The class II PI3Ks, CIIα, CIIβ and CIIγ, are not bound by regulatory subunits and are thought to mainly phosphorylate PI to generate a product with only one phosphate group: PI3P. The only class III PI3K, also called Vps34 also phosphorylated PI to generate PI3P. The role of PI3P in immune cells is only beginning to be uncovered.
PIP3 acts as a tether for signalling proteins inside the cell which relay information from outside the cells to instruct the cell how to respond. Some proteins that contain a plecstrin homology (PH) domain can bind specifically to PIP3. The most well-characterised of these are Akt (also known as PKB) and Pdk1.