title: Mutations in the polybasic juxtamembrane sequence of both plasma membrane- and endoplasmic reticulum-localized epidermal growth factor receptors confer ligand-independent cell transformation.
abstract: Deregulation of ErbB receptor-tyrosine kinases is a hallmark of many human cancers. Conserved in the ErbB family is a cluster of basic amino acid residues in the cytoplasmic juxtamembrane region. We found that charge-silencing mutagenesis within this juxtamembrane region of the epidermal growth factor receptor (EGFR) results in the generation of a mutant receptor (EGFR Mut R1-6) that spontaneously transforms NIH 3T3 cells in a ligand-independent manner. A similar mutant with one additional basic residue, EGFR Mut R1-5, fails to exhibit ligand-independent transformation. The capacity of EGFR Mut R1-6 to mediate this transformation is maintained when this mutant is retained in the endoplasmic reticulum via a single point mutation, L393H, which we describe. We show that EGFR Mut R1-6 with or without L393H exhibits enhanced basal tyrosine phosphorylation when ectopically expressed, and the ligand-independent transforming activity of EGFR Mut R1-6 is sensitive to inhibition of EGFR kinase activity and is particularly dependent on PI3K and mTOR activity. Similar to EGFR Mut R1-6/L393H in NIH 3T3 cells, EGFR variant type III, a highly oncogenic mutant form of EGFR linked to human brain cancers, confers transforming activity while it is wholly endoplasmic reticulum-retained in U87 cells. Our findings highlight the importance of the polybasic juxtamembrane sequence in regulating the oncogenic potential of EGFR signaling.
authors.affiliation: From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853 and.
authors.forename: Kirsten L
authors.initials: KL
authors.lastname: Bryant
authors.forename: Marc A
authors.initials: MA
authors.lastname: Antonyak
authors.forename: Richard A
authors.initials: RA
authors.lastname: Cerione
authors.forename: Barbara
authors.initials: B
authors.lastname: Baird
authors.forename: David
authors.initials: D
authors.lastname: Holowka
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000235:genetics* / Q000473:pathology; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D053492:Elafin / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008024:Ligands; D051379:Mice; D009154:Mutation; D041681:NIH 3T3 Cells; D015398:Signal Transduction
chemical_list: D053492:Elafin; D008024:Ligands; C506806:PI3 protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors
keywords: Endoplasmic Reticulum (ER); Epidermal Growth Factor Receptor (EGFR); Oncogene; PI 3-Kinase (PI3K); Transformation