Two receptor classes for epidermal growth factor on pheochromocytoma cells, distinguishable by temperature, lectins, and tumor promoters
✍ Scribed by Johannes Boonstra; Christine L. Mummery; Paul T. van der Saag; Siegrfried W. de Laat
- Publisher
- John Wiley and Sons
- Year
- 1985
- Tongue
- English
- Weight
- 734 KB
- Volume
- 123
- Category
- Article
- ISSN
- 0021-9541
No coin nor oath required. For personal study only.
✦ Synopsis
Rat pheochromocytoma cells (clone PC12) display cell surface receptors for both nerve growth factor (NGF) and epidermal growth factor (EGF) and therefore provide a useful model system with which to study the role of these receptors in the regulation of proliferation and differentiation. In this paper PC12 cells are demonstrated to possess two classes of EGF receptors, a highaffinity class with 7,600 sites per cell and an apparent dissociation constant (Kd) of 0.05 nM, and a low-affinity class with 62,000 sites per cell and a Kd of 14.1 nM. These findings are contrary to literature data (Huff et al., 1981;Vale and Shooter, 1983) but can be explained in part by differences in experimental conditions. Binding studies at 37OC compared with room temperature demonstrated similar affinities of both classes, but during prolonged incubation at 37OC, the binding capacities of both classes decreased. Furthermore t h e high-affinity class was sensitive to lectins, such as concanavalin A (Con A), and to the tumor-promoting phorbol ester 12-0-tetradecanoylphorbol-13-ace- tate (TPA). Both compounds caused a decrease of the affinity of the highaffinity class without affecting the low-affinity class. At high concentrations of Con A or TPA, a decrease of the apparent number of binding sites of the lowaffinity class was also observed. The similarities between the characteristics of EGF binding and NGF binding in PC12 cells are striking and will be discussed.