Enables mitogen-activated protein kinase kinase binding activity. Involved in several processes, including anterograde axonal protein transport; axon regeneration; and positive regulation of JNK cascade. Located in several cellular components, including cell body; dendrite; and perinuclear region of cytoplasm. Orthologous to human MAPK8IP3 (mitogen-activated protein kinase 8 interacting protein 3). [provided by Alliance of Genome Resources, Apr 2022]