ABSTRACT
ZAK (sterile alpha motif and leucine zipper containing kinase AZK), a serine/threonine kinase with multiple biochemical functions, has been associated with various cell processes, including cell proliferation, cell differentiation, and cardiac hypertrophy. In our previous reports, we found that the activation of ZAKα signaling was critical for cardiac hypertrophy. In this study, we show that the expression of ZAKα activated apoptosis through both a FAS-dependent pathway and a mitochondria-dependent pathway by subsequently inducing caspase-3. ZAKß, an isoform of ZAKα, is dramatically expressed during cardiac hypertrophy and apoptosis. The interaction between ZAKα and ZAKß was demonstrated here using immunoprecipitation. The results show that ZAKß has the ability to diminish the expression level of ZAKα. These findings reveal an inherent regulatory role of ZAKß to antagonize ZAKα and to subsequently downregulate the cardiac hypertrophy and apoptosis induced by ZAKα.
