Inflammasomes are multiprotein signaling complexes, which are nucleated by activated cytosolic sensors and regulate inflammation. NLRP1 is the only inflammasome sensor expressed in keratinocytes of the human skin. It is activated by diverse stress signals, which nucleate inflammasomes through its C-terminal UPA-CARD fragment, resulting in caspase-1 activation as well as maturation and release of pro-inflammatory cytokines.
We previously discovered that the ribotoxic stress response as well as by alphavirus infection activate MAP kinase p38, which directly phosphorylates and thus activates NLRP1. Now, we aim to dissect the physiological consequences of NLRP1 activation by arthropod-borne RNA viruses in the skin. To unravel how inflammation is coordinated in realistic models of the skin, we have established the cultivation and infection of human skin explants and primary keratinocytes. To visualize NLRP1 inflammasome assembly in the tissue, we generated recombinant Semliki Forest virus and Sindbis virus strains encoding a customized inflammasome reporter, caspase-1CARD (C1C) fused to fluorescent proteins or Halo-tags under a second subgenomic promoter. Notably, we observed that infection of epidermal sheets as well as ex vivo explants with Semliki Forest virus initiates inflammasome assembly in the tissue. Using this system, we now aim to investigate the molecular details of virus-induced inflammasome assembly in single primary cells as well as the coordination of the ensuing inflammation between different cell types.