Human mitochondrial DNA-protein complexes attach to a cholesterol-rich membrane structure

Gerhold, J. M., Cansiz-Arda, Ş., Lõhmus, M., Engberg, O., Reyes, A., van Rennes, H., Sanz, A., Holt, I. J., Cooper, H. M. and Spelbrink, J. N. (2015) Human mitochondrial DNA-protein complexes attach to a cholesterol-rich membrane structure. Scientific Reports, 5, 15292. (doi:10.1038/srep15292) (PMID:26478270) (PMCID:PMC4609938)

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Abstract

The helicase Twinkle is indispensable for mtDNA replication in nucleoids. Previously, we showed that Twinkle is tightly membrane-associated even in the absence of mtDNA, which suggests that Twinkle is part of a membrane-attached replication platform. Here we show that this platform is a cholesterol-rich membrane structure. We fractionated mitochondrial membrane preparations on flotation gradients and show that membrane-associated nucleoids accumulate at the top of the gradient. This fraction was shown to be highly enriched in cholesterol, a lipid that is otherwise low abundant in mitochondria. In contrast, more common mitochondrial lipids and abundant inner-membrane associated proteins concentrated in the bottom-half of these gradients. Gene silencing of ATAD3, a protein with proposed functions related to nucleoid and mitochondrial cholesterol homeostasis, modified the distribution of cholesterol and nucleoids in the gradient in an identical fashion. Both cholesterol and ATAD3 were previously shown to be enriched in ER-mitochondrial junctions and we detect nucleoid components in biochemical isolates of these structures. Our data suggest an uncommon membrane composition that accommodates platforms for replicating mtDNA and reconcile apparently disparate functions of ATAD3. We suggest that mtDNA replication platforms are organized in connection with ER-mitochondrial junctions, facilitated by a specialized membrane architecture involving mitochondrial cholesterol.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Sanz Montero, Professor Alberto
Authors: Gerhold, J. M., Cansiz-Arda, Ş., Lõhmus, M., Engberg, O., Reyes, A., van Rennes, H., Sanz, A., Holt, I. J., Cooper, H. M., and Spelbrink, J. N.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Scientific Reports
Publisher:Nature Research
ISSN:2045-2322
ISSN (Online):2045-2322
Copyright Holders:Copyright © 2015 The Authors
First Published:First published in Scientific Reports 5:15292
Publisher Policy:Reproduced under a Creative Commons License

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