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Mitofusin-2 regulates mitochondrial and endoplasmic reticulum morphology and tethering: the role of Ras

Olga Martins de Brito1, Luca Scorrano

  • 1Dulbecco-Telethon Institute, Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy.

Mitochondrion
|March 10, 2009
PubMed

Insights

Mitofusin 2 (MFN2) links endoplasmic reticulum and mitochondria. Loss of MFN2 activates ERK signaling, but this pathway does not mediate MFN2

Area of Science:

  • Cell Biology
  • Mitochondrial Dynamics
  • Organelle Communication

Background:

  • Endoplasmic reticulum (ER) and mitochondria communication is vital for cellular functions, including calcium homeostasis, lipid synthesis, and apoptosis.
  • Mitochondrial GTPase mitofusin 2 (MFN2) resides at mitochondria-associated membranes (MAM) and ER, forming bridges between organelles.
  • MFN2 interacts with and inhibits the proto-oncogene Ras, which regulates cell proliferation, cycle, and morphology.

Purpose of the Study:

  • To investigate whether signaling cascades downstream of Ras, specifically the Ras-MAPK-ERK pathway, influence MFN2's ability to tether ER and mitochondria.
  • To determine if ERK hyperactivation in MFN2-deficient cells is responsible for altered ER-mitochondria tethering and morphology.

Main Methods:

  • Analysis of ERK1 activity in MFN2-deficient cells.
  • Genetic and pharmacological manipulation of the Ras-MAPK-ERK signaling pathway.
  • Assessment of ER and mitochondrial morphology and tethering in response to pathway modulation.

Main Results:

  • Extracellular regulated kinase (ERK) 1 was found to be hyperactivated in cells lacking MFN2.
  • Modulating the Ras-MAPK-ERK cascade did not affect ER and mitochondrial morphology.
  • Interorganellar tethering between ER and mitochondria remained unchanged despite alterations in Ras-MAPK-ERK signaling.

Conclusions:

  • Sustained Ras signaling is not the mechanism by which MFN2 deficiency impacts ER-mitochondria tethering and morphology.
  • MFN2 plays a direct role in maintaining ER-mitochondria juxtaposition, independent of the Ras-MAPK-ERK pathway's influence on organelle tethering.

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