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Antitumor Effects of Ral-GTPases Downregulation in Glioblastoma. Int J Mol Sci 2022; 23:ijms23158199. [PMID: 35897776 PMCID: PMC9330696 DOI: 10.3390/ijms23158199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 07/19/2022] [Accepted: 07/22/2022] [Indexed: 12/20/2022] Open
Abstract
Glioblastoma (GBM) is the most common tumor in the central nervous system in adults. This neoplasia shows a high capacity of growth and spreading to the surrounding brain tissue, hindering its complete surgical resection. Therefore, the finding of new antitumor therapies for GBM treatment is a priority. We have previously described that cyclin D1-CDK4 promotes GBM dissemination through the activation of the small GTPases RalA and RalB. In this paper, we show that RalB GTPase is upregulated in primary GBM cells. We found that the downregulation of Ral GTPases, mainly RalB, prevents the proliferation of primary GBM cells and triggers a senescence-like response. Moreover, downregulation of RalA and RalB reduces the viability of GBM cells growing as tumorspheres, suggesting a possible role of these GTPases in the survival of GBM stem cells. By using mouse subcutaneous xenografts, we have corroborated the role of RalB in GBM growth in vivo. Finally, we have observed that the knockdown of RalB also inhibits cell growth in temozolomide-resistant GBM cells. Overall, our work shows that GBM cells are especially sensitive to Ral-GTPase availability. Therefore, we propose that the inactivation of Ral-GTPases may be a reliable therapeutic approach to prevent GBM progression and recurrence.
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2
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Ganapathy S, Liu J, Yu T, Xiong R, Zhang Q, Makriyannis A, Chen C. PKC is an indispensable factor in promoting environmental toxin chromium-mediated transformation and drug resistance. Aging (Albany NY) 2022; 14:1678-1690. [PMID: 35210368 PMCID: PMC8908929 DOI: 10.18632/aging.203917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 02/08/2022] [Indexed: 11/25/2022]
Abstract
Hexavalent chromium [Cr(VI)] pollution is a serious environmental problem, due to not only its toxicity but also carcinogenesis. Although studies reveal several features of Cr(VI)-induced carcinogenesis, the underlying mechanisms of how Cr(VI) orchestrates multiple mitogenic pathways to promote tumor initiation and progression remain not fully understood. Src/Ras and other growth-related pathways are shown to be key players in Cr(VI)-initiated tumor prone actions. The role of protein kinase C (PKC, an important signal transducer) in Cr(VI)-mediated carcinogenesis has not been thoroughly investigated. In this study, using human bronchial/lung epithelial cells and keratinocytes, we demonstrate that PKC activity is increased by transient or chronic Cr(VI) exposure, which plays no role in the activation of Src/Ras signaling and ROS upregulation by this metal toxin. PKC in chronic Cr(VI)-treated cells stabilizes Bcl-2 to mitigate doxorubicin (an anti-cancer drug)-mediated apoptosis. After the suppression of this kinase by GO6976 (a PKC inhibitor), the cells chronically exposed to Cr(VI) partially regain the sensitivity to doxorubicin. However, when co-suppressed PKC and Ras, the chronic Cr(VI)-treated cells become fully responsive to doxorubicin and are unable to be transformed. Taken together, our study provides a new insight into the mechanisms, in which PKC is an indispensable player and cooperates with other mitogenic pathways to achieve Cr(VI)-induced carcinogenesis as well as to establish drug resistance. The data also suggest that active PKC can serve as a potential biomarker for early detection of health damages by Cr(VI) and therapeutic target for developing new treatments for diseases caused by Cr(VI).
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Affiliation(s)
- Suthakar Ganapathy
- Center for Drug Discovery, Northeastern University, Boston, MA 02115, USA
| | - Jian Liu
- The Department of Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, PR China
| | - Tianqi Yu
- Center for Drug Discovery, Northeastern University, Boston, MA 02115, USA
| | - Rui Xiong
- The Department of Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, PR China
| | - Qiang Zhang
- The Department of Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, PR China
| | | | - Changyan Chen
- Center for Drug Discovery, Northeastern University, Boston, MA 02115, USA
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Duong T, Rasmussen NR, Reiner DJ. Insulated Switches: Dual-Function Protein RalGEF RGL-1 Promotes Developmental Fidelity. Int J Mol Sci 2020; 21:ijms21207610. [PMID: 33076222 PMCID: PMC7588897 DOI: 10.3390/ijms21207610] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/10/2020] [Accepted: 10/12/2020] [Indexed: 02/05/2023] Open
Abstract
The C. elegans vulva is an excellent model for the study of developmental biology and cell–cell signaling. The developmental induction of vulval precursor cells (VPCs) to assume the 3°-3°-2°-1°-2°-3° patterning of cell fates occurs with 99.8% accuracy. During C. elegans vulval development, an EGF signal from the anchor cell initiates the activation of RasLET-60 > RafLIN-45 > MEKMEK-2 > ERKMPK-1 signaling cascade to induce the 1° cell. The presumptive 1° cell signals its two neighboring cells via NotchLIN-12 to develop 2° cells. In addition, RasLET-60 switches effectors to RalGEFRGL-1 > RalRAL-1 to promote 2° fate. Shin et al. (2019) showed that RalGEFRGL-1 is a dual-function protein in VPCs fate patterning. RalGEFRGL-1 functions as a scaffold for PDKPDK-1 > AktAKT-1/2 modulatory signaling to promote 1° fate in addition to propagating the RasLET-60 modulatory signal through RalRAL-1 to promote 2° fate. The deletion of RalGEFRGL-1 increases the frequency of VPC patterning errors 15-fold compared to the wild-type control. We speculate that RalGEFRGL-1 represents an “insulated switch”, whereby the promotion of one signaling activity curtails the promotion of the opposing activity. This property might increase the impact of the switch on fidelity more than two separately encoded proteins could. Understanding how developmental fidelity is controlled will help us to better understand the origins of cancer and birth defects, which occur in part due to the misspecification of cell fates.
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Affiliation(s)
- Tam Duong
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Texas A&M University, Houston, TX 77030, USA; (T.D.); (N.R.R.)
- Department of Translational Medical Science, College of Medicine, Texas A&M Health Science Center, Texas A&M University, Houston, TX 77030, USA
| | - Neal R. Rasmussen
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Texas A&M University, Houston, TX 77030, USA; (T.D.); (N.R.R.)
- Department of Translational Medical Science, College of Medicine, Texas A&M Health Science Center, Texas A&M University, Houston, TX 77030, USA
| | - David J. Reiner
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Texas A&M University, Houston, TX 77030, USA; (T.D.); (N.R.R.)
- Department of Translational Medical Science, College of Medicine, Texas A&M Health Science Center, Texas A&M University, Houston, TX 77030, USA
- Correspondence:
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4
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Zhang Y, Luu BE, Storey KB. FoxO4 activity is regulated by phosphorylation and the cellular environment during dehydration in the African clawed frog, Xenopus laevis. Biochim Biophys Acta Gen Subj 2018; 1862:1721-1728. [DOI: 10.1016/j.bbagen.2018.05.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 04/07/2018] [Accepted: 05/04/2018] [Indexed: 01/10/2023]
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5
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Krygowska AA, Castellano E. PI3K: A Crucial Piece in the RAS Signaling Puzzle. Cold Spring Harb Perspect Med 2018; 8:cshperspect.a031450. [PMID: 28847905 DOI: 10.1101/cshperspect.a031450] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
RAS proteins are key signaling switches essential for control of proliferation, differentiation, and survival of eukaryotic cells. RAS proteins are mutated in 30% of human cancers. In addition, mutations in upstream or downstream signaling components also contribute to oncogenic activation of the pathway. RAS proteins exert their functions through activation of several signaling pathways and dissecting the contributions of these effectors in normal cells and in cancer is an ongoing challenge. In this review, we summarize our current knowledge about how RAS regulates type I phosphatidylinositol 3-kinase (PI3K), one of the main RAS effectors. RAS signaling through PI3K is necessary for normal lymphatic vasculature development and for RAS-induced transformation in vitro and in vivo, especially in lung cancer, where it is essential for tumor initiation and necessary for tumor maintenance.
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Affiliation(s)
- Agata Adelajda Krygowska
- Centre for Cancer and Inflammation, Barts Cancer Institute, Queen Mary University of London, London EC1M 6BQ, United Kingdom
| | - Esther Castellano
- Centre for Cancer and Inflammation, Barts Cancer Institute, Queen Mary University of London, London EC1M 6BQ, United Kingdom
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Moghadam AR, Patrad E, Tafsiri E, Peng W, Fangman B, Pluard TJ, Accurso A, Salacz M, Shah K, Ricke B, Bi D, Kimura K, Graves L, Najad MK, Dolatkhah R, Sanaat Z, Yazdi M, Tavakolinia N, Mazani M, Amani M, Ghavami S, Gartell R, Reilly C, Naima Z, Esfandyari T, Farassati F. Ral signaling pathway in health and cancer. Cancer Med 2017; 6:2998-3013. [PMID: 29047224 PMCID: PMC5727330 DOI: 10.1002/cam4.1105] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 04/10/2017] [Accepted: 04/14/2017] [Indexed: 12/12/2022] Open
Abstract
The Ral (Ras-Like) signaling pathway plays an important role in the biology of cells. A plethora of effects is regulated by this signaling pathway and its prooncogenic effectors. Our team has demonstrated the overactivation of the RalA signaling pathway in a number of human malignancies including cancers of the liver, ovary, lung, brain, and malignant peripheral nerve sheath tumors. Additionally, we have shown that the activation of RalA in cancer stem cells is higher in comparison with differentiated cancer cells. In this article, we review the role of Ral signaling in health and disease with a focus on the role of this multifunctional protein in the generation of therapies for cancer. An improved understanding of this pathway can lead to development of a novel class of anticancer therapies that functions on the basis of intervention with RalA or its downstream effectors.
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Affiliation(s)
- Adel Rezaei Moghadam
- Department of Human Anatomy and Cell ScienceUniversity of ManitobaWinnipegCanada
| | - Elham Patrad
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Elham Tafsiri
- Department of Pediatrics, Columbia Presbyterian Medical CenterNew YorkNew York
| | - Warner Peng
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Benjamin Fangman
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Timothy J Pluard
- Saint Luke's HospitalUniversity of Missouri at Kansas CityKansas CityMissouri
| | - Anthony Accurso
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Michael Salacz
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Kushal Shah
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Brandon Ricke
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Danse Bi
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Kyle Kimura
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Leland Graves
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Marzieh Khajoie Najad
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Roya Dolatkhah
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Zohreh Sanaat
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Mina Yazdi
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Naeimeh Tavakolinia
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Mohammad Mazani
- Pasteur Institute of IranTehranIran
- Ardabil University of Medical Sciences, BiochemistryArdabilIran
| | - Mojtaba Amani
- Pasteur Institute of IranTehranIran
- Ardabil University of Medical Sciences, BiochemistryArdabilIran
| | - Saeid Ghavami
- Department of Human Anatomy and Cell ScienceUniversity of ManitobaWinnipegCanada
| | - Robyn Gartell
- Department of Pediatrics, Columbia Presbyterian Medical CenterNew YorkNew York
| | - Colleen Reilly
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Zaid Naima
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Tuba Esfandyari
- Department of Medicine, Molecular Medicine LaboratoryThe University of Kansas Medical SchoolKansas CityKansas
| | - Faris Farassati
- Research Service (151)Kansas City Veteran Affairs Medical Center & Midwest Biomedical Research Foundation4801 E Linwood BlvdKansas CityMissouri64128‐2226
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7
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Ganapathy S, Li P, Lafontant J, Xiong R, Yu T, Zhang G, Chen C. Chromium IV exposure, via Src/Ras signaling, promotes cell transformation. Mol Carcinog 2017; 56:1808-1815. [PMID: 28218450 DOI: 10.1002/mc.22639] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 02/13/2017] [Accepted: 02/16/2017] [Indexed: 01/01/2023]
Abstract
Hexavalent chromium [Cr(VI)] is a well-known environment carcinogen. The exposure of Cr(VI) through contaminated soil, air particles, and drinking water is a strong concern for the public health worldwide. While many studies have been done, it remains unclear which intracellular molecules transduce Cr(VI)-mediated carcinogenic signaling in cells to promote cancer. In this study, we demonstrated that upon Cr(VI) treatment, the intracellular receptor src was activated, which further upregulated Ras activity, leading to the augmentation of ROS and onset of ER stress in human lung epithelial BEAS-2B or keratinocytes. These cells were formed colonies in soft agar cultures following the persistent Cr(VI) treatment. Furthermore, anti-apoptotic factor Bcl-2 was upregulated and activated in the colonies. Thus, our study suggests that Cr(VI), though activating the src and Ras signaling axis, perturbs redox state and invokes ER stress for the establishment of carcinogenic actions in the cells. In this process, Bcl-2 appears playing an important role. By uncovering these intracellular targets, our study may help developing novel strategies for better environmental protection, especially in areas contaminated or polluted by Cr(VI) as well as for effective cancer treatments.
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Affiliation(s)
- Suthakar Ganapathy
- Center for Drug Development, Northeastern University, Boston, Massachusetts
| | - Ping Li
- The First Affiliated Hospital, Zhengzhou University, Zhengzhou, China.,The Institute of Clinic Sciences, Sahlgrenska Academy, Gothenburg, Sweden
| | - Jean Lafontant
- Center for Drug Development, Northeastern University, Boston, Massachusetts
| | - Rui Xiong
- The Institute of Clinic Sciences, Sahlgrenska Academy, Gothenburg, Sweden
| | - Tianqi Yu
- Center for Drug Development, Northeastern University, Boston, Massachusetts
| | - Guojun Zhang
- The First Affiliated Hospital, Zhengzhou University, Zhengzhou, China
| | - Changyan Chen
- Center for Drug Development, Northeastern University, Boston, Massachusetts
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The cornerstone K-RAS mutation in pancreatic adenocarcinoma: From cell signaling network, target genes, biological processes to therapeutic targeting. Crit Rev Oncol Hematol 2017; 111:7-19. [PMID: 28259298 DOI: 10.1016/j.critrevonc.2017.01.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 11/15/2016] [Accepted: 01/05/2017] [Indexed: 01/17/2023] Open
Abstract
RAS belongs to the super family of small G proteins and plays crucial roles in signal transduction from membrane receptors in the cell. Mutations of K-RAS oncogene lead to an accumulation of GTP-bound proteins that maintains an active conformation. In the pancreatic ductal adenocarcinoma (PDAC), one of the most deadly cancers in occidental countries, mutations of the K-RAS oncogene are nearly systematic (>90%). Moreover, K-RAS mutation is the earliest genetic alteration occurring during pancreatic carcinogenetic sequence. In this review, we discuss the central role of K-RAS mutations and their tremendous diversity of biological properties by the interconnected regulation of signaling pathways (MAPKs, NF-κB, PI3K, Ral…). In pancreatic ductal adenocarcinoma, transcriptome analysis and preclinical animal models showed that K-RAS mutation alters biological behavior of PDAC cells (promoting proliferation, migration and invasion, evading growth suppressors, regulating mucin pattern, and miRNA expression). K-RAS also impacts tumor microenvironment and PDAC metabolism reprogramming. Finally we discuss therapeutic targeting strategies of K-RAS that have been developed without significant clinical success so far. As K-RAS is considered as the undruggable target, targeting its multiple effectors and target genes should be considered as potential alternatives.
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9
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Zhang X, Kim KM. Multifactorial Regulation of G Protein-Coupled Receptor Endocytosis. Biomol Ther (Seoul) 2017; 25:26-43. [PMID: 28035080 PMCID: PMC5207461 DOI: 10.4062/biomolther.2016.186] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 11/21/2016] [Accepted: 11/30/2016] [Indexed: 12/26/2022] Open
Abstract
Endocytosis is a process by which cells absorb extracellular materials via the inward budding of vesicles formed from the plasma membrane. Receptor-mediated endocytosis is a highly selective process where receptors with specific binding sites for extracellular molecules internalize via vesicles. G protein-coupled receptors (GPCRs) are the largest single family of plasma-membrane receptors with more than 1000 family members. But the molecular mechanisms involved in the regulation of GPCRs are believed to be highly conserved. For example, receptor phosphorylation in collaboration with β-arrestins plays major roles in desensitization and endocytosis of most GPCRs. Nevertheless, a number of subsequent studies showed that GPCR regulation, such as that by endocytosis, occurs through various pathways with a multitude of cellular components and processes. This review focused on i) functional interactions between homologous and heterologous pathways, ii) methodologies applied for determining receptor endocytosis, iii) experimental tools to determine specific endocytic routes, iv) roles of small guanosine triphosphate-binding proteins in GPCR endocytosis, and v) role of post-translational modification of the receptors in endocytosis.
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Affiliation(s)
- Xiaohan Zhang
- Pharmacology Laboratory, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Kyeong-Man Kim
- Pharmacology Laboratory, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
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10
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Inhibition of skeletal muscle atrophy during torpor in ground squirrels occurs through downregulation of MyoG and inactivation of Foxo4. Cryobiology 2016; 73:112-9. [PMID: 27593478 DOI: 10.1016/j.cryobiol.2016.08.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 08/15/2016] [Accepted: 08/31/2016] [Indexed: 12/20/2022]
Abstract
Foxo4 and MyoG proteins regulate the transcription of numerous genes, including the E3 ubiquitin ligases MAFbx and MuRF1, which are activated in skeletal muscle under atrophy-inducing conditions. In the thirteen-lined ground squirrel, there is little muscle wasting that occurs during hibernation, a process characterized by bouts of torpor and arousal, despite virtual inactivity. Consequently, we were interested in studying the regulatory role of Foxo4 and MyoG on ubiquitin ligases throughout torpor-arousal cycles. Findings indicate that MAFbx and MuRF1 decreased during early torpor (ET) by 42% and 40%, respectively, relative to euthermic control (EC), although MuRF1 expression subsequently increased at late torpor (LT). The expression pattern of MyoG most closely resembled that of MAFbx, with levels decreasing during LT. In addition, the phosphorylation of Foxo4 at Thr-451 showed an initial increase during EN, followed by a decline throughout the remainder of the torpor-arousal cycle, suggesting Foxo4 inhibition. This trend was mirrored by inhibition of the Ras-Ral pathway, as the Ras and Ral proteins were decreased by 77% and 41% respectively, at ET. Foxo4 phosphorylation at S197 was depressed during entrance and torpor, suggesting Foxo4 nuclear localization, and possibly regulating the increase in MuRF1 levels at LT. These findings indicate that signaling pathways involved in regulating muscle atrophy, such as MyoG and Foxo4 through the Ras-Ral pathway, contribute to important muscle-specific changes during hibernation. Therefore, this data provides novel insight into the molecular mechanisms regulating muscle remodeling in a hibernator model.
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11
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Zheng M, Zhang X, Sun N, Min C, Zhang X, Kim KM. RalA employs GRK2 and β-arrestins for the filamin A-mediated regulation of trafficking and signaling of dopamine D2 and D3 receptor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2072-83. [PMID: 27188791 DOI: 10.1016/j.bbamcr.2016.05.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 05/10/2016] [Accepted: 05/13/2016] [Indexed: 12/13/2022]
Abstract
Filamin A (FLNA) is known to act as platform for the signaling and intracellular trafficking of various GPCRs including dopamine D2 and D3 receptors (D2R, D3R). To understand molecular mechanisms involved in the FLNA-mediated regulation of D2R and D3R, comparative studies were conducted on the signaling and intracellular trafficking of the D2R and D3R in FLNA-knockdown cells, with a specific focus on the roles of the proteins that interact with FLNA and the D2R and D3R. Lowering the level of cellular FLNA caused an elevation in RalA activity and resulted in selective interference with the normal intracellular trafficking and signaling of the D2R and D3R, through GRK2 and β-arrestins, respectively. Knockdown of FLNA or coexpression of active RalA interfered with the recycling of the internalized D2R and resulted in the development of receptor tolerance. Active RalA was found to interact with GRK2 to sequester it from D2R. Knockdown of FLNA or coexpression of active RalA prevented D3R from coupling with G protein. The selective involvement of GRK2- and β-arrestins in the RalA-mediated cellular processes of the D2R and D3R was achieved via their different modes of interactions with the receptor and their distinct functional roles in receptor regulation. Our results show that FLNA is a multi-functional protein that acts as a platform on which D2R and D3R can interact with various proteins, through which selective regulation of these receptors occurs in combination with GRK2 and β-arrestins.
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Affiliation(s)
- Mei Zheng
- Department of Pharmacology, College of Pharmacy, Drug Development Research Institute, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Xiaohan Zhang
- Department of Pharmacology, College of Pharmacy, Drug Development Research Institute, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - NingNing Sun
- Department of Pharmacology, College of Pharmacy, Drug Development Research Institute, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Chengchun Min
- Department of Pharmacology, College of Pharmacy, Drug Development Research Institute, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Xiaowei Zhang
- Department of Pharmacology, College of Pharmacy, Drug Development Research Institute, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Drug Development Research Institute, Chonnam National University, Gwang-Ju 500-757, Republic of Korea.
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12
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Beller M, Blanke S, Brentrup D, Jäckle H. Identification and expression of Ima, a novel Ral-interacting Drosophila protein. Mech Dev 2016; 119 Suppl 1:S253-60. [PMID: 14516694 DOI: 10.1016/s0925-4773(03)00125-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We report the identification of Ima, a novel Drosophila MAGUK-like protein, which contains two WW and four PDZ protein interaction domains and interacts with the small GTPase dRal in the yeast two-hybrid system and pull-down assays. The gene is expressed in distinct spatiotemporal patterns throughout embryonic development. Overexpression of Ima interferes with normal Drosophila development, indicating that the gene functions in a tissue specific manner.
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Affiliation(s)
- Mathias Beller
- Abteilung Molekulare Entwicklungsbiologie, Max-Planck-Institut für biophysikalische Chemie, Am Fassberg, 37077 Göttingen, Germany
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13
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Nussinov R, Tsai CJ, Muratcioglu S, Jang H, Gursoy A, Keskin O. Principles of K-Ras effector organization and the role of oncogenic K-Ras in cancer initiation through G1 cell cycle deregulation. Expert Rev Proteomics 2015; 12:669-82. [DOI: 10.1586/14789450.2015.1100079] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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14
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Zheng M, Zhang X, Guo S, Zhang X, Min C, Cheon SH, Oak MH, Kim YR, Kim KM. Agonist-induced changes in RalA activities allows the prediction of the endocytosis of G protein-coupled receptors. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:77-90. [PMID: 26477566 DOI: 10.1016/j.bbamcr.2015.10.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 10/10/2015] [Accepted: 10/13/2015] [Indexed: 12/31/2022]
Abstract
GTP binding proteins are classified into two families: heterotrimeric large G proteins which are composed of three subunits, and one subunit of small G proteins. Roles of small G proteins in the intracellular trafficking of G protein-coupled receptors (GPCRs) were studied. Among various small G proteins tested, GTP-bound form (G23V) of RalA inhibited the internalization of dopamine D2 receptor independently of the previously reported downstream effectors of RalA, such as Ral-binding protein 1 and PLD. With high affinity for GRK2, active RalA inhibited the GPCR endocytosis by sequestering the GRK2 from receptors. When it was tested for several GPCRs including an endogenous GPCR, lysophosphatidic acid receptor 1, agonist-induced conversion of GTP-bound to GDP-bound RalA, which presumably releases the sequestered GRK2, was observed selectively with the GPCRs which have tendency to undergo endocytosis. Conversion of RalA from active to inactive state occurred by translocation of RGL, a guanine nucleotide exchange factor, from the plasma membrane to cytosol as a complex with Gβγ. These results suggest that agonist-induced Gβγ-mediated conversion of RalA from the GTP-bound form to the GDP-bound form could be a mechanism to facilitate agonist-induced internalization of GPCRs.
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Affiliation(s)
- Mei Zheng
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Xiaohan Zhang
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Shuohan Guo
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Xiaowei Zhang
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Chengchun Min
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Seung Hoon Cheon
- Department of Medicinal Chemistry, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Min-Ho Oak
- College of Pharmacy, Mokpo National University, Muan-gun, Jeollanamdo 534-729, Republic of Korea
| | - Young Ran Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea
| | - Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Republic of Korea.
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Vasseur R, Skrypek N, Duchêne B, Renaud F, Martínez-Maqueda D, Vincent A, Porchet N, Van Seuningen I, Jonckheere N. The mucin MUC4 is a transcriptional and post-transcriptional target of K-ras oncogene in pancreatic cancer. Implication of MAPK/AP-1, NF-κB and RalB signaling pathways. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1849:1375-84. [PMID: 26477488 DOI: 10.1016/j.bbagrm.2015.10.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 09/28/2015] [Accepted: 10/14/2015] [Indexed: 01/26/2023]
Abstract
The membrane-bound mucinMUC4 is a high molecularweight glycoprotein frequently deregulated in cancer. In pancreatic cancer, one of the most deadly cancers in occidental countries, MUC4 is neo-expressed in the preneoplastic stages and thereafter is involved in cancer cell properties leading to cancer progression and chemoresistance. K-ras oncogene is a small GTPase of the RAS superfamily, highly implicated in cancer. K-ras mutations are considered as an initiating event of pancreatic carcinogenesis and K-ras oncogenic activities are necessary components of cancer progression. However, K-ras remains clinically undruggable. Targeting early downstream K-ras signaling in cancer may thus appear as an interesting strategy and MUC4 regulation by K-ras in pancreatic carcinogenesis remains unknown. Using the Pdx1-Cre; LStopL-K-rasG12D mouse model of pancreatic carcinogenesis, we show that the in vivo early neo-expression of the mucin Muc4 in pancreatic intraepithelial neoplastic lesions (PanINs) induced by mutated K-ras is correlated with the activation of ERK, JNK and NF-κB signaling pathways. In vitro, transfection of constitutively activated K-rasG12V in pancreatic cancer cells led to the transcriptional upregulation of MUC4. This activation was found to be mediated at the transcriptional level by AP-1 and NF-κB transcription factors via MAPK, JNK and NF-κB pathways and at the posttranscriptional level by a mechanism involving the RalB GTPase. Altogether, these results identify MUC4 as a transcriptional and post-transcriptional target of K-ras in pancreatic cancer. This opens avenues in developing new approaches to target the early steps of this deadly cancer.
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Affiliation(s)
- Romain Vasseur
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France; Univ Lille Nord de France, 42 rue Paul Duez, F-59000 Lille, France; Centre Hospitalier Régional et Universitaire de Lille, Place de Verdun, 59037 Lille cedex, France
| | - Nicolas Skrypek
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France; Univ Lille Nord de France, 42 rue Paul Duez, F-59000 Lille, France; Centre Hospitalier Régional et Universitaire de Lille, Place de Verdun, 59037 Lille cedex, France
| | - Belinda Duchêne
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France; Univ Lille Nord de France, 42 rue Paul Duez, F-59000 Lille, France; Centre Hospitalier Régional et Universitaire de Lille, Place de Verdun, 59037 Lille cedex, France
| | - Florence Renaud
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France; Univ Lille Nord de France, 42 rue Paul Duez, F-59000 Lille, France; Centre Hospitalier Régional et Universitaire de Lille, Place de Verdun, 59037 Lille cedex, France; Institut de Pathologie, Centre de Biologie Pathologie, Boulevard du Professeur Jules Leclercq, 59037 Lille Cedex, France
| | - Daniel Martínez-Maqueda
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France
| | - Audrey Vincent
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France; Univ Lille Nord de France, 42 rue Paul Duez, F-59000 Lille, France; Centre Hospitalier Régional et Universitaire de Lille, Place de Verdun, 59037 Lille cedex, France
| | - Nicole Porchet
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France; Univ Lille Nord de France, 42 rue Paul Duez, F-59000 Lille, France; Centre Hospitalier Régional et Universitaire de Lille, Place de Verdun, 59037 Lille cedex, France
| | - Isabelle Van Seuningen
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France; Univ Lille Nord de France, 42 rue Paul Duez, F-59000 Lille, France; Centre Hospitalier Régional et Universitaire de Lille, Place de Verdun, 59037 Lille cedex, France
| | - Nicolas Jonckheere
- Inserm, UMR-S 1172, Jean Pierre Aubert Research Center, Team "Mucins, epithelial differentiation and carcinogenesis", 1 rue Polonovski, 59045 Lille cedex, France; Univ Lille Nord de France, 42 rue Paul Duez, F-59000 Lille, France; Centre Hospitalier Régional et Universitaire de Lille, Place de Verdun, 59037 Lille cedex, France
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Cromm PM, Spiegel J, Grossmann TN, Waldmann H. Direkte Modulation von Aktivität und Funktion kleiner GTPasen. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201504357] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Cromm PM, Spiegel J, Grossmann TN, Waldmann H. Direct Modulation of Small GTPase Activity and Function. Angew Chem Int Ed Engl 2015; 54:13516-37. [DOI: 10.1002/anie.201504357] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Indexed: 12/19/2022]
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Tanaka T, Iino M. Sec8 regulates cytokeratin8 phosphorylation and cell migration by controlling the ERK and p38 MAPK signalling pathways. Cell Signal 2015; 27:1110-9. [DOI: 10.1016/j.cellsig.2015.02.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 02/02/2015] [Accepted: 02/16/2015] [Indexed: 12/15/2022]
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Synek L, Sekereš J, Žárský V. The exocyst at the interface between cytoskeleton and membranes in eukaryotic cells. FRONTIERS IN PLANT SCIENCE 2014; 4:543. [PMID: 24427163 PMCID: PMC3877765 DOI: 10.3389/fpls.2013.00543] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 12/12/2013] [Indexed: 05/07/2023]
Abstract
Delivery and final fusion of the secretory vesicles with the relevant target membrane are hierarchically organized and reciprocally interconnected multi-step processes involving not only specific protein-protein interactions, but also specific protein-phospholipid interactions. The exocyst was discovered as a tethering complex mediating initial encounter of arriving exocytic vesicles with the plasma membrane. The exocyst complex is regulated by Rab and Rho small GTPases, resulting in docking of exocytic vesicles to the plasma membrane (PM) and finally their fusion mediated by specific SNARE complexes. In model Opisthokont cells, the exocyst was shown to directly interact with both microtubule and microfilament cytoskeleton and related motor proteins as well as with the PM via phosphatidylinositol 4, 5-bisphosphate specific binding, which directly affects cortical cytoskeleton and PM dynamics. Here we summarize the current knowledge on exocyst-cytoskeleton-PM interactions in order to open a perspective for future research in this area in plant cells.
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Affiliation(s)
- Lukáš Synek
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of the Czech RepublicPrague, Czech Republic
| | - Juraj Sekereš
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of the Czech RepublicPrague, Czech Republic
- Laboratory of Plant Cell Biology, Department of Experimental Plant Biology, Faculty of Science, Charles University in PraguePrague, Czech Republic
| | - Viktor Žárský
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of the Czech RepublicPrague, Czech Republic
- Laboratory of Plant Cell Biology, Department of Experimental Plant Biology, Faculty of Science, Charles University in PraguePrague, Czech Republic
- *Correspondence: Viktor Žárský, Laboratory of Plant Cell Biology, Department of Experimental Plant Biology, Faculty of Science, Charles University in Prague, Vinicna 5, 12844 Prague, Czech Republic e-mail:
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Overexpression of RIN1 associates with tumor grade and progression in patients of bladder urothelial carcinoma. Tumour Biol 2012; 33:847-55. [PMID: 22249975 DOI: 10.1007/s13277-011-0311-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 12/28/2011] [Indexed: 01/07/2023] Open
Abstract
Ras and Rab interactor 1 (RIN1) is an effector of H-Ras, which plays an important role in the development and progression of carcinomas, but it has not been reported in bladder cancer. Hence, the association of RIN1 expression with prognosis of bladder urothelial carcinoma (UC) was examined. RIN1 mRNA and protein expression in 20 paired UCs and the adjacent normal tissues was detected by quantitative reverse transcription polymerase chain reaction and Western blot. The expression of RIN1 protein in 96 specimens of UCs and 22 specimens of adjacent normal bladder tissues were analyzed by immunohistochemistry. The overall survival (OS) was assessed by univariate and multivariate analysis. Moreover, the progression-free survival (PFS) and recurrence-free survival (RFS), classified by the clinicopathologic features with RIN1 expression, were assessed by multivariate analysis. RIN1 mRNA and protein level was higher in UCs than in the adjacent normal tissues (P < 0.01). Enhanced RIN1 immunoexpression was associated with high histologic grades (P = 0.046), cancer progression (P = 0.047) as well as Ki-67 expression (P = 0.023). Furthermore, the 5-year survival rate was 29% in the subgroup with high level of RIN1 expression, while it was 43% in the subgroup with normal level of RIN1 expression (P < 0.05). Importantly, RIN1 level was revealed as the significant independent prognostic factor for death (P = 0.023) and progression (P = 0.003), but a weak contribution for recurrence (P = 0.063). Collectively, RIN1 expression could be a potential prognostic predictor for UC patients.
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Rybko VA, Knizhnik AV, Komelkov AV, Aushev VN, Trukhanova LS, Tchevkina EM. Different metastasis promotive potency of small G-proteins RalA and RalB in in vivo hamster tumor model. Cancer Cell Int 2011; 11:22. [PMID: 21714887 PMCID: PMC3135494 DOI: 10.1186/1475-2867-11-22] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 06/29/2011] [Indexed: 01/28/2023] Open
Abstract
Background Previously we have shown that oncogenic Ha-Ras stimulated in vivo metastasis through RalGEF-Ral signaling. RalA and RalB are highly homologous small G proteins belonging to Ras superfamily. They can be activated by Ras-RalGEF signaling pathway and influence cellular growth and survival, motility, vesicular transport and tumor progression in humans and in animal models. Here we first time compared the influence of RalA and RalB on tumorigenic, invasive and metastatic properties of RSV transformed hamster fibroblasts. Methods Retroviral vectors encoding activated forms or effector mutants of RalA or RalB proteins were introduced into the low metastatic HET-SR cell line. Tumor growth and spontaneous metastatic activity (SMA) were evaluated on immunocompetent hamsters after subcutaneous injection of cells. The biological properties of cells, including proliferation, clonogenicity, migration and invasion were determined using MTT, wound healing, colony formation and Boyden chamber assays respectively. Protein expression and phosphorylation was detected by Westen blot analysis. Extracellular proteinases activity was assessed by substrate-specific zymography. Results We have showed that although both Ral proteins stimulated SMA, RalB was more effective in metastasis stimulation in vivo as well as in potentiating of directed movement and invasion in vitro. Simultaneous expression of active RalA and RalB didn't give synergetic effect on metastasis formation. RalB activity decreased expression of Caveolin-1, while active RalA stimulated MMP-1 and uPA proteolytic activity, as well as CD24 expression. Both Ral proteins were capable of Cyclin D1 upregulation, JNK1 kinase activation, and stimulation of colony growth and motility. Among three main RalB effectors (RalBP1, exocyst complex and PLD1), PLD1 was essential for RalB-dependent metastasis stimulation. Conclusions Presented results are the first data on direct comparison of RalA and RalB impact as well as of RalA/RalB simultaneous expression influence on in vivo cell metastatic activity. We showed that RalB activation significantly more than RalA stimulates SMA. This property correlates with the ability of RalB to stimulate in vitro invasion and serum directed cell movement. We also found that RalB-PLD1 interaction is necessary for the acquisition of RalB-dependent high metastatic cell phenotype. These findings contribute to the identification of molecular mechanisms of metastasis and tumor progression.
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Affiliation(s)
- Vera A Rybko
- Department of Oncogenes Regulation, Institute of Carcinogenesis, Russian N,N, Blokhin Cancer Research Center, Kashirskoye shosse 24, 115478, Moscow, Russia.
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Shirai Y, Morioka S, Sakuma M, Yoshino KI, Otsuji C, Sakai N, Kashiwagi K, Chida K, Shirakawa R, Horiuchi H, Nishigori C, Ueyama T, Saito N. Direct binding of RalA to PKCη and its crucial role in morphological change during keratinocyte differentiation. Mol Biol Cell 2011; 22:1340-52. [PMID: 21346190 PMCID: PMC3078077 DOI: 10.1091/mbc.e10-09-0754] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
A small G protein, RalA, was identified as a binding partner of PKCη. The binding led to activation of RalA and actin depolymerization associated with keratinocyte differentiation. These results provide new insight into the molecular mechanism of cytoskeletal regulation that leads to drastic change of cell shape. During differentiation, keratinocytes undergo a dramatic shape change from small and round to large and flat, in addition to production of proteins necessary for the formation of epidermis. It has been shown that protein kinase C (PKC) η is crucial for keratinocyte differentiation. However, its role in this process has yet to be fully elucidated. Here, we show that catalytic activity is not necessary for enlarged and flattened morphology of human keratinocytes induced by overexpression of PKCη, although it is important for gene expression of the marker proteins. In addition, we identify the small G protein RalA as a binding partner of PKCη, which binds to the C1 domain, an indispensable region for the morphological change. The binding led activation of RalA and actin depolymerization associated with keratinocyte differentiation. siRNA techniques proved that RalA is involved in not only the keratinocyte differentiation induced by PKCη overexpression but also normal keratinocyte differentiation induced by calcium and cholesterol sulfate. These results provide a new insight into the molecular mechanism of cytoskeletal regulation leading to drastic change of cell shape.
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Affiliation(s)
- Yasuhito Shirai
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe 657-8501, Japan.
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Overmeyer JH, Maltese WA. Death pathways triggered by activated Ras in cancer cells. Front Biosci (Landmark Ed) 2011; 16:1693-713. [PMID: 21196257 DOI: 10.2741/3814] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ras GTPases are best known for their ability to serve as molecular switches regulating cell growth, differentiation and survival. Gene mutations that result in expression of constitutively active forms of Ras have been linked to oncogenesis in animal models and humans. However, over the past two decades, evidence has gradually accumulated to support a paradoxical role for Ras proteins in the initiation of cell death pathways. In this review we survey the literature pointing to the ability of activated Ras to promote cell death under conditions where cancer cells encounter apoptotic stimuli or Ras is ectopically expressed. In some of these cases Ras acts through known effectors and well defined apoptotic death pathways. However, in other cases it appears that Ras operates by triggering novel non-apoptotic death mechanisms that are just beginning to be characterized. Understanding these mechanisms and the factors that go into changing the nature of Ras signaling from pro-survival to pro-death could set the stage for development of novel therapeutic approaches aimed at manipulating pro-death Ras signaling pathways in cancer.
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Affiliation(s)
- Jean H Overmeyer
- Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio 43614, USA
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Wang H, Owens C, Chandra N, Conaway MR, Brautigan DL, Theodorescu D. Phosphorylation of RalB is important for bladder cancer cell growth and metastasis. Cancer Res 2010; 70:8760-9. [PMID: 20940393 DOI: 10.1158/0008-5472.can-10-0952] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
RalA and RalB are monomeric G proteins that are 83% identical in amino acid sequence but have paralogue-specific effects on cell proliferation, metastasis, and apoptosis. Using in vitro kinase assays and phosphosite-specific antibodies, here we show phosphorylation of RalB by protein kinase C (PKC) and RalA by protein kinase A. We used mass spectrometry and site-directed mutagenesis to identify S198 as the primary PKC phosphorylation site in RalB. Phorbol ester [phorbol 12-myristate 13-acetate (PMA)] treatment of human bladder carcinoma cells induced S198 phosphorylation of stably expressed FLAG-RalB as well as endogenous RalB. PMA treatment caused RalB translocation from the plasma membrane to perinuclear regions in a S198 phosphorylation-dependent manner. Using RNA interference depletion of RalB followed by rescue with wild-type RalB or RalB(S198A) as well as overexpression of wild-type RalB or RalB(S198A) with and without PMA stimulation, we show that phosphorylation of RalB at S198 is necessary for actin cytoskeletal organization, anchorage-independent growth, cell migration, and experimental lung metastasis of T24 or UMUC3 human bladder cancer cells. In addition, UMUC3 cells transfected with a constitutively active RalB(G23V) exhibited enhanced subcutaneous tumor growth, whereas those transfected with phospho-deficient RalB(G23V-S198A) were indistinguishable from control cells. Our data show that RalA and RalB are phosphorylated by different kinases, and RalB phosphorylation is necessary for in vitro cellular functions and in vivo tumor growth and metastasis.
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Affiliation(s)
- Hong Wang
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia, USA
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Kidd AR, Snider JL, Martin TD, Graboski SF, Der CJ, Cox AD. Ras-related small GTPases RalA and RalB regulate cellular survival after ionizing radiation. Int J Radiat Oncol Biol Phys 2010; 78:205-12. [PMID: 20619549 DOI: 10.1016/j.ijrobp.2010.03.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 03/05/2010] [Accepted: 03/10/2010] [Indexed: 01/25/2023]
Abstract
PURPOSE Oncogenic activation of Ras renders cancer cells resistant to ionizing radiation (IR), but the mechanisms have not been fully characterized. The Ras-like small GTPases RalA and RalB are downstream effectors of Ras function and are critical for both tumor growth and survival. The Ral effector RalBP1/RLIP76 mediates survival of mice after whole-body irradiation, but the role of the Ral GTPases themselves in response to IR is unknown. We have investigated the role of RalA and RalB in cellular responses to IR. METHODS AND MATERIALS RalA, RalB, and their major effectors RalBP1 and Sec5 were knocked down by stable expression of short hairpin RNAs in the K-Ras-dependent pancreatic cancer-derived cell line MIA PaCa-2. Radiation responses were measured by standard clonogenic survival assays for reproductive survival, gammaH2AX expression for double-strand DNA breaks (DSBs), and poly(ADP-ribose)polymerase (PARP) cleavage for apoptosis. RESULTS Knockdown of K-Ras, RalA, or RalB reduced colony-forming ability post-IR, and knockdown of either Ral isoform decreased the rate of DSB repair post-IR. However, knockdown of RalB, but not RalA, increased cell death. Surprisingly, neither RalBP1 nor Sec5 suppression affected colony formation post-IR. CONCLUSIONS Both RalA and RalB contribute to K-Ras-dependent IR resistance of MIA PaCa-2 cells. Sensitization due to suppressed Ral expression is likely due in part to decreased efficiency of DNA repair (RalA and RalB) and increased susceptibility to apoptosis (RalB). Ral-mediated radioresistance does not depend on either the RalBP1 or the exocyst complex, the two best-characterized Ral effectors, and instead may utilize an atypical or novel effector.
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Affiliation(s)
- Ambrose R Kidd
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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Abstract
The genes encoding the Ras family of small GTPases are mutated to yield constitutively active GTP-bound oncogenic proteins in one third of all human cancers. Oncogenic Ras binds to and activates a number of proteins that promote tumorigenic phenotypes, including the family of Ral guanine nucleotide exchange factors (RalGEF). Activated RalGEFs convert the Ral family of small GTPases, composed of RalA and RalB, from an inactive GDP-bound state to an active GTP-bound state. As both RalA and RalB have been implicated in a variety of tumorigenic phenotypes, we sought to determine which proteins downstream of Rals promote transformation and tumorigenesis. Here, we report that shRNA-mediated knockdown of the Ral effector proteins Sec5 and Exo84, but less so in the case of RalBP1, reduced oncogenic RalGEF-mediated transformation and oncogenic Ras-driven tumorigenic growth of human cells. These results suggest that Rals promote oncogenic Ras-mediated tumorigenesis through, at least in part, Sec5 and Exo84.
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Affiliation(s)
- Sameer H Issaq
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, DUMC-3813, Durham, NC 27710, USA
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Wang K, Chen Y, Liu S, Qiu S, Gao S, Huang X, Zhang J, Peng X, Qiani W, Zhang JY. Immunogenicity of Ra1A and its tissue-specific expression in hepatocellular carcinoma. Int J Immunopathol Pharmacol 2009; 22:735-43. [PMID: 19822090 DOI: 10.1177/039463200902200319] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
In order to understand the immunogenicity of a tumor-associated antigen (TAA), Ras family small GTP binding protein (Ra1A) in hepatocellular carcinoma (HCC), autoantibody responses to RalA were evaluated by enzyme-linked immunosorbent assay (ELISA), Western blotting and indirect immunofluorescence assay in sera from patients with HCC and sera from normal individuals. Immunohistochemistry (IHC) study with tissue array slides was also performed to analyze protein expression profiles of RalA in HCC and control tissues. This study demonstrated that RalA had a relative higher frequency of autoantibody response in HCC (20.1%) compared to liver cirrhosis (3.3%), chronic hepatitis (0%), and normal individuals sera (0%). RalA also showed a stepwise increased expression from normal liver tissues (26.7%), liver cirrhosis tissues (45.0%) to HCC tissues (63.3%). Sensitivity and specificity of anti-RalA antibody in detection of HCC was 20.1% and 99.3%, respectively. The data suggested that RalA might contribute to liver malignant transformation, and could be used as a potential tumor marker in HCC detection.
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Affiliation(s)
- K Wang
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, Texas 79968, USA
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The GTPase RalA regulates different steps of the secretory process in pancreatic beta-cells. PLoS One 2009; 4:e7770. [PMID: 19890390 PMCID: PMC2766836 DOI: 10.1371/journal.pone.0007770] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Accepted: 10/11/2009] [Indexed: 12/25/2022] Open
Abstract
Background RalA and RalB are multifuntional GTPases involved in a variety of cellular processes including proliferation, oncogenic transformation and membrane trafficking. Here we investigated the mechanisms leading to activation of Ral proteins in pancreatic β-cells and analyzed the impact on different steps of the insulin-secretory process. Methodology/Principal Findings We found that RalA is the predominant isoform expressed in pancreatic islets and insulin-secreting cell lines. Silencing of this GTPase in INS-1E cells by RNA interference led to a decrease in secretagogue-induced insulin release. Real-time measurements by fluorescence resonance energy transfer revealed that RalA activation in response to secretagogues occurs within 3–5 min and reaches a plateau after 10–15 min. The activation of the GTPase is triggered by increases in intracellular Ca2+ and cAMP and is prevented by the L-type voltage-gated Ca2+ channel blocker Nifedipine and by the protein kinase A inhibitor H89. Defective insulin release in cells lacking RalA is associated with a decrease in the secretory granules docked at the plasma membrane detected by Total Internal Reflection Fluorescence microscopy and with a strong impairment in Phospholipase D1 activation in response to secretagogues. RalA was found to be activated by RalGDS and to be severely hampered upon silencing of this GDP/GTP exchange factor. Accordingly, INS-1E cells lacking RalGDS displayed a reduction in hormone secretion induced by secretagogues and in the number of insulin-containing granules docked at the plasma membrane. Conclusions/Significance Taken together, our data indicate that RalA activation elicited by the exchange factor RalGDS in response to a rise in intracellular Ca2+ and cAMP controls hormone release from pancreatic β-cell by coordinating the execution of different events in the secretory pathway.
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Abstract
The Ras superfamily of GTP-binding proteins is involved in many cellular processes, including cell proliferation, movement, and morphology. One such member, Ral GTPase, activates downstream signaling molecules after a conversion to the active state on GTP binding. The RalGDS-related (Rgr) oncogene belongs to the RalGDS family of guanine nucleotide exchange factors (GEFs). RalGEFs activate Ral by stimulating the dissociation of GDP, allowing the binding of GTP and the initiation of downstream signaling events by Ral effectors. Rgr was first identified as a fusion between the rabbit homolog of the Rad 23 gene and the Rgr gene in a rabbit squamous cell carcinoma. The Rgr portion of the fusion was demonstrated to contain the oncogenic activity. The human form of the Rgr oncogene was identified recently, and expression was detected in human T-cell malignancies. This chapter describes the analysis of rabbit and human Rgr function using various methods. These assays may be used for the study of oncogene function in other systems.
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Affiliation(s)
- Laura A Martello
- Department of Pathology, New York Cancer Institute, New York University School of Medicine, New York, New York, USA
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Abstract
A confluence of recent observations has indicted the Ras-family G-proteins RALA and RALB as key offenders in the subversion of core biological systems driving oncogenic transformation. Here, we will focus on current developments highlighting the pivotal contribution of Ral proteins to the regulatory framework supporting tumorigenesis, and evaluate mechanistic connections between Ral effector activation and generation of this framework.
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Affiliation(s)
- Brian O Bodemann
- Department of Cell Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA
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Ceriani M, Scandiuzzi C, Amigoni L, Tisi R, Berruti G, Martegani E. Functional analysis of RalGPS2, a murine guanine nucleotide exchange factor for RalA GTPase. Exp Cell Res 2007; 313:2293-307. [PMID: 17462626 DOI: 10.1016/j.yexcr.2007.03.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 03/14/2007] [Accepted: 03/18/2007] [Indexed: 11/28/2022]
Abstract
RalGPS2 is a murine guanine nucleotide exchange factor of the RalGPS family; it contains a Cdc25-like GEF domain and does not exhibit a Ras-binding domain. The main characteristic of RalGPS2 is its pleckstrin homology (PH) domain, present at the C terminus, that preferentially binds phosphatidylinositol-4,5-biphosphate and in HEK 293 cells localized in membranes, causing ruffling and vesiculation. Moreover, RalGPS2 contains a PxxP motif in the central part of the molecule. This motif binds in vitro and in vivo SH3 domains of Grb2 and PLCgamma. RalGPS2 and its GEF domain activate RalA in vivo while the PH-PxxP domains inhibited it behaving as a dominant negative for the RalA pathway; this activation was not inhibited by co-expression of a dominant negative Ras. RalGPS2 is physiologically expressed in testis and brain; when overexpressed, the whole RalGPS2 causes considerable morphological changes in HEK 293 cells, suggesting its possible role on cytoskeleton reorganization. This is further strengthened by data obtained in NIH3T3 cells where expression of PH-PxxP domain promotes actin depolymerization. Finally, RalGPS2 and its GEF domain induce Ras-independent transcriptional activation of the c-fos promoter in NIH3T3 cells.
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Affiliation(s)
- Michela Ceriani
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, Milan, Italy
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Xu J, Shi S, Matsumoto N, Noda M, Kitayama H. Identification of Rgl3 as a potential binding partner for Rap-family small G-proteins and profilin II. Cell Signal 2007; 19:1575-82. [PMID: 17382517 DOI: 10.1016/j.cellsig.2007.02.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2007] [Revised: 02/07/2007] [Accepted: 02/07/2007] [Indexed: 11/20/2022]
Abstract
A cDNA encoding a RalGDS-related protein, Rgl3, was isolated by yeast two-hybrid screening using a small G-protein, Rap1, as a bait. Rgl3 mRNA is commonly detectable in several visceral organs (e.g. kidney, heart, liver, and lung) in the mouse and human. The Rgl3 protein mainly localizes in the cytoplasm when expressed in fibroblasts. Yeast two-hybrid assay indicated that Rgl3 could interact with Rap1, Rap2, H-Ras, N-Ras, and R-Ras but failed to interact efficiently with Ral and Rho. Interestingly, Rgl3 was found to affect cell morphology in two assay systems in culture. First, Rgl3 suppressed cell-spreading induced by Rap1, R-Ras, or C3G-CAAX (a membrane-targeted Rap/R-Ras activator) in HEK-293 cells. Second, Rgl3 enhanced the focus-formation induced by oncogenic H-Ras and N-Ras mutants in NIH3T3 cells. Moreover, we identified profilin II as a potential binding partner for Rgl3 by yeast two-hybrid screening. This interaction requires the characteristic proline cluster in the Rgl3 amino-terminal domain. Profilin II and Rgl3 co-operated in enhancing the N-Ras-induced focus-formation. These findings raise the possibility that Rgl3 mediates interaction between Ras/Rap-family proteins and profilin II, an important activator of actin polymerization.
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Affiliation(s)
- Jiegou Xu
- Department of Molecular Oncology, Kyoto University Graduate School of Medicine, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501 Japan
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Yoshizaki H, Mochizuki N, Gotoh Y, Matsuda M. Akt-PDK1 complex mediates epidermal growth factor-induced membrane protrusion through Ral activation. Mol Biol Cell 2007; 18:119-28. [PMID: 17079732 PMCID: PMC1751317 DOI: 10.1091/mbc.e06-05-0467] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 10/16/2006] [Accepted: 10/19/2006] [Indexed: 11/11/2022] Open
Abstract
We studied the spatiotemporal regulation of Akt (also called protein kinase B), phosphatidylinositol-3,4-bisphosphate [PtdIns(3,4)P2], and phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P3] by using probes based on the principle of fluorescence resonance energy transfer. On epidermal growth factor (EGF) stimulation, the amount of PtdIns(3,4,5)P3 was increased diffusely in the plasma membrane, whereas that of PtdIns(3,4)P2 was increased more in the nascent lamellipodia than in the plasma membrane of the central region. The distribution and time course of Akt activation were similar to that of increased PtdIns(3,4)P2 levels, which were most prominent in the nascent lamellipodia. Moreover, we found that upon EGF stimulation 3-phosphoinositide-dependent protein kinase-1 (PDK1) was also recruited to nascent lamellipodia in an Akt-dependent manner. Because PDK1 is known to activate Ral GTPase and because Ral is required for EGF-induced lamellipodial protrusion, we speculated that the PDK1-Akt complex may be indispensable for the induction of lamellipodia. In agreement with this idea, EGF-induced lamellipodia formation was promoted by the overexpression of Akt and inhibited by an Akt inhibitor or a Ral-binding domain of Sec5. These results identified the Akt-PDK1 complex as an upstream positive regulator of Ral GTPase in the induction of lamellipodial protrusion.
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Affiliation(s)
- Hisayoshi Yoshizaki
- *Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan; and
| | - Naoki Mochizuki
- *Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
| | - Yukiko Gotoh
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Michiyuki Matsuda
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan; and
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Vogelsgesang M, Pautsch A, Aktories K. C3 exoenzymes, novel insights into structure and action of Rho-ADP-ribosylating toxins. Naunyn Schmiedebergs Arch Pharmacol 2006; 374:347-60. [PMID: 17146673 DOI: 10.1007/s00210-006-0113-y] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 10/18/2006] [Indexed: 12/19/2022]
Abstract
The family of C3-like exoenzymes comprises seven bacterial ADP-ribosyltransferases of different origin. The common hallmark of these exoenzymes is the selective N-ADP-ribosylation of the low molecular mass GTP-binding proteins RhoA, B, and C and inhibition of signal pathways controlled by Rho GTPases. Therefore, C3-like exoenzymes were applied as pharmacological tools for analyses of cellular functions of Rho protein in numerous studies. Recent structural and functional analyses of C3-like exoenzymes provide detailed information on the molecular mechanisms and functional consequences of ADP-ribosylation catalyzed by these toxins. More recently additional non-enzymatic actions of C3-like ADP-ribosyltransferases have been identified showing that C3 transferases from Clostridium botulinum and Clostridium limosum form a GDI-like complex with the Ras-like low molecular mass GTPase Ral without ADP-ribosylation. These results add novel information on the molecular mode of action(s) of C3-like exoenzymes and are discussed in this review.
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Affiliation(s)
- Martin Vogelsgesang
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-University Freiburg, Otto-Krayer-Haus, Albertstrasse 25, Freiburg, Germany
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Young TW, Mei FC, Rosen DG, Yang G, Li N, Liu J, Cheng X. Up-regulation of tumor susceptibility gene 101 protein in ovarian carcinomas revealed by proteomics analyses. Mol Cell Proteomics 2006; 6:294-304. [PMID: 17110434 DOI: 10.1074/mcp.m600305-mcp200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Small GTPase RAS plays a critical role in cellular signaling and oncogenic transformation. Proteomics analysis of genetically defined human ovarian cancer models identified the tumor susceptibility gene 101 (TSG101) as a downstream target of RAS oncogene. Mechanistic studies revealed a novel post-translational regulation of TSG101 through the RAS/RAF/MEK/MAPK signaling pathway and downstream molecules p14(ARF)/HDM2. Immunoanalysis using ovarian cancer samples and microtissue array revealed elevated TSG101 levels in human ovarian carcinomas. Silencing of TSG101 by short interfering RNA in ovarian cancer cells led to growth inhibition and cell death. Concurrent with the apparent growth-inhibitory effect, the levels of the CBP/p300-interacting transactivator with ED-rich tail 2 (CITED2) and hypoxia-inducible factor 1alpha (HIF-1alpha), as well as its cellular activity, were markedly reduced after TSG101 knockdown. These results demonstrate that TSG101 is important for CITED2- and HIF-1alpha-mediated cellular regulation in ovarian carcinomas.
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Affiliation(s)
- Travis W Young
- Department of Pharmacology and Toxicology, Sealy Center for Cancer Cell Biology, School of Medicine, The University of Texas Medical Branch, Galveston, Texas 77555, USA
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Lad Y, McHugh B, Hodkinson PS, Mackinnon AC, Haslett C, Ginsberg MH, Sethi T. Phospholipase C epsilon suppresses integrin activation. J Biol Chem 2006; 281:29501-12. [PMID: 16895916 DOI: 10.1074/jbc.m513471200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholipase Cepsilon (PLCepsilon) is a newly described effector of the small GTP-binding protein H-Ras. Utilizing H-Ras effector mutants, we show that mutants H-Ras(G12V/E37G) and H-Ras(G12V/D38N) suppressed integrin activation in an ERK-independent manner. H-Ras(G12V/D38N) specifically activated the PLCepsilon effector pathway and suppressed integrin activation. Inhibition of PLCepsilon activation with a kinase-dead PLCepsilon mutant prevented H-Ras(G12V/D38N) from suppressing integrin activation, and low level expression of H-Ras(G12V/D38N) could synergize with wild-type PLCepsilon to suppress integrins. In addition, knockdown of endogenous PLCepsilon with small interfering RNA blocked H-Ras(G12V/D38N)-mediated integrin suppression. Suppressing integrin function with the H-Ras(G12V/D38N) mutant reduced cell adhesion to von Willebrand factor and fibronectin; this reduction in cell adhesion was blocked by coexpression of the kinase-dead PLCepsilon mutant. These results show that H-Ras suppresses integrin affinity via independent Raf and PLCepsilon signaling pathways and demonstrate a new physiological function for PLCepsilon in the regulation of integrin activation.
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Affiliation(s)
- Yatish Lad
- Medical Research Council Centre for Inflammation Research, Queen's Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom
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Shi J, Badri KR, Choudhury R, Schuger L. P311-induced myofibroblasts exhibit ameboid-like migration through RalA activation. Exp Cell Res 2006; 312:3432-42. [PMID: 16934802 DOI: 10.1016/j.yexcr.2006.07.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Revised: 07/14/2006] [Accepted: 07/18/2006] [Indexed: 11/16/2022]
Abstract
We previously showed that P311, an intracellular protein involved in cell migration, is found in human wound myofibroblast precursors (proto-myofibroblasts) and myofibroblasts. Furthermore, by binding to the TGF-beta1 latency associated protein (LAP), P311 induced NIH 3T3 cells to transform into non-fibrogenic myofibroblasts characterized by lack of TGF-beta1 production. Here we demonstrate that P311-induced myofibroblasts migrate in an ameboid rather than a mesenchymal pattern. Ameboid migration is characterized by lack of focal adhesions and stress fibers, absence of integrins and MMPs clustering/activation and changes in small GTPases activity, all leading to increased cell motility. P311-induced ameboid migration depended on activation of the GTPase RalA and was reverted to mesenchymal-type migration by RalA RNA interference. Ameboid migration was conserved in cells plated on fibrin, the initial wound matrix, but was switched back to mesenchymal-type migration by collagen I, the main ECM component in late stages of wound healing. TGF-beta1, the major stimulus of collagen production during wound repair, also reversed the ameboid phenotype to mesenchymal. Our studies therefore suggest that, by inducing RalA activity, P311 promotes a motile proto-myofibroblast and myofibroblast phenotype specifically adapted to rapidly populate the initial wound matrix.
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Affiliation(s)
- Jinghua Shi
- Department of Pathology, Wayne State University, School of Medicine, Detroit, MI 48201, USA
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Abstract
Among the effector molecules connected with the group of cell surface receptors, Ras proteins have essential roles in transducing extracellular signals to diverse intracellular events, by controlling the activities of multiple signaling pathways. For over 20 years since the discovery of Ras proteins, an enormous amount of knowledge has been accumulated as to how the proteins function in overlapping or distinct fashions. The signaling networks they regulate are very complex due to their multiple functions and cross-talks. Much attention has been paid to the pathological role of Ras in tumorigenesis. In particular, human tumors very frequently express Ras proteins constitutively activated by point mutations. Up to date, three members of the Ras family have been identified, namely H-Ras, K-Ras (A and B), and N-Ras. Although these Ras isoforms function in similar ways, many evidences also support the distinct molecular function of each Ras protein. This review summarizes differential functions of Ras and highlights the current view of the distinct signaling network regulated by each Ras for its contribution to the malignant phenotypic conversion of breast epithelial cells. Four issues are addressed in this review: (1) Ras proteins, (2) membrane localization of Ras, (3) effector molecules downstream of Ras, (4) Ras signaling in invasion. In spite of the accumulation of information on the differential functions of Ras, much more remains to be elucidated to understand the Ras-mediated molecular events of malignant phenotypic conversion of cells in a greater detail.
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Affiliation(s)
- Aree Moon
- College of Pharmacy, Duksung Women's University, Seoul 132-714, Korea.
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Omidvar N, Pearn L, Burnett AK, Darley RL. Ral is both necessary and sufficient for the inhibition of myeloid differentiation mediated by Ras. Mol Cell Biol 2006; 26:3966-75. [PMID: 16648489 PMCID: PMC1489015 DOI: 10.1128/mcb.26.10.3966-3975.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hyperactivation of Ras is one of the most common abnormalities in acute myeloid leukemia. In experimental models, Ras inhibits myeloid differentiation, which is characteristic of leukemia; however, the mechanism through which it disrupts hematopoiesis is poorly understood. In multipotent FDCP-mix cells, Ras inhibits terminal neutrophil differentiation, thereby indefinitely extending their proliferative potential. Ras also strongly promotes the sensitivity of these cells to granulocyte-macrophage colony-stimulating factor (GM-CSF). Using this model, we have dissected the signaling elements downstream of Ras to determine their relative contribution to the dysregulation of hematopoiesis. Cells expressing Ras mutants selectively activating Raf (Ras*T35S) or phosphatidylinositol 3-kinase (Ras*Y40C) did not significantly affect differentiation or proliferative capacity, whereas Ras*E37G (which selectively activates RalGEFs) perpetuated proliferation and blocked neutrophil development in a manner similar to that of Ras. Correspondingly, expression of constitutively active versions of these effectors confirmed the overriding importance of Ral guanine nucleotide exchange factors. Cells expressing Ras demonstrated hyperactivation of Ral, which itself was able to exactly mimic the phenotype of Ras, including hypersensitivity to GM-CSF. Conversely, dominant negative Ral promoted spontaneous neutrophil development. Ral, in turn, appears to influence differentiation through multiple effectors. These data show, for the first time, the importance of Ral in regulating differentiation and self-renewal in hematopoietic cells.
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Affiliation(s)
- Nader Omidvar
- Department of Haematology, School of Medicine, Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff, United Kingdom.
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Noda Y, Sasaki S. Regulation of aquaporin-2 trafficking and its binding protein complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1117-25. [PMID: 16624255 DOI: 10.1016/j.bbamem.2006.03.004] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Revised: 02/14/2006] [Accepted: 03/07/2006] [Indexed: 12/19/2022]
Abstract
Trafficking of water channel aquaporin-2 (AQP2) to the apical membrane is critical to water reabsorption in renal collecting ducts and its regulation maintains body water homeostasis. However, exact molecular mechanisms which recruit AQP2 are unknown. Recent studies highlighted a key role for spatial and temporal regulation of actin dynamics in AQP2 trafficking. We have recently identified AQP2-binding proteins which directly regulate this trafficking: SPA-1, a GTPase-activating protein (GAP) for Rap1, and cytoskeletal protein actin. In addition, a multiprotein "force generator" complex which directly binds to AQP2 has been discovered. This review summarizes recent advances related to the mechanism for AQP2 trafficking.
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Affiliation(s)
- Yumi Noda
- Department of Nephrology, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Tokyo 113-8519, Japan.
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41
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Pautsch A, Vogelsgesang M, Tränkle J, Herrmann C, Aktories K. Crystal structure of the C3bot-RalA complex reveals a novel type of action of a bacterial exoenzyme. EMBO J 2005; 24:3670-80. [PMID: 16177825 PMCID: PMC1276701 DOI: 10.1038/sj.emboj.7600813] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Accepted: 08/22/2005] [Indexed: 12/21/2022] Open
Abstract
C3 exoenzymes from bacterial pathogens ADP-ribosylate and inactivate low-molecular-mass GTPases of the Rho subfamily. Ral, a Ras subfamily GTPase, binds the C3 exoenzymes from Clostridium botulinum and C. limosum with high affinity without being a substrate for ADP ribosylation. In the complex, the ADP-ribosyltransferase activity of C3 is blocked, while binding of NAD and NAD-glycohydrolase activity remain. Here we report the crystal structure of C3 from C. botulinum in a complex with GDP-bound RalA at 1.8 A resolution. C3 binds RalA with a helix-loop-helix motif that is adjacent to the active site. A quaternary complex with NAD suggests a mode for ADP-ribosyltransferase inhibition. Interaction of C3 with RalA occurs at a unique interface formed by the switch-II region, helix alpha3 and the P loop of the GTPase. C3-binding stabilizes the GDP-bound conformation of RalA and blocks nucleotide release. Our data indicate that C. botulinum exoenzyme C3 is a single-domain toxin with bifunctional properties targeting Rho GTPases by ADP ribosylation and Ral by a guanine nucleotide dissociation inhibitor-like effect, which blocks nucleotide exchange.
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Affiliation(s)
- Alexander Pautsch
- Structural Research, Department of Integrated Lead Discovery, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
| | - Martin Vogelsgesang
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie der Universität Freiburg, Otto-Krayer-Haus, Freiburg, Germany
| | - Jens Tränkle
- Physikalische Chemie I, Ruhr-Universität Bochum, Bochum, Germany
| | | | - Klaus Aktories
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie der Universität Freiburg, Otto-Krayer-Haus, Freiburg, Germany
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie der Universität Freiburg, Otto-Krayer-Haus, Albertstrasse 25, 79104 Freiburg, Germany. Tel.: +49 761 203 5301; Fax: +49 761 203 5311; E-mail:
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Ryu CH, Kim SW, Lee KH, Lee JY, Kim H, Lee WK, Choi BH, Lim Y, Kim YH, Lee KH, Hwang TK, Jun TY, Rha HK. The merlin tumor suppressor interacts with Ral guanine nucleotide dissociation stimulator and inhibits its activity. Oncogene 2005; 24:5355-64. [PMID: 16007223 DOI: 10.1038/sj.onc.1208633] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Neurofibromatosis type 2 (NF2) is the most commonly mutated gene in benign tumors of the human nervous system such as schwannomas and meningiomas. The NF2 gene encodes a protein called schwannomin or merlin, which is involved in regulating cell growth and proliferation through protein-protein interactions with various cellular proteins. In order to better understand the mechanism by which merlin exerts its function, yeast two-hybrid screening was performed and Ral guanine nucleotide dissociation stimulator (RalGDS), a downstream molecule of Ras, was identified as a merlin-binding protein. The direct interaction between merlin and RalGDS was confirmed both in vitro and in the NIH3T3 cells. The domain analyses revealed that the broad C-terminal region of merlin (aa 141-595) is necessary for the interaction with the C-terminal Ras-binding domain (RBD) of RalGDS. Functional studies showed that merlin inhibits the RalGDS-induced RalA activation, the colony formation and the cell migration in mammalian cells. These results suggest that merlin can function as a tumor suppressor by inhibiting the RalGDS-mediated oncogenic signals.
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Affiliation(s)
- Chung Hun Ryu
- Catholic Neuroscience Center, The Catholic University of Korea, Seoul 137-701, Korea
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Gomez GA, Daniotti JL. H-Ras dynamically interacts with recycling endosomes in CHO-K1 cells: involvement of Rab5 and Rab11 in the trafficking of H-Ras to this pericentriolar endocytic compartment. J Biol Chem 2005; 280:34997-5010. [PMID: 16079139 DOI: 10.1074/jbc.m506256200] [Citation(s) in RCA: 54] [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
H-, N-, and K-Ras are isoforms of Ras proteins, which undergo different lipid modifications at the C terminus. These post-translational events make possible the association of Ras proteins both with the inner plasma membrane and to the cytosolic surface of endoplasmic reticulum and Golgi complex, which is also required for the proper function of these proteins. To better characterize the intracellular distribution and sorting of Ras proteins, constructs were engineered to express the C-terminal domain of H- and K-Ras fused to variants of green fluorescent protein. Using confocal microscopy, we found in CHO-K1 cells that H-Ras, which is palmitoylated and farnesylated, localized at the recycling endosome in addition to the inner leaflet of the plasma membrane. In contrast, K-Ras, which is farnesylated and nonpalmitoylated, mainly localized at the plasma membrane. Moreover, we demonstrate that sorting signals of H- and K-Ras are contained within the C-terminal domain of these proteins and that palmitoylation on this region of H-Ras might operate as a dominant sorting signal for proper subcellular localization of this protein in CHO-K1 cells. Using selective photobleaching techniques, we demonstrate the dynamic nature of H-Ras trafficking to the recycling endosome from plasma membrane. We also provide evidence that Rab5 and Rab11 activities are required for proper delivery of H-Ras to the endocytic recycling compartment. Using a chimera containing the Ras binding domain of c-Raf-1 fused to a fluorescent protein, we found that a pool of GTP-bound H-Ras localized on membranes from Rab11-positive recycling endosome after serum stimulation. These results suggest that H-Ras present in membranes of the recycling endosome might be activating signal cascades essential for the dynamic and function of the organelle.
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Affiliation(s)
- Guillermo Alberto Gomez
- Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC (UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba 5000, Argentina
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Abstract
Prostate cancer is the most frequently diagnosed cancer among men and the second leading cause of male cancer deaths in the United States. When prostate cancer initially presents in the clinic, the tumour is dependent on androgen for growth and, therefore, responsive to the surgical or pharmacological ablation of circulating androgens. However, there is a high rate of treatment failure because the disease often recurs as androgen-independent metastases. Surprisingly, this late-stage androgen-independent prostate cancer almost always retains expression of the AR (androgen receptor), despite the near absence of circulating androgens. Although late-stage prostate cancer is androgen-independent, the AR still seems to play a role in cancer cell growth at this stage of disease. Therefore a key to understanding hormone-independent prostate cancer is to determine the mechanism(s) by which the AR can function even in the absence of physiological levels of circulating androgen. This review will focus on the role of growth factor signalling in prostate cancer progression to androgen independence and thus outline potential molecular areas of intervention to treat prostate cancer progression.
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Affiliation(s)
- Daniel Gioeli
- Department of Microbiology, University of Virginia Health System, PO Box 800734, Charlottesville, VA 22908, U.S.A.
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Ishido M, Masuo Y. Transcriptome of pituitary adenylate cyclase-activating polypeptide-differentiated PC12 cells. ACTA ACUST UNITED AC 2005; 123:15-21. [PMID: 15518888 DOI: 10.1016/j.regpep.2004.05.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Addition of pituitary adenylate cyclase-activating polypeptide (PACAP) into the cultured PC12 cells secreted dopamine and promoted neurite outgrowth of the cells, indicating cell differentiation. To characterize the PACAP-differentiated PC12 cell transcriptome, we applied DNA macroarray techniques, using Atlas Rat 1.2 Array membranes (BD Biosciences Clontech) that have 1176 cDNA. RNA samples were harvested from PC12 cells before and at a time of 6 h treatment with 1 nM PACAP, when neuritogenesis was remarkably observed under the condition used. Several genes regulated by PACAP have been associated with neuritogenesis (i.e. villin 2 and tissue plasminogen activator) or cell growth/differentiation (i.e. cyclin or ornitine decarboxylase). Also, cytoskeleton proteins such as actin or tubulin were up-regulated for cell morphology remodeling. A message of vehicle trafficking molecule (synaptotagmin IV) was more remarkably increased (3.95-6.85-fold). Signaling molecules such as small G proteins (rab12, rab16, or ral), IkappaB, or STAT3 were altered by PACAP. It is noteworthy that PACAP inhibited the expression of galanin receptor 2, whose ligand was shown to inhibit tyrosine hydroxylase activity. Thus, in this study the transcriptome of PACAP-differentiated PC12 was established, leading to the elucidation of the molecular mechanism of neuritogenesis by the neuropeptide.
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Affiliation(s)
- Masami Ishido
- Endocrine Disruptors and Dioxin Research Projects, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
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González-García A, Pritchard CA, Paterson HF, Mavria G, Stamp G, Marshall CJ. RalGDS is required for tumor formation in a model of skin carcinogenesis. Cancer Cell 2005; 7:219-26. [PMID: 15766660 DOI: 10.1016/j.ccr.2005.01.029] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2004] [Revised: 12/07/2004] [Accepted: 01/25/2005] [Indexed: 02/04/2023]
Abstract
To investigate the role of signaling by the small GTPase Ral, we have generated mice deficient for RalGDS, a guanine nucleotide exchange factor that activates Ral. We show that RalGDS is dispensable for mouse development but plays a substantial role in Ras-induced oncogenesis. Lack of RalGDS results in reduced tumor incidence, size, and progression to malignancy in multistage skin carcinogenesis, and reduced transformation by Ras in tissue culture. RalGDS does not appear to participate in the regulation of cell proliferation, but instead controls survival of transformed cells. Experiments performed in cells isolated from skin tumors suggest that RalGDS mediates cell survival through the activation of the JNK/SAPK pathway. These studies identify RalGDS as a key component in Ras-dependent carcinogenesis in vivo.
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Affiliation(s)
- Ana González-García
- Cancer Research UK Centre for Cell and Molecular Biology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom
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Lebreton S, Boissel L, Iouzalen N, Moreau J. RLIP mediates downstream signalling from RalB to the actin cytoskeleton during Xenopus early development. Mech Dev 2004; 121:1481-94. [PMID: 15511640 DOI: 10.1016/j.mod.2004.07.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Revised: 07/13/2004] [Accepted: 07/26/2004] [Indexed: 10/26/2022]
Abstract
The Ras protein activates at least three different pathways during early development. Two of them regulate mesodermal gene expression and the third is thought to participate in the control of actin cytoskeleton dynamics via the Ral protein. From a yeast two-hybrid screen of a Xenopus maternal cDNA library, we identified the Xenopus orthologue of the Ral interacting protein (RLIP, RIP1 or RalBP1), a putative effector of small G protein Ral. Previously, we observed that a constitutively activated form of Ral GTPase (XralB G23V) induced bleaching of the animal hemisphere and disruption of the cortical actin cytoskeleton. To demonstrate that RLIP is the effector of RalB in early development, we show that the artificial targeting of RLIP to the membrane induces a similar phenotype to that of activated RalB. We show that overexpression of the Ral binding domain (RalBD) of XRLIP, which binds to the effector site of Ral, acts in competition with the endogenous effector of Ral and protects against the destructive effect of XralB G23V on the actin cytoskeleton. In contrast, the XRLIP has a synergistic effect on the activated form of XralB, which is dependent on the RalBD of RLIP. We provide evidence for the involvement of RLIP by way of its RalBD on the dynamics of the actin cytoskeleton and propose that signalling from Ral to RLIP is required for gastrulation.
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Affiliation(s)
- Stéphanie Lebreton
- Mécanismes Moléculaires du Développement, Institut Jacques Monod, CNRS, Universités Paris VI et Paris VII, 2 Place Jussieu, 75251 Paris 05, France
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Aktories K, Wilde C, Vogelsgesang M. Rho-modifying C3-like ADP-ribosyltransferases. Rev Physiol Biochem Pharmacol 2004; 152:1-22. [PMID: 15372308 DOI: 10.1007/s10254-004-0034-4] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
C3-like exoenzymes comprise a family of seven bacterial ADP-ribosyltransferases, which selectively modify RhoA, B, and C at asparagine-41. Crystal structures of C3 exoenzymes are available, allowing novel insights into the structure-function relationships of these exoenzymes. Because ADP-ribosylation specifically inhibits the biological functions of the low-molecular mass GTPases, C3 exoenzymes are established pharmacological tools to study the cellular functions of Rho GTPases. Recent studies, however, indicate that the functional consequences of C3-induced ADP-ribosylation are more complex than previously suggested. In the present review the basic properties of C3 exoenzymes are briefly summarized and new findings are reviewed.
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Affiliation(s)
- K Aktories
- Institute of Experimental and Clinical Pharmacology and Toxicology, Albert-Ludwigs University Freiburg, Otto-Krayer-Haus, Albertstr. 25, Freiburg, Germany.
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Sobering AK, Watanabe R, Romeo MJ, Yan BC, Specht CA, Orlean P, Riezman H, Levin DE. Yeast Ras regulates the complex that catalyzes the first step in GPI-anchor biosynthesis at the ER. Cell 2004; 117:637-48. [PMID: 15163411 DOI: 10.1016/j.cell.2004.05.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2004] [Revised: 04/12/2004] [Accepted: 04/12/2004] [Indexed: 10/26/2022]
Abstract
The yeast ERI1 gene encodes a small ER-localized protein that associates in vivo with GTP bound Ras2 in an effector loop-dependent manner. We showed previously that loss of Eri1 function results in hyperactive Ras phenotypes. Here, we demonstrate that Eri1 is a component of the GPI-GlcNAc transferase (GPI-GnT) complex in the ER, which catalyzes transfer of GlcNAc from UDP-GlcNAc to an acceptor phosphatidylinositol, the first step in the production of GPI-anchors for cell surface proteins. We also show that GTP bound Ras2 associates with the GPI-GnT complex in vivo and inhibits its activity, indicating that yeast Ras uses the ER as a signaling platform from which to negatively regulate the GPI-GnT. We propose that diminished GPI-anchor protein production contributes to hyperactive Ras phenotypes.
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Affiliation(s)
- Andrew K Sobering
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, MD 21205, USA
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Takaya A, Ohba Y, Kurokawa K, Matsuda M. RalA activation at nascent lamellipodia of epidermal growth factor-stimulated Cos7 cells and migrating Madin-Darby canine kidney cells. Mol Biol Cell 2004; 15:2549-57. [PMID: 15034142 PMCID: PMC420081 DOI: 10.1091/mbc.e03-11-0857] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
RalA, a member of the Ras-family GTPases, regulates various cellular functions such as filopodia formation, endocytosis, and exocytosis. On epidermal growth factor (EGF) stimulation, activated Ras recruits guanine nucleotide exchange factors (GEFs) for RalA, followed by RalA activation. By using fluorescence resonance energy transfer-based probes for RalA activity, we found that the EGF-induced RalA activation in Cos7 cells was restricted at the EGF-induced nascent lamellipodia, whereas under a similar condition both Ras activation and Ras-dependent translocation of Ral GEFs occurred more diffusely at the plasma membrane. This EGF-induced RalA activation was not observed when lamellipodial protrusion was suppressed by a dominant negative mutant of Rac1, a GTPase-activating protein for Cdc42, inhibitors of phosphatidylinositol 3-kinase, or inhibitors of actin polymerization. On the other hand, EGF-induced lamellipodial protrusion was inhibited by microinjection of the RalA-binding domains of RalBP1 and Sec5. Furthermore, we found that RalA activity was high at the lamellipodia of migrating Madin-Darby canine kidney cells and that the migration of Madin-Darby canine kidney cells was perturbed by the microinjection of RalBP1-RalA-binding domain. Thus, RalA activation is required for the induction of lamellipodia, and conversely, lamellipodial protrusion seems to be required for the RalA activation, suggesting the presence of a positive feedback loop between RalA activation and lamellipodial protrusion. Our observation also demonstrates that the spatial regulation of RalA is conducted by a mechanism distinct from the temporal regulation conducted by Ras-dependent plasma membrane recruitment of Ral guanine nucleotide exchange factors.
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Affiliation(s)
- Akiyuki Takaya
- Department of Tumor Virology, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Suita-shi, Osaka 565-0871, Japan
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