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Mitochondria regulate intracellular coenzyme Q transport and ferroptotic resistance via STARD7

ABSTRACT: Coenzyme Q (or ubiquinone) is a redox-active lipid, which serves as universal electron carrier in the mitochondrial respiratory chain and antioxidant in the plasma membrane limiting lipid peroxidation and ferroptosis. Mechanisms allowing cellular coenzyme Q distribution after synthesis within mitochondria are not understood. Here, we identify the cytosolic lipid transfer protein STARD7 as a critical and limiting factor of intracellular coenzyme Q transport. Dual localization of STARD7 to the intermembrane space of mitochondria and the cytosol upon cleavage by the rhomboid protease PARL ensures the synthesis of coenzyme Q in mitochondria and its transport to the plasma membrane. While cytosolic STARD7 overexpression protects against ferroptosis, it limits CoQ abundance in mitochondria and respiratory cell growth, illustrating the need to coordinate CoQ synthesis and cellular distribution by PARL-mediated STARD7 processing. Our findings highlight the antioxidant function of mitochondrial CoQ against ferroptosis and identify PARL and STARD7 as promising targets to interfere with ferroptosis. The repository contains raw files and methods for project 0112 (brain – whole proteomics) and 0176 (spatial proteomics). The labeling of the raw files and the experiment – raw file matches are available in the individual search zip files. The individual sections are accompanied with the project identifier.

INSTRUMENT(S): Orbitrap Exploris 480

ORGANISM(S): Homo Sapiens (human) Mus Musculus (mouse)

TISSUE(S): Brain, Cell Culture

SUBMITTER: Hendrik Nolte

LAB HEAD: Thomas Langer

PROVIDER: PXD033064 | Pride | 2022-11-12

REPOSITORIES: Pride

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			Action	DRS
	0112_SEARCH.zip	Other
	0176_SEARCH.zip	Other
	20200814_DD_0112_SoDe_wholeP_sample01.raw	Raw
	20200814_DD_0112_SoDe_wholeP_sample02.raw	Raw
	20200814_DD_0112_SoDe_wholeP_sample03.raw	Raw

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Project description:MicroRNAs (miRNAs) are small non-coding RNAs that associate with Argonaute 2 protein to regulate gene expression at the post-transcriptional level in the cytoplasm. However, recent studies have reported that some miRNAs localize to and function in other cellular compartments. Mitochondria harbour their own genetic system that may be a potential site for miRNA-mediated post-transcriptional regulation. We aimed at investigating whether nuclear-encoded miRNAs can localize to and function in human mitochondria. To enable identification of mitochondrial-enriched miRNAs, we profiled the mitochondrial and cytosolic RNA fractions from the same HeLa cells by miRNA microarray analysis. Mitochondria were purified using a combination of cell fractionation and immunoisolation, and assessed for the lack of protein and RNA contaminants. We found 57 miRNAs differentially expressed in HeLa mitochondria and cytosol. Of these 57, a signature of 13 nuclear-encoded miRNAs was reproducibly enriched in mitochondrial RNA and validated by RT-PCR for hsa-miR-494, hsa-miR-1275 and hsa-miR-1974. This study provides the first comprehensive view of the localization of RNA interference components to the mitochondria. Our data outline the molecular bases for a novel layer of crosstalk between nucleus and mitochondria through a specific subset of human miRNAs that we termed ‘mitomiRs’. To assess whether nuclear-encoded miRNA are detectable in human mitochondria, we performed the following four steps approach. First, cultured HeLa cells were allowed to reach 80-100% confluence and subjected to fractionation in order to isolate the cytosolic fraction. From the same HeLa cells, mitochondria were isolated by immunomagnetic Anti-TOM22 MicroBeads from the Mitochondria Isolation Kit (Miltenyi Biotec). In total, six mitochondria preparations were perfromed, three of these were additionally treated with RNase A. Second, total RNA was extracted from the mitochondrial and cytosolic fractions. Third, mitochondrial and cytosolic RNA were respectively profiled by microRNA microarray analysis. Last, data were analyzed and normalized.Three independent assays were performed.

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Mitochondria regulate intracellular coenzyme Q transport and ferroptotic resistance via STARD7

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