The role of apoptosis signal-regulating kinase 1 in cardiomyocyte apoptosis.

Apoptosis signal-regulating kinase 1 (ASK1), a serine/threonine protein kinase, is a reactive oxygen species-sensitive mitogen-activated protein kinase kinase kinase and activates both p38 and c-Jun N-terminal kinase pathways. Two isoforms of thioredoxin (Trx), cytosolic and mitochondrial Trx (Trx1 and Trx2, respectively), have been identified in mammalian cells. Trx1 was initially identified as an ASK1-binding protein. Trx1 and Trx2 bind directly to the N-terminal regulatory domain of ASK1 and inhibit ASK1-dependent apoptosis. Numerous other proteins interact with ASK1 and regulate its activity. In cardiomyocytes, ASK1 is involved not only in cardiac apoptosis, leading to cardiac remodeling, but also in cardiac hypertrophy as well as nonapoptotic cardiomyocyte death.