Fig. 2.

Schematic illustration of Notch signaling circuit. NICD (I) is released when the receptor (N) of the receiver cell interacts with the ligand of the sender cell (D or J) or with external ligands in a soluble form ($D_{ext}$ or $J_{ext}$)––so-called trans-activation. The released signal activates the expression of N and J, and inhibits the expression of D. The cis-inhibition occurs between the receptor and ligand in the same cell and leads to the degradation of both proteins.