Prof. Dr. Robert Ernst: "Membranes as responsive interfaces"

Cellular membranes are complex mixtures of proteins and lipids. As a collective, these constituents shape the bulk physicochemical membrane properties such as the viscosity, the lateral pressure profile, and the lipid phase behavior. It turns out that cells have evolved sophisticated mechanisms to sense and control these physicochemical properties both at the surface of the membrane and within the hydrophobic core. In collaboration with experts in molecular dynamics simulations, we study the dynamic interactions of membrane property sensors with the membrane environment. We aim to establish how organelles maintain their identity and function during cellular stress and adaptation. The ultimate goal to understand and control membrane responsiveness.

Jun.-Prof. Dr. Bianca Schrul: "Membrane Protein Targeting and Insertion into Lipid Droplets"

Lipid droplets (LDs) are cytosolic organelles that dynamically store the majority of metabolic energy in the form of neutral lipids. In contrast to all other organelles, LDs are uniquely encapsulated by a phospholipid monolayer, which separates their hydrophobic lipid core from the aqueous cytosol. Integral LD membrane proteins adopt a unique topology, in which a hydrophobic segment is inserted into the phospholipid monolayer in a hairpin-type fashion. Interestingly, many of these hairpin-proteins are initially inserted into the endoplasmic reticulum membrane before they partition to the LD monolayer. Extensive research revealed how transmembrane-spanning proteins are inserted into phospholipid bilayers. However, next to nothing is known about how hairpin proteins integrate into phospholipid monolayers. We aim to combine in vitro reconstitution experiments with molecular dynamics simulations to decipher how hairpin proteins are integrated into different types of membranes and how they partition between them. Together with quantitative imaging techniques to define the spatio-temporal distribution of LD-destined membrane proteins in living cells, this will provide key insights into fundamental processes of LD biogenesis from an integrated biophysical and cell-biological view.

Jun.-Prof. Dr. David Mick: "Time-resolved Proximity Labeling and Proteomics of Primary Cilia During Cellular Signaling"

Primary cilia are several µm long plasma membrane protrusions that coordinate central cellular signaling pathways. By using sophisticated protein trafficking mechanisms cilia dynamically adapt their protein content in response to external signals. Yet, how this constant re-shaping of the cilia proteome impacts the cilia signaling environment is largely unknown. We are combining advanced light microscopy and APEX-based proximity labeling with state-of-the-art mass-spectrometric methods to study the proteomic changes of primary cilia in an unbiased, quantitative and time-resolved manner. Our goal is to determine protein and second messenger concentrations in cilia during signaling to establish how the ciliary compartment processes and integrates external signals to trigger cellular cues. In light of the CRC1027, we can envision several collaborative projects to study polarized protein transport during cilia formation, to model the dynamic equilibrium of the ciliary proteome, and to unravel the impact of dynamic length control of cilia on their signaling capacity.