Here we investigate the role of Phosphatidylinositol (4,5) bisphosphate (PIP 2) in the physiological activation of primary murine T cells by antigen presenting cells (APC) by addressing two principal challenges in PIP 2 biology. First, PIP 2 is a regulator of cytoskeletal dynamics and a substrate for second messenger generation. The relative importance of these two processes needs to be determined. Second, PIP 2 is turned over by multiple biosynthetic and metabolizing enzymes. The joint effect of these enzymes on PIP 2 distributions needs to be determined with resolution in time and space. We found that T cells express four isoforms of the principal PIP 2-generating enzyme phosphatidylinositol 4-phosphate 5-kinase (PIP5K) with distinct spatial and temporal characteristics. In the context of a larger systems analysis of T cell signaling, these data identify the T cell/APC interface and the T cell distal pole as sites of differential PIP 2 turnover. Overexpression of different PIP5K isoforms, as corroborated by knock down and PIP 2 blockade, yielded an increase in PIP 2 levels combined with isoform-specific changes in the spatiotemporal distributions of accessible PIP 2. It rigidified the T cell, likely by impairing the inactivation of Ezrin Moesin Radixin, delayed and diminished the clustering of the T cell receptor at the cellular interface, reduced the efficiency of T cell proximal signaling and IL-2 secretion. These effects were consistently more severe for distal PIP5K isoforms. Thus spatially constrained cytoskeletal roles of PIP 2 in the control of T cell rigidity and spatiotemporal organization dominate the effects of PIP 2 on T cell activation.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Agricultural and Biological Sciences(all)