Characteristic ERK Signaling Dynamics Distinguishes Necroptosis from Apoptosis

Abstract

ERK involvement in cell death remains unclear, although many studies have demonstrated the importance of ERK dynamics in determining cellular responses. To untangle ERK’s contribution in two cell death programs, we investigated ERK signaling dynamics during hFasL-induced apoptosis and TNF-induced necroptosis in L929sAhFas cells. We observed that ERK inhibition sensitizes cells to apoptosis while delaying necroptosis. By monitoring ERK activity by live-cell imaging using an improved ERK biosensor (EKAR4.0), we reported differential ERK signaling dynamics between cell survival, apoptosis, and necroptosis. We also decrypted a temporally shifted amplitude- and frequency-modulated (AM/FM) ERK activity profile in necroptosis versus apoptosis. ERK inhibition disrupted these ERK signaling dynamics and prevented TNF and IL-6 gene expression increase during TNF-induced necroptosis. Using inducible cell line for activated MLKL, the final executioner of necroptosis, we propose ERK and its distinctive necroptotic ERK activity dynamics to be positioned downstream of MLKL.