AUTHOR=Gamper Christopher J., Powell Jonathan D. TITLE=All PI3Kinase signaling is not mTOR: dissecting mTOR-dependent and independent signaling pathways in T cells JOURNAL=Frontiers in Immunology VOLUME=3 YEAR=2012 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2012.00312 DOI=10.3389/fimmu.2012.00312 ISSN=1664-3224 ABSTRACT=

The mechanistic target of rapamycin (mTOR) is emerging as playing a central role in regulating T cell activation, differentiation, and function. mTOR integrates diverse signals from the immune microenvironment to shape the outcome of T cell receptor (TCR) antigen recognition. Phosphatidylinositol 3-kinase (PI3K) enzymes are critical mediators of T cell activation through their generation of the second messenger phosphatidylinositol (3,4,5) triphosphate (PIP3). Indeed, PIP3 generation results in the activation of Protein Kinase B (PKB, also known as AKT), a key activator of mTOR. However, recent genetic studies have demonstrated inconsistencies between PI3K disruption and loss of mTOR expression with regard to the regulation of effector and regulatory T cell homeostasis and function. In this review, we focus on how PI3K activation directs mature CD4 T cell activation and effector function by pathways dependent on and independent of mTOR signaling. Importantly, what has become clear is that targeting both mTOR-dependent and mTOR-independent PI3K-induced signaling distally affords the opportunity for more selective regulation of T cell differentiation and function.