Fig 1.

Human type IA PI 3-kinase pathway components targeted in the RNAi-based screen. During infection with Listeria, host type IA PI 3-kinase is activated downstream of the Met receptor and plays a critical role in bacterial internalization (45, 46, 78). Type IA PI 3-kinase uses PI(4,5)P₂ as a substrate and produces the lipid second-messenger product PI(3,4,5)P₃ (11, 31). PI(3,4)P₂ is another second messenger, which is generated from PI(3,4,5)P₃ by phosphatases (11). The RNAi-based screen performed in this study targeted three categories of host genes encoding proteins that act on the type IA PI 3-kinase signaling pathway. Category I genes encode proteins that interact with the 85-kDa regulatory and/or 110-kDa catalytic subunit of PI 3-kinase. Category II genes code for proteins that bind to the PI 3-kinase lipid products PI(3,4,5)P₃ and/or PI(3,4)P₂. Category III genes encode products that are indirectly controlled by type IA PI 3-kinase.