※ STE20 family introduction

    STE20 was first identified as a putative MAP4K in mating pathway in yeast and its homologs in human constitute a large family in STE group. STE20 can further be classified into two subclasses, PAK and GCK. Structure analysis shows that the kinase domains in PAKs are located at C-terminal while GCKs kinase domains are located in N-terminal. Three mammalian STE20-like kinases have been reported to be able to phosphorylate MAP3Ks, including HPK1, GLK and PAK2. HPK1 predominantly mediate the activation of the stress-activated SAPK/JNK pathway. PAK2 is activated via binding of the Rac1 or Cdc42 and subsequently involved in direct phosphorylation of MAP3K Raf-1. Besides as a upstream activator of MAPK pathway, STE20 are often used in signaling events, including cell apoptosis, morphogenesis and cytoskeletal rearrangement such as cell motility and cell shape changes (1).

Reference
1. Dan, I., Watanabe, N.M. and Kusumi, A. (2001) The Ste20 group kinases as regulators of MAP kinase cascades. Trends Cell Biol, 11, 220-230. PMID: 11316611