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Mensah-Nyagan AG, Meyer L, Patte-Mensah C. Modulatory role of neurosteroidogenesis in the spinal cord during peripheral nerve injury-induced chronic pain. Front Neuroendocrinol 2024; 72:101116. [PMID: 38182090 DOI: 10.1016/j.yfrne.2023.101116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 12/14/2023] [Accepted: 12/31/2023] [Indexed: 01/07/2024]
Abstract
The brain and spinal cord (SC) are both targeted by various hormones, including steroid hormones. However, investigations of the modulatory role of hormones on neurobiological functions usually focus only on the brain. The SC received little attention although this structure pivotally controls motor and sensory functions. Here, we critically reviewed key data showing that the process of neurosteroid biosynthesis or neurosteroidogenesis occurring in the SC plays a pivotal role in the modulation of peripheral nerve injury-induced chronic pain (PNICP) or neuropathic pain. Indeed, several active steroidogenic enzymes expressed in the SC produce endogenous neurosteroids that interact with receptors of neurotransmitters controlling pain. The spinal neurosteroidogenesis is differentially regulated during PNICP condition and its blockade modifies painful sensations. The paper suggests that future investigations aiming to develop effective strategies against PNICP or neuropathic pain must integrate in a gender or sex dependent manner the regulatory effects exerted by spinal neurosteroidogenesis.
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Affiliation(s)
- Ayikoe-Guy Mensah-Nyagan
- Biopathologie de la Myéline, Neuroprotection et Stratégies Thérapeutiques, INSERM U1119, Université de Strasbourg, Fédération de Médecine Translationnelle de Strasbourg (FMTS), Bâtiment CRBS de la Faculté de Médecine, 1 rue Eugène Boeckel, 67 000 Strasbourg, France.
| | - Laurence Meyer
- Biopathologie de la Myéline, Neuroprotection et Stratégies Thérapeutiques, INSERM U1119, Université de Strasbourg, Fédération de Médecine Translationnelle de Strasbourg (FMTS), Bâtiment CRBS de la Faculté de Médecine, 1 rue Eugène Boeckel, 67 000 Strasbourg, France
| | - Christine Patte-Mensah
- Biopathologie de la Myéline, Neuroprotection et Stratégies Thérapeutiques, INSERM U1119, Université de Strasbourg, Fédération de Médecine Translationnelle de Strasbourg (FMTS), Bâtiment CRBS de la Faculté de Médecine, 1 rue Eugène Boeckel, 67 000 Strasbourg, France
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Wood TR, Parikh P, Comstock BA, Law JB, Bammler TK, Kuban KC, Mayock DE, Heagerty PJ, Juul S. Early Biomarkers of Hypoxia and Inflammation and Two-Year Neurodevelopmental Outcomes in the Preterm Erythropoietin Neuroprotection (PENUT) Trial. EBioMedicine 2021; 72:103605. [PMID: 34619638 PMCID: PMC8498235 DOI: 10.1016/j.ebiom.2021.103605] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 08/24/2021] [Accepted: 09/16/2021] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND In the Preterm Erythropoietin (Epo) NeUroproTection (PENUT) Trial, potential biomarkers of neurological injury were measured to determine their association with outcomes at two years of age and whether Epo treatment decreased markers of inflammation in extremely preterm (<28 weeks' gestation) infants. METHODS Plasma Epo was measured (n=391 Epo, n=384 placebo) within 24h after birth (baseline), 30min after study drug administration (day 7), 30min before study drug (day 9), and on day 14. A subset of infants (n=113 Epo, n=107 placebo) had interferon-gamma (IFN-γ), Interleukin (IL)-6, IL-8, IL-10, Tau, and tumour necrosis factor-α (TNF-α) levels evaluated at baseline, day 7 and 14. Infants were then evaluated at 2 years using the Bayley Scales of Infant and Toddler Development, 3rd Edition (BSID-III). FINDINGS Elevated baseline Epo was associated with increased risk of death or severe disability (BSID-III Motor and Cognitive subscales <70 or severe cerebral palsy). No difference in other biomarkers were seen between treatment groups at any time, though Epo appeared to mitigate the association between elevated baseline IL-6 and lower BSID-III scores in survivors. Elevated baseline, day 7 and 14 Tau concentrations were associated with worse BSID-III Cognitive, Motor, and Language skills at two years. INTERPRETATION Elevated Epo at baseline and elevated Tau in the first two weeks after birth predict poor outcomes in infants born extremely preterm. However, no clear prognostic cut-off values are apparent, and further work is required before these biomarkers can be widely implemented in clinical practice. FUNDING PENUT was funded by the National Institute of Neurological Disorders and Stroke (U01NS077955 and U01NS077953).
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Affiliation(s)
- Thomas R. Wood
- Division of Neonatology, Department of Pediatrics, University of Washington, Seattle, WA
| | - Pratik Parikh
- Division of Neonatology, Department of Pediatrics, University of Washington, Seattle, WA
| | | | - Janessa B. Law
- Division of Neonatology, Department of Pediatrics, University of Washington, Seattle, WA
| | - Theo K. Bammler
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA
| | - Karl C. Kuban
- Department of Pediatrics, Boston University School of Medicine, Boston, MA
| | - Dennis E. Mayock
- Division of Neonatology, Department of Pediatrics, University of Washington, Seattle, WA
| | | | - Sandra Juul
- Division of Neonatology, Department of Pediatrics, University of Washington, Seattle, WA
| | - for the PENUT Trial consortium
- Division of Neonatology, Department of Pediatrics, University of Washington, Seattle, WA
- Department of Biostatistics, University of Washington, Seattle, WA
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA
- Department of Pediatrics, Boston University School of Medicine, Boston, MA
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Abstract
Mutations causing dysfunction of the tubulins and microtubule-associated proteins, otherwise known as tubulinopathies, are a group of recently described entities, that lead to complex brain malformations. An understanding of the fundamental principles of operation of the cytoskeleton and compounds in particular microtubules, actin, and microtubule-associated proteins, can assist in the interpretation of the imaging findings of tubulinopathies. Somewhat consistent morphological imaging patterns have been described in tubulinopathies such as dysmorphic basal ganglia-the hallmark (found in 75% of cases), callosal dysgenesis, cerebellar hypoplasia/dysplasia, and cortical malformations, most notably lissencephaly. Recognizing the common imaging phenotypes present in tubulinopathies can prove invaluable in directing the genetic workup for a patient with brain malformations.
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Patte-Mensah C, Meyer L, Mensah-Nyagan AG. Steroids, spinal cord and pain sensation. Horm Mol Biol Clin Investig 2011; 7:377-84. [DOI: 10.1515/hmbci.2011.119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 08/02/2011] [Indexed: 11/15/2022]
Abstract
AbstractDuring the whole life, the nervous system is continuously submitted to the actions of different categories of hormones, including steroids. Therefore, the interactions between hormonal compounds and neural tissues are subjected to intense investigations. While a majority of studies focus on the brain, the spinal cord (SC) has received little attention, although this structure is also an important part of the central nervous system, controlling motor and sensory functions. To point out the importance of interactions between hormones and the SC in the regulation of neurobiological activities, we recapitulated and discussed herein various key data, revealing that the pivotal role played by the SC in nociception and pain modulation, directly depends on the SC ability to metabolize and synthesize steroidal molecules. The paper suggests that future investigations aiming to develop effective strategies against chronic pain, must integrate regulatory effects exerted by hormonal steroids on the SC activity, as well as the actions of endogenous neurosteroids locally synthesized in spinal neural networks.
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Mensah-Nyagan AG, Kibaly C, Schaeffer V, Venard C, Meyer L, Patte-Mensah C. Endogenous steroid production in the spinal cord and potential involvement in neuropathic pain modulation. J Steroid Biochem Mol Biol 2008; 109:286-93. [PMID: 18434133 DOI: 10.1016/j.jsbmb.2008.03.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
It has recently been demonstrated that the spinal cord (SC) is an active production center of neuroactive steroids including pregnenolone, dehydroepiandrosterone, progesterone and allopregnanolone. Indeed, anatomical, cellular and biochemical investigations have shown that the SC dorsal horn (DH), a pivotal structure in nociception, contains various active steroidogenic enzymes such as cytochrome P450side-chain-cleavage, cytochrome P450c17, 3beta-hydroxysteroid dehydrogenase, 5alpha-reductase and 3alpha-hydroxysteroid oxido-reductase. Reviewed here are several data obtained with in vitro and vivo experiments showing that endogenous steroids synthesized in the SC are involved in the modulation of nociceptive mechanisms. Various approaches were used as the real-time polymerase chain reaction after reverse transcription to determine the effects of neuropathic pain on the expression of genes encoding steroidogenic enzymes in the DH. Combination of the pulse-chase technique with high performance liquid chromatography and continuous flow scintillation detection allowed investigations of the impact of noxious signals on the activity of steroid-producing enzymes in the SC in vitro. Radioimmunological analyses of spinal tissue extracts contributed to determine the link between the painful state and endogenous steroid secretion in the SC in vivo. Finally, the physiological relevance of the modification of endogenous steroid formation in the SC during painful situation was discussed.
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Affiliation(s)
- A G Mensah-Nyagan
- Equipe Stéroïdes et Système Nociceptif, Institut des Neurosciences Cellulaires et Intégratives, Université Louis Pasteur, 67084 Strasbourg Cedex, France.
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Kibaly C, Patte-Mensah C, Mensah-Nyagan AG. Molecular and neurochemical evidence for the biosynthesis of dehydroepiandrosterone in the adult rat spinal cord. J Neurochem 2005; 93:1220-30. [PMID: 15934942 DOI: 10.1111/j.1471-4159.2005.03113.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Various studies have indicated that exogenous dehydroepiandrosterone (DHEA) modulates several mechanisms in the CNS of rodents. As adult rodent glands do not secrete significant amounts of DHEA, its role as endogenous modulator of the CNS remains possible only if DHEA is produced by nerve cells. Therefore, the last decade has been marked by diverse unsuccessful investigations aiming to demonstrate the activity of cytochrome P450c17 (P450c17), the key DHEA-synthesizing enzyme, in adult rodent CNS. Here, we combined molecular, anatomical, cellular and neurochemical approaches to provide the first demonstration of the existence of P450c17 and bioactivity in adult rat spinal cord (SC). Real-time RT-PCR revealed P450c17 gene expression in all SC segments. Western blot analyses allowed identification of a specific P450c17 protein in the SC and immunohistochemical studies localized P450c17 in neurones and glial cells. Pulse-chase experiments combined with HPLC and radioactive steroid detection showed that SC slices converted [3H]pregnenolone into [3H]DHEA, a conversion markedly reduced by ketoconazole, a P450c17 inhibitor. Kinetics studies revealed accumulation of [3H]DHEA newly synthesized by SC slices in the incubation medium as its amount declined slowly. This first cellular mapping of an active P450c17 in adult rodent SC suggests that endogenous DHEA synthesized in spinal neural networks may control various spinally-mediated activities.
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Affiliation(s)
- Cherkaouia Kibaly
- Laboratoire de Neurophysiologie Cellulaire et Intégrée, Unité Mixte de Recherche 7519-Centre National de la Recherche Scientifique, Université Louis Pasteur, Strasbourg, France
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Patte-Mensah C, Penning TM, Mensah-Nyagan AG. Anatomical and cellular localization of neuroactive 5?/3?-reduced steroid-synthesizing enzymes in the spinal cord. J Comp Neurol 2004; 477:286-99. [PMID: 15305365 DOI: 10.1002/cne.20251] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The complementary activities of 5 alpha-reductase (5 alpha-R) and 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) are crucial for the synthesis of neuroactive 5 alpha/3 alpha-reduced steroids, such as 3 alpha-androstanediol, allopregnanolone, and tetrahydrodeoxycorticosterone, which control several important neurophysiological mechanisms through allosteric modulation of gamma-aminobutyric acid type A receptors. Immunocytochemical localization of 3 alpha-HSD in the central nervous system (CNS) has never been determined. The presence and activity of 5 alpha-R have been investigated in the CNS, but only the brain was considered; the spinal cord (SC) received little attention, although this structure is crucial for many sensorimotor activities. We have determined the first cellular distribution of 5 alpha-reductase type 1 (5 alpha-R1) and type 2 (5 alpha-R2) and 3 alpha-HSD immunoreactivities in adult rat SC. 5 alpha-R1 immunostaining was detected mainly in the white matter (Wm). In contrast, intense 5 alpha-R2 labeling was observed in dorsal (DH) and ventral horns of gray matter (Gm). 3 alpha-HSD immunoreactivity was largely distributed in the Wm and Gm, but the highest density was found in sensory areas of the DH. Double-labeling experiments combined with confocal analysis revealed that, in the Wm, 5 alpha-R1 was localized in glial cells, whereas 35% of 5 alpha-R2 and 3 alpha-HSD immunoreactivities were found in neurons. In the DH, 60% of 5 alpha-R2 immunostaining colocalized with oligodendrocyte, 25% with neuron, and 15% with astrocyte markers. Similarly, 45% of 3 alpha-HSD immunoreactivity was found in oligodendrocytes, 35% in neurons, and 20% in astrocytes. These results are the first demonstrating that oligodendrocytes and neurons of the SC possess the key enzymatic complex for synthesizing potent neuroactive steroids that may control spinal sensorimotor processes.
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Affiliation(s)
- Christine Patte-Mensah
- Laboratoire de Neurophysiologie Cellulaire et Intégrée, Unité Mixte de Recherche 7519-Centre National de la Recherche Scientifique, Université Louis Pasteur, 67084 Strasbourg, France
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Patte-Mensah C, Kappes V, Freund-Mercier MJ, Tsutsui K, Mensah-Nyagan AG. Cellular distribution and bioactivity of the key steroidogenic enzyme, cytochrome P450side chain cleavage, in sensory neural pathways. J Neurochem 2003; 86:1233-46. [PMID: 12911631 DOI: 10.1046/j.1471-4159.2003.01935.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Neurosteroids are steroids produced within the nervous system. Based on behavioural responses evoked in animals by synthetic steroid injections, several studies suggested neurosteroid involvement in important neurophysiological processes. These observations should be correlated only to neuroactive effects of the injected steroids. Neurosteroids mostly control the CNS activity through allosteric modulation of neurotransmitter receptors within concentration ranges used by neurotransmitters themselves. Therefore, neurosteroid production within pathways controlling a neurophysiological process is necessary to consider neurosteroid involvement in that process. Because of the increasing speculation about pain modulation by neurosteroids based on pharmacological observations, we decided to clarify the situation by investigating neurosteroidogenesis occurrence in sensory pathways, particularly in nociceptive structures. We studied the presence and activity of cytochrome P450side chain cleavage (P450scc) in rat pain pathways. P450scc-immunoreactive cells were localized in dorsal root ganglia (DRG), spinal cord (SC) dorsal horn, nociceptive supraspinal nuclei (SSN) and somatosensory cortex. Incubation of DRG, SSN or SC tissue homogenates with [3H]cholesterol yielded the formation of radioactive metabolites including [3H]pregnenolone of which the synthesis was reduced in presence of aminogluthetimide, a P450scc inhibitor. These first neuroanatomical and neurochemical results demonstrate the occurrence of neurosteroidogenesis in nociceptive pathways and strongly suggest that neurosteroids may control pain mechanisms.
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Affiliation(s)
- Christine Patte-Mensah
- Laboratoire de Neurophysiologie Cellulaire et Intégrée, Unité Mixte de Recherche 7519-Centre National de la Recherche Scientifique, Université Louis Pasteur, 67084 Strasbourg Cedex, France
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Rapoport M, Dawson HN, Binder LI, Vitek MP, Ferreira A. Tau is essential to beta -amyloid-induced neurotoxicity. Proc Natl Acad Sci U S A 2002; 99:6364-9. [PMID: 11959919 PMCID: PMC122954 DOI: 10.1073/pnas.092136199] [Citation(s) in RCA: 596] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2001] [Accepted: 03/08/2002] [Indexed: 11/18/2022] Open
Abstract
Senile plaques and neurofibrillary tangles, the two hallmark lesions of Alzheimer's disease, are the results of the pathological deposition of proteins normally present throughout the brain. Senile plaques are extracellular deposits of fibrillar beta-amyloid peptide (Abeta); neurofibrillary tangles represent intracellular bundles of self-assembled hyperphosphorylated tau proteins. Although these two lesions are often present in the same brain areas, a mechanistic link between them has yet to be established. In the present study, we analyzed whether tau plays a key role in fibrillar Abeta-induced neurite degeneration in central neurons. Cultured hippocampal neurons obtained from wild-type, tau knockout, and human tau transgenic mice were treated with fibrillar Abeta. Morphological analysis indicated that neurons expressing either mouse or human tau proteins degenerated in the presence of Abeta. On the other hand, tau-depleted neurons showed no signs of degeneration in the presence of Abeta. These results provide direct evidence supporting a key role for tau in the mechanisms leading to Abeta-induced neurodegeneration in the central nervous system. In addition, the analysis of the composition of the cytoskeleton of tau-depleted neurons suggested that the formation of more dynamic microtubules might confer resistance to Abeta-mediated neurodegeneration.
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Affiliation(s)
- Mark Rapoport
- Institute for Neuroscience, Northwestern University, Chicago, IL 60611, USA
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Kalcheva N, Rockwood JM, Kress Y, Steiner A, Shafit-Zagardo B. Molecular and functional characteristics of MAP-2a: ability of MAP-2a versus MAP-2b to induce stable microtubules in COS cells. CELL MOTILITY AND THE CYTOSKELETON 2000; 40:272-85. [PMID: 9678670 DOI: 10.1002/(sici)1097-0169(1998)40:3<272::aid-cm6>3.0.co;2-f] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Microtubule-associated protein-2 (MAP-2) is a prominent cytoskeletal protein in the mammalian nervous system. Two high-molecular-weight (HMW) MAP-2 isoforms, MAP-2a and MAP-2b, are developmentally regulated. MAP-2b is expressed through the life of the neuron, while MAP-2a expression coincides with the time of synaptic formation. MAP-2a and MAP-2b differ in size by approximately 10 kD. Attempts to differentiate MAP-2a from MAP-2b led to the identification of additional exons; exons 7A, 8, 13, and 16. The focus of the present study was to define the complete molecular composition of MAP-2a that was prerequisite for investigating the functional characteristic of the MAP-2a protein. Detailed examination of rat brain mRNA by Northern blot analysis and RT-PCR showed that MAP-2a contains only exon 8 in addition to the exons found in the MAP-2b transcript. Exons 7A, 13, and 16 are not present in the MAP-2a transcript. Antibody generated to exon 8 expressed protein, immunoprecipitated a HMW protein from adult rat brain that co-migrated with MAP-2a and was immunopositive with other MAP-2 antibodies. Comparative transfections of full-length MAP-2a and MAP-2b cDNA into COS-7 cells demonstrated that MAP-2a influenced the microtubule network differently than MAP-2b by inducing rapid and stable microtubule bundle formation even in the presence of nocodazole.
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Affiliation(s)
- N Kalcheva
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Shafit-Zagardo B, Kress Y, Zhao ML, Lee SC. A novel microtubule-associated protein-2 expressed in oligodendrocytes in multiple sclerosis lesions. J Neurochem 1999; 73:2531-7. [PMID: 10582615 DOI: 10.1046/j.1471-4159.1999.0732531.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Elucidation of the mechanisms involved in the regeneration of oligodendrocytes and remyelination is a central issue in multiple sclerosis (MS) research. We recently identified a novel alternatively spliced, developmentally regulated oligodendrocyte-specific protein designated microtubule-associated protein-2+13 [microtubule-associated protein-2 expressing exon 13 (MAP-2+13)]. MAP-2+13 is expressed in human fetal oligodendrocytes during process extension and myelination but is minimally expressed in normal mature CNS. To test the hypothesis that MAP-2+13 is reexpressed in regenerating oligodendrocytes in MS lesions, we examined the brains of MS patients for the expression of this protein. By immunocytochemistry using a series of monoclonal antibodies specific for MAP-2+13, we determined that MAP-2+13 expression was up-regulated in all 31 lesions from 10 different MS brains. MAP-2+13 was expressed in regenerating oligodendrocytes associated with demyelinated lesions, with the highest counts found in regions of extensive remyelination. By electron microscopy, MAP-2+13 was localized to oligodendrocytes engaged in remyelination, evident by their process extension and association with thinly myelinated (remyelinated) and demyelinated axons. These results suggest a hitherto unsuspected role for this microtubule-associated protein in oligodendrocyte function during development and myelin repair.
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Affiliation(s)
- B Shafit-Zagardo
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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12
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Abstract
Xenopus oocytes contain a complex cytoskeleton composed of three filament systems: (1) microtubules, composed of tubulin and at least three different microtubule-associated proteins (XMAPs); (2) microfilaments composed of actin and associated proteins; and (3) intermediate filaments, composed of keratins. For the past several years, we have used confocal immunofluorescence microscopy to characterize the organization of the oocyte cytoskeleton throughout the course of oogenesis. Together with computer-assisted reconstruction of the oocyte in three dimensions, confocal microscopy gives an unprecedented view of the assembly and reorganization of the cytoskeleton during oocyte growth and differentiation. Results of these studies, combined with the effects of cytoskeletal inhibitors, suggest that organization of the cytoskeleton in Xenopus oocytes is dependent upon a hierarchy of interactions between microtubules, microfilaments, and keratin filaments. This article presents a gallery of confocal images and 3-D reconstructions depicting the assembly and organization of the oocyte cytoskeleton during stages 0-VI of oogenesis, a discussion of the mechanisms that might regulate cytoskeletal organization during oogenesis, and speculates on the potential roles of the oocyte cytoskeleton during oogenesis and axis formation.
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Affiliation(s)
- D L Gard
- Department of Biology, University of Utah, Salt Lake City 84112-0840, USA.
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Chapter 9 Microtubule organization in growth cones and their role in pathfinding. Dev Biol 1998. [DOI: 10.1016/s1569-2582(98)80024-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Nick P. Signaling to The Microtubular Cytoskeleton in Plants. INTERNATIONAL REVIEW OF CYTOLOGY 1998. [DOI: 10.1016/s0074-7696(08)62178-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Li YQ, Moscatelli A, Cai G, Cresti M. Functional interactions among cytoskeleton, membranes, and cell wall in the pollen tube of flowering plants. INTERNATIONAL REVIEW OF CYTOLOGY 1997; 176:133-99. [PMID: 9394919 DOI: 10.1016/s0074-7696(08)61610-1] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The pollen tube is a cellular system that plays a fundamental role during the process of fertilization in higher plants. Because it is so important, the pollen tube has been subjected to intensive studies with the aim of understanding its biology. The pollen tube represents a fascinating model for studying interactions between the internal cytoskeletal machinery, the membrane system, and the cell wall. These compartments, often studied as independent units, show several molecular interactions and can influence the structure and organization of each other. The way the cell wall is constructed, the dynamics of the endomembrane system, and functions of the cytoskeleton suggest that these compartments are a molecular "continuum," which represents a link between the extracellular environment and the pollen tube cytoplasm. Several experimental approaches have been used to understand how these interactions may translate the pollen-pistil interactions into differential processes of pollen tube growth.
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Affiliation(s)
- Y Q Li
- Dipartimento Biologia Ambientale, Università di Siena, Italy
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16
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Abstract
To understand the role of microtubule-associated proteins (MAPs) in the regulation of microtubule (MT) dynamics we have characterized MAPs prepared from Xenopus laevis eggs (Andersen, S.S.L., B. Buendia, J.E. Domínguez, A. Sawyer, and E. Karsenti. 1994. J. Cell Biol. 127:1289-1299). Here we report on the purification and characterization of a 310-kD MAP (XMAP310) that localizes to the nucleus in interphase and to mitotic spindle MTs in mitosis. XMAP310 is present in eggs, oocytes, a Xenopus tissue culture cell line, testis, and brain. We have purified XMAP310 to homogeneity from egg extracts. The purified protein cross-links pure MTs. Analysis of the effect of this protein on MT dynamics by time-lapse video microscopy has shown that it increases the rescue frequency 5-10-fold and decreases the shrinkage rate twofold. It has no effect on the growth rate or the catastrophe frequency. Microsequencing data suggest that XMAP230 and XMAP310 are novel MAPs. Although the three Xenopus MAPs characterized so far, XMAP215 (Vasquez, R.J., D.L. Gard, and L. Cassimeris. 1994. J. Cell Biol. 127:985-993), XMAP230, and XMAP310 are localized to the mitotic spindle, they have distinct effects on MT dynamics. While XMAP215 promotes rapid MT growth, XMAP230 decreases the catastrophe frequency and XMAP310 increases the rescue frequency. This may have important implications for the regulation of MT dynamics during spindle morphogenesis and chromosome segregation.
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Affiliation(s)
- S S Andersen
- European Molecular Biology Laboratory, Cell Biology Programme, D-69117 Heidelberg, Germany.
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Abstract
Mechanisms underlying axonogenesis remain obscure. Although a large number of proteins eventually become polarized to the axonal domain, in no case does protein compartmentalization occur before or simultaneous with the earliest morphological expression of axonal properties. How then might initially unpolarized proteins, such as the microtubule-associated protein tau, play a role in the microdifferentiation of axons? We hypothesized that tau function could be locally regulated by phosphorylation during the period of axonogenesis. To test this hypothesis, we mapped relative levels of tau phosphorylation within developing cultured hippocampal neurons. This was accomplished using calibrated immunofluorescence ratio measurements employing phosphorylation state-dependent and state-independent antibodies. Tau in the nascent axon is more highly dephosphorylated at the site recognized by the tau-1 antibody than tau in the somatodendritic compartment. The change in phosphorylation state from soma to axon takes the form of a smooth proximo-distal gradient, with tau in the soma, immature dendrites and proximal axon approximately 80% phosphorylated at the tau-1 site, and that in the axonal growth cone only 20% phosphorylated. The existence of real spatial differences in tau phosphorylation state was confirmed by in situ phosphatase and kinase treatment. Pervanadate, a tyrosine phosphatase inhibitor, induced rapid tau dephosphorylation within live cells, effectively abolishing the phosphorylation gradient. Thus, the gradient is dynamic and potentially regulatable by upstream signals involving tyrosine phosphorylation. Phosphorylation gradients are likely to be present on many neuronal proteins in addition to tau, and their modulation by transmembrane signals could direct the establishment of polarity.
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Stassen MP, Thole HH, Schaaf C, Marquart AU, Sinner K, Gehrig H. Chicken microtubule-associated protein 4 (MAP4): a novel member of the MAP4 family. Histochem Cell Biol 1996; 106:341-9. [PMID: 8897075 DOI: 10.1007/bf02473244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Chicken gizzard smooth muscle has often been used as a source of proteins of the contractile and cytoskeletal apparatus. In the present study, we isolated a hitherto unknown doublet of proteins, with apparent molecular weights of 200 kDa, from embryonic chicken gizzard and showed its association with the microtubules (MTs) and by immunofluorescence staining of cultured cells. Immunoblot analysis also revealed the ubiquitous expression of this protein in all embryonic chicken tissues examined. Molecular cloning techniques allowed its identification as the chicken homologue of the microtubule-associated protein 4 (MAP4), known from mammalian species, and revealed approximately 90% of its amino acid sequence. MAP4 is the major MAP of non-neuronal tissues and cross-species comparisons clearly demonstrated its highly conserved overall structure, consisting of a basic C-terminal MT-binding region and an acidic N-terminal projection domain of unknown function. Despite these conserved features, overall sequence homologies to its mammalian counterparts are rather low and focused to distinct regions of the molecule. Among these are a conserved 18-amino acid motif, which is known to mediate binding to MTs and a part of the MT-binding domain known as the proline-rich region, which is thought to be the regulatory domain of MAP4. The N-terminal 59 amino acids are a conserved and unique feature of the MAP4 sequence and might be an indication that MAP4 performs other functions besides the enhancement of MT assembly.
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Affiliation(s)
- M P Stassen
- Institut für Zoologie, Technische Hochschule Darmstadt, Germany
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Werner D, Hawrylak N, Comery TA, Karr TL, Greenough WT. Expression of DMAP-45R in the rat visual cortex is modulated by visual experience. Brain Res 1995; 701:55-60. [PMID: 8925299 DOI: 10.1016/0006-8993(95)00954-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Effects of visual experience upon expression of a developmentally regulated microtubule-associated protein (MAP) were studied in the visual cortex of monocularly deprived rats. The antibody Drosophila MAP-45 (DMAP-45) recognizes proteins in the developing ventral nerve cord of Drosophila and in rat brain. Monocular deprivation from day 12, before eye opening, to day 80 reduced the number of DMAP-45 immunoreactive layer V pyramidal cell apical dendrites in the monocular segment (Oc1M) of the visual cortex contralateral to the deprived eye. No significant visual deprivation effects were seen in the binocular segment (Oc1B). Immunoreactivity was restored to control levels in Oc1M of rats in which the monocular sutures were removed at day 75, subsequently allowing 5 days of exposure to light. These results indicate potential involvement of this MAP in experience-dependent structural plasticity.
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Affiliation(s)
- D Werner
- Department of Biology, University of Illinois at Urbana-Champaign, Urbana 61801, USA
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20
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Mandell JW, Banker GA. The microtubule cytoskeleton and the development of neuronal polarity. Neurobiol Aging 1995; 16:229-37; discussion 238. [PMID: 7566333 DOI: 10.1016/0197-4580(94)00164-v] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The concept that axons and dendrites represent a fundamental polarization of the nerve cell has been borne out by numerous morphological, functional, and molecular studies. How does polarity arise during development? We and others have focused on the role of the microtubule cytoskeleton because microtubules (a) are essential components of axons and dendrites; (b) possess an inherent polarity at the molecular level; (c) are regulated by interactions with microtubule associated proteins (MAPs), some of which have polarized distributions in mature neurons. Here we review data on the initial acquisition of polarity as observed in neuronal culture and roles for microtubules and MAPs in this morphogenetic event. We present data clarifying some previously conflicting results on tau localization during the establishment of polarity and provide new evidence that phosphorylation of tau is spatially regulated during the development of polarity in culture. Elucidation of mechanisms locally regulating tau phosphorylation during normal neuronal development may provide clues to the significance of its abnormal phosphorylation in Alzheimer's disease.
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Haque N, Denman RB, Merz G, Grundke-Iqbal I, Iqbal K. Phosphorylation and accumulation of tau without any concomitant increase in tubulin levels in Chinese hamster ovary cells stably transfected with human tau441. FEBS Lett 1995; 360:132-6. [PMID: 7875317 DOI: 10.1016/0014-5793(95)00089-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Eucaryotic expression vectors bearing a 1.4 kb cDNA encoding the 4 repeat isoform of human tau, tau441, in either the sense or anti-sense orientation with respect to a cytomegalovirus (CMV) promoter were constructed. The resulting constructs were used to transiently express tau in Chinese Hamster Ovary cells and to generate non-neuronal stable cell lines. Immunocytochemical studies of these cells show that tau is expressed in the sense but not the anti-sense or vector containing lines. Some of the cells expressing tau showed fine elongated processes which were stained by tau antibodies. The general tau immunostaining pattern appeared diffuse and punctuate. The expressed tau was seen both unbound and bound to microtubules. In some cells labeling with antibodies that specifically recognize hyperphosphorylation of tau was observed. The size of this population increased with increasing numbers of cell passages. However, no increase in steady-state tubulin level was observed following tau441 expression. These studies show that tau can accumulate in the cells without a concomitant increase in tubulin.
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Affiliation(s)
- N Haque
- New York State Institute for Basic Research in Developmental Disabilities, NY 10314
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22
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Microtubule-based intracellular transport of organelles. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s1874-6020(06)80017-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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23
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Expression of low molecular weight isoforms of microtubule-associated protein 2. Phosphorylation and induction of microtubule assembly in vitro. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(20)30076-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Bré MH, de Néchaud B, Wolff A, Fleury A. Glutamylated tubulin probed in ciliates with the monoclonal antibody GT335. CELL MOTILITY AND THE CYTOSKELETON 1994; 27:337-49. [PMID: 7520839 DOI: 10.1002/cm.970270406] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Microtubular networks are extensively developed in many ciliate species. In several of them, we investigate the occurrence of the post-translational glutamylation of tubulin [Eddé et al., 1990: Science 247:82-85; Eddé et al., 1991: J. Cell. Biochem. 46:134-142] using as a probe for such modified tubulin, the monoclonal antibody GT335 [Wolff et al., 1992: Eur. J. Cell Biol. 59:425-432]. Results obtained in Paramecium strongly suggest that both axonemal and cytoplasmic tubulin are glutamylated. As in the vertebrate brain tubulin so far tested, the GT335 epitope is located at the carboxy-terminal fragment of cytoplasmic tubulin removed by subtilisin treatment. Immunoblotting and immunofluorescence experiments reveal that, unlike tubulin acetylation, glutamylation is not restricted to cold-resistant microtubules. In addition, immunofluorescence studies performed on dividing cells show that glutamylation takes place soon after the polymerization of microtubules. Finally, glutamylated tubulin is also detected in the ciliate species Euplotes, Tetrahymena, and Paraurostyla. Together with results obtained on flagellate species, this suggests that tubulin glutamylation came out early in the course of eukaryotic evolution and has been widely exploited in various cellular strategies.
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Affiliation(s)
- M H Bré
- Laboratoire de Biologie Cellulaire 4, CNRS URA 1134, Université Paris XI, Orsay, France
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27
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Gordon-Weeks PR. Organization of microtubules in axonal growth cones: a role for microtubule-associated protein MAP 1B. JOURNAL OF NEUROCYTOLOGY 1993; 22:717-25. [PMID: 8270956 DOI: 10.1007/bf01181317] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Neuronal growth cones guide growing axons and dendrites (neurites) through developing embryos by detecting extrinsic guidance cues and transducing the signal into changes in motile behaviour. In this brief review, the role of the growth cone cytoskeleton in these events, in particular the microtubules, is discussed. Microtubules in the neurite are mainly bundled into fascicles whereas on entering the growth cone they diverge from each other and traverse the central (C)-domain of the growth cone. Occasionally, individual microtubules extend as far as the peripheral (P)-domain and may even enter filopodia. Microtubules in the growth cone are probably dynamically unstable, exchanging dimer with a large pool of soluble tubulin. It is proposed that the 'capture' of dynamically unstable microtubules by filopodial actin filament bundles is a crucial step underlying directed growth. Localised assembly of microtubules at the growth cone, rather than at the cell body followed by transport of polymer to the growth cone, may facilitate the delivery of material to specific regions of the growth cone and hence allow vectorial growth. Bundling of microtubules and capture of microtubules by filopodia both imply roles for microtubule-associated proteins (MAPs). Several microtubule-associated proteins are present within growth cones, including MAP 1B, MAP2 and tau. Recent experiments point toward a phosphorylated form of MAP 1B as an important component in neurite elongation and in particular in the bundling of microtubules in the growth cone.
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Kunze D, Rüstow B. Pathobiochemical aspects of cytoskeleton components. EUROPEAN JOURNAL OF CLINICAL CHEMISTRY AND CLINICAL BIOCHEMISTRY : JOURNAL OF THE FORUM OF EUROPEAN CLINICAL CHEMISTRY SOCIETIES 1993; 31:477-89. [PMID: 8218579 DOI: 10.1515/cclm.1993.31.8.477] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
This review summarizes pathobiochemical aspects of diseases, in which cytoskeletal components play a crucial role in pathogenesis. An attempt to classify the disorders on the basis of phenotypic changes that occur in microfilaments, intermediate filaments and microtubuli was unsuccessful. Three groups of disorders are presented: 1. cytoplasmic inclusions in specific diseases (merely descriptive); 2. diseases with genetic defects in cytoskeletal proteins (a chain of causality from defect to phenotype, in some cases with large gaps); 3. diseases with suspected involvement of cytoskeleton (hypothetical causal chain). Microfilaments are involved in certain pathogenetic processes on account of defects in their associated proteins; in Duchenne muscular dystrophy, dystrophin is defective, while the defective protein in Rett syndrome is synapsin. Defects in spectrin and membrane anchor proteins lead to disorders of the red cell membrane skeleton (congenital haemolytic anaemias). Intermediate filaments accumulate in some types of cytoplasmic inclusions, together with ubiquitin (Mallory bodies, desmin accumulation in some myopathies and others). A pathogenetic interpretation of this phenomenon is lacking. A genetic defect in certain types of keratin is the cause of epidermolysis bullosa. Interesting preliminary results are reviewed that reveal the crucial role of cytoskeletal components in a further group of diseases (intrahepatic cholestasis, Alzheimer disease, pemphigus). These disorders are currently under investigation, or are of theoretical interest with respect to the cytoskeleton. Specific reactions of cytoskeletal components in serum, which might be used diagnostically, have not been found.
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Affiliation(s)
- D Kunze
- Institute of Pathological and Clinical Biochemistry, Charité Hospital, Humboldt University Berlin
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Gregory PE, Gutmann DH, Mitchell A, Park S, Boguski M, Jacks T, Wood DL, Jove R, Collins FS. Neurofibromatosis type 1 gene product (neurofibromin) associates with microtubules. SOMATIC CELL AND MOLECULAR GENETICS 1993; 19:265-74. [PMID: 8332934 DOI: 10.1007/bf01233074] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The neurofibromatosis type 1 (NF1) gene was recently identified by positional cloning and found to encode a protein with structural and functional homology to mammalian and yeast GTPase-activating proteins (GAPs). Using antibodies directed against the NF1 gene product, a protein of approximately 250 kDa was identified and termed neurofibromin. Double-indirect immunofluorescent labeling with anti-neurofibromin and anti-tubulin antibodies demonstrates that neurofibromin associates with cytoplasmic microtubules. Immunoblotting of microtubule-enriched cytoplasmic fractions, using antibodies generated against neurofibromin, shows that neurofibromin copurifies with microtubules. When portions of neurofibromin are expressed in Sf9 insect cells they associate with polymerized microtubules; furthermore, the critical residues for this interaction reside within the GAP-related domain of neurofibromin. The unexpected association of neurofibromin with microtubules suggests that neurofibromin is involved in microtubule-mediated intracellular signal transduction pathways.
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Affiliation(s)
- P E Gregory
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109
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30
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Lopez LA, Sheetz MP. Steric inhibition of cytoplasmic dynein and kinesin motility by MAP2. CELL MOTILITY AND THE CYTOSKELETON 1993; 24:1-16. [PMID: 8319263 DOI: 10.1002/cm.970240102] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Using several in vitro motility assays, we found that motility driven by the microtubule (MT) motors, kinesin and cytoplasmic dynein, could be inhibited by MAP2 but not by tau protein or the MT-binding proteolytic fragment of MAP2. In MT gliding assays, even the presence of one MAP2 molecule per sixty-nine tubulin dimers caused an inhibition of about 75% of MT motility at low concentrations of both motors. The percent inhibition of motility decreased with increasing concentration of either motor, suggesting that the inhibition was the result of competition for access to the MT surface. The decrease in the number of moving MTs with MAP2 was correlated with an increase in the frequency of release of moving MTs from the motor-coated glass. In assays of in vitro vesicular organelle motility and formation of ER networks, the presence of MAP2 inhibited small vesicle movements and to a lesser extent ER network formation. To determine if competition for specific sites on the MT or coating of the MT surface inhibited motility, we used tau protein and the chymotryptic MT-binding fragments of MAP2 to coat MTs. No inhibition was observed and there was even an increase in the number of attached and moving MTs in the gliding assay with tau-coated MTs. Because MAP2, tau and the chymotryptic MT-binding fragments of MAP2 bind to the same domain on tubulin, masking of the MT surface sites does not appear responsible for the inhibition of motility by MAP2. Rather, we suggest that the sidearm of MAP2 interfered with the interaction of motors with MTs and caused a dramatic increase in the rate of MT release. In vivo, MAP2 could play a major role in the generation of cellular polarity even at substoichiometric levels by inhibiting transport on microtubules in specific domains of the cytoplasm.
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Affiliation(s)
- L A Lopez
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710
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31
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Vantard M, Schellenbaum P, Peter C, Lambert AM. Higher plant microtubule-associated proteins: in vitro functional assays. Biochimie 1993; 75:725-30. [PMID: 8286444 DOI: 10.1016/0300-9084(93)90103-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Microtubule-associated proteins (MAPs) can account for the assembly and stabilization of microtubules at low tubulin concentration, for their ability to interact with other microtubules and/or cytoskeletal polymers or organelles and also for regulating microtubule anchoring and bundling properties. The data concerning higher plant MAPs remain limited so far to a few examples. Motor MAPs such as dynein or kinesin remain poorly documented in plants and are not to be discussed here. In this manuscript, the attention is focused on structural MAPs which co-assemble with tubulin during microtubule assembly. Using taxol, we developed an assay where higher plant microtubules were induced to self-assemble in a cytosolic extract of maize cultured cells and could be used as a native matrix for the isolation of putative higher plant MAPs. Seven polypeptides with molecular masses ranging between 60-125 kDa were found in this MAP-enriched fraction. These putative plant MAPs were shown to co-assemble with pig brain tubulin through two cycles of temperature-dependent assembly-disassembly. They were able to initiate and promote MAP-free tubulin assembly under conditions of non-efficient self-assembly and induced bundling of both plant and neural microtubules. One of these polypeptides (83 kDa) was found to be immunologically related to neural tau, suggesting the presence of common epitopes between neural and plant MAPs. Such epitopes may be present at the microtubule-binding domains, as the higher plant MAPs co-assemble with brain tubulin. Plant microtubules exhibit an important in situ bundling activity, as in cortical or pre-prophase band arrays, or during the drastic reorganization of the cytoskeleton during mitosis induction.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Vantard
- Institut de Biologie Moléculaire des Plantes, Strasbourg, France
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32
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Pienta KJ, Murphy BC, Getzenberg RH, Coffey DS. The Tissue Matrix and The Regulation of Gene Expression in Cancer Cells. BIOLOGY OF THE CANCER CELL 1993. [DOI: 10.1016/s1569-2558(08)60238-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Sabry JH, O'Connor TP, Evans L, Toroian-Raymond A, Kirschner M, Bentley D. Microtubule behavior during guidance of pioneer neuron growth cones in situ. J Cell Biol 1991; 115:381-95. [PMID: 1918146 PMCID: PMC2289145 DOI: 10.1083/jcb.115.2.381] [Citation(s) in RCA: 183] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The growth of an axon toward its target results from the reorganization of the cytoskeleton in response to environmental guidance cues. Recently developed imaging technology makes it possible to address the effect of such cues on the neural cytoskeleton directly. Although high resolution studies can be carried out on neurons in vitro, these circumstances do not recreate the complexity of the natural environment. We report here on the arrangement and dynamics of microtubules in live neurons pathfinding in response to natural guidance cues in situ using the embryonic grasshopper limb fillet preparation. A rich microtubule network was present within the body of the growth cone and normally extended into the distal growth cone margin. Complex microtubule loops often formed transiently within the growth cone. Branches both with and without microtubules were regularly observed. Microtubules did not extend into filopodia. During growth cone steering events in response to identified guidance cues, microtubule behaviour could be monitored. In turns towards guidepost cells, microtubules selectively invaded branches derived from filopodia that had contacted the guidepost cell. At limb segment boundaries, microtubules displayed a variety of behaviors, including selective branch invasion, and also invasion of multiple branches followed by selective retention in branches oriented in the correct direction. Microtubule invasion of multiple branches also was seen in growth cones migrating on intrasegmental epithelium. Both selective invasion and selective retention generate asymmetrical microtubule arrangements within the growth cone, and may play a key role in growth cone steering events.
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Affiliation(s)
- J H Sabry
- Department of Biochemistry and Biophysics, University of California, San Francisco 94143
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Abstract
In vitro and in vivo studies of specific neuronal fast and slow transport components are presently reshaping our understanding of how the processes of vesicular and cytoskeletal transport are regulated in axons and dendrites. Evidence suggests that vesicles possess an inherent directionality, possibly the result of their motor receptor proteins responding to intracellular cues, which then allows movement with either kinesin or cytoplasmic dynein.
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Affiliation(s)
- M P Sheetz
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710
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Abstract
Microtubules are ubiquitous cellular components involved in the control of cell structure and functions, such as cell division, regulation of shape and polarity, intracellular transport, etc. Consequently, any alteration affecting them in structure or function has a good chance of affecting the cell and generally leads to cell dysfunctions. This has been shown for instance, after treatment with microtubule-interacting drugs. Cellular aging is also characterized by the appearance of various cell dysfunctions, but the possible involvement of the microtubules in the aging process, although a rather tempting hypothesis, has not yet been extensively investigated. In this paper, I will first rapidly review the different components that build, organize and control the microtubules in normal cells, independently of the aging process. I will then consider the possible involvement of the microtubules in the aging process, more particularly in models of cells aging in vitro and in aging neuronal cells, which have been the most extensively investigated. There is some evidence for alterations in the microtubule organization both in cells aging in vitro and in the aging brain. But the interpretation of these data awaits further experiments, taking into account the latest progress in tubulin genetics and in microtubule biochemistry. Microtubules could also represent one of the cellular targets affected after signal transduction and could thus be involved in the resulting cellular responses. This hypothesis will be discussed, as it offers new insights into the regulation of microtubule organization, dynamics and functions in normal cells, which will be worthwhile to investigate during the aging process.
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Affiliation(s)
- M Raes
- Laboratoire de Biochimie Cellulaire, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium
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Abstract
Cloning of primary sequences has generated information on the structures of the non-motor microtubule-associated proteins and their relationship to one another. Questions about how classes of microtubule-associated proteins interact are starting to be addressed in vitro and, in vivo, tests of function are being pursued using a variety of cellular and molecular biological strategies.
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Affiliation(s)
- J B Olmsted
- Department of Biology, University of Rochester, New York 14627
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Fliegner KH, Liem RK. Cellular and molecular biology of neuronal intermediate filaments. INTERNATIONAL REVIEW OF CYTOLOGY 1991; 131:109-67. [PMID: 1722198 DOI: 10.1016/s0074-7696(08)62018-5] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- K H Fliegner
- Department of Pathology, Columbia University College of Physicians and Surgeons, New York, New York 10032
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van der Hoorn FA, Tarnasky HA, Nordeen SK. A new rat gene RT7 is specifically expressed during spermatogenesis. Dev Biol 1990; 142:147-54. [PMID: 1699827 DOI: 10.1016/0012-1606(90)90158-f] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We report the isolation of a new rat male germ cell-specific gene, RT7, by differential cDNA cloning procedures. The RT7 cDNA nucleotide sequence is not homologous to any sequences present in the GenBank library. RT7 RNA is expressed at very high levels in rat early spermatids, while its expression is not detectable in any other organ or tissue examined. Mapping of the RT7 transcription start site by two independent procedures demonstrated that RT7 has two major and a number of upstream minor start sites for transcription. RT7 encodes a putative 90-amino acid protein, of which the N-terminus is predicted to fold as an amphipathic alpha helix with features resembling the leucine zipper structure found in a family of transcription factors. However, unlike the leucine zipper proteins the RT7 alpha helix is not preceded by a basic region. Analysis of the RT7 promoter sequence indicates that it contains a putative testis-specific regulatory sequence found in protamine P1 and P2 promoters, as well as binding sites for several other transcription factors.
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Affiliation(s)
- F A van der Hoorn
- Department of Medical Biochemistry, University of Calgary Health Sciences Centre, Alberta, Canada
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