TIPE proteins control directional migration of human T cells via GPCR and lipid second messenger signaling

Abstract

Abstract Infiltration of specific tissues by circulating leukocytes is a common pathogenic mechanism of inflammatory diseases. G-protein-coupled receptors (GPCR) are essential for sensing chemokine gradients by leukocytes during immune responses. However, how leukocytes integrate site-specific directional cues such as chemokine gradients and make directional decisions in human immune cells is largely unknown. The TNFa-induced protein 8-Like (TIPE or TNFAIP8) family proteins are newly described pilot proteins that control directional migration (chemotaxis) of leukocytes to targeted tissues in mice. Without TIPE proteins, leukocytes become directionless, but the underlying mechanism remains elusive. Using siRNA and biochemical methods, we demonstrated here that two TIPE family members, TNFAIP8 and TIPE2, synergistically controlled directional migration (chemotaxis) in human CD4 T cells: TNFAIP8, through interacting with the Ga subunit of heterotrimeric G-proteins, and TIPE2, through utilizing lipid second messenger signaling by binding to phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-triphosphate (PIP3). Using site-directed mutagenesis, we identified the region of Ga that interacts with TNFAIP8, and the amino acids of TIPE2 protein crucial for its interaction with PIP2 and PIP3. We also discovered that TIPE protein membrane translocation was dependent on PIP2. Collectively, our work describes a new mechanistic paradigm of human T cells integrating GPCR and phospholipid signaling pathways to control directional migration of human immune cells. Additionally, our findings have implications for therapeutic targeting of TIPE proteins in human inflammatory and autoimmune diseases. NIH 5R01AI136945