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Bloomfield G, Traynor D, Sander SP, Veltman DM, Pachebat JA, Kay RR. Neurofibromin controls macropinocytosis and phagocytosis in Dictyostelium. eLife 2015; 4. [PMID: 25815683 PMCID: PMC4374526 DOI: 10.7554/elife.04940] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 03/06/2015] [Indexed: 02/06/2023] Open
Abstract
Cells use phagocytosis and macropinocytosis to internalise bulk material, which in phagotrophic organisms supplies the nutrients necessary for growth. Wildtype Dictyostelium amoebae feed on bacteria, but for decades laboratory work has relied on axenic mutants that can also grow on liquid media. We used forward genetics to identify the causative gene underlying this phenotype. This gene encodes the RasGAP Neurofibromin (NF1). Loss of NF1 enables axenic growth by increasing fluid uptake. Mutants form outsized macropinosomes which are promoted by greater Ras and PI3K activity at sites of endocytosis. Relatedly, NF1 mutants can ingest larger-than-normal particles using phagocytosis. An NF1 reporter is recruited to nascent macropinosomes, suggesting that NF1 limits their size by locally inhibiting Ras signalling. Our results link NF1 with macropinocytosis and phagocytosis for the first time, and we propose that NF1 evolved in early phagotrophs to spatially modulate Ras activity, thereby constraining and shaping their feeding structures. DOI:http://dx.doi.org/10.7554/eLife.04940.001 Dictyostelium amoebae are microbes that feed on bacteria living in the soil. They are unusual in that the amoebae can survive and grow in a single-celled form, but when food is scarce, many individual cells can gather together to form a simple multicellular organism. To feed on bacteria, the amoebae use a process called phagocytosis, which starts with the membrane that surrounds the cell growing outwards to completely surround the bacteria. This leads to the bacteria entering the amoeba within a membrane compartment called a vesicle, where they are broken down into small molecules by enzymes. The cells can also take up fluids and dissolved molecules using a similar process called macropinocytosis. With its short and relatively simple lifestyle, Dictyostelium is often used in research to study phagocytosis, cell movement and other processes that are also found in larger organisms. For example, some immune cells in animals use phagocytosis to capture and destroy invading microbes. Most studies using Dictyostelium as a model have used amoebae with genetic mutations that allow them to be grown in liquid cultures in the laboratory without needing to feed on bacteria. The mutations allow the ‘mutant’ amoebae to take up more liquid and dissolved nutrients by macropinocytosis, but it is not known where in the genome these mutations are. Here, Bloomfield et al. used genome sequencing to reveal that these mutations alter a gene that encodes a protein called Neurofibromin. The experiments show that the loss of Neurofibromin increases the amount of fluid taken up by the amoebae through macropinocytosis, and also enables the amoebae to take up larger-than-normal particles during phagocytosis. The experiments suggest that Neurofibromin controls both phagocytosis and macropinocytosis by inhibiting the activity of another protein called Ras. Neurofibromin is found in animals and many other organisms so Bloomfield et al. propose that it is an ancient protein that evolved in early single-celled organisms to control the size and shape of their feeding structures. In humans, mutations in the gene that encodes the Neurofibromin protein can lead to the development of a severe disorder—called Neurofibromatosis type 1—in which tumours form in the nervous system. Given that tumour cells can use phagocytosis and macropinocytosis to gain nutrients as they grow, understanding how this protein works in the Dictyostelium amoebae may help to inform future efforts to develop treatments for this human disease. DOI:http://dx.doi.org/10.7554/eLife.04940.002
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Affiliation(s)
| | - David Traynor
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Sophia P Sander
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Douwe M Veltman
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Justin A Pachebat
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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2
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Shen X, Zeng H, Xie L, He J, Li J, Xie X, Luo C, Xu H, Zhou M, Nie Q, Zhang X. The GTPase activating Rap/RanGAP domain-like 1 gene is associated with chicken reproductive traits. PLoS One 2012; 7:e33851. [PMID: 22496769 PMCID: PMC3322132 DOI: 10.1371/journal.pone.0033851] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 02/19/2012] [Indexed: 11/28/2022] Open
Abstract
Background Abundant evidence indicates that chicken reproduction is strictly regulated by the hypothalamic-pituitary-gonad (HPG) axis, and the genes included in the HPG axis have been studied extensively. However, the question remains as to whether any other genes outside of the HPG system are involved in regulating chicken reproduction. The present study was aimed to identify, on a genome-wide level, novel genes associated with chicken reproductive traits. Methodology/Principal Finding Suppressive subtractive hybridization (SSH), genome-wide association study (GWAS), and gene-centric GWAS were used to identify novel genes underlying chicken reproduction. Single marker-trait association analysis with a large population and allelic frequency spectrum analysis were used to confirm the effects of candidate genes. Using two full-sib Ningdu Sanhuang (NDH) chickens, GARNL1 was identified as a candidate gene involved in chicken broodiness by SSH analysis. Its expression levels in the hypothalamus and pituitary were significantly higher in brooding chickens than in non-brooding chickens. GWAS analysis with a NDH two tail sample showed that 2802 SNPs were significantly associated with egg number at 300 d of age (EN300). Among the 2802 SNPs, 2 SNPs composed a block overlapping the GARNL1 gene. The gene-centric GWAS analysis with another two tail sample of NDH showed that GARNL1 was strongly associated with EN300 and age at first egg (AFE). Single marker-trait association analysis in 1301 female NDH chickens confirmed that variation in this gene was related to EN300 and AFE. The allelic frequency spectrum of the SNP rs15700989 among 5 different populations supported the above associations. Western blotting, RT-PCR, and qPCR were used to analyze alternative splicing of the GARNL1 gene. RT-PCR detected 5 transcripts and revealed that the transcript, which has a 141 bp insertion, was expressed in a tissue-specific manner. Conclusions/Significance Our findings demonstrate that the GARNL1 gene contributes to chicken reproductive traits.
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Affiliation(s)
- Xu Shen
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, Guangzhou, China
| | - Hua Zeng
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
| | - Liang Xie
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
- Institute of Animal Science and Veterinary, Hainan Academy of Agricultural Sciences, Haikou, Hainan, China
| | - Jun He
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, Guangzhou, China
| | - Jian Li
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, Guangzhou, China
| | - Xiujuan Xie
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, Guangzhou, China
| | - Chenglong Luo
- Institute of Animal Science, Guangdong Academy of Agricultural Sciences, Guangzhou, Guangdong, China
| | - Haiping Xu
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, Guangzhou, China
| | - Min Zhou
- Biotechnology Institute, Jiang Xi Education College, Nanchang, Jiangxi, China
| | - Qinghua Nie
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, Guangzhou, China
| | - Xiquan Zhang
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong, China
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, Guangzhou, China
- * E-mail:
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Lowy DR, Johnson MR, DeClue JE, Cen H, Zhang K, Papageorge AG, Vass WC, Willumsen BM, Valentine MB, Look AT. Cell transformation by ras and regulation of its protein product. CIBA FOUNDATION SYMPOSIUM 2007; 176:67-80; discussion 80-4. [PMID: 8299427 DOI: 10.1002/9780470514450.ch5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We are studying the biological activity and regulation of mammalian Ras protein in tumours and in physiological signalling. We have shown that GAP (the GTPase-activating protein) is a potent negative regulator of normal Ras in cells. Reduction or loss of the NF1 gene product neurofibromin, in association with genetic abnormalities of the NF1 locus, has been identified in schwannoma cell lines from patients with neurofibromatosis and in melanoma and neuroblastoma lines from patients without neurofibromatosis. Although loss of neurofibromin in the schwannoma lines was associated with a high proportion of normal Ras protein in the active GTP-bound state, Ras-GTP appeared to be appropriately regulated in the melanoma and neuroblastoma lines, which contain normal levels of GAP. Therefore the GTPase-activating activity of neurofibromin is not essential for negative regulation of Ras in some cell types and the putative tumour suppressor function of neurofibromin in such cell types is independent of its GTPase-activating activity. Mitogen activation of Ras in fibroblasts is mediated primarily by exchange factors, which probably interact with a region on the Ras protein distinct from the region required for interaction with GAP. Multiple full-length cDNAs have identified a mouse gene whose products are related to yeast CDC25 guanine nucleotide exchange factor.
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Affiliation(s)
- D R Lowy
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, MD
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Feiz-Erfan I, Zabramski JM, Herrmann LL, Coons SW. Cavernous malformation within a schwannoma: review of the literature and hypothesis of a common genetic etiology. Acta Neurochir (Wien) 2006; 148:647-52; discussion 652. [PMID: 16450046 DOI: 10.1007/s00701-005-0716-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2005] [Accepted: 11/17/2005] [Indexed: 10/25/2022]
Abstract
The finding of cavernous malformations within tumors of the central or peripheral nervous system is a rare occurrence. We report a case of a histologically proven cavernous malformation found within an eighth cranial nerve schwannoma in a 76-year-old man. The patient presented with progressive loss of hearing on the left, facial pain and dysesthesia. Symptoms improved significantly after the tumor was subtotally resected through a left retrosigmoid craniotomy. Including the present report, 34 cases of cavernous malformations associated with tumors of nervous system origin, 24 cases (71%) involving tumors of Schwann cell origin, and 9 cases (26%) involving gliomas have been published. The cases were classified into two forms based on the type of association. Conjoined association, in which the cavernous malformation is located within the tissue of the nervous system tumor, and discrete association, in which the cavernous malformation and nervous system tumor are in separate locations. We explore the etiology of this association and hypothesize that a common genetic pathway may be involved in a majority of these cases.
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MESH Headings
- Aged
- Blood Vessels/pathology
- Blood Vessels/physiopathology
- Cell Transformation, Neoplastic/genetics
- Chromosomes, Human, Pair 3/genetics
- Chromosomes, Human, Pair 7/genetics
- Comorbidity
- Genetic Predisposition to Disease/genetics
- Hearing Loss, Sensorineural/etiology
- Hearing Loss, Sensorineural/physiopathology
- Hemangioma, Cavernous, Central Nervous System/diagnosis
- Hemangioma, Cavernous, Central Nervous System/genetics
- Hemangioma, Cavernous, Central Nervous System/physiopathology
- Humans
- KRIT1 Protein
- Magnetic Resonance Imaging
- Male
- Microtubule-Associated Proteins/genetics
- Mutation/genetics
- Neurofibromin 1/genetics
- Neuroma, Acoustic/diagnosis
- Neuroma, Acoustic/genetics
- Neuroma, Acoustic/physiopathology
- Pain/etiology
- Pain/physiopathology
- Proto-Oncogene Proteins/genetics
- Schwann Cells/pathology
- Signal Transduction/genetics
- Vestibulocochlear Nerve/blood supply
- Vestibulocochlear Nerve/pathology
- Vestibulocochlear Nerve/physiopathology
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Affiliation(s)
- I Feiz-Erfan
- Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013, USA.
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5
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Schwarzbraun T, Vincent JB, Schumacher A, Geschwind DH, Oliveira J, Windpassinger C, Ofner L, Ledinegg MK, Kroisel PM, Wagner K, Petek E. Cloning, genomic structure, and expression profiles of TULIP1 (GARNL1), a brain-expressed candidate gene for 14q13-linked neurological phenotypes, and its murine homologue. Genomics 2005; 84:577-86. [PMID: 15498464 DOI: 10.1016/j.ygeno.2004.04.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2004] [Revised: 04/30/2004] [Indexed: 10/26/2022]
Abstract
Previously, we have described the clinical and molecular characterization of a de novo 14q13.1-q21.1 microdeletion, less than 3.5 Mb in size, in a patient with severe microcephaly, psychomotor retardation, and other clinical anomalies. Here we report the characterization of the genomic structure of the human tuberin-like protein gene 1 (TULIP1; approved gene symbol GARNL1), a CpGisland-associated, brain-expressed candidate gene for the neurological findings in our patient, and its murine homologue. The human TULIP1 gene was mapped to chromosome band 14q13.2 by fluorescence in situ hybridization of BAC clone RP11-355C3 (GenBank Accession No. AL160231), containing the 3' region of the gene. TULIP1 spans about 271 kb of human genomic DNA and is divided into 41 exons. An untranscribed, processed pseudogene of TULIP1 was found on human chromosome band 9q31.1. The active locus TULIP1, encoding a predicted protein of 2036 amino acids, is expressed ubiquitously in pre- and postnatal human tissues. The murine homologue Tulip1 spans about 220 kb of mouse genomic DNA and is also divided into 41 exons, encoding a predicted protein of 2035 amino acids. No pseudogene could be found in the available mouse sequence data. Several splicing variants were found. Considering the location, expression profile, and predicted function, TULIP1 is a strong candidate for several neurological features seen in 14q deletion patients. Additionally we searched for mutations in the coding region of TULIP1 in subjects from a family with idiopathic basal ganglia calcification (IBGC; Fahr disease), previously linked to chromosome 14q. We identified two novel SNPs in the intron-exon boundaries; however, they did not segregate only with affected subjects in the predicted model of an autosomal dominant disease such as IBGC.
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Affiliation(s)
- Thomas Schwarzbraun
- Institute of Medical Biology and Human Genetics, Medical University of Graz, Harrachgasse 21/8, A-8010 Graz, Austria
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Fralix KD, Zhao S, Venkatasubbarao K, Freeman JW. Rap1 reverses transcriptional repression of TGF-beta type II receptor by a mechanism involving AP-1 in the human pancreatic cancer cell line, UK Pan-1. J Cell Physiol 2003; 194:88-99. [PMID: 12447993 DOI: 10.1002/jcp.10192] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The TGF-beta signaling pathway has potent anti-mitogenic effects in epithelial cells and loss of negative growth regulation is often associated with increased tumorigenicity. The human pancreatic ductal adenocarcinoma cell line, UK Pan-1, which expresses DPC4, is not highly responsive to TGF-beta due to transcriptional repression of TGF-beta type II receptor (RII). Here, we show that UK Pan-1 cells transfected with a plasmid to overexpress rap1 protein (UK/rap1) causes an increase in RII transcription and restores sensitivity to TGF-beta growth inhibition. The overexpression of rap1 was associated with diminished ras signaling as measured by ras binding domain (RBD)-binding assays. Electrophoretic mobility shift assays (EMSA) analysis revealed increased binding of nuclear proteins to a previously identified positive regulatory element (PRE1) of the RII promoter in rap1 transfected cells. Competition with an oligo containing the AP-1 consensus site was able to inhibit this binding of nuclear proteins to the PRE1 region. Further EMSA analysis using antibodies to various AP-1 components revealed that junB antibodies partially depleted the increase in binding to the PRE1 seen in UK/rap1 cells while antibodies to other AP-1 constituents such as c-jun, c-fos, and ATF-1 had no effect on binding. Consistent with this data, transient transfection of UK Pan-1 cells with junB resulted in greater RII transcription (twofold) as measured by RII-luciferase assay. Mutation of the AP-1 site inhibited junB-mediated or rap1-mediated increases in RII promoter activity. These data suggest that rap1 signaling may mediate an increase in RII transcription via increased binding of nuclear factors including junB to the PRE1 region of the RII promoter.
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Affiliation(s)
- Kimberly D Fralix
- Department of Pharmacology, University of Texas Health Science Center, San Antonio 78229, USA
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Chang KC, Chuang NN. GTPase stimulation in shrimp Ras(Q(61)K) with geranylgeranyl pyrophosphate but not mammalian GAP. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2001; 290:642-51. [PMID: 11748613 DOI: 10.1002/jez.1115] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BALB/3T3 cells were transformed by transfection with DNA encoding the mutated ras(Q(61)K) from shrimp Penaeus japonicus (Huang et al., 2000). The GTPase-activating protein (GAP) in the cytosol fraction was significantly expressed and degraded, compared to untransformed cells on the western blot. To understand this in more detail, the interaction of the bacterially expressed shrimp Ras (S-Ras) with GAP was investigated using GAP purified from mouse brains. SDS-polyacrylamide gel electrophoresis revealed the monomers of the purified GAP to have a relative mass of 65,000. Since the purified GAP was bound to the Ras conjugated affinity sepharose column with high affinity and its GTP hydolysis activity upon binding with tubulin was suppressed, the purified enzyme was concluded to be neurofibromin-like. The purified GAP enhanced the intrinsic GTPase activity of the S-Ras, to convert it into the inactive GDP-bound form, in agreement with findings for GTP-bound K(B)-Ras in vitro. To compare the effects between isoprenoids and GAP on the GTP-hydrolysis of Ras, we applied the GTP-locked shrimp mutant S-Ras(Q(61)K) and GTP-locked rat mutant K(B)-ras(Q(61)K). Radioassay studies showed that geranylgeranyl pyrophosphate at microg level catalyzed the GTP hydrolysis of S-Ras(Q(61)K) and K(B)-ras(Q(61)K) competently, but not farnesyl pyrophosphate or the purified GAP. The present study provides the view that the geranylgeranyl pyrophosphate at carboxyl terminal CAAX assists GTP hydrolysis to Ras proteins probably in a manner similar to the substrate assisted catalysis in GTPase mechanism.
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Affiliation(s)
- K C Chang
- Division of Biochemistry and Molecular Sciences, Institute of Zoology, Academia Sinica, Nankang, Taipei, Taiwan 11529
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8
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van den Berghe N, Cool RH, Wittinghofer A. Discriminatory residues in Ras and Rap for guanine nucleotide exchange factor recognition. J Biol Chem 1999; 274:11078-85. [PMID: 10196191 DOI: 10.1074/jbc.274.16.11078] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The inability of the S17N mutant of Rap1A to sequester the catalytic domain of the Rap guanine nucleotide exchange factor C3G (van den Berghe, N., Cool, R. H., Horn, G., and Wittinghofer, A. (1997) Oncogene 15, 845-850) prompted us to study possible fundamental differences in the way Rap1 interacts with C3G compared with the interaction of Ras with the catalytic domain of the mouse Ras guanine nucleotide exchange factor Cdc25(Mm). A variety of mutants in both Ras and Rap1A were designed, and both the C3G and Cdc25(Mm) catalyzed release of guanine nucleotide from these mutants was studied. In addition, we could identify regions in Rap2A that are responsible for the lack of recognition by C3G and induce high C3G activity by replacement of these residues with the corresponding Rap1A residues. The different Ras and Rap mutants showed that many residues were equally important for both C3G and Cdc25(Mm), suggesting that they interact similarly with their substrates. However, several residues were also identified to be important for the exchange reaction with only C3G (Leu70) or only Cdc25(Mm) (Gln61 and Tyr40). These results are discussed in the light of the structure of the Ras-Sos complex and suggest that some important differences in the interaction of Rap1 with C3G and Ras with Cdc25(Mm) indeed exist and that marker residues have been identified for the different structural requirements.
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Affiliation(s)
- N van den Berghe
- Max-Planck-Institut für Molekulare Physiologie, Abteilung Strukturelle Biologie, Rheinlanddamm 201, 44139 Dortmund, Germany
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11
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Andersen OS, Greathouse DV, Providence LL, Becker MD, Koeppe RE. Importance of Tryptophan Dipoles for Protein Function: 5-Fluorination of Tryptophans in Gramicidin A Channels. J Am Chem Soc 1998. [DOI: 10.1021/ja980182l] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- O. S. Andersen
- Contribution from the Department of Physiology and Biophysics, Cornell University Medical College, New York, New York 10021, and the Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - D. V. Greathouse
- Contribution from the Department of Physiology and Biophysics, Cornell University Medical College, New York, New York 10021, and the Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - L. L. Providence
- Contribution from the Department of Physiology and Biophysics, Cornell University Medical College, New York, New York 10021, and the Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - M. D. Becker
- Contribution from the Department of Physiology and Biophysics, Cornell University Medical College, New York, New York 10021, and the Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
| | - R. E. Koeppe
- Contribution from the Department of Physiology and Biophysics, Cornell University Medical College, New York, New York 10021, and the Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701
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Tocque B, Delumeau I, Parker F, Maurier F, Multon MC, Schweighoffer F. Ras-GTPase activating protein (GAP): a putative effector for Ras. Cell Signal 1997; 9:153-8. [PMID: 9113414 DOI: 10.1016/s0898-6568(96)00135-0] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
One attractive candidate for a Ras effector protein, other than the Raf kinases, is Ras-GAP. Indeed, recent literature suggests that besides the Raf/MAP kinase cascade, additional pathways must be stimulated to elicit a full biological response to Ras. Ras binds the COOH terminal domain of Ras-GAP, while the NH2 terminal domain appears to be essential for triggering downstream signals. Since Ras-GAP itself has no obvious enzymatic function that might explain a role in processes associated with proliferation, differentiation or apoptosis, candidates for downstream Ras-GAP effectors that fulfill this role remain to be identified. The newly found GAP-SH3 domain Binding Protein (G3BP) may be one of these. This review will briefly overview the candidates Ras effectors and discuss the results that position Ras-GAP as a critical effector downstream of Ras.
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Affiliation(s)
- B Tocque
- RPR Gene Medicine, CRVA, Vitry/Seine, France
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Nassar N, Horn G, Herrmann C, Block C, Janknecht R, Wittinghofer A. Ras/Rap effector specificity determined by charge reversal. NATURE STRUCTURAL BIOLOGY 1996; 3:723-9. [PMID: 8756332 DOI: 10.1038/nsb0896-723] [Citation(s) in RCA: 175] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Members of the Ras subfamily of small GTP-binding proteins have been shown to be promiscuous towards a variety of putative effector molecules such as the protein kinase c-Raf and the Ral-specific guanine nucleotide exchange factor (Ral-GEF). To address the question of specificity of interactions we have introduced the mutations E30D and K31E into Rap and show biochemically, by X-ray structure analysis and by transfection in vivo that the identical core effector region of Ras and Rap (residues 32-40) is responsible for molecular recognition, but that residues outside this region are responsible for the specificity of the interaction. The major determinant for the switch in specificity is the opposite charge of residue 31--Lys in Rap, Glu in Ras--which creates a favourable complementary interface for the Ras-Raf interaction.
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Affiliation(s)
- N Nassar
- Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Dortmund, Germany
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Abstract
ras proteins are positively regulated by nucleotide exchange factors and negatively regulated by GTPase-activating proteins (GAPs). Two GAPs have been found in mammalian cells, p120GAP and neurofibromin, the product of the type 1 neurofibromatosis (NF1) gene. A library of substitutions in the effector loop region of ras in an Escherichia coli plasmid expression system was screened for c-Ha-ras species with altered GAP interactions. Several substitutions preferentially disrupted the interaction of ras with p120GAP as compared with the interaction with the recombinant GAP-related domain of neurofibromin (NF1-GRD). The most extreme example, Tyr32His, encoded a ras species that was unaffected by p120GAP but was stimulated normally by NF1-GRD. Tyr32His was weakly transforming in Rat2 cells. Tyr32His ras was primarily GDP-bound in quiescent Rat2 cells, although it rapidly associated with GTP after treatment of cells with epidermal growth factor. These results show that the NF1 product has less stringent requirements than p120GAP for ras effector domain structure and that negative regulation of ras can be achieved in rat fibroblasts by the product of NF1.
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Affiliation(s)
- S Stang
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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Yoder-Hill J, Golubic M, Stacey DW. A conserved region of c-Ha-Ras is required for efficient GTPase stimulation by GTPase activating protein but not neurofibromin. J Biol Chem 1995; 270:27615-21. [PMID: 7499225 DOI: 10.1074/jbc.270.46.27615] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The effector binding domain and the switch II region of c-Ha-Ras are necessary for p120GAP-stimulated GTP hydrolysis. We report a third region of c-Ha-Ras located within the alpha 3 helix (amino acids 101-103) which is also required for efficient p120GAP, but not neurofibromin-mediated hydrolysis. This highly conserved region of the Ras protein was investigated using an insertion-deletion mutant (Ras-100LIR104) originally characterized by Willumsen et al. (Willumsen, B. M., Adari, H., Zhang, K., Papageorge, A. G., Stone, J. C., McCormick, F., and Lowy, D. R (1989) in The Guanine Nucleotide Binding Proteins; Common Structural and Functional Properties (Bosch, L., Kraal, B., and Parmeggiani, A., eds) pp. 165-178, Plenum Press, New York). The 100LIR104 substitution did not alter the intrinsic hydrolytic rate of the protein. The p120GAP-stimulated hydrolysis of Ras-100LIR104, however, was decreased by 2-3-fold compared to wild type Ras. This decrease in p120GAP-stimulated hydrolysis was not due to its inability to physically associate with Ras-100LIR104. GTP (as determined by competitive binding assays). Surprisingly, neurofibromin-stimulated GTP hydrolysis was unaltered by the mutation. Finally, no differences were observed in the ability of either the p120GAP catalytic domain or the neurofibromin GRD to accelerate Ras-100LIR104 GTPase activity, indicating that the amino-terminal noncatalytic GAP region is critical for p120GAP-stimulated GTP hydrolysis. This is the first report of a Ras mutation which differentiates between p120GAP and neurofibromin activity.
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Affiliation(s)
- J Yoder-Hill
- Department of Molecular Biology, Cleveland Clinic Foundation, Ohio 44195, USA
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16
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Wienecke R, König A, DeClue JE. Identification of tuberin, the tuberous sclerosis-2 product. Tuberin possesses specific Rap1GAP activity. J Biol Chem 1995; 270:16409-14. [PMID: 7608212 DOI: 10.1074/jbc.270.27.16409] [Citation(s) in RCA: 268] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Tuberous sclerosis (TSC) is a human genetic syndrome characterized by the development of benign tumors in a variety of tissues, as well as rare malignancies. Two different genetic loci have been implicated in TSC; one of these loci, the tuberous sclerosis-2 gene (TSC2), encodes an open reading frame with a putative protein product of 1784 amino acids. The putative TSC2 product (tuberin) contains a region of limited homology to the catalytic domain of Rap1GAP. We have generated antisera against the N-terminal and C-terminal portions of tuberin, and these antisera specifically recognize a 180-kDa protein in immunoprecipitation and immunoblotting analyses. A wide variety of human cell lines express the 180-kDa tuberin protein, and subcellular fractionation revealed that most tuberin is found in a membrane/particulate (100,000 x g) fraction. Immunoprecipitates of native tuberin contain an activity that specifically stimulates the intrinsic GTPase activity of Rap1a. These results were confirmed in assays with a C-terminal fragment of tuberin, expressed in bacteria or Sf9 cells. Tuberin did not stimulate the GTPase activity of Rap2, Ha-Ras, Rac, or Rho. These results suggest that the loss of tuberin leads to constitutive activation of Rap1 in tumors of patients with tuberous sclerosis.
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Affiliation(s)
- R Wienecke
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, Maryland 20892-4040, USA
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17
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Schaber MD, Gibbs JB. Determination of Ras and GTPase-activating protein interactions by kinetic competition assay. Methods Enzymol 1995; 255:171-8. [PMID: 8524101 DOI: 10.1016/s0076-6879(95)55021-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- M D Schaber
- Department of Cancer Research, Merck Research Laboratories, West Point, Pennsylvania 19486, USA
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18
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Burney TL, Rockove S, Eiseman JL, Jacobs SC, Kyprianou N. Partial growth suppression of human prostate cancer cells by the Krev-1 suppressor gene. Prostate 1994; 25:177-88. [PMID: 8084835 DOI: 10.1002/pros.2990250403] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A series of functional studies were performed to assess the potential role of the ras-related transformation suppressor gene, Krev-1, in suppressing prostate cancer cell growth. Three human prostate cancer cell lines, PC-3, TSU-Pr1, and DU-145 were transfected with a plasmid containing the Krev-1 cDNA and a neomycin resistance gene. Selected G418-resistant clones were isolated and expanded into cell lines. All cloned transfectants exhibited a significant reduction in their in vitro growth rates, i.e., longer doubling times, when compared to the parental cell lines. Molecular analysis of the Krev-1 cloned transfectants revealed that they all contained variable copy numbers of the Krev-1 gene and expressed high levels of Krev-1 mRNA transcript, as shown by Southern and Northern analysis, respectively. To determine whether the biological properties associated with tumorigenicity were changed in these Krev-1 transfectants, their growth characteristics were examined on the basis of their ability to a) form colonies in soft agar, and b) produce tumors in SCID mice. The majority of the Krev-1 transfectants from the PC-3 and TSU-Pr1 cell lines showed a substantially reduced ability to form colonies in soft agar and produced significantly smaller tumors when inoculated into SCID mice. In contrast, there was no significant reduction in the soft agar colony-forming ability or in vivo tumorigenicity of the DU-145 Krev-1 transfectants. These results suggest that the Krev-1 suppressor gene induces partial suppression of the malignant phenotype of human prostate cancer cells containing activated ras oncogenes.
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MESH Headings
- Adenocarcinoma/genetics
- Adenocarcinoma/pathology
- Animals
- Blotting, Northern
- Blotting, Southern
- Blotting, Western
- Cell Division
- DNA, Neoplasm/analysis
- DNA, Neoplasm/physiology
- GTP-Binding Proteins/biosynthesis
- GTP-Binding Proteins/genetics
- Gene Expression Regulation, Neoplastic
- Genes, Tumor Suppressor
- Genes, ras
- Humans
- Male
- Mice
- Mice, SCID
- Prostatic Neoplasms/genetics
- Prostatic Neoplasms/pathology
- Proto-Oncogene Proteins p21(ras)/biosynthesis
- RNA, Messenger/analysis
- RNA, Neoplasm/analysis
- Transfection
- Tumor Cells, Cultured
- rap GTP-Binding Proteins
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Affiliation(s)
- T L Burney
- Department of Surgery, University of Maryland School of Medicine, Baltimore
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19
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Affiliation(s)
- L Wiesmüller
- Heinrich-Pette-Institut für exp. Virologie und Immunologie, Universität Hamburg, F.R.G
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20
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Wood D, Poullet P, Wilson B, Khalil M, Tanaka K, Cannon J, Tamanoi F. Biochemical characterization of yeast RAS2 mutants reveals a new region of ras protein involved in the interaction with GTPase-activating proteins. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37690-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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21
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Abstract
Genetic, physical and biochemical methods have been used successfully to identify discrete regions of the p21ras protein involved in protein-protein interactions. Of special interest are the effector residues of p21ras, which are essential for downstream signalling. This review details current understanding of what these residues are and how they bind and activate proteins essential to the ras pathway.
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Affiliation(s)
- M S Marshall
- Department of Medicine, Indiana University School of Medicine, Indianapolis
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22
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Johnson MR, Look AT, DeClue JE, Valentine MB, Lowy DR. Inactivation of the NF1 gene in human melanoma and neuroblastoma cell lines without impaired regulation of GTP.Ras. Proc Natl Acad Sci U S A 1993; 90:5539-43. [PMID: 8516298 PMCID: PMC46756 DOI: 10.1073/pnas.90.12.5539] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The NF1 gene, which is altered in patients with type 1 neurofibromatosis, encodes neurofibromin, a protein whose GTPase-activating function can negatively regulate GTP-Ras by accelerating its conversion to inactive GDP-Ras. In schwannoma cell lines from patients with neurofibromatosis, loss of neurofibromin was previously shown to be associated with impaired regulation of GTP-Ras. Our analysis of other neural crest-derived tumor cell lines has shown that some melanoma and neuroblastoma cell lines established from tumors occurring in patients without neurofibromatosis contain reduced or undetectable levels of neurofibromin, with concomitant genetic abnormalities of the NF1 locus. In contrast to the schwannoma cell lines, GTP-Ras was appropriately regulated in the melanoma and neuroblastoma lines that were deficient in neurofibromin, even when c-H-ras was overexpressed in the lines. These results demonstrate that some neural crest tumors not associated with neurofibromatosis have acquired somatically inactivated NF1 genes and suggest a tumor-suppressor function for neurofibromin that is independent of Ras GTPase activation.
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MESH Headings
- Blotting, Northern
- Blotting, Southern
- DNA, Neoplasm/genetics
- DNA, Neoplasm/isolation & purification
- GTPase-Activating Proteins
- Gene Expression
- Gene Expression Regulation, Neoplastic
- Genes, Neurofibromatosis 1
- Genes, ras
- Guanine Nucleotides/metabolism
- Humans
- In Situ Hybridization, Fluorescence
- Kinetics
- Melanoma
- Neuroblastoma
- Neurofibromin 1
- Phosphates/metabolism
- Protein Biosynthesis
- Proteins/genetics
- RNA, Messenger/isolation & purification
- RNA, Messenger/metabolism
- RNA, Neoplasm/genetics
- RNA, Neoplasm/isolation & purification
- Tumor Cells, Cultured
- ras GTPase-Activating Proteins
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Affiliation(s)
- M R Johnson
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, MD 20892
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23
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Noda M. Structures and functions of the K rev-1 transformation suppressor gene and its relatives. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1155:97-109. [PMID: 8504133 DOI: 10.1016/0304-419x(93)90024-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- M Noda
- Department of Viral Oncology, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan
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24
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Polakis P, McCormick F. Structural requirements for the interaction of p21ras with GAP, exchange factors, and its biological effector target. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)98325-0] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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25
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Burstein E, Brondyk W, Macara I. Amino acid residues in the Ras-like GTPase Rab3A that specify sensitivity to factors that regulate the GTP/GDP cycling of Rab3A. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)50006-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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26
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Functional interaction between p21rap1A and components of the budding pathway in Saccharomyces cerevisiae. Mol Cell Biol 1992. [PMID: 1508205 DOI: 10.1128/mcb.12.9.4084] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The rap1A gene encodes a 21-kDa, ras-related GTP-binding protein (p21rap1A) of unknown function. A close structural homolog of p21rap1A (65% identity in the amino-terminal two-thirds) is the RSR1 gene product (Rsr1p) of Saccharomyces cerevisiae. Although Rsr1p is not essential for growth, its presence is required for nonrandom selection of bud sites. To assess the similarity of these proteins at the functional level, wild-type and mutant forms of p21rap1A were tested for complementation of activities known to be fulfilled by Rsr1p. Expression of p21rap1A, like multicopy expression of RSR1, suppressed the conditional lethality of a temperature-sensitive cdc24 mutation. Point mutations predicted to affect the localization of p21rap1A or its ability to cycle between GDP and GTP-bound states disrupted suppression of cdc24ts, while other mutations in the 61-65 loop region improved suppression. Expression of p21rap1A could not, however, suppress the random budding phenotype of rsr1 cells. p21rap1A also apparently interfered with the normal activity of Rsrlp, causing random budding in diploid wild-type cells, suggesting an inability of p21rap1A to interact appropriately with Rsr1p regulatory proteins. Consistent with this hypothesis, we found an Rsr1p-specific GTPase-activating protein (GAP) activity in yeast membranes which was not active toward p21rap1A, indicating that p21rap1A may be predominantly GTP bound in yeast cells. Coexpression of human Rap1-specific GAP suppressed the random budding due to expression of p21rap1A or its derivatives, including Rap1AVal-12. Although Rap1-specific GAP stimulated the GTPase of Rsr1p in vitro, it did not dominantly interfere with Rsr1p function in vivo. A chimera consisting of Rap1A1-165::Rsr1p166-272 did not exhibit normal Rsr1p function in the budding pathway. These results indicated that p21rap1A and Rsr1p share at least partial functional homology, which may have implications for p21rap1A function in mammalian cells.
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27
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McCabe PC, Haubruck H, Polakis P, McCormick F, Innis MA. Functional interaction between p21rap1A and components of the budding pathway in Saccharomyces cerevisiae. Mol Cell Biol 1992; 12:4084-92. [PMID: 1508205 PMCID: PMC360304 DOI: 10.1128/mcb.12.9.4084-4092.1992] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The rap1A gene encodes a 21-kDa, ras-related GTP-binding protein (p21rap1A) of unknown function. A close structural homolog of p21rap1A (65% identity in the amino-terminal two-thirds) is the RSR1 gene product (Rsr1p) of Saccharomyces cerevisiae. Although Rsr1p is not essential for growth, its presence is required for nonrandom selection of bud sites. To assess the similarity of these proteins at the functional level, wild-type and mutant forms of p21rap1A were tested for complementation of activities known to be fulfilled by Rsr1p. Expression of p21rap1A, like multicopy expression of RSR1, suppressed the conditional lethality of a temperature-sensitive cdc24 mutation. Point mutations predicted to affect the localization of p21rap1A or its ability to cycle between GDP and GTP-bound states disrupted suppression of cdc24ts, while other mutations in the 61-65 loop region improved suppression. Expression of p21rap1A could not, however, suppress the random budding phenotype of rsr1 cells. p21rap1A also apparently interfered with the normal activity of Rsrlp, causing random budding in diploid wild-type cells, suggesting an inability of p21rap1A to interact appropriately with Rsr1p regulatory proteins. Consistent with this hypothesis, we found an Rsr1p-specific GTPase-activating protein (GAP) activity in yeast membranes which was not active toward p21rap1A, indicating that p21rap1A may be predominantly GTP bound in yeast cells. Coexpression of human Rap1-specific GAP suppressed the random budding due to expression of p21rap1A or its derivatives, including Rap1AVal-12. Although Rap1-specific GAP stimulated the GTPase of Rsr1p in vitro, it did not dominantly interfere with Rsr1p function in vivo. A chimera consisting of Rap1A1-165::Rsr1p166-272 did not exhibit normal Rsr1p function in the budding pathway. These results indicated that p21rap1A and Rsr1p share at least partial functional homology, which may have implications for p21rap1A function in mammalian cells.
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Affiliation(s)
- P C McCabe
- Department of Molecular Biology, Cetus Corporation, Emeryville, California 94608
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28
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Paietta E, Stockert R, Racevskis J. Alternatively spliced variants of the human hepatic asialoglycoprotein receptor, H2, differ in cellular trafficking and regulation of phosphorylation. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)49877-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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29
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30
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DeClue JE, Papageorge AG, Fletcher JA, Diehl SR, Ratner N, Vass WC, Lowy DR. Abnormal regulation of mammalian p21ras contributes to malignant tumor growth in von Recklinghausen (type 1) neurofibromatosis. Cell 1992; 69:265-73. [PMID: 1568246 DOI: 10.1016/0092-8674(92)90407-4] [Citation(s) in RCA: 459] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Tumor cell lines derived from malignant schwannomas removed from patients with neurofibromatosis type 1 (NF1) have been examined for the level of expression of NF1 protein. All three NF1 lines examined expressed lower levels of NF1 protein than control cells, and the level in one line was barely detectable. The tumor lines expressed normal levels of p120GAP and p21ras. Although the p21ras proteins isolated from the tumor cells had normal (nonmutant) biochemical properties in vitro, they displayed elevated levels of bound GTP in vivo. The level of total cellular GAP-like activity was reduced in extracts from the tumor line that expresses very little NF1 protein. Introduction of the catalytic region of GAP into this line resulted in morphological reversion and lower in vivo GTP binding by endogenous p21ras. These data implicate NF1 protein as a tumor suppressor gene product that negatively regulates p21ras and define a "positive" growth role for ras activity in NF1 malignancies.
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Affiliation(s)
- J E DeClue
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, Maryland 20892
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