The effect of cellular parameters on the spatial operation of an autocrine system

Autocrine ligands are critically involved in many physiological and pathological conditions such as response to tissue injury, liver regeneration, rheumatoid arthritis, and cancer. Since the presence or absence of an autocrine system does not seem to dictate a normal or pathological condition, we propose that cell physiology may depend on the quantitative properties of autocrine systems. We are investigating the effect of two parameters on the spatial operation of the EGF/EGFR pair, ligand secretion rate and cell surface receptor number. The spatial operation of an autocrine system is evaluated by the probability that a ligand will be self-captured. Using three different assays, we found that above a critical value of ligand secretion rate, the probability of ligand self-capture decreases with increasing ligand secretion rate. We also find that the probability of ligand self-capture at a given secretion rate decreases with decreasing cell surface receptor number.