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© The Rockefeller University Press, 0021-9525/1998//1317 $5.00
The Journal of Cell Biology, Volume 143, Number 5, , 1998 1317-1328

Article

Removal of the Membrane-anchoring Domain of Epidermal Growth Factor Leads to Intracrine Signaling and Disruption of Mammary Epithelial Cell Organization



H. Steven Wiley*, Margaret F. Woolf*, Lee K. Opresko*, Patrick M. Burke*, Birgit Will*, Jeffrey R. Morgan{ddagger}, and Douglas A. Lauffenburger§

* Division of Cell Biology and Immunology, Department of Pathology, University of Utah Medical School, Salt Lake City, Utah 84132; {ddagger} Surgical Services, Massachusetts General Hospital, Harvard Medical School and the Shriners Burn Unit, Cambridge, Massachusetts 02139; and § Division of Bioengineering & Environmental Health, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

Autocrine EGF-receptor (EGFR) ligands are normally made as membrane-anchored precursors that are proteolytically processed to yield mature, soluble peptides. To explore the function of the membrane-anchoring domain of EGF, we expressed artificial EGF genes either with or without this structure in human mammary epithelial cells (HMEC). These cells require activation of the EGFR for cell proliferation. We found that HMEC expressing high levels of membrane- anchored EGF grew at a maximal rate that was not increased by exogenous EGF, but could be inhibited by anti–EGFR antibodies. In contrast, when cells expressed EGF lacking the membrane-anchoring domain (sEGF), their proliferation rate, growth at clonal densities, and receptor substrate phosphorylation were not affected by anti–EGFR antibodies. The sEGF was found to be colocalized with the EGFR within small cytoplasmic vesicles. It thus appears that removal of the membrane-anchoring domain converts autocrine to intracrine signaling. Significantly, sEGF inhibited the organization of HMEC on Matrigel, suggesting that spatial restriction of EGF access to its receptor is necessary for organization. Our results indicate that an important role of the membrane-anchoring domain of EGFR ligands is to restrict the cellular compartments in which the receptor is activated.

Key Words: epidermal growth factor • autocrine • intracrine • receptors • epithelium

Abbreviations used in this paper: EGFR, EGF receptor; HB-EGF, heparin binding EGF-like growth factor; HMEC, human mammary epithelial cells.

Address all correspondence to H. Steven Wiley, Department of Pathology, University of Utah Medical School, Salt Lake City, UT 84132. Tel.: (801) 581-5967. Fax: (801) 581-4517. E-mail: wiley{at}path.med.utah.edu


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