Dataset Information

A Proximity Labeling Strategy Provides Insights into the Composition and Dynamics of mitochondria-lipid droplet contact proteomes

ABSTRACT: Accumulating studies have shown that mitochondria-lipid droplet (LD) interaction is crucial for maintaining the homeostasis of lipid metabolism in the liver. However, the proteins involved in mitochondria-LD interaction and the functioning mechanism remain largely elusive. Here, we applied a systematic approach to characterize the proteome of mitochondria-LD contacts under normal or starvation condition by combining the bimolecular fluorescence complementary assay and a proximity labeling strategy. We first established a reporter of mitochondria-LD contacts in HepG2 cells and demonstrated that mitochondria-LD contacts are pretty sensitive to nutritional stresses. Furthermore, we uncovered 60 proteins are up-or down-regulated at contact sites upon starvation. Finally, we validated that SQLE translocates from endoplasmic reticulum to LDs and accumulates at mitochondria-LD contact sites upon starvation so as to utilize local ATP for cholesterol synthesis. This work also provides a versatile tool to profile the proteomes of any other inter-organelle membrane contacts in living cells.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Maoge Zhou

LAB HEAD: Tao Xu

PROVIDER: PXD035813 | Pride | 2023-10-24

REPOSITORIES: Pride

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A proximity labeling strategy enables proteomic analysis of inter-organelle membrane contacts.

Zhou Maoge M Kong Bingjie B Zhang Xiang X Xiao Ke K Lu Jing J Li Weixing W Li Min M Li Zonghong Z Ji Wei W Hou Junjie J Xu Tao T

iScience 20230617 7

Inter-organelle membrane contacts are highly dynamic and act as central hubs for many biological processes, but the protein compositions remain largely unknown due to the lack of efficient tools. Here, we developed BiFCPL to analyze the contact proteome in living cells by a bimolecular fluorescence complementation (BiFC)-based proximity labeling (PL) strategy. BiFCPL was applied to study mitochondria-endoplasmic reticulum contacts (MERCs) and mitochondria-lipid droplet (LD) contacts. We identifi ...[more]

PMID: 37485370

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Project description:SEPN1 is a type II protein of the endoplasmic reticulum (ER) whose loss of function gives rise to a collection of debilitating autosomal recessive myopathies gathered under the umbrella term of SEPN1-related myopathy (RM). At the moment, SEPN1-RM lacks an effective pharmacological treatment; thus, the medical management of the disease is only supportive. The potentially fatal diaphragmatic weakness leading to respiratory insufficiency in patients still ambulant is the main reason for medical concerns. Thus, studies on SEPN1-RM pathogenesis are necessary to implement a targeted pharmacological therapy aimed at relieving the general muscle weakness and the more worrisome diaphragmatic dysfunction. Here, we show a physical and functional interaction between SEPN1 and the ER stress mediator ERO1 alpha (henceforth, ERO1). Both SEPN1 and ERO1 are involved in the redox regulation of proteins into the ER, although in an opposite way SEPN1 imposes a less oxidant ER poise while ERO1 a more oxidant one, conceivable with a reductase function of SEPN1 and an oxidase one of ERO1. Furthermore, both are mainly localized in a region of the ER in close contact with mitochondria termed mitochondria-associated membranes (MAMs) and their loss impacts oppositely on the short-range MAMs, thereby impinging ER-mitochondria Ca2+ dynamics, OXPHOS, and bioenergetics. We find that ERO1 depletion restores the impaired short-range MAMs due to SEPN1 loss together with mitochondrial ATP. ERO1 knockout in a mouse background of SEPN1 loss blunts ER stress and the consequent Unfolded Protein Response (UPR) while it rescues the diaphragmatic weakness by improving ER/mitochondria contacts, calcium dynamics, and OXPHOS. Importantly, treatments of SEPN1 knock out mice with the chemical chaperone tauroursodeoxycholic acid (TUDCA) mimic the results of ERO1 loss improving calcium dynamics, OXPHOS, ER/mitochondria contacts, thereby rescuing diaphragmatic weakness as well. In addition, TUDCA-treated SEPN1-RM patients-derived myoblasts show a dynamic dose-dependent increase in ATP levels under ER stress conditions suggesting improved mitochondrial function. Thus, our findings point to the ERO1 axis in the pathogenesis of SEPN1-RM thereby impinging on MAMs and mitochondria bioenergetics and recall for the efficacy of a pharmacology therapy with ad hoc ER stress/ERO1 inhibitors for SEPN1-RM.

			Action	DRS
	1HEPG2-control.raw	Raw
	1MLDCS-HBSS_OA.raw	Raw
	1MLDCS-OA.raw	Raw
	1MLDCS-blank.raw	Raw
	2HEPG2-control.raw	Raw