Endoplasmic reticulum disruption stimulates nuclear membrane mechanotransduction

Abstract Cytosolic phospholipase A2 (cPLA 2 ) controls some of the most powerful inflammatory lipids in vertebrates by releasing their metabolic precursor, arachidonic acid, from the inner nuclear membrane (INM). Ca 2+ and INM tension (T INM ) are thought to govern the interactions and activity of cPLA 2 at the INM. However, as compensatory membrane flow from the contiguous endoplasmic reticulum (ER) may prevent T INM , the conditions permitting nuclear membrane mechanotransduction by cPLA 2 or other mediators remain unclear. To test whether the ER buffers T INM , we created the genetically encoded, Ca²⁺-insensitive T INM biosensor amphipathic lipid-packing domain inside the nucleus (ALPIN). Confocal time-lapse imaging of ALPIN– or cPLA 2 –INM interactions, along with ER morphology, nuclear shape/volume and cell lysis revealed a link between T INM and disrupted ER–nuclear membrane contiguity in osmotically or ferroptotically stressed mammalian cells and at zebrafish wound margins in vivo. By combining ALPIN imaging with Ca 2+ -induced ER disruption, we reveal the causality of this correlation, which suggests that compensatory membrane flow from the ER buffers T INM without preventing it. Besides consolidating the biomechanical basis of cPLA 2 activation by nuclear deformation, our results identify cell stress- and cell death-induced ER disruption as an additional nuclear membrane mechanotransduction trigger.