1
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Datta P, Cribbs JT, Seo S. Differential requirement of NPHP1 for compartmentalized protein localization during photoreceptor outer segment development and maintenance. PLoS One 2021; 16:e0246358. [PMID: 33961633 PMCID: PMC8104407 DOI: 10.1371/journal.pone.0246358] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 04/20/2021] [Indexed: 12/16/2022] Open
Abstract
Nephrocystin (NPHP1) is a ciliary transition zone protein and its ablation causes nephronophthisis (NPHP) with partially penetrant retinal dystrophy. However, the precise requirements of NPHP1 in photoreceptors are not well understood. Here, we characterize retinal degeneration in a mouse model of NPHP1 and show that NPHP1 is required to prevent infiltration of inner segment plasma membrane proteins into the outer segment during the photoreceptor maturation. We demonstrate that Nphp1 gene-trap mutant mice, which were previously described as null, are likely hypomorphs due to the production of a small quantity of functional mRNAs derived from nonsense-associated altered splicing and skipping of two exons including the one harboring the gene-trap. In homozygous mutant animals, inner segment plasma membrane proteins such as syntaxin-3 (STX3), synaptosomal-associated protein 25 (SNAP25), and interphotoreceptor matrix proteoglycan 2 (IMPG2) accumulate in the outer segment when outer segments are actively elongating. This phenotype, however, is spontaneously ameliorated after the outer segment elongation is completed. Consistent with this, some photoreceptor cell loss (~30%) occurs during the photoreceptor maturation period but it stops afterward. We further show that Nphp1 genetically interacts with Cep290, another NPHP gene, and that a reduction of Cep290 gene dose results in retinal degeneration that continues until adulthood in Nphp1 mutant mice. These findings demonstrate that NPHP1 is required for the confinement of inner segment plasma membrane proteins during the outer segment development, but its requirement diminishes as photoreceptors mature. Our study also suggests that additional mutations in other NPHP genes may influence the penetrance of retinopathy in human NPHP1 patients.
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Affiliation(s)
- Poppy Datta
- Department of Ophthalmology and Visual Sciences, The University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
- Institute for Vision Research, The University of Iowa, Iowa City, IA, United States of America
| | - J. Thomas Cribbs
- Department of Ophthalmology and Visual Sciences, The University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
- Institute for Vision Research, The University of Iowa, Iowa City, IA, United States of America
| | - Seongjin Seo
- Department of Ophthalmology and Visual Sciences, The University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
- Institute for Vision Research, The University of Iowa, Iowa City, IA, United States of America
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2
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Otani T, Nguyen TP, Tokuda S, Sugihara K, Sugawara T, Furuse K, Miura T, Ebnet K, Furuse M. Claudins and JAM-A coordinately regulate tight junction formation and epithelial polarity. J Cell Biol 2019; 218:3372-3396. [PMID: 31467165 PMCID: PMC6781433 DOI: 10.1083/jcb.201812157] [Citation(s) in RCA: 124] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 06/14/2019] [Accepted: 07/24/2019] [Indexed: 01/03/2023] Open
Abstract
Tight junctions (TJs) establish the epithelial barrier and are thought to form a membrane fence to regulate epithelial polarity, although the roles of TJs in epithelial polarity remain controversial. Claudins constitute TJ strands in conjunction with the cytoplasmic scaffolds ZO-1 and ZO-2 and play pivotal roles in epithelial barrier formation. However, how claudins and other TJ membrane proteins cooperate to organize TJs remains unclear. Here, we systematically knocked out TJ components by genome editing and show that while ZO-1/ZO-2-deficient cells lacked TJ structures and epithelial barriers, claudin-deficient cells lacked TJ strands and an electrolyte permeability barrier but formed membrane appositions and a macromolecule permeability barrier. Moreover, epithelial polarity was disorganized in ZO-1/ZO-2-deficient cells, but not in claudin-deficient cells. Simultaneous deletion of claudins and a TJ membrane protein JAM-A resulted in a loss of membrane appositions and a macromolecule permeability barrier and in sporadic epithelial polarity defects. These results demonstrate that claudins and JAM-A coordinately regulate TJ formation and epithelial polarity.
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Affiliation(s)
- Tetsuhisa Otani
- Division of Cell Structure, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Aichi, Japan
| | - Thanh Phuong Nguyen
- Division of Cell Structure, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Aichi, Japan
| | - Shinsaku Tokuda
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS
| | - Kei Sugihara
- Department of Anatomy and Cell Biology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Taichi Sugawara
- Division of Cell Structure, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Aichi, Japan
| | - Kyoko Furuse
- Division of Cell Structure, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Takashi Miura
- Department of Anatomy and Cell Biology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Klaus Ebnet
- Institute-Associated Research Group "Cell Adhesion and Cell Polarity," Institute of Medical Biochemistry, Zentrum für Molekularbiologie der Entzündung, University of Münster, Münster, Germany
| | - Mikio Furuse
- Division of Cell Structure, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Department of Physiological Sciences, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Aichi, Japan
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3
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Askvig JM, Watt JA. Absence of axonal sprouting following unilateral lesion in 125-day-old rat supraoptic nucleus may be due to age-dependent decrease in protein levels of ciliary neurotrophic factor receptor alpha. J Comp Neurol 2019; 527:2291-2301. [PMID: 30861131 DOI: 10.1002/cne.24675] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 02/28/2019] [Accepted: 03/04/2019] [Indexed: 02/04/2023]
Abstract
Within the supraoptic nucleus (SON) of a 35-day-old rat, we previously demonstrated a collateral sprouting response that reinnervates the partially denervated neural lobe (NL) after unilateral lesion of the hypothalamo-neurohypophysial tract. Others have shown a decreased propensity for axonal sprouting in an aged brain; therefore, to see if the SON exhibits a decreased propensity for axonal sprouting as the animal ages, we performed a unilateral lesion in the 125-day-old rat SON. Ultrastructural analysis of axon profiles in the NL of the 125-day-old rat demonstrated an absence of axonal sprouting following injury. We previously demonstrated that ciliary neurotrophic factor (CNTF) promotes process outgrowth from injured magnocellular neuron axons in vitro. Thus, we hypothesized that the lack of axonal sprouting in the 125-day-old rat SON may be due to a reduction in CNTF or the CNTF receptor components. To this point, we found that as the rat ages there is significantly less CNTF receptor alpha (CNTFRα) protein in the uninjured, 125-day-old rat compared to the uninjured, 35-day-old rat. We also observed that protein levels of CNTF and the CNTF receptor components were increased in the SON and NL following injury in the 35-day-old rat, but there was no difference in the protein levels in the 125-day-old rat. Altogether, the results presented herein demonstrate that the plasticity within the SON is highly dependent on the age of the rat, and that a decrease in CNTFRα protein levels in the 125-day-old rat may contribute to the loss of axonal sprouting following axotomy.
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Affiliation(s)
- Jason M Askvig
- Department of Biology, Concordia College, Moorhead, Minnesota
| | - John A Watt
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota
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4
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Wineland DM, Kelpsch DJ, Tootle TL. Multiple Pools of Nuclear Actin. Anat Rec (Hoboken) 2018; 301:2014-2036. [PMID: 30312534 PMCID: PMC6293971 DOI: 10.1002/ar.23964] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 04/14/2018] [Accepted: 04/17/2018] [Indexed: 02/06/2023]
Abstract
While nuclear actin was reported ~50 years ago, it's in vivo prevalence and structure remain largely unknown. Here, we use Drosophila oogenesis, that is, follicle development, to characterize nuclear actin. We find that three different reagents-DNase I, anti-actin C4, and anti-actin AC15-recognize distinct pools of nuclear actin. DNase I labels monomeric or G-actin, and, during follicle development, G-actin is present in the nucleus of every cell. Some G-actin is recognized by the C4 antibody. In particular, C4 nuclear actin colocalizes with DNase I to the nucleolus in anterior escort cells, follicle stem cells, some mitotic follicle cells, and a subset of nurse cells during early oogenesis. C4 also labels polymeric nuclear actin in the nucleoplasm of the germline stem cells, early cystoblasts, and oocytes. The AC15 antibody labels a completely distinct pool of nuclear actin from that of DNase I and C4. Specifically, AC15 nuclear actin localizes to the chromatin in the nurse and follicle cells during mid-to-late oogenesis. Within the oocyte, AC15 nuclear actin progresses from localizing to puncta surrounding the DNA, to forming a filamentous cage around the chromosomes. Together these findings reveal that nuclear actin is highly prevalent in vivo, and multiple pools of nuclear actin exist and can be recognized using different reagents. Additionally, our localization studies suggest that nuclear actin may regulate stemness, nucleolar structure and function, transcription, and nuclear structure. Such findings call for further studies to explore the prevalence, diversity, and functions of nuclear actin across tissues and organisms. Anat Rec, 301:2014-2036, 2018. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Dylane M. Wineland
- Anatomy and Cell Biology, University of Iowa Carver College of
Medicine, 51 Newton Rd, 1-500 BSB, Iowa City, IA 52242
| | - Daniel J. Kelpsch
- Anatomy and Cell Biology, University of Iowa Carver College of
Medicine, 51 Newton Rd, 1-500 BSB, Iowa City, IA 52242
| | - Tina L. Tootle
- Anatomy and Cell Biology, University of Iowa Carver College of
Medicine, 51 Newton Rd, 1-500 BSB, Iowa City, IA 52242
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5
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Skruber K, Read TA, Vitriol EA. Reconsidering an active role for G-actin in cytoskeletal regulation. J Cell Sci 2018; 131:131/1/jcs203760. [PMID: 29321224 DOI: 10.1242/jcs.203760] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Globular (G)-actin, the actin monomer, assembles into polarized filaments that form networks that can provide structural support, generate force and organize the cell. Many of these structures are highly dynamic and to maintain them, the cell relies on a large reserve of monomers. Classically, the G-actin pool has been thought of as homogenous. However, recent work has shown that actin monomers can exist in distinct groups that can be targeted to specific networks, where they drive and modify filament assembly in ways that can have profound effects on cellular behavior. This Review focuses on the potential factors that could create functionally distinct pools of actin monomers in the cell, including differences between the actin isoforms and the regulation of G-actin by monomer binding proteins, such as profilin and thymosin β4. Owing to difficulties in studying and visualizing G-actin, our knowledge over the precise role that specific actin monomer pools play in regulating cellular actin dynamics remains incomplete. Here, we discuss some of these unanswered questions and also provide a summary of the methodologies currently available for the imaging of G-actin.
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Affiliation(s)
- Kristen Skruber
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610, USA
| | - Tracy-Ann Read
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610, USA
| | - Eric A Vitriol
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610, USA
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6
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An In Vitro Potency Assay for Monitoring the Immunomodulatory Potential of Stromal Cell-Derived Extracellular Vesicles. Int J Mol Sci 2017; 18:ijms18071413. [PMID: 28671586 PMCID: PMC5535905 DOI: 10.3390/ijms18071413] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 06/09/2017] [Accepted: 06/29/2017] [Indexed: 02/06/2023] Open
Abstract
The regenerative and immunomodulatory activity of mesenchymal stromal cells (MSCs) is partially mediated by secreted vesicular factors. Extracellular vesicles (EVs) exocytosed by MSCs are gaining increased attention as prospective non-cellular therapeutics for a variety of diseases. However, the lack of suitable in vitro assays to monitor the therapeutic potential of EVs currently restricts their application in clinical studies. We have evaluated a dual in vitro immunomodulation potency assay that reproducibly reports the inhibitory effect of MSCs on induced T-cell proliferation and the alloantigen-driven mixed leukocyte reaction of pooled peripheral blood mononuclear cells in a dose-dependent manner. Phytohemagglutinin-stimulated T-cell proliferation was inhibited by MSC-derived EVs in a dose-dependent manner comparable to MSCs. In contrast, inhibition of alloantigen-driven mixed leukocyte reaction was only observed for MSCs, but not for EVs. Our results support the application of a cell-based in vitro potency assay for reproducibly determining the immunomodulatory potential of EVs. Validation of this assay can help establish reliable release criteria for EVs for future clinical studies.
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7
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Schevzov G, Vrhovski B, Bryce NS, Elmir S, Qiu MR, O'neill GM, Yang N, Verrills NM, Kavallaris M, Gunning PW. Tissue-specific Tropomyosin Isoform Composition. J Histochem Cytochem 2016; 53:557-70. [PMID: 15872049 DOI: 10.1369/jhc.4a6505.2005] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Four distinct genes encode tropomyosin (Tm) proteins, integral components of the actin microfilament system. In non-muscle cells, over 40 Tm isoforms are derived using alternative splicing. Distinct populations of actin filaments characterized by the composition of these Tm isoforms are found differentially sorted within cells ( Gunning et al. 1998b ). We hypothesized that these distinct intracellular compartments defined by the association of Tm isoforms may allow for independent regulation of microfilament function. Consequently, to understand the molecular mechanisms that give rise to these different microfilaments and their regulation, a cohort of fully characterized isoform-specific Tm antibodies was required. The characterization protocol initially involved testing the specificity of the antibodies on bacterially produced Tm proteins. We then confirmed that these Tm antibodies can be used to probe the expression and subcellular localization of different Tm isoforms by Western blot analysis, immunofluorescence staining of cells in culture, and immunohistochemistry of paraffin wax-embedded mouse tissues. These Tm antibodies, therefore, have the capacity to monitor specific actin filament populations in a range of experimental systems.
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Affiliation(s)
- Galina Schevzov
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, NSW, Sydney, Australia
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8
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Abstract
Actin is the central building block of the actin cytoskeleton, a highly regulated filamentous network enabling dynamic processes of cells and simultaneously providing structure. Mammals have six actin isoforms that are very conserved and thus share common functions. Tissue-specific expression in part underlies their differential roles, but actin isoforms also coexist in various cell types and tissues, suggesting specific functions and preferential interaction partners. Gene deletion models, antibody-based staining patterns, gene silencing effects, and the occurrence of isoform-specific mutations in certain diseases have provided clues for specificity on the subcellular level and its consequences on the organism level. Yet, the differential actin isoform functions are still far from understood in detail. Biochemical studies on the different isoforms in pure form are just emerging, and investigations in cells have to deal with a complex and regulated system, including compensatory actin isoform expression.
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Affiliation(s)
- Christophe Ampe
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, A. Baertsoenkaai 3, 9000, Ghent, Belgium.
| | - Marleen Van Troys
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, A. Baertsoenkaai 3, 9000, Ghent, Belgium
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9
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Reorganization of Synaptic Connections and Perineuronal Nets in the Deep Cerebellar Nuclei of Purkinje Cell Degeneration Mutant Mice. Neural Plast 2015; 2016:2828536. [PMID: 26819763 PMCID: PMC4706924 DOI: 10.1155/2016/2828536] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 09/10/2015] [Accepted: 09/15/2015] [Indexed: 12/22/2022] Open
Abstract
The perineuronal net (PN) is a subtype of extracellular matrix appearing as a net-like structure around distinct neurons throughout the whole CNS. PNs surround the soma, proximal dendrites, and the axonal initial segment embedding synaptic terminals on the neuronal surface. Different functions of the PNs are suggested which include support of synaptic stabilization, inhibition of axonal sprouting, and control of neuronal plasticity. A number of studies provide evidence that removing PNs or PN-components results in renewed neurite growth and synaptogenesis. In a mouse model for Purkinje cell degeneration, we examined the effect of deafferentation on synaptic remodeling and modulation of PNs in the deep cerebellar nuclei. We found reduced GABAergic, enhanced glutamatergic innervations at PN-associated neurons, and altered expression of the PN-components brevican and hapln4. These data refer to a direct interaction between ECM and synapses. The altered brevican expression induced by activated astrocytes could be required for an adequate regeneration by promoting neurite growth and synaptogenesis.
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10
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Migocka-Patrzałek M, Makowiecka A, Nowak D, Mazur AJ, Hofmann WA, Malicka-Błaszkiewicz M. β- and γ-Actins in the nucleus of human melanoma A375 cells. Histochem Cell Biol 2015; 144:417-28. [PMID: 26239425 PMCID: PMC4628621 DOI: 10.1007/s00418-015-1349-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/14/2015] [Indexed: 11/13/2022]
Abstract
Actin is a highly conserved protein that is expressed in all eukaryotic cells and has essential functions in the cytoplasm and the nucleus. Nuclear actin is involved in transcription by all three RNA polymerases, chromatin remodelling, RNA processing, intranuclear transport, nuclear export and in maintenance of the nuclear architecture. The nuclear actin level and polymerization state are important factors regulating nuclear processes such as transcription. Our study shows that, in contrast to the cytoplasm, the majority of endogenous nuclear actin is unpolymerized in human melanoma A375 cells. Most mammalian cells express the two non-muscle β- and γ-actin isoforms that differ in only four amino acids. Despite their sequence similarity, studies analysing the cytoplasmic functions of these isoforms demonstrated that β- and γ-actins show differences in localization and function. However, little is known about the involvement of the individual actin isoforms in nuclear processes. Here, we used the human melanoma A375 cell line to analyse actin isoforms in regard to their nuclear localization. We show that both β- and γ-non-muscle actin isoforms are present in nuclei of these cells. Immunolocalization studies demonstrate that both isoforms co-localize with RNA polymerase II and hnRNP U. However, we observe differences in the ratio of cytoplasmic to nuclear actin distribution between the isoforms. We show that β-actin has a significantly higher nucleus-to-cytoplasm ratio than γ-actin.
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Affiliation(s)
- Marta Migocka-Patrzałek
- Department of Animal Developmental Biology, Institute of Experimental Biology, Faculty of Biological Sciences, University of Wroclaw, Sienkiewicza 21, 50-335, Wroclaw, Poland.
- Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
- Department of Physiology and Biophysics, University at Buffalo State University of New York, Buffalo, NY, USA.
| | - Aleksandra Makowiecka
- Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Dorota Nowak
- Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Antonina J Mazur
- Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Wilma A Hofmann
- Department of Physiology and Biophysics, University at Buffalo State University of New York, Buffalo, NY, USA
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Wang P, Zhang N, Liang J, Li J, Han S, Li J. Micro-RNA-30a regulates ischemia-induced cell death by targeting heat shock protein HSPA5 in primary cultured cortical neurons and mouse brain after stroke. J Neurosci Res 2015; 93:1756-68. [DOI: 10.1002/jnr.23637] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 07/27/2015] [Accepted: 08/06/2015] [Indexed: 01/15/2023]
Affiliation(s)
- Peng Wang
- Department of Neurobiology and Center of Stroke; Beijing Institute for Brain Disorders, Capital Medical University; Beijing People's Republic of China
- Central Laboratory, Liaoning Medical University; Jinzhou People's Republic of China
| | - Nan Zhang
- Department of Anatomy; Capital Medical University; Beijing People's Republic of China
| | - Jia Liang
- Central Laboratory, Liaoning Medical University; Jinzhou People's Republic of China
| | - Jiefei Li
- Department of Neurobiology and Center of Stroke; Beijing Institute for Brain Disorders, Capital Medical University; Beijing People's Republic of China
| | - Song Han
- Department of Neurobiology and Center of Stroke; Beijing Institute for Brain Disorders, Capital Medical University; Beijing People's Republic of China
| | - Junfa Li
- Department of Neurobiology and Center of Stroke; Beijing Institute for Brain Disorders, Capital Medical University; Beijing People's Republic of China
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12
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Steele JW, Brautigam H, Short JA, Sowa A, Shi M, Yadav A, Weaver CM, Westaway D, Fraser PE, St George-Hyslop PH, Gandy S, Hof PR, Dickstein DL. Early fear memory defects are associated with altered synaptic plasticity and molecular architecture in the TgCRND8 Alzheimer's disease mouse model. J Comp Neurol 2014; 522:2319-35. [PMID: 24415002 DOI: 10.1002/cne.23536] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 12/23/2013] [Accepted: 01/07/2014] [Indexed: 11/08/2022]
Abstract
Alzheimer's disease (AD) is a complex and slowly progressing dementing disorder that results in neuronal and synaptic loss, deposition in brain of aberrantly folded proteins, and impairment of spatial and episodic memory. Most studies of mouse models of AD have employed analyses of cognitive status and assessment of amyloid burden, gliosis, and molecular pathology during disease progression. Here we sought to understand the behavioral, cellular, ultrastructural, and molecular changes that occur at a pathological stage equivalent to the early stages of human AD. We studied the TgCRND8 mouse, a model of aggressive AD amyloidosis, at an early stage of plaque pathology (3 months of age) in comparison to their wildtype littermates and assessed changes in cognition, neuron and spine structure, and expression of synaptic glutamate receptor proteins. We found that, at this age, TgCRND8 mice display substantial plaque deposition in the neocortex and hippocampus and impairment on cued and contextual memory tasks. Of particular interest, we also observed a significant decrease in the number of neurons in the hippocampus. Furthermore, analysis of CA1 neurons revealed significant changes in apical and basal dendritic spine types, as well as altered expression of GluN1 and GluA2 receptors. This change in molecular architecture within the hippocampus may reflect a rising representation of inherently less stable thin spine populations, which can cause cognitive decline. These changes, taken together with toxic insults from amyloid-β protein, may underlie the observed neuronal loss.
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Affiliation(s)
- John W Steele
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY, 10065, USA; Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA; Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
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13
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Simiczyjew A, Mazur AJ, Popow-Woźniak A, Malicka-Błaszkiewicz M, Nowak D. Effect of overexpression of β- and γ-actin isoforms on actin cytoskeleton organization and migration of human colon cancer cells. Histochem Cell Biol 2014; 142:307-22. [PMID: 24682235 PMCID: PMC4133152 DOI: 10.1007/s00418-014-1199-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/09/2014] [Indexed: 01/26/2023]
Abstract
Actins are eukaryotic proteins, which are involved in diverse cellular functions including muscle contraction, cell motility, adhesion and maintenance of cell shape. Cytoplasmic actin isoforms β and γ are ubiquitously expressed and essential for cell functioning. However, their unique contributions are not very well understood. The aim of this study was to determine the effect of β- and γ-actin overexpression on the migration capacity and actin cytoskeleton organization of human colon adenocarcinoma BE cells. In cells overexpressing β- or γ-actin, distinct cytoskeletal actin rearrangements were observed under the laser scanning confocal microscope. Overexpressed actins localized at the submembranous region of the cell body, especially near to the leading edge and on the tips of pseudopodia. The cells transfected with plasmids containing cDNA for β- or γ-actin were characterized by increased migration and invasion capacities. However, the migration velocity was statistically significantly higher only in the case of γ-actin overexpressing cells. In conclusion, the increased level of β- or γ-actin leads to actin cytoskeletal remodeling followed by an increase in migration and invasion capacities of human colon BE cells. These data suggest that expression of both actin isoforms has an impact on cancer cell motility, with the subtle predominance of γ-actin, and may influence invasiveness of human colon cancer.
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Affiliation(s)
- Aleksandra Simiczyjew
- Department of Cell Pathology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Antonina Joanna Mazur
- Department of Cell Pathology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Agnieszka Popow-Woźniak
- Department of Cell Pathology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Maria Malicka-Błaszkiewicz
- Department of Cell Pathology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Dorota Nowak
- Department of Cell Pathology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
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14
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Curthoys NM, Freittag H, Connor A, Desouza M, Brettle M, Poljak A, Hall A, Hardeman E, Schevzov G, Gunning PW, Fath T. Tropomyosins induce neuritogenesis and determine neurite branching patterns in B35 neuroblastoma cells. Mol Cell Neurosci 2013; 58:11-21. [PMID: 24211701 DOI: 10.1016/j.mcn.2013.10.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 10/21/2013] [Accepted: 10/29/2013] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND The actin cytoskeleton is critically involved in the regulation of neurite outgrowth. RESULTS The actin cytoskeleton-associated protein tropomyosin induces neurite outgrowth in B35 neuroblastoma cells and regulates neurite branching in an isoform-dependent manner. CONCLUSIONS Our data indicate that tropomyosins are key regulators of the actin cytoskeleton during neurite outgrowth. SIGNIFICANCE Revealing the molecular machinery that regulates the actin cytoskeleton during neurite outgrowth may provide new therapeutic strategies to promote neurite regeneration after nerve injury. SUMMARY The formation of a branched network of neurites between communicating neurons is required for all higher functions in the nervous system. The dynamics of the actin cytoskeleton is fundamental to morphological changes in cell shape and the establishment of these branched networks. The actin-associated proteins tropomyosins have previously been shown to impact on different aspects of neurite formation. Here we demonstrate that an increased expression of tropomyosins is sufficient to induce the formation of neurites in B35 neuroblastoma cells. Furthermore, our data highlight the functional diversity of different tropomyosin isoforms during neuritogenesis. Tropomyosins differentially impact on the expression levels of the actin filament bundling protein fascin and increase the formation of filopodia along the length of neurites. Our data suggest that tropomyosins are central regulators of actin filament populations which drive distinct aspects of neuronal morphogenesis.
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Affiliation(s)
- Nikki Margarita Curthoys
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia; Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Hannah Freittag
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia; Neuromuscular and Regenerative Medicine Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Andrea Connor
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia; Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Melissa Desouza
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia; Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Merryn Brettle
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Anne Poljak
- Bioanalytical Mass Spectrometry Facility, Bioanalytical Centre, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Amelia Hall
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Edna Hardeman
- Neuromuscular and Regenerative Medicine Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Galina Schevzov
- Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Peter William Gunning
- Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Thomas Fath
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia.
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15
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Astrocytes and glutamate homoeostasis in Alzheimer's disease: a decrease in glutamine synthetase, but not in glutamate transporter-1, in the prefrontal cortex. ASN Neuro 2013; 5:273-82. [PMID: 24059854 PMCID: PMC3791522 DOI: 10.1042/an20130017] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Astrocytes control tissue equilibrium and hence define the homoeostasis and function of the CNS (central nervous system). Being principal homoeostatic cells, astroglia are fundamental for various forms of neuropathology, including AD (Alzheimer's disease). AD is a progressive neurodegenerative disorder characterized by the loss of cognitive functions due to specific lesions in mnesic-associated regions, including the mPFC (medial prefrontal cortex). Here, we analyzed the expression of GS (glutamine synthetase) and GLT-1 (glutamate transporter-1) in astrocytes in the mPFC during the progression of AD in a triple-transgenic mouse model (3xTg-AD). GS is an astrocyte-specific enzyme, responsible for the intracellular conversion of glutamate into glutamine, whereas the removal of glutamate from the extracellular space is accomplished mainly by astroglia-specific GLT-1. We found a significant decrease in the numerical density (Nv, cells/mm3) of GS-positive astrocytes from early to middle ages (1–9 months; at the age of 1 month by 17%, 6 months by 27% and 9 months by 27% when compared with control animals) in parallel with a reduced expression of GS (determined by Western blots), which started at the age of 6 months and was sustained up to 12 months of age. We did not, however, find any changes in the expression of GLT-1, which implies an intact glutamate uptake mechanism. Our results indicate that the decrease in GS expression may underlie a gradual decline in the vital astrocyte-dependent glutamate–glutamine conversion pathway, which in turn may compromise glutamate homoeostasis, leading towards failures in synaptic connectivity with deficient cognition and memory.
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16
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Actin isoforms in neuronal development and function. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 301:157-213. [PMID: 23317819 DOI: 10.1016/b978-0-12-407704-1.00004-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The actin cytoskeleton contributes directly or indirectly to nearly every aspect of neuronal development and function. This diversity of functions is often attributed to actin regulatory proteins, although how the composition of the actin cytoskeleton itself may influence its function is often overlooked. In neurons, the actin cytoskeleton is composed of two distinct isoforms, β- and γ-actin. Functions for β-actin have been investigated in axon guidance, synaptogenesis, and disease. Insight from loss-of-function in vivo studies has also revealed novel roles for β-actin in select brain structures and behaviors. Conversely, very little is known regarding functions of γ-actin in neurons. The dysregulation or mutation of both β- and γ-actin has been implicated in multiple human neurological disorders, however, demonstrating the critical importance of these still poorly understood proteins. This chapter highlights what is currently known regarding potential distinct functions for β- and γ-actin in neurons as well as the significant areas that remain unexplored.
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17
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Askvig JM, Lo DY, Sudbeck AW, Behm KE, Leiphon LJ, Watt JA. Inhibition of the Jak-STAT pathway prevents CNTF-mediated survival of axotomized oxytocinergic magnocellular neurons in organotypic cultures of the rat supraoptic nucleus. Exp Neurol 2012; 240:75-87. [PMID: 23123407 DOI: 10.1016/j.expneurol.2012.10.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 10/15/2012] [Accepted: 10/24/2012] [Indexed: 11/19/2022]
Abstract
Previous studies have demonstrated that ciliary neurotrophic factor (CNTF) enhances survival and process outgrowth from magnocellular neurons in the paraventricular (PVN) and the supraoptic (SON) nuclei. However, the mechanisms by which CNTF facilitates these processes remain to be determined. Therefore, the aim of this study was to identify the immediate signal transduction events that occur within the rat SON following administration of exogenous rat recombinant CNTF (rrCNTF) and to determine the contribution of those intracellular signaling pathway(s) to neuronal survival and process outgrowth, respectively. Immunohistochemical and Western blot analyses demonstrated that axonal injury and acute unilateral pressure injection of 100 ng/μl of rrCNTF directly over the rat SON resulted in a rapid and transient increase in phosphorylated-STAT3 (pSTAT3) in astrocytes but not neurons in the SON in vivo. Utilizing rat hypothalamic organotypic explant cultures, we then demonstrated that administration of 25 ng/ml rrCNTF for 14days significantly increased the survival and process outgrowth of OT magnocellular neurons. In addition, pharmacological inhibition of the Jak-STAT pathway via AG490 and cucurbitacin I significantly reduced the survival of OT magnocellular neurons in the SON and PVN; however, the contribution of the Jak-STAT pathway to CNTF-mediated process outgrowth remains to be determined. Together, these data indicate that CNTF-induced survival of OT magnocellular neurons is mediated indirectly through astrocytes via the Jak-STAT signaling pathway.
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Affiliation(s)
- Jason M Askvig
- Department of Anatomy & Cell Biology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58203, USA.
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18
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Matsumura S, Sakurai K, Shinomiya T, Fujitani N, Key K, Ohashi M. Biochemical and immunohistochemical characterization of the isoforms of myosin and actin in human placenta. Placenta 2011; 32:347-55. [PMID: 21420731 DOI: 10.1016/j.placenta.2011.02.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 02/24/2011] [Accepted: 02/24/2011] [Indexed: 11/29/2022]
Abstract
Human placenta has long been known to contain large quantities of smooth muscle-type myosin and actin, while precise isoform compositions of its contractile proteins are not known. To determine the isoform compositions, myosin and actin were extracted from human term placentas and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting by using isoform-specific monoclonal anti-myosin and anti-actin antibodies. The placental myosin was found to be composed of about 65% of a nonmuscle-type heavy chain isoform (MIIA), each about 15% of two smooth muscle-type heavy chain isoforms (SM1 and SM2) and about 5% of a brain/fetus-type heavy chain isoform (MIIB2). Whereas the MIIA isoform was present in both vascular and extravascular tissues, the SM1 isoform was localized almost only in the vascular tissue. Similarly, human term placenta was found to contain approximately 60, 30, and 10% of β-nonmuscle, α-smooth muscle, γ-smooth muscle actin isoforms, respectively. The β-nonmuscle actin was located primarily in the extravascular tissue, while the α-smooth muscle actin was located mostly in the vascular tissue. The extravascular tissue of the human term placenta thus appears to be composed of almost only nonmuscle-type isoforms of contractile proteins. The vascular tissue appears to be composed of both smooth muscle-type and nonmuscle-type isoforms of contractile proteins.
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Affiliation(s)
- S Matsumura
- Department of Biophysics, Kobe University Graduate School of Health Sciences, Suma, Japan.
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19
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Hippocampal neuronal nitric oxide synthase (nNOS) is regulated by nicotine and stress in female but not in male rats. Brain Res 2011; 1368:134-42. [DOI: 10.1016/j.brainres.2010.10.090] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Revised: 10/21/2010] [Accepted: 10/26/2010] [Indexed: 12/14/2022]
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20
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GLYN MATTHEWC, WARD BARBARAJ. A β‐Actin Isotype Is Present in Rat Cardiac Endothelial Cells But Not in Cardiac Myocytes. Microcirculation 2010. [DOI: 10.1111/j.1549-8719.1998.tb00074.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- MATTHEW C.P. GLYN
- Department of Molecular and Cellular Biology, Division of Biomedical Sciences, St. Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary and Westfield College, London, UK
| | - BARBARA J. WARD
- Department of Molecular and Cellular Biology, Division of Biomedical Sciences, St. Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary and Westfield College, London, UK
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21
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Dugina V, Zwaenepoel I, Gabbiani G, Clément S, Chaponnier C. Beta and gamma-cytoplasmic actins display distinct distribution and functional diversity. J Cell Sci 2009; 122:2980-8. [PMID: 19638415 DOI: 10.1242/jcs.041970] [Citation(s) in RCA: 164] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Using newly generated monoclonal antibodies, we have compared the distribution of beta- and gamma-cytoplasmic actin in fibroblastic and epithelial cells, in which they play crucial roles during various key cellular processes. Whereas beta-actin is preferentially localized in stress fibers, circular bundles and at cell-cell contacts, suggesting a role in cell attachment and contraction, gamma-actin displays a more versatile organization, according to cell activities. In moving cells, gamma-actin is mainly organized as a meshwork in cortical and lamellipodial structures, suggesting a role in cell motility; in stationary cells, gamma-actin is also recruited into stress fibers. beta-actin-depleted cells become highly spread, display broad protrusions and reduce their stress-fiber content; by contrast, gamma-actin-depleted cells acquire a contractile phenotype with thick actin bundles and shrinked lamellar and lamellipodial structures. Moreover, beta- and gamma-actin depleted fibroblasts exhibit distinct changes in motility compared with their controls, suggesting a specific role for each isoform in cell locomotion. Our results reveal new aspects of beta- and gamma-actin organization that support their functional diversity.
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Affiliation(s)
- Vera Dugina
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
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22
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Krajacic A, Ghosh M, Puentes R, Pearse DD, Fouad K. Advantages of delaying the onset of rehabilitative reaching training in rats with incomplete spinal cord injury. Eur J Neurosci 2009; 29:641-51. [PMID: 19222562 DOI: 10.1111/j.1460-9568.2008.06600.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have previously reported that rehabilitative reaching training initiated 4 days following an incomplete cervical spinal cord injury (SCI) in adult rats promotes plasticity and task-specific recovery. This training, however, also resulted in impairments in an untrained task. Here we examined whether delaying the rehabilitative training following cervical SCI is still effective in promoting task-specific recovery, but circumvents impairments in an untrained task, comparable to what has been reported in stroke models. Therefore, reaching training for a period of 6 weeks was initiated at Day 12 following a cervical dorso-lateral quadrant lesion. Thereupon the rats' ability to reach and to walk on a horizontal ladder (i.e. the untrained task) was assessed, and 8 weeks post-injury cortical map changes were investigated through microstimulation. Further, we examined changes in phospho protein kinase A (pPKA) levels following an immediate and a delayed onset of reaching training in rats with cervical SCI. We found that delayed rehabilitative training was comparably effective as immediate training in promoting task-specific recovery and sprouting of injured axons. Importantly, delayed training did not impair the performance on horizontal ladder walking. Strikingly, only delayed reaching training restored cortical PKA levels that had dropped significantly over 2 weeks post-injury. Additionally, delayed training did not influence cortical map changes following injury, but decreased white matter damage. In conclusion, our results show that a short delay in the onset of training in a forelimb task significantly alters our outcome measures, which should be considered in future rehabilitative approaches.
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23
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Schroeder U, Graff A, Buchmeier S, Rigler P, Silvan U, Tropel D, Jockusch BM, Aebi U, Burkhard P, Schoenenberger CA. Peptide nanoparticles serve as a powerful platform for the immunogenic display of poorly antigenic actin determinants. J Mol Biol 2008; 386:1368-81. [PMID: 19063898 DOI: 10.1016/j.jmb.2008.11.023] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 11/14/2008] [Accepted: 11/15/2008] [Indexed: 11/19/2022]
Abstract
The role of actin in transcription and RNA processing is now widely accepted but the form of nuclear actin remains enigmatic. Monomeric, oligomeric or polymeric forms of actin seem to be involved in nuclear functions. Moreover, uncommon forms of actin such as the "lower dimer" have been observed in vitro. Antibodies have been pivotal in revealing the presence and distribution of different forms of actin in different cellular locations. Because of its high degree of conservation, actin is a poor immunogen and only few specific actin antibodies are available. To unravel the mystery of less common forms of actin, in particular those in the nucleus, we chose to tailor monoclonal antibodies to recognize distinct forms of actin. To increase the immune response, we used a new approach based on peptide nanoparticles, which are designed to mimic an icosahedral virus capsid and allow the repetitive, ordered display of a specific epitope on their surface. Actin sequences representing the highly conserved "hydrophobic loop," which is buried in the filamentous actin filament, were grafted onto the surface of nanoparticles by genetic engineering. After immunization with "loop nanoparticles," a number of monoclonal antibodies were established that bind to the hydrophobic loop both in vitro and in situ. Immunofluorescence studies on cells revealed that filamentous actin filaments were only labeled once the epitope had been exposed. Our studies indicate that self-assembling peptide nanoparticles represent a versatile platform that can easily be customized to present antigenic determinants in repetitive, ordered arrays and elicit an immune response against poor antigens.
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Affiliation(s)
- Ulrich Schroeder
- M. E. Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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24
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The dimensions and composition of stereociliary rootlets in mammalian cochlear hair cells: comparison between high- and low-frequency cells and evidence for a connection to the lateral membrane. J Neurosci 2008; 28:6342-53. [PMID: 18562604 DOI: 10.1523/jneurosci.1154-08.2008] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The sensory bundle of vertebrate cochlear hair cells consists of actin-containing stereocilia that are thought to bend at their ankle during mechanical stimulation. Stereocilia have dense rootlets that extend through the ankle region to anchor them into the cuticular plate. Because this region may be important in bundle stiffness and durability during prolonged stimulation at high frequencies, we investigated the structure and dimensions of rootlets relative to the stereocilia in apical (low-frequency) and basal (high-frequency) regions of rodent cochleae using light and electron microscopy. Their composition was investigated using postembedding immunogold labeling of tropomyosin, spectrin, beta-actin, gamma-actin, espin, and prestin. The rootlets have a thick central core that widens at the ankle, and are embedded in a filamentous meshwork in the cuticular plate. Within a particular frequency region, rootlet length correlates with stereociliary height but between regions it changes disproportionately; apical stereocilia are, thus, approximately twice the height of basal stereocilia in equivalent rows, but rootlet lengths increase much less. Some rootlets contact the tight junctions that underlie the ends of the bundle. Rootlets contain spectrin, tropomyosin, and beta- and gamma-actin, but espin was not detected; spectrin is also evident near the apical and junctional membranes, whereas prestin is confined to the basolateral membrane below the junctions. These data suggest that rootlets strengthen the ankle region to provide durability and may contact with the lateral wall either to give additional anchoring of the stereocilia or to provide a route for interactions between the bundle and the lateral wall.
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25
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Kacem K, Sercombe R. Similar pathological effects of sympathectomy and hypercholesterolemia on arterial smooth muscle cells and fibroblasts. Acta Histochem 2008; 110:302-13. [PMID: 18374968 DOI: 10.1016/j.acthis.2007.11.007] [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: 06/03/2007] [Revised: 11/27/2007] [Accepted: 11/27/2007] [Indexed: 11/28/2022]
Abstract
In a previous study, we showed that after sympathectomy, the femoral (FA) but not the basilar (BA) artery from non-pathological rabbits manifests migration of adventitial fibroblasts (FBs) into the media and loss of medial smooth muscle cells (SMCs). The aim of the present study was to verify whether similar behaviour of arteries occurred in the pathological context of atherosclerosis. Thus, similar experiments were conducted on hypercholesterolemic rabbits, which were chemically sympathectomized with 6-hydroxydopamine (n=4) or treated with vehicle for control (n=5). Cross-sections of BA and FA were immunolabelled for five markers of phenotypic modulation of vascular SMCs and FBs: vimentin, desmin, alpha-smooth muscle actin, beta-isoform of actin, and h-caldesmon and examined using a confocal microscope. Also, 3D images were constructed and morphometric analysis performed using image analysis software. Both intact and sympathectomized BA and FA developed atherosclerotic plaques, but the thickening of the intima was more advanced in sympathectomized animals, as judged by increased plaque frequency and by the phenotypic modulation of SMCs in the intima. Our results show that in the media of FAs hypercholesterolemia induces changes similar to those observed in sympathectomized rabbits in non-pathological conditions, i.e., migration of adventitial FBs to the media and loss of medial SMCs. These latter changes, which can be ascribed to pathological events, were accentuated after sympathectomy in the hypercholesterolemic rabbits. The present study reveals that pathological events, including migration and phenotypic modulation of vascular FBs and loss of SMCs, may be under the influence of sympathetic nerves.
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Affiliation(s)
- K Kacem
- Laboratoire de Pathologies Vasculaires, Faculté des Sciences de Bizerte, 7021 Jarzouna, Tunisia.
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26
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Chadjichristos CE, Morel S, Derouette JP, Sutter E, Roth I, Brisset AC, Bochaton-Piallat ML, Kwak BR. Targeting connexin 43 prevents platelet-derived growth factor-BB-induced phenotypic change in porcine coronary artery smooth muscle cells. Circ Res 2008; 102:653-60. [PMID: 18239136 DOI: 10.1161/circresaha.107.170472] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We previously reported that reducing the expression of the gap junction protein connexin (Cx)43 in mice restricts intimal thickening formation after acute vascular injury by limiting the inflammatory response and the proliferation and migration of smooth muscle cells (SMCs) toward the damaged site. SMC populations isolated from porcine coronary artery exhibit distinct phenotypes: spindle-shaped (S) and rhomboid (R). S-SMCs are predominant in the normal media, whereas R-SMCs are recovered in higher proportion from stent-induced intimal thickening, suggesting that they participate in the restenotic process. Here, we further investigate the relationship between connexin expression and SMC phenotypes using porcine coronary artery SMCs. Cx40 was highly expressed in normal media of porcine coronary artery in vivo, whereas Cx43 was barely detectable. In contrast, Cx40 was downregulated and Cx43 was markedly upregulated in stent-induced intimal thickening. In vitro, S-SMCs expressed Cx40 and Cx43. In R-SMCs, Cx43 expression was increased and Cx40 was absent. We confirmed that S-SMCs treated with platelet-derived growth factor-BB acquire an R phenotype. This was accompanied by an upregulation of Cx43 and a loss of Cx40. Importantly, platelet-derived growth factor-BB-induced S-to-R phenotypic change was prevented by a reduction of Cx43 expression with antisense, ie, S-SMCs retained their typical elongated appearance and the expression of alpha-smooth muscle actin, a well-known SMC differentiation marker, whereas the expression of S100A4, a typical marker of R-SMCs, was prevented. In conclusion, limiting Cx43 expression in S-SMCs prevents platelet-derived growth factor-BB-induced S-to-R modulation. This suggests that Cx43 may be an additional target for local delivery strategies aimed at reducing restenosis.
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MESH Headings
- Actins/metabolism
- Animals
- Becaplermin
- Cell Differentiation
- Cell Movement
- Cell Shape
- Cells, Cultured
- Connexin 43/antagonists & inhibitors
- Connexin 43/genetics
- Connexin 43/metabolism
- Connexins/metabolism
- Coronary Stenosis/etiology
- Coronary Stenosis/metabolism
- Coronary Stenosis/pathology
- Coronary Vessels/metabolism
- Coronary Vessels/pathology
- Disease Models, Animal
- Female
- Gap Junctions/drug effects
- Gap Junctions/metabolism
- Glycyrrhetinic Acid/analogs & derivatives
- Glycyrrhetinic Acid/pharmacology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/pathology
- Peptides/pharmacology
- Phenotype
- Platelet-Derived Growth Factor/metabolism
- Proto-Oncogene Proteins c-sis
- RNA Interference
- RNA, Small Interfering/metabolism
- Recombinant Proteins/metabolism
- S100 Proteins/metabolism
- Signal Transduction/drug effects
- Stents/adverse effects
- Sus scrofa
- Time Factors
- Tunica Intima/metabolism
- Tunica Intima/pathology
- Gap Junction alpha-5 Protein
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Affiliation(s)
- Christos E Chadjichristos
- Division of Cardiology, Geneva University Hospitals, Faculty of Medicine, University of Geneva, Switzerland
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27
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Schevzov G, Fath T, Vrhovski B, Vlahovich N, Rajan S, Hook J, Joya JE, Lemckert F, Puttur F, Lin JJC, Hardeman EC, Wieczorek DF, O'Neill GM, Gunning PW. Divergent regulation of the sarcomere and the cytoskeleton. J Biol Chem 2007; 283:275-283. [PMID: 17951248 DOI: 10.1074/jbc.m704392200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The existence of a feedback mechanism regulating the precise amounts of muscle structural proteins, such as actin and the actin-associated protein tropomyosin (Tm), in the sarcomeres of striated muscles is well established. However, the regulation of nonmuscle or cytoskeletal actin and Tms in nonmuscle cell structures has not been elucidated. Unlike the thin filaments of striated muscles, the actin cytoskeleton in nonmuscle cells is intrinsically dynamic. Given the differing requirements for the structural integrity of the actin thin filaments of the sarcomere compared with the requirement for dynamicity of the actin cytoskeleton in nonmuscle cells, we postulated that different regulatory mechanisms govern the expression of sarcomeric versus cytoskeletal Tms, as key regulators of the properties of the actin cytoskeleton. Comprehensive analyses of tissues from transgenic and knock-out mouse lines that overexpress the cytoskeletal Tms, Tm3 and Tm5NM1, and a comparison with sarcomeric Tms provide evidence for this. Moreover, we show that overexpression of a cytoskeletal Tm drives the amount of filamentous actin.
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Affiliation(s)
- Galina Schevzov
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales 2145, Australia; Discipline of Paediatrics and Child Health, Sydney, New South Wales 2006, Australia
| | - Thomas Fath
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales 2145, Australia; Discipline of Paediatrics and Child Health, Sydney, New South Wales 2006, Australia
| | - Bernadette Vrhovski
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales 2145, Australia
| | - Nicole Vlahovich
- Muscle Development Unit, The Children's Medical Research Institute, Locked Bag 23, Wentworthville, New South Wales 2145, Australia, the
| | - Sudarsan Rajan
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, Cincinnati, Ohio 45267-0524
| | - Jeff Hook
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales 2145, Australia
| | - Josephine E Joya
- Muscle Development Unit, The Children's Medical Research Institute, Locked Bag 23, Wentworthville, New South Wales 2145, Australia, the
| | - Frances Lemckert
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales 2145, Australia
| | - Franz Puttur
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales 2145, Australia
| | - Jim J-C Lin
- Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242-1324
| | - Edna C Hardeman
- Muscle Development Unit, The Children's Medical Research Institute, Locked Bag 23, Wentworthville, New South Wales 2145, Australia, the; Faculty of Medicine, University of Sydney, Sydney, New South Wales 2006, Australia, the
| | - David F Wieczorek
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, Cincinnati, Ohio 45267-0524
| | - Geraldine M O'Neill
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales 2145, Australia; Discipline of Paediatrics and Child Health, Sydney, New South Wales 2006, Australia
| | - Peter W Gunning
- Oncology Research Unit, The Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales 2145, Australia; Discipline of Paediatrics and Child Health, Sydney, New South Wales 2006, Australia.
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Clément S, Stouffs M, Bettiol E, Kampf S, Krause KH, Chaponnier C, Jaconi M. Expression and function of alpha-smooth muscle actin during embryonic-stem-cell-derived cardiomyocyte differentiation. J Cell Sci 2006; 120:229-38. [PMID: 17179203 DOI: 10.1242/jcs.03340] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Three alpha-muscle actin isoforms are sequentially expressed during in vivo cardiac development. alpha-Smooth muscle actin is first and transiently expressed, followed by alpha-skeletal and finally alpha-cardiac actin. The significance of these transitions in actin gene expression during myogenesis remains to be determined. To understand whether actin isoforms have specific functions during cardiac development and cardiomyocyte contractility, we have hampered alpha-smooth muscle and alpha-skeletal actin expression and organization during embryonic stem cell differentiation towards cardiomyocyte. We show that the sequence of actin isoform expression displays similar pattern in the in vitro model and in mouse heart embryogenesis. Treatment with an interfering fusion peptide containing the N-terminal sequence of alpha-smooth muscle actin during a time window preceding spontaneous beating, prevents proper cardiac sarcomyogenesis, whereas alpha-skeletal actin-fusion peptide has no effect. Knockdown of alpha-smooth muscle actin in embryonic stem cells using RNA interference also affects cardiac differentiation. The application of both fusion peptides on beating embryoid bodies impairs frequency. These results suggest specific functional activities for actin isoforms in cardiogenesis and cardiomyocyte contractility.
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Affiliation(s)
- Sophie Clément
- Department of Geriatrics, Laboratory of Ageing, Geneva Hospital, Chêne-Bourg, Geneva, Switzerland.
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29
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Kacem K, Sercombe R. Differing influence of sympathectomy on smooth muscle cells and fibroblasts in cerebral and peripheral muscular arteries. Auton Neurosci 2006; 124:38-48. [PMID: 16426901 DOI: 10.1016/j.autneu.2005.11.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Revised: 01/31/2005] [Accepted: 11/01/2005] [Indexed: 11/29/2022]
Abstract
In the present study, we examined the effect of sympathectomy on the distribution and the relative expression of cytoskeletal proteins used as markers of phenotypic modulation of vascular smooth muscle cells (SMCs) and myofibroblasts (MFBs) in rabbit femoral (FA) and basilar (BA) arteries. Adult rabbits were treated either with repeated 6-hydroxydopamine (6-OHDA) for sympathectomy or with vehicle for control. Cross sections taken from sympathectomized and control arteries 79 days later were immunolabelled for vimentin, desmin, alpha-smooth muscle actin (alpha-SM actin), beta-isoform of actin and h-caldesmon. The distribution of these proteins and the intensity of fluorescent labelled SMCs were examined under a confocal microscope. In the sympathectomized BA, there was no change for desmin, vimentin and h-caldesmon expression, but the expression of both alpha-SM actin and the beta-isoform was significantly higher (+19% and +30%, respectively). In the sympathectomized FA, the expression of the alpha- and beta-isoforms of actin remained unchanged, whereas those of desmin and vimentin were significantly higher (+35% and 17%, respectively) and h-caldesmon expression was lowered by 13%. In contrast to intact FAs, the external layers of sympathectomized FAs revealed migration of fibroblasts from the adventitia and death of SMCs. These results strongly suggest that sympathetic nerves intervene in the cytoskeletal protein remodelling through phenotypic modulation of both SMCs and MFBs during post-natal development, and in pathologies involving similar phenomena, such as atherosclerosis.
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Affiliation(s)
- K Kacem
- Laboratoire de Pathologies Vasculaires, Faculté des Sciences de Bizerte, 7021 Jarzouna, Bizerte, Tunisia.
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30
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Furness DN, Katori Y, Mahendrasingam S, Hackney CM. Differential distribution of beta- and gamma-actin in guinea-pig cochlear sensory and supporting cells. Hear Res 2006; 207:22-34. [PMID: 16024192 DOI: 10.1016/j.heares.2005.05.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Accepted: 05/12/2005] [Indexed: 11/15/2022]
Abstract
Sensory and supporting cells of the mammalian organ of Corti have cytoskeletons containing beta- and gamma-actin isoforms which have been described as having differing intracellular distributions in chick cochlear hair cells. Here, we have used post-embedding immunogold labelling for beta- and gamma-actin to investigate semiquantitatively how they are distributed in the guinea-pig cochlea and to compare different frequency locations. Amounts of beta-actin decrease and gamma-actin increase in the order, outer pillar cells, inner pillar cells, Deiters' cells and hair cells. There is also more beta-actin and less gamma-actin in outer pillar cells in higher than lower frequency regions. In hair cells, beta-actin is present in the cuticular plate but is more concentrated in the stereocilia, especially in the rootlets and towards the periphery of their shafts; labelling densities for gamma-actin differ less between these locations and it is the predominant isoform of the hair-cell lateral wall. Alignments of immunogold particles suggest beta-actin and gamma-actin form homomeric filaments. These data confirm differential distribution of these actin isoforms in the mammalian cochlea and reveal systematic differences between sensory and supporting cells. Increased expression of beta-actin in outer pillar cells towards the cochlear base may contribute to the greater stiffness of this region.
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Affiliation(s)
- D N Furness
- MacKay Institute of Communication and Neuroscience, School of Life Sciences, Keele University, Staffordshire ST5 5BG, United Kingdom.
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31
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Karas K, Brauer P, Petzel D. Actin redistribution in mosquito malpighian tubules after a blood meal and cyclic AMP stimulation. JOURNAL OF INSECT PHYSIOLOGY 2005; 51:1041-54. [PMID: 15993891 DOI: 10.1016/j.jinsphys.2005.05.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2004] [Revised: 05/05/2005] [Accepted: 05/05/2005] [Indexed: 05/03/2023]
Abstract
Fluid secretion by mosquito Malpighian tubules is critical to maintaining fluid and electrolyte balance after a blood meal. Endogenous cAMP levels increase in Malpighian tubules after a blood meal. Here, we determined if corresponding changes in intracellular actin distribution occur after a blood meal or dibutyryl-cAMP (db-cAMP) stimulation and whether altering actin turnover inhibits secretion. In untreated Malpighian tubules, beta-actin immunostaining was more intense in the apical region of adult Malpighian tubules than in the cytoplasm. Stimulation by a blood meal or db-cAMP significantly decreased beta-actin immunostaining in the non-apical region of the cell. Db-cAMP had similar effects in larvae and pupae Malpighian tubules. In contrast, no detectable shift in F-actin distribution was detected; however, F-actin bundles within the cytoplasm increased in size after treatment with db-cAMP. Pretreatment of Malpighian tubules with agents perturbing actin fiber assembly and disassembly decreased basal secretion rates and inhibited the stimulatory effects of db-cAMP. Our results show (1) beta-actin redistributes toward the apical membrane after a blood meal and this correlates temporally with increase urine flow rate and intracellular cAMP levels, (2) Malpighian tubules from all developmental stages exhibit this same response to db-cAMP-stimulation, and (3) dynamic assembly and disassembly of beta-actin is required for db-cAMP-stimulated secretion.
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Affiliation(s)
- Katherine Karas
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
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32
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Hofmann WA, Stojiljkovic L, Fuchsova B, Vargas GM, Mavrommatis E, Philimonenko V, Kysela K, Goodrich JA, Lessard JL, Hope TJ, Hozak P, de Lanerolle P. Actin is part of pre-initiation complexes and is necessary for transcription by RNA polymerase II. Nat Cell Biol 2004; 6:1094-101. [PMID: 15502823 DOI: 10.1038/ncb1182] [Citation(s) in RCA: 282] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2004] [Accepted: 09/20/2004] [Indexed: 11/09/2022]
Abstract
Actin is abundant in the nucleus and has been implicated in transcription; however, the nature of this involvement has not been established. Here we demonstrate that beta-actin is critically involved in transcription because antibodies directed against beta-actin, but not muscle actin, inhibited transcription in vivo and in vitro. Chromatin immunoprecipitation assays demonstrated the recruitment of actin to the promoter region of the interferon-gamma-inducible MHC2TA gene as well as the interferon-alpha-inducible G1P3 gene. Further investigation revealed that actin and RNA polymerase II co-localize in vivo and also co-purify. We employed an in vitro system with purified nuclear components to demonstrate that antibodies to beta-actin block the initiation of transcription. This assay also demonstrates that beta-actin stimulates transcription by RNA polymerase II. Finally, DNA-binding experiments established the presence of beta-actin in pre-initiation complexes and also showed that the depletion of actin prevented the formation of pre-initiation complexes. Together, these data suggest a fundamental role for actin in the initiation of transcription by RNA polymerase II.
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Affiliation(s)
- Wilma A Hofmann
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL 60612, USA
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33
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Shepard RN, Ornelles DA. Diverse roles for E4orf3 at late times of infection revealed in an E1B 55-kilodalton protein mutant background. J Virol 2004; 78:9924-35. [PMID: 15331726 PMCID: PMC515017 DOI: 10.1128/jvi.78.18.9924-9935.2004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2003] [Accepted: 05/15/2004] [Indexed: 11/20/2022] Open
Abstract
Species C human adenovirus mutants that fail to express open reading frame 3 of early region 4 (E4orf3) are phenotypically indistinguishable from the wild-type virus when evaluated in cells cultured in vitro. However, E4orf3 gene function has been productively studied in the context of additional viral mutations. This study identifies diverse roles for the E4orf3 protein that are evident in the absence of early region 1B 55-kDa protein (E1B-55K) function. In an E1B-55K-deficient background, the E4orf3 protein promotes viral replication by increasing both the burst size and the probability that an infected cell will produce virus. Early viral gene expression is not impaired in E1B-55K/E4orf3 double mutant virus-infected cells. Cells infected with the double mutant virus accumulated concatemers of viral DNA. However, the E1B-55K/E4orf3 double mutant virus did not replicate any better in MO59J cells, in which viral DNA concatemers did not accumulate, than in MO59K cells, in which viral DNA concatemers were produced, suggesting that viral DNA concatenation is not the primary growth defect of the E1B-55K/E4orf3 double mutant virus. Accumulation of viral mRNA in the nucleus and cytoplasm of E1B-55K/E4orf3 double mutant virus-infected cells was severely reduced compared to that on wild-type virus-infected cells. Thus, in an E1B-55K mutant background, the E4orf3 protein promotes the accumulation of late viral RNA and enhances late gene expression. Finally, within the context of an E1B-55K mutant virus, the E4orf3 protein acts to suppress host cell translation and preserve the viability of cells at moderately late times of infection.
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Affiliation(s)
- Robin N Shepard
- Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1064.
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34
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Zodrow JM, Stegeman JJ, Tanguay RL. Histological analysis of acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in zebrafish. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2004; 66:25-38. [PMID: 14687977 DOI: 10.1016/j.aquatox.2003.07.002] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Previous studies have demonstrated that acute exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) by injection leads to inhibition of caudal fin regeneration in zebrafish. Since the TCDD exposure in these studies is systemic, it is possible that pathology in organs other than the fin could result in inhibition of fin regeneration. Therefore, histopathology of adult zebrafish (Danio rerio) organs was characterized following abdominal cavity injection of a TCDD dose (70ng/g). The most pronounced histopathologic changes 5 days post-injection included lipidosis and hypertrophy of liver hepatocytes and hypertrophy of gill lamellae. Effects of TCDD exposure on immunolocalization of the zebrafish aryl hydrocarbon receptor nuclear translocator (ARNT2), the heterodimer partner of the aryl hydrocarbon receptor (AHR2), and an AHR regulated gene cytochrome P450 1A (CYP1A) was also determined. ARNT2 was immunolocalized to the gastrointestinal tract, gill lamellae, kidney, ventricle of the heart, caudal fin, brain and liver of zebrafish. TCDD exposure had no measurable effect on ARNT2 abundance or localization. CYP1A was immunolocalized in TCDD exposed fish as a biomarker for cells with an activated AHR pathway. CYP1A was not detected in any tissue from vehicle exposed fish. Significant TCDD-dependent induction of CYP1A was detected in the proximal tubules of the kidney, in liver hepatocytes and in the gastrointestinal tract of TCDD exposed fish. Significant but lower TCDD-dependent CYP1A expression was evident in the gill, caudal fin and ventricle of the heart. Overall, TCDD exposure in adult zebrafish leads to histopathology similar to that reported in other fish species, and it appears unlikely that the histopathology in these organs completely explains the inhibition of fin regeneration.
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Affiliation(s)
- Jeanmarie M Zodrow
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver 80262, USA
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35
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Hinz B, Gabbiani G, Chaponnier C. The NH2-terminal peptide of alpha-smooth muscle actin inhibits force generation by the myofibroblast in vitro and in vivo. J Cell Biol 2002; 157:657-63. [PMID: 11994316 PMCID: PMC2173846 DOI: 10.1083/jcb.200201049] [Citation(s) in RCA: 188] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Myofibroblasts are specialized fibroblasts responsible for granulation tissue contraction and the soft tissue retractions occurring during fibrocontractive diseases. The marker of fibroblast-myofibroblast modulation is the neo expression of alpha-smooth muscle actin (alpha-SMA), the actin isoform typical of vascular smooth muscle cells that has been suggested to play an important role in myofibroblast force generation. Actin isoforms differ slightly in their NH2-terminal sequences; these conserved differences suggest different functions. When the NH2-terminal sequence of alpha-SMA Ac-EEED is delivered to cultured myofibroblast in the form of a fusion peptide (FP) with a cell penetrating sequence, it inhibits their contractile activity; moreover, upon topical administration in vivo it inhibits the contraction of rat wound granulation tissue. The NH2-terminal peptide of alpha-skeletal actin has no effect on myofibroblasts, whereas the NH2-terminal peptide of beta-cytoplasmic actin abolishes the immunofluorescence staining for this isoform without influencing alpha-SMA distribution and cell contraction. The FPs represent a new tool to better understand the specific functions of actin isoforms. Our findings support the crucial role of alpha-SMA in wound contraction. The alpha-SMA-FP will be useful for the understanding of the mechanisms of connective tissue remodeling; moreover, it furnishes the basis for a cytoskeleton-dependent preventive and/or therapeutic strategy for fibrocontractive pathological situations.
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Affiliation(s)
- Boris Hinz
- Department of Pathology, Centre Médical Universitaire, University of Geneva, 1211 Geneva 4, Switzerland
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36
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Abstract
To investigate the precise localization of cytoplasmic gamma actin in skeletal muscle and the relationship to dystrophin molecules, we designed an antibody against the N-terminal peptide of cytoplasmic gamma actin. Western blot analysis using SDS-PAGE and isoelectric focusing (IEF) gel revealed that the antibody reacted only with the actin isoforms having gamma motility, confirming that the antibody is specific to the cytoplasmic (nonmuscle) gamma actin. Immunohistochemical analysis of the skeletal muscle of the adult mouse revealed a dot-like staining pattern of the antibody in transverse sections and a striated staining pattern in longitudinal sections. The double immunostaining technique revealed the colocalization of cytoplasmic gamma actin with alpha-actinin, implying the localization of the actin on the Z-disc. Contrary to previous findings (1), we did not detect the colocalization of cytochrome oxidase, a mitochondria marker, with this actin.
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Affiliation(s)
- T Nakata
- Department of Anatomy, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan.
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37
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Tumor necrosis factor alpha induces a metalloprotease-disintegrin, ADAM8 (CD 156): implications for neuron-glia interactions during neurodegeneration. J Neurosci 2001. [PMID: 11050116 DOI: 10.1523/jneurosci.20-21-07964.2000] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
ADAM proteases, defined by extracellular disintegrin and metalloprotease domains, are involved in protein processing and cell-cell interactions. Using wobbler (WR) mutant mice, we investigated the role of ADAMs in neurodegeneration and reactive glia activation in the CNS. We found that ADAM8 (CD 156), a suspected leukocyte adhesion molecule, is expressed in the CNS and highly induced in affected CNS areas of WR mice, in brainstem and spinal cord. ADAM8 mRNA and protein are found at low levels throughout the normal mouse CNS, in neurons and oligodendrocytes. In the WR CNS regions in which neurodegeneration occurs, ADAM8 is induced in neurons, reactive astrocytes, and activated microglia. Similarly, the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) is upregulated and shows the same cellular distribution. In primary astrocytes from wild-type and WR mice, in primary cerebellar neurons, and in mouse motoneuron-like NSC19 cells, ADAM8 expression was induced up to 15-fold by mouse TNF-alpha, in a dose-dependent manner. In both cell types, ADAM8 was also induced by human TNF-alpha, indicating that TNF receptor type I (p55) is involved. Induction of ADAM8 mRNA was suppressed by treatment with an interferon-regulating factor 1 (IRF-1) antisense oligonucleotide. We conclude that IRF-1-mediated induction of ADAM8 by TNF-alpha is a signaling pathway relevant for neurodegenerative disorders with glia activation, proposing a role for ADAM8 in cell adhesion during neurodegeneration.
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Abstract
We purified actin from bovine brain by DNase I affinity chromatography in order to compare the binding of dystrophin to muscle actin with its binding to nonmuscle actin. While both beta- and gamma-nonmuscle actins are expressed in brain, Western blot analysis with isoform-specific antibodies indicated that our purified brain actin was exclusively the gamma-isoform. The recombinant amino-terminal, actin-binding domain of dystrophin bound to muscle and brain actin in a saturable manner (approximately 1 mol/mol actin) with similar Kd values of 13.7+/-3.5 and 10.6+/-3.7 microM, respectively. We further demonstrate that intact dystrophin in the dystrophin-glycoprotein complex bound with equal avidity to muscle and brain F-actin. These data argue that a preferential binding of dystrophin to nonmuscle actin is not the basis for its targeting to the muscle cell plasmalemma but do support the hypothesis that dystrophin is capable of interacting with filamentous actin in nonmuscle tissues.
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Affiliation(s)
- B A Renley
- Department of Physiology, University of Wisconsin Medical School, Madison 53706, USA
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Adams JC, Clelland JD, Collett GD, Matsumura F, Yamashiro S, Zhang L. Cell-matrix adhesions differentially regulate fascin phosphorylation. Mol Biol Cell 1999; 10:4177-90. [PMID: 10588651 PMCID: PMC25751 DOI: 10.1091/mbc.10.12.4177] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cell adhesion to individual macromolecules of the extracellular matrix has dramatic effects on the subcellular localization of the actin-bundling protein fascin and on the ability of cells to form stable fascin microspikes. The actin-binding activity of fascin is down-regulated by phosphorylation, and we used two differentiated cell types, C2C12 skeletal myoblasts and LLC-PK1 kidney epithelial cells, to examine the hypothesis that cell adhesion to the matrix components fibronectin, laminin-1, and thrombospondin-1 differentially regulates fascin phosphorylation. In both cell types, treatment with the PKC activator 12-tetradecanoyl phorbol 13-acetate (TPA) or adhesion to fibronectin led to a diffuse distribution of fascin after 1 h. C2C12 cells contain the PKC family members alpha, gamma, and lambda, and PKCalpha localization was altered upon cell adhesion to fibronectin. Two-dimensional isoelectric focusing/SDS-polyacrylamide gels were used to determine that fascin became phosphorylated in cells adherent to fibronectin and was inhibited by the PKC inhibitors calphostin C and chelerythrine chloride. Phosphorylation of fascin was not detected in cells adherent to thrombospondin-1 or to laminin-1. LLC-PK1 cells expressing green fluorescent protein (GFP)-fascin also displayed similar regulation of fascin phosphorylation. LLC-PK1 cells expressing GFP-fascin S39A, a nonphosphorylatable mutant, did not undergo spreading and focal contact organization on fibronectin, whereas cells expressing a GFP-fascin S39D mutant with constitutive negative charge spread more extensively than wild-type cells. In contrast, C2C12 cells coexpressing S39A fascin with endogenous fascin remained competent to form microspikes on thrombospondin-1, and cells that expressed fascin S39D attached to thrombospondin-1 but did not form microspikes. Blockade of PKCalpha activity by TPA-induced down-regulation led to actin association of wild-type fascin in fibronectin-adherent C2C12 and LLC-PK1 cells but did not alter the distribution of S39A or S39D fascins. The association of fascin with actin in fibronectin-adherent cells was also evident in the presence of an inhibitory antibody to integrin alpha5 subunit. These novel results establish matrix-initiated PKC-dependent regulation of fascin phosphorylation at serine 39 as a mechanism whereby matrix adhesion is coupled to the organization of cytoskeletal structure.
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Affiliation(s)
- J C Adams
- Medical Research Council-Laboratory for Molecular Cell Biology and Department of Biochemistry and Molecular Biology, University College London, London WC1E 6BT, United Kingdom.
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40
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Clément S, Chaponnier C, Gabbiani G. A subpopulation of cardiomyocytes expressing alpha-skeletal actin is identified by a specific polyclonal antibody. Circ Res 1999; 85:e51-8. [PMID: 10559147 DOI: 10.1161/01.res.85.10.e51] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The NH(2)-terminal decapeptide of alpha-skeletal actin that contains a primary sequence specific for this isoform was used to raise a polyclonal antibody in rabbits. Using sequential affinity chromatography, we recovered from serum antibodies reacting exclusively with alpha-skeletal actin when tested by immunoblotting and immunofluorescence. Epitope mapping by means of competition assays with synthetic peptides indicated that the acetyl group and the first 9 amino acids are essential for specificity. The monospecific antibody was then used to investigate the distribution of alpha-skeletal actin in the myocardium of newborn and normal or hypertensive (with or without fibrotic areas) adult rats. Immunostaining of normal heart revealed that alpha-skeletal actin is diffusely distributed within practically all myocardial fibers of the newborn rat, whereas it is restricted to a small proportion of adult rat cardiomyocytes, which appear intensely stained. A correlation, albeit not complete, was found between the distribution of alpha-skeletal actin and beta-myosin heavy chain. During cardiac hypertrophy induced by aortic ligature between the renal arteries, the expressions of alpha-skeletal actin mRNA and protein were increased. The distribution of immunostaining had a focal pattern similar to that of normal adult rats, reactive fibers being more numerous and more intensely stained compared with normal myocardium. Positive fibers were particularly abundant at the periphery of fibrotic areas. Using this antibody, we have demonstrated for the first time the differential distribution of alpha-skeletal actin in heart tissues. Changes in the distribution of this isoform in hypertrophic heart provide new insight into the mechanisms by which the heart adapts to work overload. This antibody will prove useful in exploring the mechanisms of expression of alpha-skeletal actin and in defining its role in physiological and pathological situations.
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Affiliation(s)
- S Clément
- Department of Pathology, University of Geneva-CMU, Geneva, Switzerland
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41
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Brault V, Reedy MC, Sauder U, Kammerer RA, Aebi U, Schoenenberger C. Substitution of flight muscle-specific actin by human (beta)-cytoplasmic actin in the indirect flight muscle of Drosophila. J Cell Sci 1999; 112 ( Pt 21):3627-39. [PMID: 10523499 DOI: 10.1242/jcs.112.21.3627] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human (beta)-cytoplasmic actin differs by only 15 amino acids from Act88F actin which is the only actin expressed in the indirect flight muscle (IFM) of Drosophila melanogaster. To test the structural and functional significance of this difference, we ectopically expressed (beta)-cytoplasmic actin in the IFM of Drosophila that lack endogenous Act88F. When expression of the heterologous actin was regulated by approximately 1.5 kb of the 5′ promoter region of the Act88F gene, little (beta)-cytoplasmic actin accumulated in the IFM of the flightless transformants. Including Act88F-specific 5′ and 3′ untranslated regions (UTRs) yielded transformants that expressed wild-type amounts of (beta)-cytoplasmic actin. Despite the assembly of (beta)-cytoplasmic actin containing thin filaments to which endogenous myosin crossbridges attached, sarcomere organization was deficient, leaving the transformants flightless. Rather than affecting primarily actin-myosin interactions, our findings suggest that the (beta)-cytoplasmic actin isoform is not competent to interact with other actin-binding proteins in the IFM that are involved in the organization of functional myofibrils.
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Affiliation(s)
- V Brault
- M.E. Müller Institute, Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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Schüler H, Korenbaum E, Schutt CE, Lindberg U, Karlsson R. Mutational analysis of Ser14 and Asp157 in the nucleotide-binding site of beta-actin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 265:210-20. [PMID: 10491176 DOI: 10.1046/j.1432-1327.1999.00716.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This paper compares wild-type and two mutant beta-actins, one in which Ser14 was replaced by a cysteine, and a second in which both Ser14 and Asp157 were exchanged (Ser14-->Cys and Ser14-->Cys, Asp157-->Ala, respectively). Both of these residues are part of invariant sequences in the loops, which bind the ATP phosphates, in the interdomain cleft of actin. The increased nucleotide exchange rate, and the decreased thermal stability and affinity for DNase I seen with the mutant actins indicated that the mutations disturbed the interdomain coupling. Despite this, the two mutant actins retained their ATPase activity. In fact, the mutated actins expressed a significant ATPase activity even in the presence of Ca2+ ions, conditions under which actin normally has a very low ATPase activity. In the presence of Mg2+ ions, the ATPase activity of actin was decreased slightly by the mutations. The mutant actins polymerized as the wild-type protein in the presence of Mg2+ ions, but slower than the wild-type in a K+/Ca2+ milieu. Profilin affected the lag phases and elongation rates during polymerization of the mutant and wild-type actins to the same extent, whereas at steady-state, the concentration of unpolymerized mutant actin appeared to be elevated. Decoration of mutant actin filaments with myosin subfragment 1 appeared to be normal, as did their movement in the low-load motility assay system. Our results show that Ser14 and Asp157 are key residues for interdomain communication, and that hydroxyl and carboxyl groups in positions 14 and 157, respectively, are not necessary for ATP hydrolysis in actin.
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Affiliation(s)
- H Schüler
- Department of Cell Science, The Wenner-Gren Institute, Stockholm University, Sweden
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43
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Abstract
The actin cytoskeleton is a dynamic filamentous network whose formation and remodeling underlies the fundamental processes of cell motility and shape determination. To serve these roles, different compartments of the actin cytoskeleton engage in forming specific coupling sites between neighbouring cells and with the underlying matrix, which themselves serve signal transducing functions. In this review, we focus on methods used to visualise the actin cytoskeleton and its dynamics, embracing the use of proteins tagged with conventional fluorophores and green fluorescent protein. Included also is a comparison of cooled CCD technology, confocal and 2-photon fluorescence microscopy of living and fixed cells, as well as a critique of current procedures for electron microscopy.
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Affiliation(s)
- J Small
- Institute of Molecular Biology, Austrian Academy of Sciences, Salzburg, Austria.
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Kraemer J, Schmitz F, Drenckhahn D. Cytoplasmic dynein and dynactin as likely candidates for microtubule-dependent apical targeting of pancreatic zymogen granules. Eur J Cell Biol 1999; 78:265-77. [PMID: 10350215 DOI: 10.1016/s0171-9335(99)80060-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The critical role of microtubules in vectorial delivery of post-Golgi carrier vesicles to the apical cell surface has been established for various polarized epithelial cell types. In the present study we used secretory granules of the rat and chicken pancreas, termed zymogen granules, as model system for apically bound post-Golgi carrier vesicles that underlie the regulated exocytotic pathway. We found that targeting of zymogen granules to the apical cell surface requires an intact microtubule system which contains its colchicine-resistant organizing center and, thus, the microtubular minus ends close to the apical membrane domain. Purified zymogen granules and their membranes were found to be associated with cytoplasmic dynein intermediate and heavy chain and to contain the major components of the dynein activator complex, dynactin, i.e. p150Glued, p62, p50, Arp1, and beta-actin. Kinesin heavy chain and the kinesin receptor, 160 kD kinectin, were not detected as components of zymogen granules. Immunofluorescence staining showed a zymogen granule-like distribution for dynein and dynactin (p150Glued, p62, p50, Arpl) in the apical cytoplasm, whereas kinesin and kinectin were largely concentrated in the basal half of the cells in a pattern similar to the distribution of calreticulin, a component of the endoplasmic reticulum. Secretory granules of non-polarized chromaffin cells of the bovine adrenal medulla, that are assumed to underlie microtubular plus end targeting from the Golgi apparatus to the cell periphery, were not found to be associated with dynein or dynactin. To our knowledge, this is the first demonstration of major components of the dynein-dynactin complex associated with the membrane of a biochemically and functionally well-defined organelle which is considered to underlie a vectorial minus end-driven microtubular transport critically involved in precise delivery of digestive enzymes to the apically located acinar lumen.
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Affiliation(s)
- J Kraemer
- Institute of Anatomy, Julius-Maximilians University, Würzburg, Germany
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Gonsior SM, Platz S, Buchmeier S, Scheer U, Jockusch BM, Hinssen H. Conformational difference between nuclear and cytoplasmic actin as detected by a monoclonal antibody. J Cell Sci 1999; 112 ( Pt 6):797-809. [PMID: 10036230 DOI: 10.1242/jcs.112.6.797] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Using a reconstituted complex of profilin and skeletal muscle actin as an antigen, we generated a monoclonal mouse antibody against actin, termed 2G2. As revealed by immunoblots of proteolytic actin fragments and by pepscan analysis, the antibody recognises a nonsequential epitope on actin which is located within three different regions of the sequence, consisting of aa131-139, aa155-169, and aa176-187. In the actin model derived from X-ray diffraction, these sequences lie spatially close together in the region of the nucleotide-binding cleft, but do not form a coherent patch. In immunoblots, 2G2 reacts with all SDS-denatured actin isoforms and with actins of many vertebrates. In contrast, its immunofluorescence reactivity is highly selective and fixation-dependent. In fibroblasts and myogenic cells, fixed and extracted by formaldehyde/detergent, stress fibres or myofibrils, respectively, remained unstained. Likewise, after microinjection into living cells, 2G2 did not bind to such microfilament bundles. Extraction of myosin and tropomyosin did not alter this pattern indicating that the lack in reactivity is probably not due to epitope-masking by actin-binding proteins. More likely, the reason for the lack of reactivity with filamentous actin is that its epitope is not accessible in F-actin. However, the antibody revealed a distinct pattern of nuclear dots in differentiated myogenic cells but not in myoblasts, and of fibrillar structures in nuclei of Xenopus oocytes. In contrast, after methanol treatment, a 2G2-specific staining of stress fibres and myofibrils was observed, but no nuclear dot staining. We conclude that 2G2, in addition to binding to SDS- and methanol-denatured actin, recognises a specific conformation of native actin which is present in the nucleus and specified by compaction of the antibody-reactive region into a coherent patch. This conformation is apparently present in differentiated myogenic cells and oocytes, but not in cytoplasmic actin filament bundles.
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Affiliation(s)
- S M Gonsior
- Biochemical Cell Biology, University of Bielefeld, D-33501 Bielefeld, FRG
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Brault V, Sauder U, Reedy MC, Aebi U, Schoenenberger CA. Differential epitope tagging of actin in transformed Drosophila produces distinct effects on myofibril assembly and function of the indirect flight muscle. Mol Biol Cell 1999; 10:135-49. [PMID: 9880332 PMCID: PMC25159 DOI: 10.1091/mbc.10.1.135] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We have tested the impact of tags on the structure and function of indirect flight muscle (IFM)-specific Act88F actin by transforming mutant Drosophila melanogaster, which do not express endogenous actin in their IFMs, with tagged Act88F constructs. Epitope tagging is often the method of choice to monitor the fate of a protein when a specific antibody is not available. Studies addressing the functional significance of the closely related actin isoforms rely almost exclusively on tagged exogenous actin, because only few antibodies exist that can discriminate between isoforms. Thereby it is widely presumed that the tag does not significantly interfere with protein function. However, in most studies the tagged actin is expressed in a background of endogenous actin and, as a rule, represents only a minor fraction of the total actin. The Act88F gene encodes the only Drosophila actin isoform exclusively expressed in the highly ordered IFM. Null mutations in this gene do not affect viability, but phenotypic effects in transformants can be directly attributed to the transgene. Transgenic flies that express Act88F with either a 6x histidine tag or an 11-residue peptide derived from vesicular stomatitis virus G protein at the C terminus were flightless. Overall, the ultrastructure of the IFM resembled that of the Act88F null mutant, and only low amounts of C-terminally tagged actins were found. In contrast, expression of N-terminally tagged Act88F at amounts comparable with that of wild-type flies yielded fairly normal-looking myofibrils and partially reconstituted flight ability in the transformants. Our findings suggest that the N terminus of actin is less sensitive to modifications than the C terminus, because it can be tagged and still polymerize into functional thin filaments.
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Affiliation(s)
- V Brault
- M.E. Müller Institute, Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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Micheva KD, Vallée A, Beaulieu C, Herman IM, Leclerc N. beta-Actin is confined to structures having high capacity of remodelling in developing and adult rat cerebellum. Eur J Neurosci 1998; 10:3785-98. [PMID: 9875357 DOI: 10.1046/j.1460-9568.1998.00391.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neurons undergo complex morphological changes during differentiation and in cases of plasticity. A major determinant of cell morphology is the actin cytoskeleton, which in neurons is comprised of two actin isoforms, non-muscle gamma- and beta-actin. To better understand their respective roles during differentiation and plasticity, their cellular and subcellular localization was examined in developing and adult cerebellar cortex. It was observed that gamma-actin is expressed at a constant level throughout development, while the level of beta-actin expression rapidly decreases with age. At the light microscopic level, gamma-actin staining is ubiquitous and the only developmental change observed is a relative reduction of its concentration in cell bodies and white matter. In contrast, beta-actin staining almost completely disappears from the cytoplasm of cell bodies, primary dendrites and axons. In young cerebellar cultures, gamma-actin is found in the cell body, neurites and growth cones, while beta-actin is mainly found in growth cones, as previously reported in other primary neuronal culture systems [Kaech et al. (1997), J. Neuroscience, 17, 9565-9572; Bassell et al., (1998), J. Neuroscience, 18, 251-265]. Electron microscopy of post-embedding immunogold-labelled tissue confirms the widespread distribution of gamma-actin, and also reveals an increased concentration of gamma-actin in dendritic spines in the adult. During development, beta-actin accumulation is observed in actively growing structures, e.g., growth cones, filopodia, cell bodies and axonal tracts. In the adult cerebellar cortex, beta-actin is preferentially found in dendritic spines, structures which are known to retain their capacity for morphological modifications in the adult brain. This differential subcellular localization and developmental regulation of the two actin isoforms point to their different roles in neurons.
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Affiliation(s)
- K D Micheva
- Département de Pathologie et Biologie Cellulaire, Université de Montréal, Québec, Canada
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Plantier M, Der Terrossian E, Represa A. Beta-actin immunoreactivity in rat microglial cells: developmental pattern and participation in microglial reaction after kainate injury. Neurosci Lett 1998; 247:49-52. [PMID: 9637407 DOI: 10.1016/s0304-3940(98)00280-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In the present study we investigated the developmental and post-injury pattern of beta-actin immunoreactivity in rat brain. Our data suggest that beta-actin is higher in microglia-macrophages than in any other central nervous system cell type, including neurons and astrocytes. We also show that beta-actin immunoreactivity is particularly high in ameboid-macrophagic cells, suggesting a role on the plastic changes that these cells experience during maturation or after activation.
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Affiliation(s)
- M Plantier
- Université René Descartes (Paris V) and INSERM U29, France
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49
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Gimona M, Lando Z, Dolginov Y, Vandekerckhove J, Kobayashi R, Sobieszek A, Helfman DM. Ca2+-dependent interaction of S100A2 with muscle and nonmuscle tropomyosins. J Cell Sci 1997; 110 ( Pt 5):611-21. [PMID: 9092943 DOI: 10.1242/jcs.110.5.611] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Zero-length chemical crosslinking with 1-ethyl-3-[3-(dimethyl amino)propyl]carbodiimide (EDC) indicated an association of the Ca2+-binding protein S100A2 with tropomyosin (TM) in vitro. The mobility of the crosslinked product on SDS-PAGE gels indicated the formation of a 1:1 complex between S100A2 and TM and the interaction was Ca2+ dependent. Monoclonal antibodies were raised against S100A2 and used to determine its cellular localization in the porcine epithelial cell line LLC PK1. It was found that the localization of S100A2 depended on the differentiation state of the cells, being absent from actin stress fibers in sparsely seeded cultures, but present in the actin-containing microvilli characteristic of differentiated cells. Immunoprecipitations of [35S]methionine-labeled extracts using S100A2 as well as TM-specific antibodies failed to co-precipitate TM and S100A2, indicating a transient association between these two molecules in solution. Affinity chromatography of cell extracts on immobilized recombinant TMs, however, confirmed the Ca2+-dependent interaction between S100A2 and both muscle TMs as well as with high and low molecular mass nonmuscle TMs, suggesting that the binding site resides in one of the conserved regions of TM. Our data demonstrate the possible interaction of S100A2 with TM that is not bound to the microfilaments and indicate a differentiation-related function for S100A2 in LLC PK1 cells. The possible functional implications of this interaction are discussed.
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Affiliation(s)
- M Gimona
- Cold Spring Harbor Laboratory, NY 11724, USA
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Rovere P, Trucy J, Zimmermann VS, Granjeaud S, Rocha D, Nguyen C, Ricciardi-Castagnoli P, Jordan BR, Davoust J. Differential mRNA expression in untreated and TNF-alpha elicited murine dendritic cells precursors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1997; 417:467-73. [PMID: 9286405 DOI: 10.1007/978-1-4757-9966-8_77] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have compared the pattern of gene expression in long term cultured precursor dendritic cells (DC), either untreated (immature) or cultured for two days in the presence of recombinant murine (rm)-TNF alpha (mature). The hybridization signature of complex cDNA probes prepared from total RNA extracted from immature and mature DC were analyzed using a mouse thymic cDNA library, gridded on high density filters. For each clone spotted on the filters, we have measured using an imaging plate device the hybridization signals of the complex probe obtained from immature or mature DC. Comparative analysis of these values allowed us to identify differentially expressed gene products. Our goal is to identify a new set of genes induced or repressed during DC maturation elicited by rmTNF alpha treatment.
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Affiliation(s)
- P Rovere
- Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, Marseille, France
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