Yeast lunapark regulates the formation of trans-Sey1p complexes for homotypic ER membrane fusion

Eunhong Jang; Miriam Lee; So Young Yoon; Sang Soo Lee; Jongseo Park; Mi Sun Jin; Soo Hyun Eom; Changwook Lee; Youngsoo Jun

doi:10.1016/j.isci.2023.108386

Yeast lunapark regulates the formation of trans-Sey1p complexes for homotypic ER membrane fusion

iScience. 2023 Nov 2;26(12):108386. doi: 10.1016/j.isci.2023.108386. eCollection 2023 Dec 15.

Authors

Eunhong Jang¹, Miriam Lee^{1

2}, So Young Yoon¹, Sang Soo Lee¹, Jongseo Park¹, Mi Sun Jin¹, Soo Hyun Eom¹, Changwook Lee³, Youngsoo Jun^{1

4}

Affiliations

¹ School of Life Sciences, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
² Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA.
³ Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea.
⁴ Cell Logistics Research Center, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.

Abstract

The endoplasmic reticulum (ER) consists of the nuclear envelope and a connected peripheral network of tubules and interspersed sheets. The structure of ER tubules is generated and maintained by various proteins, including reticulons, DP1/Yop1p, atlastins, and lunapark. Reticulons and DP1/Yop1p stabilize the high membrane curvature of ER tubules, and atlastins mediate homotypic membrane fusion between ER tubules; however, the exact role of lunapark remains poorly characterized. Here, using isolated yeast ER microsomes and reconstituted proteoliposomes, we directly examined the function of the yeast lunapark Lnp1p for yeast atlastin Sey1p-mediated ER fusion and found that Lnp1p inhibits Sey1p-driven membrane fusion. Furthermore, by using a newly developed assay for monitoring trans-Sey1p complex assembly, a prerequisite for ER fusion, we found that assembly of trans-Sey1p complexes was increased by the deletion of LNP1 and decreased by the overexpression of Lnp1p, indicating that Lnp1p inhibits Sey1p-mediated fusion by interfering with assembly of trans-Sey1p complexes.

Keywords: Biochemistry; Cell biology; Molecular biology.