The JNK-interacting protein (JIP) group of scaffold proteins selectively mediates JNK signaling by aggregating specific components of the MAPK cascade to form a functional JNK signaling module and is required for JNK activation in response to excitotoxic stress. Cytoplasmic JIP1 causes inhibition of JNK-regulated activity by retaining JNK in the cytoplasm and inhibiting JNK phosphorylation of c-Jun. It may also participate in ApoER2-specific reelin signaling and directly, or indirectly, regulates GLUT2 gene expression and beta-cell function. It appears to have a role in cell signaling in mature and developing nerve terminals and may function as a regulator of vesicle transport, through interactions with the JNK-signaling components and motor proteins. It functions as an anti-apoptotic protein whose level seems to influence the beta-cell death or survival response.