Question

If you put released NICD in a cell but did not undergo Notch signaling pathway, would NICD still act to turn on Notch target genes or would it not do anything?

Answer 1

Notch receptor is used for direct cell-cell communication between neighbouring cells with the use of transmembrane protein called Delta which acts as a ligand for the Notch receptor. Upon binding by Delta protein to the receptor, Notch Intracellular Domain (NICD) is cleaved by an enzyme called γ-secretase in the cytosol. The released NICD then translocate into nucleus where they binds to transcription factors of the Notch target genes to induce gene expression.

Therefore, the purpose of ligand binding to Notch receptor is to cleave NICD from the receptor which acts as a intracellular signal transporter when set free. As NICD is directly released into the cell here, it still act to perform its role as a intracellular signal transporter as in Notch signalling pathway and turn on Notch target genes