Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. The endoplasmic reticulum ER is an organelle of nucleated cells that produces proteins, lipids and oligosaccharides. ER volume and activity are increased upon induction of unfolded protein responses UPR and are reduced upon activation of ER-phagy programs.
The first indication of a membrane system surrounding the nucleus was published in by Robert Brown 1. The high resolution offered by electron microscopy subsequently revealed that this membrane system, the nuclear envelope NE , consists of two lipid bilayers, the outer nuclear membrane ONM and the inner nuclear membrane INM , which are a continuation of the ER membrane and delimit the perinuclear space PNS , which is contiguous to the ER lumen Fig.
NPC is a nuclear pore complex. The lower panel represents the isosurface representation of the corresponding segmented volumes for NE at steady state. Please also refer to Movie 1. The dotted line shows the average width of the PNS. Assessment of mechanisms that regulate NE dynamics is relevant because cumulating data reveal that the NE, a subcellular structure that distinguishes eukaryotic from prokaryotic cells, is not a simple barrier that confines nucleoplasmic activities such as gene regulation and transcription from cytoplasmic activities such as gene translation into polypeptide chains.
Rather, the NE is a very dynamic structure 7 , 8 , which is deconstructed and then re-assembled from ER membranes during open mitosis in metazoan 9 , controls access of macromolecules to the nucleoplasm via nuclear pore complexes 10 , forms double-membrane projections in the cytoplasm as observed in several tumors and laminopathies, or invaginations 11 , 12 , it is remodeled to respond to mechanical forces These complexes connect the nucleoskeleton with the cytoskeleton, control nuclear positioning and sense mechanical forces 14 , 16 , 17 , 18 , Cells can adapt the size of the ER to their needs.
These trigger anabolic unfolded protein responses UPR resulting in transcriptional and translational induction of a subset of genes eventually leading to the expansion of the ER volume and activity Thus, the ER is a plastic organelle, whose size and activity are modulated by anabolic and catabolic programs How and if the enlargement or the collapse of the ER volume is transmitted to the NE is poorly understood.
