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Odango RJ, Camberos J, Fregoso FE, Fischhaber PL. SAW1 is increasingly required to recruit Rad10 as SSA flap-length increases from 20 to 50 bases in single-strand annealing in S. cerevisiae. Biochem Biophys Rep 2021; 28:101125. [PMID: 34622036 PMCID: PMC8481969 DOI: 10.1016/j.bbrep.2021.101125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/27/2021] [Accepted: 08/30/2021] [Indexed: 11/16/2022] Open
Abstract
SAW1 is required by the Rad1-Rad10 nuclease for efficient removal of 3′ non-homologous DNA ends (flaps) formed as intermediates during two modes of double-strand break repair in S. cerevisiae, single-strand annealing (SSA) and synthesis-dependent strand annealing (SDSA). Saw1 was shown in vitro to exhibit increasing affinity for flap DNAs as flap lengths varied from 0 to 40 deoxynucleotides (nt) with almost no binding observed when flaps were shorter than 10 nt. Accordingly, our prior in vivo fluorescence microscopy investigation showed that SAW1 was not required for recruitment of Rad10-YFP to DNA double-strand breaks (DSBs) when flaps were ∼10 nt, but it was required when flaps were ∼500 nt in G1 phase of the cell cycle. We were curious whether we would also observe an increased requirement of SAW1 for Rad10 recruitment in vivo as flaps varied from ∼20 to 50 nt, as was shown in vitro. In this investigation, we utilized SSA substrates that generate 20, 30, and 50 nt flaps in vivo in fluorescence microscopy assays and determined that SAW1 becomes increasingly necessary for SSA starting at about ∼20 nt and is completely required at ∼50 nt. Quantitative PCR experiments corroborate these results by demonstrating that repair product formation decreases in the absence of SAW1 as flap length increases. Experiments with strains containing fluorescently labeled Saw1 (Saw1-CFP) show that Saw1 localizes with Rad10 at SSA foci and that about half of the foci containing Rad10 at DSBs do not contain Saw1. Colocalization patterns of Saw1-CFP are consistent regardless of the flap length of the substrate and are roughly similar in all phases of the cell cycle. Together, these data show that Saw1 becomes increasingly important for Rad1-Rad10 recruitment and SSA repair in the ∼20–50 nt flap range, and Saw1 is present at repair sites even when not required and may depart the repair site ahead of Rad1-Rad10. There is an increasing dependence on Saw1 to recruit Rad1-Rad10 as DNA flaps increase The flap length range causing the increasing dependence is 20–50 deoxynucleotides Saw1 is found at single-strand annealing foci even when not required to recruit Rad1-Rad10 Saw1 is found in only about half of the single-strand annealing foci containing Rad1-Rad10
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Affiliation(s)
- Rowen Jane Odango
- Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St, Northridge, CA, 91330-8262, United States
| | - Juan Camberos
- Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St, Northridge, CA, 91330-8262, United States
| | - Fred Erick Fregoso
- Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St, Northridge, CA, 91330-8262, United States
| | - Paula L Fischhaber
- Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St, Northridge, CA, 91330-8262, United States
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Corral-Ramos C, Roca MG, Di Pietro A, Roncero MIG, Ruiz-Roldán C. Autophagy contributes to regulation of nuclear dynamics during vegetative growth and hyphal fusion in Fusarium oxysporum. Autophagy 2015; 11:131-44. [PMID: 25560310 DOI: 10.4161/15548627.2014.994413] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In the fungal pathogen Fusarium oxysporum, vegetative hyphal fusion triggers nuclear mitotic division in the invading hypha followed by migration of a nucleus into the receptor hypha and degradation of the resident nucleus. Here we examined the role of autophagy in fusion-induced nuclear degradation. A search of the F. oxysporum genome database for autophagy pathway components identified putative orthologs of 16 core autophagy-related (ATG) genes in yeast, including the ubiquitin-like protein Atg8, which is required for the formation of autophagosomal membranes. F. oxysporum Foatg8Δ mutants were generated in a strain harboring H1-cherry fluorescent protein (ChFP)-labeled nuclei to facilitate analysis of nuclear dynamics. The Foatg8Δ mutants did not show MDC-positive staining in contrast to the wild type and the FoATG8-complemented (cFoATG8) strain, suggesting that FoAtg8 is required for autophagy in F. oxysporum. The Foatg8Δ strains displayed reduced rates of hyphal growth, conidiation, and fusion, and were significantly attenuated in virulence on tomato plants and in the nonvertebrate animal host Galleria mellonella. In contrast to wild-type hyphae, which are almost exclusively composed of uninucleated hyphal compartments, the hyphae of the Foatg8Δ mutants contained a significant fraction of hyphal compartments with 2 or more nuclei. The increase in the number of nuclei per hyphal compartment was particularly evident after hyphal fusion events. Time-lapse microscopy analyses revealed abnormal mitotic patterns during vegetative growth in the Foatg8Δ mutants. Our results suggest that autophagy mediates nuclear degradation after hyphal fusion and has a general function in the control of nuclear distribution in F. oxysporum.
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Key Words
- Atg, autophagy-related
- BLAST, basic local alignment search tool
- CFW, calcofluor white
- ChFP, cherry fluorescent protein
- DIC, differential interference contrast
- Fusarium oxysporum
- GFP, green fluorescent protein
- HygR, hygromycin resistant
- MDC, monodansylcadaverine
- ORF, open reading frame
- PCR, polymerase chain reaction
- PDA, potato dextrose agar
- PDB, potato dextrose broth
- PMSF, phenylmethylsulfonyl fluoride
- SM, synthetic medium
- WT, wild-type
- autophagy
- filamentous fungi
- gDNA, genomic DNA
- hyphal fusion
- nuclear dynamics
- virulence
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Affiliation(s)
- Cristina Corral-Ramos
- a Departamento de Genética; Universidad de Córdoba; Campus de Excelencia Agroalimentario ; Córdoba , Spain
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Hasegawa H, Woods CE, Kinderman F, He F, Lim AC. Russell body phenotype is preferentially induced by IgG mAb clones with high intrinsic condensation propensity: relations between the biosynthetic events in the ER and solution behaviors in vitro. MAbs 2015; 6:1518-32. [PMID: 25484054 DOI: 10.4161/mabs.36242] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The underlying reasons for why some mAb (monoclonal antibody) clones are much more inclined to induce a Russell body (RB) phenotype during immunoglobulin biosynthesis remain elusive. Although RBs are morphologically understood as enlarged globular aggregates of immunoglobulins deposited in the endoplasmic reticulum (ER), little is known about the properties of the RB-inducing mAb clones as secretory cargo and their physical behaviors in the extracellular space. To elucidate how RB-inducing propensities, secretion outputs, and the intrinsic physicochemical properties of individual mAb clones are interrelated, we used HEK293 cells to study the biosynthesis of 5 human IgG mAbs for which prominent solution behavior problems were known a priori. All 5 model mAbs with inherently high condensation propensities induced RB phenotypes both at steady state and under ER-to-Golgi transport block, and resulted in low secretion titer. By contrast, one reference mAb that readily crystallized at neutral pH in vitro produced rod-shaped crystalline bodies in the ER without inducing RBs. Another reference mAb without notable solution behavior issues did not induce RBs and was secreted abundantly. Intrinsic physicochemical properties of individual IgG clones thus directly affected the biosynthetic steps in the ER, and thereby produced distinctive cellular phenotypes and influenced IgG secretion output. The findings implicated that RB formation represents a phase separation event or a loss of colloidal stability in the secretory pathway organelles. The process of RB induction allows the cell to preemptively reduce the extracellular concentration of potentially pathogenic, highly aggregation-prone IgG clones by selectively storing them in the ER.
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Key Words
- BFA, Brefeldin A
- CB, crystalline body
- DIC, differential interference contrast
- ER, endoplasmic reticulum;
- Fab, fragment antigen binding
- HC, heavy chain
- HEK, human embryonic kidney
- IgG, immunoglobulin G
- LC, light chain;
- RB, Russell body
- Russell body
- VH, heavy chain variable domain
- VL, light chain variable domain
- crystalline body
- endoplasmic reticulum
- gelation
- immunoglobulin
- mAb, monoclonal antibody
- phase separation
- protein aggregation
- protein condensation
- protein crystallization
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Affiliation(s)
- Haruki Hasegawa
- a Department of Therapeutic Discovery; Amgen ; Seattle , WA USA
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Yamashita M. Weak electric fields serve as guidance cues that direct retinal ganglion cell axons in vitro. Biochem Biophys Rep 2015; 4:83-88. [PMID: 29124190 PMCID: PMC5668898 DOI: 10.1016/j.bbrep.2015.08.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 08/17/2015] [Accepted: 08/28/2015] [Indexed: 11/28/2022] Open
Abstract
Growing axons are directed by an extracellular electric field in a process known as galvanotropism. The electric field is a predominant guidance cue directing retinal ganglion cell (RGC) axons to the future optic disc during embryonic development. Specifically, the axons of newborn RGCs grow along the extracellular voltage gradient that exists endogenously in the embryonic retina (Yamashita, 2013 [8]). To investigate the molecular mechanisms underlying galvanotropic behaviour, the quantification of the electric effect on axon orientation must be examined. In the present study, a culture system was built to apply a constant, uniform direct current (DC) electric field by supplying an electrical current to the culture medium, and this system also continuously recorded the voltage difference between the two points in the medium. A negative feedback circuit was designed to regulate the supplied current to maintain the voltage difference at the desired value. A chick embryo retinal strip was placed between the two points and cultured for 24 h in an electric field in the opposite direction to the endogenous field, and growing axons were fluorescently labelled for live cell imaging (calcein-AM). The strength of the exogenous field varied from 0.0005 mV/mm to 10.0 mV/mm. The results showed that RGC axons grew in the reverse direction towards the cathode at voltage gradients of ≥0.0005 mV/mm, and straightforward extensions were found in fields of ≥0.2–0.5 mV/mm, which were far weaker than the endogenous voltage gradient (15 mV/mm). These findings suggest that the endogenous electric field is sufficient to guide RGC axons in vivo. Retinal ganglion cell axons grow along an extracellular electric field. A culture system was built to apply a constant, uniform DC electric field. Weak electric fields (≥ 0.0005 mV/mm) were effective for the cathodal orientation. The endogenous field (15 mV/mm) is sufficient for the correct guidance of axons.
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Affiliation(s)
- Masayuki Yamashita
- Center for Medical Science, International University of Health and Welfare, 2600-1 Kitakanemaru, Ohtawara 324-8501, Japan
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Okumura H, Sato T, Sakuma R, Fukushima H, Matsuda T, Ujita M. Identification of distinctive interdomain interactions among ZP-N, ZP-C and other domains of zona pellucida glycoproteins underlying association of chicken egg-coat matrix. FEBS Open Bio 2015; 5:454-65. [PMID: 26106520 PMCID: PMC4475693 DOI: 10.1016/j.fob.2015.05.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 05/15/2015] [Accepted: 05/22/2015] [Indexed: 12/12/2022] Open
Abstract
Chicken ZP1 and ZP3 assemble through strong interactions between their ZP-C domains. ZP-C domains of chicken ZP1 and ZP3 are deeply embedded in the egg-coat matrix. Chicken ZP1 forms a homocomplex through non-covalent interaction between repeat domains. Chicken ZPD is deposited on the interstices of ZP1–ZP3 matrix in the egg coat. We propose a model for the architecture of chicken egg-coat matrix from these results.
The vertebrate egg coat, including mammalian zona pellucida, is an oocyte-specific extracellular matrix comprising two to six zona pellucida (ZP) glycoproteins. The egg coat plays important roles in fertilization, especially in species-specific interactions with sperm to induce the sperm acrosome reaction and to form the block to polyspermy. It is suggested that the physiological functions of the egg coat are mediated and/or regulated coordinately by peptide and carbohydrate moieties of the ZP glycoproteins that are spatially arranged in the egg coat, whereas a comprehensive understanding of the architecture of vertebrate egg-coat matrix remains elusive. Here, we deduced the orientations and/or distributions of chicken ZP glycoproteins, ZP1, ZP3 and ZPD, in the egg-coat matrix by confocal immunofluorescent microscopy, and in the ZP1–ZP3 complexes generated in vitro by co-immunoprecipitation assays. We further confirmed interdomain interactions of the ZP glycoproteins by far-Western blot analyses of the egg-coat proteins and pull-down assays of ZP1 in the serum, using recombinant domains of ZP glycoproteins as probes. Our results suggest that the ZP1 and ZP3 bind through their ZP-C domains to form the ZP1–ZP3 complexes and fibrils, which are assembled into bundles through interactions between the repeat domains of ZP1 to form the ZP1–ZP3 matrix, and that the ZPD molecules self-associate and bind to the ZP1–ZP3 matrix through its ZP-N and ZP-C domains to form the egg-coat matrix. Based on these results, we propose a tentative model for the architecture of the chicken egg-coat matrix that might be applicable to other vertebrate ones.
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Key Words
- CBB, Coomassie Brilliant Blue
- DIC, differential interference contrast
- DTT, dithiothreitol
- EGF, epidermal growth factor
- EHP, external hydrophobic patch
- Egg coat
- Extracellular matrix
- Fertilization
- His6, hexahistidine
- IHP, internal hydrophobic patch
- Interdomain interaction
- MBP, maltose binding protein
- RT, room temperature
- TGFR, transforming growth factor-β receptor
- THP, Tamm–Horsfall protein
- Trx, thioredoxin
- ZP, zona pellucida
- Zona pellucida
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Affiliation(s)
- Hiroki Okumura
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Meijo University, Nagoya 468-8502, Japan
- Corresponding author. Tel.: +81 52 838 2451; fax: +81 52 833 5524.
| | - Takahiro Sato
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Meijo University, Nagoya 468-8502, Japan
| | - Rio Sakuma
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Meijo University, Nagoya 468-8502, Japan
| | - Hideaki Fukushima
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Meijo University, Nagoya 468-8502, Japan
| | - Tsukasa Matsuda
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Minoru Ujita
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Meijo University, Nagoya 468-8502, Japan
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Livanos P, Giannoutsou E, Apostolakos P, Galatis B. Auxin as an inducer of asymmetrical division generating the subsidiary cells in stomatal complexes of Zea mays. Plant Signal Behav 2015; 10:e984531. [PMID: 25831267 PMCID: PMC4622748 DOI: 10.4161/15592324.2014.984531] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 09/20/2014] [Accepted: 09/23/2014] [Indexed: 05/05/2023]
Abstract
The data presented in this work revealed that in Zea mays the exogenously added auxins indole-3-acetic acid (IAA) and 1-napthaleneacetic acid (NAA), promoted the establishment of subsidiary cell mother cell (SMC) polarity and the subsequent subsidiary cell formation, while treatment with auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and 1-napthoxyacetic acid (NOA) specifically blocked SMC polarization and asymmetrical division. Furthermore, in young guard cell mother cells (GMCs) the PIN1 auxin efflux carriers were mainly localized in the transverse GMC faces, while in the advanced GMCs they appeared both in the transverse and the lateral ones adjacent to SMCs. Considering that phosphatidyl-inositol-3-kinase (PI3K) is an active component of auxin signal transduction and that phospholipid signaling contributes in the establishment of polarity, treatments with the specific inhibitor of the PI3K LY294002 were carried out. The presence of LY294002 suppressed polarization of SMCs and prevented their asymmetrical division, whereas combined treatment with exogenously added NAA and LY294002 restricted the promotional auxin influence on subsidiary cell formation. These findings support the view that auxin is involved in Z. mays subsidiary cell formation, probably functioning as inducer of the asymmetrical SMC division. Collectively, the results obtained from treatments with auxin transport inhibitors and the appearance of PIN1 proteins in the lateral GMC faces indicate a local transfer of auxin from GMCs to SMCs. Moreover, auxin signal transduction seems to be mediated by the catalytic function of PI3K.
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Key Words
- AF, actin filament
- DIC, differential interference contrast
- GMC, guard cell mother cell
- IAA, indole-3-acetic acid
- MT, microtubule
- NAA, 1-napthaleneacetic acid
- NOA, 1-napthoxyacetic acid
- PDK, 3-phosphoinositide-dependent kinase
- PI3K, phosphatidyl-inositol-3-kinase
- PIN1
- PLC, phospholipase C
- PLD, phospholipase D
- ROP GTPases, Rho-like GTPases of plants
- SMC, subsidiary cell mother cell
- TIBA, 2,3,5-triiodobenzoic acid
- auxin carriers
- auxin signaling
- morphogenesis
- phosphatidyl-inositol-3-kinase
- polarity
- stomatal complexes
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Affiliation(s)
- Pantelis Livanos
- Department of Botany; Faculty of Biology; University of Athens; Athens, Greece
| | - Eleni Giannoutsou
- Department of Botany; Faculty of Biology; University of Athens; Athens, Greece
| | | | - Basil Galatis
- Department of Botany; Faculty of Biology; University of Athens; Athens, Greece
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7
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Hall MK, Weidner DA, Dayal S, Schwalbe RA. Cell surface N-glycans influence the level of functional E-cadherin at the cell-cell border. FEBS Open Bio 2014; 4:892-7. [PMID: 25379387 DOI: 10.1016/j.fob.2014.10.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 10/09/2014] [Accepted: 10/09/2014] [Indexed: 11/23/2022] Open
Abstract
Cell surface N-glycans impact E-cadherin placement at the cell–cell border. E-cadherin retention at the cell–cell border is affected by cell surface N-glycans. Cell surface N-glycans influence E-cadherin-mediated cell–cell adhesion. N-glycans outside the cell contribute to plasma membrane structure.
E-cadherin is crucial for adhesion of cells to each other and thereby development and maintenance of tissue. While it is has been established that N-glycans inside the cell impact the level of E-cadherin at the cell surface of epithelial-derived cells, it is unclear whether N-glycans outside the cell control the clustering of E-cadherin at the cell–cell border. Here, we demonstrate reduction of N-glycans at the cell surface weakened the recruitment and retention of E-cadherin at the cell–cell border, and consequently reduced the strength of cell–cell interactions. We conclude that N-glycans at the cell surface are tightly linked to the placement of E-cadherin at the cell–cell border and thereby control E-cadherin mediated cell–cell adhesion.
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8
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Zhao S, Liao H, Ao M, Wu L, Zhang X, Chen Y. Fixation-induced cell blebbing on spread cells inversely correlates with phosphatidylinositol 4,5-bisphosphate level in the plasma membrane. FEBS Open Bio 2014; 4:190-9. [PMID: 24649401 DOI: 10.1016/j.fob.2014.02.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 02/07/2014] [Accepted: 02/10/2014] [Indexed: 12/15/2022] Open
Abstract
Protein- but not lipid-stabilizing fixatives induce cell blebbing of spread cells. Asymmetric distribution of fixation-induced blebs coincides with that of PIP2. Fixation less readily induces blebbing on spread cells with elevated PIP2 levels. Fixation more readily induces blebbing on spread cells with lower PIP2 levels. Disruption of lipid rafts enhances fixation-induced blebbing of spread cells.
While most attention has been focused on physiologically generated blebs, the molecular mechanisms for fixation-induced cell blebbing are less investigated. We show that protein-fixing (e.g. aldehydes and picric acid) but not lipid-stabilizing (e.g. OsO4 and KMnO4) fixatives induce blebbing on spread cells. We also show that aldehyde fixation may induce the loss or delocalization of phosphatidylinositol 4,5-bisphosphate (PIP2) in the plasma membrane and that the asymmetric distribution of fixation-induced blebs on spread/migrating cells coincides with that of PIP2 on the cells prefixed by lipid-stabilizing fixatives (e.g., OsO4). Moreover, fixation induces blebbing less readily on PIP2-elevated spread cells but more readily on PIP2-lowered or lipid raft-disrupted spread cells. Our data suggest that fixation-induced lowering of PIP2 level at cytoskeleton-attaching membrane sites causes bleb formation via local breakdown of the membrane–cytoskeleton coupling.
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Key Words
- Cell blebbing
- Cell fixation
- DAG, 1,2-diacylglycerol
- DIC, differential interference contrast
- HUVECs, human umbilical vein endothelial cells
- Human umbilical vein endothelial cells (HUVECs)
- IP3, inositol 1,4,5-trisphosphate
- Lipid rafts
- MβCD, methyl-β-cyclodextrin
- PI3K, phosphoinositide-3 kinase
- PIP2, phosphatidylinositol 4,5-bisphosphate
- PIP3, phosphatidylinositol 3,4,5-trisphosphate
- PLC, phospholipase C
- Phosphatidylinositol 4,5-bisphosphate (PIP2)
- TBS, Tris-buffered saline
- THP-1-derived macrophages
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Uittenbogaard M, Baxter KK, Chiaramello A. The neurogenic basic helix-loop-helix transcription factor NeuroD6 confers tolerance to oxidative stress by triggering an antioxidant response and sustaining the mitochondrial biomass. ASN Neuro 2010; 2:e00034. [PMID: 20517466 DOI: 10.1042/AN20100005] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 04/09/2010] [Accepted: 04/21/2010] [Indexed: 12/21/2022] Open
Abstract
Preserving mitochondrial mass, bioenergetic functions and ROS (reactive oxygen species) homoeostasis is key to neuronal differentiation and survival, as mitochondria produce most of the energy in the form of ATP to execute and maintain these cellular processes. In view of our previous studies showing that NeuroD6 promotes neuronal differentiation and survival on trophic factor withdrawal, combined with its ability to stimulate the mitochondrial biomass and to trigger comprehensive antiapoptotic and molecular chaperone responses, we investigated whether NeuroD6 could concomitantly modulate the mitochondrial biomass and ROS homoeostasis on oxidative stress mediated by serum deprivation. In the present study, we report a novel role of NeuroD6 as a regulator of ROS homoeostasis, resulting in enhanced tolerance to oxidative stress. Using a combination of flow cytometry, confocal fluorescence microscopy and mitochondrial fractionation, we found that NeuroD6 sustains mitochondrial mass, intracellular ATP levels and expression of specific subunits of respiratory complexes upon oxidative stress triggered by withdrawal of trophic factors. NeuroD6 also maintains the expression of nuclear-encoded transcription factors, known to regulate mitochondrial biogenesis, such as PGC-1α (peroxisome-proliferator-activated receptor γ co-activator-1α), Tfam (transcription factor A, mitochondrial) and NRF-1 (nuclear respiratory factor-1). Finally, NeuroD6 triggers a comprehensive antioxidant response to endow PC12-ND6 cells with intracellular ROS scavenging capacity. The NeuroD6 effect is not limited to the classic induction of the ROS-scavenging enzymes, such as SOD2 (superoxide dismutase 2), GPx1 (glutathione peroxidase 1) and PRDX5 (peroxiredoxin 5), but also to the recently identified powerful ROS suppressors PGC-1α, PINK1 (phosphatase and tensin homologue-induced kinase 1) and SIRT1. Thus our collective results support the concept that the NeuroD6–PGC-1α–SIRT1 neuroprotective axis may be critical in co-ordinating the mitochondrial biomass with the antioxidant reserve to confer tolerance to oxidative stress.
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Key Words
- AD, Alzheimer’s disease
- AM, acetoxymethyl ester
- COX, cytochrome c oxidase
- DAPI, 4′,6-diamidino-2-phenylindole
- DIC, differential interference contrast
- Drp1, dynamin-related protein 1
- ETC, electron transfer chain
- GABP-α, GA-binding protein-α
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- GFP, green fluorescent protein
- GPx1, glutathione peroxidase 1
- HSP, heat-shock protein
- MMP, mitochondrial membrane potential
- MTG, MitoTracker® Green
- MTR, MitoTracker® Red
- Mfn2, mitofusin 2
- Mg-Gr, Magnesium Green
- NRF, nuclear respiratory factor
- NT-PGC-1α, N-terminal-truncated PGC-1α
- NeuroD family
- OPA1, optic atrophy 1
- OXPHOS, oxidative phosphorylation
- PDL, poly-d-lysine
- PGC-1α, peroxisome-proliferator-activated receptor γ co-activator-1α
- PINK1, phosphatase and tensin homologue-induced kinase 1
- PRDX5, peroxiredoxin 5
- ROS, reactive oxygen species
- SIRT1
- SOD, superoxide dismutase
- Tfam, transcription factor A, mitochondrial
- WGA, wheatgerm agglutinin
- bHLH, basic helix–loop–helix
- mitochondria
- mtDNA, mitochondrial DNA
- neuronal survival
- reactive oxygen species (ROS)
- transcriptional co-regulator peroxisome-proliferator-activated receptor γ co-activator-1α (PGC-1α)
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Gandhi GK, Ball KK, Cruz NF, Dienel GA. Hyperglycaemia and diabetes impair gap junctional communication among astrocytes. ASN Neuro 2010; 2:e00030. [PMID: 20396375 DOI: 10.1042/AN20090048] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 01/03/2010] [Accepted: 01/05/2010] [Indexed: 01/21/2023] Open
Abstract
Sensory and cognitive impairments have been documented in diabetic humans and
animals, but the pathophysiology of diabetes in the central nervous system is
poorly understood. Because a high glucose level disrupts gap junctional
communication in various cell types and astrocytes are extensively coupled by
gap junctions to form large syncytia, the influence of experimental diabetes on
gap junction channel-mediated dye transfer was assessed in astrocytes in tissue
culture and in brain slices from diabetic rats. Astrocytes grown in
15–25 mmol/l glucose had a slow-onset, poorly reversible decrement in
gap junctional communication compared with those grown in 5.5 mmol/l glucose.
Astrocytes in brain slices from adult STZ (streptozotocin)-treated rats at
20–24 weeks after the onset of diabetes also exhibited reduced dye
transfer. In cultured astrocytes grown in high glucose, increased oxidative
stress preceded the decrement in dye transfer by several days, and gap
junctional impairment was prevented, but not rescued, after its manifestation by
compounds that can block or reduce oxidative stress. In sharp contrast with
these findings, chaperone molecules known to facilitate protein folding could
prevent and rescue gap junctional impairment, even in the presence of elevated
glucose level and oxidative stress. Immunostaining of Cx (connexin) 43 and 30,
but not Cx26, was altered by growth in high glucose. Disruption of astrocytic
trafficking of metabolites and signalling molecules may alter interactions among
astrocytes, neurons and endothelial cells and contribute to changes in brain
function in diabetes. Involvement of the microvasculature may contribute to
diabetic complications in the brain, the cardiovascular system and other
organs.
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Key Words
- 4-PBA, 4-phenylbutyric acid
- 6-NBDG, 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose
- Cx, connexin
- DCF, 2′,7′-dichlorodihydrofluorescein
- DIC, differential interference contrast
- DMEM, Dulbecco's modified Eagle's medium
- ER, endoplasmic reticulum
- FBS, fetal bovine serum
- LYCH, Lucifer Yellow CH
- LYVS, Lucifer Yellow VS
- MnTBAP, manganese(III) tetrakis (4-benzoic acid) porphyrin chloride
- NA, numerical aperture
- NOS, nitric oxide synthase
- PKC, protein kinase C
- RNS, reactive nitrogen species
- ROS, reactive oxygen species
- STZ, streptozotocin
- TMAO, trimethylamine N-oxide dihydrate
- TUDCA, tauroursodeoxycholic acid
- aCSF, artificial cerebrospinal fluid
- astrocyte
- carboxy-DCF-DA, carboxy DCF diacetate
- connexin (Cx)
- dBcAMP, dibutyryl cAMP
- diabetes
- gap junction
- hyperglycaemia
- l-NAME, l-Nω-nitro-l-arginine methyl ester
- streptozotocin
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