This project will combine approaches of biochemical engineering, cell biology, and molecular biology to increase quantitative understanding of how binding and trafficking aspects of growth factor/receptor interactions influence mammalian cell proliferation, and to exploit this increased understanding to suggest design principles for paracrine and autocrine cell culture systems. Epidermal Growth Factor (EGF) and its receptor (EGFR) on fibroblastic cell lines will serve as the system of focus. Mathematical models which describe EGF/EGFR trafficking and its effect on cell growth regulation by exogenous EGF in terms of mechanistic ligand/receptor parameters have been recently developed and experimentally validated. These models will now be used to investigate strategies for perturbation of cell culture systems, and will be extended to paracrine and autocrine EGF sources. The extended models will be critically tested by constructing artificial paracrine and autocrine systems using cells transfected with genes encoding EGF and/or EGFR. Modification of these genes by site-directed mutagenesis will allow key rate parameters of the system to be directly varied. These studies will identify parameters that can be usefully manipulated to regulate cell growth for biotechnological purposes.
