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Sun Q, Zhou L, Yu Z, Zhang J, Zhang C, Pi H. Human Parathyroid Hormone (1-34) accelerates skin wound healing through inducing cell migration via up-regulating the expression of Rac1. Cell Div 2024; 19:4. [PMID: 38347626 PMCID: PMC10860314 DOI: 10.1186/s13008-024-00111-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 02/09/2024] [Indexed: 02/15/2024] Open
Abstract
Delayed wound healing is a public issue that imposes a significant burden on both society and the patients themselves. To date, although numerous methods have been developed to accelerate the speed of wound closure, the therapeutic effects are partially limited due to the complex procedures, high costs, potential side effects, and ethical concerns. While some studies have reported that the in-vivo application of Human Parathyroid Hormone (1-34) (hPTH(1-34)) promotes the wound-healing process, the definitive role and underlying mechanisms through which it regulates the behavior of fibroblasts and keratinocytes remains unclear. Herein, hPTH(1-34)'s role in cell migration is evaluated with a series of in-vitro and in-vivo studies, whereby hPTH(1-34)'s underlying mechanism in activating the two types of cells was detected. The in-vitro study revealed that hPTH(1-34) enhanced the migration of both fibroblasts and HaCaT cells. Ras-associated C3 botulinum toxin subunit 1 (Rac1), a classical member of the Rho family, was upregulated in hPTH(1-34)-treated fibroblasts and HaCaT cells. Further study by silencing the expression of Rac1 with siRNA reversed the hPTH(1-34)-enhanced cell migration, thus confirming that Rac1 was involved in hPTH(1-34)-induced cell behavior. In-vivo study on rat wound models confirmed the effects of hPTH(1-34) on fibroblasts and keratinocytes, with increased collagen deposition, fibroblasts accumulation, and Rac1 expression in the hPTH(1-34)-treated wounds. In summary, the present study demonstrated that hPTH(1-34) accelerated wound healing through enhancing the migration of cells through the up-regulation of Rac1 expression.
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Affiliation(s)
- Qingpeng Sun
- Department of Orthopaedic, Xiangyang Hospital of Traditional Chinese Medicine, No. 24, Changzheng Road, Fancheng District, Xiangyang, 441000, Hubei Province, China
| | - Liya Zhou
- Department of Orthopaedic, Xiangyang Hospital of Traditional Chinese Medicine, No. 24, Changzheng Road, Fancheng District, Xiangyang, 441000, Hubei Province, China
| | - Zhiyong Yu
- Department of Orthopaedic, Xiangyang Hospital of Traditional Chinese Medicine, No. 24, Changzheng Road, Fancheng District, Xiangyang, 441000, Hubei Province, China
| | - Jun Zhang
- Department of Orthopaedic, Xiangyang Hospital of Traditional Chinese Medicine, No. 24, Changzheng Road, Fancheng District, Xiangyang, 441000, Hubei Province, China
| | - Chao Zhang
- Department of Orthopaedic, Xiangyang Hospital of Traditional Chinese Medicine, No. 24, Changzheng Road, Fancheng District, Xiangyang, 441000, Hubei Province, China
| | - Honglin Pi
- Department of Orthopaedic, Xiangyang Hospital of Traditional Chinese Medicine, No. 24, Changzheng Road, Fancheng District, Xiangyang, 441000, Hubei Province, China.
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Wang Y, Wu X, Wang Q, Zheng M, Pang L. Annexin A2 functions downstream of c‑Jun N‑terminal kinase to promote skin fibroblast cell migration. Mol Med Rep 2017; 15:4207-4216. [PMID: 28487977 DOI: 10.3892/mmr.2017.6535] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 02/01/2017] [Indexed: 11/06/2022] Open
Abstract
Delayed healing of skin wounds is one of the outcomes of diabetes mellitus (DM), a condition that affects a significant number of patients worldwide. However, the underlying mechanisms remain unknown. In order to examine proteome alterations in DM, a rat model of type 1 diabetes was developed using streptozotocin injections. The proteomic responses of normal and DM rat skin were analyzed by two‑dimensional electrophoresis, and differentially expressed proteins were identified using a liquid chromatography/mass spectrometry system. DM induced 36 and repressed 41 differentially expressed proteins, respectively. Altered proteins were involved in a number of biological processes, including RNA and protein metabolism, the tricarboxylic acid cycle, glycolysis, cytoskeleton regulation, hydrogen detoxification and calcium‑mediated signal transduction. In addition, overexpression of annexin A2, one of the signaling proteins altered by DM, accelerated the rate of human skin fibroblast cell migration. Application of SP600125, an inhibitor of a key regulator of cell migration c‑Jun N‑terminal kinase (JNK), inhibited the migration of normal cells. By contrast, SP600125 treatment did not inhibit the migration of annexin A2‑overexpressed cells, indicating that annexin A2 may function downstream of JNK. In conclusion, the results of the present study reveal the potential proteomic responses to DM in skin tissues, and demonstrate a positive functional role of annexin A2 in fibroblast cell migration.
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Affiliation(s)
- Youpei Wang
- Clinical Examination Center, The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Xinmei Wu
- The Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Qing Wang
- Function Experiment Teaching Center of Wenzhou Medical University, Wenzhou, Zhejiang 325035, P.R. China
| | - Meiqin Zheng
- Clinical Examination Center, The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Lingxia Pang
- Function Experiment Teaching Center of Wenzhou Medical University, Wenzhou, Zhejiang 325035, P.R. China
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3
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ZHANG SISEN, WU LIHUA. Roles of neural precursor cell expressed, developmentally downregulated 9 in tumor-associated cellular processes (Review). Mol Med Rep 2015; 12:6415-21. [DOI: 10.3892/mmr.2015.4240] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 06/15/2015] [Indexed: 11/05/2022] Open
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Bakos J, Bacova Z, Grant SG, Castejon AM, Ostatnikova D. Are Molecules Involved in Neuritogenesis and Axon Guidance Related to Autism Pathogenesis? Neuromolecular Med 2015; 17:297-304. [PMID: 25989848 DOI: 10.1007/s12017-015-8357-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 05/08/2015] [Indexed: 12/27/2022]
Abstract
Autism spectrum disorder is a heterogeneous disease, and numerous alterations of gene expression come into play to attempt to explain potential molecular and pathophysiological causes. Abnormalities of brain development and connectivity associated with alterations in cytoskeletal rearrangement, neuritogenesis and elongation of axons and dendrites might represent or contribute to the structural basis of autism pathology. Slit/Robo signaling regulates cytoskeletal remodeling related to axonal and dendritic branching. Components of its signaling pathway (ABL and Cdc42) are suspected to be molecular bases of alterations of normal development. The present review describes the most important mechanisms underlying neuritogenesis, axon pathfinding and the role of GTPases in neurite outgrowth, with special emphasis on alterations associated with autism spectrum disorders. On the basis of analysis of publicly available microarray data, potential biomarkers of autism are discussed.
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Affiliation(s)
- Jan Bakos
- Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlarska 3, Bratislava, Slovakia,
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5
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Hanniford D, Segura MF, Zhong J, Philips E, Jirau-Serrano X, Darvishian F, Berman RS, Shapiro RL, Pavlick AC, Brown B, Osman I, Hernando E. Identification of metastasis-suppressive microRNAs in primary melanoma. J Natl Cancer Inst 2015; 107:dju494. [PMID: 25677173 DOI: 10.1093/jnci/dju494] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Surgical management of primary melanoma is curative for most patients with clinically localized disease at diagnosis; however, a substantial number of patients recur and progress to advanced disease. Understanding molecular alterations that influence differential tumor progression of histopathologically similar lesions may lead to improved prognosis and therapies to slow or prevent metastasis. METHODS We examined microRNA dysregulation by expression profiling of primary melanoma tumors from 92 patients. We screened candidate microRNAs selected by differential expression between recurrent and nonrecurrent tumors or associated with primary tumor thickness (Student's t test, Benjamini-Hochberg False Discovery Rate [FDR] < 0.05), in in vitro invasion assays. We performed in vivo metastasis assays, matrix remodeling experiments, and molecular studies to identify metastasis-regulating microRNAs and their cellular and molecular mechanisms. All statistical tests were two-sided. RESULTS We identified two microRNAs (hsa-miR-382, hsa-miR-516b) whose expression was lower in aggressive vs nonaggressive primary tumors, which suppressed invasion in vitro and metastasis in vivo (mean metastatic foci: control: 37.9, 95% confidence interval [CI] = 25.6 to 50.2; miR-382: 19.5, 95% CI = 12.2 to 26.9, P = .009; miR-516b: 12.5, 95% CI = 7.7 to 17.4, P < .001, Student's t test). Mechanistically, miR-382 overexpression inhibits extracellular matrix degradation by melanoma cells. Moreover, we identified actin regulators CTTN, RAC1, and ARPC2 as direct targets of miR-382. Depletion of CTTN partially recapitulates miR-382 effects on matrix remodeling, invasion, and metastasis. Inhibition of miR-382 in a weakly tumorigenic melanoma cell line increased tumor progression and metastasis in vivo. CONCLUSIONS Aberrant expression of specific microRNAs that can functionally impact progression of primary melanoma occurs as an early event of melanomagenesis.
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Affiliation(s)
- Doug Hanniford
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Miguel F Segura
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Judy Zhong
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Elliot Philips
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Xavier Jirau-Serrano
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Farbod Darvishian
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Russell S Berman
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Richard L Shapiro
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Anna C Pavlick
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Brian Brown
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Iman Osman
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB)
| | - Eva Hernando
- Department of Pathology (DH, MFS, EP, XJS, FD, EH), Interdisciplinary Melanoma Cooperative Group (DH, MFS, JZ, XJS, FD, RSB, RLS, AP, IO, EH), Department of Environmental Medicine (JZ), Department of Dermatology (AP, IO), Department of Medicine (AP, IO), Department of Urology (IO); Department of Surgery (RSB, RLS), NYU Langone Medical Center, New York, NY; Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (BB).
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6
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High-glucose inhibits human fibroblast cell migration in wound healing via repression of bFGF-regulating JNK phosphorylation. PLoS One 2014; 9:e108182. [PMID: 25244316 PMCID: PMC4171528 DOI: 10.1371/journal.pone.0108182] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 08/26/2014] [Indexed: 01/03/2023] Open
Abstract
One of the major symptoms of diabetes mellitus (DM) is delayed wound healing, which affects large populations of patients worldwide. However, the underlying mechanism behind this illness remains elusive. Skin wound healing requires a series of coordinated processes, including fibroblast cell proliferation and migration. Here, we simulate DM by application of high glucose (HG) in human foreskin primary fibroblast cells to analyze the molecular mechanism of DM effects on wound healing. The results indicate that HG, at a concentration of 30 mM, delay cell migration, but not cell proliferation. bFGF is known to promote cell migration that partially rescues HG effects on cell migration. Molecular and cell biology studies demonstrated that HG enhanced ROS production and repressed JNK phosphorylation, but did not affect Rac1 activity. JNK and Rac1 activation were known to be important for bFGF regulated cell migration. To further confirm DM effects on skin repair, a type 1 diabetic rat model was established, and we observed the efficacy of bFGF on both normal and diabetic rat skin repair. Furthermore, proteomic studies identified an increase of Annexin A2 protein nitration in HG-stressed fibroblasts and the nitration was protected by activation of bFGF signaling. Treatment with FGFR1 and JNK inhibitors delayed cell migration and increased Annexin A2 nitration levels, indicating that Annexin A2 nitration is modulated by bFGF signaling via activation of JNK. Together with these results, our data suggests that the HG-mediated delay of cell migration is linked to the inhibition of bFGF signaling, specifically through JNK suppression.
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7
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Van den Broeke C, Jacob T, Favoreel HW. Rho'ing in and out of cells: viral interactions with Rho GTPase signaling. Small GTPases 2014; 5:e28318. [PMID: 24691164 DOI: 10.4161/sgtp.28318] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Rho GTPases are key regulators of actin and microtubule dynamics and organization. Increasing evidence shows that many viruses have evolved diverse interactions with Rho GTPase signaling and manipulate them for their own benefit. In this review, we discuss how Rho GTPase signaling interferes with many steps in the viral replication cycle, especially entry, replication, and spread. Seen the diversity between viruses, it is not surprising that there is considerable variability in viral interactions with Rho GTPase signaling. However, several largely common effects on Rho GTPases and actin architecture and microtubule dynamics have been reported. For some of these processes, the molecular signaling and biological consequences are well documented while for others we just begin to understand them. A better knowledge and identification of common threads in the different viral interactions with Rho GTPase signaling and their ultimate consequences for virus and host may pave the way toward the development of new antiviral drugs that may target different viruses.
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Affiliation(s)
- Céline Van den Broeke
- Department of Virology, Parasitology, and Immunology; Faculty of Veterinary Medicine; Ghent University; Ghent, Belgium
| | - Thary Jacob
- Department of Virology, Parasitology, and Immunology; Faculty of Veterinary Medicine; Ghent University; Ghent, Belgium
| | - Herman W Favoreel
- Department of Virology, Parasitology, and Immunology; Faculty of Veterinary Medicine; Ghent University; Ghent, Belgium
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8
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Auer M, Hausott B, Klimaschewski L. Rho GTPases as regulators of morphological neuroplasticity. Ann Anat 2011; 193:259-66. [PMID: 21459565 PMCID: PMC3143277 DOI: 10.1016/j.aanat.2011.02.015] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2011] [Accepted: 02/28/2011] [Indexed: 11/17/2022]
Abstract
GTPases function as intracellular, bimolecular switches by adopting different conformational states in response to binding GDP or GTP. Their activation is mediated through cell-surface receptors. Rho GTPases act on several downstream effectors involved in cellular morphogenesis, cell polarity, migration and cell division. In neurons, Rho GTPases regulate various features of dendritic and axonal outgrowth during development and regeneration mainly through their effects on the cytoskeleton. This review summarizes the main functions of Rho, Rac and Cdc42 GTPases as key regulators of morphological neuroplasticity under normal and pathological conditions.
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Affiliation(s)
- Maria Auer
- Division of Neuroanatomy, Medical University of Innsbruck, Muellerstrasse 59, Innsbruck, Austria
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9
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Kanazawa S, Fujiwara T, Matsuzaki S, Shingaki K, Taniguchi M, Miyata S, Tohyama M, Sakai Y, Yano K, Hosokawa K, Kubo T. bFGF regulates PI3-kinase-Rac1-JNK pathway and promotes fibroblast migration in wound healing. PLoS One 2010; 5:e12228. [PMID: 20808927 PMCID: PMC2923192 DOI: 10.1371/journal.pone.0012228] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 07/25/2010] [Indexed: 01/06/2023] Open
Abstract
Fibroblast proliferation and migration play important roles in wound healing. bFGF is known to promote both fibroblast proliferation and migration during the process of wound healing. However, the signal transduction of bFGF-induced fibroblast migration is still unclear, because bFGF can affect both proliferation and migration. Herein, we investigated the effect of bFGF on fibroblast migration regardless of its effect on fibroblast proliferation. We noticed involvement of the small GTPases of the Rho family, PI3-kinase, and JNK. bFGF activated RhoA, Rac1, PI3-kinase, and JNK in cultured fibroblasts. Inhibition of RhoA did not block bFGF-induced fibroblast migration, whereas inhibition of Rac1, PI3-kinase, or JNK blocked the fibroblast migration significantly. PI3-kinase-inhibited cells down-regulated the activities of Rac1 and JNK, and Rac1-inhibited cells down-regulated JNK activity, suggesting that PI3-kinase is upstream of Rac1 and that JNK is downstream of Rac1. Thus, we concluded that PI3-kinase, Rac1, and JNK were essential for bFGF-induced fibroblast migration, which is a novel pathway of bFGF-induced cell migration.
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Affiliation(s)
- Shigeyuki Kanazawa
- Department of Plastic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Toshihiro Fujiwara
- Department of Plastic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Shinsuke Matsuzaki
- Department of Anatomy and Neuroscience, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kenta Shingaki
- Department of Anatomy and Neuroscience, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Manabu Taniguchi
- Department of Anatomy and Neuroscience, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Shingo Miyata
- Department of Anatomy and Neuroscience, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Masaya Tohyama
- Department of Anatomy and Neuroscience, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yasuo Sakai
- Department of Plastic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kenji Yano
- Department of Plastic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Ko Hosokawa
- Department of Plastic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Tateki Kubo
- Department of Plastic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
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10
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Eriksson T, Varshney G, Aspenström P, Palmer RH. Characterisation of the role of Vrp1 in cell fusion during the development of visceral muscle of Drosophila melanogaster. BMC DEVELOPMENTAL BIOLOGY 2010; 10:86. [PMID: 20701765 PMCID: PMC2931478 DOI: 10.1186/1471-213x-10-86] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 08/11/2010] [Indexed: 12/03/2022]
Abstract
Background In Drosophila muscle cell fusion takes place both during the formation of the somatic mesoderm and the visceral mesoderm, giving rise to the skeletal muscles and the gut musculature respectively. The core process of myoblast fusion is believed to be similar for both organs. The actin cytoskeleton regulator Verprolin acts by binding to WASP, which in turn binds to the Arp2/3 complex and thus activates actin polymerization. While Verprolin has been shown to be important for somatic muscle cell fusion, the function of this protein in visceral muscle fusion has not been determined. Results Verprolin is specifically expressed in the fusion competent myoblasts of the visceral mesoderm, suggesting a role in visceral mesoderm fusion. We here describe a novel Verprolin mutant allele which displays subtle visceral mesoderm fusion defects in the form of mislocalization of the immunoglobulin superfamily molecule Duf/Kirre, which is required on the myoblast cell surface to facilitate attachment between cells that are about to fuse, indicating a function for Verprolin in visceral mesoderm fusion. We further show that Verprolin mutant cells are capable of both migrating and fusing and that the WASP-binding domain of Verprolin is required for rescue of the Verprolin mutant phenotype. Conclusions Verprolin is expressed in the visceral mesoderm and plays a role in visceral muscle fusion as shown by mislocalization of Duf/Kirre in the Verprolin mutant, however it is not absolutely required for myoblast fusion in either the visceral or the somatic mesoderm.
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Affiliation(s)
- Therese Eriksson
- Department of Molecular Biology, Building 6L, Umeå University, Umeå S-90187, Sweden
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11
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Beta C. Bistability in the actin cortex. PMC BIOPHYSICS 2010; 3:12. [PMID: 20576094 PMCID: PMC2907310 DOI: 10.1186/1757-5036-3-12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 06/24/2010] [Indexed: 11/19/2022]
Abstract
Multi-color fluorescence imaging experiments of wave forming Dictyostelium cells have revealed that actin waves separate two domains of the cell cortex that differ in their actin structure and phosphoinositide composition. We propose a bistable model of actin dynamics to account for these experimental observation. The model is based on the simplifying assumption that the actin cytoskeleton is composed of two distinct network types, a dendritic and a bundled network. The two structurally different states that were observed in experiments correspond to the stable fixed points in the bistable regime of this model. Each fixed point is dominated by one of the two network types. The experimentally observed actin waves can be considered as trigger waves that propagate transitions between the two stable fixed points. PACS Codes: 87.16.Ln, 87.17.Aa, 89.75.Fb
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Affiliation(s)
- Carsten Beta
- Institut für Physik und Astronomie, Universität Potsdam, 14476 Potsdam, Germany.
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12
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Hausott B, Kurnaz I, Gajovic S, Klimaschewski L. Signaling by neuronal tyrosine kinase receptors: relevance for development and regeneration. Anat Rec (Hoboken) 2010; 292:1976-85. [PMID: 19943349 DOI: 10.1002/ar.20964] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Receptor tyrosine kinase activation by binding of neurotrophic factors determines neuronal morphology and identity, migration of neurons to appropriate destinations, and integration into functional neural circuits as well as synapse formation with appropriate targets at the right time and at the right place. This review summarizes the most important aspects of intraneuronal signaling mechanisms and induced gene expression changes that underlie morphological and neurochemical consequences of receptor tyrosine kinase activation in central and peripheral neurons.
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Affiliation(s)
- Barbara Hausott
- Division of Neuroanatomy, Medical University Innsbruck, Muellerstrasse 59, Innsbruck, Austria
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Gehmlich K, Hayess K, Legler C, Haebel S, Van der Ven PFM, Ehler E, Fürst DO. Ponsin interacts with Nck adapter proteins: implications for a role in cytoskeletal remodelling during differentiation of skeletal muscle cells. Eur J Cell Biol 2010; 89:351-64. [PMID: 20129698 DOI: 10.1016/j.ejcb.2009.10.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2009] [Revised: 10/26/2009] [Accepted: 10/29/2009] [Indexed: 10/19/2022] Open
Abstract
Skeletal muscle differentiation is a complex process: It is characterised by changes in gene expression and protein composition. Simultaneously, a dramatic remodelling of the cytoskeleton and associated cell-matrix contacts, the costameres, occurs. The expression and localisation of the protein ponsin at cell-matrix contacts marks the establishment of costameres. In this report we show that skeletal muscle cells are characterised by a novel ponsin isoform, which contains a large insertion in its carboxy-terminus. This skeletal muscle-specific module binds the adapter proteins Nck1 and Nck2, and increased co-localisation of ponsin with Nck2 is observed at remodelling cell-matrix contacts of differentiating skeletal muscle cells. Since this ponsin insertion can be phosphorylated, it may adjust the interaction affinity with Nck adapter proteins. The novel ponsin isoform and its interaction with Nck1/2 provide exciting insight into the convergence of signalling pathways at the costameres, and its crucial role for skeletal muscle differentiation and re-generation.
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Affiliation(s)
- Katja Gehmlich
- Institute of Biochemistry and Biology, Cell Biology, University of Potsdam, Germany.
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14
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Meacham CE, Ho EE, Dubrovsky E, Gertler FB, Hemann MT. In vivo RNAi screening identifies regulators of actin dynamics as key determinants of lymphoma progression. Nat Genet 2009; 41:1133-7. [PMID: 19783987 PMCID: PMC2756700 DOI: 10.1038/ng.451] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Accepted: 07/27/2009] [Indexed: 01/08/2023]
Abstract
Mouse models have markedly improved our understanding of cancer development and tumor biology. However, these models have shown limited efficacy as tractable systems for unbiased genetic experimentation. Here, we report the adaptation of loss-of-function screening to mouse models of cancer. Specifically, we have been able to introduce a library of shRNAs into individual mice using transplantable Emu-myc lymphoma cells. This approach has allowed us to screen nearly 1,000 genetic alterations in the context of a single tumor-bearing mouse. These experiments have identified a central role for regulators of actin dynamics and cell motility in lymphoma cell homeostasis in vivo. Validation experiments confirmed that these proteins represent bona fide lymphoma drug targets. Additionally, suppression of two of these targets, Rac2 and twinfilin, potentiated the action of the front-line chemotherapeutic vincristine, suggesting a critical relationship between cell motility and tumor relapse in hematopoietic malignancies.
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Affiliation(s)
- Corbin E Meacham
- The Koch Institute for Integrative Cancer Research at MIT, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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15
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Nowak SJ, Nahirney PC, Hadjantonakis AK, Baylies MK. Nap1-mediated actin remodeling is essential for mammalian myoblast fusion. J Cell Sci 2009; 122:3282-93. [PMID: 19706686 DOI: 10.1242/jcs.047597] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Myoblast fusion is crucial for the formation, growth, maintenance and regeneration of healthy skeletal muscle. Unfortunately, the molecular machinery, cell behaviors, and membrane and cytoskeletal remodeling events that govern fusion and myofiber formation remain poorly understood. Using time-lapse imaging approaches on mouse C2C12 myoblasts, we identify discrete and specific molecular events at myoblast membranes during fusion and myotube formation. These events include rearrangement of cell shape from fibroblast to spindle-like morphologies, changes in lamellipodial and filopodial extensions during different periods of differentiation, and changes in membrane alignment and organization during fusion. We find that actin-cytoskeleton remodeling is crucial for these events: pharmacological inhibition of F-actin polymerization leads to decreased lamellipodial and filopodial extensions and to reduced myoblast fusion. Additionally, shRNA-mediated inhibition of Nap1, a member of the WAVE actin-remodeling complex, results in accumulations of F-actin structures at the plasma membrane that are concomitant with a decrease in myoblast fusion. Our data highlight distinct and essential roles for actin cytoskeleton remodeling during mammalian myoblast fusion, provide a platform for cellular and molecular dissection of the fusion process, and suggest a functional conservation of Nap1-regulated actin-cytoskeleton remodeling during myoblast fusion between mammals and Drosophila.
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Affiliation(s)
- Scott J Nowak
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, USA
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16
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Feltri ML, Suter U, Relvas JB. The function of RhoGTPases in axon ensheathment and myelination. Glia 2009; 56:1508-1517. [PMID: 18803320 DOI: 10.1002/glia.20752] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
RhoGTPases are molecular switches that integrate extracellular signals to perform diverse cellular responses. This ability relies on the network of proteins regulating RhoGTPases activity and localization, and on the interaction of RhoGTPases with many different cellular effectors. Myelination is an ideal place for RhoGTPases regulation, as it is the result of fine orchestration of many stimuli from at least two cell types. Recent work has revealed that RhoGTPases are required for Schwann cells to sort, ensheath, and myelinate axons. Here, we will review these recent advances showing the critical roles for RhoGTPases in various aspects of Schwann development and myelination, including the recent discovery of their involvement in Charcot-Marie-Tooth disease. Comparison with potential roles of RhoGTPases in central nervous system myelination will be drawn.
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Affiliation(s)
- M Laura Feltri
- DIBIT, San Raffaele Scientific Institute, Milano, Italy.
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17
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Krause S, Stendel C, Senderek J, Relvas JB, Suter U. Small Rho GTPases are key regulators of peripheral nerve biology in health and disease. J Peripher Nerv Syst 2009; 13:188-99. [PMID: 18844785 DOI: 10.1111/j.1529-8027.2008.00177.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A thorough knowledge of the cellular and molecular basis of the structure and function of peripheral nerves is of paramount importance not only for a better understanding of the fascinating biology of the peripheral nervous system but also for providing critical insights into the various diseases affecting peripheral nerves as the firm foundation of potential treatments. Genetic approaches in model organisms, in combination with research on hereditary forms of neuropathies, have contributed significantly to our progress in this field. In this review, we will focus on recent advances using these synergistic approaches that led to the identification of small Rho GTPases and their regulators as crucial functional players in proper development and function of myelinated peripheral nerves, with a particular emphasis on the cell biology of Schwann cells in health and disease.
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Affiliation(s)
- Sven Krause
- Institute of Cell Biology, Department of Biology, ETH Zürich, Zürich, Switzerland
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18
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19
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Richardson B, Beckett K, Baylies M. Visualizing new dimensions in Drosophila myoblast fusion. Bioessays 2008; 30:423-31. [PMID: 18404690 DOI: 10.1002/bies.20756] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Over several years, genetic studies in the model system, Drosophila melanogastor, have uncovered genes that when mutated, lead to a block in myoblast fusion. Analyses of these gene products have suggested that Arp2/3-mediated regulation of the actin cytoskeleton is crucial to myoblast fusion in the fly. Recent advances in imaging in Drosophila embryos, both in fixed and live preparations, have led to a new appreciation of both the three-dimensional organization of the somatic mesoderm and the cell biology underlying myoblast fusion.
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Affiliation(s)
- Brian Richardson
- Program in Developmental Biology, Sloan Kettering Institute, USA
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20
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Hable WE, Reddy S, Julien L. The Rac1 inhibitor, NSC23766, depolarizes adhesive secretion, endomembrane cycling, and tip growth in the fucoid alga, Silvetia compressa. PLANTA 2008; 227:991-1000. [PMID: 18183417 DOI: 10.1007/s00425-007-0673-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Accepted: 11/23/2007] [Indexed: 05/25/2023]
Abstract
Proper cell morphogenesis is dependent on the establishment and expression of cellular polarity. In the fucoid zygote, cell shape is critical for establishing the developmental pattern of the adult, and is achieved by guiding insertion of new membrane and wall to the rhizoid tip. Selection and growth of the appropriate tip site are accompanied by formation of dynamic actin arrays associated with the actin-nucleating Arp2/3 complex. In eukaryotes, a major pathway for activation of the Arp2/3 complex is via the Rho family GTPase, Rac1, which stimulates the Scar/WAVE complex. To determine whether Rac1 controls actin nucleation in Silvetia compressa (J. Agardh) E. Serrao, T. O. Cho, S. M. Boo et Brawley, we tested the effects of the Rac1-specific inhibitory compound, NSC23766, on actin dependent processes and on actin arrays. We found that NSC23766 disrupted polar secretion of adhesive, polarization of endomembranes, and tip-focused growth in the rhizoid. Similarly, NSC23766 altered actin and Arp2 localization in the growing rhizoid. In contrast, NSC23766 had no effect on selection of the growth site or on cytokinesis. These data suggest that Rac1 participates in nucleation of specific actin arrays in the developing zygote.
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Affiliation(s)
- Whitney E Hable
- Department of Biology, University of Massachusetts Dartmouth, North Dartmouth, MA 02747-2300, USA.
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21
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Richardson BE, Beckett K, Nowak SJ, Baylies MK. SCAR/WAVE and Arp2/3 are crucial for cytoskeletal remodeling at the site of myoblast fusion. Development 2007; 134:4357-67. [PMID: 18003739 DOI: 10.1242/dev.010678] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Myoblast fusion is crucial for formation and repair of skeletal muscle. Here we show that active remodeling of the actin cytoskeleton is essential for fusion in Drosophila. Using live imaging, we have identified a dynamic F-actin accumulation (actin focus) at the site of fusion. Dissolution of the actin focus directly precedes a fusion event. Whereas several known fusion components regulate these actin foci, others target additional behaviors required for fusion. Mutations in kette/Nap1, an actin polymerization regulator, lead to enlarged foci that do not dissolve, consistent with the observed block in fusion. Kette is required to positively regulate SCAR/WAVE, which in turn activates the Arp2/3 complex. Mutants in SCAR and Arp2/3 have a fusion block and foci phenotype, suggesting that Kette-SCAR-Arp2/3 participate in an actin polymerization event required for focus dissolution. Our data identify a new paradigm for understanding the mechanisms underlying fusion in myoblasts and other tissues.
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Affiliation(s)
- Brian E Richardson
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10021, USA
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22
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Pommereit D, Wouters FS. An NGF-induced Exo70-TC10 complex locally antagonises Cdc42-mediated activation of N-WASP to modulate neurite outgrowth. J Cell Sci 2007; 120:2694-705. [PMID: 17635999 DOI: 10.1242/jcs.03475] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
NGF-induced differentiation of PC12 cells is mediated by actin-polymerisation-driven membrane protrusion, involving GTPase signalling pathways that activate actin nucleation promoting factors such as the neural Wiskott-Aldrich syndrome protein (N-WASP). Expression of the exocyst subunit Exo70 in PC12 cells and neurons leads to the generation of numerous membrane protrusions, an effect that is strongly potentiated upon NGF-induced differentiation. Förster resonance energy transfer (FRET) imaging by fluorescence lifetime microscopy (FLIM) reveals an NGF-induced interaction of activated TC10 with Exo70. Expression of dominant-negative mutants and siRNA-mediated knockdown implicates N-WASP in NGF-induced Exo70-TC10-mediated membrane protrusion. However, FRET imaging of N-WASP activation levels of cells expressing Exo70 and/or constitutively active TC10 reveals that this complex locally antagonises the NGF-induced activation of N-WASP in membrane protrusions. Experiments involving siRNA-mediated knockdown of Cdc42 and overexpression of constitutively active Cdc42 confirm that the Exo70-TC10 complex mainly targets the NGF-induced Cdc42-dependent activation of N-WASP. Our results show that Exo70 is responsible for the correct targeting of the Exo70-TC10 complex to sites of membrane protrusion. The functional uncoupling between both pathways represents a novel regulatory mechanism that enables switching between morphologically distinct – Cdc42- or TC10-dominated – forms of cellular membrane outgrowth.
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Affiliation(s)
- Dagmar Pommereit
- European Neuroscience Institute-Göttingen, Cell Biophysics Group and DFG Research Center for Molecular Physiology of the Brain (CMPB), D-37073 Göttingen, Germany
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23
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Singh MK, Cowell L, Seo S, O’Neill GM, Golemis EA. Molecular basis for HEF1/NEDD9/Cas-L action as a multifunctional co-ordinator of invasion, apoptosis and cell cycle. Cell Biochem Biophys 2007; 48:54-72. [PMID: 17703068 PMCID: PMC1976382 DOI: 10.1007/s12013-007-0036-3] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 04/11/2007] [Accepted: 11/30/1999] [Indexed: 10/23/2022]
Abstract
Upregulation of the scaffolding protein HEF1, also known as NEDD9 and Cas-L, has recently been identified as a pro-metastatic stimulus in a number of different solid tumors, and has also been strongly associated with pathogenesis of BCR-Abl-dependent tumors. As the evidence mounts for HEF1/NEDD9/Cas-L as a key player in metastatic cancer, it is timely to review the molecular regulation of HEF1/NEDD9/Cas-L. Most of the mortality associated with cancer arises from uncontrolled metastases, thus a better understanding of the properties of proteins specifically associated with promotion of this process may yield insights that improve cancer diagnosis and treatment. In this review, we summarize the extensive literature regarding HEF1/NEDD9/Cas-L expression and function in signaling relevant to cell attachment, migration, invasion, cell cycle, apoptosis, and oncogenic signal transduction. The complex function of HEF1/NEDD9/Cas-L revealed by this analysis leads us to propose a model in which alleviation of cell cycle checkpoints and acquired resistance to apoptosis is permissive for a HEF1/NEDD9/Cas-L-promoted pro-metastatic phenotype.
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Affiliation(s)
- Mahendra K. Singh
- Division of Basic Science, Fox Chase Cancer Center, Philadelphia, PA, USA
| | - Lauren Cowell
- Oncology Research Unit, The Children’s Hospital at Westmead, NSW, Australia
- Discipline of Paediatrics and Child Health, The University of Sydney, NSW, Australia
| | - Sachiko Seo
- Department of Hematology and Oncology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
| | - Geraldine M. O’Neill
- Oncology Research Unit, The Children’s Hospital at Westmead, NSW, Australia
- Discipline of Paediatrics and Child Health, The University of Sydney, NSW, Australia
| | - Erica A. Golemis
- Division of Basic Science, Fox Chase Cancer Center, Philadelphia, PA, USA
- corresponding author: Erica A. Golemis, Fox Chase Cancer Center, 333 Cottman Ave. Philadelphia, PA 19111 USA, Phone: 215-728-2860, FAX: 215-728-3616,
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24
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Chang F, Lemmon CA, Park D, Romer LH. FAK potentiates Rac1 activation and localization to matrix adhesion sites: a role for betaPIX. Mol Biol Cell 2006; 18:253-64. [PMID: 17093062 PMCID: PMC1751318 DOI: 10.1091/mbc.e06-03-0207] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
FAK, a cytoplasmic protein tyrosine kinase, is activated and localized to focal adhesions upon cell attachment to extracellular matrix. FAK null cells spread poorly and exhibit altered focal adhesion turnover. Rac1 is a member of the Rho-family GTPases that promotes membrane ruffling, leading edge extension, and cell spreading. We investigated the activation and subcellular location of Rac1 in FAK null and FAK reexpressing fibroblasts. FAK reexpressers had a more robust pattern of Rac1 activation after cell adhesion to fibronectin than the FAK null cells. Translocation of Rac1 to focal adhesions was observed in FAK reexpressers, but seldom in FAK null cells. Experiments with constitutively active L61Rac1 and dominant negative N17Rac1 indicated that the activation state of Rac1 regulated its localization to focal adhesions. We demonstrated that FAK tyrosine-phosphorylated betaPIX and thereby increased its binding to Rac1. In addition, betaPIX facilitated the targeting of activated Rac1 to focal adhesions and the efficiency of cell spreading. These data indicate that FAK has a role in the activation and focal adhesion translocation of Rac1 through the tyrosine phosphorylation of betaPIX.
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Affiliation(s)
- Fumin Chang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
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25
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Zhou FQ, Snider WD. Intracellular control of developmental and regenerative axon growth. Philos Trans R Soc Lond B Biol Sci 2006; 361:1575-92. [PMID: 16939976 PMCID: PMC1664665 DOI: 10.1098/rstb.2006.1882] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Accepted: 06/19/2006] [Indexed: 01/10/2023] Open
Abstract
Axon growth is a highly regulated process that requires stimulating signals from extracellular factors. The extracellular signals are then transduced to regulate coordinately gene expression and local axon assembly. Growth factors, especially neurotrophins that act via receptor tyrosine kinases, have been heavily studied as extracellular factors that stimulate axon growth. Downstream of receptor tyrosine kinases, recent studies have suggested that phosphatidylinositol-3 kinase (PI3K) regulates local assembly of axonal cytoskeleton, especially microtubules, via glycogen synthase kinase 3beta (GSK-3beta) and multiple microtubule binding proteins. The role of extracellular signal regulated kinase (ERK) signalling in regulation of local axon assembly is less clear, but may involve the regulation of local protein translation. Gene expression during axon growth is regulated by transcription factors, among which cyclic AMP response element binding protein and nuclear factors of activated T-cells (NFATs) are known to be required for neurotrophin (NT)-induced axon extension. In addition to growth factors, extracellular matrix molecules and neuronal activity contribute importantly to control axon growth. Increasingly, evidence suggests that these influences act to enhance growth via coordinating with growth factor signalling. Finally, evidence is emerging that developmental versus regenerative axon growth may be mediated by distinct signalling pathways, both at the level of gene transcription and at the level of local axon assembly.
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Affiliation(s)
- Feng-Quan Zhou
- Department of Orthopedic Surgery, The Johns Hopkins University School of MedicineBaltimore, MD 21287, USA
- Department of Neuroscience, The Johns Hopkins University School of MedicineBaltimore, MD 21205, USA
| | - William D Snider
- UNC-Neuroscience Center, University of North Carolina at Chapel Hill8109 Neuroscience Research Building, 103 Mason Farm Road, Chapel Hill, NC 27599-7250, USA
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26
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Weiner OD, Rentel MC, Ott A, Brown GE, Jedrychowski M, Yaffe MB, Gygi SP, Cantley LC, Bourne HR, Kirschner MW. Hem-1 complexes are essential for Rac activation, actin polymerization, and myosin regulation during neutrophil chemotaxis. PLoS Biol 2006; 4:e38. [PMID: 16417406 PMCID: PMC1334198 DOI: 10.1371/journal.pbio.0040038] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Accepted: 12/01/2005] [Indexed: 12/30/2022] Open
Abstract
Migrating cells need to make different actin assemblies at the cell's leading and trailing edges and to maintain physical separation of signals for these assemblies. This asymmetric control of activities represents one important form of cell polarity. There are significant gaps in our understanding of the components involved in generating and maintaining polarity during chemotaxis. Here we characterize a family of complexes (which we term leading edge complexes), scaffolded by hematopoietic protein 1 (Hem-1), that organize the neutrophil's leading edge. The Wiskott-Aldrich syndrome protein family Verprolin-homologous protein (WAVE)2 complex, which mediates activation of actin polymerization by Rac, is only one member of this family. A subset of these leading edge complexes are biochemically separable from the WAVE2 complex and contain a diverse set of potential polarity-regulating proteins. RNA interference-mediated knockdown of Hem-1-containing complexes in neutrophil-like cells: (a) dramatically impairs attractant-induced actin polymerization, polarity, and chemotaxis; (b) substantially weakens Rac activation and phosphatidylinositol-(3,4,5)-tris-phosphate production, disrupting the (phosphatidylinositol-(3,4,5)-tris-phosphate)/Rac/F-actin-mediated feedback circuit that organizes the leading edge; and (c) prevents exclusion of activated myosin from the leading edge, perhaps by misregulating leading edge complexes that contain inhibitors of the Rho-actomyosin pathway. Taken together, these observations show that versatile Hem-1-containing complexes coordinate diverse regulatory signals at the leading edge of polarized neutrophils, including but not confined to those involving WAVE2-dependent actin polymerization.
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Affiliation(s)
- Orion D Weiner
- 1Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
- 6Cardivascular Research Institute, University of California San Francisco, California, United States of America
| | - Maike C Rentel
- 2Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Alex Ott
- 2Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Glenn E Brown
- 3Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Mark Jedrychowski
- 4Department of Cell Biology and Taplin Biological Mass Spectrometry Facility, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael B Yaffe
- 3Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Steven P Gygi
- 4Department of Cell Biology and Taplin Biological Mass Spectrometry Facility, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Lewis C Cantley
- 5Department of Systems Biology, Harvard Medical School, Division of Signal Transduction, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Henry R Bourne
- 2Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Marc W Kirschner
- 1Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
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27
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Mathur J. Local interactions shape plant cells. Curr Opin Cell Biol 2005; 18:40-6. [PMID: 16343888 DOI: 10.1016/j.ceb.2005.12.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2005] [Accepted: 12/01/2005] [Indexed: 12/23/2022]
Abstract
Plant cell expansion is usually attributed to the considerable osmotic pressure that develops within and impinges upon the cell boundary. Whereas turgor containment within expandable walls explains global expansion, the scalar nature of turgor does not directly suggest a mechanism for achieving the localized, differential growth that is responsible for the diversity of plant-cell forms. The key to achieving local growth in plant cells appears to lie not in harnessing turgor but in using it to identify weak regions in the cell boundary and thus creating discrete intracellular domains for targeting the growth machinery. Membrane-interacting phospholipases, Rho-like proteins and their interactors, an actin-modulating ARP2/3 complex with its upstream regulators, and actin-microtubule interactions play important roles in the intracellular cooperation to shape plant cells.
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Affiliation(s)
- Jaideep Mathur
- Laboratory of Molecular Cell Biology, Department of Plant Agriculture, Crop Science Bldg., 50 Stone Road, Guelph, Ontario, N1G 2W1, Canada.
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28
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Brábek J, Constancio SS, Siesser PF, Shin NY, Pozzi A, Hanks SK. Crk-associated substrate tyrosine phosphorylation sites are critical for invasion and metastasis of SRC-transformed cells. Mol Cancer Res 2005; 3:307-15. [PMID: 15972849 DOI: 10.1158/1541-7786.mcr-05-0015] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Crk-associated substrate (CAS, p130Cas) is a major tyrosine phosphorylated protein in cells transformed by v-crk and v-src oncogenes. We recently reported that reexpression of CAS in CAS-deficient mouse embryo fibroblasts transformed by oncogenic Src promoted an invasive phenotype associated with enhanced cell migration through Matrigel, organization of actin into large podosome ring and belt structures, activation of matrix metalloproteinase-2, and elevated tyrosine phosphorylation of the focal adhesion proteins FAK and paxillin. We have now extended these studies to examine the mechanism by which CAS achieves these changes and to evaluate the potential role for CAS in promoting in vivo tumor growth and metastasis. Whereas the presence or absence of CAS did not alter the primary growth of subcutaneous-injected Src-transformed mouse embryo fibroblasts, CAS expression was required to promote lung metastasis following removal of the primary tumor. The substrate domain YxxP tyrosines, the major sites of CAS phosphorylation by Src that mediate interactions with Crk, were found to be critical for promoting both invasive and metastatic properties of the cells. The ability of CAS to promote Matrigel invasion, formation of large podosome structures, and tyrosine phosphorylation of Src substrates, including FAK, paxillin, and cortactin, was also strictly dependent on the YxxP tyrosines. In contrast, matrix metalloproteinase-2 activation was most dependent on the CAS SH3 domain, whereas the substrate domain YxxP sites also contributed to this property. Thus multiple CAS-mediated signaling events are implicated in promoting invasive and metastatic properties of Src-transformed cells.
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Affiliation(s)
- Jan Brábek
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37212, USA
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29
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Michelot A, Guérin C, Huang S, Ingouff M, Richard S, Rodiuc N, Staiger CJ, Blanchoin L. The formin homology 1 domain modulates the actin nucleation and bundling activity of Arabidopsis FORMIN1. THE PLANT CELL 2005; 17:2296-313. [PMID: 15994911 PMCID: PMC1182490 DOI: 10.1105/tpc.105.030908] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2005] [Revised: 05/16/2005] [Accepted: 05/19/2005] [Indexed: 05/03/2023]
Abstract
The organization of actin filaments into large ordered structures is a tightly controlled feature of many cellular processes. However, the mechanisms by which actin filament polymerization is initiated from the available pool of profilin-bound actin monomers remain unknown in plants. Because the spontaneous polymerization of actin monomers bound to profilin is inhibited, the intervention of an actin promoting factor is required for efficient actin polymerization. Two such factors have been characterized from yeasts and metazoans: the Arp2/3 complex, a complex of seven highly conserved subunits including two actin-related proteins (ARP2 and ARP3), and the FORMIN family of proteins. The recent finding that Arabidopsis thaliana plants lacking a functional Arp2/3 complex exhibit rather modest morphological defects leads us to consider whether the large FORMIN family plays a central role in the regulation of actin polymerization. Here, we have characterized the mechanism of action of Arabidopsis FORMIN1 (AFH1). Overexpression of AFH1 in pollen tubes has been shown previously to induce abnormal actin cable formation. We demonstrate that AFH1 has a unique behavior when compared with nonplant formins. The activity of the formin homology domain 2 (FH2), containing the actin binding activity, is modulated by the formin homology domain 1 (FH1). Indeed, the presence of the FH1 domain switches the FH2 domain from a tight capper (Kd approximately 3.7 nM) able to nucleate actin filaments that grow only in the pointed-end direction to a leaky capper that allows barbed-end elongation and efficient nucleation of actin filaments from actin monomers bound to profilin. Another exciting feature of AFH1 is its ability to bind to the side and bundle actin filaments. We have identified an actin nucleator that is able to organize actin filaments directly into unbranched actin filament bundles. We suggest that AFH1 plays a central role in the initiation and organization of actin cables from the pool of actin monomers bound to profilin.
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Affiliation(s)
- Alphée Michelot
- Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Joseph Fourier, Unité Mixte de Recherche 5168, F38054, Grenoble, France
| | - Christophe Guérin
- Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Joseph Fourier, Unité Mixte de Recherche 5168, F38054, Grenoble, France
| | - Shanjin Huang
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Mathieu Ingouff
- Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Joseph Fourier, Unité Mixte de Recherche 5168, F38054, Grenoble, France
| | - Stéphane Richard
- Salk Institute, Structural Biology Laboratory, La Jolla, California 92037
| | - Natalia Rodiuc
- Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Joseph Fourier, Unité Mixte de Recherche 5168, F38054, Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Laurent Blanchoin
- Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Joseph Fourier, Unité Mixte de Recherche 5168, F38054, Grenoble, France
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30
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Abstract
Oculocerebrorenal syndrome of Lowe (OCRL) is an X-linked disorder with the hallmark features of congenital cataracts, mental retardation and Fanconi syndrome of the kidney proximal tubules. OCRL was first described in 1952, and exactly four decades later, the gene responsible was identified and found to encode a protein highly homologous to inositol polyphosphate 5-phosphatase. This suggested that Lowe syndrome may represent an inborn error of inositol phosphate metabolism, and subsequent studies confirmed that such metabolism is indeed perturbed in Lowe syndrome cells. However, the mechanism by which loss of function of the OCRL1 protein brings about Lowe syndrome remains ill defined. In this review, I will discuss our understanding of OCRL1, including where it is localized, what it interacts with and what its possible functions might be. I will then discuss possible mechanisms by which loss of OCRL1 may bring about cellular defects that manifest themselves in the pathology of Lowe syndrome.
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Affiliation(s)
- Martin Lowe
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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31
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Ehrenreiter K, Piazzolla D, Velamoor V, Sobczak I, Small JV, Takeda J, Leung T, Baccarini M. Raf-1 regulates Rho signaling and cell migration. ACTA ACUST UNITED AC 2005; 168:955-64. [PMID: 15753127 PMCID: PMC2171799 DOI: 10.1083/jcb.200409162] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Raf kinases relay signals inducing proliferation, differentiation, and survival. The Raf-1 isoform has been extensively studied as the upstream kinase linking Ras activation to the MEK/ERK module. Recently, however, genetic experiments have shown that Raf-1 plays an essential role in counteracting apoptosis, and that it does so independently of its ability to activate MEK. By conditional gene ablation, we now show that Raf-1 is required for normal wound healing in vivo and for the migration of keratinocytes and fibroblasts in vitro. Raf-1-deficient cells show a symmetric, contracted appearance, characterized by cortical actin bundles and by a disordered vimentin cytoskeleton. These defects are due to the hyperactivity and incorrect localization of the Rho-effector Rok-alpha to the plasma membrane. Raf-1 physically associates with Rok-alpha in wild-type (WT) cells, and reintroduction of either WT or kinase-dead Raf-1 in knockout fibroblasts rescues their defects in shape and migration. Thus, Raf-1 plays an essential, kinase-independent function as a spatial regulator of Rho downstream signaling during migration.
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Affiliation(s)
- Karin Ehrenreiter
- Department of Microbiology and Genetics, Max F. Perutz Laboratories, University Departments at the Vienna Biocenter, 1030 Vienna, Austria
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32
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Abstract
The seven-subunit ARP2/3 complex is an efficient modulator of the actin cytoskeleton with well-recognized roles in amoeboid locomotion and subcellular motility of organelles and microbes. The recent identification of different subunit homologs suggests the existence of a functional ARP2/3 complex in higher plants. Mutations in some of the subunits have revealed a pivotal role for the complex in determining the shape of walled cells and focused attention on the interlinked processes of cortical-actin organization, growth-site selection, organelle motility and actin-microtubule interactions during plant cell morphogenesis. The findings supporting a global conservation of molecular mechanisms for membrane protrusion have been further strengthened by the identification of plant homologs of upstream regulators of the complex such as PIR121, NAP125 and HSPC300. As discussed here, the recent studies suggest that there might be hitherto unappreciated molecular and cell-biological commonalities between protrusion mediated motility of animal cells and polarized, expansion-mediated growth of plant cells.
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Affiliation(s)
- Jaideep Mathur
- Molecular Cell Biology Laboratory, Department of Plant Agriculture, University of Guelph, 50 Stone Road, Guelph, Ontario, Canada, N1G 2W1.
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33
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Li Y, Sorefan K, Hemmann G, Bevan MW. Arabidopsis NAP and PIR regulate actin-based cell morphogenesis and multiple developmental processes. PLANT PHYSIOLOGY 2004; 136:3616-27. [PMID: 15516496 PMCID: PMC527160 DOI: 10.1104/pp.104.053173] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The actin cytoskeleton mediates cellular processes through the dynamic regulation of the time, location, and extent of actin polymerization. Actin polymerization is controlled by several types of evolutionarily conserved proteins, including those comprising the ARP2/3 complex. In animal cells ARP2/3 activity is regulated by WAVE complexes that contain WAVE/SCAR proteins, PIR121, Nap125, and other proteins. The activity of the WAVE complex is regulated by Rho-GTPase-mediated signaling that leads to ARP2/3 activation by WAVE/SCAR proteins. We describe in this report Arabidopsis (Arabidopsis thaliana) genes encoding Nap and PIR proteins. Light-grown Atnap-1 and Atpir-1 mutant plants displayed altered leaf, inflorescence, silique, and seed set phenotypes. Dark-grown Atnap-1 and Atpir-1 seedlings also exhibited longer roots, enhanced skotomorphogenesis and Glc responses, and shorter thicker hypocotyls than those of wild type, showing that AtNAP and AtPIR participate in a variety of growth and developmental processes. Mutations in AtNAP and AtPIR caused cell morphology defects in cotyledon pavement cells and trichomes seen in mutants in ARP2/3 subunits and in plants expressing constitutively active Rop2 GTPase. The patterns and levels of actin polymerization observed in Atnap-1 and Atpir-1 mutant trichome cells and epidermal pavement cell morphology is consistent with Arabidopsis NAP and PIR proteins forming a WAVE complex that activates ARP2/3 activity. The multiple growth and developmental phenotypes of Atnap and Atpir mutants reveals these proteins are also required for a wider variety of cellular functions in addition to regulating trichome cell growth.
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Affiliation(s)
- Yunhai Li
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
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34
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Toda M, Dawson M, Nakamura T, Munro PMG, Richardson RM, Bailly M, Ono SJ. Impact of Engagement of FcϵRI and CC Chemokine Receptor 1 on Mast Cell Activation and Motility. J Biol Chem 2004; 279:48443-8. [PMID: 15337751 DOI: 10.1074/jbc.m408725200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
CC chemokines participate in the recruitment and activation of immune cells through CC chemokine receptors (CCRs). Here, we report that cross-talk between CCR1-mediated signaling pathway and FcepsilonRI-mediated signaling pathway affects degranulation positively but affects chemotaxis of mast cells adversely. Costimulation via FcepsilonRI engagement with IgE/antigen and CCR1 engagement with recombinant human CCL3 synergistically enhanced degranulation in rat basophilic leukemia-2H3 cells expressing human CCR1 (RBL-CCR1). Interestingly, FcepsilonRI engagement inhibited CCL3-mediated chemotaxis and membrane ruffling of RBL-CCR1 cells. Small GTP-binding proteins of the Rho family, Rac, Cdc42, and Rho control chemotaxis by mediating the reorganization of the actin cytoskeleton. Both a Rho inhibitor C3 exoenzyme and a Rho kinase (ROCK) inhibitor Y-27632 inhibited chemotaxis of RBL-CCR1 cells toward CCL3, indicating that activation of the Rho/ROCK signaling pathway is required for the CCL3-mediated chemotaxis of the cells. Costimulation with IgE/antigen and CCL3 enhanced Rac and Cdc42 activation but decreased ROCK activation in RBL-CCR1 cells compared with that in the cells stimulated with CCL3 alone. These results suggest that costimulation via FcepsilonRI and CCR1 engagements induced 1) inhibition of membrane ruffling, 2) decreased ROCK activation, and 3) reciprocal imbalance between Small GTP-binding proteins of the Rho family, which result in the inhibition of chemotaxis of RBL-CCR1 cells. The cross-talk between FcepsilonRI-mediated signaling pathway and CCR-mediated signaling pathway would induce optimal activation and arrested chemotaxis of mast cells, thus contributing to allergic inflammation.
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Affiliation(s)
- Masako Toda
- Division of Ocular Immunology, Institutes of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
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35
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Altan ZM, Fenteany G. c-Jun N-terminal kinase regulates lamellipodial protrusion and cell sheet migration during epithelial wound closure by a gene expression-independent mechanism. Biochem Biophys Res Commun 2004; 322:56-67. [PMID: 15313173 DOI: 10.1016/j.bbrc.2004.07.079] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2004] [Indexed: 02/05/2023]
Abstract
c-Jun N-terminal kinase (JNK) is emerging as an important regulator of cell migration. Perturbing the JNK signaling pathway with three structurally and mechanistically distinct inhibitors that selectively target either JNKs themselves or the upstream mixed-lineage kinases, we found dramatic inhibition of membrane protrusion and cell sheet migration during wound closure in Madin-Darby canine kidney (MDCK) epithelial cell monolayers. Extension of lamellipodia is blocked from the earliest times after wounding in the presence of JNK pathway inhibitors, whereas assembly of non-protrusive actin bundles at the wound margin is unaffected. Inhibitors of the other mitogen-activated protein kinase (MAPK) pathways, the extracellular signal-regulated kinase and p38 MAPK pathways, only have comparatively weak or marginal inhibitory effects on wound closure. Multiple splice variants of both JNK1 and JNK2 are expressed in MDCK cells, and JNK1 and JNK2 are rapidly and transiently activated upon wounding. Phosphorylation of c-Jun does not appear relevant to MDCK wound closure, and membrane protrusion directly after wounding is not affected by inhibitors of RNA or protein synthesis. While most known substrates of JNK are transcription factors or proteins regulating apoptosis, our data indicate that JNK regulates protrusion and migration in a gene expression-independent manner and suggest an important cytoplasmic role for JNK in the control of cell motility.
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Affiliation(s)
- Z Melis Altan
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
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36
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Stradal TEB, Rottner K, Disanza A, Confalonieri S, Innocenti M, Scita G. Regulation of actin dynamics by WASP and WAVE family proteins. Trends Cell Biol 2004; 14:303-11. [PMID: 15183187 DOI: 10.1016/j.tcb.2004.04.007] [Citation(s) in RCA: 208] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Theresia E B Stradal
- German Research Centre for Biotechnology, Department of Cell Biology, Mascheroder Weg 1, D-38124 Braunschweig, Germany
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37
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Abstract
Dynamic actin filaments contribute to cell migration, organelle movements, memory, and gene regulation. These dynamic processes are often regulated by extracellular and?or cell cycle signals. Regulation targets, not actin itself, but the factors that determine it's dynamic properties. Thus, filament nucleation, rate and duration of elongation, and depolymerization are each controlled with regard to time and?or space. Two mechanisms exist for nucleating filaments de novo, the Arp23 complex and the formins; multiple pathways regulate each. A new filament elongates rapidly but transiently before its barbed end is capped. Rapid capping allows the cell to maintain fine temporal and spatial control over F-actin distribution. Modulation of capping protein activity and its access to barbed ends is emerging as a site of local regulation. Finally, to maintain a steady state filaments must depolymerize. Depolymerization can limit the rate of new filament nucleation and elongation. The activity of ADF?cofilin, which facilitates depolymerization, is also regulated by multiple inputs. This chapter describes (1) mechanism and regulation of new filament formation, (2) mechanism of enhancing elongation at barbed ends, (3) capping proteins and their regulators, and (4) recycling of actin monomers from filamentous actin (F-actin) back to globular actin (G-actin).
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Affiliation(s)
- Sally H Zigmond
- Biology Department, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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