Investigating phosphatidylinositol phosphates in antigen presentation (360G-Wellcome-209155_Z_17_Z)

Presentation of exogenously acquired antigens to CD4+ T-cells by macrophages and dendritic cells is critical for generation of a robust adaptive immune response. These exogenous antigens are displayed on major histocompatibility complex class II (MHCII) molecules, providing molecular identification of captured pathogens. Antigens destined for presentation can be captured from the extracellular environment, or generated by degradation of phagocytosed pathogens. Phosphatidylinositol phosphates (PIPs) and their effector proteins are important for coordinating phagosome maturation and are a key virulence target of many intracellular pathogens. Despite their importance, the mechanisms by which PIPs and their effectors recruit the MHCII complex and initiate trafficking of the MHCII-peptide complex to the plasma membrane remain poorly understood. Using live fluorescence microscopy and manipulating dynamics and localisation of PIPs and their effectors, I aim to investigate the mechanisms of MHCII trafficking and how this can be subverted by pathogens. The main questions I will answer in this proposal are: What are the dynamics of MHCII recruitment to the phagosome and does this depend on specific PIPs and their effector proteins? Are PIP-mediated phagolysosomal tubules required for MHCII-peptide complex delivery to the plasma membrane? Is MHCII trafficking manipulated by pathogens to increase pathogen survival?