Related Experiment Video

Updated: Jul 25, 2026

A Faster, High Resolution, mtPA-GFP-based Mitochondrial Fusion Assay Acquiring Kinetic Data of Multiple Cells in Parallel Using Confocal Microscopy
10:45

A Faster, High Resolution, mtPA-GFP-based Mitochondrial Fusion Assay Acquiring Kinetic Data of Multiple Cells in Parallel Using Confocal Microscopy

Published on: July 20, 2012

Rat liver GTP-binding proteins mediate changes in mitochondrial membrane potential and organelle fusion

J D Cortese1

  • 1Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill, North Carolina 27599-7090, USA.

The American Journal of Physiology
|March 10, 1999
PubMed

Insights

Mitochondrial fusion, crucial for cell health, is regulated by GTP-binding proteins (mtg). These proteins increase mitochondrial membrane potential, influencing fusion and cellular energetics.

Area of Science:

  • Cell Biology
  • Mitochondrial Dynamics
  • Biochemistry

Background:

  • Mitochondrial morphology varies in healthy and diseased cells, suggesting regulation by fusion processes.
  • A fraction of mitochondrial outer membrane proteins (mtg) with GTP-binding and fusogenic properties was previously isolated.

Purpose of the Study:

  • To investigate the role of mtg in mitochondrial fusion and its relationship with mitochondrial membrane potential (DeltaPsi).
  • To explore the influence of cellular energetics on mitochondrial morphology.

Main Methods:

  • Quantitative confocal microscopy to measure DeltaPsi changes in response to mtg.
  • Use of GTPase modulators (GTPgammaS, excess GTP, AlF4) and inhibitors (Bordetella pertussis toxin) to probe fusion mechanisms.
  • Stereometric analysis to assess the impact of altered DeltaPsi and ATP synthesis on mitochondrial fusion.

Main Results:

  • Mitochondrial outer membrane fraction (mtg) addition transiently increased DeltaPsi in rat hepatocytes, fibroblasts, and rabbit myocytes.
  • The mtg-induced DeltaPsi increase was inhibited by GTPase modulators and AlF4, indicating a link between DeltaPsi and fusion.
  • Decreasing DeltaPsi or ATP synthesis via respiratory inhibitors reduced mtg- and AlF4-induced fusion.
  • G protein inhibition led to mitochondrial hyperpolarization and loss of AlF4-dependent fusion.

Conclusions:

  • GTPases (mtg) exert DeltaPsi-dependent control over mitochondrial fusion.
  • Changes in mitochondrial membrane potential are upstream of AlF4-induced fusion.
  • Cellular energetics play a role in modulating mammalian mitochondrial morphology.

More Related Videos

Multi-parameter Measurement of the Permeability Transition Pore Opening in Isolated Mouse Heart Mitochondria13:42

Multi-parameter Measurement of the Permeability Transition Pore Opening in Isolated Mouse Heart Mitochondria

Published on: September 7, 2012

A Model Membrane Platform for Reconstituting Mitochondrial Membrane Dynamics10:31

A Model Membrane Platform for Reconstituting Mitochondrial Membrane Dynamics

Published on: September 2, 2020

Related Concept Videos

GTPases and their Regulation02:14

GTPases and their Regulation

Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒  small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...
Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial precursors...
Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
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,...
Energy to Drive Translocation01:37

Energy to Drive Translocation

Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...
Activation and Inactivation of G Proteins01:22

Activation and Inactivation of G Proteins

Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...