Methotrexate inhibition of muropeptide transporter SLC46A2 controls psoriatic skin inflammation

Abstract

Cytosolic innate immune sensing is critical for protecting barrier tissues. NOD1 and NOD2 are cytosolic sensors of small peptidoglycan fragments (muropeptides) derived from the bacterial cell wall. These muropeptides enter cells, especially epithelial cells, through unclear mechanisms. We previously implicated SLC46 transporters in muropeptide transport in Drosophila immunity. Here we focus on Slc46a2, which is highly expressed in mammalian epidermal keratinocytes, and show that it is critical for delivery of DAP-muropeptides and activation of NOD1 in keratinocytes, while the related transporter Slc46a3 is critical for responding to MDP, the NOD2 ligand. In a mouse model, Slc46a2 and Nod1 deficiency strongly suppressed psoriatic inflammation, while methotrexate, a commonly used psoriasis therapeutic, inhibited Slc46a2-dependent transport of DAP-muropeptides. Collectively these studies define SLC46A2 as a transporter of NOD1 activating muropeptides, with critical roles in the skin barrier, and identify this transporter as an important target for anti-inflammatory intervention.

Synthesis and validation of click-modified of NOD1/2 agonists

“…Here, we report the chemical synthesis of iE-DAP-Alk and MDP-Alk, for use in clickchemistry reactions. This modification is smaller than those previously reported, and valuable in recent work where we probed the biological role of PGN transporters [30]. The modified iE-DAP and MDP showed similar potency as the native molecules in the NF-κB reporter assays in transfected cell lines, and in cytokine induction in IFNγ-primed bone marrow-derived macrophages (BMDM).…”