Identification of a Novel Regulatory Element Controlling ASK1‐JNK Signaling

Abstract

Jun N‐terminal kinase (JNK) plays a key role in mediating diverse signaling events and controls a number of important cellular processes such as apoptosis, proliferation, metabolism, and DNA repair. Dysregulated activation of JNK signaling has been implicated in numerous disease states, including neurodegenerative diseases, chronic inflammatory disease, ischemia, diabetes, and cancer. Thus, understanding how JNK is regulated may lead to the development of novel therapeutic strategies. Our research focuses on the ASK1 signalosome, an upstream kinase complex that controls JNK activity. Here we report the identification of a novel regulatory element between ASK1 and its associated protein kinase, ASK2. Using protein complex pull‐down assays coupled with mutagenesis, we have conclusively established a ternary protein complex composed of ASK1, ASK2, and 14‐3‐3. The ASK1/ASK2 interaction is essential for 14‐3‐3 association. Through deletion mapping and binding assays, we have identified a critical sequence in ASK2 needed for the ASK1/ASK2 interaction. Expression of this regulatory sequence disrupted the ASK2/ASK1 interaction and inhibited JNK activation in response to stress signals, including hydrogen peroxide. These data established the importance of ASK2 in the ASK1 signalosome for JNK regulation and revealed a regulatory element essential for the control of ASK1‐JNK signaling. The ASK1/ASK2 interface may offer a therapeutic target for manipulating JNK signaling. The identified ASK2 sequence may serve as a basis for the development of novel JNK signaling modulators.The work was supported by NIH P01 CA116676.