TY - JOUR T1 - The ER morphology-regulating lunapark protein induces the formation of stacked bilayer discs JF - Life Science Alliance JO - Life Sci. Alliance DO - 10.26508/lsa.201700014 VL - 1 IS - 1 SP - e201700014 AU - Songyu Wang AU - Robert E Powers AU - Vicki AM Gold AU - Tom A Rapoport Y1 - 2018/01/01 UR - https://www.life-science-alliance.org/content/1/1/e201700014.abstract N2 - Lunapark (Lnp) is a conserved membrane protein that localizes to and stabilizes three-way junctions of the tubular ER network. In higher eukaryotes, phosphorylation of Lnp may contribute to the conversion of the ER from tubules to sheets during mitosis. Here, we report on the reconstitution of purified Lnp with phospholipids. Surprisingly, Lnp induces the formation of stacked membrane discs. Each disc is a bicelle, with Lnp sitting in the bilayer facing both directions. The interaction between bicelles is mediated by the cytosolic domains of Lnp, resulting in a constant distance between the discs. A phosphomimetic Lnp mutant shows reduced bicelle stacking. Based on these results, we propose that Lnp tethers ER membranes in vivo in a cell cycle–dependent manner. Lnp appears to be the first membrane protein that induces the formation of stacked bicelles. ER -