Phosphoinositide 3‐kinase gamma; participates in T cell receptor‐induced T cell activation.

Class I phosphoinositide 3‐kinase (PI3K) is a family of enzymes that generate 3‐phosphorylated poly‐phosphoinositides at the cell membrane following stimulation of protein tyrosine (Tyr) kinase‐associated or G protein‐coupled receptors (GPCR). The class I PI3K are divided into two types, class I A p85/p110 heterodimers, which are activated by Tyr kinases, and the class I B p110γ isoform, which is activated by GPCR. Although the T cell receptor (TCR) is a protein Tyr kinase‐associated receptor, previous studies showed that p110γ deletion affects TCR‐induced T cell stimulation. We examined whether the TCR activates p110γ and the consequences of interfering with p110γ expression or function for T cell activation. We found that after TCR ligation, p110γ interacts with Gα q/11 , lymphocyte‐specific tyrosine kinase, and zeta‐associated protein. TCR stimulation activates p110γ, which affects 3‐phosphorylated poly‐phosphoinositides levels at the immunological synapse. We show that TCR‐stimulated p110γ controls Rac1 activity, F‐actin polarization and the interaction between T cells and antigen‐presenting cells, illustrating a crucial role for p110γ in TCR‐induced T cell activation.