The pseudokinase MLKL activates PAD4-dependent NET formation in necroptotic neutrophils

Citation:

Akshay A D'Cruz, Mary Speir, Meghan Bliss-Moreau, Sylvia Dietrich, Shu Wang, Alyce A Chen, Mathilde Gavillet, Arshed Al-Obeidi, Kate E Lawlor, James E Vince, Michelle A Kelliher, Razq Hakem, Manolis Pasparakis, David A Williams, Maria Ericsson, and Ben A Croker. 2018. “The pseudokinase MLKL activates PAD4-dependent NET formation in necroptotic neutrophils.” Sci Signal, 11, 546.

Abstract:

Neutrophil extracellular trap (NET) formation can generate short-term, functional anucleate cytoplasts and trigger loss of cell viability. We demonstrated that the necroptotic cell death effector mixed lineage kinase domain-like (MLKL) translocated from the cytoplasm to the plasma membrane and stimulated downstream NADPH oxidase-independent ROS production, loss of cytoplasmic granules, breakdown of the nuclear membrane, chromatin decondensation, histone hypercitrullination, and extrusion of bacteriostatic NETs. This process was coordinated by receptor-interacting protein kinase-1 (RIPK1), which activated the caspase-8-dependent apoptotic or RIPK3/MLKL-dependent necroptotic death of mouse and human neutrophils. Genetic deficiency of RIPK3 and MLKL prevented NET formation but did not prevent cell death, which was because of residual caspase-8-dependent activity. Peptidylarginine deiminase 4 (PAD4) was activated downstream of RIPK1/RIPK3/MLKL and was required for maximal histone hypercitrullination and NET extrusion. This work defines a distinct signaling network that activates PAD4-dependent NET release for the control of methicillin-resistant (MRSA) infection.