Pathways of Intracellular Signal Transduction

A: Incorrect. Stimulation of the Wnt pathway occurs by the binding of a secreted protein to a cell surface receptor.

B: Incorrect. The JAK/STAT pathway is stimulated by cytokines rather than by direct cell-cell interactions.

C: Correct! Notch is a transmembrane protein that is stimulated by other transmembrane proteins (such as Delta) on adjacent cells.

D: Incorrect. This is triggered by the binding of Lin-3, an EGF-like protein, to a receptor called Let-23 on the surface of prevulval cells."