TY - JOUR
T1 - Ras-independent oncogenic transformation by an EGF-receptor mutant
AU - Boerner, Julie L.
AU - McManus, Michael J.
AU - Martin, G. Steven
AU - Maihle, Nita J.
PY - 2000
Y1 - 2000
N2 - Mutations in the ligand-binding domain of the epidermal growth factor receptor have been identified in several types of human cancers, including malignant gliomas. These mutations render signaling by this receptor to be constitutively ligand-independent. In fibroblasts transformed with ligand-independent epidermal growth factor receptor mutants, there is a correlation between the formation of a unique phosphotyrosine protein complex and oncogenic transformation. This phosphoprotein complex includes Grb2, Shc, Sos, tyrosine-phosphorylated form of caldesmon, and two, as yet, unidentified proteins. The presence of Grb2, Shc, and Sos in this complex implicates Ras in ligand-independent signaling by these oncogenic epidermal growth factor receptor mutants. We, therefore, have used retroviral co-infections of cultured primary fibroblasts to determine if Ras activation is required for phosphoprotein complex formation, stress fiber loss, or transformation. As predicted, expression of a dominant-negative Ras mutant (N17Ras) completely abrogates ligand-stimulated soft agar colony growth of primary fibroblasts. In contrast, N17Ras expression has no effect on v-ErbB mediated stress fiber disassembly, soft agar colony growth, or phosphoprotein complex assembly. In addition, our data suggest that ligand-dependent Ras activation may be suppressed by oncogenic v-ErbB expression. Together these observations suggest that oncogenic signaling by v-ErbB does not require Ras activation, and implicate an alternative signal transduction pathway in ligand-independent epidermal growth factor receptor oncogenic signaling.
AB - Mutations in the ligand-binding domain of the epidermal growth factor receptor have been identified in several types of human cancers, including malignant gliomas. These mutations render signaling by this receptor to be constitutively ligand-independent. In fibroblasts transformed with ligand-independent epidermal growth factor receptor mutants, there is a correlation between the formation of a unique phosphotyrosine protein complex and oncogenic transformation. This phosphoprotein complex includes Grb2, Shc, Sos, tyrosine-phosphorylated form of caldesmon, and two, as yet, unidentified proteins. The presence of Grb2, Shc, and Sos in this complex implicates Ras in ligand-independent signaling by these oncogenic epidermal growth factor receptor mutants. We, therefore, have used retroviral co-infections of cultured primary fibroblasts to determine if Ras activation is required for phosphoprotein complex formation, stress fiber loss, or transformation. As predicted, expression of a dominant-negative Ras mutant (N17Ras) completely abrogates ligand-stimulated soft agar colony growth of primary fibroblasts. In contrast, N17Ras expression has no effect on v-ErbB mediated stress fiber disassembly, soft agar colony growth, or phosphoprotein complex assembly. In addition, our data suggest that ligand-dependent Ras activation may be suppressed by oncogenic v-ErbB expression. Together these observations suggest that oncogenic signaling by v-ErbB does not require Ras activation, and implicate an alternative signal transduction pathway in ligand-independent epidermal growth factor receptor oncogenic signaling.
KW - Chicken embryo fibroblast
KW - Dominant-negative Ras
KW - Stress fiber
KW - V-ErbB
UR - http://www.scopus.com/inward/record.url?scp=0034071737&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034071737&partnerID=8YFLogxK
M3 - Article
C2 - 10683142
AN - SCOPUS:0034071737
SN - 0021-9533
VL - 113
SP - 935
EP - 942
JO - Journal of Cell Science
JF - Journal of Cell Science
IS - 6
ER -