Endoplasmatic Reticulum Shaping by Generic Mechanisms and Proteins

S.9.B. Endoplasmatic reticulum shaping by generic mechanisms and protein-induced spontaneous curvature and branching.

This chapter deals with the surprising recent discovery that the endoplasmatic reticulum (ER) can form extended tubular network with tubules penetrating to the tip of the axons. The formation of tubular networks is controlled by the generic mechanisms of maximizing the area to volume ratio of ER membranes in the highly crowded cytoplasmic space. The elastic energy associated with the nanotube formation is minimized by spontaneous curvature inducing proteins that form complexes acting as hydrophobic wedges, such as reticulons discovered by the group of Tom Rapoport. The tubular junctions are stabilized by reticulon forming two forceps twisted by 90°. The extension into the dendrites and axons are mediated by coupling of the tubes to the microtubules which is mediated by REEP. An intriguing function of the tubular ER network is the long range stimulation of the genetic expression by calcium waves activating Ca-mediated transcription factors as suggested by Park [Park 2008]. At the end I present models of tension driven membrane fusion, (i) of bud detachment via tension driven pore formation (instead of pinching and popping).

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Endoplasmatic reticulum shaping by generic mechanisms and proteins

For the glossary please see here: Glossary/Lecture notes on ER shaping

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