GO:0070375:   ERK5 cascade
An intracellular protein kinase cascade containing at least ERK5 (also called BMK1; a MAPK), a MEK (a MAPKK) and a MAP3K. The cascade can also contain an additional tier: the upstream MAP4K. The kinases in each tier phosphorylate and activate the kinases in the downstream tier to transmit a signal within a cell.