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Serebryannyy LA, Yuen M, Parilla M, Cooper ST, de Lanerolle P. The Effects of Disease Models of Nuclear Actin Polymerization on the Nucleus. Front Physiol 2016; 7:454. [PMID: 27774069 PMCID: PMC5053997 DOI: 10.3389/fphys.2016.00454] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 09/21/2016] [Indexed: 01/09/2023] Open
Abstract
Actin plays a crucial role in regulating multiple processes within the nucleus, including transcription and chromatin organization. However, the polymerization state of nuclear actin remains controversial, and there is no evidence for persistent actin filaments in a normal interphase nucleus. Further, several disease pathologies are characterized by polymerization of nuclear actin into stable filaments or rods. These include filaments that stain with phalloidin, resulting from point mutations in skeletal α-actin, detected in the human skeletal disease intranuclear rod myopathy, and cofilin/actin rods that form in response to cellular stressors like heatshock. To further elucidate the effects of these pathological actin structures, we examined the nucleus in both cell culture models as well as isolated human tissues. We find these actin structures alter the distribution of both RNA polymerase II and chromatin. Our data suggest that nuclear actin filaments result in disruption of nuclear organization, which may contribute to the disease pathology.
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Affiliation(s)
- Leonid A Serebryannyy
- Department of Physiology and Biophysics, University of Illinois at Chicago Chicago, IL, USA
| | - Michaela Yuen
- Institute for Neuroscience and Muscle Research, Kids Research Institute, The Children's Hospital at WestmeadSydney, NSW, Australia; Faculty of Medicine, Discipline of Pediatrics and Child Health, University of SydneySydney, NSW, Australia
| | - Megan Parilla
- Department of Physiology and Biophysics, University of Illinois at Chicago Chicago, IL, USA
| | - Sandra T Cooper
- Institute for Neuroscience and Muscle Research, Kids Research Institute, The Children's Hospital at WestmeadSydney, NSW, Australia; Faculty of Medicine, Discipline of Pediatrics and Child Health, University of SydneySydney, NSW, Australia
| | - Primal de Lanerolle
- Department of Physiology and Biophysics, University of Illinois at Chicago Chicago, IL, USA
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Yang J, Wu C, Stefanescu I, Jakobsson L, Chervoneva I, Horowitz A. RhoA inhibits neural differentiation in murine stem cells through multiple mechanisms. Sci Signal 2016; 9:ra76. [PMID: 27460990 DOI: 10.1126/scisignal.aaf0791] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Spontaneous neural differentiation of embryonic stem cells is induced by Noggin-mediated inhibition of bone morphogenetic protein 4 (BMP4) signaling. RhoA is a guanosine triphosphatase (GTPase) that regulates cytoskeletal dynamics and gene expression, both of which control stem cell fate. We found that disruption of Syx, a gene encoding a RhoA-specific guanine nucleotide exchange factor, accelerated retinoic acid-induced neural differentiation in murine embryonic stem cells aggregated into embryoid bodies. Cells from Syx(+/+) and Syx(-/-) embryoid bodies had different abundances of proteins implicated in stem cell pluripotency. The differentiation-promoting proteins Noggin and RARγ (a retinoic acid receptor) were more abundant in cells of Syx(-/-) embryoid bodies, whereas the differentiation-suppressing proteins SIRT1 (a protein deacetylase) and the phosphorylated form of SMAD1 (the active form of this transcription factor) were more abundant in cells of Syx(+/+) embryoid bodies. These differences were blocked by the overexpression of constitutively active RhoA, indicating that the abundance of these proteins was maintained, at least in part, by RhoA activity. The peripheral stress fibers in cells from Syx(-/-) embryoid bodies were thinner than those in Syx(+/+) cells. Furthermore, less Noggin and fewer vesicles containing Rab3d, a GTPase that mediates Noggin trafficking, were detected in cells from Syx(-/-) embryoid bodies, which could result from increased Noggin exocytosis. These results suggested that, in addition to inhibiting Noggin transcription, RhoA activity in wild-type murine embryonic stem cells also prevented neural differentiation by limiting Noggin secretion.
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Affiliation(s)
- Junning Yang
- Cardeza Foundation for Hematologic Research, Department of Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Chuanshen Wu
- Department of Molecular Cardiology, Cleveland Clinic Foundation, Cleveland, OH 44195, USA
| | - Ioana Stefanescu
- Cardeza Foundation for Hematologic Research, Department of Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Lars Jakobsson
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm 17177, Sweden
| | - Inna Chervoneva
- Division of Biostatistics, Department of Pharmacology and Experimental Therapeutics, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Arie Horowitz
- Cardeza Foundation for Hematologic Research, Department of Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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Tang W, Cai P, Huo W, Li H, Tang J, Zhu D, Xie H, Chen P, Hang B, Wang S, Xia Y. Suppressive action of miRNAs to ARP2/3 complex reduces cell migration and proliferation via RAC isoforms in Hirschsprung disease. J Cell Mol Med 2016; 20:1266-75. [PMID: 26991540 PMCID: PMC4929290 DOI: 10.1111/jcmm.12799] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Accepted: 12/22/2015] [Indexed: 01/05/2023] Open
Abstract
Hirschsprung disease (HSCR) is a congenital disorder caused by the defective function of the embryonic enteric neural crest. The impaired migration of embryonic enteric neural crest plays an important role in the pathogenesis of this disease. Recent studies showed that the ARP2/3 complex and RAC isoforms had effects on actin cytoskeleton remodelling, which contributes to migration. Moreover, some regulatory relationships were identified between ARP2/3 complex and RAC isoforms. Although microRNAs (miRNAs) have been known to modulate target gene expression on the post-transcriptional level, little is known about the regulation among miRNAs, ARP2/3 complex and RAC isoforms. Here, we report that down-regulation of ARP2 and ARP3, two main subunits of ARP2/3 complex, suppressed migration and proliferation in 293T and SH-SY5Y cell lines via the inhibition of RAC1 and RAC2. Meanwhile, as the target genes, ARP2 and ARP3 are reduced by increased miR-24-1* and let-7a*, respectively, in 70 HSCR samples as compared with 74 normal controls. Co-immunoprecipitation showed that aberrant reduction in ARP2 and ARP3 could weaken the function of ARP2/3 complex. Our study demonstrates that the miR-24-1*/let-7a*-ARP2/3 complex-RAC isoforms pathway may represent a novel pathogenic mechanism for HSCR.
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Affiliation(s)
- Weibing Tang
- Department of Pediatric Surgery, Nanjing Children's Hospital Affiliated Nanjing Medical University, Nanjing, China
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Peng Cai
- Children's Hospital of Soochow University, Soochow, China
| | - Weiwei Huo
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University), Ministry of Education, Nanjing, China
| | - Hongxing Li
- Department of Pediatric Surgery, Nanjing Children's Hospital Affiliated Nanjing Medical University, Nanjing, China
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Junwei Tang
- Department of Pediatric Surgery, Nanjing Children's Hospital Affiliated Nanjing Medical University, Nanjing, China
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Dongmei Zhu
- Department of Pediatric Surgery, Nanjing Children's Hospital Affiliated Nanjing Medical University, Nanjing, China
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Hua Xie
- Department of Pediatric Surgery, Nanjing Children's Hospital Affiliated Nanjing Medical University, Nanjing, China
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Pingfa Chen
- Department of Pediatric Surgery, Nanjing Children's Hospital Affiliated Nanjing Medical University, Nanjing, China
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Bo Hang
- Department of Cell and Molecular Biology, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Shouyu Wang
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University), Ministry of Education, Nanjing, China
- Department of Molecular Cell Biology and Toxicology, Jiangsu Key Lab of Cancer Biomarkers, Prevention & Treatment, Cancer Center, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Yankai Xia
- Children's Hospital of Soochow University, Soochow, China
- Key Laboratory of Modern Toxicology (Nanjing Medical University), Ministry of Education, Nanjing, China
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Parrish AR. The cytoskeleton as a novel target for treatment of renal fibrosis. Pharmacol Ther 2016; 166:1-8. [PMID: 27343756 DOI: 10.1016/j.pharmthera.2016.06.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 06/07/2016] [Indexed: 12/23/2022]
Abstract
The incidence of chronic kidney disease (CKD) is increasing, with an estimated prevalence of 12% in the United States (Synder et al., 2009). While CKD may progress to end-stage renal disease (ESRD), which necessitates renal replacement therapy, i.e. dialysis or transplantation, most CKD patients never reach ESRD due to the increased risk of death from cardiovascular disease. It is well-established that regardless of the initiating insult - most often diabetes or hypertension - fibrosis is the common pathogenic pathway that leads to progressive injury and organ dysfunction (Eddy, 2014; Duffield, 2014). As such, there has been extensive research into the molecular and cellular mechanisms of renal fibrosis; however, translation to effective therapeutic strategies has been limited. While a role for the disruption of the cytoskeleton, most notably the actin network, has been established in acute kidney injury over the past two decades, a role in regulating renal fibrosis and CKD is only recently emerging. This review will focus on the role of the cytoskeleton in regulating pro-fibrotic pathways in the kidney, as well as data suggesting that these pathways represent novel therapeutic targets to manage fibrosis and ultimately CKD.
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Affiliation(s)
- Alan R Parrish
- Department of Medical Pharmacology and Physiology, School of Medicine, University of Missouri, Columbia, MO 65212, USA.
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Lu X, Fukumoto S, Yamada Y, Evans CA, Diekwisch TG, Luan X. Ameloblastin, an Extracellular Matrix Protein, Affects Long Bone Growth and Mineralization. J Bone Miner Res 2016; 31:1235-46. [PMID: 26766111 DOI: 10.1002/jbmr.2788] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 01/06/2016] [Accepted: 01/08/2016] [Indexed: 11/07/2022]
Abstract
Matrix molecules such as the enamel-related calcium-binding phosphoprotein ameloblastin (AMBN) are expressed in multiple tissues, including teeth, bones, and cartilage. Here we have asked whether AMBN is of functional importance for timely long bone development and, if so, how it exerts its function related to osteogenesis. Adolescent AMBN-deficient mice (AMBN(Δ5-6) ) suffered from a 33% to 38% reduction in femur length and an 8.4% shorter trunk spinal column when compared with WT controls, whereas there was no difference between adult animals. On a cellular level, AMBN truncation resulted in a shortened growth plate and a 41% to 49% reduction in the number of proliferating tibia chondrocytes and osteoblasts. Bone marrow stromal cells (BMSCs) isolated from AMBN mutant mice displayed defects in proliferation and differentiation potential as well as cytoskeleton organization. Osteogenesis-related growth factors, such as insulin-like growth factor 1 (IGF1) and BMP7, were also significantly (46% to 73%) reduced in AMBN-deficient BMSCs. Addition of exogenous AMBN restored cytoskeleton structures in AMBN mutant BMSCs and resulted in a dramatic 400% to 600% increase in BMP2, BMP7, and Col1A expression. Block of RhoA diminished the effect of AMBN on osteogenic growth factor and matrix protein gene expression. Addition of exogenous BMP7 and IGF1 rescued the proliferation and differentiation potential of AMBN-deficient BMSCs. Confirming the effects of AMBN on long bone growth, back-crossing of mutant mice with full-length AMBN overexpressors resulted in a complete rescue of AMBN(Δ5-6) bone defects. Together, these data indicate that AMBN affects extracellular matrix production and cell adhesion properties in the long bone growth plate, resulting in altered cytoskeletal dynamics, increased osteogenesis-related gene expression, as well as osteoblast and chondrocyte proliferation. We propose that AMBN facilitates rapid long bone growth and an important growth spurt during the skeletogenesis of adolescent tooth-bearing vertebrates. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Xuanyu Lu
- Department of Oral Biology, Brodie Laboratory for Craniofacial Genetics, University of Illinois College of Dentistry, Chicago, IL, USA
| | - Satoshi Fukumoto
- Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Yoshihiko Yamada
- Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Carla A Evans
- Department of Orthodontics, Brodie Laboratory for Craniofacial Genetics, University of Illinois College of Dentistry, Chicago, IL, USA
| | - Thomas Gh Diekwisch
- Department of Oral Biology, Brodie Laboratory for Craniofacial Genetics, University of Illinois College of Dentistry, Chicago, IL, USA
| | - Xianghong Luan
- Department of Oral Biology, Brodie Laboratory for Craniofacial Genetics, University of Illinois College of Dentistry, Chicago, IL, USA.,Department of Orthodontics, Brodie Laboratory for Craniofacial Genetics, University of Illinois College of Dentistry, Chicago, IL, USA
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56
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Speight P, Kofler M, Szászi K, Kapus A. Context-dependent switch in chemo/mechanotransduction via multilevel crosstalk among cytoskeleton-regulated MRTF and TAZ and TGFβ-regulated Smad3. Nat Commun 2016; 7:11642. [PMID: 27189435 PMCID: PMC4873981 DOI: 10.1038/ncomms11642] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 04/15/2016] [Indexed: 01/12/2023] Open
Abstract
Myocardin-related transcription factor (MRTF) and TAZ are major mechanosensitive transcriptional co-activators that link cytoskeleton organization to gene expression. Despite many similarities in their regulation, their physical and/or functional interactions are unknown. Here we show that MRTF and TAZ associate partly through a WW domain-dependent mechanism, and exhibit multilevel crosstalk affecting each other's expression, transport and transcriptional activity. Specifically, MRTF is essential for TAZ expression; TAZ and MRTF inhibit each other's cytosolic mobility and stimulus-induced nuclear accumulation; they antagonize each other's stimulatory effect on the α-smooth muscle actin (SMA) promoter, which harbours nearby cis-elements for both, but synergize on isolated TEAD-elements. Importantly, TAZ confers Smad3 sensitivity to the SMA promoter. Thus, TAZ is a context-dependent switch during mechanical versus mechano/chemical signalling, which inhibits stretch-induced but is indispensable for stretch+TGFβ-induced SMA expression. Crosstalk between these cytoskeleton-regulated factors seems critical for fine-tuning mechanical and mechanochemical transcriptional programmes underlying myofibroblast transition, wound healing and fibrogenesis.
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Affiliation(s)
- Pam Speight
- Keenan Research Centre for Biomedical Science of St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada M5B 1T8
| | - Michael Kofler
- Keenan Research Centre for Biomedical Science of St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada M5B 1T8
| | - Katalin Szászi
- Keenan Research Centre for Biomedical Science of St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada M5B 1T8.,Department Surgery, University of Toronto, Toronto, Ontario, Canada M5P 1T5
| | - András Kapus
- Keenan Research Centre for Biomedical Science of St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada M5B 1T8.,Department Surgery, University of Toronto, Toronto, Ontario, Canada M5P 1T5.,Department Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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57
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Verboon JM, Sugumar B, Parkhurst SM. Wiskott-Aldrich syndrome proteins in the nucleus: aWASH with possibilities. Nucleus 2016; 6:349-59. [PMID: 26305109 PMCID: PMC4915506 DOI: 10.1080/19491034.2015.1086051] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Actin and proteins that regulate its dynamics or interactions have well-established roles in the cytoplasm where they function as key components of the cytoskeleton to control diverse processes, including cellular infrastructure, cellular motility, cell signaling, and vesicle transport. Recent work has also uncovered roles for actin and its regulatory proteins in the nucleus, primarily in mechanisms governing gene expression. The Wiskott Aldrich Syndrome (WAS) family of proteins, comprising the WASP/N-WASP, SCAR/WAVE, WHAMM/JMY/WHAMY, and WASH subfamilies, function in the cytoplasm where they activate the Arp2/3 complex to form branched actin filaments. WAS proteins are present in the nucleus and have been implicated as transcriptional regulators. We found that Drosophila Wash, in addition to transcriptional effects, is involved in global nuclear architecture. Here we summarize the regulation and function of nuclear WAS proteins, and highlight how our work with Wash expands the possibilities for the functions of these proteins in the nucleus.
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Affiliation(s)
- Jeffrey M Verboon
- a Division of Basic Sciences; Fred Hutchinson Cancer Research Center ; Seattle , WA USA
| | - Bina Sugumar
- a Division of Basic Sciences; Fred Hutchinson Cancer Research Center ; Seattle , WA USA
| | - Susan M Parkhurst
- a Division of Basic Sciences; Fred Hutchinson Cancer Research Center ; Seattle , WA USA
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58
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Wallrath LL, Bohnekamp J, Magin TM. Cross talk between the cytoplasm and nucleus during development and disease. Curr Opin Genet Dev 2016; 37:129-136. [PMID: 27110666 DOI: 10.1016/j.gde.2016.03.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 03/09/2016] [Accepted: 03/15/2016] [Indexed: 01/03/2023]
Abstract
Mechanotransduction is a process whereby mechanical stimuli outside the cell are sensed by components of the plasma membrane and transmitted as signals through the cytoplasm that terminate in the nucleus. The nucleus responds to these signals by altering gene expression. During mechanotransduction, complex networks of proteins are responsible for cross talk between the cytoplasm and the nucleus. These proteins include cell membrane receptors, cytoplasmic filaments, LINC complex members that bridge the nucleus and cytoplasm, and nuclear envelope proteins that connect to the chromatin. Mechanotransduction also plays a critical role in development. Furthermore, it is possible that disrupted mechanotransduction leads to changes in gene expression that underlie the pathogenic mechanisms of disease.
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Affiliation(s)
- Lori L Wallrath
- Department of Biochemistry, University of Iowa, Iowa City, IA 52242, USA.
| | - Jens Bohnekamp
- Institute of Biology and Translational Center for Regenerative Medicine, University of Leipzig, D-04103 Leipzig, Germany
| | - Thomas M Magin
- Institute of Biology and Translational Center for Regenerative Medicine, University of Leipzig, D-04103 Leipzig, Germany
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59
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Actin, actin-binding proteins, and actin-related proteins in the nucleus. Histochem Cell Biol 2016; 145:373-88. [PMID: 26847179 DOI: 10.1007/s00418-015-1400-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2015] [Indexed: 10/25/2022]
Abstract
Extensive research in the past decade has significantly broadened our view about the role actin plays in the life of the cell and added novel aspects to actin research. One of these new aspects is the discovery of the existence of nuclear actin which became evident only recently. Nuclear activities including transcriptional activation in the case of all three RNA polymerases, editing and nuclear export of mRNAs, and chromatin remodeling all depend on actin. It also became clear that there is a fine-tuned equilibrium between cytoplasmic and nuclear actin pools and that this balance is ensured by an export-import system dedicated to actin. After over half a century of research on conventional actin and its organizing partners in the cytoplasm, it was also an unexpected finding that the nucleus contains more than 30 actin-binding proteins and new classes of actin-related proteins which are not able to form filaments but had evolved nuclear-specific functions. The actin-binding and actin-related proteins in the nucleus have been linked to RNA transcription and processing, nuclear transport, and chromatin remodeling. In this paper, we attempt to provide an overview of the wide range of information that is now available about actin, actin-binding, and actin-related proteins in the nucleus.
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60
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HSPC280, a winged helix protein expressed in the subventricular zone of the developing ganglionic eminences, inhibits neuronal differentiation. Histochem Cell Biol 2015; 145:175-84. [PMID: 26537243 DOI: 10.1007/s00418-015-1380-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/21/2015] [Indexed: 12/27/2022]
Abstract
Winged helix proteins have critical roles in a variety of developmental processes. During a screening for genes expressed in the developing forebrain, we identified HSPC280, a non-typical winged helix protein, which shares similarity with a protein-protein interaction domain found in the proteins of the actin-binding Rho-activating protein family. In this work, we analyzed HSPC280 expression during mouse development as well as during neuronal differentiation of mouse Neuro2a cells. HSPC280 expression is tightly regulated; during mouse development, it was detected predominantly in the ganglionic eminences of the ventral telencephalon, from their appearance at E11.5 to P0, with the highest levels between E13.5 and E15.5, a period that correlates with the peak of neurogenesis in these structures. Comparative expression analysis of HSPC280 with Dlx2, cyclinD2 and Lhx6 revealed that, within the ganglionic eminences, HSPC280 was restricted in the proliferating cell population of the subventricular zone, in a pattern similar to that of cyclinD2. Finally, we showed that HSPC280 is a nuclear protein which, when overexpressed in Neuro2a cells, it inhibited neuronal differentiation in vitro, suggesting its involvement in the mechanisms controlling neural progenitor cells proliferation.
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Corcoran JA, McCormick C. Viral activation of stress-regulated Rho-GTPase signaling pathway disrupts sites of mRNA degradation to influence cellular gene expression. Small GTPases 2015; 6:178-85. [PMID: 26480288 PMCID: PMC4905259 DOI: 10.1080/21541248.2015.1093068] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 09/07/2015] [Accepted: 09/08/2015] [Indexed: 01/09/2023] Open
Abstract
Viruses are useful tools that often reveal previously unrecognized levels of control within a cell. By studying the oncogenic Kaposi's sarcoma-associated herpesvirus (KSHV), we discovered a new signaling axis in endothelial cells (ECs) that links actin cytoskeleton dynamics to post-transcriptional control of gene expression. Translational repression and rapid decay of mRNAs containing AU-rich elements (AREs) occurs in cytoplasmic RNA granules known as processing bodies (PBs). Rho-GTPase activity influences PB dynamics but mechanistic details remain obscure. We have previously shown that the KSHV Kaposin B protein blocks the degradation of ARE-mRNAs that encode potent cytokines and angiogenic factors, at least in part by preventing PB formation. Moreover, Kaposin B is sufficient to cause marked alterations in endothelial cell physiology including the formation of long parallel actin stress fibers and accelerated migration and angiogenic phenotypes. All of these phenotypes depend on Kaposin B-mediated activation of a non-canonical signaling pathway comprising the stress-inducible kinase MK2, hsp27, p115RhoGEF and RhoA. Accelerated endothelial cell migration and angiogenesis depends on the subsequent activation of the RhoA-dependent kinase ROCK, but PB disruption is ROCK-independent. In this Commentary, we discuss implications of the activation of this signaling axis, and propose mechanistic links between RhoA activation and PB dynamics.
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Affiliation(s)
- Jennifer A Corcoran
- Department of Microbiology and Immunology; Dalhousie University; Halifax NS, Canada
| | - Craig McCormick
- Department of Microbiology and Immunology; Dalhousie University; Halifax NS, Canada
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Chang M, Huang S. Arabidopsis ACT11 modifies actin turnover to promote pollen germination and maintain the normal rate of tube growth. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 83:515-527. [PMID: 26096143 DOI: 10.1111/tpj.12910] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 05/21/2015] [Accepted: 06/01/2015] [Indexed: 06/04/2023]
Abstract
Actin is an ancient conserved protein that is encoded by multiple isovariants in multicellular organisms. There are eight functional actin genes in the Arabidopsis genome, and the precise function and mechanism of action of each isovariant remain poorly understood. Here, we report the characterization of ACT11, a reproductive actin isovariant. Our studies reveal that loss of function of ACT11 causes a delay in pollen germination, but enhances pollen tube growth. Cytological analysis revealed that the amount of filamentous actin decreased, and the rate of actin turnover increased in act11 pollen. Convergence of actin filaments upon the germination aperture was impaired in act11 pollen, consistent with the observed delay of germination. Reduction of actin dynamics with jasplakinolide suppressed the germination and tube growth phenotypes in act11 pollen, suggesting that the underlying mechanisms involve an increase in actin dynamics. Thus, we demonstrate that ACT11 is required to maintain the rate of actin turnover in order to promote pollen germination and maintain the normal rate of pollen tube growth.
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Affiliation(s)
- Ming Chang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shanjin Huang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- National Center for Plant Gene Research, Beijing, 100101, China
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Donnelly SK, Bravo-Cordero JJ, Hodgson L. Rho GTPase isoforms in cell motility: Don't fret, we have FRET. Cell Adh Migr 2015; 8:526-34. [PMID: 25482645 PMCID: PMC4594258 DOI: 10.4161/cam.29712] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The Rho-family of p21 small GTPases are directly linked to the regulation of actin-based motile machinery and play a key role in the control of cell migration. Aside from the original and most well-characterized canonical Rho GTPases RhoA, Rac1, and Cdc42, numerous isoforms of these key proteins have been identified and shown to have specific roles in regulating various cellular motility processes. The major difficulty in addressing these isoform-specific effects is that isoforms typically contain highly similar primary amino acid sequences and thus are able to interact with the same upstream regulators and the downstream effector targets. Here, we will introduce the major members of each GTPase subfamily and discuss recent advances in the design and application of fluorescent resonance energy transfer-based probes, which are at the forefront of the technologies available to directly probe the differential, spatiotemporal activation dynamics of these proteins in live single cells. Currently, it is possible to specifically detect the activation status of RhoA vs. RhoC isoforms, as well as Cdc42 vs. TC-10 isoforms in living cells. Clearly, additional efforts are still required to produce biosensor systems capable of detecting other isoforms of Rho GTPases including RhoB, Rac2/3, RhoG, etc. Through such efforts, we will uncover the isoform-specific roles of these near-identical proteins in living cells, clearly an important area of the Rho GTPase biology that is not yet fully appreciated.
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Affiliation(s)
- Sara K Donnelly
- a Department of Anatomy and Structural Biology ; Albert Einstein College of Medicine of Yeshiva University ; Bronx , NY USA
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Affiliation(s)
| | - Nicolas Bourmeyster
- Laboratoire Signalisation et Transports Ioniques Membranaires (STIM); Université de Poitiers Poitiers Cédex, France
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Dopie J, Rajakylä EK, Joensuu MS, Huet G, Ferrantelli E, Xie T, Jäälinoja H, Jokitalo E, Vartiainen MK. Genome-wide RNAi screen for nuclear actin reveals a network of cofilin regulators. J Cell Sci 2015; 128:2388-400. [PMID: 26021350 PMCID: PMC4510847 DOI: 10.1242/jcs.169441] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 05/19/2015] [Indexed: 01/15/2023] Open
Abstract
Nuclear actin plays an important role in many processes that regulate gene expression. Cytoplasmic actin dynamics are tightly controlled by numerous actin-binding proteins, but regulation of nuclear actin has remained unclear. Here, we performed a genome-wide RNA interference (RNAi) screen in Drosophila cells to identify proteins that influence either nuclear polymerization or import of actin. We validate 19 factors as specific hits, and show that Chinmo (known as Bach2 in mammals), SNF4Aγ (Prkag1 in mammals) and Rab18 play a role in nuclear localization of actin in both fly and mammalian cells. We identify several new regulators of cofilin activity, and characterize modulators of both cofilin kinases and phosphatase. For example, Chinmo/Bach2, which regulates nuclear actin levels also in vivo, maintains active cofilin by repressing the expression of the kinase Cdi (Tesk in mammals). Finally, we show that Nup98 and lamin are candidates for regulating nuclear actin polymerization. Our screen therefore reveals new aspects of actin regulation and links nuclear actin to many cellular processes.
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Affiliation(s)
- Joseph Dopie
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Eeva K Rajakylä
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Merja S Joensuu
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Guillaume Huet
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Evelina Ferrantelli
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Tiao Xie
- Image and Data Analysis Core (IDAC), Harvard Medical School, Boston, MA 02115, USA
| | - Harri Jäälinoja
- Light Microscopy Unit, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Eija Jokitalo
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Maria K Vartiainen
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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66
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Giehl K, Keller C, Muehlich S, Goppelt-Struebe M. Actin-mediated gene expression depends on RhoA and Rac1 signaling in proximal tubular epithelial cells. PLoS One 2015; 10:e0121589. [PMID: 25816094 PMCID: PMC4376694 DOI: 10.1371/journal.pone.0121589] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 02/14/2015] [Indexed: 12/29/2022] Open
Abstract
Morphological alterations of cells can lead to modulation of gene expression. An essential link is the MKL1-dependent activation of serum response factor (SRF), which translates changes in the ratio of G- and F-actin into mRNA transcription. SRF activation is only partially characterized in non-transformed epithelial cells. Therefore, the impact of GTPases of the Rho family and changes in F-actin structures were analyzed in renal proximal tubular epithelial cells. Activation of SRF signaling was compared to the regulation of a known MKL1/SRF target gene, connective tissue growth factor (CTGF). In the human proximal tubular cell line HKC-8 overexpression of two actin mutants either favoring or preventing the formation of F-actin fibers regulated SRF-mediated transcription as well as CTGF expression. Only overexpression of constitutively active RhoA activated SRF-dependent gene expression whereas no effect was detected upon overexpression of Rac1 mutants. To elucidate the functional role of Rho kinases as downstream mediators of RhoA, pharmacological inhibition and genetic inhibition by transient siRNA knock down were compared. Upon stimulation with lysophosphatidic acid (LPA) Rho kinase inhibitors partially suppressed SRF-mediated transcription, whereas interference with Rho kinase expression by siRNA reduced activation of SRF, but barely affected CTGF expression. Together with the partial inhibition of CTGF expression by the pharmacological inhibitors Y27432 and H1154, Rho kinases seem to be less important in mediating RhoA signaling related to CTGF expression in HKC-8 epithelial cells. Short term pharmacological inhibition of Rac1 activity by EHT1864 reduced SRF-dependent CTGF expression in HKC-8 cells, but was overcome by a stimulatory effect after prolonged incubation after 4-6 h. Similarly, human primary cells of proximal but not of distal tubular origin showed inhibitory as well as stimulatory effects of Rac1 inhibition. Thus, RhoA signaling activates MKL1-SRF-mediated CTGF expression in proximal tubular cells, whereas Rac1 signaling is more complex with adaptive cellular responses.
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Affiliation(s)
- Klaudia Giehl
- Signal Transduction of Cellular Motility, Internal Medicine V, Justus-Liebig-University Giessen, Giessen, Germany
| | - Christof Keller
- Department of Nephrology and Hypertension, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Susanne Muehlich
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-University, Munich, Germany
| | - Margarete Goppelt-Struebe
- Department of Nephrology and Hypertension, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
- * E-mail:
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67
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Volkman LE. Baculoviruses and nucleosome management. Virology 2015; 476:257-263. [PMID: 25569454 DOI: 10.1016/j.virol.2014.12.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 12/09/2014] [Accepted: 12/10/2014] [Indexed: 11/30/2022]
Abstract
Negatively-supercoiled-ds DNA molecules, including the genomes of baculoviruses, spontaneously wrap around cores of histones to form nucleosomes when present within eukaryotic nuclei. Hence, nucleosome management should be essential for baculovirus genome replication and temporal regulation of transcription, but this has not been documented. Nucleosome mobilization is the dominion of ATP-dependent chromatin-remodeling complexes. SWI/SNF and INO80, two of the best-studied complexes, as well as chromatin modifier TIP60, all contain actin as a subunit. Retrospective analysis of results of AcMNPV time course experiments wherein actin polymerization was blocked by cytochalasin D drug treatment implicate actin-containing chromatin modifying complexes in decatenating baculovirus genomes, shutting down host transcription, and regulating late and very late phases of viral transcription. Moreover, virus-mediated nuclear localization of actin early during infection may contribute to nucleosome management.
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Affiliation(s)
- Loy E Volkman
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
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68
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Luo T, Roman P, Liu C, Sun X, Park Y, Hu B. Upregulation of the GEF-H1 pathway after transient cerebral ischemia. Exp Neurol 2014; 263:306-13. [PMID: 25447939 DOI: 10.1016/j.expneurol.2014.10.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/10/2014] [Accepted: 10/22/2014] [Indexed: 01/10/2023]
Abstract
The microtubule-dependent GEF-H1 pathway controls synaptic re-networking and overall gene expression via regulating cytoskeleton dynamics. Understanding this pathway after ischemia is essential to developing new therapies for neuronal function recovery. However, how the GEF-H1 pathway is regulated following transient cerebral ischemia remains unknown. This study employed a rat model of transient forebrain ischemia to investigate alterations of the GEF-H1 pathway using Western blotting, confocal and electron microscopy, dephosphorylation analysis, and pull-down assay. The GEF-H1 activity was significantly upregulated by: (i) dephosphorylation and (ii) translocation to synaptic membrane and nuclear structures during the early phase of reperfusion. GEF-H1 protein was then downregulated in the brain regions where neurons were destined to undergo delayed neuronal death, but markedly upregulated in neurons that were resistant to the same episode of cerebral ischemia. Consistently, GTP-RhoA, a GEF-H1 substrate, was significantly upregulated after brain ischemia. Electron microscopy further showed that neuronal microtubules were persistently depolymerized in the brain region where GEF-H1 protein was downregulated after brain ischemia. The results demonstrate that the GEF-H1 activity is significantly upregulated in both vulnerable and resistant brain regions in the early phase of reperfusion. However, GEF-H1 protein is downregulated in the vulnerable neurons but upregulated in the ischemic resistant neurons during the recovery phase after ischemia. The initial upregulation of GEF-H1 activity may contribute to excitotoxicity, whereas the late upregulation of GEF-H1 protein may promote neuroplasticity after brain ischemia.
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Affiliation(s)
- Tianfei Luo
- Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Department of Neurology, The First Teaching Hospital, Jilin University, Changchun, China
| | - Philip Roman
- Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States
| | - Chunli Liu
- Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States
| | - Xin Sun
- Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Department of Neurology, The First Teaching Hospital, Jilin University, Changchun, China
| | - Yujung Park
- Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States
| | - Bingren Hu
- Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
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69
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Yin Z, Sailem H, Sero J, Ardy R, Wong STC, Bakal C. How cells explore shape space: a quantitative statistical perspective of cellular morphogenesis. Bioessays 2014; 36:1195-203. [PMID: 25220035 DOI: 10.1002/bies.201400011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Through statistical analysis of datasets describing single cell shape following systematic gene depletion, we have found that the morphological landscapes explored by cells are composed of a small number of attractor states. We propose that the topology of these landscapes is in large part determined by cell-intrinsic factors, such as biophysical constraints on cytoskeletal organization, and reflects different stable signaling and/or transcriptional states. Cell-extrinsic factors act to determine how cells explore these landscapes, and the topology of the landscapes themselves. Informational stimuli primarily drive transitions between stable states by engaging signaling networks, while mechanical stimuli tune, or even radically alter, the topology of these landscapes. As environments fluctuate, the topology of morphological landscapes explored by cells dynamically adapts to these fluctuations. Finally we hypothesize how complex cellular and tissue morphologies can be generated from a limited number of simple cell shapes.
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Affiliation(s)
- Zheng Yin
- Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute, Weill Cornell Medical College, Houston, TX, USA
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