Our laboratory studies various signal transduction pathways involved in the regulation of cell proliferation and differentiation. Specifically, we focus on ERK-MAPK pathway mediating growth factor-dependent cell growth regulation, TOR/S6K and LKB1/AMPK pathways mediating nutrient-dependent cell growth regulation, and JNK-MAPK pathway regulating cell death. To understand detailed functional mechanisms of cell growth regulation, we have generated various gain-of-function and loss-of-function mutants for the components of each signaling in Drosophila and characterized their roles in cell growth regulation. By examining their genetic interactions with each other, we are trying to expand our understanding for the global signaling network regulating cell growth. Moreover, through biochemical approaches using mammalian cell culture system, we study the detailed molecular mechanisms on how these molecules function and interact with each other in the process of cell growth regulation.