Analysis of Apoptosis Signal-Regulating Kinase I (ASK1) Oligomerization

Abstract

Apoptosis Signal-Regulating Kinase I (ASK1) is a member of the Mitogen Activated Protein Kinase (MAPK) pathway. Responding to various stimulations, ASK1 activates four MAPK kinase (MKK) substrates including MKK4/7 and MKK3/7, which phosphorylate the c – Jun N terminal Kinase (JNK) and p38, respectively. The dysfunction and misregulation of ASK1 lead to various diseases such as cancers, cardiovascular diseases, neurodegenerative disorders, inflammatory diseases and diabetes. The activation of ASK1 is highly regulated by many regulatory factors. However, the molecular mechanism of ASK1 activation largely remains unclear. We recently found out that the purified ASK1 is capable of auto-activating itself and it exists as a huge oligomer instead of a homodimer as previous studies suggested. To explore the mechanism of ASK1 oligomerization and auto-activation, we have generated a series of ASK1 truncates and hoping to identify the responsible domains/motifs for its oligomerization and auto-activation. We have purified two ASK1 truncates - ASK1-NK (N terminal and Kinase domains) and ASK1-K (Kinase domain). After performing gel filtration, it was found out that, ASK1-NK remains as monomer and ASK1-K forms dimer in their native state. In conclusion, this study will help us to understand the detailed mechanism of ASK1 oligomerization which will surely enrich our knowledge in understanding the activation process of ASK1.