151
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Vakiani E, Solit DB. KRAS and BRAF: drug targets and predictive biomarkers. J Pathol 2010; 223:219-29. [PMID: 21125676 DOI: 10.1002/path.2796] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 09/22/2010] [Accepted: 09/24/2010] [Indexed: 12/11/2022]
Abstract
Three decades have passed since RAS was first identified as the transformative factor in the Harvey and Kirsten strains of the mouse sarcoma virus. RAS and several of its downstream effectors, including BRAF, have since been shown to be commonly mutated in broad range of human cancers and biological studies have confirmed that RAS pathway activation promotes tumour initiation, progression and metastatic spread in many contexts. With the identification of RAS mutation as a strong predictor of clinical resistance to EGFR-targeted therapies, RAS mutational testing has been incorporated into the routine clinical care of patients with colorectal and lung cancers. This article reviews the current understanding of RAS signalling as it relates to cancer biology, current efforts to develop inhibitors of RAS and its key downstream effectors and the technical challenges of RAS mutational testing in the clinical setting.
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Affiliation(s)
- Efsevia Vakiani
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
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152
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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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153
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Saraç ÖS, Atalay V, Cetin-Atalay R. GOPred: GO molecular function prediction by combined classifiers. PLoS One 2010; 5:e12382. [PMID: 20824206 PMCID: PMC2930845 DOI: 10.1371/journal.pone.0012382] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Accepted: 06/22/2010] [Indexed: 11/18/2022] Open
Abstract
Functional protein annotation is an important matter for in vivo and in silico biology. Several computational methods have been proposed that make use of a wide range of features such as motifs, domains, homology, structure and physicochemical properties. There is no single method that performs best in all functional classification problems because information obtained using any of these features depends on the function to be assigned to the protein. In this study, we portray a novel approach that combines different methods to better represent protein function. First, we formulated the function annotation problem as a classification problem defined on 300 different Gene Ontology (GO) terms from molecular function aspect. We presented a method to form positive and negative training examples while taking into account the directed acyclic graph (DAG) structure and evidence codes of GO. We applied three different methods and their combinations. Results show that combining different methods improves prediction accuracy in most cases. The proposed method, GOPred, is available as an online computational annotation tool (http://kinaz.fen.bilkent.edu.tr/gopred).
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Affiliation(s)
- Ömer Sinan Saraç
- Department of Computer Engineering, Middle East Technical University, Ankara, Turkey
| | - Volkan Atalay
- Department of Computer Engineering, Middle East Technical University, Ankara, Turkey
| | - Rengul Cetin-Atalay
- Department of Molecular Biology and Genetics, Faculty of Science, Bilkent University, Ankara, Turkey
- * E-mail:
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154
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Vigil D, Martin TD, Williams F, Yeh JJ, Campbell SL, Der CJ. Aberrant overexpression of the Rgl2 Ral small GTPase-specific guanine nucleotide exchange factor promotes pancreatic cancer growth through Ral-dependent and Ral-independent mechanisms. J Biol Chem 2010; 285:34729-40. [PMID: 20801877 DOI: 10.1074/jbc.m110.116756] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Our recent studies established essential and distinct roles for RalA and RalB small GTPase activation in K-Ras mutant pancreatic ductal adenocarcinoma (PDAC) cell line tumorigencity, invasion, and metastasis. However, the mechanism of Ral GTPase activation in PDAC has not been determined. There are four highly related mammalian RalGEFs (RalGDS, Rgl1, Rgl2, and Rgl3) that can serve as Ras effectors. Whether or not they share distinct or overlapping functions in K-Ras-mediated growth transformation has not been explored. We found that plasma membrane targeting to mimic persistent Ras activation enhanced the growth-transforming activities of RalGEFs. Unexpectedly, transforming activity did not correlate directly with total cell steady-state levels of Ral activation. Next, we observed elevated Rgl2 expression in PDAC tumor tissue and cell lines. Expression of dominant negative Ral, which blocks RalGEF function, as well as interfering RNA suppression of Rgl2, reduced PDAC cell line steady-state Ral activity, growth in soft agar, and Matrigel invasion. Surprisingly, the effect of Rgl2 on anchorage-independent growth could not be rescued by constitutively activated RalA, suggesting a novel Ral-independent function for Rgl2 in transformation. Finally, we determined that Rgl2 and RalB both localized to the leading edge, and this localization of RalB was dependent on endogenous Rgl2 expression. In summary, our observations support nonredundant roles for RalGEFs in Ras-mediated oncogenesis and a key role for Rgl2 in Ral activation and Ral-independent PDAC growth.
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155
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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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156
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Zipfel PA, Brady DC, Kashatus DF, Ancrile BD, Tyler DS, Counter CM. Ral activation promotes melanomagenesis. Oncogene 2010; 29:4859-64. [PMID: 20562921 PMCID: PMC2928877 DOI: 10.1038/onc.2010.224] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Up to one-third of human melanomas are characterized by an oncogenic mutation in the gene encoding the small guanosine triphosphatase (GTPase) NRAS. Ras proteins activate three primary classes of effectors, namely, Rafs, phosphatidyl-inositol-3-kinases (PI3Ks) and Ral guanine exchange factors (RalGEFs). In melanomas lacking NRAS mutations, the first two effectors can still be activated through an oncogenic BRAF mutation coupled with a loss of the PI3K negative regulator PTEN. This suggests that Ras effectors promote melanoma, regardless of whether they are activated by oncogenic NRas. The only major Ras effector pathway not explored for its role in melanoma is the RalGEF-Ral pathway, in which Ras activation of RalGEFs converts the small GTPases RalA and RalB to an active guanosine triphosphate-bound state. We report that RalA is activated in several human melanoma cancer cell lines harboring an oncogenic NRAS allele, an oncogenic BRAF allele or wild-type NRAS and BRAF alleles. Furthermore, short hairpin RNA (shRNA)-mediated knockdown of RalA, and to a lesser extent of RalB, variably inhibited the tumorigenic growth of melanoma cell lines having these three genotypes. Thus, as is the case for Raf and PI3 K signaling, Rals also contribute to melanoma tumorigenesis.
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Affiliation(s)
- P A Zipfel
- Department of Surgery, Duke University Medical Center, Durham, NC, USA
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157
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Henry GD, Corrigan DJ, Dineen JV, Baleja JD. Charge effects in the selection of NPF motifs by the EH domain of EHD1. Biochemistry 2010; 49:3381-92. [PMID: 20329706 DOI: 10.1021/bi100065r] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The Eps15 homology (EH) domain is found in proteins associated with endocytosis and vesicle trafficking. EH domains bind to their target proteins through an asparagine-proline-phenylalanine (NPF) motif. We have measured the interaction energetics of the EH domain from EHD1 with peptides derived from two of its binding partners: Rabenosyn-5 (Ac-GPSLNPFDEED-NH(2)) and Rab11-Fip2 (Ac-YESTNPFTAK-NH(2)). Heteronuclear single quantum coherence (HSQC) spectroscopy shows that both peptides bind in the canonical binding pocket of EHD1 EH and induce identical structural changes, yet the affinity of the negatively charged Ac-GPSLNPFDEED-NH(2) (K(a) = 8 x 10(5) M(-1)) is tighter by 2 orders of magnitude. The thermodynamic profiles (DeltaG, DeltaH, DeltaS) were measured for both peptides as a function of temperature. The enthalpies of binding are essentially identical, and the difference in affinity is a consequence of the difference in entropic cost. Ac-GPSLNPFDEED-NH(2) binding is salt-dependent, demonstrating an electrostatic component to the interaction, whereas Ac-YESTNPFTAK-NH(2) binding is independent of salt. Successive replacement of acidic residues in Ac-GPSLNPFDEED-NH(2) with neutral residues showed that all are important. Lysine side chains in EHD1 EH create a region of strong positive surface potential near the NPF binding pocket. Contributions by lysine epsilon-amino groups to complex formation with Ac-GPSLNPFDEED-NH(2) was shown using direct-observe (15)N NMR spectroscopy. These experiments have enabled us to define a new extended interaction motif for EHD proteins, N-P-F-[DE]-[DE]-[DE], which we have used to predict new interaction partners and hence broaden the range of cellular activities involving the EHD proteins.
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Affiliation(s)
- Gillian D Henry
- Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, USA
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158
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Mishra PJ, Ha L, Rieker J, Sviderskaya EV, Bennett DC, Oberst MD, Kelly K, Merlino G. Dissection of RAS downstream pathways in melanomagenesis: a role for Ral in transformation. Oncogene 2010; 29:2449-56. [PMID: 20118982 PMCID: PMC3287039 DOI: 10.1038/onc.2009.521] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 12/21/2009] [Accepted: 12/23/2009] [Indexed: 12/18/2022]
Abstract
Cutaneous malignant melanoma is considered one of the most deadly human cancers, based on both its penchant for metastatic spread and its typical resistance to currently available therapy. Long known to harbor oncogenic NRAS mutations, melanomas were more recently reported to be frequent bearers of activating mutations in BRAF, one of the effectors situated downstream of wild-type NRAS. NRAS and BRAF mutations are rarely found in the same melanoma, suggesting that they may possess important overlapping oncogenic activities. Here, we compare and contrast the oncogenic roles of the three major NRas downstream effectors, Raf, phosphatidylinositol 3-kinase (PI3K) and Ral guanine exchange factor (RalGEF), using genetically engineered Arf-deficient immortalized mouse melanocytes as a model system. Although no single downstream pathway could recapitulate all of the consequences of oncogenic NRas expression, our data indicate a prominent role for BRaf and PI3K in melanocyte senescence and invasiveness, respectively. More surprisingly, we discovered that constitutive RalGEF activation had a major impact on several malignant phenotypes, particularly anchorage-independent growth, indicating that this often overlooked pathway should be more carefully evaluated as a possible therapeutic target.
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Affiliation(s)
- P J Mishra
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, NIH, Bethesda, MD 20892-4264, USA
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159
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Abstract
Activating mutations of NRAS are common in acute myeloid leukemia, chronic myelomonocytic leukemia, and myelodysplastic syndrome. Like all RAS proteins, NRAS must undergo a series of post-translational modifications for differential targeting to distinct membrane subdomains. Although farnesylation is the obligatory first step in post-translational modifications of RAS, to date, successes of therapies targeting farnesyl protein transferase are modest. Other RAS modifications, such as palmitoylation, are required for optimal plasma membrane association of RAS proteins. However, the relative importance of these latter modifications of RAS in leukemogenesis is not clear. We have previously shown that expression of oncogenic NRAS using a bone marrow transduction and transplantation model efficiently induces a chronic myelomonocytic leukemia- or acute myeloid leukemia-like disease in mice. Here we examined the role of palmitoylation in NRAS leukemogenesis using this model. We found that palmitoylation is essential for leukemogenesis by oncogenic NRAS. We also found that farnesylation is essential for NRAS leukemogenesis, yet through a different mechanism from that of palmitoylation deficiency. This study demonstrates, for the first time, that palmitoylation is an essential process for NRAS leukemogenesis and suggests that the development of therapies targeting RAS palmitoylation may be effective in treating oncogenic NRAS-associated malignancies.
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160
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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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161
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Balasubramanian N, Meier JA, Scott DW, Norambuena A, White MA, Schwartz MA. RalA-exocyst complex regulates integrin-dependent membrane raft exocytosis and growth signaling. Curr Biol 2009; 20:75-9. [PMID: 20005108 DOI: 10.1016/j.cub.2009.11.016] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Revised: 11/06/2009] [Accepted: 11/06/2009] [Indexed: 01/03/2023]
Abstract
Anchorage dependence of cell growth is a key metastasis-suppression mechanism that is mediated by effects of integrins on growth signaling pathways. The small GTPase RalA is activated in metastatic cancers through multiple mechanisms and specifically induces anchorage independence. Loss of integrin-mediated adhesion triggers caveolin-dependent internalization of cholesterol- and sphingolipid-rich lipid raft microdomains to the recycling endosomes; these domains serve as platforms for many signaling pathways, and their clearance from the plasma membrane (PM) after cell detachment suppresses growth signaling. Conversely, readhesion triggers their return to the PM and restores growth signaling. Activation of Arf6 by integrins mediates exit of raft markers from the recycling endosomes but is not sufficient for return to the PM. We now show that RalA but not RalB mediates integrin-dependent membrane raft exocytosis through the exocyst complex. Constitutively active RalA restores membrane raft targeting to promote anchorage-independent growth signaling. Ras-transformed pancreatic cancer cells also show RalA-dependent constitutive PM raft targeting. These results identify RalA as a key determinant of integrin-dependent membrane raft trafficking and regulation of growth signaling. They therefore define a mechanism by which RalA regulates anchorage dependence and provide a new link between integrin signaling and cancer.
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Affiliation(s)
- Nagaraj Balasubramanian
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.
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162
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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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163
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Differential requirement of CAAX-mediated posttranslational processing for Rheb localization and signaling. Oncogene 2009; 29:380-91. [PMID: 19838215 PMCID: PMC2809798 DOI: 10.1038/onc.2009.336] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Rheb1 and Rheb2 small GTPases and their effector mTOR are aberrantly activated in human cancer and are attractive targets for anti-cancer drug discovery. Rheb is targeted to endomembranes via its C-terminal CAAX (C = cysteine, A = aliphatic, X = terminal amino acid) motif, a substrate for posttranslational modification by a farnesyl isoprenoid. Following farnesylation, Rheb undergoes two additional CAAX-signaled processing steps, Rce1-catalyzed cleavage of the AAX residues and Icmt-mediated carboxylmethylation of the farnesylated cysteine. However, whether these post-prenylation processing steps are required for Rheb signaling through mTOR is not known. We found that Rheb1 and Rheb2 localize primarily to the endoplasmic reticulum and Golgi apparatus. We determined that Icmt and Rce1 processing is required for Rheb localization, but is dispensable for Rheb-induced activation of the mTOR substrate p70 S6 kinase (S6K). Finally, we evaluated whether farnesylthiosalicylic acid (FTS) blocks Rheb localization and function. Surprisingly, FTS prevented S6K activation induced by a constitutively active mTOR mutant, indicating that FTS inhibits mTOR at a level downstream of Rheb. We conclude that inhibitors of Icmt and Rce1 will not block Rheb function, but FTS could be a promising treatment for Rheb- and mTOR-dependent cancers.
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164
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Solanas M, Grau L, Moral R, Vela E, Escrich R, Escrich E. Dietary olive oil and corn oil differentially affect experimental breast cancer through distinct modulation of the p21Ras signaling and the proliferation-apoptosis balance. Carcinogenesis 2009; 31:871-9. [DOI: 10.1093/carcin/bgp243] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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165
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Abstract
Ras proteins activate Raf and PI-3 kinases, as well as exchange factors for RalA and RalB GTPases. Many previous studies have reported that the Ral signaling cascade contributes positively to Ras-mediated oncogenesis. Here, utilizing a bioengineered tissue model of early steps in Ras-induced human squamous cell carcinoma of the skin, we found the opposite. Conversion of Ras-expressing keratinocytes from a premalignant to malignant state induced by decreasing E-cadherin function was associated with and required a knockdown of RalA to a similar degree by shRNA expression in these cells decrease in RalA expression. Moreover, direct ∼2-3 fold knockdown of RalA by shRNA expression in these cells reduced E-cadherin levels and also induced progression to a malignant phenotype. Knockdown of the Ral effector, Exo84, mimicked the effects of decreasing RalA levels in these engineered tissues. These phenomena can be explained by our finding that the stability of E-cadherin in Ras-expressing keratinocytes depends upon this RalA signaling cascade. These results imply that an important component of the early stages in squamous carcinoma progression may be a modest decrease in RalA gene expression that magnifies the effects of decreased E-cadherin expression by promoting its degradation.
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166
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Hu G, Wei Y, Kang Y. The multifaceted role of MTDH/AEG-1 in cancer progression. Clin Cancer Res 2009; 15:5615-20. [PMID: 19723648 DOI: 10.1158/1078-0432.ccr-09-0049] [Citation(s) in RCA: 212] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cancer is the result of the progressive acquisition of multiple malignant traits through the accumulation of genetic or epigenetic alterations. Recent studies have established a functional role of MTDH (Metadherin)/AEG-1 (Astrocyte Elevated Gene 1) in several crucial aspects of tumor progression, including transformation, evasion of apoptosis, invasion, metastasis, and chemoresistance. Overexpression of MTDH/AEG-1 is frequently observed in melanoma, glioma, neuroblastoma, and carcinomas of breast, prostate, liver, and esophagus and is correlated with poor clinical outcomes. MTDH/AEG-1 functions as a downstream mediator of the transforming activity of oncogenic Ha-Ras and c-Myc. Furthermore, MTDH/AEG-1 overexpression activates the PI3K/Akt, nuclear factor kappaB (NFkappaB), and Wnt/beta-catenin signaling pathways to stimulate proliferation, invasion, cell survival, and chemoresistance. The lung-homing domain of MTDH/AEG-1 also mediates the adhesion of tumor cells to the vasculature of distant organs and promotes metastasis. These findings suggest that therapeutic targeting of MTDH/AEG-1 may simultaneously suppress tumor growth, block metastasis, and enhance the efficacy of chemotherapeutic treatments.
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Affiliation(s)
- Guohong Hu
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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167
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Narumiya S, Tanji M, Ishizaki T. Rho signaling, ROCK and mDia1, in transformation, metastasis and invasion. Cancer Metastasis Rev 2009; 28:65-76. [PMID: 19160018 DOI: 10.1007/s10555-008-9170-7] [Citation(s) in RCA: 412] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The Rho subgroup of the Rho GTPases consisting of RhoA, RhoB and RhoC induces a specific type of actin cytoskeleton and carry out a variety of functions in the cell. mDia and ROCK are downstream effectors of Rho mediating Rho action on the actin cytoskeleton; mDia produces actin filaments by nucleation and polymerization and ROCK activate myosin to cross-link them for induction of actomyosin bundles and contractility. mDia is potentially linked to Rac activation and membrane ruffle formation through c-Src-induced phosphorylation of focal adhesion proteins, and ROCK antagonizes this mDia action. Thus, cell morphogenesis, adhesion, and motility can be determined by the balance between mDia and ROCK activities. Though they are not oncogenes by themselves, overexpression of RhoA and RhoC are often found in clinical cancers, and RhoC has been repeatedly identified as a gene associated with metastasis. The Rho-ROCK pathway is implicated in Ras-mediated transformation, the amoeboid movement of tumor cells in the three-dimensional matrix, and transmigration of tumor cells through the mesothelial monolayer. On the other hand, the Rho-mDia1 pathway is implicated in Src-mediated remodeling of focal adhesions and migration of tumor cells. There is also an indication that the Rho pathway other than ROCK is involved in Src-mediated induction of podosome and regulation of matrix metalloproteases. Thus, Rho mediates various phenotypes of malignant transformation by Ras and Src through its effectors, ROCK and mDia.
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Affiliation(s)
- Shuh Narumiya
- Department of Pharmacology, Kyoto University Faculty of Medicine, Kyoto, 606-8501, Japan.
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168
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Li TT, Alemayehu M, Aziziyeh AI, Pape C, Pampillo M, Postovit LM, Mills GB, Babwah AV, Bhattacharya M. Beta-arrestin/Ral signaling regulates lysophosphatidic acid-mediated migration and invasion of human breast tumor cells. Mol Cancer Res 2009; 7:1064-77. [PMID: 19609003 DOI: 10.1158/1541-7786.mcr-08-0578] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The lipid mediator lysophosphatidic acid (LPA) plays a role in cancer progression and signals via specific G protein-coupled receptors, LPA(1-3). LPA has been shown to enhance the metastasis of breast carcinoma cells to bone. However, the mechanisms by which LPA receptors regulate breast cancer cell migration and invasion remain unclear. Breast cancer cell proliferation has been shown to be stimulated by Ral GTPases, a member of the Ras superfamily. Ral activity can be regulated by the multifunctional protein beta-arrestin. We now show that HS578T and MDA-MB-231 breast cancer cells and MDA-MB-435 melanoma cells have higher expression of beta-arrestin 1 mRNA compared with the nontumorigenic mammary MCF-10A cells. Moreover, we found that the mRNA levels of LPA1, LPA2, beta-arrestin 2, and Ral GTPases are elevated in the advanced stages of breast cancer. LPA stimulates the migration and invasion of MDA-MB-231 cells, but not of MCF-10A cells, and this is mediated by pertussis toxin-sensitive G proteins and LPA1. However, ectopic expression of LPA1 in MCF-10A cells caused these cells to acquire an invasive phenotype. Gene knockdown of either beta-arrestin or Ral proteins significantly impaired LPA-stimulated migration and invasion. Thus, our data show a novel role for beta-arrestin/Ral signaling in mediating LPA-induced breast cancer cell migration and invasion, two important processes in metastasis.
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Affiliation(s)
- Timothy T Li
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
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169
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Shirakawa R, Fukai S, Kawato M, Higashi T, Kondo H, Ikeda T, Nakayama E, Okawa K, Nureki O, Kimura T, Kita T, Horiuchi H. Tuberous sclerosis tumor suppressor complex-like complexes act as GTPase-activating proteins for Ral GTPases. J Biol Chem 2009; 284:21580-8. [PMID: 19520869 DOI: 10.1074/jbc.m109.012112] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The small GTPases RalA and RalB are multifunctional proteins regulating a variety of cellular processes. Like other GTPases, the activity of Ral is regulated by the opposing effects of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Although several RalGEFs have been identified and characterized, the molecular identity of RalGAP remains unknown. Here, we report the first molecular identification of RalGAPs, which we have named RalGAP1 and RalGAP2. They are large heterodimeric complexes, each consisting of a catalytic alpha1 or alpha2 subunit and a common beta subunit. These RalGAP complexes share structural and catalytic similarities with the tuberous sclerosis tumor suppressor complex, which acts as a GAP for Rheb. In vitro GTPase assays revealed that recombinant RalGAP1 accelerates the GTP hydrolysis rate of RalA by 280,000-fold. Heterodimerization was required for this GAP activity. In PC12 cells, knockdown of the beta subunit led to sustained Ral activation upon epidermal growth factor stimulation, indicating that the RalGAPs identified here are critical for efficient termination of Ral activation induced by extracellular stimuli. Our identification of RalGAPs will enable further understanding of Ral signaling in many biological and pathological processes.
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Affiliation(s)
- Ryutaro Shirakawa
- Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
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170
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Catimel B, Yin MX, Schieber C, Condron M, Patsiouras H, Catimel J, Robinson DEJE, Wong LSM, Nice EC, Holmes AB, Burgess AW. PI(3,4,5)P3 Interactome. J Proteome Res 2009; 8:3712-26. [DOI: 10.1021/pr900320a] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Bruno Catimel
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Meng-Xin Yin
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Christine Schieber
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Melanie Condron
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Heather Patsiouras
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Jenny Catimel
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Diane E. J. E. Robinson
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Leon S.-M. Wong
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Edouard C. Nice
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Andrew B. Holmes
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Antony W. Burgess
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
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171
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Chia WJ, Tang BL. Emerging roles for Rab family GTPases in human cancer. Biochim Biophys Acta Rev Cancer 2009; 1795:110-6. [PMID: 19425190 DOI: 10.1016/j.bbcan.2008.10.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Member of the Ras-associated binding (Rab) family of small GTPases function as molecular switches regulating vesicular transport in eukaryotes cells. Their pathophysiological roles in human malignancies are less well-known compared to members of Ras and Rho families. Several members of the Rab family have, however, been shown to be aberrantly expressed in various cancer tissues. Recent findings have also revealed , in particular, Rab25 as a determinant of tumor progression and aggressiveness of epithelial cancers. Rab25 associates with alpha5beta1 integrin, and enhances tumor cell invasion by directing the localization of integrin-containing vesicles to the leading edge of matrix invading pseudopodia. We summarized here recent integrin on Rab25 and other Rabs implicated to be involved in a variety of human cancers, and discussed plausible mechanisms of how dysregulation of Rab expression could be tumorigenic or tumor suppressive.
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Affiliation(s)
- Wan Jie Chia
- Department of Biochemistry,Yong Loo Lin School of Medicine, national University of Singapore, 8 Medical Drive, Singapore 117597, Singapore
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172
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Abstract
Ras leads an important signaling pathway that is deregulated in neurofibromatosis type 1 and malignant peripheral nerve sheath tumor (MPNST). In this study, we show that overactivation of Ras and many of its downstream effectors occurred in only a fraction of MPNST cell lines. RalA, however, was overactivated in all MPNST cells and tumor samples compared to nontransformed Schwann cells. Silencing Ral or inhibiting it with a dominant-negative Ral (Ral S28N) caused a significant reduction in proliferation, invasiveness, and in vivo tumorigenicity of MPNST cells. Silencing Ral also reduced the expression of epithelial mesenchymal transition markers. Expression of the NF1-GTPase-related domain (NF1-GRD) diminished the levels of Ral activation, implicating a role for neurofibromin in regulating RalA activation. NF1-GRD treatment caused a significant decrease in proliferation, invasiveness, and cell cycle progression, but cell death increased. We propose Ral overactivation as a novel cell signaling abnormality in MPNST that leads to important biological outcomes with translational ramifications.
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173
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Affiliation(s)
- John M Kyriakis
- Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts 02111, USA.
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174
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The epithelial polarity program: machineries involved and their hijacking by cancer. Oncogene 2008; 27:6939-57. [DOI: 10.1038/onc.2008.345] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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175
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Catimel B, Schieber C, Condron M, Patsiouras H, Connolly L, Catimel J, Nice EC, Burgess AW, Holmes AB. The PI(3,5)P2 and PI(4,5)P2 Interactomes. J Proteome Res 2008; 7:5295-313. [DOI: 10.1021/pr800540h] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bruno Catimel
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Christine Schieber
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Melanie Condron
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Heather Patsiouras
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Lisa Connolly
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Jenny Catimel
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Edouard C. Nice
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Antony W. Burgess
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Andrew B. Holmes
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, Royal Melbourne Hospital, Parkville Victoria 3052, Australia, and School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
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176
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Maehama T, Tanaka M, Nishina H, Murakami M, Kanaho Y, Hanada K. RalA functions as an indispensable signal mediator for the nutrient-sensing system. J Biol Chem 2008; 283:35053-9. [PMID: 18948269 DOI: 10.1074/jbc.m805822200] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cells sense nutrients present in the extracellular environment and modulate the activities of intracellular signaling systems in response to nutrient availability. This study demonstrates that RalA and its activator RalGDS participate in nutrient sensing and are indispensable for activation of mammalian target of rapamycin complex 1 (mTORC1) induced by extracellular nutrients. Knockdown of RalA or RalGDS abolished amino acid- and glucose-induced mTORC1 activation, as judged by phosphorylation of S6 kinase and eukaryotic translation initiation factor 4E-binding protein 1. The amount of GTP-bound RalA increased in response to increased amino acid availability. In addition, RalA knockdown suppressed Rheb-induced S6 kinase phosphorylation, and the constitutively active form of RalA induced mTORC1 activation in the absence of Rheb. These results collectively suggest that RalGDS and RalA act downstream of Rheb and that RalA activation is a crucial step in nutrient-induced mTORC1 activation.
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Affiliation(s)
- Tomohiko Maehama
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo 162-8640, Japan.
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177
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Awasthi S, Singhal SS, Awasthi YC, Martin B, Woo JH, Cunningham CC, Frankel AE. RLIP76 and Cancer. Clin Cancer Res 2008; 14:4372-7. [PMID: 18628450 DOI: 10.1158/1078-0432.ccr-08-0145] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
RLIP76 is a multifunctional membrane protein that transports glutathione conjugates of electrophilic compounds and other xenobiotics including chemotherapy agents out of cells. The protein is overexpressed in lung carcinomas, ovarian carcinomas, and melanomas. The protein also binds Ral and participates in mitotic spindle function, clathrin-dependent endocytosis, and triggers GTPase-activating protein activity. It is found throughout the cell, in membrane, cytosol, and the nucleus, and is known to shift between these compartments in response to stress. Loss of RLIP76 by antibody or antisense therapy is associated with increased sensitivity to radiation and chemotherapy. Conversely, liposomally delivered RLIP may treat poisoning and wounds.
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Affiliation(s)
- Sanjay Awasthi
- Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, Texas, USA
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178
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Spiczka KS, Yeaman C. Ral-regulated interaction between Sec5 and paxillin targets Exocyst to focal complexes during cell migration. J Cell Sci 2008; 121:2880-91. [PMID: 18697830 DOI: 10.1242/jcs.031641] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Changes in cellular behavior that cause epithelial cells to lose adhesiveness, acquire a motile invasive phenotype and metastasize to secondary sites are complex and poorly understood. Molecules that normally function to integrate adhesive spatial information with cytoskeleton dynamics and membrane trafficking probably serve important functions in cellular transformation. One such complex is the Exocyst, which is essential for targeted delivery of membrane and secretory proteins to specific plasma membrane sites to maintain epithelial cell polarity. Upon loss of cadherin-mediated adhesion in Dunning R3327-5'A prostate tumor cells, Exocyst localization shifts from lateral membranes to tips of protrusive membrane extensions. Here, it colocalizes and co-purifies with focal complex proteins that regulate membrane trafficking and cytoskeleton dynamics. These sites are the preferred destination of post-Golgi transport vesicles ferrying biosynthetic cargo, such as alpha(5)-integrin, which mediates adhesion of cells to the substratum, a process essential to cell motility. Interference with Exocyst activity impairs integrin delivery to plasma membrane and inhibits tumor cell motility and matrix invasiveness. Localization of Exocyst and, by extension, targeting of Exocyst-dependent cargo, is dependent on Ral GTPases, which control association between Sec5 and paxillin. Overexpression of Ral-uncoupled Sec5 mutants inhibited Exocyst interaction with paxillin in 5'A cells, as did RNAi-mediated reduction of either RalA or RalB. Reduction of neither GTPase significantly altered steady-state levels of assembled Exocyst in these cells, but did change the observed localization of Exocyst proteins.
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Affiliation(s)
- Krystle S Spiczka
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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179
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Yoshikawa M, Kajiho H, Sakurai K, Minoda T, Nakagawa S, Kontani K, Katada T. Tyr-phosphorylation signals translocate RIN3, the small GTPase Rab5-GEF, to early endocytic vesicles. Biochem Biophys Res Commun 2008; 372:168-72. [PMID: 18486601 DOI: 10.1016/j.bbrc.2008.05.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 05/02/2008] [Indexed: 10/22/2022]
Abstract
The small GTPase Rab5 plays a key role in early endocytic pathway, and its activation requires guanine-nucleotide exchange factors (GEFs). Rab5-GEFs share a conserved VPS9 domain for the GEF action, and RIN3 containing additional domains, such as Src-homology 2, RIN-family homology (RH), and Ras-association (RA), was identified as a new Rab5-GEF. However, precise functions of the additional domains and the activation mechanism of RIN3 remain unknown. Here, we found tyrosine-phosphorylation signals are involved in the Rab5-GEF activation. Treatment of HeLa cells with pervanadate translocates RIN3 from cytoplasm to the Rab5-positive vesicles. This RIN3 translocation was applied to various mutants lacking each domain of RIN3. Our present results suggest that a Ras GTPase(s) activated by tyrosine-phosphorylation signals interacts with the inhibitory RA domain, resulting in an active conformation of RIN3 as a Rab5-GEF and that RIN-unique RH domain constitutes a Rab5-binding region for the progress of GEF action.
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Affiliation(s)
- Manabu Yoshikawa
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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