Identifying WNK1 as a Negative Regulator of NLRP3 Inflammasome Activation and Pyroptosis
Pyroptosis is a form of inflammatory cell death initiated by complexes called inflammasomes as a protective response to pathogenic infections and cellular damage. During pyroptosis, inflammasomes mediate the production and release of proinflammatory cytokines, signaling for inflammation and innate immune functions. The NLRP3 inflammasome is the most widely studied inflammasome, as it responds to a diverse range of pathogen and damage-associated stimuli. While NLRP3 is essential for innate immunity, aberrant NLRP3 inflammasome activation contributes to chronic inflammation and a wide variety of inflammatory diseases. Understanding the pathways that control NLRP3 inflammasome activation will help develop strategies to treat these inflammatory conditions. The work presented in this thesis identifies WNK1, a serine/threonine kinase with several cellular functions, as a negative regulator of the NLRP3 inflammasome. In vitro, macrophages deficient in WNK1 protein or kinase activity show a significant increase in NLRP3 inflammasome activation and pyroptosis compared to control macrophages. In vivo, mice with conditional knockout of WNK1 in their macrophages show significant increase in inflammatory cytokine production and neutrophil recruitment in response to NLRP3 stimulation compared with control mice. Mechanistically, we demonstrate that WNK1’s canonical signaling pathway through STK39/OXSR1, which is known to control the SLC12 family of cation-chloride cotransporters, tempers NLRP3 inflammasome activation and pyroptosis by balancing intracellular Cl–and K+ concentrations during NLRP3’s activation. When macrophages are deficient in WNK1, we show that excess potassium and chloride are lost as a response to NLRP3 stimuli, thus exacerbating NLRP3’s activation, pyroptosis, and the resulting inflammatory response. Collectively, this work reinforces the importance of ion regulation during NLRP3 inflammasome activation and pyroptosis and shows for the first time that the WNK1 signaling pathway plays a role in suppressing NLRP3 activationthrough ion regulation. This work also suggests that pharmacological inhibition of the WNK1 pathway may have negative clinical implications by promoting excess inflammation. The knowledge gained from this study introduces a novelarea of regulation to the field, allowing the opportunity to investigate the relationship between WNK1 and the NLRP3 inflammasome in human health and disease.
Biochemistry|Cellular biology|Molecular biology
Mayes-Hopfinger, Lindsey Gail, "Identifying WNK1 as a Negative Regulator of NLRP3 Inflammasome Activation and Pyroptosis" (2021). ETD Collection for Thomas Jefferson University. AAI28714111.