1
|
Structural basis of the oncogenic KRAS mutant and GJ101 complex. Biochem Biophys Res Commun 2023; 641:27-33. [PMID: 36516586 DOI: 10.1016/j.bbrc.2022.12.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 12/01/2022] [Accepted: 12/06/2022] [Indexed: 12/12/2022]
Abstract
KRAS mutations occur in a quarter of all human cancers. When activated in its GTP-bound form, RAS stimulates diverse cellular systems, such as cell division, differentiation, growth, and apoptosis through the activations of various signaling pathways, which include mitogen-activated protein kinase (MAPK), phosphoinositide 3 kinases (PI3K), and RAL-GEFs pathways. We found that GJ101 (65LYDVA69) binds directly to the KRAS mutant (G12V) and showed tumor-suppressive activity. In addition, the GJ101 peptide inhibited KRAS mutant as determined by a [α-32P] guanosine triphosphate (GTP) binding assay and suppressed pancreatic cell line in a cell proliferation assay. Herein, the complex structure of KRAS and GJ101 was clarified by X-ray crystallography. Isothermal titration calorimetry showed that GJ101 binds highly with KRAS mutant and the complex structure of KRAS G12V.GJ101 complex presented that the residue of Q61 directly interacted with L65 of GJ101. Overall, the results suggest GJ101 be considered a developmental starting point for KRAS G12V inhibitor.
Collapse
|
2
|
Pham G, Shin DM, Kim Y, Kim SH. Ran-GTP/-GDP-dependent nuclear accumulation of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 and TGACG-BINDING FACTOR2 controls salicylic acid-induced leaf senescence. PLANT PHYSIOLOGY 2022; 189:1774-1793. [PMID: 35417014 PMCID: PMC9237681 DOI: 10.1093/plphys/kiac164] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 02/08/2022] [Indexed: 05/11/2023]
Abstract
Leaf senescence is the final stage of leaf development and can be triggered by various external factors, such as hormones and light deprivation. In this study, we demonstrate that the overexpression of the GTP-bound form of Arabidopsis (Arabidopsis thaliana) Ran1 (a Ras-related nuclear small G-protein, AtRan1) efficiently promotes age-dependent and dark-triggered leaf senescence, while Ran-GDP has the opposite effect. Transcriptome analysis comparing AtRan1-GDP- and AtRan1-GTP-overexpressing transgenic plants (Ran1T27Nox and Ran1G22Vox, respectively) revealed that differentially expressed genes (DEGs) related to the senescence-promoting hormones salicylic acid (SA), jasmonic acid, abscisic acid, and ethylene (ET) were significantly upregulated in dark-triggered senescing leaves of Ran1G22Vox, indicating that these hormones are actively involved in Ran-GTP/-GDP-dependent, dark-triggered leaf senescence. Bioinformatic analysis of the promoter regions of DEGs identified diverse consensus motifs, including the bZIP motif, a common binding site for TGACG-BINDING FACTOR (TGA) transcription factors. Interestingly, TGA2 and its interactor, NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (NPR1), which are two positive transcriptional regulators of SA signaling, differed in their extent of accumulation in the nucleus versus cytoplasm of Ran1T27Nox and Ran1G22Vox plants. Moreover, SA-induced, Ran-GTP-/-GDP-dependent functions of NPR1 included genome-wide global transcriptional reprogramming of genes involved in cell death, aging, and chloroplast organization. Furthermore, the expression of AtRan1-GTP in SA signaling-defective npr1 and SA biosynthesis-deficient SA-induction deficient2 genetic backgrounds abolished the effects of AtRan1-GTP, thus retarding age-promoted leaf senescence. However, ET-induced leaf senescence was not mediated by Ran machinery-dependent nuclear shuttling of ETHYLENE-INSENSITIVE3 and ETHYLENE-INSENSITIVE3-LIKE1 proteins. We conclude that Ran-GTP/-GDP-dependent nuclear accumulation of NPR1 and TGA2 represents another regulatory node for SA-induced leaf senescence.
Collapse
Affiliation(s)
| | | | - Yoon Kim
- Division of Biological Science and Technology, Yonsei University, Yonseidae 1 Gil, Wonju-Si 220-710, South Korea
| | | |
Collapse
|
3
|
Han CW, Jeong MS, Ha SC, Jang SB. A H-REV107 Peptide Inhibits Tumor Growth and Interacts Directly with Oncogenic KRAS Mutants. Cancers (Basel) 2020; 12:cancers12061412. [PMID: 32486141 PMCID: PMC7352977 DOI: 10.3390/cancers12061412] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/28/2020] [Accepted: 05/28/2020] [Indexed: 12/12/2022] Open
Abstract
Kirsten-RAS (KRAS) has been the target of drugs because it is the most mutated gene in human cancers. Because of the low affinity of drugs for KRAS mutations, it was difficult to target these tumor genes directly. We found a direct interaction between KRAS G12V and tumor suppressor novel H-REV107 peptide with high binding affinity. We report the first crystal structure of an oncogenic mutant, KRAS G12V-H-REV107. This peptide was shown to interact with KRAS G12V in the guanosine diphosphate (GDP)-bound inactive state and to form a stable complex, blocking the activation function of KRAS. We showed that the peptide acted as an inhibitor of mutant KRAS targets by [α-32P] guanosine triphosphate (GTP) binding assay. The H-REV107 peptide inhibited pancreatic cancer and colon cancer cell lines in cell proliferation assay. Specially, the H-REV107 peptide can suppress pancreatic tumor growth by reduction of tumor volume and weight in xenotransplantation mouse models. Overall, the results presented herein will facilitate development of novel drugs for inhibition of KRAS mutations in cancer patients.
Collapse
Affiliation(s)
- Chang Woo Han
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, 2, Busandaehak-ro 63 beon-gil, Geumjeong-gu, Busan 46241, Korea;
| | - Mi Suk Jeong
- Korea Nanobiotechnology Center, Pusan National University, 2, Busandaehak-ro 63 beon-gil, Geumjeong-gu, Busan 46241, Korea
- Correspondence: (M.S.J.); (S.B.J.); Tel.: +82-51-510-2523 (S.B.J.); Fax: +82-51-581-2544 (S.B.J.)
| | - Sung Chul Ha
- Pohang Accelarator Laboratory, Pohang University of Science and Technology, 80 Jigok-ro 127 beon-gil, Nam-gu, Gyeongsangbuk-do, Pohang-si 37673, Korea;
| | - Se Bok Jang
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, 2, Busandaehak-ro 63 beon-gil, Geumjeong-gu, Busan 46241, Korea;
- Correspondence: (M.S.J.); (S.B.J.); Tel.: +82-51-510-2523 (S.B.J.); Fax: +82-51-581-2544 (S.B.J.)
| |
Collapse
|
4
|
Structural snapshots of RAF kinase interactions. Biochem Soc Trans 2018; 46:1393-1406. [PMID: 30381334 DOI: 10.1042/bst20170528] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 07/25/2018] [Accepted: 07/30/2018] [Indexed: 02/07/2023]
Abstract
RAF (rapidly accelerated fibrosarcoma) Ser/Thr kinases (ARAF, BRAF, and CRAF) link the RAS (rat sarcoma) protein family with the MAPK (mitogen-activated protein kinase) pathway and control cell growth, differentiation, development, aging, and tumorigenesis. Their activity is specifically modulated by protein-protein interactions, post-translational modifications, and conformational changes in specific spatiotemporal patterns via various upstream regulators, including the kinases, phosphatase, GTPases, and scaffold and modulator proteins. Dephosphorylation of Ser-259 (CRAF numbering) and dissociation of 14-3-3 release the RAF regulatory domains RAS-binding domain and cysteine-rich domain for interaction with RAS-GTP and membrane lipids. This, in turn, results in RAF phosphorylation at Ser-621 and 14-3-3 reassociation, followed by its dimerization and ultimately substrate binding and phosphorylation. This review focuses on structural understanding of how distinct binding partners trigger a cascade of molecular events that induces RAF kinase activation.
Collapse
|
5
|
Ke H, Matsumoto S, Murashima Y, Taniguchi-Tamura H, Miyamoto R, Yoshikawa Y, Tsuda C, Kumasaka T, Mizohata E, Edamatsu H, Kataoka T. Structural basis for intramolecular interaction of post-translationally modified H-Ras•GTP prepared by protein ligation. FEBS Lett 2017; 591:2470-2481. [PMID: 28730604 DOI: 10.1002/1873-3468.12759] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 07/09/2017] [Accepted: 07/10/2017] [Indexed: 01/26/2023]
Abstract
Ras undergoes post-translational modifications including farnesylation, proteolysis, and carboxymethylation at the C terminus, which are necessary for membrane recruitment and effector recognition. Full activation of c-Raf-1 requires cooperative interaction of the farnesylated C terminus and the activator region of Ras with its cysteine-rich domain (CRD). However, the molecular basis for this interaction remains unclear because of difficulties in preparing modified Ras in amounts sufficient for structural studies. Here, we use Sortase A-catalyzed protein ligation to prepare modified Ras in sufficient amounts for NMR and X-ray crystallographic analyses. The results show that the farnesylated C terminus establishes an intramolecular interaction with the catalytic domain and brings the farnesyl moiety to the proximity of the activator region, which may be responsible for their cooperative recognition of c-Raf-1-CRD.
Collapse
Affiliation(s)
- Haoliang Ke
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| | - Shigeyuki Matsumoto
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| | - Yosuke Murashima
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| | - Haruka Taniguchi-Tamura
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| | - Ryo Miyamoto
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| | - Yoko Yoshikawa
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| | - Chiemi Tsuda
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| | - Takashi Kumasaka
- Japan Synchrotron Radiation Research Institute (JASRI), Sayo-gun, Hyogo, Japan
| | - Eiichi Mizohata
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan
| | - Hironori Edamatsu
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| | - Tohru Kataoka
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan
| |
Collapse
|
6
|
Margiotti K, Pascolini G, Consoli F, Guida V, Di Bonaventura C, Giallonardo AT, Pizzuti A, De Luca A. Lack of pathogenic mutations in SOS1 gene in phenytoin-induced gingival overgrowth patients. Arch Oral Biol 2017; 80:160-163. [DOI: 10.1016/j.archoralbio.2017.04.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 04/03/2017] [Accepted: 04/04/2017] [Indexed: 11/16/2022]
|
7
|
Owens M, Kivuva E, Quinn A, Brennan P, Caswell R, Lango Allen H, Vaidya B, Ellard S. SOS1 frameshift mutations cause pure mucosal neuroma syndrome, a clinical phenotype distinct from multiple endocrine neoplasia type 2B. Clin Endocrinol (Oxf) 2016; 84:715-9. [PMID: 26708403 DOI: 10.1111/cen.13008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/21/2015] [Accepted: 12/17/2015] [Indexed: 11/27/2022]
Abstract
BACKGROUND Mucosal neuromas, thickened corneal nerves and marfanoid body habitus are characteristic phenotypic features of multiple endocrine neoplasia type 2B (MEN2B) and often provide an early clue to the diagnosis of the syndrome. Rarely, patients present with typical physical features of MEN2B but without associated endocrinopathies (medullary thyroid carcinoma or pheochromocytoma) or a RET gene mutation; this clinical presentation is thought to represent a distinct condition termed 'pure mucosal neuroma syndrome'. METHODS Exome sequencing was performed in two unrelated probands with mucosal neuromas, thickened corneal nerves and marfanoid body habitus, but no MEN2B-associated endocrinopathy or RET gene mutation. Sanger sequencing was performed to confirm mutations detected by exome sequencing and to test in family members and 3 additional unrelated index patients with mucosal neuromas or thickened corneal nerves. RESULTS A heterozygous SOS1 gene frameshift mutation (c.3266dup or c.3248dup) was identified in each proband. Sanger sequencing showed that proband 1 inherited the c.3266dup mutation from his affected mother, while the c.3248dup mutation had arisen de novo in proband 2. Sanger sequencing also identified one further novel SOS1 mutation (c.3254dup) in one of the 3 additional index patients. CONCLUSION Our results demonstrate the existence of pure mucosal neuroma syndrome as a clinical entity distinct from MEN2B that can now be diagnosed by genetic testing.
Collapse
Affiliation(s)
- Martina Owens
- Department of Molecular Genetics, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
| | - Emma Kivuva
- Department of Clinical Genetics, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
| | - Anthony Quinn
- Department of Ophthalmology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
| | - Paul Brennan
- Northern Genetics Service, Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Richard Caswell
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, UK
| | - Hana Lango Allen
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, UK
| | - Bijay Vaidya
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
| | - Sian Ellard
- Department of Molecular Genetics, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, UK
| |
Collapse
|
8
|
Lukman S, Grant BJ, Gorfe AA, Grant GH, McCammon JA. The distinct conformational dynamics of K-Ras and H-Ras A59G. PLoS Comput Biol 2010; 6. [PMID: 20838576 PMCID: PMC2936511 DOI: 10.1371/journal.pcbi.1000922] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 08/06/2010] [Indexed: 02/07/2023] Open
Abstract
Ras proteins regulate signaling cascades crucial for cell proliferation and differentiation by switching between GTP- and GDP-bound conformations. Distinct Ras isoforms have unique physiological functions with individual isoforms associated with different cancers and developmental diseases. Given the small structural differences among isoforms and mutants, it is currently unclear how these functional differences and aberrant properties arise. Here we investigate whether the subtle differences among isoforms and mutants are associated with detectable dynamical differences. Extensive molecular dynamics simulations reveal that wild-type K-Ras and mutant H-Ras A59G are intrinsically more dynamic than wild-type H-Ras. The crucial switch 1 and switch 2 regions along with loop 3, helix 3, and loop 7 contribute to this enhanced flexibility. Removing the gamma-phosphate of the bound GTP from the structure of A59G led to a spontaneous GTP-to-GDP conformational transition in a 20-ns unbiased simulation. The switch 1 and 2 regions exhibit enhanced flexibility and correlated motion when compared to non-transitioning wild-type H-Ras over a similar timeframe. Correlated motions between loop 3 and helix 5 of wild-type H-Ras are absent in the mutant A59G reflecting the enhanced dynamics of the loop 3 region. Taken together with earlier findings, these results suggest the existence of a lower energetic barrier between GTP and GDP states of the mutant. Molecular dynamics simulations combined with principal component analysis of available Ras crystallographic structures can be used to discriminate ligand- and sequence-based dynamic perturbations with potential functional implications. Furthermore, the identification of specific conformations associated with distinct Ras isoforms and mutants provides useful information for efforts that attempt to selectively interfere with the aberrant functions of these species.
Collapse
Affiliation(s)
- Suryani Lukman
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- Bioinformatics Institute, Agency for Science, Technology and Research, Singapore
- * E-mail: (SL); (BJG)
| | - Barry J. Grant
- Department of Chemistry and Biochemistry, Center for Theoretical Biological Physics, University of California San Diego, La Jolla, California, United States of America
- Howard Hughes Medical Institute, University of California San Diego, La Jolla, California, United States of America
- * E-mail: (SL); (BJG)
| | - Alemayehu A. Gorfe
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas, United States of America
| | - Guy H. Grant
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - J. Andrew McCammon
- Department of Chemistry and Biochemistry, Center for Theoretical Biological Physics, University of California San Diego, La Jolla, California, United States of America
- Department of Pharmacology, University of California San Diego, La Jolla, California, United States of America
| |
Collapse
|
9
|
Jang SI, Lee EJ, Hart PS, Ramaswami M, Pallos D, Hart TC. Germ line gain of function with SOS1 mutation in hereditary gingival fibromatosis. J Biol Chem 2007; 282:20245-55. [PMID: 17510059 DOI: 10.1074/jbc.m701609200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutation of human SOS1 is responsible for hereditary gingival fibromatosis type 1, a benign overgrowth condition of the gingiva. Here, we investigated molecular mechanisms responsible for the increased rate of cell proliferation in gingival fibroblasts caused by mutant SOS1 in vitro. Using ectopic expression of wild-type and mutant SOS1 constructs, we found that truncated SOS1 could localize to the plasma membrane, without growth factor stimuli, leading to sustained activation of Ras/MAPK signaling. Additionally, we observed an increase in the magnitude and duration of ERK signaling in hereditary gingival fibromatosis gingival fibroblasts that was associated with phosphorylation of retinoblastoma tumor suppressor protein and the up-regulation of cell cycle regulators, including cyclins C, D, and E and the E2F/DP transcription factors. These factors promote cell cycle progression from G(1) to S phase, and their up-regulation may underlie the increased gingival fibroblast proliferation observed. Selective depletion of wild-type and mutant SOS1 through small interfering RNA demonstrates the link between mutation of SOS1, ERK signaling, cell proliferation rate, and the expression levels of Egr-1 and proliferating cell nuclear antigen. These findings elucidate the mechanisms for gingival overgrowth mediated by SOS1 gene mutation in humans.
Collapse
Affiliation(s)
- Shyh-Ing Jang
- Section of Human and Craniofacial Genetics, National Institute of Dental and Craniofacial Research, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA
| | | | | | | | | | | |
Collapse
|
10
|
Long X, Lin Y, Ortiz-Vega S, Busch S, Avruch J. The Rheb switch 2 segment is critical for signaling to target of rapamycin complex 1. J Biol Chem 2007; 282:18542-18551. [PMID: 17470430 PMCID: PMC3205911 DOI: 10.1074/jbc.m610736200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The small GTPase Rheb is a positive upstream regulator of the target of rapamycin (TOR) complex 1 in mammalian cells and can bind directly to TOR complex 1. To identify the regions of the Rheb surface most critical for signaling to TOR complex 1, we created a set of 26 mutants wherein clusters of 1-5 putative solvent-exposed residues were changed to alanine, ultimately changing 65 residues distributed over the entire Rheb surface. The signaling function of these mutants was assessed by their ability, in comparison to wild type Rheb, to restore the phosphorylation of S6K1(Thr389) when expressed transiently in amino acid-deprived 293T cells. The major finding is that two mutants situated in the Rheb switch 2 segment, Y67A/I69A and I76A/D77A, exhibit a near total loss of function, whereas extensive replacement of the switch 1 segment and other surface residues with alanines causes relatively little disturbance of Rheb rescue of S6K1 from amino acid withdrawal. This is surprising in view of the minimal impact of guanyl nucleotide on Rheb switch 2 configuration. The loss of function Rheb switch 2 mutants are well expressed and exhibit partial agonist function in amino acid-replete cells. They are unimpaired in their ability to bind GTP or mammalian (m)TOR in vivo or in vitro, and the mTOR polypeptides retrieved with these inactive Rheb mutants exhibit kinase activity in vitro comparable with mTOR bound to wild type Rheb. We conclude that Rheb signaling to mTOR in vivo requires a Rheb switch 2-dependent interaction with an element other than the three known polypeptide components of TOR complex 1.
Collapse
Affiliation(s)
- Xiaomeng Long
- Diabetes Unit and Medical Services and the Department of Molecular Biology, Massachusetts General Hospital, and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
| | - Yenshou Lin
- Diabetes Unit and Medical Services and the Department of Molecular Biology, Massachusetts General Hospital, and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
| | - Sara Ortiz-Vega
- Diabetes Unit and Medical Services and the Department of Molecular Biology, Massachusetts General Hospital, and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
| | - Susann Busch
- Diabetes Unit and Medical Services and the Department of Molecular Biology, Massachusetts General Hospital, and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
| | - Joseph Avruch
- Diabetes Unit and Medical Services and the Department of Molecular Biology, Massachusetts General Hospital, and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114.
| |
Collapse
|
11
|
Allen NPC, Donninger H, Vos MD, Eckfeld K, Hesson L, Gordon L, Birrer MJ, Latif F, Clark GJ. RASSF6 is a novel member of the RASSF family of tumor suppressors. Oncogene 2007; 26:6203-11. [PMID: 17404571 DOI: 10.1038/sj.onc.1210440] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
RASSF family proteins are tumor suppressors that are frequently downregulated during the development of human cancer. The best-characterized member of the family is RASSF1A, which is downregulated by promoter methylation in 40-90% of primary human tumors. We now identify and characterize a novel member of the RASSF family, RASSF6. Like the other family members, RASSF6 possesses a Ras Association domain and binds activated Ras. Exogenous expression of RASSF6 promoted apoptosis, synergized with activated K-Ras to induce cell death and inhibited the survival of specific tumor cell lines. Suppression of RASSF6 enhanced the tumorigenic phenotype of a human lung tumor cell line. Furthermore, RASSF6 is often downregulated in primary human tumors. RASSF6 shares some similar overall properties as other RASSF proteins. However, there are significant differences in biological activity between RASSF6 and other family members including a discrete tissue expression profile, cell killing specificity and impact on signaling pathways. Moreover, RASSF6 may play a role in dictating the degree of inflammatory response to the respiratory syncytial virus. Thus, RASSF6 is a novel RASSF family member that demonstrates the properties of a Ras effector and tumor suppressor but exhibits biological properties that are unique and distinct from those of other family members.
Collapse
Affiliation(s)
- N P C Allen
- Department of Cell and Cancer Biology, National Cancer Institute, Rockville, MD, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Abstract
Ras genes are the most common targets for somatic gain-of-function mutations in human cancer. Recently, germline mutations that affect components of the Ras-Raf-mitogen-activated and extracellular-signal regulated kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) pathway were shown to cause several developmental disorders, including Noonan, Costello and cardio-facio-cutaneous syndromes. Many of these mutant alleles encode proteins with aberrant biochemical and functional properties. Here we will discuss the implications of germline mutations in the Ras-Raf-MEK-ERK pathway for understanding normal developmental processes and cancer pathogenesis.
Collapse
Affiliation(s)
- Suzanne Schubbert
- Department of Pediatrics, University of California, 513 Parnassus Avenue, Room HSE-302, San Francisco, California 94143, USA
| | | | | |
Collapse
|
13
|
Elam C, Hesson L, Vos MD, Eckfeld K, Ellis CA, Bell A, Krex D, Birrer MJ, Latif F, Clark GJ. RRP22 is a farnesylated, nucleolar, Ras-related protein with tumor suppressor potential. Cancer Res 2005; 65:3117-25. [PMID: 15833841 DOI: 10.1158/0008-5472.can-04-0749] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ras proteins are members of a superfamily of related small GTPases. Some members, such as Ras, are oncogenic. However, other members seem to serve as tumor suppressors, such as Rig and Noey2. We now identify and characterize a novel member of the Ras superfamily, RRP22. Like Ras, RRP22 can be posttranslationally modified by farnesyl. Unlike Ras, RRP22 inhibits cell growth and promotes caspase-independent cell death. Examination of human tumor cells shows that RRP22 is frequently down-regulated due to promoter methylation. Moreover, reexpression of RRP22 in an RRP22-negative neural tumor cell line impairs its growth in soft agar. Unusually for a Ras-related protein, RRP22 localizes to the nucleolus in a GTP-dependent manner, suggesting a novel mechanism of action. Thus, we identify a new member of the Ras superfamily that can serve as a potential tumor suppressor.
Collapse
Affiliation(s)
- Candice Elam
- Department of Cell and Cancer Biology, National Cancer Institute, 9610 Medical Center Drive, Rockville, MD 20820, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Nevins AK, Thurmond DC. A direct interaction between Cdc42 and vesicle-associated membrane protein 2 regulates SNARE-dependent insulin exocytosis. J Biol Chem 2004; 280:1944-52. [PMID: 15537656 DOI: 10.1074/jbc.m409528200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In pancreatic beta cells, insulin granule exocytosis is regulated by SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor protein (SNAP) receptor) proteins, and this is coupled to cortical F-actin reorganization via the Rho family GTPase Cdc42 by an unknown mechanism. We investigated interactions among the target SNARE protein Syntaxin 1A and the vesicle-associated membrane SNARE protein (VAMP2) with Cdc42 and compared these structural interactions with their functional importance to glucose-stimulated insulin secretion in MIN6 beta cells. Subcellular fractionation analyses revealed a parallel redistribution of Cdc42 and VAMP2 from the granule fraction to the plasma membrane in response to glucose that temporally corresponded with the glucose-induced activation of Cdc42. Moreover, within these fractions Cdc42 and VAMP2 were found to co-immunoprecipitate under basal and glucose-stimulated conditions, suggesting that they moved as a complex. Furthermore, VAMP2 bound both GST-Cdc42-GTPgammaS and GST-Cdc42-GDP, indicating that the Cdc42-VAMP2 complex could form under both cytosolic GDP-bound Cdc42 and plasma membrane GTP-bound Cdc42 conformational conditions. In vitro binding analyses showed that VAMP2 bound directly to Cdc42 and that a heterotrimeric complex with Syntaxin 1A could also be formed. Deletion analyses of VAMP2 revealed that only the N-terminal 28 residues were required for Cdc42 binding. Expression of this 28-residue VAMP2 peptide in MIN6 beta cells resulted in the specific impairment of glucose-stimulated insulin secretion, indicating a functional importance for the Cdc42-VAMP2 interaction. Taken together, these data suggest a mechanism whereby glucose activates Cdc42 to induce the targeting of intracellular Cdc42-VAMP2-insulin granule complexes to Syntaxin 1A at the plasma membrane.
Collapse
Affiliation(s)
- Angela K Nevins
- Department of Biochemistry and Molecular Biology and the Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
| | | |
Collapse
|
15
|
Taira K, Umikawa M, Takei K, Myagmar BE, Shinzato M, Machida N, Uezato H, Nonaka S, Kariya KI. The Traf2- and Nck-interacting kinase as a putative effector of Rap2 to regulate actin cytoskeleton. J Biol Chem 2004; 279:49488-96. [PMID: 15342639 DOI: 10.1074/jbc.m406370200] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rap2 belongs to the Ras family of small GTP-binding proteins, but its specific roles in cell signaling remain unknown. In the present study, we have affinity-purified from rat brain a Rap2-interacting protein of approximately 155 kDa, p155. By liquid chromatography tandem mass spectrometry, we have identified p155 as Traf2- and Nck-interacting kinase (TNIK). TNIK possesses an N-terminal kinase domain homologous to STE20, the Saccharomyces cerevisiae mitogen-activated protein kinase kinase kinase kinase, and a C-terminal regulatory domain termed the citron homology (CNH) domain. TNIK induces disruption of F-actin structure, thereby inhibiting cell spreading. In addition, TNIK specifically activates the c-Jun N-terminal kinase (JNK) pathway. Among our observations, TNIK interacted with Rap2 through its CNH domain but did not interact with Rap1 or Ras. TNIK interaction with Rap2 was dependent on the intact effector region and GTP-bound configuration of Rap2. When co-expressed in cultured cells, TNIK colocalized with Rap2, while a mutant TNIK lacking the CNH domain did not. Rap2 potently enhanced the inhibitory function of TNIK against cell spreading, but this was not observed for the mutant TNIK lacking the CNH domain. Rap2 did not significantly enhance TNIK-induced JNK activation, but promoted autophosphorylation and translocation of TNIK to the detergent-insoluble cytoskeletal fraction. These results suggest that TNIK is a specific effector of Rap2 to regulate actin cytoskeleton.
Collapse
Affiliation(s)
- Kiyohito Taira
- Division of Cell Biology, Graduate School of Medicine, University of the Ryukyus, 207 Uehara, Nishihara-cho, Okinawa 903-0215, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Hwang SL, Hong YR, Sy WD, Lieu AS, Lin CL, Lee KS, Howng SL. Rac1 gene mutations in human brain tumours. Eur J Surg Oncol 2004; 30:68-72. [PMID: 14736526 DOI: 10.1016/j.ejso.2003.10.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
AIMS Rac1 is a member of the Ras superfamily of small GTPase and plays a fundamental role in cytoskeleton reorganization, regulation of gene expression and cell proliferation, and cellular transformation. Though recent studies point to an involvement of rac1 in tumorigenesis, little is known about the alteration of rac1 gene in human brain tumours. METHODS Reverse transcription-polymerase chain reaction (RT-PCR), TA cloning, and DNA sequencing were performed to detect rac1 gene mutations in the surgical specimens of 45 human brain tumours. RESULTS Twelve of 45 cases had base changes in the rac1 gene. The frequency of rac1 alterations was seven of 18 meningiomas, three of 14 astrocytomas, one of seven pituitary adenomas, and one of four metastatic brain tumours. No mutation was detected in acoustic neurilemomas. The subtypes of seven meningiomas include three meningotheliomatous, two atypical, one transitional and one angioblastic meningioma. Three astrocytomas had rac1 gene mutation, including one grade II, one grade III, and one grade IV astrocytoma. All of single base changes were transitions, five of them being T to C transitions. Sites of rac1 mutation were found in codons 34, 41 (two cases), 42 (two cases), 43, 44, 46 and 58. These mutations are mainly localized in the putative effector-domain of rac1 gene and may enhance the activity of rac1, which increases the survival of brain tumours. CONCLUSION Our results suggest that rac1 gene may play a role in some brain tumours of divergent histogenesis and that the alterations of rac1 gene may contribute to tumorigenesis and/or metastasis.
Collapse
Affiliation(s)
- S L Hwang
- Division of Neurosurgery, Kaohsiung Medical University Hospital, 100 Shih Chuan 1st Road, 80708 Kaohsiung, Taiwan, ROC
| | | | | | | | | | | | | |
Collapse
|
17
|
Agarwal M, Nelson DJ, Larochelle DA. The three-dimensional model of Dictyostelium discoideum racE based on the human rhoA-GDP crystal structure. J Mol Graph Model 2002; 21:3-18. [PMID: 12413026 DOI: 10.1016/s1093-3263(01)00137-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The three-dimensional structure of racE was modeled using several homologous small G proteins, and the best model obtained using the human rhoA as modeling template is reported. The three-dimensional fold of the racE model is remarkably similar to the cellular form of human ras p21 crystal structure. Its secondary structure consists of six alpha-helices, six beta-strands and three 3(10) helices. The model retains its secondary structure after a 300 K, 300 ps molecular dynamics (MD) simulation. Important domains of the protein include its effector loop (residues 34-46), the insertion domain (residues 121-136), and the polybasic motif (between 210 and 220) not modeled in the current structure. The effector loop is inherently flexible and the structure docked with GDP exhibits the effector loop moving significantly closer to the nucleotide binding pocket, forming a tighter complex with the bound GDP. The mobility of the effector loop is conferred by a single residue 'hinge' point at residue 34Asp, also allowing the Switch I region, immediately preceding the effector loop, to be equally mobile. In comparison, the Switch II region shows average mobility. The insertion domain is highly flexible, with the insertion taking the form of a helical domain, with several charged residues forming a complex charged interface over the entire insertion region. While the GDP moiety is loosely held in the active site, the metal cation is extensively co-ordinated. The critical residue 38Thr exhibits high mobility, and is seen interacting directly with the metal ion at a distance of 2.64 A, and indirectly via an intervening water molecule. 64Gln, a key residue involved in GTP hydrolysis in ras, is seen facing the beta-phosphate group and the metal ion. Certain residues (i.e. 51Asn, 38Thr and 65Glu) exhibit unique characteristics and these residues, together with 158Val, may play important roles in the maintenance of the protein's integrity and function. There is strong consensus of secondary structural elements between models generated using various templates, such as h-rac1, h-rhoA and h-cdc42 bound to RhoGDI, all sharing only 50-55% sequence identity with racE, which suggests that this model is in all probability an accurate prediction of the true tertiary structure of racE.
Collapse
Affiliation(s)
- Madhavi Agarwal
- Department of Biology, Clark University, Worcester, MA 01610, USA.
| | | | | |
Collapse
|
18
|
Hughes PE, Oertli B, Hansen M, Chou FL, Willumsen BM, Ginsberg MH. Suppression of integrin activation by activated Ras or Raf does not correlate with bulk activation of ERK MAP kinase. Mol Biol Cell 2002; 13:2256-65. [PMID: 12134066 PMCID: PMC117310 DOI: 10.1091/mbc.01-10-0480] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The rapid modulation of ligand-binding affinity ("activation") is a central property of the integrin family of cell adhesion receptors. The Ras family of small GTP-binding proteins and their downstream effectors are key players in regulating integrin activation. H-Ras can suppress integrin activation in fibroblasts via its downstream effector kinase, Raf-1. In contrast, to H-Ras, a closely related small GTP-binding protein R-Ras has the opposite activity, and promotes integrin activation. To gain insight into the regulation of integrin activation by Ras GTPases, we created a series of H-Ras/R-Ras chimeras. We found that a 35-amino acid stretch of H-Ras was required for full suppressive activity. Furthermore, the suppressive chimeras were weak activators of the ERK1/2 MAP kinase pathway, suggesting that the suppression of integrin activation may be independent of the activation of the bulk of ERK MAP kinase. Additional data demonstrating that the ability of H-Ras or Raf-1 to suppress integrin activation was unaffected by inhibition of bulk ERK1/2 MAP kinase activation supported this hypothesis. Thus, the suppression of integrin activation is a Raf kinase induced regulatory event that can be mediated independently of bulk activation of the ERK MAP-kinase pathway.
Collapse
Affiliation(s)
- Paul E Hughes
- The Division of Vascular Biology, Department of Cell Biology. The Scripps Research Institute, La Jolla, California 92037, USA
| | | | | | | | | | | |
Collapse
|
19
|
Murphy GA, Graham SM, Morita S, Reks SE, Rogers-Graham K, Vojtek A, Kelley GG, Der CJ. Involvement of phosphatidylinositol 3-kinase, but not RalGDS, in TC21/R-Ras2-mediated transformation. J Biol Chem 2002; 277:9966-75. [PMID: 11788587 DOI: 10.1074/jbc.m109059200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Oncogenic Ras and activated forms of the Ras-related protein TC21/R-Ras2 share similar abilities to alter cell proliferation. However, in contrast to Ras, we found previously that TC21 fails to activate the Raf-1 serine/threonine kinase. Thus, TC21 must utilize non-Raf effectors to regulate cell function. In this study, we determined that TC21 interacts strongly with some (RalGDS, RGL, RGL2/Rlf, AF6, and the phosphatidylinositol 3-kinase (PI3K) catalytic subunit p110delta), and weakly with other Ras small middle dotGTP-binding proteins. In addition, library screening identified novel TC21-interacting proteins. We also determined that TC21, similar to Ras, mediates activation of phospholipase Cepsilon. We then examined if RalGDS, a RalA guanine nucleotide exchange factor, or PI3K are effectors for TC21-mediated signaling and cell proliferation in murine fibroblasts. We found that overexpression of full-length RalGDS reduced the focus forming activity of activated TC21. Furthermore, expression of activated Ras, but not TC21, enhanced GTP loading on RalA. In fact, TC21 attenuated insulin-stimulated RalA small middle dotGTP formation. In contrast, like Ras, expression of activated TC21 resulted in membrane translocation and an increase in the PI3K-dependent phosphorylation of Akt, and inhibition of PI3K activity interfered with TC21 focus formation. Finally, unlike Ras, TC21 did not activate the Rac small GTPase, indicating that Ras may not activate Rac by PI3K. Taken together, these results suggest that PI3K, but not RalGDS, is an important mediator of cell proliferation by TC21.
Collapse
Affiliation(s)
- Gretchen A Murphy
- Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-7295, USA.
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Khokhlatchev A, Rabizadeh S, Xavier R, Nedwidek M, Chen T, Zhang XF, Seed B, Avruch J. Identification of a novel Ras-regulated proapoptotic pathway. Curr Biol 2002; 12:253-65. [PMID: 11864565 DOI: 10.1016/s0960-9822(02)00683-8] [Citation(s) in RCA: 287] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
BACKGROUND The Ras-GTPase controls cell fate decisions through the binding of an array of effector molecules, such as Raf and PI 3-kinase, in a GTP-dependent manner. NORE1, a noncatalytic polypeptide, binds specifically to Ras-GTP and to several other Ras-like GTPases. NORE is homologous to the putative tumor suppressor RASSF1 and to the Caenorhabditis elegans polypeptide T24F1.3. RESULTS We find that all three NORE-related polypeptides bind selectively to the proapoptotic protein kinase MST1, a member of the Group II GC kinases. Endogenous NORE and MST1 occur in a constitutive complex in vivo that associates with endogenous Ras after serum stimulation. Targeting recombinant MST1 to the membrane, either through NORE or myristoylation, augments the apoptotic efficacy of MST1. Overexpression of constitutively active Ki-RasG12V promotes apoptosis in a variety of cell lines; Ha-RasG12V is a much less potent proapoptotic agent; however, a Ha-RasG12V effector loop mutant (E37G) that binds NORE, but not Raf or PI 3-kinase, exhibits proapoptotic efficacy approaching that of Ki-RasG12V. The apoptotic action of both Ki-RasG12V and Ha-RasG12V, E37G is suppressed by overexpression of the MST1 carboxy-terminal noncatalytic segment or by the NORE segment that binds MST1. CONCLUSIONS MST1 is a phylogenetically conserved partner of the NORE/RASSF polypeptide family, and the NORE-MST1 complex is a novel Ras effector unit that mediates the apoptotic effect of Ki-RasG12V.
Collapse
Affiliation(s)
- Andrei Khokhlatchev
- Diabetes Unit and Medical Services, Massachusetts General Hospital, Boston, MA 02114, USA
| | | | | | | | | | | | | | | |
Collapse
|
21
|
Ramírez de Molina A, Penalva V, Lucas L, Lacal JC. Regulation of choline kinase activity by Ras proteins involves Ral-GDS and PI3K. Oncogene 2002; 21:937-46. [PMID: 11840339 DOI: 10.1038/sj.onc.1205144] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2001] [Revised: 10/19/2001] [Accepted: 10/31/2001] [Indexed: 11/09/2022]
Abstract
Ras proteins are molecular switches that control signaling pathways critical in the onset of a variety of human cancers. The signaling pathways activated by Ras proteins are those controlled by its direct effectors such as the serine-threonine protein kinase Raf-1, the exchange factor for other GTPases Ral-GDS, and the lipid kinase PI3K. As a consequence of Ras activation, a number of additional enzymes are affected, including several members of the serine-threonine intracellular proteins kinases as well as enzymes related to phospholipid metabolism regulation such as phospholipases A2 and D, and choline kinase. The precise mechanisms by which ras oncogenes impinge into these later molecules and their relevance to the onset of the carcinogenic process is still not fully understood. Here we have investigated the mechanism of regulation of choline kinase by Ras proteins and found no direct link between PLD and choline kinase activation. We provide evidence that Ras proteins regulate the activity of choline kinase through its direct effectors Ral-GDS and PI3K, while the Raf pathways seems to be not relevant in this process. The importance of Ras-dependent activation of choline kinase is discussed.
Collapse
Affiliation(s)
- Ana Ramírez de Molina
- Instituto de Investigaciones Biomédicas, CSIC, Arturo Duperier 4, 28029 Madrid, Spain
| | | | | | | |
Collapse
|
22
|
Soares TA, Miller JH, Straatsma TP. Revisiting the structural flexibility of the complex p21(ras)-GTP: the catalytic conformation of the molecular switch II. Proteins 2001; 45:297-312. [PMID: 11746677 DOI: 10.1002/prot.1150] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The hydrolysis of GTP in p21(ras) triggers conformational changes that regulate the ras/ERK signaling pathway. An important active site residue is Gln61, which has been found to be mutated in 30% of human tumors. The dynamics of the active site conformation is studied by using molecular dynamics simulation of two independent structures of the GTP-bound uncomplexed enzyme. Two distinct conformations of the enzyme are observed, in which the side-chain residue Gln61 is in different orientations. Essential dynamics analysis is used to describe the essential motions in the transition between the two conformations. Results are compared with earlier simulations of p21(ras) and its complex with GTPase activating protein p21-GAP.
Collapse
Affiliation(s)
- T A Soares
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | | | | |
Collapse
|
23
|
Rotchell JM, Lee JS, Chipman JK, Ostrander GK. Structure, expression and activation of fish ras genes. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2001; 55:1-21. [PMID: 11551618 DOI: 10.1016/s0166-445x(01)00214-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Ras genes encode proteins that play a central role in cell growth signaling cascades. The fish ras genes characterized to date, have a high degree of nucleotide sequence and deduced amino acid similarity with the mammalian ras gene counterparts. A large proportion and wide variety of mammalian tumors possess mutant forms of ras. In such cases, the localization of ras mutations has been restricted to exons I and II, and to codons 12, 13 and 61. Experimental exposure of fish to a range of genotoxic compounds has similarly led to the production of a ras mutational profile for selected species. The inducing compound, tissue investigated and the fish species studied affect the ras mutational spectrum and incidence observed, despite the apparent conserved sequence homology. Furthermore, the fish ras mutational profile differs from that observed in rodent models, including a novel codon (16) mutation. The role of ras genes in tumor formation in feral fish has been investigated using several species collected from areas of high hydrocarbon contamination. Tomcod (Microgadus tomcod), winter flounder (Pseudopleuronectes americanus) and dragonet (Callionymus lyra) liver samples display evidence of ras gene mutations, though for the latter species the codon affected is not characteristic of ras gene mutational profiles. English sole (Pleuronectes vetulus) and European flounder (Platichthys flesus) liver tumor samples so far examined, on the other hand, do not display ras gene mutations. Thus, the pattern and incidence of ras gene mutations in environmentally-induced tumors also appear to be species specific. In determining the basis of both the species susceptibility observed in the field and species differences in effects of laboratory controlled exposures, the interaction of fish ras genes with other components of the cell growth signaling cascade (such as protein kinase C, additional oncogenes and tumor suppressor genes) are discussed. The effect of promoting agents following contaminant-induced initiation could similarly provide answers in unraveling the question of species susceptibility.
Collapse
Affiliation(s)
- J M Rotchell
- Centre for Environmental Research, School of Chemistry, Physics and Environmental Science, University of Sussex, Falmer, Brighton BN1 9QJ, UK
| | | | | | | |
Collapse
|
24
|
Yang W, Tabancay AP, Urano J, Tamanoi F. Failure to farnesylate Rheb protein contributes to the enrichment of G0/G1 phase cells in the Schizosaccharomyces pombe farnesyltransferase mutant. Mol Microbiol 2001; 41:1339-47. [PMID: 11580838 DOI: 10.1046/j.1365-2958.2001.02599.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Protein farnesylation is important for a number of physiological processes, including proliferation and cell morphology. The Schizosaccharomyces pombe mutant, cpp1-, defective in farnesylation, exhibits distinct phenotypes, including morphological changes and sensitivity to the arginine analogue, canavanine. In this work, we report a novel phenotype of this mutant, enrichment of G0/G1 phase cells. This phenotype results mainly from the inability to farnesylate the Rheb G-protein, as normal cell cycle progression can be restored to the mutant by expressing a mutant form of SpRheb (SpRheb-CVIL) that can bypass farnesylation. In contrast, a farnesylation-defective mutant of SpRheb (SpRheb-SVIA) is incapable of restoring the normal cell cycle profile to the cpp1- mutant. Inhibition of SpRheb expression leads to the accumulation of cells at the G0/G1 phase of the cell cycle. This growth arrest phenotype of the sprheb- disruption can be complemented by the introduction of wild-type sprheb+. The complementation is dependent on farnesylation, as the farnesylation-defective SpRheb-SVIA mutant is incapable of complementing the sprheb- disruption. Other mutants of SpRheb, E40K and S20N, are also incapable of complementing the sprheb- disruption. Furthermore, efficient complementation can be obtained by the expression of human Rheb but not Saccharomyces cerevisiae Rheb. Our findings suggest that protein farnesylation is important for cell cycle progression of S. pombe cells and that farnesylated SpRheb is critical in this process.
Collapse
Affiliation(s)
- W Yang
- Department of Microbiology and Molecular Genetics, Jonsson Comprehensive Cancer Center, Molecular Biology Institute, University of California, Los Angeles, 1602 Molecular Sciences Bldg, 405 Hilgard Ave., Los Angeles, CA 90095-1489, USA
| | | | | | | |
Collapse
|
25
|
Zang M, Waelde CA, Xiang X, Rana A, Wen R, Luo Z. Microtubule integrity regulates Pak leading to Ras-independent activation of Raf-1. insights into mechanisms of Raf-1 activation. J Biol Chem 2001; 276:25157-65. [PMID: 11274179 DOI: 10.1074/jbc.m100152200] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Growth factors activate Raf-1 by engaging a complex program, which requires Ras binding, membrane recruitment, and phosphorylation of Raf-1. The present study employs the microtubule-depolymerizing drug nocodazole as an alternative approach to explore the mechanisms of Raf activation. Incubation of cells with nocodazole leads to activation of Pak1/2, kinases downstream of small GTPases Rac/Cdc42, which have been previously indicated to phosphorylate Raf-1 Ser(338). Nocodazole-induced stimulation of Raf-1 is augmented by co-expression of small GTPases Rac/Cdc42 and Pak1/2. Dominant negative mutants of these proteins block activation of Raf-1 by nocodazole, but not by epidermal growth factor (EGF). Thus, our studies define Rac/Cdc42/Pak as a module upstream of Raf-1 during its activation by microtubule disruption. Although it is Ras-independent, nocodazole-induced activation of Raf-1 appears to involve the amino-terminal regulatory region in which the integrity of the Ras binding domain is required. Surprisingly, the Raf zinc finger mutation (C165S/C168S) causes a robust activation of Raf-1 by nocodazole, whereas it diminishes Ras-dependent activation of Raf-1. We also show that mutation of residues Ser(338) to Ala or Tyr(340)-Tyr(341) to Phe-Phe immediately amino-terminal to the catalytic domain abrogates activation of both the wild type and zinc finger mutant Raf by both EGF/4beta-12-O-tetradecanoylphorbol-13-acetate and nocodazole. Finally, an in vitro kinase assay demonstrates that the zinc finger mutant serves as a better substrate of Pak1 than the wild type Raf-1. Collectively, our results indicate that 1) the zinc finger exerts an inhibitory effect on Raf-1 activation, probably by preventing phosphorylation of (338)SSYY(341); 2) such inhibition is first overcome by an unknown factor binding in place of Ras-GTP to the amino-terminal regulatory region in response to nocodazole; and 3) EGF and nocodazole utilize different kinases to phosphorylate Ser(338), an event crucial for Raf activation.
Collapse
Affiliation(s)
- M Zang
- Diabetes and Metabolism Research Unit, Endocrinology Section, Evans Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA
| | | | | | | | | | | |
Collapse
|
26
|
Song C, Hu CD, Masago M, Kariyai K, Yamawaki-Kataoka Y, Shibatohge M, Wu D, Satoh T, Kataoka T. Regulation of a novel human phospholipase C, PLCepsilon, through membrane targeting by Ras. J Biol Chem 2001; 276:2752-7. [PMID: 11022048 DOI: 10.1074/jbc.m008324200] [Citation(s) in RCA: 264] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Phosphoinositide-specific phospholipase C (PI-PLC) plays a pivotal role in regulation of intracellular signal transduction from various receptor molecules. More than 10 members of human PI-PLC isoforms have been identified and classified into three classes beta, gamma, and delta, which are regulated by distinct mechanisms. Here we report identification of a novel class of human PI-PLC, named PLCepsilon, which is characterized by the presence of a Ras-associating domain at its C terminus and a CDC25-like domain at its N terminus. The Ras-associating domain of PLCepsilon specifically binds to the GTP-bound forms of Ha-Ras and Rap1A. The dissociation constant for Ha-Ras is estimated to be approximately 40 nm, comparable with those of other Ras effectors. Co-expression of an activated Ha-Ras mutant with PLCepsilon induces its translocation from the cytosol to the plasma membrane. Upon stimulation with epidermal growth factor, similar translocation of ectopically expressed PLCepsilon is observed, which is inhibited by co-expression of dominant-negative Ha-Ras. Furthermore, using a liposome-based reconstitution assay, it is shown that the phosphatidylinositol 4,5-bisphosphate-hydrolyzing activity of PLCepsilon is stimulated in vitro by Ha-Ras in a GTP-dependent manner. These results indicate that Ras directly regulates phosphoinositide breakdown through membrane targeting of PLCepsilon.
Collapse
Affiliation(s)
- C Song
- Department of Physiology II, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Pal S, Datta K, Khosravi-Far R, Mukhopadhyay D. Role of protein kinase Czeta in Ras-mediated transcriptional activation of vascular permeability factor/vascular endothelial growth factor expression. J Biol Chem 2001; 276:2395-403. [PMID: 11060301 DOI: 10.1074/jbc.m007818200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF), a multifunctional cytokine, is regulated by different factors including degree of cell differentiation, hypoxia, and certain oncogenes namely, ras and src. The up-regulation of VPF/VEGF expression by Ras has been found to be through both transcription and mRNA stability. The present study investigates a novel pathway whereby Ras promotes the transcription of VPF/VEGF by activating protein kinase Czeta (PKCzeta). The Ras-mediated overexpression of VPF/VEGF was also found to be inhibited by using the antisense or the dominant-negative mutant of PKCzeta. In co-transfection assays, by overexpressing oncogenic Ha-Ras (12 V) and PKCzeta, there was an additive effect up to 4-fold in activation of Sp1-mediated VPF/VEGF transcription. It has been shown through electrophoretic mobility shift assay that Ras promoted the PKCzeta-induced binding of Sp1 to the VPF/VEGF promoter. In the presence of PDK-1, a major activating kinase for PKC, the Ras-mediated activation of VPF/VEGF promoter through PKCzeta was further increased, suggesting that PKCzeta can serve as an effector for both Ras and PDK-1. In other experiments, with the use of a dominant-negative mutant of phosphatidylinositol 3-kinase, the activation of VPF/VEGF promoter through Ras, PDK-1, and PKCzeta was completely repressed, indicating phosphatidylinositol 3-kinase as an important component of this pathway. Taken together, these data elucidate the signaling mechanism of Ras-mediated VPF/VEGF transcriptional activation through PKCzeta and also provide insight into PKCzeta and Sp1-dependent transcriptional regulation of VPF/VEGF.
Collapse
Affiliation(s)
- S Pal
- Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
| | | | | | | |
Collapse
|
28
|
Farrar CT, Ma J, Singel DJ, Halkides CJ. Structural changes induced in p21Ras upon GAP-334 complexation as probed by ESEEM spectroscopy and molecular-dynamics simulation. Structure 2000; 8:1279-87. [PMID: 11188692 DOI: 10.1016/s0969-2126(00)00532-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND The means by which the protein GAP accelerates GTP hydrolysis, and thereby downregulates growth signaling by p21Ras, is of considerable interest, particularly inasmuch as p21 mutants are implicated in a number of human cancers. A GAP "arginine finger," identified by X-ray crystallography, has been suggested as playing the principal role in the GTP hydrolysis. Mutagenesis studies, however, have shown that the arginine can only partially account for the 10(5)-fold increase in the GAP-accelerated GTPase rate of p21. RESULTS We report electron spin-echo envelope modulation (ESEEM) studies of GAP-334 complexed with GMPPNP bound p21 in frozen solution, together with molecular-dynamics simulations. Our results indicate that, in solution, the association of GAP-334 with GTP bound p21 induces a conformational change near the metal ion active site of p21. This change significantly reduces the distances from the amide groups of p21 glycine residues 60 and 13 to the divalent metal ion. CONCLUSIONS The movement of glycine residues 60 and 13 upon the binding of GAP-334 in solution provides a physical basis to interpret prior mutagenesis studies, which indicated that Gly-60 and Gly-13 of p21 play important roles in the GAP-dependent GTPase reaction. Gly-60 and Gly-13 may play direct catalytic roles and stabilize the attacking water molecule and beta,gamma-bridging oxygen, respectively, in p21. The amide proton of Gly-60 could also play an indirect role in catalysis by supplying a crucial hydrogen bonding interaction that stabilizes loop L4 and therefore the position of other important catalytic residues.
Collapse
Affiliation(s)
- C T Farrar
- Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138, USA
| | | | | | | |
Collapse
|
29
|
Urasaki N, Tokumoto M, Terauchi R, Tarora K, Chinen I, Ban Y, Kayano T, Tanaka H. cDNA cloning and molecular analysis of papaya small GTP-binding protein, pgp1. Genes Genet Syst 2000; 75:293-8. [PMID: 11245222 DOI: 10.1266/ggs.75.293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
In the course of papaya EST collection, one clone (pRA4-3) encoding partial sequence of papaya small GTP-binding protein gene, pgp1, was obtained. Based on the sequence information of pRA4-3, the entire coding region of pgp1 was cloned using the 3'RACE PCR technique. ORF of pgp1 is 636bp long and deduced molecular weight of the protein is 23,311. Phylogenetic analysis showed that PGP1 belongs to YPT/RAB group of the small GTP-binding protein and is a homologue of RAB2. Southern analysis showed that there are several pgp1-related genes in papaya genome. Northern analysis showed that pgp1 was expressed equally in stems of seedlings that were grown under light and dark conditions. This result shows that PGP1 is not involved in the phytochrome-mediated signal transduction as an auxin signal transducer in stems of papaya seedlings.
Collapse
Affiliation(s)
- N Urasaki
- Iwate Biotechnology Research Center, Kitakami, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
30
|
Urano J, Tabancay AP, Yang W, Tamanoi F. The Saccharomyces cerevisiae Rheb G-protein is involved in regulating canavanine resistance and arginine uptake. J Biol Chem 2000; 275:11198-206. [PMID: 10753927 DOI: 10.1074/jbc.275.15.11198] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The new member of the Ras superfamily of G-proteins, Rheb, has been identified in rat and human, but its function has not been defined. We report here the identification of Rheb homologues in the budding yeast Saccharomyces cerevisiae (ScRheb) as well as in Schizosaccharomyces pombe, Drosophila melanogaster, zebrafish, and Ciona intestinalis. These proteins define a new class of G-proteins based on 1) their overall sequence similarity, 2) high conservation of their effector domain sequence, 3) presence of a unique arginine in their G1 box, and 4) presence of a conserved CAAX farnesylation motif. Characterization of an S. cerevisiae strain deficient in ScRheb showed that it is hypersensitive to growth inhibitory effects of canavanine and thialysine, which are analogues of arginine and lysine, respectively. Accordingly, the uptake of arginine and lysine was increased in the ScRheb-deficient strain. This increased arginine uptake requires the arginine-specific permease Can1p. The function of ScRheb is dependent on having an intact effector domain since mutations in the effector domain of ScRheb are incapable of complementing canavanine hypersensitivity of scrheb disruptant cells. Furthermore, the conserved arginine in the G1 box plays a role in the activity of ScRheb, as a mutation of this arginine to glycine significantly reduced the ability of ScRheb to complement canavanine hypersensitivity of ScRheb-deficient yeast. Finally, a mutation in the C-terminal CAAX farnesylation motif resulted in a loss of ScRheb function. This result, in combination with our finding that ScRheb is farnesylated, suggests that farnesylation plays a key role in ScRheb function. Our findings assign the regulation of arginine and lysine uptake as the first physiological function for this new farnesylated Ras superfamily G-protein.
Collapse
Affiliation(s)
- J Urano
- Department of Microbiology, Molecular Biology Institute, University of California, Los Angeles, California 90095-1489, USA
| | | | | | | |
Collapse
|
31
|
Carraway CA, Carvajal ME, Carraway KL. Association of the Ras to mitogen-activated protein kinase signal transduction pathway with microfilaments. Evidence for a p185(neu)-containing cell surface signal transduction particle linking the mitogenic pathway to a membrane-microfilament association site. J Biol Chem 1999; 274:25659-67. [PMID: 10464302 DOI: 10.1074/jbc.274.36.25659] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Microvilli of the aggressive 13762 ascites mammary adenocarcinoma contain a large, microfilament-associated signal transduction particle whose scaffolding is a stable glycoprotein complex (Li, Y., Hua, F., Carraway, K. L., and Carraway, C. A. C. (1999) J. Biol. Chem. 274, 25651-25658) associated with the growth factor receptor p185(neu). The receptor is constitutively tyrosine-phosphorylated in the cells and microvilli, predicting that it should recruit mitogenic pathway components to this membrane-microfilament interaction site. Immunoprecipitation of cell lysates with anti-phosphotyrosine and immunoblotting showed phosphorylated forms of the mitogenic pathway proteins Shc and MAPK in addition to p185(neu), suggesting that the Ras to MAPK mitogenic pathway is activated. Immunoblotting of p185(neu)-containing microvillar fractions revealed the presence in each of stably associated Shc, Grb-2, Sos, Ras, Raf, mitogen-activated protein kinase kinase, and mitogen-activated protein kinase/extracellular signal-regulated kinase, as well as the transcription factor-phosphorylating kinase Rsk. All of these pathway components co-immunoprecipitated with p185(neu) from cleared lysates of microvilli solubilized under microfilament-depolymerizing conditions. The recruitment of constitutively phosphorylated p185(neu) and the activated mitogenic pathway proteins to this membrane-microfilament interaction site provides a physical model for integrating the assembly of the mitogenic pathway with the transmission of growth factor signal to the cytoskeleton. This linkage is probably a requisite step in the global cytoskeleton remodeling accompanying mitogenesis.
Collapse
Affiliation(s)
- C A Carraway
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, Florida 33101, USA.
| | | | | |
Collapse
|
32
|
Afonso A, Weinstein J, Kelly J, Wolin R, Rosenblum SB, Connolly M, Guzi T, James L, Carr D, Patton R, Bishop WR, Kirshmeier P, Liu M, Heimark L, Chen KJ, Nomeir AA. Analogues of 1-(3,10-dibromo-8-chloro-6,11-dihydro-5H-benzo-[5,6]-cyclohepta [1,2-b]pyridin-11-yl)piperidine as inhibitors of farnesyl protein transferase. Bioorg Med Chem 1999; 7:1845-55. [PMID: 10530932 DOI: 10.1016/s0968-0896(99)00103-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The synthesis of several 4-pyridylacetyl N-oxide derivatives of 4-(3-bromo-6,11-dihydro-5H-benzo[5,6]-cyclohepta[1,2-b]-pyridin-11-yl)pi perazine/piperidine 3 is described. This study was aimed at identifying fomesyl protein transferase (FPT) inhibitors in these two series of tricycles containing different phenyl ring substituents. The in vitro activity profile of the initial group of compounds 7a-7g led to the synthesis of the 8-methyl-10-methoxy and 8-methyl-10-bromo analogues 7i, 13i, and 13j. The 11R(-) enantiomers of these compounds were found to exhibit potent in vitro FPT inhibition activity.
Collapse
Affiliation(s)
- A Afonso
- Schering-Plough Research Institute, Kenilworth, NJ 07033, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Afonso A, Kelly J, Weinstein J, James L, Bishop WR. Analogs of 4-(3-bromo-8-methyl-10-methoxy-6,11-dihydro-5H-benzo[5,6]-cyclo hepta[1,2-b]pyridin-11-yl)-1-(4-pyridinylacetyl)piperidine N-oxide as inhibitors of farnesyl protein transferase. Bioorg Med Chem Lett 1999; 9:1875-80. [PMID: 10406658 DOI: 10.1016/s0960-894x(99)00287-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A series of 3-substituted analogs 3 of 4-(3-bromo-8-methyl-10-methoxy-6,11-dihydro-5H-benzo[5,6]-cyclohepta[1,2 b]pyridin-11-yl)-1-(4-pyridinylacetyl)piperidine N-oxide 2 was prepared and evaluated as FPT inhibitors. The objective of this study was to identify other substituents at C3 in this series of FPT inhibitors that would have the FPT potency enhancement similar to that found for a C3 bromo substituent. The 3-methyl analog 17b was found to be tenfold less active than 2, and other C3 substituents having more steric bulk were found to cause a further reduction in activity.
Collapse
Affiliation(s)
- A Afonso
- Schering-Plough Research Institute, Kenilworth, NJ 07033, USA
| | | | | | | | | |
Collapse
|
34
|
Patterson SI, Skene JH. A shift in protein S-palmitoylation, with persistence of growth-associated substrates, marks a critical period for synaptic plasticity in developing brain. JOURNAL OF NEUROBIOLOGY 1999; 39:423-37. [PMID: 10363914 DOI: 10.1002/(sici)1097-4695(19990605)39:3<423::aid-neu8>3.0.co;2-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In the mammalian cortex, the initial formation of synaptic connections is followed by a prolonged period during which synaptic circuits are functional, but retain an elevated capacity for activity-dependent remodeling and functional plasticity. During this period, synaptic terminals appear fully mature, morphologically and physiologically. We show here, however, that synaptic terminals during this period are distinguished by their simultaneous accumulation of multiple growth-associated proteins at levels characteristic of axonal growth cones, and proteins involved in synaptic transmitter release at levels characteristic of adult synapses. We show further that newly formed synapses undergo a switch in the dynamic S-palmitoylation of proteins early in the critical period, which includes a large and specific decrease in the palmitoylation of GAP-43 and other major substrates characteristic of growth cones. Previous studies have shown that a similar reduction in ongoing palmitoylation of growth cone proteins is sufficient to stop advancing axons in vitro, suggesting that a developmental switch in protein S-palmitoylation serves to disengage the molecular machinery for axon extension in the absence of local triggers for remodeling during the critical period. Only much later does a decline in the availability of major growth cone components mark the molecular maturation of cortical synapses at the close of the critical period.
Collapse
Affiliation(s)
- S I Patterson
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | |
Collapse
|
35
|
Dumas JJ, Zhu Z, Connolly JL, Lambright DG. Structural basis of activation and GTP hydrolysis in Rab proteins. Structure 1999; 7:413-23. [PMID: 10196122 DOI: 10.1016/s0969-2126(99)80054-9] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Rab proteins comprise a large family of GTPases that regulate vesicle trafficking. Despite conservation of critical residues involved in nucleotide binding and hydrolysis, Rab proteins exhibit low sequence identity with other GTPases, and the structural basis for Rab function remains poorly characterized. RESULTS The 2. 0 A crystal structure of GppNHp-bound Rab3A reveals the structural determinants that stabilize the active conformation and regulate GTPase activity. The active conformation is stabilized by extensive hydrophobic contacts between the switch I and switch II regions. Serine residues in the phosphate-binding loop (P loop) and switch I region mediate unexpected interactions with the gamma phosphate of GTP that have not been observed in previous GTPase structures. Residues implicated in the interaction with effectors and regulatory factors map to a common face of the protein. The electrostatic potential at the surface of Rab3A indicates a non-uniform distribution of charged and nonpolar residues. CONCLUSIONS The major structural determinants of the active conformation involve residues that are conserved throughout the Rab family, indicating a common mode of activation. Novel interactions with the gamma phosphate impose stereochemical constraints on the mechanism of GTP hydrolysis and provide a structural explanation for the large variation of GTPase activity within the Rab family. An asymmetric distribution of charged and nonpolar residues suggests a plausible orientation with respect to vesicle membranes, positioning predominantly hydrophobic surfaces for interaction with membrane-associated effectors and regulatory factors. Thus, the structure of Rab3A establishes a framework for understanding the molecular mechanisms underlying the function of Rab GTPases.
Collapse
Affiliation(s)
- J J Dumas
- Program in Molecular Medicine, University of Massachusetts Medical Center, 373 Plantation Street, Worcester, MA 01605, USA
| | | | | | | |
Collapse
|
36
|
Graham SM, Oldham SM, Martin CB, Drugan JK, Zohn IE, Campbell S, Der CJ. TC21 and Ras share indistinguishable transforming and differentiating activities. Oncogene 1999; 18:2107-16. [PMID: 10321735 DOI: 10.1038/sj.onc.1202517] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Constitutively activated mutants of the Ras-related protein TC21/R-Ras2 cause tumorigenic transformation of NIH3T3 cells. However, unlike Ras, TC21 fails to bind to and activate the Raf-1 serine-threonine kinase. Thus, whereas Ras transformation is critically dependent on Raf-1 TC21 activity is promoted by activation of Raf-independent signaling pathways. In the present study, we have further compared the functions of Ras and TC21. First we determined the basis for the inability of TC21 to activate Raf-1. Whereas Ras can interact with the two distinct Ras-binding sequences in NH2-terminus of Raf-1, designated RBS1 and Raf-Cys, TC21 could only bind Raf-Cys. Thus, the inability of TC21 to bind to RBS1 may prevent it from promoting the translocation of Raf-1 to the plasma membrane. Second, we found that TC21 is an activator of the JNK and p38, but not ERK, mitogen-activated protein kinase cascades and that TC21 transforming activity was dependent on Rac function. Thus, like Ras, TC21 may activate a Rac/JNK pathway. Third, we determined if TC21 could cause the same biological consequences as Ras in three distinct cell types. Like Ras, activated TC21 caused transformation of RIE-1 rat intestinal epithelial cells and terminal differentiation of PC12 pheochromocytoma cells. Finally, activated TC21 blocked serum starvation-induced differentiation of C2 myoblasts, whereas dominant negative TC21 greatly accelerated this differentiation process. Therefore, TC21 and Ras share indistinguishable biological activities in all cell types that we have evaluated. These results support the importance of Raf-independent pathways in mediating the actions of Ras and TC21.
Collapse
Affiliation(s)
- S M Graham
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, 27599, USA
| | | | | | | | | | | | | |
Collapse
|
37
|
Al-Mulla F, Milner-White EJ, Going JJ, Birnie GD. Structural differences between valine-12 and aspartate-12 Ras proteins may modify carcinoma aggression. J Pathol 1999; 187:433-8. [PMID: 10398103 DOI: 10.1002/(sici)1096-9896(199903)187:4<433::aid-path273>3.0.co;2-e] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Recent evidence associates the codon 12 valine-for-glycine (G12V) mutant Ki-Ras protein with higher stage and increased lethality of colorectal carcinomas, while the codon 12 aspartate-for-glycine (G12D) Ras mutation shows no such association. Several observations may be relevant to this phenomenon. First, GTPase activity of G12V Ras is one-quarter that of G12D Ras and one-tenth that of wild-type (WT) Ras. Second, binding of the GTP analogue GppNp to G12D Ras is 8-fold weaker than its binding to G12V or WT Ras and crystal structures indicate that electrostatic repulsion between the carboxylate group of the G12D Asp-12 side-chain and the gamma phosphate of the bound nucleotide may make GTP binding to G12D Ras weaker even than that of GppNp. It is proposed that this lowering of affinity for GTP allows G12D Ras an escape from the oncogenic GTP-bound state, whereas GTP tightly bound to G12V mutant Ras generates a more persistent, potentially oncogenic, signal. Structural comparisons also suggest that differences between the Switch I (effector) region of G12D and G12V Ras could modify interactions with downstream signalling molecules such as Raf-1, neurofibromin, and phosphatidylinositol 3-hydroxy-kinase. Other differences between the G12D and G12V mutant Ras proteins include a lower affinity of the GTPase activating protein GAP for G12V than for G12D or WT Ras; but, as both G12D and G12V Ras are refractory to GTPase activation by GAP binding, this may be less significant. These studies complement experimental data showing that such Ras mutations differ in their effects in vitro and in vivo and, with recent data indicating heterogeneity of ras mutation in colorectal carcinomas and other tumours, make it plausible that codon 12 Ras mutations differ in carcinogenic potential and prognostic significance.
Collapse
Affiliation(s)
- F Al-Mulla
- The Beatson Institute for Cancer Research, CRC Beatson Laboratories, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | | | | | | |
Collapse
|
38
|
Abstract
Cdc42p is an essential GTPase that belongs to the Rho/Rac subfamily of Ras-like GTPases. These proteins act as molecular switches by responding to exogenous and/or endogenous signals and relaying those signals to activate downstream components of a biological pathway. The 11 current members of the Cdc42p family display between 75 and 100% amino acid identity and are functional as well as structural homologs. Cdc42p transduces signals to the actin cytoskeleton to initiate and maintain polarized gorwth and to mitogen-activated protein morphogenesis. In the budding yeast Saccharomyces cerevisiae, Cdc42p plays an important role in multiple actin-dependent morphogenetic events such as bud emergence, mating-projection formation, and pseudohyphal growth. In mammalian cells, Cdc42p regulates a variety of actin-dependent events and induces the JNK/SAPK protein kinase cascade, which leads to the activation of transcription factors within the nucleus. Cdc42p mediates these processes through interactions with a myriad of downstream effectors, whose number and regulation we are just starting to understand. In addition, Cdc42p has been implicated in a number of human diseases through interactions with its regulators and downstream effectors. While much is known about Cdc42p structure and functional interactions, little is known about the mechanism(s) by which it transduces signals within the cell. Future research should focus on this question as well as on the detailed analysis of the interactions of Cdc42p with its regulators and downstream effectors.
Collapse
Affiliation(s)
- D I Johnson
- Department of Microbiology & Molecular Genetics and the Markey Center for Molecular Genetics, University of Vermont, Burlington, Vermont 05405,
| |
Collapse
|
39
|
Ostermeier C, Brunger AT. Structural basis of Rab effector specificity: crystal structure of the small G protein Rab3A complexed with the effector domain of rabphilin-3A. Cell 1999; 96:363-74. [PMID: 10025402 DOI: 10.1016/s0092-8674(00)80549-8] [Citation(s) in RCA: 279] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The small G protein Rab3A plays an important role in the regulation of neurotransmitter release. The crystal structure of activated Rab3A/GTP/Mg2+ bound to the effector domain of rabphilin-3A was solved to 2.6 A resolution. Rabphilin-3A contacts Rab3A in two distinct areas. The first interface involves the Rab3A switch I and switch II regions, which are sensitive to the nucleotide-binding state of Rab3A. The second interface consists of a deep pocket in Rab3A that interacts with a SGAWFF structural element of rabphilin-3A. Sequence and structure analysis, and biochemical data suggest that this pocket, or Rab complementarity-determining region (RabCDR), establishes a specific interaction between each Rab protein and its effectors. RabCDRs could be major determinants of effector specificity during vesicle trafficking and fusion.
Collapse
Affiliation(s)
- C Ostermeier
- The Howard Hughes Medical Institute and Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, USA
| | | |
Collapse
|
40
|
Pederson KJ, Barbieri JT. Intracellular expression of the ADP-ribosyltransferase domain of Pseudomonas exoenzyme S is cytotoxic to eukaryotic cells. Mol Microbiol 1998; 30:751-9. [PMID: 10094623 DOI: 10.1046/j.1365-2958.1998.01106.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Exoenzyme S of Pseudomonas aeruginosa is an ADP-ribosyltransferase, which is secreted via a type III-dependent secretion mechanism and has been demonstrated to exert cytotoxic effects on eukaryotic cells. Alignment studies predict that the amino-terminus of exoenzyme S has limited primary amino acid homology with the YopE cytotoxin of Yersinia, while biochemical studies have localized the FAS-dependent ADP-ribosyltransferase activity to the carboxyl-terminus. Thus, exoenzyme S could interfere with host cell physiology via several independent mechanisms. The goal of this study was to define the role of the ADP-ribosyltransferase domain in the modulation of eukaryotic cell physiology. The carboxyl-terminal 222 amino acids of exoenzyme S, which represent the FAS-dependent ADP-ribosyltransferase domain (termed deltaN222), and a point mutant, deltaN222-E381A, which possesses a 2000-fold reduction in the capacity to ADP-ribosylate, were transiently expressed in eukaryotic cells under the control of the immediate early CMV promoter. Lysates from cells transfected with deltaN222 expressed ADP-ribosyltransferase activity. Co-transfection of deltaN222, but not deltaN222-E381A, resulted in a decrease in the steady-state levels of two reporter proteins, green fluorescent protein and luciferase, in both CHO and Vero cells. In addition, transfection with deltaN222 resulted in a greater percentage of cells staining with trypan blue than when cells were transfected with either deltaN222-E381A or control plasmid. Together, these data indicate that expression of the ADP-ribosyltransferase domain of exoenzyme S is cytotoxic to eukaryotic cells.
Collapse
Affiliation(s)
- K J Pederson
- Medical College of Wisconsin, Department of Microbiology and Molecular Genetics, Milwaukee 53226, USA
| | | |
Collapse
|
41
|
Halkides CJ, Farrar CT, Singel DJ. The effects of cryoprotection on the structure and activity of p21 ras: implications for electron spin-echo envelope modulation spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1998; 134:142-153. [PMID: 9740740 DOI: 10.1006/jmre.1998.1520] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Electron spin-echo envelope modulation (ESEEM) spectroscopy is widely used to investigate the active sites of biological molecules in frozen solutions. Various cryoprotection techniques, particularly the addition of co-solvents, are commonly employed in the preparation of such samples. In conjunction with ESEEM studies of Mn(II) guanosine nucleotide complexes of p21 ras, we have investigated the effects of cryoprotection on the spectroscopy, the structure, and the activity of this protein. Echo decay times, which typically govern ESEEM spectral resolution, were found to vary linearly with the concentration of glycerol or methyl alpha-D-glucopyranoside (MG), with both additives equally effective on a per-mole basis. The effect of glycerol and MG on the ESEEM amplitudes of various protein nucleiwas studied in ras p21.Mn(II). 5'guanylylimido-diphosphate(p21.Mn(II)-GMPPNP) complexes: these additives did not alter the distances of these nuclei from the Mn(II) ion. In particular, in p21 incorporating [2H-3]Thr, the Mn(II)-[2H-3]Thr35 distance was found to be unaffected by the concentration of cryoprotectant or the rate of freezing. The proximity of the cryoprotectants to the Mn(II) ion was probed by 2H ESEEM in solutions made with d5-glycerol and d7-methyl alpha-D-glucopyranoside (d7-MG). In p21.Mn(II)GMPPNP, the large deuterium modulations from the d5-glycerol exhibit saturation behavior with increasing d5-glycerol concentration, implying that glycerol, a widely used cryoprotectant, replaces the aquo ligands of the Mn(II) ion. The interaction between the Mn(II) ion of p21 and MG, however, is less intimate: the deuterium ESEEM amplitudes are much smaller for samples prepared with d7-MG than with d5-glycerol. Several polyhydroxylic compounds were found to have essentially no effect on the ability of the guanosine 5'-triphosphate (GTP) hydrolysis activating protein, GAP334, to catalyze hydrolysis of p21. guanosine 5'-triphosphate. This observation implies that the introduction of cryoprotectant does not significantly perturb the structure of p21 and gives insight into the mechanism of the GTPase reaction.
Collapse
Affiliation(s)
- C J Halkides
- Department of Chemistry, University of North Carolina at Wilmington, Wilmington, North Carolina, 28403-3297, USA.
| | | | | |
Collapse
|
42
|
Abstract
With the number of known roles played by Ras proteins increasing rapidly, finding answers to how the diverse cellular responses are triggered is becoming increasingly pertinent. Although our understanding of the control of specificity of signal transduction is still small, the combination of biochemical, structural and genetic analyses is starting to reveal how the cell-specific responses to Ras activation are controlled.
Collapse
Affiliation(s)
- C Rommel
- Regeneron Pharmaceuticals Inc., Tarrytown, New York 10591-6707, USA
| | | |
Collapse
|
43
|
Kelly J, Wolin R, Connolly M, Afonso A, James L, Kirshmeier P, Bishop WR, McPhail AT. Synthesis of isomeric 3-piperidinyl and 3-pyrrolidinyl benzo[5,6]cyclohepta[1,2-b]pyridines: sulfonamido derivatives as inhibitors of Ras prenylation. Bioorg Med Chem 1998; 6:673-86. [PMID: 9681133 DOI: 10.1016/s0968-0896(98)00026-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Blocking farnesylation of oncogenic Ras proteins is a mechanism based therapeutic approach that is of current interest for the development of antitumor agents to treat ras associated tumors. As part of a SAR study on the lead farnesyl protein transferase (FPT) inhibitor I, we report here the synthesis of novel geometric isomers II and III and the FPT inhibition activity of their N-acyl and N-sulfonamido derivatives 15-65. The N-acyl derivatives are markedly less active than the lead inhibitor I thereby demonstrating that the spatial location of the N-acyl group in I is critical for binding of the compound to FPT. In contrast to I, the N-sulfonamido-II series is a novel lead of non-sulfhydryl, nonpeptidic compounds that are dual FPT/GGPT inhibitors. In light of recent reports on the alternative prenylation of N- and K-Ras, dual FPT/GGPT inhibitors may be required to control cell proliferation in tumors containing activated Ras.
Collapse
Affiliation(s)
- J Kelly
- Schering-Plough Research Institute, Kenilworth, NJ 07033, USA
| | | | | | | | | | | | | | | |
Collapse
|
44
|
Ohnishi M, Yamawaki-Kataoka Y, Kariya K, Tamada M, Hu CD, Kataoka T. Selective inhibition of Ras interaction with its particular effector by synthetic peptides corresponding to the Ras effector region. J Biol Chem 1998; 273:10210-5. [PMID: 9553071 DOI: 10.1074/jbc.273.17.10210] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ras proteins possess multiple downstream effectors of distinct structures. We and others demonstrated that Ha-Ras carrying certain effector region mutations could interact differentially with its effectors, implying that significant differences exist in their Ras recognition mechanisms. Here, by employing the fluorescence polarization method, we measured the activity of effector region synthetic peptides bearing various amino acid substitutions to inhibit association of Ras with the effectors human Raf-1 and Schizosaccharomyces pombe Byr2. The effect of these peptides on association with another effector Saccharomyces cerevisiae adenylyl cyclase was also examined by measuring inhibition of the Ras-dependent adenylyl cyclase activity. The peptide corresponding to the residues 17-44 competitively inhibited Ras association with all the three effectors at the Ki values of 1 approximately 10 microM, and the inhibition was considerably attenuated by the D38A mutation. The peptide with the D38N mutation inhibited association of Ha-Ras with Byr2 but not with the others, whereas that with the P34G mutation inhibited association of Ha-Ras with Raf-1 and Byr2 but not with adenylyl cyclase. Thus, the specificity observed with the whole Ras protein was retained in the effector region peptide. These results suggest that the effector region residues constitute a major determinant for differential recognition of the effector molecules, raising a possibility for selective inhibition of a particular Ras function.
Collapse
Affiliation(s)
- M Ohnishi
- Department of Physiology II, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650, Japan
| | | | | | | | | | | |
Collapse
|
45
|
Ihara K, Muraguchi S, Kato M, Shimizu T, Shirakawa M, Kuroda S, Kaibuchi K, Hakoshima T. Crystal structure of human RhoA in a dominantly active form complexed with a GTP analogue. J Biol Chem 1998; 273:9656-66. [PMID: 9545299 DOI: 10.1074/jbc.273.16.9656] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 2.4-A resolution crystal structure of a dominantly active form of the small guanosine triphosphatase (GTPase) RhoA, RhoAV14, complexed with the nonhydrolyzable GTP analogue, guanosine 5'-3-O-(thio)triphosphate (GTPgammaS), reveals a fold similar to RhoA-GDP, which has been recently reported (Wei, Y., Zhang, Y., Derewenda, U., Liu, X., Minor, W., Nakamoto, R. K., Somlyo, A. V., Somlyo, A. P., and Derewenda, Z. S. (1997) Nat. Struct. Biol. 4, 699-703), but shows large conformational differences localized in switch I and switch II. These changes produce hydrophobic patches on the molecular surface of switch I, which has been suggested to be involved in its effector binding. Compared with H-Ras and other GTPases bound to GTP or GTP analogues, the significant conformational differences are located in regions involving switches I and II and part of the antiparallel beta-sheet between switches I and II. Key residues that produce these conformational differences were identified. In addition to these differences, RhoA contains four insertion or deletion sites with an extra helical subdomain that seems to be characteristic of members of the Rho family, including Rac1, but with several variations in details. These sites also display large displacements from those of H-Ras. The ADP-ribosylation residue, Asn41, by C3-like exoenzymes stacks on the indole ring of Trp58 with a hydrogen bond to the main chain of Glu40. The recognition of the guanosine moiety of GTPgammaS by the GTPase contains water-mediated hydrogen bonds, which seem to be common in the Rho family. These structural differences provide an insight into specific interaction sites with the effectors, as well as with modulators such as guanine nucleotide exchange factor (GEF) and guanine nucleotide dissociation inhibitor (GDI).
Collapse
Affiliation(s)
- K Ihara
- Divisions of Structural Biology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-01, Japan
| | | | | | | | | | | | | | | |
Collapse
|
46
|
Ganesan AK, Frank DW, Misra RP, Schmidt G, Barbieri JT. Pseudomonas aeruginosa exoenzyme S ADP-ribosylates Ras at multiple sites. J Biol Chem 1998; 273:7332-7. [PMID: 9516428 DOI: 10.1074/jbc.273.13.7332] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pseudomonas aeruginosa exoenzyme S (ExoS) ADP-ribosylated Ras to a stoichiometry of approximately 2 molecules of ADP-ribose incorporated per molecule of Ras, which suggested that ExoS could ADP-ribosylate Ras at more than one arginine residue. SDS-polyacrylamide gel electrophoresis analysis showed that ADP-ribosylated Ras possessed a slower mobility than non-ADP-ribosylated Ras. Analysis of the ADP-ribosylation of in vitro transcribed/translated Ras by ExoS identified two electrophoretically shifted forms of Ras, which was consistent with the ADP-ribosylation of Ras at two distinct arginine residues. Analysis of ADP-ribosylated in vitro transcribed/translated Ras mutants possessing individual Arg-to-Ala substitutions showed that Arg-41 was the preferred site of ADP-ribosylation and that the second ADP-ribosylation event occurred at a slower rate than the ADP-ribosylation at Arg-41, but did not occur at a specific arginine residue. Analysis of bacterially expressed wild-type RasDeltaCAAX and RasDeltaCAAXR41K supported the conclusion that Arg-41 was the preferred site of ADP-ribosylation. Arg-41 is located adjacent to the switch 1 region of Ras, which is involved in effector interactions. Introduction of ExoS into eukaryotic cells inhibited Ras-mediated eukaryotic signal transduction since infection of PC-12 cells with an ExoS-producing strain of P. aeruginosa inhibited nerve growth factor-stimulated neurite formation. This is the first demonstration that ExoS disrupts a Ras-mediated signal transduction pathway.
Collapse
Affiliation(s)
- A K Ganesan
- Department of Microbiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | | | | | | | | |
Collapse
|
47
|
de Souza Fernandez T, Menezes de Souza J, Macedo Silva ML, Tabak D, Abdelhay E. Correlation of N-ras point mutations with specific chromosomal abnormalities in primary myelodysplastic syndrome. Leuk Res 1998; 22:125-34. [PMID: 9593469 DOI: 10.1016/s0145-2126(97)00112-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A cytogenetic and N-ras point mutation study was done in patients with primary myelodysplastic syndrome (MDS) from Rio de Janeiro, Brazil, in order to evaluate the progression of preleukemic states to overt leukemia. Cytogenetic analysis was performed in 50 patients with MDS and clonal chromosomal abnormalities were detected in 19 (38%) of them. Patients with refractory anemia (RA) or with ringed sideroblasts (RARS) presented normal karyotypes or single abnormalities as del(5q) or -Y, while patients in more advanced states as RA with excess of blasts (RAEB), RAEB in transformation (RAEB-t) and chronic myelomonocytic leukemia (CMML) showed complex karyotypes and single abnormalities involving chromosomes 7 or 8, which were related to poor prognosis and elevated risk of transformation to acute myeloid leukemia (AML). The frequency of ras activation was studied in these 50 patients with MDS. Samples of bone marrow were screened for oncogenic point mutations by DNA amplification followed by oligonucleotide hybridization analysis (PCR-ASO) at codon 12 of N-ras proto-oncogene. We detected N-ras point mutations in 21 patients (42%). Progression from MDS to AML was observed in 9 patients (18%). The correlation analysis between N-ras point mutations and specific chromosomal abnormalities indicated that although mutated N-ras was found in cells with del(5q) and monosomy 7, cells with those abnormalities and normal N-ras were also identified. Otherwise trisomy of chromosome 8 showed a correlation with N-ras point mutations and in all cases, patients showed progression of MDS to AML during the follow-up study. MDS comprises a heterogeneous group of hematopoietic disorders and probably several steps are implicated in the evolution to AML. In this work we suggest that one possible pathway of leukemogenesis in MDS includes N-ras point mutations in association with trisomy of chromosome 8.
Collapse
Affiliation(s)
- T de Souza Fernandez
- Biophysics Institute Carlos Chagas Filho, Federal University of Rio de Janeiro, Brazil
| | | | | | | | | |
Collapse
|
48
|
Davis CR, Richman TJ, Deliduka SB, Blaisdell JO, Collins CC, Johnson DI. Analysis of the mechanisms of action of the Saccharomyces cerevisiae dominant lethal cdc42G12V and dominant negative cdc42D118A mutations. J Biol Chem 1998; 273:849-58. [PMID: 9422741 DOI: 10.1074/jbc.273.2.849] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Saccharomyces cerevisiae Cdc42p GTPase is localized to the plasma membrane and involved in signal transduction mechanisms controlling cell polarity. The mechanisms of action of the dominant negative cdc42(D118A) mutant and the lethal, gain of function cdc42(G12V) mutant were examined. Cdc42(D118A,C188S)p and its guanine-nucleotide exchange factor Cdc24p displayed a temperature-dependent interaction in the two-hybrid system, which correlated with the temperature dependence of the cdc42(D118A) phenotype and supported a Cdc24p sequestration model for the mechanism of cdc42(D118A) action. Five cdc42 mutations were isolated that led to decreased interactions with Cdc24p. The isolation of one mutation (V44A) correlated with the observations that the T35A effector domain mutation could interfere with Cdc42(D118A, C188S)p-Cdc24p interactions and could suppress the cdc42(D118A) mutation, suggesting that Cdc24p may interact with Cdc42p through its effector domain. The cdc42(G12V) mutant phenotypes were suppressed by the intragenic T35A and K183-187Q mutations and in skm1Delta and cla4Delta cells but not ste20Delta cells, suggesting that the mechanism of cdc42(G12V) action is through the Skm1p and Cla4p protein kinases at the plasma membrane. Two intragenic suppressors of cdc42(G12V) were also identified that displayed a dominant negative phenotype at 16 degrees C, which was not suppressed by overexpression of Cdc24p, suggesting an alternate mechanism of action for these dominant negative mutations.
Collapse
Affiliation(s)
- C R Davis
- Department of Microbiology and Molecular Genetics and the Markey Center for Molecular Genetics, University of Vermont, Burlington, Vermont 05405, USA
| | | | | | | | | | | |
Collapse
|
49
|
9.4 Activation and Inactivation of Ras-Like Gtpases by Bacterial Cytotoxins. J Microbiol Methods 1998. [DOI: 10.1016/s0580-9517(08)70309-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
50
|
|