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Zhang H, Ben Zablah Y, Zhang H, Jia Z. Rho Signaling in Synaptic Plasticity, Memory, and Brain Disorders. Front Cell Dev Biol 2021; 9:729076. [PMID: 34671600 PMCID: PMC8520953 DOI: 10.3389/fcell.2021.729076] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 09/03/2021] [Indexed: 12/12/2022] Open
Abstract
Memory impairments are associated with many brain disorders such as autism, Alzheimer's disease, and depression. Forming memories involves modifications of synaptic transmission and spine morphology. The Rho family small GTPases are key regulators of synaptic plasticity by affecting various downstream molecules to remodel the actin cytoskeleton. In this paper, we will review recent studies on the roles of Rho proteins in the regulation of hippocampal long-term potentiation (LTP) and long-term depression (LTD), the most extensively studied forms of synaptic plasticity widely regarded as cellular mechanisms for learning and memory. We will also discuss the involvement of Rho signaling in spine morphology, the structural basis of synaptic plasticity and memory formation. Finally, we will review the association between brain disorders and abnormalities of Rho function. It is expected that studying Rho signaling at the synapse will contribute to the understanding of how memory is formed and disrupted in diseases.
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Affiliation(s)
- Haorui Zhang
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Youssif Ben Zablah
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Haiwang Zhang
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Zhengping Jia
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
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2
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Suica VI, Uyy E, Boteanu RM, Ivan L, Antohe F. Alteration of actin dependent signaling pathways associated with membrane microdomains in hyperlipidemia. Proteome Sci 2015; 13:30. [PMID: 26628893 PMCID: PMC4666118 DOI: 10.1186/s12953-015-0087-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 11/24/2015] [Indexed: 01/05/2023] Open
Abstract
Background Membrane microdomains represent dynamic membrane nano-assemblies enriched in signaling molecules suggesting their active involvement in not only physiological but also pathological molecular processes. The hyperlipidemic stress is a major risk factor of atherosclerosis, but its exact mechanisms of action at the membrane microdomains level remain elusive. The aim of the present study was to determine whether membrane-cytoskeleton proteome in the pulmonary tissue could be modulated by the hyperlipidemic stress, a major risk factor of atherosclerosis. Results High resolution mass spectrometry based proteomics analysis was performed for detergent resistant membrane microdomains isolated from lung homogenates of control, ApoE deficient and statin treated ApoE deficient mice. The findings of the study allowed the identification with high confidence of 1925 proteins, 291 of which were found significantly altered by the modified genetic background, by the statin treatment or both conditions. Principal component analysis revealed a proximal partitioning of the biological replicates, but also a distinct spatial scattering of the sample groups, highlighting different quantitative profiles. The statistical significant over-representation of Regulation of actin cytoskeleton, Focal adhesion and Adherens junction Kyoto Encyclopedia of Genes and Genomes signaling pathways was demonstrated through bioinformatics analysis. The three inter-relation maps comprised 29 of regulated proteins, proving membrane-cytoskeleton coupling targeting and alteration by hyperlipidemia and/or statin treatment. Conclusions The findings of the study allowed the identification with high confidence of the main proteins modulated by the hyperlipidemic stress involved in the actin-dependent pathways. Our study provides the basis for future work probing how the protein activities at the membrane-cytoskeleton interface are dependent upon genetic induced hyperlipidemia. Electronic supplementary material The online version of this article (doi:10.1186/s12953-015-0087-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Viorel-Iulian Suica
- Institute of Cellular Biology and Pathology "Nicolae Simionescu", 8 BP Hasdeu Street, PO Box 35-14, 050568 Bucharest, Romania
| | - Elena Uyy
- Institute of Cellular Biology and Pathology "Nicolae Simionescu", 8 BP Hasdeu Street, PO Box 35-14, 050568 Bucharest, Romania
| | - Raluca Maria Boteanu
- Institute of Cellular Biology and Pathology "Nicolae Simionescu", 8 BP Hasdeu Street, PO Box 35-14, 050568 Bucharest, Romania
| | - Luminita Ivan
- Institute of Cellular Biology and Pathology "Nicolae Simionescu", 8 BP Hasdeu Street, PO Box 35-14, 050568 Bucharest, Romania
| | - Felicia Antohe
- Institute of Cellular Biology and Pathology "Nicolae Simionescu", 8 BP Hasdeu Street, PO Box 35-14, 050568 Bucharest, Romania
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3
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Bolognin S, Lorenzetto E, Diana G, Buffelli M. The potential role of rho GTPases in Alzheimer's disease pathogenesis. Mol Neurobiol 2014; 50:406-22. [PMID: 24452387 DOI: 10.1007/s12035-014-8637-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 01/02/2014] [Indexed: 02/07/2023]
Abstract
Alzheimer's disease (AD) is characterized by a wide loss of synapses and dendritic spines. Despite extensive efforts, the molecular mechanisms driving this detrimental alteration have not yet been determined. Among the factors potentially mediating this loss of neuronal connectivity, the contribution of Rho GTPases is of particular interest. This family of proteins is classically considered a key regulator of actin cytoskeleton remodeling and dendritic spine maintenance, but new insights into the complex dynamics of its regulation have recently determined how its signaling cascade is still largely unknown, both in physiological and pathological conditions. Here, we review the growing evidence supporting the potential involvement of Rho GTPases in spine loss, which is a unanimously recognized hallmark of early AD pathogenesis. We also discuss some new insights into Rho GTPase signaling framework that might explain several controversial results that have been published. The study of the connection between AD and Rho GTPases represents a quite unchartered avenue that holds therapeutic potential.
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Affiliation(s)
- Silvia Bolognin
- Department of Neurological and Movement Sciences, Section of Physiology, University of Verona, Strada le Grazie 8, 37134, Verona, Italy,
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Geörg M, Maudsdotter L, Tavares R, Jonsson AB. Meningococcal resistance to antimicrobial peptides is mediated by bacterial adhesion and host cell RhoA and Cdc42 signalling. Cell Microbiol 2013; 15:1938-54. [PMID: 23834289 DOI: 10.1111/cmi.12163] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 06/06/2013] [Accepted: 06/28/2013] [Indexed: 11/28/2022]
Abstract
Antimicrobial peptides (AMPs) constitute an essential part of the innate immune defence. Pathogenic bacteria have evolved numerous strategies to withstand AMP-mediated killing. The influence of host epithelia on bacterial AMP resistance is, however, still largely unknown. We found that adhesion to pharyngeal epithelial cells protected Neisseria meningitidis, a leading cause of meningitis and sepsis, from the human cathelicidin LL-37, the cationic model amphipathic peptide (MAP) and the peptaibol alamethicin, but not from polymyxin B. Adhesion to primary airway epithelia resulted in a similar increase in LL-37 resistance. The inhibition of selective host cell signalling mediated by RhoA and Cdc42 was found to abolish the adhesion-induced LL-37 resistance by a mechanism unrelated to the actin cytoskeleton. Moreover, N. meningitidis triggered the formation of cholesterol-rich membrane microdomains in pharyngeal epithelial cells, and host cell cholesterol proved to be essential for adhesion-induced resistance. Our data highlight the importance of Rho GTPase-dependent host cell signalling for meningococcal AMP resistance. These results indicate that N. meningitidis selectively exploits the epithelial microenvironment in order to protect itself from LL-37.
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Affiliation(s)
- Miriam Geörg
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
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Mishra M, Del Valle L, Otte J, Darbinian N, Gordon J. Pur-alpha regulates RhoA developmental expression and downstream signaling. J Cell Physiol 2012; 228:65-72. [PMID: 22553010 DOI: 10.1002/jcp.24105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Pur-alpha is an essential protein for postnatal brain development which localizes specifically to dendrites where it plays a role in the translation of neuronal RNA. Mice lacking Pur-alpha display decreased neuronogenesis and impaired neuronal differentiation. Here we examined two Rho GTPases, Rac1 and RhoA, which play opposing roles in neurite outgrowth and are critical for dendritic maturation during mouse brain development in the presence and absence of Pur-alpha. Pur-alpha is developmentally regulated in the mouse brain with expression beginning shortly after birth and rapidly increasing to peak during the third week of postnatal development. RhoA levels analyzed by Western blotting rapidly fluctuated in the wild-type mouse brain, however, in the absence of Pur-alpha, a decrease in RhoA levels shortly after birth and a delay in the cycling of RhoA regulation was observed leading to reduced basal levels of RhoA after day 10 postnatal. Immunohistochemistry of brain tissues displayed reduced RhoA levels in the cortex and cerebellum and loss of perinuclear cytoplasmic labeling of RhoA within the cortex in the knockout mouse brain. While Rac1 levels remained relatively stable at all time points during development and were similar in both wild-type and Pur-alpha knockout mice, changes in subcellular localization of Rac1 were seen in the absence of Pur-alpha. These findings suggest that Pur-alpha can regulate RhoA at multiple levels including basal protein levels, subcellular compartmentalization, as well as turnover of active RhoA in order to promote dendritic maturation.
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Affiliation(s)
- Mamata Mishra
- Department of Neuroscience and Center for Neurovirology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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Gualdoni S, Albertinazzi C, Corbetta S, Valtorta F, de Curtis I. Normal levels of Rac1 are important for dendritic but not axonal development in hippocampal neurons. Biol Cell 2012; 99:455-64. [PMID: 17428196 DOI: 10.1042/bc20060119] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND INFORMATION Rho family GTPases are required for cytoskeletal reorganization and are considered important for the maturation of neurons. Among these proteins, Rac1 is known to play a crucial role in the regulation of actin dynamics, and a number of studies indicate the involvement of this protein in different steps of vertebrate neuronal maturation. There are two distinct Rac proteins expressed in neurons, namely the ubiquitous Rac1 and the neuron-specific Rac3. The specific functions of each of these GTPases during early neuronal development are largely unknown. RESULTS The combination of the knockout of Rac3 with Rac1 down-regulation by siRNA (small interfering RNA) has been used to show that down-regulation of Rac1 affects dendritic development in mouse hippocampal neurons, without affecting axons. F-actin levels are strongly decreased in neuronal growth cones following down-regulation of Rac1, and time-lapse analysis indicated that the reduction of Rac1 levels decreases growth-cone dynamics. CONCLUSIONS These results show that normal levels of endogenous Rac1 activity are critical for early dendritic development, whereas dendritic outgrowth is not affected in hippocampal neurons from Rac3-null mice. On the other hand, early axonal development appears normal after Rac1 down-regulation. Our findings also suggest that the initial establishment of neuronal polarity is not affected by Rac1 down-regulation.
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Affiliation(s)
- Sara Gualdoni
- Dibit, San Raffaele Scientific Institute, Milano, Italy
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7
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Takemoto-Kimura S, Suzuki K, Kamijo S, Ageta-Ishihara N, Fujii H, Okuno H, Bito H. Differential roles for CaM kinases in mediating excitation-morphogenesis coupling during formation and maturation of neuronal circuits. Eur J Neurosci 2010; 32:224-30. [DOI: 10.1111/j.1460-9568.2010.07353.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Sigma-1 receptors regulate hippocampal dendritic spine formation via a free radical-sensitive mechanism involving Rac1xGTP pathway. Proc Natl Acad Sci U S A 2009; 106:22468-73. [PMID: 20018732 DOI: 10.1073/pnas.0909089106] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Sigma-1 receptors (Sig-1Rs) are endoplasmic reticulum (ER)-resident proteins known to be involved in learning and memory. Dendritic spines in hippocampal neurons play important roles in neuroplasticity and learning and memory. This study tested the hypothesis that Sig-1Rs might regulate denritic spine formation in hippocampal neurons and examined potential mechanisms therein. In rat hippocampal primary neurons, the knockdown of Sig-1Rs by siRNAs causes a deficit in the formation of dendritic spines that is unrelated to ER Ca(2+) signaling or apoptosis, but correlates with the mitochondrial permeability transition and cytochrome c release, followed by caspase-3 activation, Tiam1 cleavage, and a reduction in Rac1.GTP. Sig-1R-knockdown neurons contain higher levels of free radicals when compared to control neurons. The activation of superoxide dismutase or the application of the hydroxyl-free radical scavenger N-acetyl cysteine (NAC) to the Sig-1R-knockdown neurons rescues dendritic spines and mitochondria from the deficits caused by Sig-1R siRNA. Further, the caspase-3-resistant TIAM1 construct C1199DN, a stable guanine exchange factor able to constitutively activate Rac1 in the form of Rac1.GTP, also reverses the siRNA-induced dendritic spine deficits. In addition, constitutively active Rac1.GTP reverses this deficit. These results implicate Sig-1Rs as endogenous regulators of hippopcampal dendritic spine formation and suggest a free radical-sensitive ER-mitochondrion-Rac1.GTP pathway in the regulation of dendritic spine formation in the hippocampus.
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Odagaki SI, Kumanogoh H, Nakamura S, Maekawa S. Biochemical interaction of an actin-capping protein, CapZ, with NAP-22. J Neurosci Res 2009; 87:1980-5. [DOI: 10.1002/jnr.22040] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Li H, Han W, Villar VAM, Keever LB, Lu Q, Hopfer U, Quinn MT, Felder RA, Jose PA, Yu P. D1-like receptors regulate NADPH oxidase activity and subunit expression in lipid raft microdomains of renal proximal tubule cells. Hypertension 2009; 53:1054-61. [PMID: 19380616 DOI: 10.1161/hypertensionaha.108.120642] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
NADPH oxidase (Nox)-dependent reactive oxygen species production is implicated in the pathogenesis of cardiovascular diseases, including hypertension. We tested the hypothesis that oxidase subunits are differentially regulated in renal proximal tubules from normotensive and spontaneously hypertensive rats. Basal Nox2 and Nox4, but not Rac1, in immortalized renal proximal tubule cells and brush border membranes were greater in hypertensive than in normotensive rats. However, more Rac1 was expressed in lipid rafts in cells from hypertensive rats than in cells from normotensive rats; the converse was observed with Nox4, whereas Nox2 expression was similar. The D(1)-like receptor agonist fenoldopam decreased Nox2 and Rac1 protein in lipid rafts to a greater extent in hypertensive than in normotensive rats. Basal oxidase activity was 3-fold higher in hypertensive than in normotensive rats but was inhibited to a greater extent by fenoldopam in normotensive (58+/-3.3%) than in hypertensive rats (31+/-5.2%; P<0.05; n=6 per group). Fenoldopam decreased the amount of Nox2 that coimmunoprecipitated with p67(phox) in cells from normotensive rats. D(1)-like receptors may decrease oxidase activity by disrupting the distribution and assembly of oxidase subunits in cell membrane microdomains. The cholesterol-depleting reagent methyl-beta-cyclodextrin decreased oxidase activity and cholesterol content to a greater extent in hypertensive than in normotensive rats. The greater basal levels of Nox2 and Nox4 in cell membranes and Nox2 and Rac1 in lipid rafts in hypertensive rats than in normotensive rats may explain the increased basal oxidase activity in hypertensive rats.
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Affiliation(s)
- Hewang Li
- Center for Molecular Physiology Research, Children's National Medical Center, Washington, DC 20010, USA
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11
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Liu GJ, Nagarajah R, Banati RB, Bennett MR. Glutamate induces directed chemotaxis of microglia. Eur J Neurosci 2009; 29:1108-18. [DOI: 10.1111/j.1460-9568.2009.06659.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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12
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Expression of Rho GTPases Rho‐A and Rac1 in the adult and developing gerbil cerebellum. Int J Dev Neurosci 2008; 26:723-32. [DOI: 10.1016/j.ijdevneu.2008.07.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 07/06/2008] [Accepted: 07/07/2008] [Indexed: 12/21/2022] Open
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Tsuda R, Kumanogoh H, Umeda M, Maekawa S. Morphological analysis on the distribution of membrane lipids and a membrane protein, NAP-22, during neuronal development in vitro. J Mol Histol 2008; 39:371-9. [DOI: 10.1007/s10735-008-9175-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Accepted: 05/27/2008] [Indexed: 11/24/2022]
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Masutani T, Taguchi K, Kumanogoh H, Nakamura S, Maekawa S. Molecular interaction of neurocalcin alpha with alsin (ALS2). Neurosci Lett 2008; 438:26-8. [PMID: 18482800 DOI: 10.1016/j.neulet.2008.04.066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Revised: 04/07/2008] [Accepted: 04/14/2008] [Indexed: 12/11/2022]
Abstract
Membrane microdomains (MDs), or lipid rafts, are recently identified dynamic membrane domains on which various signal-transductions are performed. Intracellular Ca(2+)-binding proteins participate in the Ca(2+) signaling through interaction with various proteins. Neurocalcin alpha (NCalpha) is a member of neuronal calcium sensor (NCS) protein family and shows Ca(2+)-dependent binding to the cell membrane through N-terminal myristoyl moiety. Since NCalpha was identified as a Ca(2+)-dependent binding protein to neuronal MDs, its binding proteins may participate in the signal-transduction on the MDs. In an immunoprecipitate using anti-NCalpha antibody, alsin (ALS2), a protein product of one of the responsive genes for amyotrophic lateral sclerosis, was detected through LC-MS/MS. Specific antibody to alsin was produced and immunoprecipitation using this antibody showed co-sedimentation of NCalpha. Some part of alsin bound to brain-derived MD fraction in the presence of Ca(2+) ions and eluted out by the chelation of Ca(2+) ions, as in the case of NCalpha. Immunostaining of cultured neurons showed broad distribution of alsin and NCalpha, and membrane association of these proteins were increased through Ca(2+) loading by maitotoxin. These results suggest that alsin binds cell membrane in a Ca(2+)-dependent manner through NCalpha and regulates membrane dynamics.
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Affiliation(s)
- Toshinori Masutani
- Division of Biology, Graduate School of Science, Kobe-University, Rokkodaicho 1-1, Nada-ku, Kobe 657-8501, Japan
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Yamazaki Y, Horibata Y, Nagatsuka Y, Hirabayashi Y, Hashikawa T. Fucoganglioside alpha-fucosyl(alpha-galactosyl)-GM1: a novel member of lipid membrane microdomain components involved in PC12 cell neuritogenesis. Biochem J 2007; 407:31-40. [PMID: 17608628 PMCID: PMC2267403 DOI: 10.1042/bj20070090] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In order to search for novel components of lipid membrane microdomains involved in neural signalling pathways, mAbs (monoclonal antibodies) were raised against the detergent-insoluble membrane fraction of PC12 (pheochromocytoma) cells. Among the 22 hybrid clones, mAb PR#1 specifically detected a fucoganglioside Fuc(Gal)-GM1 [a-fucosyl(a-galactosyl)-GM1], a ganglioside homologous with GM1a (II3NeuAc,GgOse4Cer), as a novel member of microdomain components with biological functions. In the presence of mAb PR#1 in the culture medium, the outgrowth of neurites was induced in PC12 cells in a dose-dependent manner, with no effects on cell proliferation, suggesting that Fuc(Gal)-GM1 is preferentially involved in PC12 cell neuritogenesis. Effects through Fuc(Gal)-GM1 were different from those through GM1a during differentiation, e.g. under PR#1 treatment on Fuc(Gal)-GM1, round cell bodies with thinner cell processes were induced, whereas treatment with CTB (cholera toxin B subunit), a specific probe for GM1a, produced flattened cell bodies with thicker pro-cesses. Molecular analysis demonstrated that the PR#1-Fuc(Gal)-GM1 pathway was associated with Fyn and Yes of the Src family of kinases, although Src itself was not involved. No association was found with TrkA (tropomyosin receptor kinase A) and ERKs (extracellular-signal-regulated kinases), which are responsible for GM1a-induced differentiation. From these findings, it is suggested that a fucoganglioside Fuc(Gal)-GM1 provides a functional platform distinct from that of GM1a for signal transduction in PC12 cell differentiation.
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Affiliation(s)
- Yasuhiro Yamazaki
- *Laboratory for Neural Architecture, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan
| | - Yasuhiro Horibata
- †Hirabayashi Research Unit, Neural Circuit Research Group, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan
| | - Yasuko Nagatsuka
- †Hirabayashi Research Unit, Neural Circuit Research Group, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan
| | - Yoshio Hirabayashi
- †Hirabayashi Research Unit, Neural Circuit Research Group, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan
| | - Tsutomu Hashikawa
- *Laboratory for Neural Architecture, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan
- To whom correspondence should be addressed (email )
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Levitan I, Gooch KJ. Lipid rafts in membrane-cytoskeleton interactions and control of cellular biomechanics: actions of oxLDL. Antioxid Redox Signal 2007; 9:1519-34. [PMID: 17576163 DOI: 10.1089/ars.2007.1686] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Membrane-cytoskeleton coupling is known to play major roles in a plethora of cellular responses, such as cell growth, differentiation, polarization, motility, and others. In this review, the authors discuss the growing amount of evidence indicating that membrane-cytoskeleton interactions are regulated by the lipid composition of the plasma membrane, suggesting that cholesterol-rich membrane domains (lipid rafts), including caveolae, are essential for membrane-cytoskeleton coupling. Several models for raft-cytoskeleton interactions are discussed. Also described is the evidence suggesting that raft-cytoskeleton interactions play key roles in several cytoskeleton-dependent processes, particularly in the regulation of cellular biomechanical properties. To address further the physiological significance of raft-cytoskeleton coupling, the authors focus on the impact of oxidized low density lipoproteins, one of the major cholesterol carriers and proatherogenic factors, on the integrity of lipid rafts/caveolae, and on the organization of the cytoskeleton. Finally, the authors review the recent studies showing that oxLDL and cholesterol depletion have similar impacts on the biomechanical properties of vascular endothelial cells, which in turn affect endothelial angiogenic potential.
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Affiliation(s)
- Irena Levitan
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Takemoto-Kimura S, Ageta-Ishihara N, Nonaka M, Adachi-Morishima A, Mano T, Okamura M, Fujii H, Fuse T, Hoshino M, Suzuki S, Kojima M, Mishina M, Okuno H, Bito H. Regulation of dendritogenesis via a lipid-raft-associated Ca2+/calmodulin-dependent protein kinase CLICK-III/CaMKIgamma. Neuron 2007; 54:755-70. [PMID: 17553424 DOI: 10.1016/j.neuron.2007.05.021] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 12/30/2006] [Accepted: 05/16/2007] [Indexed: 02/07/2023]
Abstract
Ca(2+) signaling plays a central role in activity-dependent regulation of dendritic arborization, but key molecular mechanisms downstream of calcium elevation remain poorly understood. Here we show that the C-terminal region of the Ca(2+)/calmodulin-dependent protein kinase CLICK-III (CL3)/CaMKIgamma, a membrane-anchored CaMK, was uniquely modified by two sequential lipidification steps: prenylation followed by a kinase-activity-regulated palmitoylation. These modifications were essential for CL3 membrane anchoring and targeting into detergent-resistant lipid microdomains (or rafts) in the dendrites. We found that CL3 critically contributed to BDNF-stimulated dendritic growth. Raft insertion of CL3 specifically promoted dendritogenesis of cortical neurons by acting upstream of RacGEF STEF and Rac, both present in lipid rafts. Thus, CL3 may represent a key element in the Ca(2+)-dependent and lipid-raft-delineated switch that turns on extrinsic activity-regulated dendrite formation in developing cortical neurons.
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Affiliation(s)
- Sayaka Takemoto-Kimura
- Department of Neurochemistry, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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Taguchi K, Yoshinaka K, Yoshino KI, Yonezawa K, Maekawa S. Biochemical and morphologic evidence of the interaction of oligodendrocyte membrane rafts with actin filaments. J Neurosci Res 2005; 81:218-25. [PMID: 15931670 DOI: 10.1002/jnr.20555] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cytoskeletal structures under the cell membrane carry out pivotal roles in the maintenance and remodeling of the cell structures. Reforming of the cytoskeletal networks after partial extraction of membrane components could be a good clue to identify molecular components pertaining the interaction of cytoskeleton with membrane. A detergent extract from 3-week-old rat brain membrane fraction was found to make an actin-based gel upon incubation at 25 degrees C. Some protein components of the gelation products were recovered in a Triton-insoluble low-density microdomain fraction (raft) after depolymerization of actin filaments. Some of these proteins were identified as 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNPase), proteolipid protein (PLP), and myelin oligodendrocyte glycoprotein (MOG) through electrospray time-of-flight (ESI-TOF) analysis and Western blotting. Because these proteins are well-known marker proteins of oligodendrocytes, localization of these proteins and cholesterol, a raft-localized lipid, with actin filaments was studied using cultured oligodendrocytes. Clear colocalization of these proteins and cholesterol with actin filaments was observed after Triton treatment at 4 degrees C before fixation. These results indicate that raft microdomains participate in the formation of cell shape through interaction with microfilaments in oligodendrocytes.
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Affiliation(s)
- Katsutoshi Taguchi
- Division of Bioinformation, Department of Biosystems Science, Graduate School of Science and Technology, Kobe University, Nada-ku, Kobe, Japan
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Désiré L, Bourdin J, Loiseau N, Peillon H, Picard V, De Oliveira C, Bachelot F, Leblond B, Taverne T, Beausoleil E, Lacombe S, Drouin D, Schweighoffer F. RAC1 inhibition targets amyloid precursor protein processing by gamma-secretase and decreases Abeta production in vitro and in vivo. J Biol Chem 2005; 280:37516-25. [PMID: 16150730 DOI: 10.1074/jbc.m507913200] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
beta-Amyloid peptides (Abeta) that form the senile plaques of Alzheimer disease consist mainly of 40- and 42-amino acid (Abeta 40 and Abeta 42) peptides generated from the cleavage of the amyloid precursor protein (APP). Generation of Abeta involves beta-secretase and gamma-secretase activities and is regulated by membrane trafficking of the proteins involved in Abeta production. Here we describe a new small molecule, EHT 1864, which blocks the Rac1 signaling pathways. In vitro, EHT 1864 blocks Abeta 40 and Abeta 42 production but does not impact sAPPalpha levels and does not inhibit beta-secretase. Rather, EHT 1864 modulates APP processing at the level of gamma-secretase to prevent Abeta 40 and Abeta 42 generation. This effect does not result from a direct inhibition of the gamma-secretase activity and is specific for APP cleavage, since EHT 1864 does not affect Notch cleavage. In vivo, EHT 1864 significantly reduces Abeta 40 and Abeta 42 levels in guinea pig brains at a threshold that is compatible with delaying plaque accumulation and/or clearing the existing plaque in brain. EHT 1864 is the first derivative of a new chemical series that consists of candidates for inhibiting Abeta formation in the brain of AD patients. Our findings represent the first pharmacological validation of Rac1 signaling as a target for developing novel therapies for Alzheimer disease.
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20
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Grande-García A, Echarri A, Del Pozo MA. Integrin regulation of membrane domain trafficking and Rac targeting. Biochem Soc Trans 2005; 33:609-13. [PMID: 16042555 DOI: 10.1042/bst0330609] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Integrins are crucial regulators of essential cellular processes such as gene expression, cell proliferation and migration. Alteration of these processes is central to tumourigenesis. Integrin signals mediate anchorage dependence of cell growth, while growth of cancer cells is anchorage-independent. Integrins critically regulate Rho family GTPases, that are also involved in cell-cycle progression and oncogenesis. In addition to their effect on GTP loading, integrins independently control the translocation of GTP-bound Rac to the plasma membrane. This step is essential for Rac binding to effectors. Integrins increase membrane affinity for Rac, leading to RhoGDI dissociation and effector coupling locally, in the vicinity of activated/bound integrins. Integrin-regulated Rac binding sites are within CEMMs (cholesterol-enriched membrane microdomains). Integrins control Rac signalling by preventing the internalization of its binding sites in CEMMs. Integrin regulation of signalling pathways initiated in CEMMs may be important for the spatial control of cell migration and anchorage dependence of cell growth.
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Affiliation(s)
- A Grande-García
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Ronda de Poniente, 5, 28760 Tres Cantos, Madrid, Spain
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21
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Zimmerman MC, Dunlay RP, Lazartigues E, Zhang Y, Sharma RV, Engelhardt JF, Davisson RL. Requirement for Rac1-dependent NADPH oxidase in the cardiovascular and dipsogenic actions of angiotensin II in the brain. Circ Res 2004; 95:532-9. [PMID: 15271858 DOI: 10.1161/01.res.0000139957.22530.b9] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We have shown that intracellular superoxide (O(2)(*-)) production in CNS neurons plays a key role in the pressor, bradycardic, and dipsogenic actions of Ang II in the brain. In this study, we tested the hypothesis that a Rac1-dependent NADPH oxidase is a key source of O(2)(*-) in Ang II-sensitive neurons and is involved in these central Ang II-dependent effects. We performed both in vitro and in vivo studies using adenoviral (Ad)-mediated expression of dominant-negative Rac1 (AdN17Rac1) to inhibit Ang II-stimulated Rac1 activation, an obligatory step in NADPH oxidase activation. Ang II induced a time-dependent increase in Rac1 activation and O(2)(*-) production in Neuro-2A cells, and this was abolished by pretreatment with AdN17Rac1 or the NADPH oxidase inhibitors apocynin or diphenylene iodonium. AdN17Rac1 also inhibited Ang II-induced increases in NADPH oxidase activity in primary neurons cultured from central cardiovascular control regions. In contrast, overexpression of wild-type Rac1 (AdwtRac1) caused more robust NADPH oxidase-dependent O(2)(*-) production to Ang II. To extend the in vitro studies, the pressor, bradycardic, and drinking responses to intracerebroventricularly (ICV) injected Ang II were measured in mice that had undergone gene transfer of AdN17Rac1 or AdwtRac1 to the brain. AdN17Rac1 abolished the increase in blood pressure, decrease in heart rate, and drinking response induced by ICV injection of Ang II, whereas AdwtRac1 enhanced these physiological effects. The exaggerated physiological responses in AdwtRac1-treated mice were abolished by O(2)(*-) scavenging. These results, for the first time, identify a Rac1-dependent NADPH oxidase as the source of central Ang II-induced O(2)(*-) production, and implicate this oxidase in cardiovascular diseases associated with dysregulation of brain Ang II signaling, including hypertension.
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Affiliation(s)
- Matthew C Zimmerman
- Department of Anatomy and Cell Biology, The University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City 52242, USA
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22
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O'Kane EM, Stone TW, Morris BJ. Increased long-term potentiation in the CA1 region of rat hippocampus via modulation of GTPase signalling or inhibition of Rho kinase. Neuropharmacology 2004; 46:879-87. [PMID: 15033347 DOI: 10.1016/j.neuropharm.2003.11.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2003] [Revised: 11/10/2003] [Accepted: 11/20/2003] [Indexed: 11/20/2022]
Abstract
There is accumulating evidence that Ras, and Ras-related GTPases of the Rho family, such as RhoA, RhoB and Rac1, are involved in synaptic plasticity in brain regions such as the hippocampus. We have recently shown that Rho family GTPases are activated by synaptic transmission in the CA1 region of the hippocampus. Since the function of these GTPases is dependent on post-translational isoprenylation by either farnesyl or geranylgeranyl transferases, we tested the hypothesis that inhibition of isoprenylation would modify long-term potentiation (LTP). Farnesyl transferase inhibition, which suppressed activation of RhoB and Ras but not RhoA or Rac1, reduced the magnitude of LTP, while geranylgeranyl transferase inhibition, which inhibited RhoA and Rac1 but not RhoB, increased the magnitude of LTP. In addition, Y-27632, a specific inhibitor of a downstream effector of Rho GTPases-Rho-kinase-also increased the magnitude of LTP. This provides strong evidence that GTPases are important mediators of synaptic plasticity, and demonstrates that Rho-kinase acts to reduce the degree of plasticity at hippocampal synapses during LTP. Rho-kinase inhibitors have the unusual property of increasing the magnitude of LTP, and so may be potential cognitive enhancers.
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Affiliation(s)
- E M O'Kane
- Institute of Biomedical and Life Sciences, Division of Neuroscience and Biomedical Systems, West Medical Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
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23
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Stickney JT, Bacon WC, Rojas M, Ratner N, Ip W. Activation of the tumor suppressor merlin modulates its interaction with lipid rafts. Cancer Res 2004; 64:2717-24. [PMID: 15087385 DOI: 10.1158/0008-5472.can-03-3798] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neurofibromatosis type 2 (NF2) is a genetic disorder characterized by bilateral schwannomas of the eighth cranial nerve. The NF2 tumor suppressor protein, merlin, is related to the ERM (ezrin, radixin, and moesin) family of membrane/F-actin linkers. Merlin resists solubilization by the detergent Triton X-100 (TX-100), a property commonly attributed to association with the cytoskeleton. Accordingly, NF2 patient mutations that encode merlins with enhanced TX-100 solubility have been explained previously in terms of loss of cytoskeletal attachment. However, here we present data to suggest that the detergent resistance of merlin is a result of its constitutive residence in lipid rafts. Furthermore, when cells are grown to high density, merlin shifts to a more buoyant lipid raft fraction in a density gradient. This shift is mimicked in subconfluent cells treated with cytochalasin D, suggesting that the shift results from merlin dissociation from the actin cytoskeleton, but not from lipid rafts. Intramolecular NH(2)- and COOH-terminal binding, which occurs when merlin transitions to the growth-suppressive form, also brings about a similar change in buoyant density. Our results suggest that constitutive residence of merlin in lipid rafts is crucial for its function and that as merlin becomes growth suppressive in vivo, one significant molecular event may be the loss of interaction with the actin cytoskeleton. To our knowledge, merlin is the first tumor suppressor known to reside within lipid rafts, and the significance of this finding is underscored by known loss-of-function NF2 patient mutations that encode merlins with enhanced TX-100 solubility.
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Affiliation(s)
- John T Stickney
- Department of Cell Biology, Neurobiology, and Anatomy, Vontz Center for Molecular Studies, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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24
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Zimmerman MC, Davisson RL. Redox signaling in central neural regulation of cardiovascular function. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2004; 84:125-49. [PMID: 14769433 DOI: 10.1016/j.pbiomolbio.2003.11.009] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
One of the most prominent concepts to emerge in cardiovascular research over the past decade, especially in areas focused on angiotensin II (AngII), is that reactive oxygen species (ROS) are critical signaling molecules in a wide range of cellular processes. Many of the physiological effects of AngII are mediated by ROS, and alterations in AngII-mediated redox mechanisms are implicated in cardiovascular diseases such as hypertension and atherosclerosis. Although most investigations to date have focused on the vasculature as a key player, the nervous system has recently begun to gain attention in this field. Accumulating evidence suggests that ROS have important effects on central neural mechanisms involved in blood pressure regulation, volume homeostasis, and autonomic function, particularly those that involve AngII signaling. Furthermore, oxidant stress in the central nervous system is implicated in the neuro-dysregulation associated with some forms of hypertension and heart failure. The main objective of this review is to discuss the recent progress and prospects for this new field of central redox signaling in cardiovascular regulation, while also addressing the molecular tools that have spurred it forward.
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Affiliation(s)
- Matthew C Zimmerman
- Department of Anatomy and Cell Biology, Roy J and Lucille A Carver College of Medicine, The University of Iowa, Iowa City 52245, USA
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25
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del Pozo MA, Alderson NB, Kiosses WB, Chiang HH, Anderson RGW, Schwartz MA. Integrins regulate Rac targeting by internalization of membrane domains. Science 2004; 303:839-42. [PMID: 14764880 DOI: 10.1126/science.1092571] [Citation(s) in RCA: 431] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Translocation of the small GTP-binding protein Rac1 to the cell plasma membrane is essential for activating downstream effectors and requires integrin-mediated adhesion of cells to extracellular matrix. We report that active Rac1 binds preferentially to low-density, cholesterol-rich membranes, and specificity is determined at least in part by membrane lipids. Cell detachment triggered internalization of plasma membrane cholesterol and lipid raft markers. Preventing internalization maintained Rac1 membrane targeting and effector activation in nonadherent cells. Regulation of lipid rafts by integrin signals may regulate the location of membrane domains such as lipid rafts and thereby control domain-specific signaling events in anchorage-dependent cells.
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Affiliation(s)
- Miguel A del Pozo
- Department of Cell Biology, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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26
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Vilhardt F, van Deurs B. The phagocyte NADPH oxidase depends on cholesterol-enriched membrane microdomains for assembly. EMBO J 2004; 23:739-48. [PMID: 14765128 PMCID: PMC380990 DOI: 10.1038/sj.emboj.7600066] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2003] [Accepted: 12/12/2003] [Indexed: 11/09/2022] Open
Abstract
The superoxide-producing phagocyte NADPH oxidase consists of a membrane-bound flavocytochrome b558 complex, and cytosolic factors p47phox, p67phox and the small GTPase Rac, which translocate to the membrane to assemble the active complex following cell activation. We here show that insolubility of NADPH oxidase subunits in nonionic detergents TX-100, Brij-58, and Brij-98 is a consequence of inclusion into cholesterol-enriched membrane microdomains (lipid rafts). Thus, flavocytochrome b558, in a cholesterol-dependent manner, segregated to the bouyant low-density detergent-resistant membrane (DRM) fraction, and the cytosolic NADPH oxidase factors associated dynamically with low-density DRM. Further, superoxide production following cholesterol depletion was severely compromised in intact cells or in a cell-free reconstituted system, correlating with a reduced translocation of cytosolic phox subunits to the membrane. In analogy with the widely accepted role of lipid rafts as signaling platforms, our data indicate that cholesterol-enriched microdomains act to recruit and/or organize the cytosolic NADPH oxidase factors in the assembly of the active NADPH oxidase.
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Affiliation(s)
- Frederik Vilhardt
- Structural Cell Biology Unit, Department of Medical Anatomy, The Panum Institute, Copenhagen, Denmark.
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27
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Deretic D, Traverso V, Parkins N, Jackson F, Rodriguez de Turco EB, Ransom N. Phosphoinositides, ezrin/moesin, and rac1 regulate fusion of rhodopsin transport carriers in retinal photoreceptors. Mol Biol Cell 2004; 15:359-70. [PMID: 13679519 PMCID: PMC307553 DOI: 10.1091/mbc.e03-04-0203] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2003] [Revised: 08/25/2003] [Accepted: 08/26/2003] [Indexed: 11/11/2022] Open
Abstract
The post-Golgi trafficking of rhodopsin in photoreceptor cells is mediated by rhodopsin-bearing transport carriers (RTCs) and regulated by the small GTPase rab8. In this work, we took a combined pharmacological-proteomic approach to uncover new regulators of RTC trafficking toward the specialized light-sensitive organelle, the rod outer segment (ROS). We perturbed phospholipid synthesis by activating phospholipase D with sphingosine 1-phosphate (S1P) or inhibiting phosphatidic acid phosphohydrolase by propranolol (Ppl). S1P stimulated the overall rate of membrane trafficking toward the ROS. Ppl stimulated budding of RTCs, but blocked membrane delivery to the ROS. Ppl caused accumulation of RTCs in the vicinity of the fusion sites, suggesting a defect in tethering, similar to the previously described phenotype of the rab8T22N mutant. Proteomic analysis of RTCs accumulated upon Ppl treatment showed a significant decrease in phosphatidylinositol-4,5-bisphosphate-binding proteins ezrin and/or moesin. Ppl induced redistribution of moesin, actin and the small GTPase rac1 from RTCs into the cytosol. By confocal microscopy, ezrin/moesin and rac1 colocalized with rab8 on RTCs at the sites of their fusion with the plasma membrane; however, this distribution was lost upon Ppl treatment. Our data suggest that in photoreceptors phosphatidylinositol-4,5-bisphosphate, moesin, actin, and rac1 act in concert with rab8 to regulate tethering and fusion of RTCs. Consequentially, they are necessary for rhodopsin-laden membrane delivery to the ROS, thus controlling the critical steps in the biogenesis of the light-detecting organelle.
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Affiliation(s)
- Dusanka Deretic
- Department of Surgery, Division of Ophthalmology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
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28
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Abstract
Ras-related GTPases of the Rho family, such as RhoA and RhoB, are well-characterised mediators of morphological change in peripheral tissues via their effects on the actin cytoskeleton. We tested the hypothesis that Rho family GTPases are involved in synaptic transmission in the CA1 region of the hippocampus. We show that GTPases are activated by synaptic transmission. RhoA and RhoB were activated by low frequency stimulation, while the induction of long-term potentiation (LTP) by high frequency stimulation was associated with specific activation of RhoB via NMDA receptor stimulation. This illustrates that these GTPases are potential mediators of synaptic transmission in the hippocampus, and raises the possibility that RhoB may play a role in plasticity at hippocampal synapses during LTP.
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Affiliation(s)
- E M O'Kane
- Division of Neuroscience and Biomedical Systems, Institute of Biomedical and Life Sciences, West Medical Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
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29
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Abstract
Small GTP binding proteins regulate diverse biological processes including gene expression, cytoskeleton reorganization, and protein and vesicular transport. While small GTPases have been investigated in a wide variety of cells, few studies have addressed their role in photoreceptors. In vertebrate retinal rods, the light stimulus is transmitted from rhodopsin via the pathway mediated by the heterotrimeric G protein transducin. To increase their sensitivity to light, photoreceptors accumulate remarkably high concentrations of rhodopsin and transducin in specialized cellular compartments, the outer segments (OS). Transport of these proteins from the inner segments is regulated by the small GTPases Rab6 and Rab8, which do not enter OS. Here, we asked if small G proteins have other functions in photoreceptors. We show that OS contain the small GTPase Rac-1, a member of the Rho family. In contrast to other cells, Rac-1 in OS is exclusively associated with the membranes and resides in lipid rafts. Most importantly, Rac-1 is activated by light. This activation is specifically blocked by a synthetic peptide corresponding to the Asn-Pro-X-X-Tyr motif found in rhodopsin, and Rac-1 coprecipitates with rhodopsin on Concanavalin A Sepharose. These data provide the first direct evidence for the existence of a novel pathway activated by rhodopsin.
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Affiliation(s)
- Nagaraj Balasubramanian
- Department of Molecular and Cellular Pharmacology and the Neuroscience Program, University of Miami School of Medicine, Miami, FL 33136, USA
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30
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Rosslenbroich V, Dai L, Franken S, Gehrke M, Junghans U, Gieselmann V, Kappler J. Subcellular localization of collapsin response mediator proteins to lipid rafts. Biochem Biophys Res Commun 2003; 305:392-9. [PMID: 12745088 DOI: 10.1016/s0006-291x(03)00754-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Collapsin response mediator proteins (CRMPs) are involved in signal transduction after exposure of neural cells to the axon guidance molecule Semaphorin 3A/collapsin. All five known CRMPs are expressed in the developing cerebral cortex and neocortical neurons are responsive to Semaphorin 3A. Here, we examine the expression and subcellular localization of CRMPs in neocortical neurons and in neonatal rat brain. In neocortical neurons CRMP-4 was detected in the perikaryon with a diffuse cytosolic distribution. In neurites and at growth cones punctate staining patterns were observed. Extraction of neuron cultures with methyl-beta-cyclodextrin to deplete cholesterol caused rapid redistribution of the punctate CRMP-4 staining into larger patches and abundant growth cone collapse. Western blotting of brain extracts demonstrated for all CRMPs the existence of soluble, detergent-extractable, and Triton X-100-resistant forms. Furthermore, sucrose density gradient centrifugation after solubilization of brain membranes with Triton X-100 revealed that CRMP-1, -3, -5, and to a lower extent CRMP-4 are associated with a detergent-resistant fraction with low buoyant density, but CRMP-2 was not detectable in this fraction. Thus, we propose that lipid rafts form sites for the compartmentalization of signaling events involving specific CRMPs and that the integrity of these membrane microdomains is essential for the maintenance of growth cones.
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Affiliation(s)
- Volker Rosslenbroich
- Institut für Physiologische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 11, 53115, Bonn, Germany
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31
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Zhang SSM, Wei JY, Li C, Barnstable CJ, Fu XY. Expression and activation of STAT proteins during mouse retina development. Exp Eye Res 2003; 76:421-31. [PMID: 12634107 DOI: 10.1016/s0014-4835(03)00002-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cytokines and growth factors play important roles in mammalian ocular development and maintenance. Recent studies have indicated that some of these ligands can activate signal transducer and activator of transcription factors (STATs) and modulate gene transcription. The purpose of this study was to investigate the expression and activation of STAT proteins in the developing mouse retina. Anti-STAT and anti-phosphorylated STAT antibodies were used to detect the expression and activation of STATs in embryonic and postnatal neuronal retina, ciliary margin, and retinal pigment epithelium (RPE). In situ hybridization and Western blot were also employed. In embryonic stages, all STAT proteins were expressed in the neuronal retina in distinct cell populations at different embryonic stages. For example, Stat3 expression and activation gradually increased in the inner neuroblast layer and ciliary margin during development. In adult retina, Stat3 was detected in the inner nuclear layer and ganglion cells layers. Stat1 was strongly expressed in both outer and inner plexiform layers. Stat5a was clearly expressed in the outer/inner nuclear layer, the ganglion cell layer, and the inner plexiform layer. Strong expression of Stat3, Stat5a, and Stat6 was observed in the RPE. Activated Stat3 and Stat5a were found in the neural retina and the RPE. Distinct STAT proteins were present in different cell populations in neuronal retina and RPE suggesting multiple functions of STATs in mammalian eye development. Studies of STAT signal pathways in the eye may contribute to the understanding of molecular mechanisms in control of ocular development and pathogenesis.
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Affiliation(s)
- Samuel Shao-Min Zhang
- Department of Pathology, Yale University School of Medicine, 310 Cedar Street, BML 117, New Haven, CT 06520-8023, USA.
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32
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Maekawa S, Iino S, Miyata S. Molecular characterization of the detergent-insoluble cholesterol-rich membrane microdomain (raft) of the central nervous system. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1610:261-70. [PMID: 12648779 DOI: 10.1016/s0005-2736(03)00023-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Many fundamental neurological issues such as neuronal polarity, the formation and remodeling of synapses, synaptic transmission, and the pathogenesis of the neuronal cell death are closely related to the membrane dynamics. The elucidation of functional roles of a detergent-insoluble cholesterol-rich domain (raft) could therefore provide good clues to the molecular understanding of these important phenomena, for the participation of the raft in the fundamental cell functions, such as signal transduction and selective transport of lipids and proteins, has been elucidated in nonneural cells. Interestingly, the brain is rich in raft and the brain-derived raft differs in its lipid and protein components from other tissue-derived rafts. Since many excellent reviews are written on the membrane lipid dynamics of this microdomain, signal transduction, and neuronal glycolipids, we review on the characterization of the raft proteins recovered in the detergent-insoluble low-density fraction from rat brain. Special focus is addressed on the biochemical characterization of a neuronal enriched protein, NAP-22, for the lipid organizing activity of this protein has become increasingly clear.
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Affiliation(s)
- Shohei Maekawa
- Department of Life Science, Graduate School of Science and Technology, Kobe University, Rokkodai 1-1, Kobe 657-8501, Japan.
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33
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Noyama K, Maekawa S. Localization of cyclic nucleotide phosphodiesterase 2 in the brain-derived Triton-insoluble low-density fraction (raft). Neurosci Res 2003; 45:141-8. [PMID: 12573460 DOI: 10.1016/s0168-0102(02)00208-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cyclic nucleotides perform a variety of roles in the formation and remodeling of the neuronal interaction. The membrane microdomain called "raft" has been paid much attention, for this domain contains many signal-transducing molecules including trimeric G proteins and cytoskeletal proteins. The raft domain is recovered in a low-density fraction after the treatment of the membrane with a non-ionic detergent such as Triton X-100. The enrichment of cholesterol and sphingolipids is ascribed to be responsible for the detergent insolubility. In this study we focused on the cyclic nucleotide signaling process in rafts prepared from the cerebral cortex of 10-day-old rat and the synaptic plasma membrane fraction and found the presence of a high cAMP and cGMP phosphodiesterase (PDE) activity. The activity was effectively inhibited with erythro-9-(2-hydroxy-3-nonyl)adenine, a PDE2-specific inhibitor but not with other inhibitors such as vinpocetine, quazione, or zaprinast. Further western blotting analysis confirmed the localization of PDE2 in the raft fraction. The presence of adenylyl cyclase V/VI and PKA in the raft fraction was also shown with Western blotting. These results suggest the participation of the raft in the cyclic nucleotide signaling cascade in neurons.
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Affiliation(s)
- Kenjiro Noyama
- Division of Bioinformation, Department of Life Science, Graduate School of Science and Technology, Kobe University, Rokkodai 1-1, Nada-ku, Kobe 657-8501, Japan
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34
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Nakai Y, Kamiguchi H. Migration of nerve growth cones requires detergent-resistant membranes in a spatially defined and substrate-dependent manner. J Cell Biol 2002; 159:1097-108. [PMID: 12499360 PMCID: PMC2173975 DOI: 10.1083/jcb.200209077] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Motility of nerve growth cones (GCs) is regulated by region-specific activities of cell adhesion molecules (CAMs). CAM activities could be modified by their localization to detergent-resistant membranes (DRMs), specialized microdomains enriched in signaling molecules. This paper deals with a question of whether DRMs are involved in GC migration stimulated by three CAMs; L1, N-cadherin (Ncad), and beta1 integrin. We demonstrate that L1 and Ncad are present in DRMs, whereas beta1 integrin is exclusively detected in non-DRMs of neurons and that localization of L1 and Ncad to DRMs is developmentally regulated. GC migration mediated by L1 and Ncad but not by beta1 integrin is inhibited after DRM disruption by micro-scale chromophore-assisted laser inactivation (micro-CALI) of GM1 gangliosides or by pharmacological treatments that deplete cellular cholesterol or sphingolipids, essential components for DRMs. Characteristic morphology of GCs induced by L1 and Ncad is also affected by micro-CALI-mediated DRM disruption. Micro-CALI within the peripheral domain of GCs, or even within smaller areas such as the filopodia and the lamellipodia, is sufficient to impair their migration. However, micro-CALI within the central domain does not affect GC migration. These results demonstrate the region-specific involvement of DRMs in CAM-dependent GC behavior.
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Affiliation(s)
- Yoko Nakai
- Developmental Brain Science Group, RIKEN Brain Science Institute (BSI), Wako, Saitama, 351-0198, Japan
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35
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Terashita A, Funatsu N, Umeda M, Shimada Y, Ohno-Iwashita Y, Epand RM, Maekawa S. Lipid binding activity of a neuron-specific protein NAP-22 studied in vivo and in vitro. J Neurosci Res 2002; 70:172-9. [PMID: 12271466 DOI: 10.1002/jnr.10407] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
There exists a microdomain called "raft" in the cell membrane. The enrichment of cholesterol and sphingolipids in its outer leaflet is well recognized. In contrast, little is known of the lipid composition of the inner leaflet of raft, where many acylated signal-transducing molecules, such as trimeric G proteins and protein tyrosine kinases, associate. NAP-22 is a neuronal protein localized on the inner leaflet of raft domain. This protein was found to bind cholesterol in the liposome. In this study, we further analyze the lipid binding activity of NAP-22 using eukaryotic and bacterial expression systems. In addition to cholesterol, NAP-22 showed a phosphatidylethanolamine (PE)- and polyphosphoinositide-dependent membrane binding in the liposome assay. The N-terminal myristoylation was essential for the liposome binding. The C-terminal deletion up to D61 showed little effect on the binding. The lipid binding region was hence judged to be in the N-terminal 60-amino-acid sequence. NAP-22 was then expressed in COS7 cells, and the intracellular localization was studied. Biochemical analysis showed the localization of NAP-22 in a Triton-insoluble low-density fraction. Cell staining analysis showed colocalization patterns of NAP-22 with PE and cholesterol in the membrane.
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Affiliation(s)
- Akira Terashita
- Division of Bioinformation, Department of Life Science, Graduate School of Science and Technology, Kobe-University, Rokkodai, Nada-ku, Kobe, Japan
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Grimmer S, van Deurs B, Sandvig K. Membrane ruffling and macropinocytosis in A431 cells require cholesterol. J Cell Sci 2002; 115:2953-62. [PMID: 12082155 DOI: 10.1242/jcs.115.14.2953] [Citation(s) in RCA: 184] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cholesterol is important for the formation of caveolea and deeply invaginated clathrin-coated pits. We have now investigated whether formation of macropinosomes is dependent on the presence of cholesterol in the plasma membrane. Macropinocytosis in A431 cells was induced by the phorbol ester 12-O-tetradecanoylphorbol 13-acetate, a potent activator of protein kinase C (PKC). When cells were pretreated with methyl-β-cyclodextrin to extract cholesterol, the phorbol ester was unable to induce the increased endocytosis of ricin otherwise seen, although PKC could still be activated. Electron microscopy revealed that extraction of cholesterol inhibited the formation of membrane ruffles and macropinosomes at the plasma membrane. Furthermore, cholesterol depletion inhibited the phorbol ester-induced reorganization of filamentous actin at the cell periphery, a prerequisite for the formation of membrane ruffles that close into macropinosomes. Under normal conditions the small GTPase Rac1 is activated by the phorbol ester and subsequently localized to the plasma membrane, where it induces the reorganization of actin filaments required for formation of membrane ruffles. Cholesterol depletion did not inhibit the activation of Rac1. However,confocal microscopy showed that extraction of cholesterol prevented the phorbol ester-stimulated localization of Rac1 to the plasma membrane. Thus,our results demonstrate that cholesterol is required for the membrane localization of activated Rac1, actin reorganization, membrane ruffling and macropinocytosis.
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Affiliation(s)
- Stine Grimmer
- Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
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