Non canonical role of GAPDH in neutrophil migration and chronic skin inflammation

Abstract

Neutrophils are the most abundant leukocytes and have an important role in tissue homeostasis and disease. Neutrophil migration and its role during chronic inflammation have been recently the focus of huge interest due to its tremendous therapeutical potential. The zebrafish has become an excellent model for the study of inflammation and neutrophil biology with several zebrafish mutant lines allowing the study of chronic inflammation. Spint1a-deficient zebrafish larvae is a widely used model of chronic skin inflammation characterized by neutrophil infiltration, epithelial disruption and keratinocyte cell death. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional protein widely known for its implication in the glycolytic pathway and other non-canonical function, such as cell death. Here, we report using a combination of pharmacological and genetic strategies that inhibition of nuclear translocation of Gapdh resulted in decreased skin neutrophil infiltration, speed and displacement length, and in reduced number of keratinocyte hyperproliferation and cell death. In addition, neutrophil number correlated with skin inflammation and expression in neutrophils of wild-type Gapdh, but not a nuclear translocation defective mutant, exacerbated skin inflammation. Similarly, inhibition of nuclear translocation of GAPDH reduced the expression of pathology-associated markers in human organotypic 3D skin models of chronic inflammation. Finally, single cell RNA-Seq analysis of Spint1a-deficient larvae revealed that inhibition of nuclear translocation of Gapdh reduced the expression of a set of genes that were induced in neutrophils and keratinocytes of inflamed skin larvae as well as neutrophil-specific il4 and ptpn6. Strikingly, Il4 deficiency alleviated skin inflammation of Spint1a-deficient larvae, suggesting that Il4 production by neutrophils in response to the nuclear translocation of Gapdh contributed to skin inflammation. Overall, our data supports that a non-canonical function of GAPDH is an important mediator of acute and chronic skin inflammation by modulating both keratinocyte biology and neutrophil infiltration to skin lesions. This mechanism provides new insights into the contribution of neutrophils to acute and chronic skin inflammation, and can have a significant translational impact to develop new therapeutic approaches to treat skin inflammatory disorders.