Effect of epidermal growth factor receptor internalization on regulation of the phospholipase C-γ1 signaling pathway

Jason M. Haugh, Kevin Schooler, Alan Wells, H. Steven Wiley, Douglas A. Lauffenburger

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99 Scopus citations

Abstract

The epidermal growth factor receptor (EGFR) ligands, epidermal growth factor (EGF), and transforming growth factor-α (TGFα) elicit differential postendocytic processing of ligand and receptor molecules, which impacts long-term cell signaling outcomes. These differences arise from the higher affinity of the EGF-EGFR interaction versus that of TGFα-EGFR in the acidic conditions of sorting endosomes. To determine whether EGFR occupancy in endosomes might also affect short-term signaling events, we examined activation of the phospholipase C-γ1 (PLC-γ1) pathway, an event shown to be essential for growth factor-induced cell motility. We found that EGF continues to stimulate maximal tyrosine phosphorylation of EGFR following internalization, while, as expected, TGFα stimulates markedly less. The resulting higher level of receptor activation by EGF, however, did not yield higher levels of phosphatidylinositol (4,5)-bisphosphate (PIP2) hydrolysis over those stimulated by TGFα. By altering the ratio of activated receptors between the cell surface and the internalized compartment, we found that only cell surface receptors effectively participate in PLC function. In contrast to PIP2 hydrolysis, PLC-γ1 tyrosine phosphorylation correlated linearly with the total level of Tyr(P)-EGFR stimulated by either ligand, indicating that the functional deficiency of internal EGFR cannot be attributed to an inability to interact with and phosphorylate signaling proteins. We conclude that EGFR signaling through the PLC pathway is spatially restricted at a point between PLC-γ1 phosphorylation and PIP2 hydrolysis, perhaps because of limited access of EGFR-bound PLC-γ1 to its substrate in endocytic trafficking organelles.

Original languageEnglish (US)
Pages (from-to)8958-8965
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number13
DOIs
StatePublished - Mar 26 1999
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry

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