Apoptosis signal regulated kinase 1 (ASK1) is a widely expressed redox sensitive serine/threonine kinase, composed of the N-terminal TRX binding domain (ASK1-TBD), the central regulatory region containing the TRAF binding domain (ASK1-CRR), and the serine/threonine kinase domain (ASK1-CD), as well as the C-terminal coiled coil (CC) region. ASK1 plays an important role in the cellular response cascade caused by environmental changes, regulating cell apoptosis signal transduction by activating mitochondrial dependent cysteine proteases. It also mediates signal transduction that determines cell fate, such as differentiation and survival. MAP3K5/ASK1 is also necessary for the innate immune response, which is crucial for the host to resist multiple pathogens.