β-Arrestins facilitate ubiquitin-dependent degradation of apoptosis signal-regulating kinase 1 (ASK1) and attenuate H 2O 2-induced apoptosis

Abstract

β-Arrestins are ubiquitously expressed proteins that play important roles in receptor desensitization, endocytosis, proteosomal degradation, apoptosis and signaling. It has been reported that β-Arrestin2 acts as a scaffold by directly interacting with the JNK3 isoform and recruiting MKK4 and the apoptosis-signaling kinase-1 (ASK1). Here, we report a novel function of β-Arrestins in regulating H 2O 2-induced apoptosis. Our study demonstrates that β-Arrestins physically associate with C-terminal domain of ASK1, and moreover, both over-expression and RNA interference (RNAi) experiments indicate that β-Arrestins down-regulate ASK1 protein. In detail, β-Arrestin-induced reduction of ASK1 protein is due to ubiquitination and proteasome-dependent degradation of ASK1 in response to association of β-Arrestins and ASK1. Upon H 2O 2 stimulation, the protein binding between β-Arrestins and ASK1 increases and ASK1 degradation is expedited. In consequence, β-Arrestins prevent ASK1-JNK signaling and as a result attenuate H 2O 2-induced apoptosis. Structurally, C-terminal domain of ASK1 is essential for β-Arrestins and ASK1 association. We also found that CHIP is required for β-Arrestins-induced ASK1 degradation, which suggested that β-Arrestins function as a scaffold of ASK1 and CHIP, leading to CHIP-mediated ASK1 degradation. All these findings indicate that β-Arrestins play a negative regulatory role in H 2O 2-induced apoptosis signaling through associating with ASK1 and CHIP and facilitating ASK1 degradation, which provides a new insight for analyzing the effects of β-Arrestins on protecting cells from oxidative stress-induced apoptosis.