Membrane identity is key to cellular function, with each organelle displaying distinct identity determinants. Among the main factors imposing this are phosphoinositides, a small family of phospholipids that act as signpost of membrane identity. Interconversion of these phosphoinositides occurs via the action of lipid kinases and phosphatases that control a myriad of cellular functions. Using state of the art protein and supported lipid bilayer reconstitution systems, we are able to gain a direct mechanistic understanding of how these membrane identity changes are regulated.

Membrane identity is a key regulator of diverse cellular events, ranging from membrane trafficking to the formation of membrane contact sites and cytokinesis. By using state of the art imaging approaches, we aim to discover the mechanisms behind this regulation. By selectively perturbing and redirecting lipid kinases and phosphatases using optogenetics and other cell biological approaches, we can selectively alter the membrane identity of organelles. In combination with the reconstitution of phosphoinositide conversion cascades, this will form the basis for a better understanding of fundamental aspects in cell biology with profound implications to health and disease.

In the first publication of the lab, we have combined our passion for protein reconstitution and cellular imaging to generate recombinant biosensors for the detection of all eight phosphoinositide species in fixed and permeabilised cells. Importantly, these biosensors allow for the reliable, and multiplex visualisation of these crucial signalling lipids and are also compatible with super-resolution STED microscopy! This will enable our lab to investigate membrane identity at the nanoscale.

These biosensors are easy to produce recombinantly and have been rigorously validated. We show that this approach presents a major advance in the detection of phosphoinositides in multiple ways:

·        Visualisation of all eight phosphoinositide species without the need of overexpression

·        Super-resolution imaging of the nanoscale organisation of PI(3)P on endosomes and PI(4)P the Golgi

·        Multiplex visualisation across scales, from 2D to 3D cell culture and whole Drosophila tissue