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BP: Fachverband Biologische Physik

BP 2: Membranes and Vesicles I

BP 2.7: Hauptvortrag

Montag, 18. März 2024, 11:15–11:45, H 2032

The fascinating membrane morphology of the endoplasmic reticulum — •Reinhard Lipowsky — Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany

Our body contains an enormous number of biomembranes that enclose our cells and most intracellular organelles. A particularly intriguing example is provided by the membrane of the endoplasmic reticulum (ER), which extends throughout the whole cell as a bicontinuous network of membrane nanotubes connected by three-way junctions, thereby generating a surface with a very high topological genus. [1]

A long-standing puzzle of the ER morphology is the straight appearance of the nanotubes in the light microscope, which form contact angles close to 120 degrees. Another puzzling aspect are the nanoscopic shapes of the tubules and junctions. Furthermore, both the formation and the maintenance of the nanotubular networks require GTP and GTP-hydrolyzing membrane proteins. In fact, the nanotubes are destroyed when the supply of GTP is interrupted.

It has been recently argued [1] that all of these puzzling observations are intimately related to each other and to the dimerization of two membrane proteins anchored in the same membrane. The dimerization process can generate an effective membrane tension that stabilizes the ER geometry and prevents the tube destruction, thereby maintaining the integrity of the ER.

[1] R. Lipowsky, S. Pramanik, A. S. Benk, M. Tarnawski, J. P. Spatz, R. Dimova. Elucidating the Morphology of the Endoplasmic reticulum. ACS Nano 17:11957-11968 (2023) DOI: 10.1021/acsnano.3c01338

Keywords: biosystems; biomembranes; curvature elasticity; membrane tension