curvature of double-membrane organelles generated by changes in membrane size and composition曲率变化产生的双层膜细胞器膜的大小和构成.pdf

Curvature of Double-Membrane Organelles Generated by Changes in Membrane Size and Composition Roland L. Knorr, Rumiana Dimova*, Reinhard Lipowsky Max Planck Institute of Colloids and Interfaces, Science Park Golm, Potsdam, Germany Abstract Transient double-membrane organelles are key players in cellular processes such as autophagy, reproduction, and viral infection. These organelles are formed by the bending and closure of flat, double-membrane sheets. Proteins are believed to be important in these morphological transitions but the underlying mechanism of curvature generation is poorly understood. Here, we describe a novel mechanism for this curvature generation which depends primarily on three membrane properties: the lateral size of the double-membrane sheets, the molecular composition of their highly curved rims, and a possible asymmetry between the two flat faces of the sheets. This mechanism is evolutionary advantageous since it does not require active processes and is readily available even when resources within the cell are restricted as during starvation, which can induce autophagy and sporulation. We identify pathways for protein-assisted regulation of curvature generation, organelle size, direction of bending, and morphology. Our theory also provides a mechanism for the stabilization of large double-membrane sheet-like structures found in the endoplasmic reticulum and in the Golgi cisternae. Citation: Knorr RL, Dimova R, Lipowsky R (2012) Curvature of Double-Membrane Organelles Generated by Changes in Membrane Size and Composition. PLoS ONE 7(3): e32753. doi:10.1371/journal.pone.0032753 Editor: Ludger Johannes, Institut Curie, France Received November 9, 2011; Accepted January 30, 2012; Published March 12, 2012 Copyright: 2012 Knorr et al. This is a