Dresden 2020 – scientific programme

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BP: Fachverband Biologische Physik

BP 5: Bioimaging and Biospectroscopy I

BP 5.6: Talk

Monday, March 16, 2020, 16:45–17:00, HÜL 386

Self-organization of endoplasmic reticulum exit sites — •Konstantin Speckner, Lorenz Stadler, and Matthias Weiss — Experimentalphysik 1, Universität Bayreuth

The endoplasmic reticulum (ER) is a highly dynamic organelle that pervades the entire cell and hosts a variety of vital processes. For example, the exchange of proteins with the secretory pathway occurs at specialized and long-lived membrane domains, called ER exit sites (ERES). In mammalian cells, ERES form droplet-like protein assemblies that arrange as hundreds of dispersed punctae with a quasi-crystalline ordering. Although ERES were seen to diffuse on short timescales, they appear stationary on longer periods. Notably, their dynamics is different from the cytoskeleton-dependent, shivering motion of ER tubules. To gain insights into the underlying physical mechanisms of ERES self-organization, we have studied the emerging pattern of ERES when perturbing the ER morphology in different ways. As a result, we found a significantly changed spatial arrangement of ERES components when affecting the cytoskeletons integrity or reducing the amount of curvature-inducing membrane proteins. Even more pronounced changes were observed when the ER was transformed into vesicular structures by osmotic swelling. Our findings strongly indicate that the self-organization of ERES on the ER membrane system is caused by a diffusion-driven condensation phenomenon, similar to a liquid-liquid phase separation.