PT  - JOURNAL ARTICLE
AU  - Songyu Wang
AU  - Robert E Powers
AU  - Vicki AM Gold
AU  - Tom A Rapoport
TI  - The ER morphology-regulating lunapark protein induces the formation of stacked bilayer discs
AID  - 10.26508/lsa.201700014
DP  - 2018 Jan 01
TA  - Life Science Alliance
PG  - e201700014
VI  - 1
IP  - 1
4099  - https://www.life-science-alliance.org/content/1/1/e201700014.short
4100  - https://www.life-science-alliance.org/content/1/1/e201700014.full
SO  - Life Sci. Alliance2018 Jan 01; 1
AB  - 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.