Amino acid transport represents a druggable process for inhibiting human plasmacytoid dendritic cell activity during autoimmunity

IL-3 mediates human plasmacytoid dendritic cell (pDC) survival in vitro, but its mechanism of action is unclear. We show that, through JAK2/STAT5, IL-3 and the related GM-CSF, induce expression of System L amino acid transporters SLC7A5 and SLC3A2. This primes pDC to allow subsequent activation of mTORC1 in response to TLR9 stimulation. Active mTORC1 facilitates increased metabolic activity, type I IFN and TNF production, and the expression of SLC7A11, a subunit of the cystine/glutamate antiporter, xc—. We found that co-expression of SLC7A5, SLC3A2 and SLC7A11 is a major transcriptional signature shared by cytokine-producing pDC in vitro, and pDC at sites of autoimmune kidney damage in systemic lupus erythematosus (SLE). Targeting the expression or function of these transporters with inhibitors of JAK2 and of xc— synergistically blocked cytokine production by pDC. We propose that such an approach may have value for treating SLE, and other diseases in which pDC are implicated. Overall design: PBMC from buffy coats from healthy blood donors were isolated by density gradient centrifugation using SepMate tubes and Lymphoprep (both STEMCELL Technologies). pDC were negatively selected from PBMC using the plasmacytoid dendritic cell isolation kit II (Miltenyi Biotec). pDC were cultured with or without ODN for 5h. Single cells were sequenced using the 10x Chromium controller. One sample per treatment was used.