Interaction of the Eph family of
receptor protein tyrosine kinases and their
ligands,
ephrin family members, induces bi-directional signaling via cell-cell contacts. High expression of B-type
ephrin is associated with high invasion potential of
tumors, however, the mechanism by which
ephrin-B promotes
cancer cell invasion is poorly understood. We show that interaction of
ephrin-B1 with the
Eph receptor B2 (EphB2) significantly enhances processing of the extracellular domain of
ephrin-B1, which is regulated by the C-terminus.
Matrix metalloproteinase-8 (MMP-8) is the key
protease that cleaves
ephrin-B1, and the C-terminus of
ephrin-B1 regulates activation of the extracellular release of MMP-8 without requirement of de novo
protein synthesis. One possible mechanism by which
ephrin-B1 regulates the exocytosis of MMP-8 is the activation of Arf1
GTPase, a critical regulator of membrane trafficking. In support of this hypothesis, activation of
ephrin-B1 increased
GTP-bound Arf1, and the secretion of MMP-8 was reduced by expression of a dominant-negative mutant of Arf1. Expression of
ephrin-B1 promoted the invasion of
cancer cells in vivo, which required the C-terminus of
ephrin-B1. Our results suggest a novel function of the C-terminus of
ephrin-B1 in activating MMP-8 secretion, which promotes the invasion of
cancer cells.