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

Report Date:

1995-05-17

Pagination or Media Count:

10.0

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 substrates 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 substrates 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.

Subject Categories:

  • Medicine and Medical Research

Distribution Statement:

APPROVED FOR PUBLIC RELEASE