Real-time kinetics: Additional insights for improved RTK drug discovery

Real-time kinetics case study: EGF vs Epiregulin

Kinetics of SH2(Grb2) recruitment to the plasma membrane differ in response to EGF and epiregulin stimulation. Indeed, epiregulin-induced SH2(Grb2) recruitment was more efficacious (~25%) and displayed faster kinetics relative
to that observed with EGF (t1/2 = 31.3 sec vs. 253.8 sec, respectively). The plasma membrane recruitment of SH2(Grb2) in response to both agonists was sustained for at least 60 minutes and was rapidly reversed (within 7 mins) by the EGFR kinase inhibitor Gefitinib (Iressa®). Striking differences were observed in agonist-induced trafficking of the SH2(Grb2) biosensor to early endosomes. Notably, EGF, but not epiregulin, promoted a gradual time-dependent increase in SH2(Grb2) levels in the early endosome compartment. These results are consistent with previously published data demonstrating that EGF, but not epiregulin, promotes EGFR internalization.