Membrane localization of v-ErbB is required but not sufficient for ligand-independent transformation.
The v-ErbB retroviral oncogene is a transduced, mutated copy of the avian EGF receptor gene, and its expression is sufficient to induce tumor formation in vivo. The structural alterations that release the oncogenic potential of the v-ErbB oncogene are similar to EGFR gene mutations described in human tumors. Thus, the study of v-ErbB tumor biology offers a useful model through which we can gain insight into the mechanism of EGFR-induced malignancies. Despite years of study, however, questions remain regarding the domains of v-ErbB required for oncogenicity. We sought to clarify the role of the transmembrane domain of v-ErbB during transformation using S3-v-ErbB, an acutely transforming retroviral oncogene isolated from avian sarcomas. Infection of primary fibroblasts with a retroviral vector containing S3-v-ErbB results in the formation of a transformation-associated phosphoprotein signaling complex, soft agar colony formation, and the rapid induction of highly vascularized sarcomas in vivo. To address contribution of the transmembrane domain of S3-v-ErbB during these processes, we constructed a mutant version of this oncogene with a precise deletion in this domain. Specifically, the S3-v-ErbB-TM- mutant was created through an in-frame deletion of the entire transmembrane domain. Primary fibroblasts expressing this S3-v-ErbB-TM- mutant fail to form a characteristic transformation-associated phosphoprotein complex and do not grow in an anchorage-independent manner. In addition, day-old chicks injected with a helper-independent retrovirus expressing the S3-v-ErbB-TM- mutant exhibit only limited tumor formation in vivo. These results demonstrate that the transmembrane domain and, consequently membrane localization, are essential for S3-v-ErbB-mediated transformation.
Danielsen
Andrew J
AJ
Tumor Biology Program, Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA.
Christensen
Trace A
TA
Lovejoy
Courtney A
CA
Adelsman
Margaret A
MA
Connolly
Denise C
DC
Maihle
Nita J
NJ
D000818:Animals; D000831:Animals, Newborn; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D002642:Chick Embryo; D002645:Chickens; D005347:Fibroblasts; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009369:Neoplasms / Q000209:etiology; D018739:Oncogene Proteins v-erbB / Q000008:administration & dosage / Q000378:metabolism* / Q000502:physiology*; D021381:Protein Transport; D014170:Transformation, Genetic
D008024:Ligands; D018739:Oncogene Proteins v-erbB