TABLE 1.

EC₅₀ values for agonist-stimulated EGF receptor/protein association

Table compares the EC₅₀ values for each growth factor for stimulating the recruitment of the eight signaling proteins. These values were estimated based on the response to each dose of growth factor at t = 2.5 min. This largely eliminates the effects of the declines in signal at longer times and means that these values reflect mainly the initial association of the two proteins. The EC₅₀ values differed for the recruitment of different proteins by the same growth factor. So, for example, EGF exhibited an EC₅₀ of ∼0.03 nm for recruiting Grb2 and PI3K-R1 but an EC₅₀ about 10-fold higher for recruiting Cbl. EPG exhibited the widest range of EC₅₀ values (∼18-fold difference), whereas HB-EGF showed the smallest range of EC₅₀ values (∼3-fold).

EC50	EGF	TGF	BTC	HB-EGF	AREG	EPG	EPR
	nm
Cbl	0.31	0.73	0.40	0.85	36.0	33.0	21.0
CrkL	0.14	0.40	0.25	1.5	26.0	19.0	21.0
Gab1	0.08	0.11	0.06	0.47	5.9	4.8	2.7
Grb2	0.03	0.06	0.04	0.64	4.0	1.8	2.7
PI3K-RI	0.03	0.24	0.11	1.2	21.0	22.0	18.0
p52 Shc	0.06	0.12	0.15	0.85	3.7	3.7	2.6
p66 Shc	0.10	0.21	0.05	1.7	13.0	6.1	4.0
Shp2	0.09	0.11	0.09	0.50	13.0	3.3	4.0