Atypical PI3Ks coordinate chemotaxis, signaling dynamics, and multicellular development in Dictyostelium

Phosphoinositide 3-kinase (PI3K) signaling regulates protrusion, polarity, membrane uptake, and multicellular development in Dictyostelium discoideum, but these functions have been interpreted largely through canonical Class I PI3Ks and PI(3,4,5)P production. This framework does not fully explain how PI3K-dependent pathways attenuate Ras activity, organize PI(3,4)P2-associated polarity states, support cAMP relay, or coordinate development. Here, we identify three atypical PI3K-family enzymes--PikF, PikG, and PikH--as functionally distinct regulators of these processes. PikF constrains Ras-phosphoinositide-actin signaling; pikF- cells show prolonged cAMP-stimulated Ras activation, extended PI