF-I receptor, both events being abolished by rapamycin. IGF-I-induced IGF-I receptor decrease was not prevented by proteolysis inhibitors. Pulse-label with [(35)S]methionine/cysteine followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that SB216763 or L-leucine retarded synthesis of IGF-I receptor and its precursor molecule. SB216763 (but not l-leucine) destabilized IGF-I receptor mRNA and decreased its level, without changing IGF-I receptor gene transcription. In SB216763-treated cells, IGF-I-induced Tyr-autophosphorylation of IGF-I receptor was decreased by 36%, compared to nontreated cells. IGF-I attenuated constitutive Ser(396)-phosphorylation of tau by 30% in nontreated cells, but not in SB216763-treated cells. IGF-I-induced down-regulations of (125)I-IGF-I binding and IGF-I receptor, as well as IGF-I-induced phosphorylations of GSK-3beta and mTOR were restored to the control levels of nontreated cells after washout of IGF-I (10 nM for 12 h)-treated cells. Thus, IGF-I down-regulated functional IGF-I receptor via GSK-3beta inhibition and mTOR activation; constitutive activity of GSK-3beta maintained IGF-I receptor level in nonstimulated cells.
Collapse
Affiliation(s)
- Takayuki Nemoto
- Department of Pharmacology, Miyazaki Medical College, University of Miyazaki, Miyazaki, Japan
| | | | | | | | | | | | | | | |
Collapse
|