Spitz is a protein in Drosophila species which is the major activator of their epidermal growth factor receptor (EGFR).
Spitz is responsible for activating signaling of the Drosophila epidermal growth factor receptor (DER) and is involved in the development of the embryos, eyes, and wings of fruit flies.
Spitz can be sequestered and prevented from binding to DER by the protein Argos (Aos) which then inhibits the epidermal growth factor receptor pathway.
[4] EGFR exists as a dimer, and two Spitz proteins bind to the receptor to regulate its function.
The specificity, autophosphorylation, mechanism, and other behaviors of the dimer can change significantly when it is weakened by the double-occupancy of the Spitz proteins.