Suppression of apoptosis signal-regulating kinase 1 (ASK1) activation through ASK2/14-3-3 interaction

A83

The important function of Apoptosis Signal-Regulating Kinase 1 (ASK1) in stress-induced cell death requires that it is highly regulated. Previous findings have shown that ASK2 is an ASK1 binding partner. Here we describe a novel function of ASK2, mediating the interaction between ASK1 and the cell survival protein 14-3-3. We found that ASK2 interacts with 14-3-3, a process that is both phosphorylation-dependent and mediated through the amphipathic groove of 14-3-3. Phosphorylation at serine 964 of ASK2 is critical for binding to 14-3-3, as an alanine mutation at this site completely abolishes interaction. Interestingly, the ASK2 S964A mutation decreases ASK1 and 14-3-3 interaction. This dissociation is correlated with a decrease in the phosphorylation at ASK1 serine 967, the critical residue required for ASK1 interaction with 14-3-3, and a concomminent increase in c-Jun N-terminal kinase (JNK) activation, a downstream target of activated ASK1. This data allows us to propose a model whereby ASK2 interaction with 14-3-3 is first necessary in order for ASK1 to bind with and be regulated by 14-3-3.