1
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Mai Le N, Li J. Ras-related C3 botulinum toxin substrate 1 role in Pathophysiology of Neurological diseases. BRAIN HEMORRHAGES 2022. [DOI: 10.1016/j.hest.2022.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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2
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Colón-Bolea P, García-Gómez R, Shackleton S, Crespo P, Bustelo XR, Casar B. RAC1 induces nuclear alterations through the LINC complex to enhance melanoma invasiveness. Mol Biol Cell 2020; 31:2768-2778. [PMID: 33026942 PMCID: PMC7851868 DOI: 10.1091/mbc.e20-02-0127] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
RHO GTPases are key regulators of the cytoskeletal architecture, which impact a broad range of biological processes in malignant cells including motility, invasion, and metastasis, thereby affecting tumor progression. One of the constraints during cell migration is the diameter of the pores through which cells pass. In this respect, the size and shape of the nucleus pose a major limitation. Therefore, enhanced nuclear plasticity can promote cell migration. Nuclear morphology is determined in part through the cytoskeleton, which connects to the nucleoskeleton through the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. Here, we unravel the role of RAC1 as an orchestrator of nuclear morphology in melanoma cells. We demonstrate that activated RAC1 promotes nuclear alterations through its effector PAK1 and the tubulin cytoskeleton, thereby enhancing migration and intravasation of melanoma cells. Disruption of the LINC complex prevented RAC1-induced nuclear alterations and the invasive properties of melanoma cells. Thus, RAC1 induces nuclear morphology alterations through microtubules and the LINC complex to promote an invasive phenotype in melanoma cells.
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Affiliation(s)
- Paula Colón-Bolea
- Instituto de Biomedicina y Biotecnología de Cantabria, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Cantabria, Santander 39011, Spain
| | - Rocío García-Gómez
- Instituto de Biomedicina y Biotecnología de Cantabria, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Cantabria, Santander 39011, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Instituto de Salud Carlos III, Madrid 28029, Spain
| | - Sue Shackleton
- Department of Biochemistry, University of Leicester, Leicester LE1 9HM, UK
| | - Piero Crespo
- Instituto de Biomedicina y Biotecnología de Cantabria, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Cantabria, Santander 39011, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Instituto de Salud Carlos III, Madrid 28029, Spain
| | - Xosé R Bustelo
- Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Instituto de Salud Carlos III, Madrid 28029, Spain.,Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer (CSIC), Universidad de Salamanca, Salamanca 37007, Spain
| | - Berta Casar
- Instituto de Biomedicina y Biotecnología de Cantabria, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Cantabria, Santander 39011, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Instituto de Salud Carlos III, Madrid 28029, Spain
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3
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Hodge RG, Schaefer A, Howard SV, Der CJ. RAS and RHO family GTPase mutations in cancer: twin sons of different mothers? Crit Rev Biochem Mol Biol 2020; 55:386-407. [PMID: 32838579 DOI: 10.1080/10409238.2020.1810622] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The RAS and RHO family comprise two major branches of the RAS superfamily of small GTPases. These proteins function as regulated molecular switches and control cytoplasmic signaling networks that regulate a diversity of cellular processes, including cell proliferation and cell migration. In the early 1980s, mutationally activated RAS genes encoding KRAS, HRAS and NRAS were discovered in human cancer and now comprise the most frequently mutated oncogene family in cancer. Only recently, exome sequencing studies identified cancer-associated alterations in two RHO family GTPases, RAC1 and RHOA. RAS and RHO proteins share significant identity in their amino acid sequences, protein structure and biochemistry. Cancer-associated RAS mutant proteins harbor missense mutations that are found primarily at one of three mutational hotspots (G12, G13 and Q61) and have been identified as gain-of-function oncogenic alterations. Although these residues are conserved in RHO family proteins, the gain-of-function mutations found in RAC1 are found primarily at a distinct hotspot. Unexpectedly, the cancer-associated mutations found with RHOA are located at different hotspots than those found with RAS. Furthermore, since the RHOA mutations suggested a loss-of-function phenotype, it has been unclear whether RHOA functions as an oncogene or tumor suppressor in cancer development. Finally, whereas RAS mutations are found in a broad spectrum of cancer types, RHOA and RAC1 mutations occur in a highly restricted range of cancer types. In this review, we focus on RHOA missense mutations found in cancer and their role in driving tumorigenesis, with comparisons to cancer-associated mutations in RAC1 and RAS GTPases.
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Affiliation(s)
- Richard G Hodge
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Antje Schaefer
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.,Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sarah V Howard
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Channing J Der
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.,Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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4
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Yao D, Li C, Rajoka MSR, He Z, Huang J, Wang J, Zhang J. P21-Activated Kinase 1: Emerging biological functions and potential therapeutic targets in Cancer. Am J Cancer Res 2020; 10:9741-9766. [PMID: 32863957 PMCID: PMC7449905 DOI: 10.7150/thno.46913] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 07/23/2020] [Indexed: 02/06/2023] Open
Abstract
The p21-Activated kinase 1 (PAK1), a member of serine-threonine kinases family, was initially identified as an interactor of the Rho GTPases RAC1 and CDC42, which affect a wide range of processes associated with cell motility, survival, metabolism, cell cycle, proliferation, transformation, stress, inflammation, and gene expression. Recently, the PAK1 has emerged as a potential therapeutic target in cancer due to its role in many oncogenic signaling pathways. Many PAK1 inhibitors have been developed as potential preclinical agents for cancer therapy. Here, we provide an overview of essential roles that PAK1 plays in cancer, including its structure and autoactivation mechanism, its crucial function from onset to progression to metastasis, metabolism, immune escape and even drug resistance in cancer; endogenous regulators; and cancer-related pathways. We also summarize the reported PAK1 small-molecule inhibitors based on their structure types and their potential application in cancer. In addition, we provide overviews on current progress and future challenges of PAK1 in cancer, hoping to provide new ideas for the diagnosis and treatment of cancer.
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5
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Rac1 activates non-oxidative pentose phosphate pathway to induce chemoresistance of breast cancer. Nat Commun 2020; 11:1456. [PMID: 32193458 PMCID: PMC7081201 DOI: 10.1038/s41467-020-15308-7] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 02/27/2020] [Indexed: 02/08/2023] Open
Abstract
Resistance development to one chemotherapeutic reagent leads frequently to acquired tolerance to other compounds, limiting the therapeutic options for cancer treatment. Herein, we find that overexpression of Rac1 is associated with multi-drug resistance to the neoadjuvant chemotherapy (NAC). Mechanistically, Rac1 activates aldolase A and ERK signaling which up-regulates glycolysis and especially the non-oxidative pentose phosphate pathway (PPP). This leads to increased nucleotides metabolism which protects breast cancer cells from chemotherapeutic-induced DNA damage. To translate this finding, we develop endosomal pH-responsive nanoparticles (NPs) which deliver Rac1-targeting siRNA together with cisplatin and effectively reverses NAC-chemoresistance in PDXs from NAC-resistant breast cancer patients. Altogether, our findings demonstrate that targeting Rac1 is a potential strategy to overcome acquired chemoresistance in breast cancer. Acquired resistance to chemotherapy can lead to multi-drug resistance and poor prognosis in cancer. Here, the authors show that Rac1 increases glycolysis and non-oxidative pentose phosphate pathway activity leading to neoadjuvant chemotherapy (NAC) resistance, thus its inhibition sensitizes resistant breast cancer PDXs to NAC.
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6
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Yan M, Dou T, Lv W, Wang X, Zhao L, Chang X, Zhou Z. Integrated analysis of paraquat-induced microRNAs-mRNAs changes in human neural progenitor cells. Toxicol In Vitro 2017; 44:196-205. [DOI: 10.1016/j.tiv.2017.06.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 03/30/2017] [Accepted: 06/10/2017] [Indexed: 10/19/2022]
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7
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Sheng N, Tan G, You W, Chen H, Gong J, Chen D, Zhang H, Wang Z. MiR-145 inhibits human colorectal cancer cell migration and invasion via PAK4-dependent pathway. Cancer Med 2017; 6:1331-1340. [PMID: 28440035 PMCID: PMC5463071 DOI: 10.1002/cam4.1029] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 01/04/2017] [Accepted: 01/08/2017] [Indexed: 01/05/2023] Open
Abstract
MicroRNA-145 (miR-145), as a tumor-suppressive miRNA, has been demonstrated down-regulated in colorectal cancer (CRC) cells, and could inhibit CRC cells growth. However, the molecular pathway in which miR-145 modulates CRC malignant transformation has not been fully revealed. Here, we reported an intense correlation between the expressions of PAK4 and miR-145 in human CRC cell lines. Transwell assay verified overexpression of miR-145, as well as knockdown of PAK4, significantly suppressed cell migration and invasion ability. The impaired migration and invasion ability of SW1116 cells was affected through the down-regulation of phosphorylation level of LIMK1 and cofilin in a PAK4-dependent manner. Collectively, we have demonstrated that miR-145 suppressed CRC migration and invasion through PAK4 pathway, which provides an attractive microRNA-based therapeutic target for CRC.
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Affiliation(s)
- Nengquan Sheng
- Department of General SurgeryShanghai Jiao Tong University Affiliated Sixth People's HospitalShanghai200233China
| | - Gewen Tan
- Department of General SurgeryShanghai Jiao Tong University Affiliated Sixth People's HospitalShanghai200233China
| | - Weiqiang You
- Department of General SurgeryShanghai Jiao Tong University Affiliated Sixth People's HospitalShanghai200233China
| | - Hongqi Chen
- Department of General SurgeryShanghai Jiao Tong University Affiliated Sixth People's HospitalShanghai200233China
| | - Jianfeng Gong
- Department of General SurgeryShanghai Jiao Tong University Affiliated Sixth People's HospitalShanghai200233China
| | - Di Chen
- National Key Laboratory of Science and Technology on Nano/Micro Fabrication TechnologyResearch Institute Micro/Nano Science and TechnologyShanghai Jiao Tong UniversityShanghai200240China
| | - Huizhen Zhang
- Department of PathologyShanghai Jiao Tong University Affiliated Sixth People's HospitalShanghai200233China
| | - Zhigang Wang
- Department of General SurgeryShanghai Jiao Tong University Affiliated Sixth People's HospitalShanghai200233China
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8
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Hu H, Juvekar A, Lyssiotis CA, Lien EC, Albeck JG, Oh D, Varma G, Hung YP, Ullas S, Lauring J, Seth P, Lundquist MR, Tolan DR, Grant AK, Needleman DJ, Asara JM, Cantley LC, Wulf GM. Phosphoinositide 3-Kinase Regulates Glycolysis through Mobilization of Aldolase from the Actin Cytoskeleton. Cell 2016; 164:433-46. [PMID: 26824656 DOI: 10.1016/j.cell.2015.12.042] [Citation(s) in RCA: 254] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 08/18/2015] [Accepted: 12/22/2015] [Indexed: 02/06/2023]
Abstract
The phosphoinositide 3-kinase (PI3K) pathway regulates multiple steps in glucose metabolism and also cytoskeletal functions, such as cell movement and attachment. Here, we show that PI3K directly coordinates glycolysis with cytoskeletal dynamics in an AKT-independent manner. Growth factors or insulin stimulate the PI3K-dependent activation of Rac, leading to disruption of the actin cytoskeleton, release of filamentous actin-bound aldolase A, and an increase in aldolase activity. Consistently, PI3K inhibitors, but not AKT, SGK, or mTOR inhibitors, cause a significant decrease in glycolysis at the step catalyzed by aldolase, while activating PIK3CA mutations have the opposite effect. These results point toward a master regulatory function of PI3K that integrates an epithelial cell's metabolism and its form, shape, and function, coordinating glycolysis with the energy-intensive dynamics of actin remodeling.
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Affiliation(s)
- Hai Hu
- Division of Hematology and Oncology, Beth Israel Deaconess Medical Center (BIDMC) and Harvard Medical School (HMS), Boston, MA 02215, USA
| | - Ashish Juvekar
- Division of Hematology and Oncology, Beth Israel Deaconess Medical Center (BIDMC) and Harvard Medical School (HMS), Boston, MA 02215, USA
| | | | - Evan C Lien
- Department of Pathology, BIDMC, Boston, MA 02215, USA
| | - John G Albeck
- Department of Cell Biology, HMS, Boston, MA 02215, USA
| | - Doogie Oh
- Department of Molecular and Cellular Biology, FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA
| | - Gopal Varma
- Department of Radiology, BIDMC Boston, MA 02215, USA
| | - Yin Pun Hung
- Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Soumya Ullas
- Longwood Small Animal Imaging Facility, BIDMC, Boston, MA 02215, USA
| | - Josh Lauring
- The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD 21287, USA
| | - Pankaj Seth
- Division of Interdisciplinary Medicine, BIDMC, Boston, MA 02215, USA
| | - Mark R Lundquist
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10065, USA
| | - Dean R Tolan
- Department of Biology, Boston University, Boston, MA 02215, USA
| | - Aaron K Grant
- Department of Radiology, BIDMC Boston, MA 02215, USA
| | - Daniel J Needleman
- Department of Molecular and Cellular Biology, FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA
| | - John M Asara
- Division of Signal Transduction, BIDMC, Boston, MA 02215, USA
| | - Lewis C Cantley
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10065, USA
| | - Gerburg M Wulf
- Division of Hematology and Oncology, Beth Israel Deaconess Medical Center (BIDMC) and Harvard Medical School (HMS), Boston, MA 02215, USA.
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9
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Zaldua N, Llavero F, Artaso A, Gálvez P, Lacerda HM, Parada LA, Zugaza JL. Rac1/p21‐activated kinase pathway controls retinoblastoma protein phosphorylation and E2F transcription factor activation in B lymphocytes. FEBS J 2016; 283:647-61. [DOI: 10.1111/febs.13617] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 10/26/2015] [Accepted: 12/01/2015] [Indexed: 12/20/2022]
Affiliation(s)
- Natalia Zaldua
- Center for Cooperative Research in Biosciences Bizkaia Science and Technology Park Spain
- Idem Biotechnology SL Cordovilla Spain
| | - Francisco Llavero
- Department of Genetics, Physical Anthropology and Animal Physiology University of the Basque Country Leioa Spain
- Achucarro Basque Center for Neuroscience Bizkaia Science and Technology Park Spain
| | - Alain Artaso
- Department of Genetics, Physical Anthropology and Animal Physiology University of the Basque Country Leioa Spain
| | - Patricia Gálvez
- Bioiberica Pharmascience Division Technological Park of Health Sciences Granada Spain
| | | | - Luis A. Parada
- Instituto de Patología Experimental CONICET‐Universidad Nacional de Salta Argentina
| | - José L. Zugaza
- Department of Genetics, Physical Anthropology and Animal Physiology University of the Basque Country Leioa Spain
- Achucarro Basque Center for Neuroscience Bizkaia Science and Technology Park Spain
- IKERBASQUE Basque Foundation for Science Bilbao Spain
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10
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Matveeva EA, Venkova LS, Chernoivanenko IS, Minin AA. Vimentin is involved in regulation of mitochondrial motility and membrane potential by Rac1. Biol Open 2015; 4:1290-7. [PMID: 26369929 PMCID: PMC4610213 DOI: 10.1242/bio.011874] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In this study we show that binding of mitochondria to vimentin intermediate filaments (VIF) is regulated by GTPase Rac1. The activation of Rac1 leads to a redoubling of mitochondrial motility in murine fibroblasts. Using double-mutants Rac1(G12V, F37L) and Rac1(G12V, Y40H) that are capable to activate different effectors of Rac1, we show that mitochondrial movements are regulated through PAK1 kinase. The involvement of PAK1 kinase is also confirmed by the fact that expression of its auto inhibitory domain (PID) blocks the effect of activated Rac1 on mitochondrial motility. The observed effect of Rac1 and PAK1 kinase on mitochondria depends on phosphorylation of the Ser-55 of vimentin. Besides the effect on motility Rac1 activation also decreases the mitochondrial membrane potential (MMP) which is detected by ∼20% drop of the fluorescence intensity of mitochondria stained with the potential sensitive dye TMRM. One of important consequences of the discovered regulation of MMP by Rac1 and PAK1 is a spatial differentiation of mitochondria in polarized fibroblasts: at the front of the cell they are less energized (by ∼25%) than at the rear part.
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Affiliation(s)
- Elena A Matveeva
- Institute of Protein Research, Russian Academy of Sciences, Department of Cell Biology, Moscow 119988, Russia
| | - Larisa S Venkova
- Institute of Protein Research, Russian Academy of Sciences, Department of Cell Biology, Moscow 119988, Russia
| | - Ivan S Chernoivanenko
- Institute of Protein Research, Russian Academy of Sciences, Department of Cell Biology, Moscow 119988, Russia
| | - Alexander A Minin
- Institute of Protein Research, Russian Academy of Sciences, Department of Cell Biology, Moscow 119988, Russia
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11
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Vlisidou I, Wood W. Drosophila blood cells and their role in immune responses. FEBS J 2015; 282:1368-82. [PMID: 25688716 DOI: 10.1111/febs.13235] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/02/2015] [Accepted: 02/12/2015] [Indexed: 12/17/2022]
Abstract
Drosophila melanogaster has been extensively used to study the humoral arm of innate immunity because of the developmental and functional parallels with mammalian innate immunity. However, the fly cellular response to infection is far less understood. Investigative work on Drosophila haemocytes, the immunosurveillance cells of the insect, has revealed that they fulfil roles similar to mammalian monocytes and macrophages. They respond to wound signals and orchestrate the coagulation response. In addition, they phagocytose and encapsulate invading pathogens, and clear up apoptotic bodies controlling inflammation. This review briefly describes the Drosophila haematopoietic system and discusses what is currently known about the contribution of haemocytes to the immune response upon infection and wounding, during all stages of development.
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Affiliation(s)
- Isabella Vlisidou
- School of Cellular and Molecular Medicine, University of Bristol, UK
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12
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Bopp A, Wartlick F, Henninger C, Schwarz M, Kaina B, Fritz G. Rac1 promotes diethylnitrosamine (DEN)-induced formation of liver tumors. Carcinogenesis 2015; 36:378-89. [PMID: 25556150 DOI: 10.1093/carcin/bgu323] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
To elucidate the function of the Ras-homologous GTPase Rac1 in hepatocarcinogenesis induced by diethylnitrosamine (DEN), mice lacking hepatic Rac1 expression were treated with DEN and compared to the wild-type (WT). Rac1 knock-out (KO) mice were found to have a lower tumor yield as compared to Rac1 proficient mice. The small-sized tumors formed in the absence of Rac1 lack an activated Ras/Raf/mitogen-activated protein kinase pathway, as indicated by the absence of p-ERK expression. Apparently, Rac1 is required for Ras-driven oncogenic pathways. Moreover, tumors in Rac1 deficient mice were glutamine synthase (GS) negative. They displayed a high number of p-H3-positive and cyclinB1 expressing cells, pointing to a defect in mitotic progression. To elucidate the influence of Rac1 on mechanisms of tumor initiation, acute DEN-induced hepatic stress responses were monitored. Rac1 deficiency caused fairly complex, partially time-dependent, alterations in both basal and/or DEN-induced messenger RNA (mRNA) and protein levels of susceptibility-related genes. Basal protein expression of DNA repair factors Brca1 and DNA repair protein RAD51 homolog (Rad51) and the cell cycle regulatory factor p27 was enhanced in the absence of Rac1. Following DEN treatment, p21 mRNA and protein expression was stimulated independent of the Rac1 status. Lack of Rac1 increased mechanisms of the DNA damage response (DDR), as shown by elevated protein levels of p-ATR, p-p53 and γH2AX 24h after DEN treatment. The data show that Rac1 is essential for DEN-stimulated hepatocarcinogenesis. We hypothesize that it promotes tumor initiation by counteracting the elimination of initiated cells and, moreover, alleviates the outgrowth of transformed cells. Hence, pharmacological targeting of Rac1 could be suitable for chemoprevention.
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Affiliation(s)
- Anita Bopp
- Institute of Toxicology, Heinrich Heine University Düsseldorf, Moorenstrasse 5, D-40225 Düsseldorf, Germany
| | - Friedrich Wartlick
- Institute of Toxicology, Heinrich Heine University Düsseldorf, Moorenstrasse 5, D-40225 Düsseldorf, Germany
| | - Christian Henninger
- Institute of Toxicology, Heinrich Heine University Düsseldorf, Moorenstrasse 5, D-40225 Düsseldorf, Germany
| | - Michael Schwarz
- Institute of Pharmacology and Toxicology, University Tübingen, Wilhelmstrasse 76, D-72074 Tübingen, Germany
| | - Bernd Kaina
- Institute of Toxicology, University Medical Center Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany and
| | - Gerhard Fritz
- Institute of Toxicology, Heinrich Heine University Düsseldorf, Moorenstrasse 5, D-40225 Düsseldorf, Germany,
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13
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Abe T, Yamazaki D, Murakami S, Hiroi M, Nitta Y, Maeyama Y, Tabata T. The NAV2 homolog Sickie regulates F-actin-mediated axonal growth in Drosophila mushroom body neurons via the non-canonical Rac-Cofilin pathway. Development 2014; 141:4716-28. [DOI: 10.1242/dev.113308] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Rac-Cofilin pathway is essential for cytoskeletal remodeling to control axonal development. Rac signals through the canonical Rac-Pak-LIMK pathway to suppress Cofilin-dependent axonal growth and through a Pak-independent non-canonical pathway to promote outgrowth. Whether this non-canonical pathway converges to promote Cofilin-dependent F-actin reorganization in axonal growth remains elusive. We demonstrate that Sickie, a homolog of the human microtubule-associated protein neuron navigator 2, cell-autonomously regulates axonal growth of Drosophila mushroom body (MB) neurons via the non-canonical pathway. Sickie was prominently expressed in the newborn F-actin-rich axons of MB neurons. A sickie mutant exhibited axonal growth defects, and its phenotypes were rescued by exogenous expression of Sickie. We observed phenotypic similarities and genetic interactions among sickie and Rac-Cofilin signaling components. Using the MARCM technique, distinct F-actin and phospho-Cofilin patterns were detected in developing axons mutant for sickie and Rac-Cofilin signaling regulators. The upregulation of Cofilin function alleviated the axonal defect of the sickie mutant. Epistasis analyses revealed that Sickie suppresses the LIMK overexpression phenotype and is required for Pak-independent Rac1 and Slingshot phosphatase to counteract LIMK. We propose that Sickie regulates F-actin-mediated axonal growth via the non-canonical Rac-Cofilin pathway in a Slingshot-dependent manner.
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Affiliation(s)
- Takashi Abe
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
- Graduate Program in Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - Daisuke Yamazaki
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Satoshi Murakami
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Makoto Hiroi
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Yohei Nitta
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Yuko Maeyama
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Tetsuya Tabata
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
- Graduate Program in Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
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14
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Zhao ZS, Manser E. PAK family kinases: Physiological roles and regulation. CELLULAR LOGISTICS 2014; 2:59-68. [PMID: 23162738 PMCID: PMC3490964 DOI: 10.4161/cl.21912] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The p21-activated kinases (PAKs) are a family of Ser/Thr protein kinases that are represented by six genes in humans (PAK 1-6), and are found in all eukaryotes sequenced to date. Genetic and knockdown experiments in frogs, fish and mice indicate group I PAKs are widely expressed, required for multiple tissue development, and particularly important for immune and nervous system function in the adult. The group II PAKs (human PAKs 4-6) are more enigmatic, but their restriction to metazoans and presence at cell-cell junctions suggests these kinases emerged to regulate junctional signaling. Studies of protozoa and fungal PAKs show that they regulate cell shape and polarity through phosphorylation of multiple cytoskeletal proteins, including microtubule binding proteins, myosins and septins. This chapter discusses what we know about the regulation of PAKs and their physiological role in different model organisms, based primarily on gene knockout studies.
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Affiliation(s)
- Zhuo-Shen Zhao
- sGSK Group; Astar Neuroscience Research Partnership; Singapore
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15
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Coronin1 proteins dictate rac1 intracellular dynamics and cytoskeletal output. Mol Cell Biol 2014; 34:3388-406. [PMID: 24980436 DOI: 10.1128/mcb.00347-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Rac1 regulates lamellipodium formation, myosin II-dependent contractility, and focal adhesions during cell migration. While the spatiotemporal assembly of those processes is well characterized, the signaling mechanisms involved remain obscure. We report here that the cytoskeleton-related Coronin1A and -1B proteins control a myosin II inactivation-dependent step that dictates the intracellular dynamics and cytoskeletal output of active Rac1. This step is signaling-branch specific, since it affects the functional competence of active Rac1 only when forming complexes with downstream ArhGEF7 and Pak proteins in actomyosin-rich structures. The pathway is used by default unless Rac1 is actively rerouted away from the structures by upstream activators and signals from other Rho GTPases. These results indicate that Coronin1 proteins are at the center of a regulatory hub that coordinates Rac1 activation, effector exchange, and the F-actin organization state during cell signaling. Targeting this route could be useful to hamper migration of cancer cells harboring oncogenic RAC1 mutations.
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16
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Keestra AM, Bäumler AJ. Detection of enteric pathogens by the nodosome. Trends Immunol 2013; 35:123-30. [PMID: 24268520 DOI: 10.1016/j.it.2013.10.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 10/23/2013] [Accepted: 10/24/2013] [Indexed: 01/31/2023]
Abstract
Nucleotide-binding oligomerization domain protein (NOD)1 and NOD2 participate in signaling pathways that detect pathogen-induced processes, such as the presence of peptidoglycan fragments in the host cell cytosol, as danger signals. Recent work suggests that peptidoglycan fragments activate NOD1 indirectly, through activation of the small Rho GTPase Ras-related C3 botulinum toxin substrate 1 (RAC1). Excessive activation of small Rho GTPases by virulence factors of enteric pathogens also triggers the NOD1 signaling pathway. Many enteric pathogens use virulence factors that alter the activation state of small Rho GTPases, thereby manipulating the host cell cytoskeleton of intestinal epithelial cells to promote bacterial attachment or entry. These data suggest that the NOD1 signaling pathway in intestinal epithelial cells provides an important sentinel function for detecting 'breaking and entering' by enteric pathogens.
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Affiliation(s)
- A Marijke Keestra
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, One Shields Avenue, Davis CA 95616, USA
| | - Andreas J Bäumler
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, One Shields Avenue, Davis CA 95616, USA.
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17
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Song S, Zhou F, Chen WR. Low-level laser therapy regulates microglial function through Src-mediated signaling pathways: implications for neurodegenerative diseases. J Neuroinflammation 2012; 9:219. [PMID: 22989325 PMCID: PMC3488572 DOI: 10.1186/1742-2094-9-219] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 08/22/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Activated microglial cells are an important pathological component in brains of patients with neurodegenerative diseases. The purpose of this study was to investigate the effect of He-Ne (632.8 nm, 64.6 mW/cm2) low-level laser therapy (LLLT), a non-damaging physical therapy, on activated microglia, and the subsequent signaling events of LLLT-induced neuroprotective effects and phagocytic responses. METHODS To model microglial activation, we treated the microglial BV2 cells with lipopolysaccharide (LPS). For the LLLT-induced neuroprotective study, neuronal cells with activated microglial cells in a Transwell™ cell-culture system were used. For the phagocytosis study, fluorescence-labeled microspheres were added into the treated microglial cells to confirm the role of LLLT. RESULTS Our results showed that LLLT (20 J/cm2) could attenuate toll-like receptor (TLR)-mediated proinflammatory responses in microglia, characterized by down-regulation of proinflammatory cytokine expression and nitric oxide (NO) production. LLLT-triggered TLR signaling inhibition was achieved by activating tyrosine kinases Src and Syk, which led to MyD88 tyrosine phosphorylation, thus impairing MyD88-dependent proinflammatory signaling cascade. In addition, we found that Src activation could enhance Rac1 activity and F-actin accumulation that typify microglial phagocytic activity. We also found that Src/PI3K/Akt inhibitors prevented LLLT-stimulated Akt (Ser473 and Thr308) phosphorylation and blocked Rac1 activity and actin-based microglial phagocytosis, indicating the activation of Src/PI3K/Akt/Rac1 signaling pathway. CONCLUSIONS The present study underlines the importance of Src in suppressing inflammation and enhancing microglial phagocytic function in activated microglia during LLLT stimulation. We have identified a new and important neuroprotective signaling pathway that consists of regulation of microglial phagocytosis and inflammation under LLLT treatment. Our research may provide a feasible therapeutic approach to control the progression of neurodegenerative diseases.
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Affiliation(s)
- Sheng Song
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, No, 55 Zhongshan Avenue West, Guangzhou, Tianhe District, 510631, China
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18
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Arrizabalaga O, Lacerda HM, Zubiaga AM, Zugaza JL. Rac1 protein regulates glycogen phosphorylase activation and controls interleukin (IL)-2-dependent T cell proliferation. J Biol Chem 2012; 287:11878-90. [PMID: 22337875 DOI: 10.1074/jbc.m111.297804] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Small GTPases of the Rho family have been implicated in important cellular processes such as cell migration and adhesion, protein secretion, and/or gene transcription. In the lymphoid system, these GTPases participate in the signaling cascades that are activated after engagement of antigen receptors. However, little is known about the role that Rho GTPases play in IL-2-mediated responses. Here, we show that IL-2 induces Rac1 activation in Kit 225 T cells. We identified by mass spectrometry the muscle isoform of glycogen phosphorylase (PYGM) as a novel Rac1 effector molecule in IL-2-stimulated cells. The interaction between the active form of Rac1 (Rac1-GTP) and PYGM was established directly through a domain comprising amino acids 191-270 of PYGM that exhibits significant homology with the Rac binding domain of PAK1. The integrity of this region was crucial for PYGM activation. Importantly, IL-2-dependent cellular proliferation was inhibited upon blocking both the activation of Rac1 and the activity of PYGM. These results reveal a new role for Rac1 in cell signaling, showing that this GTPase triggers T cell proliferation upon IL-2 stimulation by associating with PYGM and modulating its enzymatic activity.
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Affiliation(s)
- Onetsine Arrizabalaga
- Department of Genetics, Physical Anthropology and Animal Physiology, University of the Basque Country, 48940 Leioa, Spain
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19
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Vicente-Manzanares M, Newell-Litwa K, Bachir AI, Whitmore LA, Horwitz AR. Myosin IIA/IIB restrict adhesive and protrusive signaling to generate front-back polarity in migrating cells. ACTA ACUST UNITED AC 2011; 193:381-96. [PMID: 21482721 PMCID: PMC3080254 DOI: 10.1083/jcb.201012159] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Migratory front-back polarity emerges from the cooperative effect of myosin IIA (MIIA) and IIB (MIIB) on adhesive signaling. We demonstrate here that, during polarization, MIIA and MIIB coordinately promote localized actomyosin bundling, which generates large, stable adhesions that do not signal to Rac and thereby form the cell rear. MIIA formed dynamic actomyosin proto-bundles that mark the cell rear during spreading; it also bound to actin filament bundles associated with initial adhesion maturation in protrusions. Subsequent incorporation of MIIB stabilized the adhesions and actomyosin filaments with which it associated and formed a stable, extended rear. These adhesions did not turn over and no longer signal to Rac. Microtubules fine-tuned the polarity by positioning the front opposite the MIIA/MIIB-specified rear. Decreased Rac signaling in the vicinity of the MIIA/MIIB-stabilized proto-bundles and adhesions was accompanied by the loss of Rac guanine nucleotide exchange factor (GEFs), like βPIX and DOCK180, and by inhibited phosphorylation of key residues on adhesion proteins that recruit and activate Rac GEFs. These observations lead to a model for front-back polarity through local GEF depletion.
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Affiliation(s)
- Miguel Vicente-Manzanares
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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20
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Ball RW, Warren-Paquin M, Tsurudome K, Liao EH, Elazzouzi F, Cavanagh C, An BS, Wang TT, White JH, Haghighi AP. Retrograde BMP signaling controls synaptic growth at the NMJ by regulating trio expression in motor neurons. Neuron 2010; 66:536-49. [PMID: 20510858 DOI: 10.1016/j.neuron.2010.04.011] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/02/2010] [Indexed: 10/19/2022]
Abstract
Retrograde signaling is essential for coordinating the growth of synaptic structures; however, it is not clear how it can lead to modulation of cytoskeletal dynamics and structural changes at presynaptic terminals. We show that loss of retrograde bone morphogenic protein (BMP) signaling at the Drosophila larval neuromuscular junction (NMJ) leads to a significant reduction in levels of Rac GEF Trio and a diminution of transcription at the trio locus. We further find that Trio is required in motor neurons for normal structural growth. Finally, we show that transgenic expression of Trio in motor neurons can partially restore NMJ defects in larvae mutant for BMP signaling. Based on our findings, we propose a model in which a retrograde BMP signal from the muscle modulates GTPase activity through transcriptional regulation of Rac GEF trio, thereby regulating the homeostasis of synaptic growth at the NMJ.
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Affiliation(s)
- Robin W Ball
- Department of Physiology, McGill University, Montréal, QC H3G 1Y6, Canada
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21
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Sauzeau V, Berenjeno IM, Citterio C, Bustelo XR. A transcriptional cross-talk between RhoA and c-Myc inhibits the RhoA/Rock-dependent cytoskeleton. Oncogene 2010; 29:3781-92. [PMID: 20453885 PMCID: PMC2896432 DOI: 10.1038/onc.2010.134] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The GTPase RhoA participates in a number of cellular processes, including cytoskeletal organization, mitogenesis and tumorigenesis. We have previously shown that the transforming activity of an oncogenic version of RhoA (Q63L mutant) was highly dependent on the transcriptional factor c–Myc. In contrast to these positive effects in the RhoA route, we show here that c–Myc affects negatively the F–actin cytoskeleton induced by RhoAQ63L and its downstream effector, the serine/threonine kinase Rock. This effect entails the activation of a transcriptional program that requires synergistic interactions with RhoA–derived signals and that includes the upregulation of the GTPase Cdc42 and its downstream element Pak1 as well as the repression of specific integrin subunits. The negative effects of c–Myc in the F–actin cytoskeleton are eliminated by the establishment of cell–to–cell contacts, an effect associated with the rescue of Pak1 and integrin levels at the post–transcriptional and transcriptional levels, respectively. These results reveal the presence of a hitherto unknown signaling feed–back loop between RhoA and c–Myc oncogenes that can contribute to maintain fluid cytoskeletal dynamics in cancer cells.
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Affiliation(s)
- V Sauzeau
- Centro de Investigación del Cáncer, CSIC-University of Salamanca, Campus Unamuno, Salamanca, Spain
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22
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Forgetting is regulated through Rac activity in Drosophila. Cell 2010; 140:579-89. [PMID: 20178749 DOI: 10.1016/j.cell.2009.12.044] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 11/06/2009] [Accepted: 12/22/2009] [Indexed: 11/23/2022]
Abstract
Initially acquired memory dissipates rapidly if not consolidated. Such memory decay is thought to result either from the inherently labile nature of newly acquired memories or from interference by subsequently attained information. Here we report that a small G protein Rac-dependent forgetting mechanism contributes to both passive memory decay and interference-induced forgetting in Drosophila. Inhibition of Rac activity leads to slower decay of early memory, extending it from a few hours to more than one day, and to blockade of interference-induced forgetting. Conversely, elevated Rac activity in mushroom body neurons accelerates memory decay. This forgetting mechanism does not affect memory acquisition and is independent of Rutabaga adenylyl cyclase-mediated memory formation mechanisms. Endogenous Rac activation is evoked on different time scales during gradual memory loss in passive decay and during acute memory removal in reversal learning. We suggest that Rac's role in actin cytoskeleton remodeling may contribute to memory erasure.
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23
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Mohamadnejad M, Sohail MA, Watanabe A, Krause DS, Swenson ES, Mehal WZ. Adenosine inhibits chemotaxis and induces hepatocyte-specific genes in bone marrow mesenchymal stem cells. Hepatology 2010; 51:963-73. [PMID: 20044808 PMCID: PMC2840188 DOI: 10.1002/hep.23389] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
UNLABELLED Bone marrow-derived mesenchymal stem cells (MSCs) have therapeutic potential in liver injury, but the signals responsible for MSC localization to sites of injury and initiation of differentiation are not known. Adenosine concentration is increased at sites of cellular injury and inflammation, and adenosine is known to signal a variety of cellular changes. We hypothesized that local elevations in the concentration of adenosine at sites of tissue injury regulate MSC homing and differentiation. Here we demonstrate that adenosine does not induce MSC chemotaxis but dramatically inhibits MSC chemotaxis in response to the chemoattractant hepatocyte growth factor (HGF). Inhibition of HGF-induced chemotaxis by adenosine requires the A2a receptor and is mediated via up-regulation of the cyclic adenosine monophosphate (AMP)/protein kinase A pathway. This results in inhibition of cytosolic calcium signaling and down-regulation of HGF-induced Rac1. Because of the important role of Rac1 in the formation of actin stress fibers, we examined the effect of adenosine on stress fiber formation and found that adenosine inhibits HGF-induced stress fiber formation. In addition, we found that adenosine induces the expression of some key endodermal and hepatocyte-specific genes in mouse and human MSCs in vitro. CONCLUSION We propose that the inhibition of MSC chemotaxis at sites of high adenosine concentration results in localization of MSCs to areas of cellular injury and death in the liver. We speculate that adenosine might initiate the process of differentiation of MSCs into hepatocyte-like cells.
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Affiliation(s)
- Mehdi Mohamadnejad
- Yale University, School of Medicine, Department of Internal Medicine, Section of Digestive Diseases, New Haven, CT, USA, Digestive Disease Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Muhammad A Sohail
- Yale University, School of Medicine, Department of Internal Medicine, Section of Digestive Diseases, New Haven, CT, USA
| | - Azuma Watanabe
- Yale University, School of Medicine, Department of Internal Medicine, Section of Digestive Diseases, New Haven, CT, USA
| | - Diane S Krause
- Yale University, School of Medicine, Department of Laboratory Medicine, New Haven, CT, USA
| | - E Scott Swenson
- Yale University, School of Medicine, Department of Internal Medicine, Section of Digestive Diseases, New Haven, CT, USA
| | - Wajahat Z Mehal
- Yale University, School of Medicine, Department of Internal Medicine, Section of Digestive Diseases, New Haven, CT, USA
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24
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Sauzeau V, Sevilla MA, Montero MJ, Bustelo XR. The Rho/Rac exchange factor Vav2 controls nitric oxide-dependent responses in mouse vascular smooth muscle cells. J Clin Invest 2009; 120:315-30. [PMID: 20038798 DOI: 10.1172/jci38356] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Accepted: 10/14/2009] [Indexed: 01/21/2023] Open
Abstract
The regulation of arterial contractility is essential for blood pressure control. The GTPase RhoA promotes vasoconstriction by modulating the cytoskeleton of vascular smooth muscle cells. Whether other Rho/Rac pathways contribute to blood pressure regulation remains unknown. By studying a hypertensive knockout mouse lacking the Rho/Rac activator Vav2, we have discovered a new signaling pathway involving Vav2, the GTPase Rac1, and the serine/threonine kinase Pak that contributes to nitric oxide-triggered blood vessel relaxation and normotensia. This pathway mediated the Pak-dependent inhibition of phosphodiesterase type 5, a process that favored RhoA inactivation and the subsequent depolymerization of the F-actin cytoskeleton in vascular smooth muscle cells. The inhibition of phosphodiesterase type 5 required its physical interaction with autophosphorylated Pak1 but, unexpectedly, occurred without detectable transphosphorylation events between those 2 proteins. The administration of phosphodiesterase type 5 inhibitors prevented the development of hypertension and cardiovascular disease in Vav2-deficient animals, demonstrating the involvement of this new pathway in blood pressure regulation. Taken together, these results unveil one cause of the cardiovascular phenotype of Vav2-knockout mice, identify a new Rac1/Pak1 signaling pathway, and provide a mechanistic framework for better understanding blood pressure control in physiological and pathological states.
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Affiliation(s)
- Vincent Sauzeau
- Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer, CSIC-University of Salamanca, Campus Unamuno, Salamanca, Spain
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25
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Bustos RI, Forget MA, Settleman JE, Hansen SH. Coordination of Rho and Rac GTPase function via p190B RhoGAP. Curr Biol 2008; 18:1606-11. [PMID: 18948007 DOI: 10.1016/j.cub.2008.09.019] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Revised: 09/08/2008] [Accepted: 09/09/2008] [Indexed: 12/30/2022]
Abstract
The Rac GTPase regulates Rho signaling in a broad range of physiological settings and in oncogenic transformation [1-3]. Here, we report a novel mechanism by which crosstalk between Rac and Rho GTPases is achieved. Activated Rac1 binds directly to p190B Rho GTPase-activating protein (RhoGAP), a major modulator of Rho signaling. p190B colocalizes with constitutively active Rac1 in membrane ruffles. Moreover, activated Rac1 is sufficient to recruit p190B into a detergent-insoluble membrane fraction, a process that is accompanied by a decrease in GTP-bound RhoA from membranes. p190B is recruited to the plasma membrane in response to integrin engagement [4]. We demonstrate that collagen type I, a potent inducer of Rac1-dependent cell motility in HeLa cells, counteracts cytoskeletal collapse resulting from overexpression of wild-type p190B, but not that resulting from overexpression of a p190B mutant specifically lacking the Rac1-binding sequence. Furthermore, this p190B mutant exhibits dramatically enhanced RhoGAP activity, consistent with a model whereby binding of Rac1 relieves autoinhibition of p190B RhoGAP function. Collectively, these observations establish that activated Rac1, through direct interaction with p190B, modulates subcellular RhoGAP localization and activity, thereby providing a novel mechanism for Rac control of Rho signaling in a broad range of physiological processes.
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Affiliation(s)
- Rodrigo I Bustos
- GI Cell Biology Laboratory, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts 02115, USA
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26
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Caloca MJ, Zugaza JL, Bustelo XR. Mechanistic analysis of the amplification and diversification events induced by Vav proteins in B-lymphocytes. J Biol Chem 2008; 283:36454-64. [PMID: 18974050 DOI: 10.1074/jbc.m803814200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Vav proteins participate in the assembly of a multibranched signal transduction pathway in lymphocytes, including the stimulation of the phosphatidylinositol 3-kinase/protein kinase B and the phospholipase C-gamma/Ras GDP-releasing protein/Ras/Erk routes. In the present work, we used a genetic approach in chicken DT40 B-cell lines to investigate additional elements of the Vav route, the synergisms existing among the different Vav signaling branches, and the activities exerted by wild-type and oncogenic Vav proteins in B-lymphocytes. We show here that the Vav pathway is ramified in B-lymphocytes in additional diacylglycerol-dependent signaling branches such as those involving protein kinase C, protein kinase D, and phospholipase D. By using side-by-side comparisons of the activation levels of those signal transduction pathways in inhibitor-treated and knockout DT40 cells, we show that B-cells have different requirements regarding Vav proteins for the activation of antigen receptor downstream elements. Furthermore, we have detected interpathway cross-talk at the level of the most proximal elements but not among the most distal effector molecules of the Vav route. Finally, we show that the oncogenic versions of Vav1 and RhoA can activate alternative routes that could contribute to signal amplification and diversification events in transformed lymphocytes.
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Affiliation(s)
- María J Caloca
- Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas, University of Salamanca, Campus Unamuno, Salamanca E-37007, Spain
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27
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Tscharntke M, Pofahl R, Chrostek-Grashoff A, Smyth N, Niessen C, Niemann C, Hartwig B, Herzog V, Klein HW, Krieg T, Brakebusch C, Haase I. Impaired epidermal wound healing in vivo upon inhibition or deletion of Rac1. J Cell Sci 2007; 120:1480-90. [PMID: 17389689 DOI: 10.1242/jcs.03426] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
To address the functions of Rac1 in keratinocytes of the basal epidermal layer and in the outer root sheath of hair follicles, we generated transgenic mice expressing a dominant inhibitory mutant of Rac, N17Rac1, under the control of the keratin 14 promoter. These mice do not exhibit an overt skin phenotype but show protracted skin wound re-epithelialization. Investigation into the underlying mechanisms revealed that in vivo both proliferation of wound-edge keratinocytes and centripetal migration of the neo-epidermis were impaired. Similar results were obtained in mice with an epidermis-specific deletion of Rac1. Primary epidermal keratinocytes that expressed the N17Rac1 transgene were less proliferative than control cells and showed reduced ERK1/2 phosphorylation upon growth factor stimulation. Adhesion, spreading, random migration and closure of scratch wounds in vitro were significantly inhibited on collagen I and, to a lesser extent, on fibronectin. Stroboscopic analysis of cell dynamics (SACED) of N17Rac1 transgenic and control keratinocytes identified decreased lamella-protrusion persistence in connection with increased ruffle frequency as a probable mechanism for the observed impairment of keratinocyte adhesion and migration. We conclude that Rac1 is functionally required for normal epidermal wound healing and, in this context, exerts a dual function - namely the regulation of keratinocyte proliferation and migration.
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Affiliation(s)
- Michael Tscharntke
- Department of Dermatology, University of Cologne, Center for Molecular Medicine, (CMMC), Joseph-Stelzmann-Strasse 9, 50924 Cologne, Germany
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28
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Williams MJ, Habayeb MS, Hultmark D. Reciprocal regulation of Rac1 and Rho1 inDrosophilacirculating immune surveillance cells. J Cell Sci 2007; 120:502-11. [PMID: 17227793 DOI: 10.1242/jcs.03341] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In many cell types it is evident that the small GTPases Rac and Rho regulate each other's activities. What is unclear is exactly how this regulation occurs. To further elucidate this interaction we examined the activities of Rac1 and Rho1 in Drosophila cellular immune surveillance cells. In larvae the cellular immune response involves circulating cells (hemocytes) that can be recruited from a hematopoietic organ located behind the brain, as well as a sessile population found just underneath the larval cuticle. We demonstrate for the first time that Rho-kinase activation requires both Rho1 and the Drosophila c-Jun N-terminal kinase (Basket). We also show that Rac1, via Basket, regulates Rho1 activity, possibly by inhibiting RhoGAPp190. In the reciprocal pathway, co-expression of dominant negative Rho-kinase and constitutive active Rho1 induces a Rac1-like phenotype. This induction requires the formin Diaphanous. Co-expression of dominant negative Rho-kinase and constitutive active Rho1 also induces filopodia formation, with Diaphanous enriched at the tips. The Rac1-like phenotypes, and filopodia formation, could be blocked by co-expression of dominant negative Rac1. Finally, though dominant negative Rac1 is able to block filopodia formation in the overexpression experiments, only Rac2 is necessary for filopodia formed by hemocytes after parasitization.
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Affiliation(s)
- Michael J Williams
- Umeå Centre for Molecular Pathogenesis (UCMP), Umeå University, S-901 87, Umeå, Sweden.
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29
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Morley S, Wagner J, Kauppinen K, Sherman M, Manor D. Requirement for Akt-mediated survival in cell transformation by the dbl oncogene. Cell Signal 2007; 19:211-8. [PMID: 16916597 DOI: 10.1016/j.cellsig.2006.06.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2006] [Accepted: 06/29/2006] [Indexed: 01/20/2023]
Abstract
The dbl oncogene product is the founding member of a large family of oncogenic proteins that function by activating the small GTP-binding proteins Cdc42, Rac and Rho. Through its substrate GTPases, Dbl transduces proliferative signals from cell-surface receptors to diverse cellular effectors and signaling pathways. The mechanisms by which these multiple signals are integrated, as well as their relative contribution to Dbl-induced cell transformation, are presently poorly understood. We investigated the role of the survival regulators PI3-kinase and Akt in Dbl-induced cell transformation. We found that Dbl induced the phosphorylation of Akt on threonine 308, through the GTPases Rac and Cdc42 and in a PI3-kinase dependent manner. Pharmacological or biochemical interference with this pathway lead to a marked, dose-dependent inhibition of the focus formation activity exhibited by Dbl-expressing cells. Dbl expression stimulated the phosphorylation of the anti-apoptotic Akt substrate Bad, and caused a marked decrease in basal levels of apoptosis. Finally, we found that activated Cdc42 existed in cells in complex with phosphoionositide-dependent kinase-1 (PDK1), the downstream mediator of PI3-kinase action. The data indicate that Dbl signaling stimulate the formation of a novel survival complex, through which anti-apoptotic signals are generated and propagated.
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Affiliation(s)
- S Morley
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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30
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Oka T, Ihara S, Fukui Y. Cooperation of DEF6 with activated Rac in regulating cell morphology. J Biol Chem 2006; 282:2011-8. [PMID: 17121847 DOI: 10.1074/jbc.m605153200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Rho-family GTPases have been implicated in actin remodeling and subsequent morphologic changes in various cells. DEF6, a pleckstrin homology domain-containing protein, has been reported to regulate Rho-family GTPases as a guanine nucleotide exchange factor. Here, we demonstrate that DEF6 also has the property of cooperating with activated Rac1. DEF6 bound selectively to Rac1 loaded with GTP. The interaction is mediated by the effector domain of Rac1. Overexpression of GFP-DEF6 together with constitutively active Rac1 in COS-7 cells significantly changed their cell shape; this was not seen in the absence of activated Rac1. This effect of DEF6 on cellular morphology was shown to be independent of its guanine nucleotide exchange activity. Because DEF6 does not contain any sequences previously known to interact with Rac, we explored the domain necessary for the binding. The amino-terminal portion and central parts of DEF6 were required for the binding. Finally, we succeeded in creating mutants of DEF6 with point mutations in the amino-terminal portion, which abrogate the binding to activated Rac1. These mutants did not exhibit the morphologic change in COS-7 cells when they were co-expressed with activated Rac1. These results suggest that DEF6 not only activates Rho-family GTPases but also cooperates with activated Rac1 to exert its cellular function.
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Affiliation(s)
- Tsutomu Oka
- Division of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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31
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Mills JB, Mant CT, Hodges RS. One-step purification of a recombinant protein from a whole cell extract by reversed-phase high-performance liquid chromatography. J Chromatogr A 2006; 1133:248-53. [PMID: 16945380 PMCID: PMC2722115 DOI: 10.1016/j.chroma.2006.08.042] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Revised: 08/11/2006] [Accepted: 08/15/2006] [Indexed: 11/30/2022]
Abstract
We have developed a one-step facile, flexible and readily scalable purification method for a recombinant protein, TM 1-99 (113 amino acid residues; 12,837 Da) based on reversed-phase high-performance liquid chromatography (RP-HPLC) from an E. coli cell lysate. Following cell lysis, the cell contents were extracted with 0.1% aqueous trifluoroacetic acid (TFA), applied directly under conditions of high sample load to a narrow bore RP-HPLC C(8) column (150 mm x 2.1 mm I.D.) and eluted by a shallow gradient of acetonitrile (0.1%/min). Loads of 23 and 48 mg of lyophilized crude cell extract produced 2.4 and 4.2mg of purified product (>94% pure), respectively, at >94% recovery. Our results show the excellent potential of one-step RP-HPLC for purification of recombinant proteins from cell lysates, where high yields of purified product and greater purity are achieved compared to affinity chromatography. Such an approach was also successful in purifying just trace levels (<0.1% of total contents of crude sample) of TM 1-99 from a cell lysate.
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Affiliation(s)
| | | | - Robert S. Hodges
- Corresponding author. Tel.: +1 303 724 3253. E-mail address: (R.S. Hodges)
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32
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Prieto-Sánchez RM, Berenjeno IM, Bustelo XR. Involvement of the Rho/Rac family member RhoG in caveolar endocytosis. Oncogene 2006; 25:2961-73. [PMID: 16568096 PMCID: PMC1463992 DOI: 10.1038/sj.onc.1209333] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We show here that the GTPase RhoG is involved in caveolar trafficking. Wild-type RhoG moves sequentially to the plasma membrane, intracellular vesicles, and the Golgi apparatus along markers of this endocytic pathway. Such translocation is associated with changes in RhoG GDP/GTP levels and is highly dependent on lipid raft integrity and on the function of the GTPase dynamin2. In addition, the constitutively active RhoG(Q61L) mutant is preferentially located in endocytic vesicles that can be decorated with markers of the caveola-derived endocytic pathway. RhoG(Q61L), but not the analogous Rac1 mutant protein, affects caveola internalization and the subsequent delivery of endocytic vesicles to the Golgi apparatus. The expression of RhoG/Rac1 chimeric proteins and RhoG(Q61L) effector mutants in cells induces alterations in the internalization of caveolae and severe changes in vesicle structure, respectively. However, the knockdown of endogenous rhoG transcripts using small interfering RNAs does not affect significantly the trafficking of caveola-derived vesicles, suggesting that RhoG function is dispensable for this endocytic process or, alternatively, that its function is compensated by other molecules. Taken together, these observations assign a novel function to RhoG and suggest that caveolar trafficking, as previously shown for other endocytic routes, is modulated by GTPases of the Ras superfamily.
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Affiliation(s)
| | | | - XR Bustelo
- Correspondence: Dr XR Bustelo, Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer (IBMCC), and Red Temática Cooperativa de Centros de Cáncer, CSIC-University of Salamanca, Campus Unamuno, E-37007 Salamanca, Spain. E-mail:
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33
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Volinsky N, Gantman A, Yablonski D. A Pak- and Pix-dependent branch of the SDF-1alpha signalling pathway mediates T cell chemotaxis across restrictive barriers. Biochem J 2006; 397:213-22. [PMID: 16515536 PMCID: PMC1479756 DOI: 10.1042/bj20051655] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Pak (p21-activated kinase) serine/threonine kinases have been shown to mediate directional sensing of chemokine gradients. We hypothesized that Pak may also mediate chemokine-induced shape changes, to facilitate leucocyte chemotaxis through restrictive barriers, such as the extracellular matrix. A potent inhibitor, Pak(i), was characterized and used to probe the role of Pak-family kinases in SDF-1alpha (stromal-cell derived factor-1alpha/CXCL12)-induced chemotaxis in a T cell model. Pak(i) potently inhibited SDF-1alpha-induced Pak activation by a bivalent mechanism, as indicated by its complete inactivation upon point mutation of two binding sites, but partial inactivation upon mutation of either site alone. Importantly, Pak(i) was not toxic to cells over the time frame of our experiments, since it did not substantially affect cell surface expression of CXCR4 (CXC chemokine receptor 4) or integrins, cell cycle progression, or a number of ligand-induced responses. Pak(i) produced dose-dependent inhibition of SDF-1alpha-induced migration through rigid filters bearing small pores; but unexpectedly, did not substantially affect the magnitude or kinetics of chemotaxis through filters bearing larger pores. SDF-1alpha-induced Pak activation was partly dependent on PIX (Pak-interactive exchange factor); correspondingly, an allele of beta-PIX that cannot bind Pak inhibited SDF-1alpha-induced chemotaxis through small, but not large pores. By contrast, other key players in chemotaxis: G(i), PI3K (phosphoinositide 3-kinase), and the Rho-family G-proteins, Rac and Cdc42 (cell division cycle 42), were required for SDF-1alpha-induced migration regardless of the barrier pore-size. These studies have revealed a distinct branch of the SDF-1alpha signalling pathway, in which the Rac/Cdc42 effector, Pak, and its partner, PIX, specifically regulate the cellular events required for chemokine-induced migration through restrictive barriers.
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Affiliation(s)
- Natalia Volinsky
- The Rappaport Family Institute for Research in the Medical Sciences, Bruce Rappaport Faculty of Medicine, Technion – Israel Institute of Technology, P.O. Box 9649, Bat Galim, Haifa 31096, Israel
| | - Anna Gantman
- The Rappaport Family Institute for Research in the Medical Sciences, Bruce Rappaport Faculty of Medicine, Technion – Israel Institute of Technology, P.O. Box 9649, Bat Galim, Haifa 31096, Israel
| | - Deborah Yablonski
- The Rappaport Family Institute for Research in the Medical Sciences, Bruce Rappaport Faculty of Medicine, Technion – Israel Institute of Technology, P.O. Box 9649, Bat Galim, Haifa 31096, Israel
- To whom correspondence should be addressed (email )
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34
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Rhee S, Grinnell F. P21-activated kinase 1: convergence point in PDGF- and LPA-stimulated collagen matrix contraction by human fibroblasts. ACTA ACUST UNITED AC 2006; 172:423-32. [PMID: 16449192 PMCID: PMC2063651 DOI: 10.1083/jcb.200505175] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Fibroblast three-dimensional collagen matrix culture provides a tissue-like model that can be used to analyze cell form and function. The physiological agonists platelet-derived growth factor (PDGF) and lysophosphatidic acid (LPA) both stimulate human fibroblasts to contract floating collagen matrices. In this study, we show that the PDGF and LPA signaling pathways required for matrix contraction converge on p21-activated kinase 1 (PAK1) and its downstream effector cofilin1 and that contraction depends on cellular ruffling activity, rather than on the protrusion and retraction of cellular dendritic extensions. We also show that, depending on the agonist, different Rho effectors cooperate with PAK1 to regulate matrix contraction, Rho kinase in the case of PDGF and mDia1 in the case of LPA. These findings establish a unified framework for understanding the cell signaling pathways involved in fibroblast contraction of floating collagen matrices.
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Affiliation(s)
- Sangmyung Rhee
- Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, TX 75390, USA
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35
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Williams MJ, Wiklund ML, Wikman S, Hultmark D. Rac1 signalling in the Drosophila larval cellular immune response. J Cell Sci 2006; 119:2015-24. [PMID: 16621891 DOI: 10.1242/jcs.02920] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Drosophila larval cellular immune response involves cells (hemocytes) that can be recruited from a hematopoietic organ located behind the brain, as well as a sessile population of cells found just underneath the larval cuticle arranged in a segmental pattern. By using two Rac1 GTPase effector-loop mutants together with epistasis studies, we show that Rac1 requires the Drosophila melanogaster Jun N-terminal kinase Basket (Bsk), as well as stable actin formation to recruit the sessile hemocyte population. We show that actin stabilization is necessary for Rac1-induced hemocyte activation by lowering cofilin (encoded by the twinstar gene tsr) expression in blood cells. Removing Bsk by RNAi suppressed Rac1-induced release of sessile hemocytes. RNAi against Bsk also suppressed Rac1 induction of lamellocytes, a specialized population of hemocytes necessary for the encapsulation of invading pathogens. Furthermore, Rac1 and Bsk are involved in regulating the formation of actin- and focal adhesion kinase (FAK)-rich placodes in hemocytes. Lastly, Rac1 and Bsk are both required for the proper encapsulation of eggs from the parasitoid wasp Leptipolina boulardi. From these data we conclude that Rac1 induces Bsk activity and stable actin formation for cellular immune activation, leading to sessile hemocyte release and an increase in the number of circulating hemocytes.
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Affiliation(s)
- Michael J Williams
- Umeå Centre for Molecular Pathogenesis (UCMP), Umeå University, S-901 87, Umeå, Sweden.
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36
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Pullar CE, Isseroff RR. The β2-adrenergic receptor activates pro-migratory and pro-proliferative pathways in dermal fibroblasts via divergent mechanisms. J Cell Sci 2006; 119:592-602. [PMID: 16443756 DOI: 10.1242/jcs.02772] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Dermal fibroblasts are required for skin wound repair; they migrate into the wound bed, proliferate, synthesize extracellular matrix components and contract the wound. Although fibroblasts express β2-adrenergic receptors (β2-AR) and cutaneous keratinocytes can synthesize β-AR agonists (catecholamines), the functional significance of this hormonal mediator network in the skin has not been addressed. Emerging studies from our laboratory demonstrate that β2-AR activation modulates keratinocyte migration, essential for wound re-epithelialization. Here we describe an investigation of the effects of β2-AR activation on the dermal component of wound healing. We examined β2-AR-mediated regulation of biological processes in dermal fibroblasts that are critical for wound repair: migration, proliferation, contractile ability and cytoskeletal conformation.We provide evidence for the activation of at least two divergent β2-AR-mediated signaling pathways in dermal fibroblasts, a Src-dependent pro-migratory pathway, transduced through the epidermal growth factor receptor and extracellular signal-regulated kinase, and a PKA-dependent pro-proliferative pathway. β2-AR activation attenuates collagen gel contraction and alters the actin cytoskeleton and focal adhesion distribution through PKA-dependent mechanisms. Our work uncovers a previously unrecognized role for the adrenergic hormonal mediator network in the cutaneous wound repair process. Exploiting these divergent β2-AR agonist responses in cutaneous cells may generate novel therapeutic approaches for the control of wound healing.
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Affiliation(s)
- Christine E Pullar
- Department of Dermatology, University of California, Davis, TB 192, One Shields Avenue, CA 95616, USA.
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37
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Toschi E, Bacigalupo I, Strippoli R, Chiozzini C, Cereseto A, Falchi M, Nappi F, Sgadari C, Barillari G, Mainiero F, Ensoli B. HIV-1 Tat regulates endothelial cell cycle progression via activation of the Ras/ERK MAPK signaling pathway. Mol Biol Cell 2006; 17:1985-94. [PMID: 16436505 PMCID: PMC1415297 DOI: 10.1091/mbc.e05-08-0717] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Tat, the transactivator of HIV-1 gene expression, is released by acutely HIV-1-infected T-cells and promotes adhesion, migration, and growth of inflammatory cytokine-activated endothelial and Kaposi's sarcoma cells. It has been previously demonstrated that these effects of Tat are due to its ability to bind through its arginine-glycine-aspartic (RGD) region to the alpha5beta1 and alphavbeta3 integrins. However, the signaling pathways linking Tat to the regulation of cellular functions are incompletely understood. Here, we report that Tat ligation on human endothelial cells results in the activation of the small GTPases Ras and Rac and the mitogen-activated protein kinase ERK, specifically through its RGD region. In addition, we demonstrated that Tat activation of Ras, but not of Rac, induces ERK phosphorylation. We also found that the receptor proximal events accompanying Tat-induced Ras activation are mediated by tyrosine phosphorylation of Shc and recruitment of Grb2. Moreover, Tat enabled endothelial cells to progress through the G1 phase in response to bFGF, and the process is linked to ERK activation. Taken together, these data provide novel evidence about the ability of Tat to activate the Ras-ERK cascade which may be relevant for endothelial cell proliferation and for Kaposi's sarcoma progression.
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Affiliation(s)
- Elena Toschi
- AIDS National Center, Istituto Superiore di Sanità, 00161 Rome, Italy
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38
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Abstract
Our initial characterization of Rac3, a close relative of the small GTPase Rac1, established its ability to promote membrane ruffling, transformation, and activation of c-jun transcriptional activity. The finding that Rac3 is transforming, and its similarity to Rac1, a protein that has a well-established connection to many processes important for cancer progression, prompted further investigation into Rac3 transformation. We used effector domain mutants (EDMs) to explore the relationship among Rac signaling, transformation, and effector usage. All Rac3 EDMs tested (N26D, F37L, Y40C, and N43D) retained the ability to promote membrane ruffling and focus formation. In contrast, only the N43D mutant promoted anchorage independence. This differs from Rac1, where both N26D and N43D mutants were impaired in both types of transformation. To learn more about the signaling pathways involved, we did luciferase reporter assays and glutathione S-transferase pull-down assays for effector binding. We found evidence for a functional link between activation of phospholipase Cbeta2 by Rac3 and signaling to the serum response factor (SRF). Surprisingly, we also found that Rac3 binds poorly to the known Rac1 effectors mixed lineage kinases 2 and 3 (MLK2 and MLK3). Transcription of cyclin D1 was the only pathway that correlated with growth in soft agar. Our experiments show that activation of membrane ruffling and transcriptional activation of c-jun, SRF, or E2F are not sufficient to promote anchorage-independent growth mediated by Rac3. Instead, multiple effector pathways are required for Rac3 transformation, and these overlap partially but not completely with those used by Rac1.
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Affiliation(s)
- Patricia J Keller
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7512, USA
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39
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Travaglione S, Messina G, Fabbri A, Falzano L, Giammarioli AM, Grossi M, Rufini S, Fiorentini C. Cytotoxic necrotizing factor 1 hinders skeletal muscle differentiation in vitro by perturbing the activation/deactivation balance of Rho GTPases. Cell Death Differ 2005; 12:78-86. [PMID: 15514676 DOI: 10.1038/sj.cdd.4401522] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The current knowledge assigns a crucial role to the Rho GTPases family (Rho, Rac, Cdc42) in the complex transductive pathway leading to skeletal muscle cell differentiation. Their exact function in myogenesis, however, remains largely undefined. The protein toxin CNF1 was herein employed as a tool to activate Rho, Rac and Cdc42 in the myogenic cell line C2C12. We demonstrated that CNF1 impaired myogenesis by affecting the muscle regulatory factors MyoD and myogenin and the structural protein MHC expressions. This was principally driven by Rac/Cdc42 activation whereas Rho apparently controlled only the fusion process. More importantly, we proved that a controlled balance between Rho and Rac/Cdc42 activation/deactivation state was crucial for the correct execution of the differentiation program, thus providing a novel view for the role of Rho GTPases in muscle cell differentiation. Also, the use of Rho hijacking toxins can represent a new strategy to pharmacologically influence the differentiative process.
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Affiliation(s)
- S Travaglione
- Department of Drug Research and Evaluation, Istituto Superiore di Sanità, Viale Regina 299, 00161 Rome, Italy
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40
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Cho YJ, Zhang B, Kaartinen V, Haataja L, de Curtis I, Groffen J, Heisterkamp N. Generation of rac3 null mutant mice: role of Rac3 in Bcr/Abl-caused lymphoblastic leukemia. Mol Cell Biol 2005; 25:5777-85. [PMID: 15964830 PMCID: PMC1157002 DOI: 10.1128/mcb.25.13.5777-5785.2005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Numerous studies indirectly implicate Rac GTPases in cancer. To investigate if Rac3 contributes to normal or malignant cell function, we generated rac3 null mutants through gene targeting. These mice were viable, fertile, and lacked an obvious external phenotype. This shows Rac3 function is dispensable for embryonic development. Bcr/Abl is a deregulated tyrosine kinase that causes chronic myelogenous leukemia and Ph-positive acute lymphoblastic leukemia in humans. Vav1, a hematopoiesis-specific exchange factor for Rac, was constitutively tyrosine phosphorylated in primary lymphomas from Bcr/Abl P190 transgenic mice, suggesting inappropriate Rac activation. rac3 is expressed in these malignant hematopoietic cells. Using lysates from BCR/ABL transgenic mice that express or lack rac3, we detected the presence of activated Rac3 but not Rac1 or Rac2 in the malignant precursor B-lineage lymphoblasts. In addition, in female P190 BCR/ABL transgenic mice, lack of rac3 was associated with a longer average survival. These data are the first to directly show a stimulatory role for Rac in leukemia in vivo. Moreover, our data suggest that interference with Rac3 activity, for example, by using geranyl-geranyltransferase inhibitors, may provide a positive clinical benefit for patients with Ph-positive acute lymphoblastic leukemia.
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Affiliation(s)
- Young Jin Cho
- Section of Molecular Carcinogenesis, Division of Hematology/Oncology Ms#54, Childrens Hospital Los Angeles, University of Southern California 4650 Sunset Boulevard, Los Angeles, California 90027, USA
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41
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Boureux A, Furstoss O, Simon V, Roche S. Abl tyrosine kinase regulates a Rac/JNK and a Rac/Nox pathway for DNA synthesis and Myc expression induced by growth factors. J Cell Sci 2005; 118:3717-26. [PMID: 16076903 DOI: 10.1242/jcs.02491] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The cytoplasmic tyrosine kinase Abl is a Src substrate required for platelet-derived growth factor (PDGF) receptor signaling leading to Myc expression and DNA synthesis. Abl targets are, however, ill defined. Here we report that the small GTPase Rac is an important effector of its mitogenic function. PDGF-induced Rac activation was impaired in cells with inactive Abl and active Rac overcame the mitogenic defects found in these cells. Rac function required both a Jun N-terminal kinase (JNK) and a NADPH oxidase (Nox) pathway. Furthermore, co-activation of JNK and Nox were sufficient to mimic the Rac mitogenic rescue. Abl also regulated PDGF-induced JNK and Nox activation. Finally, we found that Myc is an important target of this signaling cascade: Myc induction was sensitive to small inhibitors of JNK and Nox activities and forced expression of Myc overcame the G1 block induced by dominant interfering mutants of mitogen-activated protein kinase kinase 4 (MKK4) and Nox2 activating subunit. We concluded that cytoplasmic Abl operates on a Rac/JNK and a Rac/Nox pathway for PDGF-induced Myc induction and DNA synthesis.
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Affiliation(s)
- Anthony Boureux
- CRBM, CNRS FRE2593, 1919 route de Mende, 34293 Montpellier Cedex 05, France
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42
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Inoue T, Heo WD, Grimley JS, Wandless TJ, Meyer T. An inducible translocation strategy to rapidly activate and inhibit small GTPase signaling pathways. Nat Methods 2005; 2:415-8. [PMID: 15908919 PMCID: PMC3579513 DOI: 10.1038/nmeth763] [Citation(s) in RCA: 322] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2005] [Accepted: 04/22/2005] [Indexed: 11/09/2022]
Abstract
We made substantial advances in the implementation of a rapamycin-triggered heterodimerization strategy. Using molecular engineering of different targeting and enzymatic fusion constructs and a new rapamycin analog, Rho GTPases were directly activated or inactivated on a timescale of seconds, which was followed by pronounced cell morphological changes. As signaling processes often occur within minutes, such rapid perturbations provide a powerful tool to investigate the role, selectivity and timing of Rho GTPase-mediated signaling processes.
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Affiliation(s)
- Takanari Inoue
- Stanford University, Department of Molecular Pharmacology, Clark Center, 318 Campus Drive, Stanford, California 94305-5439, USA.
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43
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Carstanjen D, Yamauchi A, Koornneef A, Zang H, Filippi MD, Harris C, Towe J, Atkinson S, Zheng Y, Dinauer MC, Williams DA. Rac2 regulates neutrophil chemotaxis, superoxide production, and myeloid colony formation through multiple distinct effector pathways. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2005; 174:4613-20. [PMID: 15814684 DOI: 10.4049/jimmunol.174.8.4613] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Polymorphonuclear neutrophils (PMN) are an important component of the innate immune system. We have shown previously that migration and superoxide (O2*-) production, as well as some kinase signaling pathways are compromised in mice deficient in the Ras-related Rho GTPase Rac2. In this study, we demonstrate that Rac2 controls chemotaxis and superoxide production via distinct pathways and is critical for development of myeloid colonies in vitro. The Rac2 mutants V36A, F37A, and N39A all bind to both Pak1 and p67(phox), yet are unable to rescue superoxide production and chemotaxis when expressed in Rac2-/- PMN. In contrast, the N43A mutant, which binds to Por1 (Arfaptin 2), p67phox, and Pak1, is able to rescue superoxide production but not chemotaxis. The F37A mutant, demonstrated to have reduced binding to Por1, shows reduced rescue of fMLP-induced chemotaxis. Finally, the Rac2Y40C mutant that is defective in binding to all three potential downstream effectors (Pak1, p67phox, and Por1) is unable to rescue chemotaxis, motility, or superoxide production, but is able to rescue defective growth of myeloid colonies in vitro. These findings suggest that binding to any single effector is not sufficient to rescue the distinct cellular phenotypes of Rac2-/- PMN, implicating multiple, distinct, and potentially parallel effector pathways.
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Affiliation(s)
- Dirk Carstanjen
- Division of Experimental Hematology, Children's Hospital Research Foundation, Cincinnati, OH 45229, USA
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44
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Ng J, Luo L. Rho GTPases regulate axon growth through convergent and divergent signaling pathways. Neuron 2005; 44:779-93. [PMID: 15572110 DOI: 10.1016/j.neuron.2004.11.014] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Revised: 08/20/2004] [Accepted: 10/15/2004] [Indexed: 11/16/2022]
Abstract
Rho GTPases are essential regulators of cytoskeletal reorganization, but how they do so during neuronal morphogenesis in vivo is poorly understood. Here we show that the actin depolymerization factor cofilin is essential for axon growth in Drosophila neurons. Cofilin function in axon growth is inhibited by LIM kinase and activated by Slingshot phosphatase. Dephosphorylating cofilin appears to be the major function of Slingshot in regulating axon growth in vivo. Genetic data provide evidence that Rho or Rac/Cdc42, via effector kinases Rok or Pak, respectively, activate LIM kinase to inhibit axon growth. Importantly, Rac also activates a Pak-independent pathway that promotes axon growth, and different RacGEFs regulate these distinct pathways. These genetic analyses reveal convergent and divergent pathways from Rho GTPases to the cytoskeleton during axon growth in vivo and suggest that different developmental outcomes could be achieved by biases in pathway selection.
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Affiliation(s)
- Julian Ng
- Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
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45
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Bae GU, Kim YK, Kwon HK, Park JW, Lee EK, Paek SJ, Choi WS, Jung ID, Lee HY, Cho EJ, Lee HW, Han JW. Hydrogen peroxide mediates Rac1 activation of S6K1. Exp Cell Res 2004; 300:476-84. [PMID: 15475011 DOI: 10.1016/j.yexcr.2004.07.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2004] [Revised: 07/19/2004] [Indexed: 11/25/2022]
Abstract
We previously reported that hydrogen peroxide (H2O2) mediates mitogen activation of ribosomal protein S6 kinase 1 (S6K1) which plays an important role in cell proliferation and growth. In this study, we investigated a possible role of H2O2 as a molecular linker in Rac1 activation of S6K1. Overexpression of recombinant catalase in NIH-3T3 cells led to the drastic inhibition of H2O2 production by PDGF, which was accompanied by a decrease in S6K1 activity. Similarly, PDGF activation of S6K1 was significantly inhibited by transient transfection or stable transfection of the cells with a dominant-negative Rac1 (Rac1N17), while overexpression of constitutively active Rac1 (Rac1V12) in the cells led to an increase in basal activity of S6K1. In addition, stable transfection of Rat2 cells with Rac1N17 dramatically attenuated the H2O2 production by PDGF as compared with that in the control cells. In contrast, Rat2 cells stably transfected with Rac1V12 produced high level of H2O2 in the absence of PDGF, comparable to that in the control cells stimulated with PDGF. More importantly, elimination of H2O2 produced in Rat2 cells overexpressing Rac1V12 inhibited the Rac1V12 activation of S6K1, indicating the possible role of H2O2 as a mediator in the activation of S6K1 by Rac1. However, H2O2 could be also produced via other pathway, which is independent of Rac1 or PI3K, because in Rat2 cells stably transfected with Rac1N17, H2O2 could be produced by arsenite, which has been shown to be a stimulator of H2O2 production. Taken together, these results suggest that H2O2 plays a pivotal role as a mediator in Rac1 activation of S6K1.
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Affiliation(s)
- Gyu-Un Bae
- College of Pharmacy, Sungkyunkwan University, Suwon 440-746, South Korea
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46
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Hoppe AD, Swanson JA. Cdc42, Rac1, and Rac2 display distinct patterns of activation during phagocytosis. Mol Biol Cell 2004; 15:3509-19. [PMID: 15169870 PMCID: PMC491814 DOI: 10.1091/mbc.e03-11-0847] [Citation(s) in RCA: 273] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2003] [Revised: 05/03/2004] [Accepted: 05/04/2004] [Indexed: 01/09/2023] Open
Abstract
The small G proteins Cdc42, Rac1, and Rac2 regulate the rearrangements of actin and membrane necessary for Fcgamma receptor-mediated phagocytosis by macrophages. Activated, GTP-bound Cdc42, Rac1, and Rac2 bind to the p21-binding domain (PBD) of PAK1, and this interaction provided a basis for microscopic methods to localize activation of these G proteins inside cells. Fluorescence resonance energy transfer-based stoichiometry of fluorescent chimeras of actin, PBD, Cdc42, Rac1, and Rac2 was used to quantify G protein activation relative to actin movements during phagocytosis of IgG-opsonized erythrocytes. The activation dynamics of endogenous G proteins, localized using yellow fluorescent protein-labeled PBD, was restricted to phagocytic cups, with a prominent spike of activation over an actin-poor region at the base of the cup. Refinements of fluorescence resonance energy transfer stoichiometry allowed calculation of the fractions of activated GTPases in forming phagosomes. Cdc42 activation was restricted to the leading margin of the cell, whereas Rac1 was active throughout the phagocytic cup. During phagosome closure, activation of Rac1 and Rac2 increased uniformly and transiently in the actin-poor region of phagosomal membrane. These distinct roles for Cdc42, Rac1, and Rac2 in the component activities of phagocytosis indicate mechanisms by which their differential regulation coordinates rearrangements of actin and membranes.
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Affiliation(s)
- Adam D Hoppe
- Department of Microbiology and Immunology and the Biophysics Research Division, University of Michigan Medical School, Ann Arbor, Michigan 48109-0620, USA
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47
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Menard RE, Mattingly RR. Cell surface receptors activate p21-activated kinase 1 via multiple Ras and PI3-kinase-dependent pathways. Cell Signal 2004; 15:1099-109. [PMID: 14575865 DOI: 10.1016/s0898-6568(03)00087-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
p21-activated kinases (PAKs) were the first identified mammalian members of a growing family of Ste20-like serine-threonine protein kinases. In this study, we show that PAK1 can be stimulated by carbachol, lysophosphatidic acid (LPA), epidermal growth factor (EGF), and phorbol 12-myristate 13-acetate (PMA) by multiple independent and overlapping pathways. Dominant-negative Ras, Rac, and Cdc42 inhibited PAK1 activation by all of these agonists, while active Rac1 and Cdc42 were sufficient to maximally activate PAK1 in the absence of any treatment. Active Ras induced only a weak activation of PAK1 that could be potentiated by muscarinic receptor stimulation. Studies using inhibitors of the EGF receptor tyrosine kinase, phosphatidylinositol 3-kinase (PI3-kinase) and protein kinase C (PKC) revealed that all of the cell surface agonists could activate PAK1 through pathways independent of PKC, that EGF stimulated a PI3-kinase dependent pathway to stimulate PAK1, and that muscarinic receptor stimulation of PAK1 was predominantly mediated through this EGF-R-dependent mechanism. Activation of PAK1 by LPA was independent of PI3-kinase and the EGF receptor, but was inhibited by dominant-negative RhoA. These results identify multiple Ras-dependent pathways to activation of PAK1.
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Affiliation(s)
- Raymond E Menard
- Department of Pharmacology, Wayne State University, 540 E. Canfield, Room 6326, Detroit, MI 48201, USA
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Abstract
In order to generate coherent biological responses to extracellular stimuli, cells have established synergistic and antagonistic crosstalk between pathways with similar or opposing functions, respectively. Two routes cooperating in the generation of mitogenic and cytoskeletal functions are those induced by Ras and Rho/Rac GTPases. In these signaling interactions, Rho/Rac proteins have been always placed in a downstream position respect to Ras in all cell systems analysed so far. In this report, we describe that such signaling hierarchy does not apply to T-lymphocytes. Thus, we show that both Rac1 GDP/GTP exchange factors such as Vav and constitutively active versions of Rac1 can promote the effective stimulation of the Ras pathway in T-lymphocytes. The molecular link for this new type of pathway interconnectivity is RasGRP1, a diacylglycerol-dependent GDP/GTP exchange factor for Ras that translocates to the plasma membrane in a Vav- and Rac1-dependent manner. The effect of the Vav/Rac1 pathway on the Ras pathway is highly dependent on the activity of phospholipase C-gamma, the key cellular supplier of intracellular diacylglycerol. Signaling experiments suggest that this crosstalk represents a signaling strategy used by the T-cell receptor to promote robust biological responses of both the Rac/Rho and Ras pathways upon antigen engagement.
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Affiliation(s)
- José L Zugaza
- Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer, University of Salamanca-CSIC, Campus Unamuno, E-37007 Salamanca, Spain
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Caloca MJ, Zugaza JL, Vicente-Manzanares M, Sánchez-Madrid F, Bustelo XR. F-actin-dependent Translocation of the Rap1 GDP/GTP Exchange Factor RasGRP2. J Biol Chem 2004; 279:20435-46. [PMID: 14988412 DOI: 10.1074/jbc.m313013200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
RasGRPs constitute a new group of diacylglycerol-dependent GDP/GTP exchange factors that activate Ras subfamily GTPases. Despite a common structure, Ras-GRPs diverge in their GTPase specificity, subcellular distribution, and downstream biological effects. The more divergent family member is RasGRP2, a Rap1-specific exchange factor with low affinity toward diacylglycerol. The regulation of RasGRP2 during signal transduction has remained elusive up to now. In this report, we show that the subcellular localization of Ras-GRP2 is highly dependent on actin dynamics. Thus, the induction of F-actin by cytoskeletal regulators such as Vav, Vav2, Dbl, and Rac1 leads to the shift of RasGRP2 from the cytosol to membrane ruffles and its co-localization with F-actin. Treatment of cells with cytoskeletal disrupting drugs abolishes this effect, leading to an abnormal localization of RasGRP2 in cytoplasmic clusters of actin. The use of Rac1 effector mutants indicates that the RasGRP2 translocation is linked exclusively to actin polymerization and is independent of other pathways such as p21-activated kinase JNK, or superoxide production. Biochemical experiments demonstrate that the translocation of RasGRP2 to membrane ruffles is mediated by the direct association of this protein with F-actin, a property contained within its 150 first amino acids. Finally, we show that the RasGRP2/F-actin interaction promotes the regionalized activation of Rap1 in juxtamembrane areas of the cell. These results reveal a novel function of the actin cytoskeleton in mediating the spatial activation of Ras subfamily GTPases through the selective recruitment of GDP/GTP exchange factors.
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Affiliation(s)
- Mariía J Caloca
- Centro de Investigación del Cáncer, University of Salamanca-Consejo Superior de Investigaciones Cientiíficas, Campus Unamuno, E-37007 Salamanca, Spain
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Schotte P, Denecker G, Van Den Broeke A, Vandenabeele P, Cornelis GR, Beyaert R. Targeting Rac1 by the Yersinia effector protein YopE inhibits caspase-1-mediated maturation and release of interleukin-1beta. J Biol Chem 2004; 279:25134-42. [PMID: 15060067 DOI: 10.1074/jbc.m401245200] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Yersinia bacteria can take control of the host cell by injecting so-called Yop effector proteins into the cytosol of the cells to which they adhere. Using Yersinia enterocolitica strains that are deficient for one or more Yops, we could show that YopE and, to a lesser extent, YopT interfere with the caspase-1-mediated maturation of prointerleukin-1beta in macrophages. In addition, overexpression of YopE and YopT was shown to prevent the autoproteolytic activation of caspase-1 in a way that is dependent on their inhibitory effect on Rho GTPases. Expression of constitutive-active or dominant-negative Rho GTPase mutants or treatment with Rho GTPase inhibitors confirmed the role of Rho GTPases and, in particular, Rac1 in the autoactivation of caspase-1. Rac1-induced caspase-1 activation was mediated by its effect on LIM kinase-1, which is targeting the actin cytoskeleton. Rac-1 and LIM kinase-1 dominant-negative mutants were shown to inhibit caspase-1 activation induced by overexpression of Asc, which is a caspase-1-activating adaptor protein. Moreover, Rac1 as well as YopE and YopT significantly modulated caspase-1 oligomerization. These results highlight a previously unknown function of Rho GTPases in the activation of caspase-1 and give new insight on the role of YopE in immune-escape mechanisms of Yersinia.
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Affiliation(s)
- Peter Schotte
- Unit of Molecular Signal Transduction in Inflammation, Flanders Interuniversity Institute for Biotechnology (VIB), Ghent Unniversity, Ghent, Belgium
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