Novel role for the N-terminus domain of the a2 isoform of vacuolar ATPase in interleukin-1β production

Interleukin-1β (IL-1β) is a mediator cytokine that is released by macrophages and epithelial cells in pregnancy and tumorigenesis before antigen recognition. a2V-ATPase is a protein expressed during pregnancy and tumorigenesis and has a novel role in immune regulation. It is expressed as a 70 kDa molecule in intracellular vesicles. Upon cell stimulation it migrates to the surface followed by the cleavage of a 20 kDa portion (a2 N-terminus domain, a2NTD). This study aimed to determine whether a2NTD could induce IL-1β production in immune cells. Peripheral blood mononuclear cells (PMBC) were stimulated with a2NTD and analyzed for cytokine gene expression by gene arrays. Supernatants were analyzed for IL-1β by enzyme-linked immunosorbent assay, and cells were analyzed for intracellular expression of IL-1α, IL-1β, and TNF-α by flow cytometry. When PBMC were cultured with a2NTD, there was a 2.5-fold increase in IL1A and IL1B gene expression and no induction of TNF gene expression. There was a 72-fold increase in IL-1β in supernatants of PBMC cultured with a2NTD. Finally, there was a 204-fold increase in intracellular expression of IL-1β in monocytes incubated with a2NTD. These results indicate a regulatory role for a2NTD in IL-1 cytokine production and suggest a unique role for this molecule in inflammation.