1
|
Richardson DS, Spehar JM, Han DT, Chakravarthy PA, Sizemore ST. The RAL Enigma: Distinct Roles of RALA and RALB in Cancer. Cells 2022; 11:cells11101645. [PMID: 35626682 PMCID: PMC9139244 DOI: 10.3390/cells11101645] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 04/29/2022] [Accepted: 05/05/2022] [Indexed: 11/16/2022] Open
Abstract
RALA and RALB are highly homologous small G proteins belonging to the RAS superfamily. Like other small GTPases, the RALs are molecular switches that can be toggled between inactive GDP-bound and active GTP-bound states to regulate diverse and critical cellular functions such as vesicle trafficking, filopodia formation, mitochondrial fission, and cytokinesis. The RAL paralogs are activated and inactivated by a shared set of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) and utilize similar sets of downstream effectors. In addition to their important roles in normal cell biology, the RALs are known to be critical mediators of cancer cell survival, invasion, migration, and metastasis. However, despite their substantial similarities, the RALs often display striking functional disparities in cancer. RALA and RALB can have redundant, unique, or even antagonistic functions depending on cancer type. The molecular basis for these discrepancies remains an important unanswered question in the field of cancer biology. In this review we examine the functions of the RAL paralogs in normal cellular physiology and cancer biology with special consideration provided to situations where the roles of RALA and RALB are non-redundant.
Collapse
|
2
|
D’Aloia A, Arrigoni E, Costa B, Berruti G, Martegani E, Sacco E, Ceriani M. RalGPS2 Interacts with Akt and PDK1 Promoting Tunneling Nanotubes Formation in Bladder Cancer and Kidney Cells Microenvironment. Cancers (Basel) 2021; 13:cancers13246330. [PMID: 34944949 PMCID: PMC8699646 DOI: 10.3390/cancers13246330] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/01/2021] [Accepted: 12/14/2021] [Indexed: 12/30/2022] Open
Abstract
Simple Summary Cell-to-cell communication in the tumor microenvironment is a crucial process to orchestrate the different components of the tumoral infrastructure. Among the mechanisms of cellular interplay in cancer cells, tunneling nanotubes (TNTs) are dynamic connections that play an important role. The mechanism of the formation of TNTs among cells and the molecules involved in the process remain to be elucidated. In this study, we analyze several bladder cancer cell lines, representative of tumors at different stages and grades. We demonstrate that TNTs are formed only by mid or high-stage cell lines that show muscle-invasive properties and that they actively transport mitochondria and proteins. The formation of TNTs is triggered by stressful conditions and starts with the assembly of a specific multimolecular complex. In this study, we characterize some of the protein components of the TNTs complex, as they are potential novel molecular targets for future therapies aimed at counteracting tumor progression. Abstract RalGPS2 is a Ras-independent Guanine Nucleotide Exchange Factor for RalA GTPase that is involved in several cellular processes, including cytoskeletal organization. Previously, we demonstrated that RalGPS2 also plays a role in the formation of tunneling nanotubes (TNTs) in bladder cancer 5637 cells. In particular, TNTs are a novel mechanism of cell–cell communication in the tumor microenvironment, playing a central role in cancer progression and metastasis formation. However, the molecular mechanisms involved in TNTs formation still need to be fully elucidated. Here we demonstrate that mid and high-stage bladder cancer cell lines have functional TNTs, which can transfer mitochondria. Moreover, using confocal fluorescence time-lapse microscopy, we show in 5637 cells that TNTs mediate the trafficking of RalA protein and transmembrane MHC class III protein leukocyte-specific transcript 1 (LST1). Furthermore, we show that RalGPS2 is essential for nanotubes generation, and stress conditions boost its expression both in 5637 and HEK293 cell lines. Finally, we prove that RalGPS2 interacts with Akt and PDK1, in addition to LST1 and RalA, leading to the formation of a complex that promotes nanotubes formation. In conclusion, our findings suggest that in the tumor microenvironment, RalGPS2 orchestrates the assembly of multimolecular complexes that drive the formation of TNTs.
Collapse
Affiliation(s)
- Alessia D’Aloia
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy; (A.D.); (E.A.); (B.C.); (E.M.); (E.S.)
| | - Edoardo Arrigoni
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy; (A.D.); (E.A.); (B.C.); (E.M.); (E.S.)
| | - Barbara Costa
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy; (A.D.); (E.A.); (B.C.); (E.M.); (E.S.)
| | - Giovanna Berruti
- Department of Biosciences, University of Milan, Via Celoria 26, 20133 Milan, Italy;
| | - Enzo Martegani
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy; (A.D.); (E.A.); (B.C.); (E.M.); (E.S.)
- SYSBIO-ISBE-IT-Candidate National Node of Italy for ISBE, Research Infrastructure for Systems Biology Europe, 20126 Milan, Italy
| | - Elena Sacco
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy; (A.D.); (E.A.); (B.C.); (E.M.); (E.S.)
- SYSBIO-ISBE-IT-Candidate National Node of Italy for ISBE, Research Infrastructure for Systems Biology Europe, 20126 Milan, Italy
| | - Michela Ceriani
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy; (A.D.); (E.A.); (B.C.); (E.M.); (E.S.)
- Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Piazza dell’Ateneo Nuovo 1, 20126 Milano, Italy
- Correspondence: ; Tel.: +39-0264483544
| |
Collapse
|
3
|
Hussain SS, Tran TM, Ware TB, Luse MA, Prevost CT, Ferguson AN, Kashatus JA, Hsu KL, Kashatus DF. RalA and PLD1 promote lipid droplet growth in response to nutrient withdrawal. Cell Rep 2021; 36:109451. [PMID: 34320341 PMCID: PMC8344381 DOI: 10.1016/j.celrep.2021.109451] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 06/04/2021] [Accepted: 07/02/2021] [Indexed: 01/22/2023] Open
Abstract
Lipid droplets (LDs) are dynamic organelles that undergo dynamic changes in response to changing cellular conditions. During nutrient depletion, LD numbers increase to protect cells against toxic fatty acids generated through autophagy and provide fuel for beta-oxidation. However, the precise mechanisms through which these changes are regulated have remained unclear. Here, we show that the small GTPase RalA acts downstream of autophagy to directly facilitate LD growth during nutrient depletion. Mechanistically, RalA performs this function through phospholipase D1 (PLD1), an enzyme that converts phosphatidylcholine (PC) to phosphatidic acid (PA) and that is recruited to lysosomes during nutrient stress in a RalA-dependent fashion. RalA inhibition prevents recruitment of the LD-associated protein perilipin 3, which is required for LD growth. Our data support a model in which RalA recruits PLD1 to lysosomes during nutrient deprivation to promote the localized production of PA and the recruitment of perilipin 3 to expanding LDs.
Collapse
Affiliation(s)
- Syed S Hussain
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA 22908, USA
| | - Tuyet-Minh Tran
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA 22908, USA
| | - Timothy B Ware
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
| | - Melissa A Luse
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA 22908, USA
| | - Christopher T Prevost
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA 22908, USA
| | - Ashley N Ferguson
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA 22908, USA
| | - Jennifer A Kashatus
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA 22908, USA
| | - Ku-Lung Hsu
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA; University of Virginia Cancer Center, University of Virginia Health System, Charlottesville, VA 22903, USA
| | - David F Kashatus
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA 22908, USA; University of Virginia Cancer Center, University of Virginia Health System, Charlottesville, VA 22903, USA.
| |
Collapse
|
4
|
Lei Z, Wang J, Zhang L, Liu CH. Ubiquitination-Dependent Regulation of Small GTPases in Membrane Trafficking: From Cell Biology to Human Diseases. Front Cell Dev Biol 2021; 9:688352. [PMID: 34277632 PMCID: PMC8281112 DOI: 10.3389/fcell.2021.688352] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 06/09/2021] [Indexed: 01/04/2023] Open
Abstract
Membrane trafficking is critical for cellular homeostasis, which is mainly carried out by small GTPases, a class of proteins functioning in vesicle budding, transport, tethering and fusion processes. The accurate and organized membrane trafficking relies on the proper regulation of small GTPases, which involves the conversion between GTP- and GDP-bound small GTPases mediated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Emerging evidence indicates that post-translational modifications (PTMs) of small GTPases, especially ubiquitination, play an important role in the spatio-temporal regulation of small GTPases, and the dysregulation of small GTPase ubiquitination can result in multiple human diseases. In this review, we introduce small GTPases-mediated membrane trafficking pathways and the biological processes of ubiquitination-dependent regulation of small GTPases, including the regulation of small GTPase stability, activity and localization. We then discuss the dysregulation of small GTPase ubiquitination and the associated human membrane trafficking-related diseases, focusing on the neurological diseases and infections. An in-depth understanding of the molecular mechanisms by which ubiquitination regulates small GTPases can provide novel insights into the membrane trafficking process, which knowledge is valuable for the development of more effective and specific therapeutics for membrane trafficking-related human diseases.
Collapse
Affiliation(s)
- Zehui Lei
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Beijing, China.,Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Jing Wang
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Beijing, China
| | - Lingqiang Zhang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences (Beijing), Beijing Institute of Lifeomics, Beijing, China
| | - Cui Hua Liu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Beijing, China.,Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| |
Collapse
|
5
|
Apken LH, Oeckinghaus A. The RAL signaling network: Cancer and beyond. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2020; 361:21-105. [PMID: 34074494 DOI: 10.1016/bs.ircmb.2020.10.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The RAL proteins RALA and RALB belong to the superfamily of small RAS-like GTPases (guanosine triphosphatases). RAL GTPases function as molecular switches in cells by cycling through GDP- and GTP-bound states, a process which is regulated by several guanine exchange factors (GEFs) and two heterodimeric GTPase activating proteins (GAPs). Since their discovery in the 1980s, RALA and RALB have been established to exert isoform-specific functions in central cellular processes such as exocytosis, endocytosis, actin organization and gene expression. Consequently, it is not surprising that an increasing number of physiological functions are discovered to be controlled by RAL, including neuronal plasticity, immune response, and glucose and lipid homeostasis. The critical importance of RAL GTPases for oncogenic RAS-driven cellular transformation and tumorigenesis still attracts most research interest. Here, RAL proteins are key drivers of cell migration, metastasis, anchorage-independent proliferation, and survival. This chapter provides an overview of normal and pathological functions of RAL GTPases and summarizes the current knowledge on the involvement of RAL in human disease as well as current therapeutic targeting strategies. In particular, molecular mechanisms that specifically control RAL activity and RAL effector usage in different scenarios are outlined, putting a spotlight on the complexity of the RAL GTPase signaling network and the emerging theme of RAS-independent regulation and relevance of RAL.
Collapse
Affiliation(s)
- Lisa H Apken
- Institute of Molecular Tumor Biology, Faculty of Medicine, University of Münster, Münster, Germany
| | - Andrea Oeckinghaus
- Institute of Molecular Tumor Biology, Faculty of Medicine, University of Münster, Münster, Germany.
| |
Collapse
|
6
|
Wang X, Gou L, Gao Y, Huang Y, Kuai R, Li Y, Wang Y, Chen Y, Li J, Cheng C, Feng Z, Wu X, Yao R. RalA exerts an inhibitory effect on IL-1β/IL-18 secretion by blocking NLRP3 inflammasome activation in levornidazole-treated human THP-1 macrophages. Int Immunopharmacol 2020; 88:106898. [PMID: 32866784 DOI: 10.1016/j.intimp.2020.106898] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/11/2020] [Accepted: 08/11/2020] [Indexed: 12/17/2022]
Abstract
The NLRP3 inflammasome is an important mediator of inflammatory responses and its regulation is an active area of research. RalA is a Ras-like GTPase, which play pivotal roles in the biology of cells. So far, there have been very few studies on RalA regulating inflammatory responses. Bioinformatics analysis predicted that RalA might participate in the regulatory network of NLRP3 inflammasome, which has been confirmed in THP-1 macrophages. After virtual screening of compounds, it was found that levonidazole selected from our virtual small molecule compound library has the potential to bind to RalA. Of note, the interaction of RalA/levornidazole was verified by Surface Plasmon Resonance-Biacore T200, LC/MS analysis and Western blotting analysis. Molecular dynamics simulations revealed that the conformational changes of RalA might be regulated by levornidazole. Additionally, IL-1β/IL-18 secretion from ATP + LPS stimulated THP-1-derived macrophages was RalA-dependently suppressed by levornidazole, suggesting that RalA might have an inhibitory effect on NLRP3 inflammasome activation. The results of co-immunoprecipitation and RalA depletion experiments showed that levornidazole could induce RalA to block the assembly of NLRP3/ASC/pro-caspase-1 complex, thereby reducing the levels of cleaved-caspase-1 and IL-1β/IL-18 secretion. Our study has suggested an anti-inflammatory function of RalA and identified its targeting chemical compound. Overall, this study clarifies a novel pharmacological mechanism by which RalA/levornidazole inhibits NLRP3 inflammasome activation and IL-1β/IL-18 secretion.
Collapse
Affiliation(s)
- Xingqi Wang
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China.
| | - Lingshan Gou
- Center for Genetic Medicine, Xuzhou Maternity and Child Health Care Hospital, Xuzhou 221009, Jiangsu, China
| | - Yuzhi Gao
- Department of Cell Biology, Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical University, 209 Tongshan Road, Xuzhou 221009, Jiangsu, China
| | - Yuqing Huang
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China
| | - Rui Kuai
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China
| | - Yu Li
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China
| | - Yujing Wang
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China
| | - Yanhong Chen
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China
| | - Jun Li
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China
| | - Chao Cheng
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China
| | - Zhaojun Feng
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, 101 Shanghai Road, Xuzhou 221116, Jiangsu, China
| | - Xuefeng Wu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 163 Xianlin Avenue, Nanjing 210093, Jiangsu, China.
| | - Ruiqin Yao
- Department of Cell Biology, Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical University, 209 Tongshan Road, Xuzhou 221009, Jiangsu, China.
| |
Collapse
|
7
|
Pollock SR, Schinlever AR, Rohani A, Kashatus JA, Kashatus DF. RalA and RalB relocalization to depolarized mitochondria depends on clathrin-mediated endocytosis and facilitates TBK1 activation. PLoS One 2019; 14:e0214764. [PMID: 30995277 PMCID: PMC6469766 DOI: 10.1371/journal.pone.0214764] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 03/19/2019] [Indexed: 01/08/2023] Open
Abstract
Healthy mitochondria use an electrochemical gradient across the inner mitochondrial membrane (IMM) to generate energy in the form of ATP. A variety of endogenous and exogenous factors can lead to transient or sustained depolarization of the IMM, including mitochondrial fission events, expression of uncoupling proteins, electron transport chain (ETC) inhibitors, or chemical uncouplers. This depolarization in turn leads to a variety of physiological responses, ranging from selective mitochondrial clearance (mitophagy) to cell death. How cells recognize and ultimately respond to depolarized mitochondria remains incompletely understood. Here we show that the small GTPases RalA and RalB both relocalize to mitochondria following depolarization in a process dependent on clathrin-mediated endocytosis (CME). Furthermore, both genetic and pharmacologic inhibition of RalA and RalB leads to an increase in the activity of the atypical IκB kinase TBK1 both basally and in response to mitochondrial depolarization. This phenotype was also observed following inhibition of Ral relocalization. Collectively, these data suggest a model in which RalA and RalB inhibit TBK1 and that relocalization of Ral to depolarized mitochondria facilitates TBK1 activation through release of this inhibition.
Collapse
Affiliation(s)
- Sarah R. Pollock
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - Austin R. Schinlever
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - Ali Rohani
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - Jennifer A. Kashatus
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - David F. Kashatus
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
- * E-mail:
| |
Collapse
|
8
|
Lee SH, Mayr C. Gain of Additional BIRC3 Protein Functions through 3'-UTR-Mediated Protein Complex Formation. Mol Cell 2019; 74:701-712.e9. [PMID: 30948266 DOI: 10.1016/j.molcel.2019.03.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 01/08/2019] [Accepted: 03/04/2019] [Indexed: 12/13/2022]
Abstract
Alternative 3' untranslated regions (3' UTRs) are widespread, but their functional roles are largely unknown. We investigated the function of the long BIRC3 3' UTR, which is upregulated in leukemia. The 3' UTR does not regulate BIRC3 protein localization or abundance but is required for CXCR4-mediated B cell migration. We established an experimental pipeline to study the mechanism of regulation and used mass spectrometry to identify BIRC3 protein interactors. In addition to 3'-UTR-independent interactors involved in known BIRC3 functions, we detected interactors that bind only to BIRC3 protein encoded from the mRNA with the long 3' UTR. They regulate several functions, including CXCR4 trafficking. We further identified RNA-binding proteins differentially bound to the alternative 3' UTRs and found that cooperative binding of Staufen and HuR mediates 3'-UTR-dependent complex formation. We show that the long 3' UTR is required for the formation of specific protein complexes that enable additional functions of BIRC3 protein beyond its 3'-UTR-independent functions.
Collapse
Affiliation(s)
- Shih-Han Lee
- Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Christine Mayr
- Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
| |
Collapse
|
9
|
Thomas JC, Cooper JM, Clayton NS, Wang C, White MA, Abell C, Owen D, Mott HR. Inhibition of Ral GTPases Using a Stapled Peptide Approach. J Biol Chem 2016; 291:18310-25. [PMID: 27334922 DOI: 10.1074/jbc.m116.720243] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Indexed: 01/31/2023] Open
Abstract
Aberrant Ras signaling drives numerous cancers, and drugs to inhibit this are urgently required. This compelling clinical need combined with recent innovations in drug discovery including the advent of biologic therapeutic agents, has propelled Ras back to the forefront of targeting efforts. Activated Ras has proved extremely difficult to target directly, and the focus has moved to the main downstream Ras-signaling pathways. In particular, the Ras-Raf and Ras-PI3K pathways have provided conspicuous enzyme therapeutic targets that were more accessible to conventional drug-discovery strategies. The Ras-RalGEF-Ral pathway is a more difficult challenge for traditional medicinal development, and there have, therefore, been few inhibitors reported that disrupt this axis. We have used our structure of a Ral-effector complex as a basis for the design and characterization of α-helical-stapled peptides that bind selectively to active, GTP-bound Ral proteins and that compete with downstream effector proteins. The peptides have been thoroughly characterized biophysically. Crucially, the lead peptide enters cells and is biologically active, inhibiting isoform-specific RalB-driven cellular processes. This, therefore, provides a starting point for therapeutic inhibition of the Ras-RalGEF-Ral pathway.
Collapse
Affiliation(s)
- Jemima C Thomas
- From the Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom, Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | - Jonathan M Cooper
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390-9039
| | - Natasha S Clayton
- From the Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom
| | - Chensu Wang
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390-9039
| | - Michael A White
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390-9039
| | - Chris Abell
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | - Darerca Owen
- From the Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom,
| | - Helen R Mott
- From the Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom,
| |
Collapse
|
10
|
Gentry LR, Nishimura A, Cox AD, Martin TD, Tsygankov D, Nishida M, Elston TC, Der CJ. Divergent roles of CAAX motif-signaled posttranslational modifications in the regulation and subcellular localization of Ral GTPases. J Biol Chem 2015. [PMID: 26216878 DOI: 10.1074/jbc.m115.656710] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The Ras-like small GTPases RalA and RalB are well validated effectors of RAS oncogene-driven human cancer growth, and pharmacologic inhibitors of Ral function may provide an effective anti-Ras therapeutic strategy. Intriguingly, although RalA and RalB share strong overall amino acid sequence identity, exhibit essentially identical structural and biochemical properties, and can utilize the same downstream effectors, they also exhibit divergent and sometimes opposing roles in the tumorigenic and metastatic growth of different cancer types. These distinct biological functions have been attributed largely to sequence divergence in their carboxyl-terminal hypervariable regions. However, the role of posttranslational modifications signaled by the hypervariable region carboxyl-terminal tetrapeptide CAAX motif (C = cysteine, A = aliphatic amino acid, X = terminal residue) in Ral isoform-selective functions has not been addressed. We determined that these modifications have distinct roles and consequences. Both RalA and RalB require Ras converting CAAX endopeptidase 1 (RCE1) for association with the plasma membrane, albeit not with endomembranes, and loss of RCE1 caused mislocalization as well as sustained activation of both RalA and RalB. In contrast, isoprenylcysteine carboxylmethyltransferase (ICMT) deficiency disrupted plasma membrane localization only of RalB, whereas RalA depended on ICMT for efficient endosomal localization. Furthermore, the absence of ICMT increased stability of RalB but not RalA protein. Finally, palmitoylation was critical for subcellular localization of RalB but not RalA. In summary, we have identified striking isoform-specific consequences of distinct CAAX-signaled posttranslational modifications that contribute to the divergent subcellular localization and activity of RalA and RalB.
Collapse
Affiliation(s)
| | - Akiyuki Nishimura
- the Division of Cardiocirculatory Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institutes of Natural Sciences, 5-1 Higashiyama, Myoudaiji-cho, Okazaki, Aichi 444-8787, Japan
| | - Adrienne D Cox
- From the Departments of Pharmacology and Radiation Oncology, and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 and
| | | | | | - Motohiro Nishida
- the Division of Cardiocirculatory Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institutes of Natural Sciences, 5-1 Higashiyama, Myoudaiji-cho, Okazaki, Aichi 444-8787, Japan
| | | | - Channing J Der
- From the Departments of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 and
| |
Collapse
|
11
|
Gentry LR, Martin TD, Reiner DJ, Der CJ. Ral small GTPase signaling and oncogenesis: More than just 15minutes of fame. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2976-2988. [PMID: 25219551 DOI: 10.1016/j.bbamcr.2014.09.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 09/03/2014] [Accepted: 09/04/2014] [Indexed: 01/26/2023]
Abstract
Since their discovery in 1986, Ral (Ras-like) GTPases have emerged as critical regulators of diverse cellular functions. Ral-selective guanine nucleotide exchange factors (RalGEFs) function as downstream effectors of the Ras oncoprotein, and the RalGEF-Ral signaling network comprises the third best characterized effector of Ras-dependent human oncogenesis. Because of this, Ral GTPases as well as their effectors are being explored as possible therapeutic targets in the treatment of RAS mutant cancer. The two Ral isoforms, RalA and RalB, interact with a variety of downstream effectors and have been found to play key and distinct roles in both normal and neoplastic cell physiology including regulation of vesicular trafficking, migration and invasion, tumor formation, metastasis, and gene expression. In this review we provide an overview of Ral biochemistry and biology, and we highlight recent discoveries.
Collapse
Affiliation(s)
- Leanna R Gentry
- University of North Carolina at Chapel Hill, Department of Pharmacology, Chapel Hill, NC, USA
| | | | - David J Reiner
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX, USA
| | - Channing J Der
- University of North Carolina at Chapel Hill, Department of Pharmacology, Chapel Hill, NC, USA; University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA.
| |
Collapse
|
12
|
Tang SC, Chen YC. Novel therapeutic targets for pancreatic cancer. World J Gastroenterol 2014; 20:10825-10844. [PMID: 25152585 PMCID: PMC4138462 DOI: 10.3748/wjg.v20.i31.10825] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 02/13/2014] [Accepted: 04/09/2014] [Indexed: 02/06/2023] Open
Abstract
Pancreatic cancer has become the fourth leading cause of cancer death in the last two decades. Only 3%-15% of patients diagnosed with pancreatic cancer had 5 year survival rate. Drug resistance, high metastasis, poor prognosis and tumour relapse contributed to the malignancies and difficulties in treating pancreatic cancer. The current standard chemotherapy for pancreatic cancer is gemcitabine, however its efficacy is far from satisfactory, one of the reasons is due to the complex tumour microenvironment which decreases effective drug delivery to target cancer cell. Studies of the molecular pathology of pancreatic cancer have revealed that activation of KRAS, overexpression of cyclooxygenase-2, inactivation of p16INK4A and loss of p53 activities occurred in pancreatic cancer. Co-administration of gemcitabine and targeting the molecular pathological events happened in pancreatic cancer has brought an enhanced therapeutic effectiveness of gemcitabine. Therefore, studies looking for novel targets in hindering pancreatic tumour growth are emerging rapidly. In order to give a better understanding of the current findings and to seek the direction in future pancreatic cancer research; in this review we will focus on targets suppressing tumour metastatsis and progression, KRAS activated downstream effectors, the relationship of Notch signaling and Nodal/Activin signaling with pancreatic cancer cells, the current findings of non-coding RNAs in inhibiting pancreatic cancer cell proliferation, brief discussion in transcription remodeling by epigenetic modifiers (e.g., HDAC, BMI1, EZH2) and the plausible therapeutic applications of cancer stem cell and hyaluronan in tumour environment.
Collapse
|
13
|
Abstract
Recognition that Ral guanine nucleotide exchange factors (RalGEFs) are direct Ras effectors and that Ral G-protein activation is a direct consequence of Ras activation has spurred focused efforts to establish the contribution of RalGEF/Ral signaling to oncogenic transformation. Here, we provide a broad-strokes overview of the mechanistic organization of the RalGEF/Ral signaling network, evaluate the evidence for participation of this network in tumorigenic regulatory milieus, consider targeting strategies, and discuss the challenges to and opportunities for clinical development of these targeting strategies.
Collapse
Affiliation(s)
- Jonathan M Cooper
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Brian O Bodemann
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Michael A White
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas, USA.
| |
Collapse
|
14
|
The deubiquitylase USP33 discriminates between RALB functions in autophagy and innate immune response. Nat Cell Biol 2013; 15:1220-30. [PMID: 24056301 DOI: 10.1038/ncb2847] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 08/20/2013] [Indexed: 12/17/2022]
Abstract
The RAS-like GTPase RALB mediates cellular responses to nutrient availability or viral infection by respectively engaging two components of the exocyst complex, EXO84 and SEC5. RALB employs SEC5 to trigger innate immunity signalling, whereas RALB-EXO84 interaction induces autophagocytosis. How this differential interaction is achieved molecularly by the RAL GTPase remains unknown. We found that whereas GTP binding turns on RALB activity, ubiquitylation of RALB at Lys 47 tunes its activity towards a particular effector. Specifically, ubiquitylation at Lys 47 sterically inhibits RALB binding to EXO84, while facilitating its interaction with SEC5. Double-stranded RNA promotes RALB ubiquitylation and SEC5-TBK1 complex formation. In contrast, nutrient starvation induces RALB deubiquitylation by accumulation and relocalization of the deubiquitylase USP33 to RALB-positive vesicles. Deubiquitylated RALB promotes the assembly of the RALB-EXO84-beclin-1 complexes driving autophagosome formation. Thus, ubiquitylation within the effector-binding domain provides the switch for the dual functions of RALB in autophagy and innate immune responses.
Collapse
|
15
|
Ral GTPases in tumorigenesis: emerging from the shadows. Exp Cell Res 2013; 319:2337-42. [PMID: 23830877 DOI: 10.1016/j.yexcr.2013.06.020] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/18/2013] [Accepted: 06/26/2013] [Indexed: 01/03/2023]
Abstract
Oncogenic Ras proteins rely on a series of key effector pathways to drive the physiological changes that lead to tumorigenic growth. Of these effector pathways, the RalGEF pathway, which activates the two Ras-related GTPases RalA and RalB, remains the most poorly understood. This review will focus on key developments in our understanding of Ral biology, and will speculate on how aberrant activation of the multiple diverse Ral effector proteins might collectively contribute to oncogenic transformation and other aspects of tumor progression.
Collapse
|