Accession Number : ADA300531

Title :   Characterization of Ligand-Induced Endocytosis of EGF Receptors.

Descriptive Note : Annual rept. 9 May 94-8 May 95,

Corporate Author : SCRIPPS RESEARCH INST LA JOLLA CA

Personal Author(s) : Schmid, Sandra L. ; Lamaze, Christophe

PDF Url : ADA300531

Report Date : 17 MAY 1995

Pagination or Media Count : 10

Abstract : Down-regulation of activated EGF-receptors (EGF-R) requires their tyrosine kinase (Y-kinase) activity. However, controversy existed as to whether ligand-induced activation of the EGF-R Y-kinase was required for internalization or for lysosomal targeting. We have addressed this issue using a cell-free assay which selectively measures the recruitment of EGF-R into coated pits. While EGF bound to wild-type receptors is efficiently sequestered in coated pits, sequestration of kinase- deficient receptors occurs inefficiently and at the same basal rate of endocytosis of unoccupied receptors or receptors lacking any cytoplasmic domain. Sequestration of deletion mutants of the EGF-R which lack autophosphorylation sites also requires an active Y-kinase. Our results directly establish that the EGF-R Y-kinase is required for internalization. They further suggest that a kinase substrate(s) other than the EGF-R itself, is required for its efficient ligand-induced recruitment into coated pits. Finally we have developed a powerful functional assay for identification of these I substrate(s) based on our finding that the addition of a soluble EGF-R Y-kinase fully and specifically restores the recruitment of kinase-deficient EOF-R into coated pits.

Descriptors :   *LIGANDS, *MAMMARY GLANDS, *BREAST CANCER, CHELATION, SUBSTRATES, CYTOPLASM, TARGETING, CELLS(BIOLOGY), ASSAYING.

Subject Categories : Medicine and Medical Research

Distribution Statement : APPROVED FOR PUBLIC RELEASE