QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by DeWitt, A. E. Articles by Lauffenburger, D. A. Search for Related Content PubMed PubMed Citation Articles by DeWitt, A. E. Articles by Lauffenburger, D. A. Social Bookmarking                         What's this?

Quantitative analysis of the EGF receptor autocrine system reveals cryptic regulation of cell response by ligand capture

¹ Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
² Newborn Medicine, Children’s Hospital, Boston, MA 02115, USA
³ Fundamental Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
⁴ Division of Bioengineering and Environmental Health and Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

*Author for correspondence (e-mail: lauffen{at}mit.edu)

Accepted March 29, 2001

Autocrine signaling is important in normal tissue physiology as well as pathological conditions. It is difficult to analyze these systems, however, because they are both self-contained and recursive. To understand how parameters such as ligand production and receptor expression influence autocrine activity, we investigated a human epidermal growth factor/epidermal growth factor receptor (EGF/EGFR) loop engineered into mouse B82 fibroblasts. We varied the level of ligand production using the tet-off expression system and used metalloprotease inhibitors to modulate ligand release. Receptor expression was varied using antagonistic blocking antibodies. We compared autocrine ligand release with receptor activation using a microphysiometer-based assay and analyzed our data using a quantitative model of ligand release and receptor dynamics. We found that the activity of our autocrine system could be described in terms of a simple ratio between the rate of ligand production (V_LT) and the rate of receptor production (V_R). At a V_LT/V_R ratio of <0.3, essentially no ligand was found in the extracellular medium, but a significant number of cell receptors (30-40%) were occupied. As the V_LT/V_R ratio increased from 0.3 towards unity, receptor occupancy increased and significant amounts of ligand appeared in the medium. Above a V_LT/V_R ratio of 1.0, receptor occupancy approached saturation and most of the released ligand was lost into the medium. Analysis of human mammary epithelial cells showed that a V_LT/V_R ratio of <5x10^-4was sufficient to evoke >20% of a maximal proliferative response. This demonstrates that natural autocrine systems can be active even when no ligand appears in the extracellular medium.

Key words: Autocrine, EGF, Computational model

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				T. G. Johns, R. B. Luwor, C. Murone, F. Walker, J. Weinstock, A. A. Vitali, R. M. Perera, A. A. Jungbluth, E. Stockert, L. J. Old, et al. Antitumor efficacy of cytotoxic drugs and the monoclonal antibody 806 is enhanced by the EGF receptor inhibitor AG1478 PNAS, December 23, 2003; 100(26): 15871 - 15876. [Abstract] [Full Text] [PDF]

				W. Tang, I. Ezcurra, J. Muschietti, and S. McCormick A Cysteine-Rich Extracellular Protein, LAT52, Interacts with the Extracellular Domain of the Pollen Receptor Kinase LePRK2 PLANT CELL, September 1, 2002; 14(9): 2277 - 2287. [Abstract] [Full Text] [PDF]