Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 3: Membranes and Interfaces

BP 3.12: Talk

Monday, March 26, 2007, 17:00–17:15, H43

Self-organization of exit sites in the endoplasmic reticulum in mammalian cells — •Matthias Weiss and Stephan Heinzer — Cellular Biophysics Group (B085), German Cancer Research Center, Im Neuenheimer Feld 580, 69120 Heidelberg

Exit sites (ES) are specialized membrane domains of the endoplasmic reticulum (ER) at which cargo proteins of the secretory pathway are packaged into small, COPII-coated vesicles. While the essential COPII proteins that are responsible for the emergence of the vesicles have been identified and characterized during the last decade, their binding kinetics and diffusion properties have remained elusive. Using high-resolution fluorescence microscopy techniques (photobleaching and correlation spectroscopy), we have dtermined the typical exchange time of COPII proteins at single ERES in vivo, the diffusion coefficients of the individual proteins in the cytoplasm as well as the cargo-dependent diffusion of ERES on the ER membrane. We also have quantified the spatial arrangement and size distribution of ERES in vivo. Based on these results, we propose a simple model for the self-organization of ERES that quantitatively matches the experimental data.