Activation of the WNK1 Pathway in Macrophages and Across Tissues

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Koner, Sakura
WNK1 , Macrophages , Neuropathic pain
Lysine-deficient protein Kinase 1 (or WNK1) belongs to a family of unique kinases which lack the conserved lysine residue in the subdomain II of their structure. There are four known members of the WNK family (WNK1-4) that phosphorylate downstream targets SPAK (STE20 (sterile 20)-related Ser/Thr protein kinases or the SPS1 (sporulation-specific protein 1)-related proline/alanine-rich kinase) and OSR1 (Oxidative stress-responsive kinase 1), which phosphorylate sodium-potassium-chloride cotransporters and potassium-chloride cotransporters. WNK1’s role in the central nervous system was first elucidated when mutations in the gene was found to result in the development of Hereditary Sensory and Autonomic Neuropathy Type 2. Since then, it has been shown that WNK1 is activated and upregulated in various models of neuropathic pain. More recently, an evolving role for WNK1 has been found in the immune system. WNK1 acts as a chloride sensor under homeostatic conditions and is activated in response to low intracellular chloride concentration and prevents NLRP3 activation in macrophages. Our study hypothesized that WNK1 and pathway proteins have differential expression across tissues and WNK1 can be activated by modulating environmental salt concentrations in macrophages. We studied baseline expression of total and phosphorylated WNK1 and pathway proteins across various tissues in male and female C57BL/6J mice. Sex-dependent differences in expression patterns were observed for OSR1 in lungs and spleen while other tissues displayed similar expression. WNK1 and other pathway proteins did not show sex-differences but displayed tissue-specific differences. Experiments using the RAW 264.7 macrophage cell line found that challenge with increasing concentrations of salt solutions (sodium and potassium chloride) resulted in increased WNK1 expression at both mRNA and protein levels. This work suggests that WNK1 and most pathway proteins’ expression varies in an organ-specific manner but remains uniform across sexes except OSR1. It also suggests that WNK1 expression can be regulated by increasing salt concentrations in a macrophage cell line. Given that increased WNK1 and salt concentrations are known to result in pain, our work is indicating that targeting this pathway in peripheral immune cells may provide a potential therapeutic target for alleviating neuropathic pain in people living with spinal cord injury.
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