Active Akt and Functional p53 Modulate Apoptosis in Abelson Virus-Transformed Pre-B Cells

Gong, Lilin; Unnikrishnan, Indira; Raghavan, Anuradha S.; Parmar, Kalindi; Rosenberg, Naomi

doi:10.1128/jvi.78.4.1636-1644.2004

Cited by 6 publications

(5 citation statements)

References 58 publications

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“…To determine if the mutants that fail to transform pre-B cells are capable of affecting the growth or survival of pre-B cells, the ability of these proteins to substitute for the v-Abl protein encoded by the temperaturesensitive P70/H590 mutant Ab-MLV strain was examined (5,8). 7C411 cells, which grow normally at the permissive temperature but not at 39.5°C, the nonpermissive temperature for the P70/H590 mutant, were infected with wild-type virus and the different mutants, and the infected cells were recovered by sorting the populations on the basis of GFP expression.…”

Section: Resultsmentioning

confidence: 99%

Gag Influences Transformation by Abelson Murine Leukemia Virus and Suppresses Nuclear Localization of the v-Abl Protein

Yi¹,

Rosenberg

2007

J Virol

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Like the v-Onc proteins encoded by many transforming retroviruses, the v-Abl protein is expressed as a Gag-Onc fusion. Although the Gag-derived myristoylation signal targets the v-Abl protein to the plasma membrane, the protein contains the entire MA and p12 sequences and a small number of CA-derived residues. To understand the role of Gag sequences in transformation, mutants lacking portions of these sequences were examined for the effects of these deletions on v-Abl function and localization. Deletion of the N-terminal third of p12 or all of p12 enhanced the transformation of both pre-B cells and NIH 3T3 cells. In contrast, deletions in MA or a deletion removing all of Gag except the first 34 amino acids important for myristoylation highly compromised the ability to transform either cell type. Although all of the mutant proteins retained kinase activity, those defective in transformation were reduced in their ability to activate Erk, suggesting a role for Gag sequences in v-Abl signaling. Immunofluorescence analysis revealed that a v-Abl protein retaining only the first 34 amino acids of Gag localized to the nucleus. These data indicate that Gag sequences are important for normal v-Abl signaling and that they suppress nuclear localization of the molecule.Abelson murine leukemia virus (Ab-MLV) is a replicationdefective retrovirus that arose spontaneously from a recombination between Moloney MLV (Mo-MLV) and the c-abl proto-oncogene. As a result, sequences from the retroviral gag gene and the cellular c-abl gene were fused, leading to the production of a single gene product. The v-Abl protein encoded by this gene is a nonreceptor tyrosine kinase, and its expression induces pre-B-cell lymphoma in mice and transforms NIH 3T3 and pre-B cells in vitro (26,29). The ablderived sequences contain the catalytic domain, the SH2 domain that is important for binding to tyrosine-phosphorylated proteins, and the carboxyl terminus that functions to strongly enhance the transformation of pre-B cells (16,17). Intact tyrosine kinase activity and the SH2 domain are required for transformation by 14,26).Despite the importance of abl-encoded sequences in Ab-MLV transformation, the Gag domain, which contains the entire MA and p12 regions, a small portion of CA, and a myristoylation signal, has long been appreciated as playing an important role in this process. An analysis of mutants with insertions in gag showed that the integrity of the region is important for Ab-MLV-mediated transformation of NIH 3T3 cells (22). A v-Abl protein that lacks the myristoylation signal fails to transform NIH 3T3 cells but still stimulates the growth of a factor-dependent hematopoietic cell line (3), a phenotype associated with loss of plasma membrane localization. Other experiments have also highlighted the importance of the myristoylation signal and the residues at the extreme amino terminus of the protein. For example, mutants that encode v-Abl proteins containing only the first 34 amino acids of Gag, including the myristoylation signal, or those that...

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Section: Resultsmentioning

confidence: 99%

Gag Influences Transformation by Abelson Murine Leukemia Virus and Suppresses Nuclear Localization of the v-Abl Protein

Yi¹,

Rosenberg

2007

J Virol

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“…These data, coupled with the results presented earlier, suggest that Shc affects v-Abl-mediated transformation by reducing signals transmitted to Ras and downstream to the MAP kinase pathway via the Raf protein. (17,26). The ability of the Mek inhibitor PD98059 to block growth without disrupting cell survival also supports a critical role for the MAP kinase cascade in this aspect of Ab-MLV transformation.…”

Section: Dn Shc Alters Ras Activation Activation Of Ras Is Critical mentioning

confidence: 92%

“…In addition, Shc binds P120/R273K at a reduced level (26). This mutant form of v-Abl retains its ability to block apoptosis but is compromised in its ability to stimulate growth of cells (17,26), suggesting that Shc may be particularly important for v-Abl-induced proliferation. To test this idea directly and to probe the nature of the signals that pass from v-Abl through Shc to downstream effector proteins, we studied transformation of pre-B cells coexpressing Ab-MLV and dominant-negative (DN) mutants of Shc.…”

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confidence: 99%

Disruption of the Shc/Grb2 Complex during Abelson Virus Transformation Affects Proliferation, but Not Apoptosis

Baughn¹,

Rosenberg²

2005

J Virol

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(26,30,43). The SH2 domain contains the FLVRES motif that forms a phosphotyrosine-binding pocket involved in protein-protein associations. Disruption of the v-Abl SH2 domain results in defects in cell transformation, suggesting that signaling cascades influenced by the SH2 domain affect multiple pathways (26,52). Although the v-Abl SH2 domain has been associated with signaling to the Ras, PI3-K, and c-Myc pathways (reviewed in reference 66), the ways that particular SH2 binding proteins transmit signals downstream from this domain have not been elucidated.The adaptor protein Shc is one molecule that binds to the SH2 domain of v-Abl. Once bound, Shc becomes tyrosine phosphorylated (35, 38) and associates with Grb2/Sos, a complex that can activate Ras. Association with Grb2 requires phosphorylation of Y239, 240, and 313, three tyrosines located in the CH1 domain of Shc (20,25). These residues become phosphorylated upon activation of several different receptors and are probably targets of v-Abl (reviewed in reference 40). Shc phosphorylation can promote cell growth and survival depending on the cell type and context, and multiple pathways, including those involving Ras/mitogen-activated protein (MAP) kinase and PI3-K/Akt, can be affected (18,19,24,32).In addition to Ab-MLV-mediated transformation, Shc proteins have been implicated in Ret/Ptc2, Trk-T3, ErbB2, and polyomavirus middle-T transformation, and hyperphosphorylation of Shc has been documented for several types of cancer (4,31,37,53).Shc influences Ras and Myc, two molecules required for Ab-MLV transformation, (16,47,48), reinforcing the possible functional link between v-Abl and Shc. In addition, Shc binds P120/R273K at a reduced level (26). This mutant form of v-Abl retains its ability to block apoptosis but is compromised in its ability to stimulate growth of cells (17,26), suggesting that Shc may be particularly important for v-Abl-induced proliferation. To test this idea directly and to probe the nature of the signals that pass from v-Abl through Shc to downstream effector proteins, we studied transformation of pre-B cells coexpressing Ab-MLV and dominant-negative (DN) mutants of Shc. These experiments revealed that Shc function is important for transformation and influences growth by transmitting signals that integrate downstream with the Ras-Raf-MAP kinase pathway. MATERIALS AND METHODS Cells and viruses.293T and COS7 cells were grown in Dulbecco's modified Eagle's medium (Gibco) supplemented to contain 10% fetal calf serum (Sigma) and 2 mM L-glutamine (Gibco). NIH 3T3 cells were grown in Dulbecco's modified Eagle's medium supplemented to contain 10% calf serum (Sigma) and 2 mM L-glutamine. Ab-MLV-transformed pre-B cells were grown in RPMI 1640 medium (Gibco) supplemented to contain 20% fetal calf serum, 2 mM L-glutamine, and 50 M 2-mercaptoethanol (Sigma). Viral stocks were prepared by transfection of 293T cells as described elsewhere (26,63) and titered by infecting NIH 3T3 cells with 0.5 ml of virus containing 8 g of Polybrene (Sigma)/ml. The cell...

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“…For example, previous results suggested that v-Abl-induced AKT activation is a critical signaling pathway in v-Abl-induced cytokine-independent cell growth (Oki et al, 2002). In addition, a report from other group showed that signal transmitted through AKT is important in modulating apoptosis in v-Abltransformed Pre-B cells (Gong et al, 2004). It has also been revealed that the PI3K/AKT pathway contributes to transformation by BCR-ABL (Skorski et al, 1997;Kharas et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Oncogenic E17K mutation in the pleckstrin homology domain of AKT1 promotes v-Abl-mediated pre-B-cell transformation and survival of Pim-deficient cells

et al. 2010

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Active Akt and Functional p53 Modulate Apoptosis in Abelson Virus-Transformed Pre-B Cells

Cited by 6 publications

References 58 publications

Gag Influences Transformation by Abelson Murine Leukemia Virus and Suppresses Nuclear Localization of the v-Abl Protein

Gag Influences Transformation by Abelson Murine Leukemia Virus and Suppresses Nuclear Localization of the v-Abl Protein

Disruption of the Shc/Grb2 Complex during Abelson Virus Transformation Affects Proliferation, but Not Apoptosis

Oncogenic E17K mutation in the pleckstrin homology domain of AKT1 promotes v-Abl-mediated pre-B-cell transformation and survival of Pim-deficient cells

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