Diverse biological and developmental functions are mediated by signall
ing through the epidermal growth factor (EGF) receptor. lit flies, man
y different mechanisms are used to control and restrict EGF-R signalli
ng, including ligand processing, ligand variety (an inhibitor as well
as activators), transcription and perhaps subcellular localization of
the receptor. Since the components of EGF-R signalling have been well
conserved, understanding these different modes of receptor regulation
in flies should lead to general insights into the strategies of recept
or activation.