Abstract
A procedure for an in vitro signaling assay is described for the MAPK and NFkappaB pathways. The method uses a membrane-cleared lysate that contains all the soluble components required for activating these signaling cascades. The pathways can be activated by variety of molecules, including kinases, G-proteins, and E3 ligases. We demonstrate that YopJ inhibits downstream of all these activators. The in vitro signaling assay is ideal for initial biochemical studies on activators and inhibitors of the MAPK and NFkappaB pathways.