Raf kinase inhibitor protein RKIP enhances signaling by glycogen synthase kinase-3β.

Raf kinase inhibitory protein (RKIP) is a physiologic inhibitor of c-RAF kinase and nuclear factor κB signaling that represses tumor invasion and metastasis. Glycogen synthase kinase-3β (GSK3β) suppresses tumor progression by downregulating multiple oncogenic pathways including Wnt signaling and cyclin D1 activation. Here, we show that RKIP binds GSK3 proteins and maintains GSK3β protein levels and its active form.