Related Experiment Video
Updated: Jul 11, 2025
Author Spotlight: Regulation and Dysregulation of ER-Mitochondria Contacts — Implications for Neurodegenerative Disease Pathogenesis
Published on: October 11, 2024
Membrane contact site detection (MCS-DETECT) reveals dual control of rough mitochondria-ER contacts
Ben Cardoen1, Kurt R Vandevoorde2, Guang Gao2
1School of Computing Science, Simon Fraser University , Burnaby, Canada.
Abstract:
Identification and morphological analysis of mitochondria-ER contacts (MERCs) by fluorescent microscopy is limited by subpixel resolution interorganelle distances. Here, the membrane contact site (MCS) detection algorithm, MCS-DETECT, reconstructs subpixel resolution MERCs from 3D super-resolution image volumes. MCS-DETECT shows that elongated ribosome-studded riboMERCs, present in HT-1080 but not COS-7 cells, are morphologically distinct from smaller smooth contacts and larger contacts induced by mitochondria-ER linker expression in COS-7 cells. RiboMERC formation is associated with increased mitochondrial potential, reduced in Gp78 knockout HT-1080 cells and induced by Gp78 ubiquitin ligase activity in COS-7 and HeLa cells. Knockdown of riboMERC tether RRBP1 eliminates riboMERCs in both wild-type and Gp78 knockout HT-1080 cells. By MCS-DETECT, Gp78-dependent riboMERCs present complex tubular shapes that intercalate between and contact multiple mitochondria. MCS-DETECT of 3D whole-cell super-resolution image volumes, therefore, identifies novel dual control of tubular riboMERCs, whose formation is dependent on RRBP1 and size modulated by Gp78 E3 ubiquitin ligase activity.
Insights
A new algorithm, MCS-DETECT, reveals distinct mitochondria-ER contacts (MERCs). It shows ribosome-studded MERCs (riboMERCs) are controlled by RRBP1 and Gp78 E3 ubiquitin ligase activity.
Area of Science:
- Cell Biology
- Molecular Biology
- Microscopy
Background:
- Mitochondria-ER contacts (MERCs) are crucial for cellular function.
- Current fluorescent microscopy techniques have limitations in resolving subpixel interorganelle distances.
- Understanding the morphology and regulation of MERCs is essential.
Purpose of the Study:
- To develop and validate a novel algorithm, MCS-DETECT, for high-resolution analysis of MERCs.
- To characterize the morphology of different types of MERCs, including ribosome-studded MERCs (riboMERCs).
- To investigate the molecular mechanisms regulating riboMERC formation and morphology.
Main Methods:
- Development of the MCS-DETECT algorithm for reconstructing subpixel resolution MERCs from 3D super-resolution image volumes.
- Comparative morphological analysis of MERCs in HT-1080 and COS-7 cells.
- Investigating the role of Gp78 E3 ubiquitin ligase and RRBP1 in riboMERC formation.
Main Results:
- MCS-DETECT successfully reconstructs subpixel resolution MERCs.
- Distinct morphologies of MERCs were identified: small smooth contacts, larger contacts, and elongated riboMERCs.
- RiboMERC formation is dependent on RRBP1 and modulated by Gp78 E3 ubiquitin ligase activity, influencing mitochondrial potential.
Conclusions:
- MCS-DETECT is a powerful tool for analyzing MERCs at high resolution.
- Novel insights into the dual regulation of tubular riboMERCs by RRBP1 and Gp78 were uncovered.
- Gp78 E3 ubiquitin ligase activity plays a significant role in modulating the size and complexity of Gp78-dependent riboMERCs.
More Related Videos
07:55Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights
Published on: June 16, 2023
08:27Visualization and Quantification of Endogenous Intra-Organelle Protein Interactions at ER-Mitochondria Contact Sites by Proximity Ligation Assays
Published on: October 20, 2023
Related Concept Videos
01:28The Inner Mitochondrial Membrane
01:45Mitochondrial Membranes
01:26Insertion of Single-pass Transmembrane Proteins in the RER
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
01:19Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:29Insertion of Multi-pass Transmembrane Proteins in the RER
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
01:12Porin Insertion in the Outer Mitochondrial Membrane
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...