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Xu Q, Zhao J, Guo Y, Liu M, Schinckel AP, Zhou B. A Single-Nucleotide Polymorphism in the Promoter of Porcine ARHGAP24 Gene Regulates Aggressive Behavior of Weaned Pigs After Mixing by Affecting the Binding of Transcription Factor p53. Front Cell Dev Biol 2022; 10:839583. [PMID: 35433684 PMCID: PMC9010951 DOI: 10.3389/fcell.2022.839583] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 02/28/2022] [Indexed: 11/18/2022] Open
Abstract
Pigs are important biomedical model animals for the study of human neurological diseases. Similar to human aggressive behavior in children and adolescents, weaned pigs also show more aggressive behavior after mixing, which has negative effects on animal welfare and growth performance. The identification of functional single-nucleotide polymorphisms (SNPs) related to the aggressive behavior of pigs would provide valuable molecular markers of the aggressive behavioral trait for genetic improvement program. The Rho GTPase–activating protein 24 (ARHGAP24) gene plays an important role in regulating the process of axon guidance, which may impact the aggressive behavior of pigs. By resequencing the entire coding region, partially adjacent introns and the 5′ and 3′ flanking regions, six and four SNPs were identified in the 5′ flanking region and 5′ untranslated region (UTR) of the porcine ARHGAP24 gene, respectively. Association analyses revealed that nine SNPs were significantly associated with aggressive behavioral traits (p = < 1.00 × 10–4–4.51 × 10–2), and their haplotypes were significantly associated with aggressive behavior (p = < 1.00 × 10–4–2.99 × 10–2). The core promoter region of the ARHGAP24 gene has been identified between −670 and −1,113 bp. Furthermore, the luciferase activity of allele A of rs335052970 was significantly less than that of allele G, suggesting that the transcriptional activity of the ARHGAP24 gene was inhibited by allele A of rs335052970. It was identified that the transcription factor p53 bound to the transcription factor binding sites (TFBSs) containing allele A of rs335052970. In porcine primary neural cells, p53 binds to the target promoter region of the ARHGAP24 gene, reduces its promoter transcriptional activity, and then reduces its messenger RNA (mRNA) and protein expression. The results demonstrated that the ARHGAP24 gene had significant genetic effects on aggressive behavioral traits of pigs. Therefore, rs335052970 in the ARHGAP24 gene can be used as a molecular marker to select the less aggressive pigs.
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Affiliation(s)
- Qinglei Xu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Jing Zhao
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Yanli Guo
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Mingzheng Liu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Allan P. Schinckel
- Department of Animal Sciences, Purdue University, West Lafayette, IN, United States
| | - Bo Zhou
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
- *Correspondence: Bo Zhou,
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Dupraz S, Hilton BJ, Husch A, Santos TE, Coles CH, Stern S, Brakebusch C, Bradke F. RhoA Controls Axon Extension Independent of Specification in the Developing Brain. Curr Biol 2019; 29:3874-3886.e9. [PMID: 31679934 DOI: 10.1016/j.cub.2019.09.040] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 08/22/2019] [Accepted: 09/16/2019] [Indexed: 12/22/2022]
Abstract
The specification of an axon and its subsequent outgrowth are key steps during neuronal polarization, a prerequisite to wire the brain. The Rho-guanosine triphosphatase (GTPase) RhoA is believed to be a central player in these processes. However, its physiological role has remained undefined. Here, genetic loss- and gain-of-function experiments combined with time-lapse microscopy, cell culture, and in vivo analysis show that RhoA is not involved in axon specification but confines the initiation of neuronal polarization and axon outgrowth during development. Biochemical analysis and super-resolution microscopy together with molecular and pharmacological manipulations reveal that RhoA restrains axon growth by activating myosin-II-mediated actin arc formation in the growth cone to prevent microtubules from protruding toward the leading edge. Through this mechanism, RhoA regulates the duration of axon growth and pause phases, thus controlling the tightly timed extension of developing axons. Thereby, this work unravels physiologically relevant players coordinating actin-microtubule interactions during axon growth.
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Affiliation(s)
- Sebastian Dupraz
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Brett J Hilton
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Andreas Husch
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Telma E Santos
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Charlotte H Coles
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Sina Stern
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Cord Brakebusch
- Biotech Research & Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen, Denmark
| | - Frank Bradke
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany.
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Rho GTPases in the Physiology and Pathophysiology of Peripheral Sensory Neurons. Cells 2019; 8:cells8060591. [PMID: 31208035 PMCID: PMC6627758 DOI: 10.3390/cells8060591] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 12/13/2022] Open
Abstract
Numerous experimental studies demonstrate that the Ras homolog family of guanosine triphosphate hydrolases (Rho GTPases) Ras homolog family member A (RhoA), Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division cycle 42 (Cdc42) are important regulators in somatosensory neurons, where they elicit changes in the cellular cytoskeleton and are involved in diverse biological processes during development, differentiation, survival and regeneration. This review summarizes the status of research regarding the expression and the role of the Rho GTPases in peripheral sensory neurons and how these small proteins are involved in development and outgrowth of sensory neurons, as well as in neuronal regeneration after injury, inflammation and pain perception. In sensory neurons, Rho GTPases are activated by various extracellular signals through membrane receptors and elicit their action through a wide range of downstream effectors, such as Rho-associated protein kinase (ROCK), phosphoinositide 3-kinase (PI3K) or mixed-lineage kinase (MLK). While RhoA is implicated in the assembly of stress fibres and focal adhesions and inhibits neuronal outgrowth through growth cone collapse, Rac1 and Cdc42 promote neuronal development, differentiation and neuroregeneration. The functions of Rho GTPases are critically important in the peripheral somatosensory system; however, their signalling interconnections and partially antagonistic actions are not yet fully understood.
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Tang J, Yu Y, Zheng H, Yin L, Sun M, Wang W, Cui J, Liu W, Xie X, Chen F. ITRAQ-based quantitative proteomic analysis of Cynops orientalis limb regeneration. BMC Genomics 2017; 18:750. [PMID: 28938871 PMCID: PMC5610437 DOI: 10.1186/s12864-017-4125-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 09/06/2017] [Indexed: 02/06/2023] Open
Abstract
Background Salamanders regenerate their limbs after amputation. However, the molecular mechanism of this unique regeneration remains unclear. In this study, isobaric tags for relative and absolute quantification (iTRAQ) coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS) was employed to quantitatively identify differentially expressed proteins in regenerating limbs 3, 7, 14, 30 and 42 days post amputation (dpa). Results Of 2636 proteins detected in total, 253 proteins were differentially expressed during different regeneration stages. Among these proteins, Asporin, Cadherin-13, Keratin, Collagen alpha-1(XI) and Titin were down-regulated. CAPG, Coronin-1A, AnnexinA1, Cathepsin B were up-regulated compared with the control. The identified proteins were further analyzed to obtain information about their expression patterns and functions in limb regeneration. Functional analysis indicated that the differentially expressed proteins were associated with wound healing, immune response, cellular process, metabolism and binding. Conclusions This work indicated that significant proteome alternations occurred during salamander limb regeneration. The results may provide fundamental knowledge to understand the mechanism of limb regeneration. Electronic supplementary material The online version of this article (10.1186/s12864-017-4125-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jie Tang
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.,Shaanxi Institute of Zoology, 88 Xingqing Road, Xi'an, Shaanxi Province, 710032, People's Republic of China
| | - Yuan Yu
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China
| | - Hanxue Zheng
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China
| | - Lu Yin
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China
| | - Mei Sun
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China
| | - Wenjun Wang
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China
| | - Jihong Cui
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China
| | - Wenguang Liu
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China
| | - Xin Xie
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China. .,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.
| | - Fulin Chen
- Lab of Tissue Engineering, Faculty of Life Science, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China. .,Provincial Key Laboratory of Biotechnology of Shaanxi, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China. .,Key Laboratory of Resource Biology and Modern Biotechnology in Western China, Ministry of Education, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi Province, 710069, People's Republic of China.
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Neto E, Alves CJ, Leitão L, Sousa DM, Alencastre IS, Conceição F, Lamghari M. Axonal outgrowth, neuropeptides expression and receptors tyrosine kinase phosphorylation in 3D organotypic cultures of adult dorsal root ganglia. PLoS One 2017; 12:e0181612. [PMID: 28742111 PMCID: PMC5524368 DOI: 10.1371/journal.pone.0181612] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 07/05/2017] [Indexed: 12/27/2022] Open
Abstract
Limited knowledge from mechanistic studies on adult sensory neuronal activity was generated, to some extent, in recapitulated adult in vivo 3D microenvironment. To fill this gap there is a real need to better characterize the adult dorsal root ganglia (aDRG) organotypic cultures to make these in vitro systems exploitable for different approaches, ranging from basic neurobiology to regenerative therapies, to address the sensory nervous system in adult stage. We conducted a direct head-to-head comparison of aDRG and embryonic DRG (eDRG) organotypic culture focusing on axonal growth, neuropeptides expression and receptors tyrosine kinase (RTK) activation associated with neuronal survival, proliferation and differentiation. To identify alterations related to culture conditions, these parameters were also addressed in retrieved aDRG and eDRG and compared with organotypic cultures. Under similar neurotrophic stimulation, aDRG organotypic cultures displayed lower axonal outgrowth rate supported by reduced expression of growth associated protein-43 and high levels of RhoA and glycogen synthase kinase 3 beta mRNA transcripts. In addition, differential alteration in sensory neuropeptides expression, namely calcitonin gene-related peptide and substance P, was detected and was mainly pronounced at gene expression levels. Among 39 different RTK, five receptors from three RTK families were emphasized: tropomyosin receptor kinase A (TrkA), epidermal growth factor receptors (EGFR, ErbB2 and ErbB3) and platelet-derived growth factor receptor (PDGFR). Of note, except for EGFR, the phosphorylation of these receptors was dependent on DRG developmental stage and/or culture condition. In addition, EGFR and PDGFR displayed alterations in their cellular expression pattern in cultured DRG. Overall we provided valuable information particularly important when addressing in vitro the molecular mechanisms associated with development, maturation and regeneration of the sensory nervous system.
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Affiliation(s)
- Estrela Neto
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- INEB—Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
- FMUP—Faculdade de Medicina da Universidade do Porto, Porto, Portugal
| | - Cecília J. Alves
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- INEB—Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
| | - Luís Leitão
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- INEB—Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
- ICBAS—Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Daniela M. Sousa
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- INEB—Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
| | - Inês S. Alencastre
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- INEB—Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
| | - Francisco Conceição
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- INEB—Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
| | - Meriem Lamghari
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- INEB—Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
- ICBAS—Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- * E-mail:
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Zhou X, Zheng Y. Cell type-specific signaling function of RhoA GTPase: lessons from mouse gene targeting. J Biol Chem 2013; 288:36179-88. [PMID: 24202176 DOI: 10.1074/jbc.r113.515486] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
RhoA GTPase is a key intracellular regulator of actomyosin dynamics and other cell functions, including adhesion, proliferation, survival, and gene expression. Most of our knowledge of RhoA signaling function is from studies in immortalized cell lines utilizing inhibitors or dominant mutant overexpression, both of which are limited in terms of specificity, dosage, and clonal variation. Recent mouse gene targeting studies of rhoA and its regulators/effectors have revealed cell type-specific signaling mechanisms in the context of mammalian physiology. The new knowledge may present therapeutic opportunities for the rational targeting of RhoA signaling-mediated pathophysiologies.
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Affiliation(s)
- Xuan Zhou
- From the Division of Experimental Hematology and Cancer Biology, Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, Ohio 45229
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7
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Katayama KI, Imai F, Campbell K, Lang RA, Zheng Y, Yoshida Y. RhoA and Cdc42 are required in pre-migratory progenitors of the medial ganglionic eminence ventricular zone for proper cortical interneuron migration. Development 2013; 140:3139-45. [PMID: 23861058 DOI: 10.1242/dev.092585] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Cortical interneurons arise from the ganglionic eminences in the ventral telencephalon and migrate tangentially to the cortex. Although RhoA and Cdc42, members of the Rho family of small GTPases, have been implicated in regulating neuronal migration, their respective roles in the tangential migration of cortical interneurons remain unknown. Here we show that loss of RhoA and Cdc42 in the ventricular zone (VZ) of the medial ganglionic eminence (MGE) using Olig2-Cre mice causes moderate or severe defects in the migration of cortical interneurons, respectively. Furthermore, RhoA- or Cdc42-deleted MGE cells exhibit impaired migration in vitro. To determine whether RhoA and Cdc42 directly regulate the motility of cortical interneurons during migration, we deleted RhoA and Cdc42 in the subventricular zone (SVZ), where more fate-restricted progenitors are located within the ganglionic eminences, using Dlx5/6-Cre-ires-EGFP (Dlx5/6-CIE) mice. Deletion of either gene within the SVZ does not cause any obvious defects in cortical interneuron migration, indicating that cell motility is not dependent upon RhoA or Cdc42. These findings provide genetic evidence that RhoA and Cdc42 are required in progenitors of the MGE in the VZ, but not the SVZ, for proper cortical interneuron migration.
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Affiliation(s)
- Kei-ichi Katayama
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
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The small GTPase RhoA is required for proper locomotor circuit assembly. PLoS One 2013; 8:e67015. [PMID: 23825607 PMCID: PMC3692541 DOI: 10.1371/journal.pone.0067015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 05/13/2013] [Indexed: 11/19/2022] Open
Abstract
The assembly of neuronal circuits during development requires the precise navigation of axons, which is controlled by attractive and repulsive guidance cues. In the developing spinal cord, ephrinB3 functions as a short-range repulsive cue that prevents EphA4 receptor-expressing corticospinal tract and spinal interneuron axons from crossing the midline, ensuring proper formation of locomotor circuits. Here we report that the small GTPase RhoA, a key regulator of cytoskeletal dynamics, is also required for ephrinB3/EphA4-dependent locomotor circuit formation. Deletion of RhoA from neural progenitor cells results in mice that exhibit a rabbit-like hopping gait, which phenocopies mice lacking ephrinB3 or EphA4. Consistent with this locomotor defect, we found that corticospinal tract axons and spinal interneuron projections from RhoA-deficient mice aberrantly cross the spinal cord midline. Furthermore, we determined that loss of RhoA blocks ephrinB3-induced growth cone collapse of cortical axons and disrupts ephrinB3 expression at the spinal cord midline. Collectively, our results demonstrate that RhoA is essential for the ephrinB3/EphA4-dependent assembly of cortical and spinal motor circuits that control normal locomotor behavior.
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Weiner JA, Jontes JD, Burgess RW. Introduction to mechanisms of neural circuit formation. Front Mol Neurosci 2013; 6:12. [PMID: 23717261 PMCID: PMC3652293 DOI: 10.3389/fnmol.2013.00012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 04/26/2013] [Indexed: 12/28/2022] Open
Affiliation(s)
- Joshua A Weiner
- Department of Biology, University of Iowa Iowa City, IA, USA
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Auer M, Schweigreiter R, Hausott B, Thongrong S, Höltje M, Just I, Bandtlow C, Klimaschewski L. Rho-independent stimulation of axon outgrowth and activation of the ERK and Akt signaling pathways by C3 transferase in sensory neurons. Front Cell Neurosci 2012; 6:43. [PMID: 23087613 PMCID: PMC3468917 DOI: 10.3389/fncel.2012.00043] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 09/23/2012] [Indexed: 11/15/2022] Open
Abstract
Peripheral nerve injury triggers the activation of RhoA in spinal motor and peripheral sensory neurons. RhoA activates a number of effector proteins including the Rho-associated kinase, ROCK, which targets the cytoskeleton and leads to inhibition of neurite outgrowth. Blockade of the Rho/ROCK pathway by pharmacological means improves axon regeneration after experimental injury. C3bot transferase, an exoenzyme produced by Clostridium botulinum, inactivates RhoA by ADP-ribosylation. It has been successfully applied in experimental CNS lesions to facilitate axon regeneration. Up to now it was not investigated thoroughly whether C3bot exerts positive effects on peripheral axon regeneration as well. In the present study, recombinant membrane permeable C3bot produced a small, but significant, axon outgrowth effect on peripheral sensory neurons dissociated from adult dorsal root ganglia (DRG) of the rat. Neuronal overexpression of C3, however, did not enhance axonal growth. Moreover, transfection of plasmids encoding dominant negative RhoA or RhoA specific shRNAs failed to increase axonal growth. Furthermore, we show that the C3bot mutant, C3E174Q, which lacks RhoA inhibitory activity, still stimulates axonal growth. When analyzing possible signaling mechanisms we found that extracellular signal-regulated kinase (ERK) and Akt are activated by C3bot and ERK is induced by the C3E174Q mutant. Upregulation of kinase activities by C3bot occurs significantly faster than inactivation of RhoA indicating a RhoA-independent pathway of action by C3bot. The induction of ERK signaling by C3bot was detected in embryonic hippocampal neurons, too. Taken together, although RhoA plays a central role for inhibition of axon outgrowth by myelin-derived inhibitors, it does not interfere with axonal growth of sensory neurons on a permissive substrate in vitro. C3bot blocks neuronal RhoA activity, but its positive effects on axon elongation and branching appear to be mediated by Rho independent mechanisms involving activation of axon growth promoting ERK and Akt kinases.
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Affiliation(s)
- Maria Auer
- Division of Neuroanatomy, Innsbruck Medical University Innsbruck, Austria
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