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Jeon Y, Shin YK, Kim H, Choi YY, Kang M, Kwon Y, Cho Y, Chi SW, Shin JE. βPix Guanine Nucleotide Exchange Factor Regulates Regeneration of Injured Peripheral Axons. Int J Mol Sci 2023; 24:14357. [PMID: 37762659 PMCID: PMC10532151 DOI: 10.3390/ijms241814357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 09/13/2023] [Accepted: 09/15/2023] [Indexed: 09/29/2023] Open
Abstract
Axon regeneration is essential for successful recovery after peripheral nerve injury. Although growth cone reformation and axonal extension are crucial steps in axonal regeneration, the regulatory mechanisms underlying these dynamic processes are poorly understood. Here, we identify βPix (Arhgef7), the guanine nucleotide exchange factor for Rac1 GTPase, as a regulator of axonal regeneration. After sciatic nerve injury in mice, the expression levels of βPix increase significantly in nerve segments containing regenerating axons. In regrowing axons, βPix is localized in the peripheral domain of the growth cone. Using βPix neuronal isoform knockout (NIKO) mice in which the neuronal isoforms of βPix are specifically removed, we demonstrate that βPix promotes neurite outgrowth in cultured dorsal root ganglion neurons and in vivo axon regeneration after sciatic nerve crush injury. Activation of cJun and STAT3 in the cell bodies is not affected in βPix NIKO mice, supporting the local action of βPix in regenerating axons. Finally, inhibiting Src, a kinase previously identified as an activator of the βPix neuronal isoform, causes axon outgrowth defects in vitro, like those found in the βPix NIKO neurons. Altogether, these data indicate that βPix plays an important role in axonal regrowth during peripheral nerve regeneration.
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Affiliation(s)
- Yewon Jeon
- Department of Life Sciences, Korea University, Seoul 02841, Republic of Korea;
- Peripheral Neuropathy Research Center (PNRC), Department of Molecular Neuroscience, College of Medicine, Dong-A University, Busan 49201, Republic of Korea; (Y.K.S.); (H.K.); (Y.Y.C.); (M.K.)
| | - Yoon Kyung Shin
- Peripheral Neuropathy Research Center (PNRC), Department of Molecular Neuroscience, College of Medicine, Dong-A University, Busan 49201, Republic of Korea; (Y.K.S.); (H.K.); (Y.Y.C.); (M.K.)
| | - Hwigyeong Kim
- Peripheral Neuropathy Research Center (PNRC), Department of Molecular Neuroscience, College of Medicine, Dong-A University, Busan 49201, Republic of Korea; (Y.K.S.); (H.K.); (Y.Y.C.); (M.K.)
- Department of Translational Biomedical Sciences, Graduate School of Dong-A University, Busan 49201, Republic of Korea
| | - Yun Young Choi
- Peripheral Neuropathy Research Center (PNRC), Department of Molecular Neuroscience, College of Medicine, Dong-A University, Busan 49201, Republic of Korea; (Y.K.S.); (H.K.); (Y.Y.C.); (M.K.)
| | - Minjae Kang
- Peripheral Neuropathy Research Center (PNRC), Department of Molecular Neuroscience, College of Medicine, Dong-A University, Busan 49201, Republic of Korea; (Y.K.S.); (H.K.); (Y.Y.C.); (M.K.)
- Department of Translational Biomedical Sciences, Graduate School of Dong-A University, Busan 49201, Republic of Korea
| | - Younghee Kwon
- Department School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Yongcheol Cho
- Department of Brain Sciences, DGIST, Daegu 42899, Republic of Korea;
| | - Sung Wook Chi
- Department of Life Sciences, Korea University, Seoul 02841, Republic of Korea;
| | - Jung Eun Shin
- Peripheral Neuropathy Research Center (PNRC), Department of Molecular Neuroscience, College of Medicine, Dong-A University, Busan 49201, Republic of Korea; (Y.K.S.); (H.K.); (Y.Y.C.); (M.K.)
- Department of Translational Biomedical Sciences, Graduate School of Dong-A University, Busan 49201, Republic of Korea
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2
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Kwon Y, Jeon YW, Kwon M, Cho Y, Park D, Shin JE. βPix-d promotes tubulin acetylation and neurite outgrowth through a PAK/Stathmin1 signaling pathway. PLoS One 2020; 15:e0230814. [PMID: 32251425 PMCID: PMC7135283 DOI: 10.1371/journal.pone.0230814] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 03/09/2020] [Indexed: 12/11/2022] Open
Abstract
Microtubules are a major cytoskeletal component of neurites, and the regulation of microtubule stability is essential for neurite morphogenesis. βPix (ARHGEF7) is a guanine nucleotide exchange factor for the small GTPases Rac1 and Cdc42, which modulate the organization of actin filaments and microtubules. βPix is expressed as alternatively spliced variants, including the ubiquitous isoform βPix-a and the neuronal isoforms βPix-b and βPix-d, but the function of the neuronal isoforms remains unclear. Here, we reveal the novel role of βPix neuronal isoforms in regulating tubulin acetylation and neurite outgrowth. At DIV4, hippocampal neurons cultured from βPix neuronal isoform knockout (βPix-NIKO) mice exhibit defects in neurite morphology and tubulin acetylation, a type of tubulin modification which often labels stable microtubules. Treating βPix-NIKO neurons with paclitaxel, which stabilizes the microtubules, or reintroducing either neuronal βPix isoform to the KO neurons overcomes the impairment in neurite morphology and tubulin acetylation, suggesting that neuronal βPix isoforms may promote microtubule stabilization during neurite development. βPix-NIKO neurons also exhibit lower phosphorylation levels for Stathmin1, a microtubule-destabilizing protein, at Ser16. Expressing either βPix neuronal isoform in the βPix-NIKO neurons restores Stathmin1 phosphorylation levels, with βPix-d having a greater effect than βPix-b. Furthermore, we find that the recovery of neurite length and Stathmin1 phosphorylation via βPix-d expression requires PAK kinase activity. Taken together, our study demonstrates that βPix-d regulates the phosphorylation of Stathmin1 in a PAK-dependent manner and that neuronal βPix isoforms promote tubulin acetylation and neurite morphogenesis during neuronal development.
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Affiliation(s)
- Younghee Kwon
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Ye Won Jeon
- Division of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Minjae Kwon
- Division of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Yongcheol Cho
- Division of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Dongeun Park
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Jung Eun Shin
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
- Institute of Life Science and Biotechnology, Korea University, Seoul, Republic of Korea
- * E-mail:
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3
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Kwon Y, Lee SJ, Lee E, Kim D, Park D. βPix heterozygous mice have defects in neuronal morphology and social interaction. Biochem Biophys Res Commun 2019; 516:1204-1210. [PMID: 31296385 DOI: 10.1016/j.bbrc.2019.07.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 07/01/2019] [Indexed: 11/20/2022]
Abstract
βPix activates Rho family small GTPases, Rac1 and Cdc42 as a guanine nucleotide exchange factor. Although overexpression of βPix in cultured neurons indicates that βPix is involved in spine morphogenesis and synapse formation in vitro, the in vivo role of βPix in the neuron is not well understood. Recently, we generated βPix knockout mice that showed lethality at embryonic day 9.5. Here, we investigate the neuronal role of βPix using βPix heterozygous mice that are viable and fertile. βPix heterozygous mice show decreased expression levels of βPix proteins in various tissues including the brain. Cultured hippocampal neurons from βPix heterozygous mice show a decrease in neurite length and complexity as well as synaptic density. Both excitatory and inhibitory synapse densities are decreased in these neurons. Golgi-staining of hippocampal tissues from the brain of these mice show reduced dendritic complexity and spine density in the hippocampal neurons. Expression levels of NMDA- and AMPA-receptor subunits and Git1 protein in hippocampal tissues are also decreased in these mice. Behaviorally, βPix heterozygous mice exhibit impaired social interaction. Altogether, these results indicate that βPix is required for neurite morphogenesis and synapse formation, and the reduced expression of βPix proteins results in a defect in social behavior.
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Affiliation(s)
- Younghee Kwon
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Seung Joon Lee
- Computational Biology & Genomics, Biogen, Cambridge, MA, 02142, USA.
| | - Eunee Lee
- Department of Anatomy, College of Medicine, Yonsei University, Seoul, 03722, Republic of Korea.
| | - Daesoo Kim
- Department of Biological Sciences, KAIST, Daejeon, 34141, Republic of Korea.
| | - Dongeun Park
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea.
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Shin MS, Song SH, Shin JE, Lee SH, Huh SO, Park D. Src-mediated phosphorylation of βPix-b regulates dendritic spine morphogenesis. J Cell Sci 2019; 132:jcs.224980. [DOI: 10.1242/jcs.224980] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 12/24/2018] [Indexed: 11/20/2022] Open
Abstract
PAK-interacting guanine nucleotide exchange factor (βPix) has been implicated in many actin-based cellular processes including spine morphogenesis in neurons. However, the molecular mechanisms by which βPix controls spine morphology remain elusive. Previously, we have reported the expression of several alternative spliced βPix isoforms in the brain. Here, we report a novel finding that the b isoform of βPix (βPix-b) mediates regulation of spine and synapse formation. We found that βPix-b, which is mainly expressed in neurons, enhances spine and synapse formation through preferential localization at spines. In neurons, glutamate treatment efficiently stimulates Rac1 GEF activity of βPix-b. The glutamate stimulation also promotes Src kinase-mediated phosphorylation of βPix-b in both AMPA receptor- and NMDA receptor-dependent manner. Tyrosine 598 (Y598) of βPix-b is identified as the major Src-mediated phosphorylation site. Finally, Y598 phosphorylation of βPix-b enhances its Rac1 GEF activity that is critical for spine and synapse formation. In conclusion, we provide a novel mechanism by which βPix-b regulates activity-dependent spinogenesis and synaptogenesis via Src-mediated phosphorylation.
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Affiliation(s)
- Mi-seon Shin
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Sang-ho Song
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
- Current address: Lee Kong Chian School of Medicine, Nanyang Technological University and Institute of Molecular and Cell Biology, Singapore 138673, Singapore
| | - Jung Eun Shin
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
- Current address: KU Advanced Graduate Program for Life Science, Korea University, Seoul 02841, Republic of Korea
| | - Seung-Hye Lee
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
- Current address: Department of Neuroscience, Genentech, Inc., South San Francisco, CA 94080, USA
| | - Sung-Oh Huh
- Department of Pharmacology, College of Medicine, Institute of Natural Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Dongeun Park
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
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López Tobón A, Suresh M, Jin J, Vitriolo A, Pietralla T, Tedford K, Bossenz M, Mahnken K, Kiefer F, Testa G, Fischer KD, Püschel AW. The guanine nucleotide exchange factor Arhgef7/βPix promotes axon formation upstream of TC10. Sci Rep 2018; 8:8811. [PMID: 29891904 PMCID: PMC5995858 DOI: 10.1038/s41598-018-27081-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 05/29/2018] [Indexed: 11/10/2022] Open
Abstract
The characteristic six layers of the mammalian neocortex develop sequentially as neurons are generated by neural progenitors and subsequently migrate past older neurons to their final position in the cortical plate. One of the earliest steps of neuronal differentiation is the formation of an axon. Small GTPases play essential roles during this process by regulating cytoskeletal dynamics and intracellular trafficking. While the function of GTPases has been studied extensively in cultured neurons and in vivo much less is known about their upstream regulators. Here we show that Arhgef7 (also called βPix or Cool1) is essential for axon formation during cortical development. The loss of Arhgef7 results in an extensive loss of axons in cultured neurons and in the developing cortex. Arhgef7 is a guanine-nucleotide exchange factor (GEF) for Cdc42, a GTPase that has a central role in directing the formation of axons during brain development. However, active Cdc42 was not able to rescue the knockdown of Arhgef7. We show that Arhgef7 interacts with the GTPase TC10 that is closely related to Cdc42. Expression of active TC10 can restore the ability to extend axons in Arhgef7-deficient neurons. Our results identify an essential role of Arhgef7 during neuronal development that promotes axon formation upstream of TC10.
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Affiliation(s)
- Alejandro López Tobón
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Schloßplatz 5, D-48149, Münster, Germany.,Cells-in-Motion Cluster of Excellence, University of Münster, D-48149, Münster, Germany.,Department of Oncology and Hemato-Oncology, University of Milan, Milan, 20122, Italy.,European Institute of Oncology, Via Adamello 16, 20139, Milan, Italy
| | - Megalakshmi Suresh
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Schloßplatz 5, D-48149, Münster, Germany.,Cells-in-Motion Cluster of Excellence, University of Münster, D-48149, Münster, Germany
| | - Jing Jin
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Schloßplatz 5, D-48149, Münster, Germany.,Cells-in-Motion Cluster of Excellence, University of Münster, D-48149, Münster, Germany
| | - Alessandro Vitriolo
- Department of Oncology and Hemato-Oncology, University of Milan, Milan, 20122, Italy.,European Institute of Oncology, Via Adamello 16, 20139, Milan, Italy
| | - Thorben Pietralla
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Schloßplatz 5, D-48149, Münster, Germany
| | - Kerry Tedford
- Institut für Biochemie und Zellbiologie, Otto-von-Guericke-University, Medical Faculty, Leipziger Str. 44, 39120, Magdeburg, 39120, Germany
| | - Michael Bossenz
- Institut für Biochemie und Zellbiologie, Otto-von-Guericke-University, Medical Faculty, Leipziger Str. 44, 39120, Magdeburg, 39120, Germany
| | - Kristina Mahnken
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Schloßplatz 5, D-48149, Münster, Germany
| | - Friedemann Kiefer
- Cells-in-Motion Cluster of Excellence, University of Münster, D-48149, Münster, Germany.,Max-Planck-Institute for Molecular Biomedicine, Mammalian cell signaling laboratory, Röntgenstr. 20, D-48149, Münster, Germany.,European Institute for Molecular Imaging, Westfälische Wilhelms-Universität, Waldeyerstr. 15, D-48149, Münster, Germany
| | - Giuseppe Testa
- Department of Oncology and Hemato-Oncology, University of Milan, Milan, 20122, Italy.,European Institute of Oncology, Via Adamello 16, 20139, Milan, Italy
| | - Klaus-Dieter Fischer
- Institut für Biochemie und Zellbiologie, Otto-von-Guericke-University, Medical Faculty, Leipziger Str. 44, 39120, Magdeburg, 39120, Germany
| | - Andreas W Püschel
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Schloßplatz 5, D-48149, Münster, Germany. .,Cells-in-Motion Cluster of Excellence, University of Münster, D-48149, Münster, Germany.
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6
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Zhou W, Li X, Premont RT. Expanding functions of GIT Arf GTPase-activating proteins, PIX Rho guanine nucleotide exchange factors and GIT-PIX complexes. J Cell Sci 2017; 129:1963-74. [PMID: 27182061 DOI: 10.1242/jcs.179465] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The GIT proteins, GIT1 and GIT2, are GTPase-activating proteins (inactivators) for the ADP-ribosylation factor (Arf) small GTP-binding proteins, and function to limit the activity of Arf proteins. The PIX proteins, α-PIX and β-PIX (also known as ARHGEF6 and ARHGEF7, respectively), are guanine nucleotide exchange factors (activators) for the Rho family small GTP-binding protein family members Rac1 and Cdc42. Through their multi-domain structures, GIT and PIX proteins can also function as signaling scaffolds by binding to numerous protein partners. Importantly, the constitutive association of GIT and PIX proteins into oligomeric GIT-PIX complexes allows these two proteins to function together as subunits of a larger structure that coordinates two distinct small GTP-binding protein pathways and serves as multivalent scaffold for the partners of both constituent subunits. Studies have revealed the involvement of GIT and PIX proteins, and of the GIT-PIX complex, in numerous fundamental cellular processes through a wide variety of mechanisms, pathways and signaling partners. In this Commentary, we discuss recent findings in key physiological systems that exemplify current understanding of the function of this important regulatory complex. Further, we draw attention to gaps in crucial information that remain to be filled to allow a better understanding of the many roles of the GIT-PIX complex in health and disease.
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Affiliation(s)
- Wu Zhou
- Department of Medicine, College of Medicine and Health, Lishui University, Lishui 323000, China
| | - Xiaobo Li
- Department of Computer Science and Technology, College of Engineering and Design, Lishui University, Lishui 323000, China
| | - Richard T Premont
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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Llano O, Smirnov S, Soni S, Golubtsov A, Guillemin I, Hotulainen P, Medina I, Nothwang HG, Rivera C, Ludwig A. KCC2 regulates actin dynamics in dendritic spines via interaction with β-PIX. J Cell Biol 2015; 209:671-86. [PMID: 26056138 PMCID: PMC4460141 DOI: 10.1083/jcb.201411008] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 04/27/2015] [Indexed: 02/07/2023] Open
Abstract
Chloride extrusion in mature neurons is largely mediated by the neuron-specific potassium-chloride cotransporter KCC2. In addition, independently of its chloride transport function, KCC2 regulates the development and morphology of dendritic spines through structural interactions with the actin cytoskeleton. The mechanism of this effect remains largely unknown. In this paper, we show a novel pathway for KCC2-mediated regulation of the actin cytoskeleton in neurons. We found that KCC2, through interaction with the b isoform of Rac/Cdc42 guanine nucleotide exchange factor β-PIX, regulates the activity of Rac1 GTPase and the phosphorylation of one of the major actin-regulating proteins, cofilin-1. KCC2-deficient neurons had abnormally high levels of phosphorylated cofilin-1. Consistently, dendritic spines of these neurons exhibited a large pool of stable actin, resulting in reduced spine motility and diminished density of functional synapses. In conclusion, we describe a novel signaling pathway that couples KCC2 to the cytoskeleton and regulates the formation of glutamatergic synapses.
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Affiliation(s)
- Olaya Llano
- Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Sergey Smirnov
- Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Shetal Soni
- Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Andrey Golubtsov
- Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Isabelle Guillemin
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences and Research Center for Neurosensory Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Pirta Hotulainen
- Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
| | - Igor Medina
- Institut de Neurobiologie de la Méditerranée, Institut National de la Santé et de la Recherche Médicale Unité 901, 13009 Marseille, France Aix-Marseille Université, Unité Mixte de Recherche 901, 13273 Marseille, France
| | - Hans Gerd Nothwang
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences and Research Center for Neurosensory Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Claudio Rivera
- Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland Institut de Neurobiologie de la Méditerranée, Institut National de la Santé et de la Recherche Médicale Unité 901, 13009 Marseille, France Aix-Marseille Université, Unité Mixte de Recherche 901, 13273 Marseille, France
| | - Anastasia Ludwig
- Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland
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Omelchenko T, Rabadan MA, Hernández-Martínez R, Grego-Bessa J, Anderson KV, Hall A. β-Pix directs collective migration of anterior visceral endoderm cells in the early mouse embryo. Genes Dev 2015; 28:2764-77. [PMID: 25512563 PMCID: PMC4265679 DOI: 10.1101/gad.251371.114] [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: 11/25/2022]
Abstract
Rac1 is essential for generating the protrusive activity that drives the collective migration of anterior visceral endoderm (AVE) cells in the early mouse embryo. Omelchenko et al. identified β-Pix as a potential regulator of Rac1. Genetic deletion of β-Pix in mice disrupts collective AVE migration. Collective epithelial migration is important throughout embryonic development. The underlying mechanisms are poorly understood but likely involve spatially localized activation of Rho GTPases. We previously reported that Rac1 is essential for generating the protrusive activity that drives the collective migration of anterior visceral endoderm (AVE) cells in the early mouse embryo. To identify potential regulators of Rac1, we first performed an RNAi screen of Rho family exchange factors (guanine nucleotide exchange factor [GEF]) in an in vitro collective epithelial migration assay and identified β-Pix. Genetic deletion of β-Pix in mice disrupts collective AVE migration, while high-resolution live imaging revealed that this is associated with randomly directed protrusive activity. We conclude that β-Pix controls the spatial localization of Rac1 activity to drive collective AVE migration at a critical stage in mouse development.
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Affiliation(s)
| | | | - Rocío Hernández-Martínez
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Joaquim Grego-Bessa
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Kathryn V Anderson
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
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9
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Noble M, Mayer-Pröschel M, Li Z, Dong T, Cui W, Pröschel C, Ambeskovic I, Dietrich J, Han R, Yang YM, Folts C, Stripay J, Chen HY, Stevens BM. Redox biology in normal cells and cancer: restoring function of the redox/Fyn/c-Cbl pathway in cancer cells offers new approaches to cancer treatment. Free Radic Biol Med 2015; 79:300-23. [PMID: 25481740 PMCID: PMC10173888 DOI: 10.1016/j.freeradbiomed.2014.10.860] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 10/29/2014] [Accepted: 10/30/2014] [Indexed: 12/12/2022]
Abstract
This review discusses a unique discovery path starting with novel findings on redox regulation of precursor cell and signaling pathway function and identification of a new mechanism by which relatively small changes in redox status can control entire signaling networks that regulate self-renewal, differentiation, and survival. The pathway central to this work, the redox/Fyn/c-Cbl (RFC) pathway, converts small increases in oxidative status to pan-activation of the c-Cbl ubiquitin ligase, which controls multiple receptors and other proteins of central importance in precursor cell and cancer cell function. Integration of work on the RFC pathway with attempts to understand how treatment with systemic chemotherapy causes neurological problems led to the discovery that glioblastomas (GBMs) and basal-like breast cancers (BLBCs) inhibit c-Cbl function through altered utilization of the cytoskeletal regulators Cool-1/βpix and Cdc42, respectively. Inhibition of these proteins to restore normal c-Cbl function suppresses cancer cell division, increases sensitivity to chemotherapy, disrupts tumor-initiating cell (TIC) activity in GBMs and BLBCs, controls multiple critical TIC regulators, and also allows targeting of non-TICs. Moreover, these manipulations do not increase chemosensitivity or suppress division of nontransformed cells. Restoration of normal c-Cbl function also allows more effective harnessing of estrogen receptor-α (ERα)-independent activities of tamoxifen to activate the RFC pathway and target ERα-negative cancer cells. Our work thus provides a discovery strategy that reveals mechanisms and therapeutic targets that cannot be deduced by standard genetics analyses, which fail to reveal the metabolic information, isoform shifts, protein activation, protein complexes, and protein degradation critical to our discoveries.
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Affiliation(s)
- Mark Noble
- Department of Biomedical Genetics and University of Rochester Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Margot Mayer-Pröschel
- Department of Biomedical Genetics and University of Rochester Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Zaibo Li
- Department of Pathology, Ohio State University Wexner Medical Center, 410W 10th Avenue, E403 Doan Hall, Columbus, OH 43210-1240, USA.
| | - Tiefei Dong
- University of Michigan Tech Transfer, 1600 Huron Pkwy, 2nd Floor, Building 520, Ann Arbor, MI 48109-2590, USA.
| | - Wanchang Cui
- Department of Radiation Oncology, University of Maryland School of Medicine,10 South Pine Street, MSTF Room 600, Baltimore, MD 21201, USA.
| | - Christoph Pröschel
- Department of Biomedical Genetics and University of Rochester Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Ibro Ambeskovic
- Department of Biomedical Genetics and University of Rochester Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Joerg Dietrich
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Yawkey 9E, Boston, MA 02114, USA.
| | - Ruolan Han
- Department of Biomedical Genetics and University of Rochester Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Yin Miranda Yang
- Department of Biomedical Genetics and University of Rochester Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Christopher Folts
- Department of Biomedical Genetics and University of Rochester Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Jennifer Stripay
- Department of Biomedical Genetics and University of Rochester Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY 14642, USA.
| | - Hsing-Yu Chen
- Harvard Medical School, Department of Cell Biology 240 Longwood Avenue Building C1, Room 513B Boston, MA 02115, USA.
| | - Brett M Stevens
- University of Colorado School of Medicine, Division of Hematology, 12700 E. 19th Avenue, Campus Box F754-AMCA, Aurora, CO 80045, USA.
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10
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Totaro A, Tavano S, Filosa G, Gärtner A, Pennucci R, Santambrogio P, Bachi A, Dotti CG, de Curtis I. Biochemical and functional characterisation of αPIX, a specific regulator of axonal and dendritic branching in hippocampal neurons. Biol Cell 2012; 104:533-52. [DOI: 10.1111/boc.201100060] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 04/24/2012] [Indexed: 01/13/2023]
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11
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Saneyoshi T, Hayashi Y. The Ca2+ and Rho GTPase signaling pathways underlying activity-dependent actin remodeling at dendritic spines. Cytoskeleton (Hoboken) 2012; 69:545-54. [PMID: 22566410 DOI: 10.1002/cm.21037] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 04/17/2012] [Accepted: 04/25/2012] [Indexed: 02/06/2023]
Abstract
Most excitatory synapses reside on small protrusions located on the dendritic shaft of neurons called dendritic spines. Neuronal activity regulates the number and structure of spines in both developing and mature brains. Such morphological changes are mediated by the modification of the actin cytoskeleton, the major structural component of spines. Because the number and size of spines is tightly correlated with the strength of synaptic transmission, the activity-dependent structural remodeling of a spine plays an important role in the modulation of synaptic transmission. The regulation of spine morphogenesis utilizes multiple intracellular signaling pathways that alter the dynamics of actin remodeling. Here, we will review recent studies examining the signaling pathways underlying activity-dependent actin remodeling at excitatory postsynaptic neurons.
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12
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Mo J, Lee D, Hong S, Han S, Yeo H, Sun W, Choi S, Kim H, Lee HW. Preso regulation of dendritic outgrowth through PI(4,5)P2-dependent PDZ interaction with βPix. Eur J Neurosci 2012; 36:1960-70. [PMID: 22595022 DOI: 10.1111/j.1460-9568.2012.08124.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In neuronal development, dendritic outgrowth and arborization are important for the establishment of neural circuit formation. A previous study reported that PSD-95-interacting regulator of spine morphogenesis (Preso) formed a complex with PAK-interacting exchange factor-beta (βPix) via PSD-95/Dlg/ZO-1 (PDZ) interaction. Here, we report that Preso and its binding protein, βPix, are localized in dendritic growth cones. Knockdown and dominant-negative inhibition of Preso in cultured neurons markedly reduced the dendritic outgrowth but not branching, and led to a decrease in the intensity of βPix and F-actin in neuronal dendritic tips. Moreover, phosphatidylinositol 4,5-bisphosphate (PIP(2) ) induced a conformational change in Preso toward the open PDZ domain and enhanced the interaction with βPix. In addition, the Preso band 4.1 protein, ezrin, radixin and moesin (FERM) domain mutant is unable to interact with PIP(2) and it did not rescue the Preso-knockdown effect. These results indicate that PIP(2) is a key signalling molecule that regulates dendritic outgrowth through activation of small GTPase signalling via interaction between Preso and βPix.
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Affiliation(s)
- Jiwon Mo
- Department of Anatomy and Division of Brain Korea 21 Biomedical Science, College of Medicine, Korea University, Seoul, Republic of Korea
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13
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Park J, Kim Y, Park ZY, Park D, Chang S. Neuronal specific βPix-b stimulates actin-dependent processes via the interaction between its PRD and WH1 domain of N-WASP. J Cell Physiol 2012; 227:1476-84. [PMID: 21618538 DOI: 10.1002/jcp.22863] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
βPix, a Pak-interacting nucleotide exchange factor (Cool-1/p85SPR), is a Cdc42/Rac1-specific guanine nucleotide exchange factor (GEF) involved in various actin-related processes. Many previous studies have focused on ubiquitously expressed βPix-a, while the role of the neuronal-specific isoform βPix-b is still unknown, especially whether its role is distinct from or similar to βPix-a. Here we show that unlike βPix-a, overexpression of βPix-b stimulates actin-dependent comet formation in BHK21 cells. This effect is attributed to the interaction between its proline-rich domain (PRD) and the WH1 domain of N-WASP. In addition, we show that overexpression of βPix-b stimulates actin-dependent dendritic spine formation in rat hippocampal neurons in culture, a formation that is blocked by co-expression of the WH1 domain of N-WASP or the PRD of βPix-b. Knocking-down endogenous expression of βPix-b by shRNA reduced the number of dendritic spines, which were rescued only by PRD-containing βPix-b mutants. GEF activity of βPix-b is also required for these effects. The results show that neuronal-specific βPix-b stimulates actin-dependent processes in cells via the interaction between its PRD and the WH1 domain of N-WASP. Our results identify N-WASP as the first protein shown to interact with the PRD of βPix-b, raising the possibility that, as an N-WASP WH1-binding protein, βPix-b may regulate N-WASP's activity in cells.
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Affiliation(s)
- Joohyun Park
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, Seoul, South Korea
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14
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Tolias KF, Duman JG, Um K. Control of synapse development and plasticity by Rho GTPase regulatory proteins. Prog Neurobiol 2011; 94:133-48. [PMID: 21530608 DOI: 10.1016/j.pneurobio.2011.04.011] [Citation(s) in RCA: 197] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 04/13/2011] [Accepted: 04/15/2011] [Indexed: 12/21/2022]
Abstract
Synapses are specialized cell-cell contacts that mediate communication between neurons. Most excitatory synapses in the brain are housed on dendritic spines, small actin-rich protrusions extending from dendrites. During development and in response to environmental stimuli, spines undergo marked changes in shape and number thought to underlie processes like learning and memory. Improper spine development, in contrast, likely impedes information processing in the brain, since spine abnormalities are associated with numerous brain disorders. Elucidating the mechanisms that regulate the formation and plasticity of spines and their resident synapses is therefore crucial to our understanding of cognition and disease. Rho-family GTPases, key regulators of the actin cytoskeleton, play essential roles in orchestrating the development and remodeling of spines and synapses. Precise spatio-temporal regulation of Rho GTPase activity is critical for their function, since aberrant Rho GTPase signaling can cause spine and synapse defects as well as cognitive impairments. Rho GTPases are activated by guanine nucleotide exchange factors (GEFs) and inhibited by GTPase-activating proteins (GAPs). We propose that Rho-family GEFs and GAPs provide the spatiotemporal regulation and signaling specificity necessary for proper Rho GTPase function based on the following features they possess: (i) existence of multiple GEFs and GAPs per Rho GTPase, (ii) developmentally regulated expression, (iii) discrete localization, (iv) ability to bind to and organize specific signaling networks, and (v) tightly regulated activity, perhaps involving GEF/GAP interactions. Recent studies describe several Rho-family GEFs and GAPs that uniquely contribute to spinogenesis and synaptogenesis. Here, we highlight several of these proteins and discuss how they occupy distinct biochemical niches critical for synaptic development.
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Affiliation(s)
- Kimberley F Tolias
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
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15
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Interaction of microtubules and actin with the N-terminus of βPix-b(L) directs cellular pinocytosis. Mol Cell Biochem 2011; 351:207-15. [PMID: 21249427 DOI: 10.1007/s11010-011-0728-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 01/10/2011] [Indexed: 12/30/2022]
Abstract
βPix is a Rac/Cdc42 guanine nucleotide exchange factor (GEF) that is known to be a regulator of actin cytoskeleton remodeling. Recently, a novel splicing isoform, βPix-b(L), was identified as an alternative translational product of the βPix-b mRNA with an extended N-terminus comprising a partial calponin homology (CH) domain and a serine-rich (SR) domain. However, the cellular function of βPix-b(L) is largely unknown. In the current study, we analyzed the genomic DNA structure and cellular functions of βPix-b(L). The results of this study demonstrate that βPix is composed of 24 exons and 21 introns spanning around 100 kb. RT-PCR experiments revealed that there are two forms of βPix mRNA with distinct 5' UTRs that are the result of alternative splicing of exon 1 and 2 from βPix genomic DNA. In addition, affinity chromatography analysis and a pull-down assay with the N-terminal region of βPix-b(L) revealed that βPix-b(L) interacts with tubulin and actin via its N-terminal CH and SR domains, respectively. Interaction with tubulin enabled βPix-b(L) to bundle the microtubule and form membrane protrusions. Furthermore, the N-terminus of βPix-b(L) was also critical for its localization to cellular vesicles. Functionally, βPix-b(L) induced pinocytosis through cooperative action of the CH and Dbl homology (DH) domains, demonstrating the role of βPix-b(L) in the regulation of membrane dynamics.
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16
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Xie Z, Cahill ME, Radulovic J, Wang J, Campbell SL, Miller CA, Sweatt JD, Penzes P. Hippocampal phenotypes in kalirin-deficient mice. Mol Cell Neurosci 2010; 46:45-54. [PMID: 20708080 DOI: 10.1016/j.mcn.2010.08.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Revised: 07/31/2010] [Accepted: 08/03/2010] [Indexed: 11/19/2022] Open
Abstract
Regulation of forebrain cellular structure and function by small GTPase pathways is crucial for normal and pathological brain development and function. Kalirin is a brain-specific activator of Rho-like small GTPases implicated in neuropsychiatric disorders. We have recently demonstrated key roles for kalirin in cortical synaptic transmission, dendrite branching, spine density, and working memory. However, little is known about the impact of the complete absence of kalirin on the hippocampus in mice. We thus investigated hippocampal function, structure, and associated behavioral phenotypes in KALRN knockout (KO) mice we have recently generated. Here we show that KALRN KO mice had modest impairments in hippocampal LTP, but normal hippocampal synaptic transmission. In these mice, both context and cue-dependent fear conditioning were impaired. Spine density and dendrite morphology in hippocampal pyramidal neurons were not significantly affected in the KALRN KO mice, but small alterations in the gross morphology of the hippocampus were detected. These data suggest that hippocampal structure and function are more resilient to the complete loss of kalirin, and reveal impairments in fear learning. These studies allow the comparison of the phenotypes of different kalirin mutant mice and shed light on the brain region-specific functions of small GTPase signaling.
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Affiliation(s)
- Zhong Xie
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
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17
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Shin EY, Lee CS, Park MH, Kim DJ, Kwak SJ, Kim EG. Involvement of betaPIX in angiotensin II-induced migration of vascular smooth muscle cells. Exp Mol Med 2009; 41:387-96. [PMID: 19322025 DOI: 10.3858/emm.2009.41.6.044] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Angiotensin II (Ang II) stimulates migration of vascular smooth muscle cell (VSMC) in addition to its contribution to contraction and hypertrophy. It is well established that Rho GTPases regulate cellular contractility and migration by reorganizing the actin cytoskeleton. Ang II activates Rac1 GTPase, but its upstream guanine nucleotide exchange factor (GEF) remains elusive. Here, we show that Ang II-induced VSMC migration occurs in a betaPIX GEF-dependent manner. betaPIX-specific siRNA treatment significantly inhibited Ang II-induced VSMC migration. Ang II activated the catalytic activity of betaPIX towards Rac1 in dose- and time-dependent manners. Activity reached a peak at 10 min and declined close to a basal level by 30 min following stimulation. Pharmacological inhibition with specific kinase inhibitors revealed the participation of protein kinase C, Src family kinase, and phosphatidylinositol 3-kinase (PI3-K) upstream of betaPIX. Both p21-activated kinase and reactive oxygen species played key roles in cytoskeletal reorganization downstream of betaPIX-Rac1. Taken together, our results suggest that betaPIX is involved in Ang II-induced VSMC migration.
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Affiliation(s)
- Eun Young Shin
- Department of Biochemistry and Signaling Disorder Research CenterCollege of Medicine, Chungbuk National University, Cheongju 361-763, Korea
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18
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Penzes P, Cahill ME, Jones KA, Srivastava DP. Convergent CaMK and RacGEF signals control dendritic structure and function. Trends Cell Biol 2008; 18:405-13. [PMID: 18701290 DOI: 10.1016/j.tcb.2008.07.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 06/30/2008] [Accepted: 07/02/2008] [Indexed: 12/25/2022]
Abstract
Structural plasticity of excitatory synapses is a vital component of neuronal development, synaptic plasticity and behavior, and its malfunction underlies many neurodevelopmental and psychiatric disorders. However, the molecular mechanisms that control dendritic spine morphogenesis have only recently emerged. We summarize recent work that has revealed an important connection between calcium/calmodulin-dependent kinases (CaMKs) and guanine-nucleotide-exchange factors (GEFs) that activate the small GTPase Rac (RacGEFs) in controlling dendritic spine morphogenesis. These two groups of molecules function in neurons as a unique signaling cassette that transduces calcium influx into small GTPase activity and, thence, actin reorganization and spine morphogenesis. Through this pathway, CaMKs and RacGEFs amplify calcium signals and translate them into spatially and temporally regulated structural remodeling of dendritic spines.
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Affiliation(s)
- Peter Penzes
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611, USA.
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19
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Mayhew MW, Jeffery ED, Sherman NE, Nelson K, Polefrone JM, Pratt SJ, Shabanowitz J, Parsons JT, Fox JW, Hunt DF, Horwitz AF. Identification of phosphorylation sites in betaPIX and PAK1. J Cell Sci 2008; 120:3911-8. [PMID: 17989089 DOI: 10.1242/jcs.008177] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Mark W Mayhew
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
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20
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Liu J, Fraser SD, Faloon PW, Rollins EL, Vom Berg J, Starovic-Subota O, Laliberte AL, Chen JN, Serluca FC, Childs SJ. A betaPix Pak2a signaling pathway regulates cerebral vascular stability in zebrafish. Proc Natl Acad Sci U S A 2007; 104:13990-5. [PMID: 17573532 PMCID: PMC1955796 DOI: 10.1073/pnas.0700825104] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2007] [Indexed: 11/18/2022] Open
Abstract
The vasculature tailors to the needs of different tissues and organs. Molecular, structural, and functional specializations are observed in different vascular beds, but few genetic models give insight into how these differences arise. We identify a unique cerebrovascular mutation in the zebrafish affecting the integrity of blood vessels supplying the brain. The zebrafish bubblehead (bbh) mutant exhibits hydrocephalus and severe cranial hemorrhage during early embryogenesis, whereas blood vessels in other regions of the embryo appear intact. Here we show that hemorrhages are associated with poor cerebral endothelial-mesenchymal contacts and an immature vascular pattern in the head. Positional cloning of bbh reveals a hypomorphic mutation in betaPix, a binding partner for the p21-activated kinase (Pak) and a guanine nucleotide exchange factor for Rac and Cdc42. betaPix is broadly expressed during embryonic development and is enriched in the brain and in large blood vessels. By knockdown of specific betaPix splice variants, we show that they play unique roles in embryonic vascular stabilization or hydrocephalus. Finally, we show that Pak2a signaling is downstream of betaPix. These data identify an essential in vivo role for betaPix and Pak2a during embryonic development and illuminate a previously unrecognized pathway specifically involved in cerebrovascular stabilization.
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Affiliation(s)
- Jing Liu
- *Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1
| | - Sherri D. Fraser
- *Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1
| | - Patrick W. Faloon
- Novartis Institutes for BioMedical Research, 250 Massachusetts Avenue, Cambridge, MA 02139
| | - Evvi Lynn Rollins
- *Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1
| | - Johannes Vom Berg
- *Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1
| | - Olivera Starovic-Subota
- *Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1
| | - Angie L. Laliberte
- *Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1
| | - Jau-Nian Chen
- Department of Molecular, Cellular, and Developmental Biology, University of California, Los Angeles, CA 90095; and
| | - Fabrizio C. Serluca
- Novartis Institutes for BioMedical Research, 250 Massachusetts Avenue, Cambridge, MA 02139
| | - Sarah J. Childs
- *Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1
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21
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Abstract
Alpha and betaPIX belong to the group of guanine nucleotide exchange factors (GEFs) that mediate activation of members of the Rho GTPase family, in particular Rac1 and Cdc42, by stimulating the exchange of GDP for GTP. Rho family proteins are well known as regulators of the actin cytoskeleton and have been implicated in the formation of various types of focal adhesion structures. However, the function of GEF proteins during focal adhesion formation is only beginning to emerge. Here, we highlight the recent findings on alpha and betaPIX and their involvement in integrin-dependent signaling and suggest models for the role of PIX proteins during focal adhesion turnover.
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Affiliation(s)
- Georg Rosenberger
- Institut für Humangenetik, Universitätsklinikum Hamburg-Eppendorf, Butenfeld 42, 22529 Hamburg, Germany
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22
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Zeniou-Meyer M, Borg JP, Vitale N. Le complexe GIT-PIX : Une plate-forme de régulation des GTPases ARF et Rac/Cdc42. Med Sci (Paris) 2005; 21:849-53. [PMID: 16197902 DOI: 10.1051/medsci/20052110849] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We recently described that the tumor suppressor factor Scribble anchors the PIX exchange factor for Rac/Cdc42 and the ARF-GAP GIT proteins at the plasma membrane. Because it has been postulated that the GIT-PIX proteins dimerize and tightly self-assemble to form a high molecular weight complex, this nexus may be capable of linking together important signalling molecules to control cytosqueleton polymerization and membrane dynamics. To date, most studies that have tempted to unravel the function of these proteins have found their implication in a great variety of cellular functions (receptor recycling, endo-exocytosis, cell migration, synapse formation...) but have mostly neglected to consider the multimeric organization of this hub. There is no doubt that our comprehension of physiopathological disorders such as cancers will be improved when the nature of the complex pathways integrated by the GIT-PIX nodule will be understood.
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Affiliation(s)
- Maria Zeniou-Meyer
- CNRS UPR-2356, Neurotransmission et sécrétion neuroendocrine, Centre de neurochimie, Strasbourg, France
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23
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Lee J, Jung ID, Chang WK, Park CG, Cho DY, Shin EY, Seo DW, Kim YK, Lee HW, Han JW, Lee HY. p85 beta-PIX is required for cell motility through phosphorylations of focal adhesion kinase and p38 MAP kinase. Exp Cell Res 2005; 307:315-28. [PMID: 15893751 DOI: 10.1016/j.yexcr.2005.03.028] [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] [Received: 07/13/2004] [Revised: 02/22/2005] [Accepted: 03/01/2005] [Indexed: 11/25/2022]
Abstract
Lysophosphatidic acid (LPA) mediates diverse biological responses, including cell migration, through the activation of G-protein-coupled receptors. Recently, we have shown that LPA stimulates p21-activated kinase (PAK) that is critical for focal adhesion kinase (FAK) phosphorylation and cell motility. Here, we provide the direct evidence that p85 beta-PIX is required for cell motility of NIH-3T3 cells by LPA through FAK and p38 MAP kinase phosphorylations. LPA induced p85 beta-PIX binding to FAK in NIH-3T3 cells that was inhibited by pretreatment of the cells with phosphoinositide 3-kinase inhibitor, LY294002. Furthermore, the similar inhibition of the complex formation was also observed, when the cells were transfected with either p85 beta-PIX mutant that cannot bind GIT or dominant negative mutants of Rac1 (N17Rac1) and PAK (PAK-PID). Transfection of the cells with specific p85 beta-PIX siRNA led to drastic inhibition of LPA-induced FAK phosphorylation, peripheral redistribution of p85 beta-PIX with FAK and GIT1, and cell motility. p85 beta-PIX was also required for p38 MAP kinase phosphorylation induced by LPA. Finally, dominant negative mutant of Rho (N19Rho)-transfected cells did not affect PAK activation, while the cells stably transfected with p85 beta-PIX siRNA or N17Rac1 showed the reduction of LPA-induced PAK activation. Taken together, the present data suggest that p85 beta-PIX, located downstream of Rac1, is a key regulator for the activations of FAK or p38 MAP kinase and plays a pivotal role in focal complex formation and cell motility induced by LPA.
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Affiliation(s)
- Jangsoon Lee
- Department of Pharmacology, College of Medicine, Konyang University, Nonsan, 320-711, Republic of Korea
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24
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Rhee S, Yang SJ, Lee SJ, Park D. betaPix-b(L), a novel isoform of betaPix, is generated by alternative translation. Biochem Biophys Res Commun 2004; 318:415-21. [PMID: 15120616 DOI: 10.1016/j.bbrc.2004.04.039] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2004] [Indexed: 11/26/2022]
Abstract
betaPix (Pak-interacting exchange factor) isoforms are recently identified guanine nucleotide exchange factors (GEFs) for Rho family GTPases, Rac/Cdc42, that are key players in the regulation of actin dynamics. Here we show that a novel 105-kDa betaPix isoform, betaPix-bL, is generated by alternative translation of betaPix-b mRNA. Translation of betaPix-bL starts at an atypical initiation site, GTG, that is located 57 nucleotides downstream from the newly identified 5' end of betaPix-b cDNA. The expression of two isoforms, betaPix-b and betaPix-bL, from betaPix-b mRNA is controlled by an internal ribosome entry site (IRES)-driven mechanism. Comparing to betaPix-b, betaPix-bL contains additional 105 amino acids composed of a calponin homology (CH) domain and a serine-rich sequence in the N-terminus. The expression of betaPix-bL in rat brain is developmentally regulated and high in the embryonic stages, suggesting that the function of betaPix-bL is more heavily required during the early stages of brain development.
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Affiliation(s)
- Sangmyung Rhee
- School of Biological Sciences, Seoul National University, Seoul 151-742, South Korea
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25
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Yoshizawa M, Sone M, Matsuo N, Nagase T, Ohara O, Nabeshima YI, Hoshino M. Dynamic and coordinated expression profile of dbl-family guanine nucleotide exchange factors in the developing mouse brain. Gene Expr Patterns 2003; 3:375-81. [PMID: 12799088 DOI: 10.1016/s1567-133x(03)00002-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dbl-family guanine nucleotide exchange factors (Dbl-GEFs) act as activators of Rho-like small G proteins such as Rac1, Cdc42 and RhoA. Recently, some GEFs have been suggested to play important roles in the development of the nervous system. Here, we report a comprehensive expression profile analysis of 20 Dbl-GEFs that have yet to be well investigated. Northern analyses of murine mRNAs from brains of E13, E17, P7 and adult mice revealed expression of 18 out of 20 GEFs in some or all stages. In addition, we found that three human GEFs were highly expressed in the brain. Examination of the spatial expression patterns of five GEFs in embryos or neonatal brain by in situ hybridization revealed distinct patterns for each GEF. Our study reveals the dynamic and coordinated expression profiles of the Dbl-GEFs and provides a basic framework for understanding the function of GEFs in neural development.
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Affiliation(s)
- Masato Yoshizawa
- Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, 606-8501 Kyoto, Japan
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26
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Buchsbaum RJ, Connolly BA, Feig LA. Regulation of p70 S6 kinase by complex formation between the Rac guanine nucleotide exchange factor (Rac-GEF) Tiam1 and the scaffold spinophilin. J Biol Chem 2003; 278:18833-41. [PMID: 12531897 DOI: 10.1074/jbc.m207876200] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Tiam1 is a ubiquitous guanine nucleotide exchange factor (GEF) that activates the Rac GTPase. We have shown previously that the N terminus of Tiam1 contributes to the signaling specificity of its downstream target Rac via association with IB2, a scaffold that promotes Rac activation of a p38 kinase cascade. Here we show that the N terminus of Tiam1 can influence Rac signaling specificity in a different way by interaction with spinophilin, a scaffold that binds to p70 S6 kinase, another protein regulated by Rac. In particular, spinophilin binding promotes the plasma membrane localization of Tiam1 and enhances the ability of Tiam1 to activate p70 S6 kinase. In contrast, spinophilin binding suppresses the ability of Tiam to activate Pak1, a different Rac effector. Finally, a mutant spinophilin that cannot bind to Tiam1 suppresses serum-induced p70 S6 kinase activation in cells, suggesting that a Tiam1/spinophilin complex contributes to p70 S6 kinase regulation by extracellular signals. These findings add to a growing body of evidence supporting the concept that some Rac-GEFs not only activate Rac GTPases but also participate in the selection of Rac effector by binding to particular scaffolds that complex with components of specific Rac effector pathways.
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Affiliation(s)
- Rachel J Buchsbaum
- Department of Biochemistry, Tufts University School of Medicine, Boston, Massachussetts 02111, USA
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27
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Park E, Na M, Choi J, Kim S, Lee JR, Yoon J, Park D, Sheng M, Kim E. The Shank family of postsynaptic density proteins interacts with and promotes synaptic accumulation of the beta PIX guanine nucleotide exchange factor for Rac1 and Cdc42. J Biol Chem 2003; 278:19220-9. [PMID: 12626503 DOI: 10.1074/jbc.m301052200] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Shank/ProSAP family of multidomain proteins is known to play an important role in organizing synaptic multiprotein complexes. Here we report a novel interaction between Shank and beta PIX, a guanine nucleotide exchange factor for the Rac1 and Cdc42 small GTPases. This interaction is mediated by the PDZ domain of Shank and the C-terminal leucine zipper domain and the PDZ domain-binding motif at the extreme C terminus of beta PIX. Shank colocalizes with beta PIX at excitatory synaptic sites in cultured neurons. In brain, Shank forms a complex with beta PIX and beta PIX-associated signaling molecules including p21-associated kinase (PAK), an effector kinase of Rac1/Cdc42. Importantly, overexpression of Shank in cultured neurons promotes synaptic accumulation of beta PIX and PAK. Considering the involvement of Rac1 and PAK in spine dynamics, these results suggest that Shank recruits beta PIX and PAK to spines for the regulation of postsynaptic structure.
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Affiliation(s)
- Eunhye Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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Ahn SJ, Chung KW, Lee RA, Park IA, Lee SH, Park DE, Noh DY. Overexpression of betaPix-a in human breast cancer tissues. Cancer Lett 2003; 193:99-107. [PMID: 12691829 DOI: 10.1016/s0304-3835(03)00004-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Pak interacting exchange factor (betaPix) is a recently cloned protein that contains a multidomain with many potential binding sites and is known to be involved in the regulation of Cdc42/Rac GTPases and Pak kinase activity. These domains of betaPix appear to play a critical role in the regulation of the cytoskeletal organization. The overexpression of betaPix enhances the activation of p38, which is thought to be an important downstream effector of the Rho GTPase family (Rac, Cdc42), which are involved in increased membrane ruffling and cell motility. This increase of cell mobility is an important feature of cancer invasion. We examined the expression of betaPix-a in human breast cancer tissues and adjacent normal tissues obtained from 39 breast cancer patients. Immunoblot analysis and RT-PCR revealed that betaPix-a expression was significantly increased in 37 of the 39 breast cancer tissues (94.9%) versus normal breast tissues. Immunohistochemical analysis showed that breast cancer tissues have consistently stronger immunoreactivity to betaPix-a antibodies than normal tissues. betaPix-a overexpression was inversely associated with extensive intraductal component (P<0.001). In conclusion, betaPix-a expression was found to be higher in human breast cancer tissues than in normal breast tissues, which implies a role for betaPix-a in human breast tumorigenesis. We suggest that betaPix-a may be a useful marker of malignant disease in the breast.
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Affiliation(s)
- Soo-Jung Ahn
- Cancer Research Institute, Seoul National University, 28 Yongon-Dong, Jongno-Gu, Seoul 110-744, South Korea
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Kim S, Ko J, Shin H, Lee JR, Lim C, Han JH, Altrock WD, Garner CC, Gundelfinger ED, Premont RT, Kaang BK, Kim E. The GIT family of proteins forms multimers and associates with the presynaptic cytomatrix protein Piccolo. J Biol Chem 2003; 278:6291-300. [PMID: 12473661 DOI: 10.1074/jbc.m212287200] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cytoskeletal matrix assembled at active zones (CAZ) is implicated in defining neurotransmitter release sites. However, little is known about the molecular mechanisms by which the CAZ is organized. Here we report a novel interaction between Piccolo, a core component of the CAZ, and GIT proteins, multidomain signaling integrators with GTPase-activating protein activity for ADP-ribosylation factor small GTPases. A small region (approximately 150 amino acid residues) in Piccolo, which is not conserved in the closely related CAZ protein Bassoon, mediates a direct interaction with the Spa2 homology domain (SHD) domain of GIT1. Piccolo and GIT1 colocalize at synaptic sites in cultured neurons. In brain, Piccolo forms a complex with GIT1 and various GIT-associated proteins, including betaPIX, focal adhesion kinase, liprin-alpha, and paxillin. Point mutations in the SHD of GIT1 differentially interfere with the association of GIT1 with Piccolo, betaPIX, and focal adhesion kinase, suggesting that these proteins bind to the SHD by different mechanisms. Intriguingly, GIT proteins form homo- and heteromultimers through their C-terminal G-protein-coupled receptor kinase-binding domain in a tail-to-tail fashion. This multimerization enables GIT1 to simultaneously interact with multiple SHD-binding proteins including Piccolo and betaPIX. These results suggest that, through their multimerization and interaction with Piccolo, the GIT family proteins are involved in the organization of the CAZ.
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Affiliation(s)
- Seho Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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30
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Shin EY, Shin KS, Lee CS, Woo KN, Quan SH, Soung NK, Kim YG, Cha CI, Kim SR, Park D, Bokoch GM, Kim EG. Phosphorylation of p85 beta PIX, a Rac/Cdc42-specific guanine nucleotide exchange factor, via the Ras/ERK/PAK2 pathway is required for basic fibroblast growth factor-induced neurite outgrowth. J Biol Chem 2002; 277:44417-30. [PMID: 12226077 DOI: 10.1074/jbc.m203754200] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Guanine nucleotide exchange factors (GEFs) have been implicated in growth factor-induced neuronal differentiation through the activation of small GTPases. Although phosphorylation of these GEFs is considered an activation mechanism, little is known about the upstream of PAK-interacting exchange factor (PIX), a member of the Dbl family of GEFs. We report here that phosphorylation of p85 betaPIX/Cool/p85SPR is mediated via the Ras/ERK/PAK2 pathway. To understand the role of p85 betaPIX in basic fibroblast growth factor (bFGF)-induced neurite outgrowth, we established PC12 cell lines that overexpress the fibroblast growth factor receptor-1 in a tetracycline-inducible manner. Treatment with bFGF induces the phosphorylation of p85 betaPIX, as determined by metabolic labeling and mobility shift upon gel electrophoresis. Interestingly, phosphorylation of p85 betaPIX is inhibited by PD98059, a specific MEK inhibitor, suggesting the involvement of the ERK cascade. PAK2, a major PAK isoform in PC12 cells as well as a binding partner of p85 betaPIX, also functions upstream of p85 betaPIX phosphorylation. Surprisingly, PAK2 directly binds to ERK, and its activation is dependent on ERK. p85 betaPIX specifically localizes to the lamellipodia at neuronal growth cones in response to bFGF. A mutant form of p85 betaPIX (S525A/T526A), in which the major phosphorylation sites are replaced by alanine, shows significant defect in targeting. Moreover, expression of the mutant p85 betaPIX efficiently blocks PC12 cell neurite outgrowth. Our study defines a novel signaling pathway for bFGF-induced neurite outgrowth that involves activation of the PAK2-p85 betaPIX complex via the ERK cascade and subsequent translocation of this complex.
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Affiliation(s)
- Eun-Young Shin
- Department of Biochemistry, College of Medicine, Chungbuk National University, Cheongju 361-763, Korea
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31
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Abstract
Neurones are highly specialised cells that can extend over great distances, enabling the complex networking of the nervous system. We are beginning to understand in detail the molecular mechanisms that control the shape of neurones during development. One family of proteins that are clearly essential are the Rho GTPases which have a pivotal role in regulating the actin cytoskeleton in all cell types. The Rho GTPases are responsible for the activation and downregulation of many downstream kinases. This review discusses individual kinases that are regulated by three members of the Rho GTPases, Rac, Rho and Cdc42 and their function during neurite outgrowth and remodelling.
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Affiliation(s)
- Margareta Nikolic
- Molecular and Developmental Neurobiology MRC Centre, New Hunt's House, King's College London, London SE1 1UL, UK.
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Koh CG, Manser E, Zhao ZS, Ng CP, Lim L. β1PIX, the PAK-interacting exchange factor, requires localization via a coiled-coil region to promote microvillus-like structures and membrane ruffles. J Cell Sci 2001; 114:4239-51. [PMID: 11739656 DOI: 10.1242/jcs.114.23.4239] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PIX is a Rho-family guanine nucleotide exchange factor that binds PAK. We previously described two isoforms of PIX that differ in their N termini. Here, we report the identification of a new splice variant of βPIX, designated β2PIX, that is the dominant species in brain and that lacks the region of ∼120 residues with predicted coiled-coil structure at the C terminus of β1PIX. Instead, β2PIX contains a serine-rich C terminus. To determine whether these splice variants differ in their cellular function, we studied the effect of expressing these proteins in HeLa cells. We found that the coiled-coil region plays a key role in the localization of β1PIX to the cell periphery and is also responsible for PIX dimerization. Overexpression of β1, but not β2PIX, drives formation of membrane ruffles and microvillus-like structures (via activation of Rac1 and Cdc42, respectively), indicating that its function requires localized activation of these GTPases. Thus, β1PIX, like other RhoGEFs, exerts specific morphological functions that are dependent on its intracellular location and are mediated by its C-terminal dimerization domain.
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Affiliation(s)
- C G Koh
- Glaxo-IMCB Group, Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609.
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Lee SH, Eom M, Lee SJ, Kim S, Park HJ, Park D. BetaPix-enhanced p38 activation by Cdc42/Rac/PAK/MKK3/6-mediated pathway. Implication in the regulation of membrane ruffling. J Biol Chem 2001; 276:25066-72. [PMID: 11309380 DOI: 10.1074/jbc.m010892200] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
betaPix (PAK-interacting exchange factor) is a recently identified guanine nucleotide exchange factor for Rho family small G protein Cdc42/Rac. The protein interacts with p21-activated protein kinase (PAK) through its SH3 domain. We examined the effect of betaPix on MAP kinase signaling and cytoskeletal rearrangement in NIH3T3 fibroblast cells. Overexpression of betaPix enhanced the activation of p38 in the absence of other stimuli and also induced translocation of p38 to the nucleus. This betaPix-induced p38 activation was blocked by coexpression of dominant-negative Cdc42/Rac or kinase-inactive PAK, indicating that the effect of betaPix on p38 is exerted through the Cdc42/Rac-PAK pathway and requires PAK kinase activity. The essential role of betaPix in growth factor-stimulated p38 activation was evidenced by the blocking of platelet-derived growth factor-induced p38 activation in the cells expressing betaPix SH3m (W43K) and betaPix DHm (L238R,L239R). In addition, SB203580, a p38 inhibitor, and kinase-inactive p38 (T180A,Y182F) blocked membrane ruffling induced by betaPix, suggesting that p38 might be involved in mediating betaPix-induced membrane ruffling. The results in this study suggest that betaPix might have a role in nuclear signaling, as well as in actin cytoskeleton regulation, and that some part of these cellular functions is possibly mediated by p38 MAP kinase.
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Affiliation(s)
- S H Lee
- School of Biological Sciences, Seoul National University, Seoul, 151-742, Republic of Korea
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Kim S, Lee SH, Park D. Leucine zipper-mediated homodimerization of the p21-activated kinase-interacting factor, beta Pix. Implication for a role in cytoskeletal reorganization. J Biol Chem 2001; 276:10581-4. [PMID: 11278242 DOI: 10.1074/jbc.c000806200] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pix, a p21-activated kinase-interacting exchange factor, is known to be involved in the regulation of Cdc42/Rac GTPases. The 85-kDa betaPix-a protein contains an Src homology 3 domain, the tandem Dbl homology and Pleckstrin homology domains, a proline-rich region, and a GIT1-binding domain. In addition to those domains, betaPix-a also contains a putative leucine zipper domain at the C-terminal end. In this study, we demonstrate that the previously identified putative leucine zipper domain mediates the formation of betaPix-a homodimers. Using in vitro and in vivo methodologies, we show that deletion of the leucine zipper domain is sufficient to abolish betaPix-a homodimerization. In NIH3T3 fibroblast cells, expression of wild type betaPix-a induces the formation of membrane ruffles. However, cells expressing the leucine zipper domain deletion mutant could not form membrane ruffle structures. Moreover, platelet-derived growth factor-mediated cytoskeletal changes were completely blocked by the leucine zipper domain deletion mutant. The results suggest that the leucine zipper domain enables betaPix-a to homodimerize, and homodimerization is essential for betaPix-a signaling functions leading to the cytoskeletal reorganization.
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Affiliation(s)
- S Kim
- School of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea.
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