skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Mitochondrial-ER Contact Sites and Tethers Influence the Biosynthesis and Function of Coenzyme Q
Coenzyme Q (CoQ) is an essential redox-active lipid that plays a major role in the electron transport chain, driving mitochondrial ATP synthesis. In Saccharomyces cerevisiae (yeast), CoQ biosynthesis occurs exclusively in the mitochondrial matrix via a large protein-lipid complex, the CoQ synthome, comprised of CoQ itself, late-stage CoQ-intermediates, and the polypeptides Coq3-Coq9 and Coq11. Coq11 is suggested to act as a negative modulator of CoQ synthome assembly and CoQ synthesis, as its deletion enhances Coq polypeptide content, produces an enlarged CoQ synthome, and restores respiration in mutants lacking the CoQ chaperone polypeptide, Coq10. The CoQ synthome resides in specific niches within the inner mitochondrial membrane, termed CoQ domains, that are often located adjacent to the endoplasmic reticulum-mitochondria encounter structure (ERMES). Loss of ERMES destabilizes the CoQ synthome and renders CoQ biosynthesis less efficient. Here we show that deletion of COQ11 suppresses the respiratory deficient phenotype of select ERMES mutants, results in repair and reorganization of the CoQ synthome, and enhances mitochondrial CoQ domains. Given that ER-mitochondrial contact sites coordinate CoQ biosynthesis, we used a Split-MAM (Mitochondrial Associated Membrane) artificial tether consisting of an ER-mitochondrial contact site reporter, to evaluate the effects of artificial membrane tethers on CoQ biosynthesis in both wild-type and ERMES mutant yeast strains. Overall, this work identifies the deletion of COQ11 as a novel suppressor of phenotypes associated with ERMES deletion mutants and indicates that ER-mitochondria tethers influence CoQ content and turnover, highlighting the role of membrane contact sites in regulating mitochondrial respiratory homeostasis.  more » « less
Award ID(s):
2343997
PAR ID:
10570177
Author(s) / Creator(s):
 ;  ;  ;  ;  
Publisher / Repository:
SAGE Publications
Date Published:
Journal Name:
Contact
Volume:
8
ISSN:
2515-2564
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; (, Journal of Biological Chemistry)
    Carman, George M (Ed.)
    Coenzyme Q (CoQ) is a redox-active lipid molecule that acts as an electron carrier in the mitochondrial electron transport chain. In Saccharomyces cerevisiae, CoQ is synthesized in the mitochondrial matrix by a multi-subunit protein-lipid complex termed the CoQ synthome, the spatial positioning of which is coordinated by the Endoplasmic Reticulum-Mitochondria Encounter Structure (ERMES). The MDM12 gene encoding the cytosolic subunit of ERMES, is co-expressed with COQ-10, which encodes the putative CoQ chaperone Coq10, via a shared bidirectional promoter. Deletion of COQ10 results in respiratory deficiency, impaired CoQ biosynthesis, and reduced spatial coordination between ERMES and the CoQ Synthome. While Coq10 protein content is maintained upon deletion of MDM12, we show that deletion of COQ10 by replacement with a HIS3 marker results in diminished Mdm12 protein content. Since deletion of individual ERMES subunits prevents ERMES formation, we asked whether some or all of the phenotypes associated with COQ10 deletion result from ERMES dysfunction. To identify the phenotypes resulting solely due to the loss of Coq10, we constructed strains expressing a functionally impaired (coq10-L96S) or truncated (coq10-R147*) Coq10 isoform using CRISPR-Cas9. We show that both coq10 mutants preserve Mdm12 protein content and exhibit impaired respiratory capacity like the coq10Δ mutant, indicating that Coq10’s function is vital for respiration regardless of ERMES integrity. Moreover, the maintenance of CoQ synthome stability and efficient CoQ biosynthesis observed for the coq10-R147* mutant suggests these deleterious phenotypes in the coq10Δ mutant result from ERMES disruption. Overall, this study clarifies the role of Coq10 in modulating CoQ biosynthesis. 
    more » « less
  2. ; ; ; ; (, bioRxiv)
    Abstract Mitochondria play a crucial role in the regulation of cellular metabolism and signalling. Mitochondrial activity is modulated by the processes of mitochondrial fission and fusion, which are required to properly balance respiratory and metabolic functions, transfer material between mitochondria, and remove defective mitochondria. Mitochondrial fission occurs at sites of contact between the endoplasmic reticulum (ER) and mitochondria, and is dependent on the formation of actin filaments that drive mitochondrial constriction and the recruitment and activation of the dynamin-related GTPase fission protein DRP1. The requirement for mitochondria- and ER-associated actin filaments in mitochondrial fission remains unclear, and the role of actin in mitochondrial fusion remains entirely unexplored. Here we show that preventing the formation of actin filaments on either mitochondria or the ER disrupts both mitochondrial fission and fusion. We show that fusion but not fission is dependent on Arp2/3, whereas both fission and fusion are dependent on INF2 formin-dependent actin polymerization. We also show that mitochondria-associated actin marks fusion sites prior to the dynamin family GTPase fusion protein MFN2. Together, our work introduces a novel method for perturbing organelle-associated actin filaments, and demonstrates a previously unknown role for actin in mitochondrial fusion. 
    more » « less
  3. ; ; ; ; ; (, Science)
    Lipid composition determines the physical properties of biological membranes and can vary substantially between and within organisms. We describe a specific role for the viscosity of energy-transducing membranes in cellular respiration. Engineering of fatty acid biosynthesis inEscherichia coliallowed us to titrate inner membrane viscosity across a 10-fold range by controlling the abundance of unsaturated or branched lipids. These fluidizing lipids tightly controlled respiratory metabolism, an effect that can be explained with a quantitative model of the electron transport chain (ETC) that features diffusion-coupled reactions between enzymes and electron carriers (quinones). Lipid unsaturation also modulated mitochondrial respiration in engineered budding yeast strains. Thus, diffusion in the ETC may serve as an evolutionary constraint for lipid composition in respiratory membranes. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, Journal of Cell Biology)
    Mitochondria are dynamic organelles regulated by fission and fusion processes. The fusion of membranes requires elaborative coordination of proteins and lipids and is particularly crucial for the function and quality control of mitochondria. Phosphatidic acid (PA) on the mitochondrial outer membrane generated by PLD6 facilitates the fusion of mitochondria. However, how PA promotes mitochondrial fusion remains unclear. Here, we show that a mitochondrial outer membrane protein, NME3, is required for PLD6-induced mitochondrial tethering or clustering. NME3 is enriched at the contact interface of two closely positioned mitochondria depending on PLD6, and NME3 binds directly to PA-exposed lipid packing defects via its N-terminal amphipathic helix. The PA binding function and hexamerization confer NME3 mitochondrial tethering activity. Importantly, nutrient starvation enhances the enrichment efficiency of NME3 at the mitochondrial contact interface, and the tethering ability of NME3 contributes to fusion efficiency. Together, our findings demonstrate NME3 as a tethering protein promoting selective fusion between PLD6-remodeled mitochondria for quality control. 
    more » « less
  5. ; (, ACS Chemical Biology)
    Organelles feature characteristic lipid compositions that lead to differences in membrane properties. In cells, membrane ordering and fluidity are commonly measured using the solvatochromic dye Laurdan, whose fluorescence is sensitive to lipid packing. As a general lipophilic dye, Laurdan stains all hydrophobic environments in cells; therefore, it is challenging to characterize membrane properties in specific organelles or assess their responses to pharmacological treatments in intact cells. Here, we describe the synthesis and application of Laurdan-derived probes that read out the membrane packing of individual cellular organelles. The set of organelle-targeted Laurdans (OTL) localizes to the ER, mitochondria, lysosomes, and Golgi compartments with high specificity while retaining the spectral resolution needed to detect biological changes in membrane ordering. We show that ratiometric imaging with OTLs can resolve membrane heterogeneity within organelles as well as changes in lipid packing resulting from inhibition of trafficking or bioenergetic processes. We apply these probes to characterize organelle-specific responses to saturated lipid stress. While the ER and lysosomal membrane fluidity is sensitive to exogenous saturated fatty acids, that of mitochondrial membranes is protected. We then use differences in ER membrane fluidity to sort populations of cells based on their fatty acid diet, highlighting the ability of organelle-localized solvatochromic probes to distinguish between cells based on their metabolic state. These results expand the repertoire of targeted membrane probes and demonstrate their application in interrogating lipid dysregulation. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email