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ERK and JNK activation is essential for oncogenic transformation by v-Rel.

Kralova J, Sheely JI, Liss AS, Bose HR - Oncogene (2010)

Bottom Line: The expression of v-Rel results in the strong and sustained activation of the ERK and JNK MAPK pathways.MAPK signaling also has an important role in the initial transformation of primary spleen cells by v-Rel, although distinct requirements for MAPK activity at different stages of v-Rel-mediated transformation were identified.We also show that the ability of v-Rel to induce MAPK signaling more strongly than c-Rel contributes to its greater oncogenicity.

View Article: PubMed Central - PubMed

Affiliation: Section of Molecular Genetics and Microbiology, Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, USA.

ABSTRACT
v-Rel is the acutely oncogenic member of the NF-κB family of transcription factors. Infection with retroviruses expressing v-Rel rapidly induces fatal lymphomas in birds and transforms primary lymphocytes and fibroblasts in vitro. We have previously shown that AP-1 transcriptional activity contributes to v-Rel-mediated transformation. Although v-Rel increases the expression of these factors, their activity may also be induced through phosphorylation by the mitogen-activated protein kinases (MAPKs). The expression of v-Rel results in the strong and sustained activation of the ERK and JNK MAPK pathways. This induction is critical for the v-Rel-transformed phenotype, as suppression of MAPK activity with chemical inhibitors or small interfering RNA severely impairs colony formation of v-Rel-transformed lymphoid cell lines. However, signaling must be maintained within an optimal range in these cells, as strong additional activation of either pathway beyond the levels induced by v-Rel through the expression of constitutively active MAPK proteins attenuates the transformed phenotype. MAPK signaling also has an important role in the initial transformation of primary spleen cells by v-Rel, although distinct requirements for MAPK activity at different stages of v-Rel-mediated transformation were identified. We also show that the ability of v-Rel to induce MAPK signaling more strongly than c-Rel contributes to its greater oncogenicity.

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Induction of the ERK and JNK MAPK pathways by v-Rel. Chicken embryo fibroblasts (CEFs) or DT40 cells were left uninfected (−) or were infected with helper virus alone (H) or with retroviruses expressing c-Rel (C) or v-Rel (V). Cell lysates were prepared 7–10 days later, when cells expressing v-Rel exhibited characteristic morphological changes. Western blot analysis examined the levels of total and phosphorylated protein for components of the (a) ERK, (b) JNK, and (c) p38 MAPK signaling cascades. The expression of c-Rel and v-Rel in these cells is shown in panel (a).
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Figure 1: Induction of the ERK and JNK MAPK pathways by v-Rel. Chicken embryo fibroblasts (CEFs) or DT40 cells were left uninfected (−) or were infected with helper virus alone (H) or with retroviruses expressing c-Rel (C) or v-Rel (V). Cell lysates were prepared 7–10 days later, when cells expressing v-Rel exhibited characteristic morphological changes. Western blot analysis examined the levels of total and phosphorylated protein for components of the (a) ERK, (b) JNK, and (c) p38 MAPK signaling cascades. The expression of c-Rel and v-Rel in these cells is shown in panel (a).

Mentions: We examined the activation of the major MAPK cascades in cells expressing c-Rel or v-Rel. Chicken embryo fibroblasts (CEFs) and the avian B-cell line, DT40, were infected with helper virus alone (chick syntitial virus, CSV) or with retroviruses expressing c-Rel (REV-C) or v-Rel (REV-TW). Cell lysates were prepared following morphological transformation of cells expressing v-Rel. The activity of the MAPK pathway components was determined by measuring their phosphorylation status, including the levels of active, phosphorylated ERK, JNK, and p38. Cells expressing v-Rel exhibited high levels of ERK and JNK phosphorylation in both cell types relative to uninfected or CSV-infected cells, while total protein levels remained unchanged (Figure 1a, Figure 1b). In contrast, v-Rel activation of p38 was not as dramatic and was primarily limited to DT40 cells (Figure 1c). The phosphorylation of downstream targets of ERK (RSK) and JNK (c-Jun) correlated with the activation of their respective kinases in v-Rel-expressing cells. While v-Rel expression increased the total levels of c-Jun (1.5–1.6 fold) compared to uninfected cells, the levels of phosphorylated c-Jun normalized to total levels were also elevated (~1.7 fold). Further, the phosphorylation levels of the upstream kinases for ERK (MKK1/2) and JNK (MKK4/7) were also increased, thereby suggesting activation of the entire MAPK signaling cascades in cells expressing v-Rel. In comparison to v-Rel expression in these cells, the overexpression of c-Rel resulted in a smaller and sometimes non-detectable increase in MAPK phosphorylation at each level of these cascades, suggesting that a difference in MAPK activation contributes to the stronger oncogenicity of v-Rel. Similar data were obtained in the DT95 B-cell line (Supplemental Figure 1).


ERK and JNK activation is essential for oncogenic transformation by v-Rel.

Kralova J, Sheely JI, Liss AS, Bose HR - Oncogene (2010)

Induction of the ERK and JNK MAPK pathways by v-Rel. Chicken embryo fibroblasts (CEFs) or DT40 cells were left uninfected (−) or were infected with helper virus alone (H) or with retroviruses expressing c-Rel (C) or v-Rel (V). Cell lysates were prepared 7–10 days later, when cells expressing v-Rel exhibited characteristic morphological changes. Western blot analysis examined the levels of total and phosphorylated protein for components of the (a) ERK, (b) JNK, and (c) p38 MAPK signaling cascades. The expression of c-Rel and v-Rel in these cells is shown in panel (a).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2992084&req=5

Figure 1: Induction of the ERK and JNK MAPK pathways by v-Rel. Chicken embryo fibroblasts (CEFs) or DT40 cells were left uninfected (−) or were infected with helper virus alone (H) or with retroviruses expressing c-Rel (C) or v-Rel (V). Cell lysates were prepared 7–10 days later, when cells expressing v-Rel exhibited characteristic morphological changes. Western blot analysis examined the levels of total and phosphorylated protein for components of the (a) ERK, (b) JNK, and (c) p38 MAPK signaling cascades. The expression of c-Rel and v-Rel in these cells is shown in panel (a).
Mentions: We examined the activation of the major MAPK cascades in cells expressing c-Rel or v-Rel. Chicken embryo fibroblasts (CEFs) and the avian B-cell line, DT40, were infected with helper virus alone (chick syntitial virus, CSV) or with retroviruses expressing c-Rel (REV-C) or v-Rel (REV-TW). Cell lysates were prepared following morphological transformation of cells expressing v-Rel. The activity of the MAPK pathway components was determined by measuring their phosphorylation status, including the levels of active, phosphorylated ERK, JNK, and p38. Cells expressing v-Rel exhibited high levels of ERK and JNK phosphorylation in both cell types relative to uninfected or CSV-infected cells, while total protein levels remained unchanged (Figure 1a, Figure 1b). In contrast, v-Rel activation of p38 was not as dramatic and was primarily limited to DT40 cells (Figure 1c). The phosphorylation of downstream targets of ERK (RSK) and JNK (c-Jun) correlated with the activation of their respective kinases in v-Rel-expressing cells. While v-Rel expression increased the total levels of c-Jun (1.5–1.6 fold) compared to uninfected cells, the levels of phosphorylated c-Jun normalized to total levels were also elevated (~1.7 fold). Further, the phosphorylation levels of the upstream kinases for ERK (MKK1/2) and JNK (MKK4/7) were also increased, thereby suggesting activation of the entire MAPK signaling cascades in cells expressing v-Rel. In comparison to v-Rel expression in these cells, the overexpression of c-Rel resulted in a smaller and sometimes non-detectable increase in MAPK phosphorylation at each level of these cascades, suggesting that a difference in MAPK activation contributes to the stronger oncogenicity of v-Rel. Similar data were obtained in the DT95 B-cell line (Supplemental Figure 1).

Bottom Line: The expression of v-Rel results in the strong and sustained activation of the ERK and JNK MAPK pathways.MAPK signaling also has an important role in the initial transformation of primary spleen cells by v-Rel, although distinct requirements for MAPK activity at different stages of v-Rel-mediated transformation were identified.We also show that the ability of v-Rel to induce MAPK signaling more strongly than c-Rel contributes to its greater oncogenicity.

View Article: PubMed Central - PubMed

Affiliation: Section of Molecular Genetics and Microbiology, Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, USA.

ABSTRACT
v-Rel is the acutely oncogenic member of the NF-κB family of transcription factors. Infection with retroviruses expressing v-Rel rapidly induces fatal lymphomas in birds and transforms primary lymphocytes and fibroblasts in vitro. We have previously shown that AP-1 transcriptional activity contributes to v-Rel-mediated transformation. Although v-Rel increases the expression of these factors, their activity may also be induced through phosphorylation by the mitogen-activated protein kinases (MAPKs). The expression of v-Rel results in the strong and sustained activation of the ERK and JNK MAPK pathways. This induction is critical for the v-Rel-transformed phenotype, as suppression of MAPK activity with chemical inhibitors or small interfering RNA severely impairs colony formation of v-Rel-transformed lymphoid cell lines. However, signaling must be maintained within an optimal range in these cells, as strong additional activation of either pathway beyond the levels induced by v-Rel through the expression of constitutively active MAPK proteins attenuates the transformed phenotype. MAPK signaling also has an important role in the initial transformation of primary spleen cells by v-Rel, although distinct requirements for MAPK activity at different stages of v-Rel-mediated transformation were identified. We also show that the ability of v-Rel to induce MAPK signaling more strongly than c-Rel contributes to its greater oncogenicity.

Show MeSH
Related in: MedlinePlus