Thrombospondin 2 potentiates notch3/jagged1 signaling.

Extracellular thrombospondins (TSP or THBS) and the Notch family of transmembrane receptors share a role in multiple, overlapping cellular functions and participate in developmental signaling and pathological reactions to tissue injury. We demonstrate that TSP2, but not TSP1, enhances the potency of Notch3 signal transduction. In addition, TSP2 reduces cancer cell proliferation in a Notch-ligand dependent fashion. The loss of TSP2 in knock-out mice reduces Notch target gene expression. TSP2 binds directly to Notch3 and Jagged1. TSP1 also binds to Notch3 and Jagged1; however, only TSP2 augments the interaction between Notch3 and Jagged1. These studies demonstrate that the diverse functions of TSP2 may also include a role as an intermediary protein that facilitates transcellular receptor-ligand interactions.