Fig. 2. PLA2 and PI3K/PTEN regulate chemotaxis in Dictyostelium. In Dictyostelium, chemotaxis is regulated by at least two intertwined and partly redundant pathways involving PI3K and PLA2. Both pathways are regulated by extracellular cAMP. The PI3K pathway is regulated, via PtdIns(4,5)P₂ (PIP2)/PTEN, by PLC. The PLA2 pathway depends on cytosolic Ca²⁺, which is regulated by IP3 (thus partly by PLC), fatty acids and Ca²⁺ uptake. In steep gradients, either pathway is dispensable; in shallow gradients, both pathways are necessary to allow efficient chemotaxis (see text for details). Red arrows indicate enzymatic reactions. PL, phospholipids; Lyso-PL, lyso-phospholipids; Gβ, heterotrimeric G protein; cAR1, cAMP receptor; PIP3, PtdIns(3,4,5)P₃.