Focus issue: recruiting players for a game of ERK.

The extracellular signal-regulated kinase (ERK) pathway is one of the superfamily of mitogen-activated protein kinase pathways. Signals transmitted by this kinase cascade activate a pair of related proteins, ERK1 and ERK2. Research published in Science Signaling shows that, despite the wealth of knowledge about this pathway, previously unknown functions continue to be discovered and additional components in this pathway continue to be identified. Thus, we are continuing to learn the plays and recruit the players in the game that is ERK signaling.