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Article ; Online: Deletion of Transglutaminase 2 from Mouse Astrocytes Significantly Improves Their Ability to Promote Neurite Outgrowth on an Inhibitory Matrix

Jacen Emerson / Thomas Delgado / Peter Girardi / Gail V. W. Johnson

International Journal of Molecular Sciences, Vol 24, Iss 6058, p

2023 Volume 6058

Abstract: Astrocytes are the primary support cells of the central nervous system (CNS) that help maintain the energetic requirements and homeostatic environment of neurons. CNS injury causes astrocytes to take on reactive phenotypes with an altered overall ... ...

Abstract	Astrocytes are the primary support cells of the central nervous system (CNS) that help maintain the energetic requirements and homeostatic environment of neurons. CNS injury causes astrocytes to take on reactive phenotypes with an altered overall function that can range from supportive to harmful for recovering neurons. The characterization of reactive astrocyte populations is a rapidly developing field, and the underlying factors and signaling pathways governing which type of reactive phenotype that astrocytes take on are poorly understood. Our previous studies suggest that transglutaminase 2 (TG2) has an important role in determining the astrocytic response to injury. Selectively deleting TG2 from astrocytes improves functional outcomes after CNS injury and causes widespread changes in gene regulation, which is associated with its nuclear localization. To begin to understand how TG2 impacts astrocytic function, we used a neuron-astrocyte co-culture paradigm to compare the effects of TG2−/− and wild-type (WT) mouse astrocytes on neurite outgrowth and synapse formation. Neurons were grown on a control substrate or an injury-simulating matrix comprised of inhibitory chondroitin sulfate proteoglycans (CSPGs). Compared to WT astrocytes, TG2−/− astrocytes supported neurite outgrowth to a significantly greater extent only on the CSPG matrix, while synapse formation assays showed mixed results depending on the pre- and post-synaptic markers analyzed. We hypothesize that TG2 regulates the supportive functions of astrocytes in injury conditions by modulating gene expression through interactions with transcription factors and transcription complexes. Based on the results of a previous yeast two-hybrid screen for TG2 interactors, we further investigated the interaction of TG2 with Zbtb7a, a ubiquitously expressed transcription factor. Co-immunoprecipitation and colocalization analyses confirmed the interaction of TG2 and Zbtb7a in the nucleus of astrocytes. Overexpression or knockdown of Zbtb7a levels in WT and TG2−/− ...
Keywords	transglutaminase 2 ; astrocytes ; neurons ; neurite outgrowth ; CNS injury ; Zbtb7a ; Biology (General) ; QH301-705.5 ; Chemistry ; QD1-999
Subject code	571
Language	English
Publishing date	2023-03-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Author Correction

Shon A. Koren / Nada Ahmed Selim / Lizbeth De la Rosa / Jacob Horn / M. Arsalan Farooqi / Alicia Y. Wei / Annika Müller-Eigner / Jacen Emerson / Gail V. W. Johnson / Andrew P. Wojtovich

Nature Communications, Vol 14, Iss 1, Pp 1-

All-optical spatiotemporal mapping of ROS dynamics across mitochondrial microdomains in situ

2023 Volume 1

Keywords	Science ; Q
Language	English
Publishing date	2023-12-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: All-optical spatiotemporal mapping of ROS dynamics across mitochondrial microdomains in situ

Shon A. Koren / Nada Ahmed Selim / Lizbeth De la Rosa / Jacob Horn / M. Arsalan Farooqi / Alicia Y. Wei / Annika Müller-Eigner / Jacen Emerson / Gail V. W. Johnson / Andrew P. Wojtovich

Nature Communications, Vol 14, Iss 1, Pp 1-

2023 Volume 16

Abstract: Abstract Hydrogen peroxide (H2O2) functions as a second messenger to signal metabolic distress through highly compartmentalized production in mitochondria. The dynamics of reactive oxygen species (ROS) generation and diffusion between mitochondrial ... ...

Abstract	Abstract Hydrogen peroxide (H2O2) functions as a second messenger to signal metabolic distress through highly compartmentalized production in mitochondria. The dynamics of reactive oxygen species (ROS) generation and diffusion between mitochondrial compartments and into the cytosol govern oxidative stress responses and pathology, though these processes remain poorly understood. Here, we couple the H2O2 biosensor, HyPer7, with optogenetic stimulation of the ROS-generating protein KillerRed targeted into multiple mitochondrial microdomains. Single mitochondrial photogeneration of H2O2 demonstrates the spatiotemporal dynamics of ROS diffusion and transient hyperfusion of mitochondria due to ROS. This transient hyperfusion phenotype required mitochondrial fusion but not fission machinery. Measurement of microdomain-specific H2O2 diffusion kinetics reveals directionally selective diffusion through mitochondrial microdomains. All-optical generation and detection of physiologically-relevant concentrations of H2O2 between mitochondrial compartments provide a map of mitochondrial H2O2 diffusion dynamics in situ as a framework to understand the role of ROS in health and disease.
Keywords	Science ; Q
Language	English
Publishing date	2023-09-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Tau clearance mechanisms and their possible role in the pathogenesis of Alzheimer disease

GailV.W.Johnson

Frontiers in Neurology, Vol

2013 Volume 4

Abstract: One of the defining pathological features of Alzheimer disease (AD) is the intraneuronal accumulation of tau. Tau that forms these accumulations is altered both posttranslationally and conformationally, and there is now significant evidence that soluble ... ...

Abstract	One of the defining pathological features of Alzheimer disease (AD) is the intraneuronal accumulation of tau. Tau that forms these accumulations is altered both posttranslationally and conformationally, and there is now significant evidence that soluble forms of these modified tau species are the toxic entities rather than the insoluble neurofibrillary tangles (NFTs). However there is still noteworthy debate concerning which specific pathological forms of tau are the contributors to the neuronal dysfunction and death in AD. Nonetheless, given that increases in aberrant forms of tau play a role in the neurodegeneration process in AD, there is growing interest in understanding the degradative pathways that remove tau from the cell, and the selectivity of these different pathways for these various forms of tau. Indeed, one can speculate that deficits in a pathway that selectively removes certain pathological forms of tau could play a pivotal role in AD. In this review we will discuss the different proteolytic and degradative machineries that may be involved in removing tau from the cell. How deficits in these different degradative pathways may contribute to abnormal accumulation of tau in AD will also be considered. In addition, the issue of the selective targeting of specific tau species to a given degradative pathway for clearance from the cell will be addressed.
Keywords	Autophagy ; Proteolysis ; tau ; degradation ; Proteasome ; Neurology. Diseases of the nervous system ; RC346-429 ; Neurosciences. Biological psychiatry. Neuropsychiatry ; RC321-571 ; Internal medicine ; RC31-1245 ; Medicine ; R
Subject code	571
Language	English
Publishing date	2013-09-01T00:00:00Z
Publisher	Frontiers
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Deletion or Inhibition of Astrocytic Transglutaminase 2 Promotes Functional Recovery after Spinal Cord Injury

Anissa Elahi / Jacen Emerson / Jacob Rudlong / Jeffrey W. Keillor / Garrick Salois / Adam Visca / Peter Girardi / Gail V.W. Johnson / Christoph Pröschel

Cells, Vol 10, Iss 2942, p

2021 Volume 2942

Abstract: Following CNS injury, astrocytes become “reactive” and exhibit pro-regenerative or harmful properties. However, the molecular mechanisms that cause astrocytes to adopt either phenotype are not well understood. Transglutaminase 2 (TG2) plays a key role in ...

Abstract	Following CNS injury, astrocytes become “reactive” and exhibit pro-regenerative or harmful properties. However, the molecular mechanisms that cause astrocytes to adopt either phenotype are not well understood. Transglutaminase 2 (TG2) plays a key role in regulating the response of astrocytes to insults. Here, we used mice in which TG2 was specifically deleted in astrocytes ( Gfap -Cre+/− TG2 fl/fl, referred to here as TG2-A-cKO) in a spinal cord contusion injury (SCI) model. Deletion of TG2 from astrocytes resulted in a significant improvement in motor function following SCI. GFAP and NG2 immunoreactivity, as well as number of SOX9 positive cells, were significantly reduced in TG2-A-cKO mice. RNA-seq analysis of spinal cords from TG2-A-cKO and control mice 3 days post-injury identified thirty-seven differentially expressed genes, all of which were increased in TG2-A-cKO mice. Pathway analysis revealed a prevalence for fatty acid metabolism, lipid storage and energy pathways, which play essential roles in neuron–astrocyte metabolic coupling. Excitingly, treatment of wild type mice with the selective TG2 inhibitor VA4 significantly improved functional recovery after SCI, similar to what was observed using the genetic model. These findings indicate the use of TG2 inhibitors as a novel strategy for the treatment of SCI and other CNS injuries.
Keywords	transglutaminase 2 ; spinal cord injury ; astrocytes ; regeneration ; GFAP ; SOX9 ; Biology (General) ; QH301-705.5
Subject code	572
Language	English
Publishing date	2021-10-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Inhibition or ablation of transglutaminase 2 impairs astrocyte migration

Monteagudo, Alina / Changyi Ji / Abdullah Akbar / Jeffrey W. Keillor / Gail V.W. Johnson

Biochemical and biophysical research communications. 2017 Jan. 22, v. 482

2017

Abstract: Astrocytes play numerous complex roles that support and facilitate the function of neurons. Further, when there is an injury to the central nervous system (CNS) they can both facilitate or ameliorate functional recovery depending on the location and ... ...

Abstract	Astrocytes play numerous complex roles that support and facilitate the function of neurons. Further, when there is an injury to the central nervous system (CNS) they can both facilitate or ameliorate functional recovery depending on the location and severity of the injury. When a CNS injury is relatively severe a glial scar is formed, which is primarily composed of astrocytes. The glial scar can be both beneficial, by limiting inflammation, and detrimental, by preventing neuronal projections, to functional recovery. Thus, understanding the processes and proteins that regulate astrocyte migration in response to injury is still of fundamental importance. One protein that is likely involved in astrocyte migration is transglutaminase 2 (TG2); a multifunctional protein expressed ubiquitously throughout the brain. Its functions include transamidation and GTPase activity, among others, and previous studies have implicated TG2 as a regulator of migration. Therefore, we examined the role of TG2 in primary astrocyte migration subsequent to injury. Using wild type or TG2â/â astrocytes, we manipulated the different functions and conformation of TG2 with novel irreversible inhibitors or mutant versions of the protein. Results showed that both inhibition and ablation of TG2 in primary astrocytes significantly inhibit migration. Additionally, we show that the deficiency in migration caused by deletion of TG2 can only be rescued with the native protein and not with mutants. Finally, the addition of TGFÎ² rescued the migration deficiency independent of TG2. Taken together, our study shows that transamidation and GTP/GDP-binding are necessary for inhibiting astrocyte migration and it is TGFÎ² independent.
Keywords	astrocytes ; brain ; guanosinetriphosphatase ; inflammation ; mutants ; neurons ; protein-glutamine gamma-glutamyltransferase ; proteins ; transforming growth factor beta
Language	English
Dates of publication	2017-0122
Size	p. 942-947.
Publishing place	Elsevier Inc.
Document type	Article
ZDB-ID	205723-2
ISSN	0006-291X ; 0006-291X
ISSN (online)	0006-291X
ISSN	0006-291X
DOI	10.1016/j.bbrc.2016.11.137
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Differential modulation of TCF/LEF-1 activity by the soluble LRP6-ICD.

Brandon Beagle / Gail V W Johnson

PLoS ONE, Vol 5, Iss 7, p e

2010 Volume 11821

Abstract: The canonical Wnt/beta-catenin (Wnt) pathway is a master transcriptional regulatory signaling pathway that controls numerous biological processes including proliferation and differentiation. As such, transcriptional activity of the Wnt pathway is tightly ...

Abstract	The canonical Wnt/beta-catenin (Wnt) pathway is a master transcriptional regulatory signaling pathway that controls numerous biological processes including proliferation and differentiation. As such, transcriptional activity of the Wnt pathway is tightly regulated and/or modulated by numerous proteins at the level of the membrane, cytosol and/or nucleus. In the nucleus, transcription of Wnt target genes by TCF/LEF-1 is repressed by the long Groucho/TLE co-repressor family. However, a truncated member of the Groucho/TLE family, amino terminal enhancer of Split (AES) can positively modulate TCF/LEF-1 activity by antagonizing long Groucho/TLE members in a dominant negative manner. We have previously shown the soluble intracellular domain of the LRP6 receptor, a receptor required for activation of the Wnt pathway, can positively regulate transcriptional activity within the Wnt pathway. In the current study, we show the soluble LRP6 intracellular domain (LRP6-ICD) can also translocate to the nucleus in CHO and HEK 293T cells and in contrast to cytosolic LRP6-ICD; nuclear LRP6-ICD represses TCF/LEF-1 activity. In agreement with previous reports, we show AES enhances TCF/LEF-1 mediated reporter transcription and further we demonstrate that AES activity is spatially regulated in HEK 293T cells. LRP6-ICD interacts with AES exclusively in the nucleus and represses AES mediated TCF/LEF-1 reporter transcription. These results suggest that LRP6-ICD can differentially modulate Wnt pathway transcriptional activity depending upon its subcellular localization and differential protein-protein interactions.
Keywords	Medicine ; R ; Science ; Q
Subject code	570
Language	English
Publishing date	2010-07-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Intracellular localization and conformational state of transglutaminase 2

Soner Gundemir / Gail V W Johnson

PLoS ONE, Vol 4, Iss 7, p e

implications for cell death.

2009 Volume 6123

Abstract: Transglutaminase 2 (TG2) is a multifunctional enzyme that has guanine nucleotide binding and GTP hydrolyzing activity in addition to its transamidating function. Studies show that TG2 is a player in mediating cell death processes. However, there is far ... ...

Abstract	Transglutaminase 2 (TG2) is a multifunctional enzyme that has guanine nucleotide binding and GTP hydrolyzing activity in addition to its transamidating function. Studies show that TG2 is a player in mediating cell death processes. However, there is far from a consensus about the role of this enzyme in cell death processes as it appears to be dependent upon the cell type, stimuli, subcellular localization and conformational state of the enzyme. The purpose of this study was to dissect the role of TG2 in the cell death processes. To this end, we created and characterized 4 distinct point mutants of TG2, each of which differs from the wild type by its conformation or by lacking an important function. We also prepared these mutants as nuclear targeted proteins. By overexpressing mutant or wild type forms of TG2 in HEK 293 cells, we investigated the modulatory role of the protein in the cell death process in response to three stressors: thapsigargin, hyperosmotic stress and oxygen/glucose deprivation (OGD). All of the TG2 constructs, except the R580A mutant (which cannot bind guanine nucleotides and is therefore more prone to exhibit transamidating activity), either did not significantly affect the cell death processes or were protective. However in the case of the R580A mutant, cell death in response to high thapsigargin concentrations, was significantly increased. Intriguingly, nuclear localization of R580A-TG2 was sufficient to counteract the pro-death role of cytoplasmic R580A-TG2. In addition, nuclear localization of TG2 significantly facilitated its protective role against OGD. Our data support the hypothesis that the transamidation activity of TG2, which is mostly quiescent except in extreme stress conditions, is necessary for its pro-death role. In addition, nuclear localization of TG2 generally plays a key role in its protective function against cell death processes, either counteracting the detrimental effect or strengthening the protective role of the protein.
Keywords	Medicine ; R ; Science ; Q
Subject code	571
Language	English
Publishing date	2009-07-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Cytosolic guanine nucledotide binding deficient form of transglutaminase 2 (R580a) potentiates cell death in oxygen glucose deprivation.

Gozde Colak / Jeffrey W Keillor / Gail V W Johnson

PLoS ONE, Vol 6, Iss 1, p e

2011 Volume 16665

Abstract: Transglutaminase 2 (TG2) is a hypoxia-responsive protein that is a calcium-activated transamidating enzyme, a GTPase and a scaffolding/linker protein. Upon activation TG2 undergoes a large conformational change, which likely affects not only its ... ...

Abstract	Transglutaminase 2 (TG2) is a hypoxia-responsive protein that is a calcium-activated transamidating enzyme, a GTPase and a scaffolding/linker protein. Upon activation TG2 undergoes a large conformational change, which likely affects not only its enzymatic activities but its non-catalytic functions as well. The focus of this study was on the role of transamidating activity, conformation and localization of TG2 in ischemic cell death. Cells expressing a GTP binding deficient form of TG2 (TG2-R580A) with high basal transamidation activity and a more extended conformation showed significantly increased cell death in response to oxygen-glucose deprivation; however, targeting TG2-R580A to the nucleus abrogated its detrimental role in oxygen-glucose deprivation. Treatment of cells expressing wild type TG2, TG2-C277S (a transamidating inactive mutant) and TG2-R580A with Cp4d, a reversible TG2 inhibitor, did not affect cell death in response to oxygen-glucose deprivation. These findings indicate that the pro-cell death effects of TG2 are dependent on its localization to the cytosol and independent of its transamidation activity. Further, the conformational state of TG2 is likely an important determinant in cell survival and the prominent function of TG2 in ischemic cell death is as a scaffold to modulate cellular processes.
Keywords	Medicine ; R ; Science ; Q
Language	English
Publishing date	2011-01-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Metabolic state determines sensitivity to cellular stress in Huntington disease

Youngnam N Jin / Woong Y Hwang / Chulman Jo / Gail V W Johnson

PLoS ONE, Vol 7, Iss 1, p e

normalization by activation of PPARγ.

2012 Volume 30406

Abstract: Impairments in mitochondria and transcription are important factors in the pathogenesis of Huntington disease (HD), a neurodegenerative disease caused by a polyglutamine expansion in the huntingtin protein. This study investigated the effect of different ...

Abstract	Impairments in mitochondria and transcription are important factors in the pathogenesis of Huntington disease (HD), a neurodegenerative disease caused by a polyglutamine expansion in the huntingtin protein. This study investigated the effect of different metabolic states and peroxisome proliferator-activated receptor γ (PPARγ) activation on sensitivity to cellular stressors such as H(2)O(2) or thapsigargin in HD. Striatal precursor cells expressing wild type (STHdh(Q7)) or mutant huntingtin (STHdh(Q111)) were prepared in different metabolic conditions (glucose vs. pyruvate). Due to the fact that STHdh(Q111) cells exhibit mitochondrial deficits, we expected that in the pyruvate condition, where ATP is generated primarily by the mitochondria, there would be greater differences in cell death between the two cell types compared to the glucose condition. Intriguingly, it was the glucose condition that gave rise to greater differences in cell death. In the glucose condition, thapsigargin treatment resulted in a more rapid loss of mitochondrial membrane potential (ΔΨm), a greater activation of caspases (3, 8, and 9), and a significant increase in superoxide/reactive oxygen species (ROS) in STHdh(Q111) compared to STHdh(Q7), while both cell types showed similar kinetics of ΔΨm-loss and similar levels of superoxide/ROS in the pyruvate condition. This suggests that bioenergetic deficiencies are not the primary contributor to the enhanced sensitivity of STHdh(Q111) cells to stressors compared to the STHdh(Q7) cells. PPARγ activation significantly attenuated thapsigargin-induced cell death, concomitant with an inhibition of caspase activation, a delay in ΔΨm loss, and a reduction of superoxide/ROS generation in STHdh(Q111) cells. Expression of mutant huntingtin in primary neurons induced superoxide/ROS, an effect that was significantly reduced by constitutively active PPARγ. These results provide significant insight into the bioenergetic disturbances in HD with PPARγ being a potential therapeutic target for HD.
Keywords	Medicine ; R ; Science ; Q
Subject code	570
Language	English
Publishing date	2012-01-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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