"PI 3-kinases (PI3Ks) generate intracellular lipid second messengers in signal transduction and membrane trafficking pathways. PI3Ks are implicated in cancer, inflammation and autoimmunity, and represent attractive drug targets. Mammalian PI3K isoforms are divided into class I, II and III PI3Ks. While the class I PI3Ks have been extensively studied and targeted in drug development, the other PI3Ks, especially the class II PI3Ks, remain poorly investigated.In this proposal, I aim to uncover the signalling mechanisms and functions of the class II PI3K isoforms, PI3K-C2alpha and PI3K-C2beta, by exploiting cells derived from unique gene-targeted mice generated in the Host Laboratory (unpublished) combined with my expertise in intracellular trafficking and imaging studies. Initial characterisation of these mice indicates that these PI3Ks could be drug targets in their own right in cancer and metabolism, observations that this project now seeks to understand at a molecular and cell level.By screening responses in cells in which class II PI3K isoforms are genetically inactivated in a ‘drug-like’ fashion, I will assess the coupling of these PI3Ks to distinct receptors and their functional impact, interrogate their downstream signalling pathways by phosphoproteomics and lipidomics, and perform a detailed assessment of their spatio-temporal activity upon activation of cell-surface receptors, in order to elucidate their sites of action and the precise subcellular events they regulate. Class II PI3K effector/complexes will be identified. It is poised to unravel new molecular mechanisms interlinking signalling and trafficking.I will bring expertise currently not available in the Host Laboratory and deliver a cross-disciplinary approach to uncover the mechanisms of action and functional roles of potential drug targets, to strengthen the Host, and to provide guidance for ongoing and future drug development and open up new avenues for exploitation."