title: Ligand-induced internalization and increased cell calcium are mediated via distinct structural elements in the carboxyl terminus of the epidermal growth factor receptor.
abstract: Signals that can mediate ligand-induced receptor internalization and calcium regulation are present in a 48-amino acid "calcium-internalization" domain in the C' terminus of the epidermal growth factor (EGF) receptor. The basis of calcium and internalization regulation signalled by this 48-amino acid sequence was analyzed using deletion and substitution mutant receptors. Cells expressing truncated receptors containing either the NH2- or COOH-terminal portion of the 48-residue domain displayed high affinity EGF-dependent endocytosis and receptor down-regulation. These endocytosis-competent EGF receptor mutants that lacked any autophosphorylation site were unable to increase the concentration of intracellular calcium. To investigate the role of self-phosphorylation in EGF-induced calcium mobilization, phenylalanine was substituted for the single autophosphorylated tyrosine residue in this region of an internalization-competent truncated receptor. The receptor-mediated calcium response was abolished, while ligand-dependent receptor internalization was unimpaired. These results demonstrate that EGF-dependent receptor endocytosis and calcium mobilization are separate events. Tyrosine self-phosphorylation is required for increased [Ca2+]i, while structural features distinct from autophosphorylation are required for receptor internalization.
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla 92093.
authors.forename: C P
authors.initials: CP
authors.lastname: Chang
authors.forename: J P
authors.initials: JP
authors.lastname: Kao
authors.forename: C S
authors.initials: CS
authors.lastname: Lazar
authors.forename: B J
authors.initials: BJ
authors.lastname: Walsh
authors.forename: A
authors.initials: A
authors.lastname: Wells
authors.forename: H S
authors.initials: HS
authors.lastname: Wiley
authors.forename: G N
authors.initials: GN
authors.lastname: Gill
authors.forename: M G
authors.initials: MG
authors.lastname: Rosenfeld
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D015536:Down-Regulation; D004705:Endocytosis; D066246:ErbB Receptors / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D051379:Mice; D010766:Phosphorylation
chemical_list: D008024:Ligands; D066246:ErbB Receptors; D002118:Calcium