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Ultrastructure and dynamics of the actin-myosin II cytoskeleton during mitochondrial fission

Changsong Yang1, Tatyana M Svitkina2

  • 1Department of Biology, University of Pennsylvania, Philadelphia, PA, USA.

Nature Cell Biology
|April 17, 2019
PubMed

Insights

Mitochondrial fission involves actin and myosin II. New research reveals an interstitial actin network that, when deformed by myosin II, initiates mitochondrial constriction for cell division.

Area of Science:

  • Cell Biology
  • Cytoskeletal Dynamics

Background:

  • Mitochondrial fission is crucial for cellular function.
  • The precise mechanism of mitochondrial preconstriction by actin and myosin II is not fully understood.
  • The cytoskeletal ultrastructure at mitochondrial constriction sites remains largely uncharacterized.

Purpose of the Study:

  • To elucidate the role of the cytoskeletal network in mitochondrial fission.
  • To investigate the ultrastructural organization of actin and myosin II at mitochondrial constriction sites.
  • To propose a mechanism for how myosin II facilitates mitochondrial preconstriction.

Main Methods:

  • Platinum replica electron microscopy was employed to visualize the ultrastructure of mitochondria and associated cytoskeletal elements.
  • Cellular models were used to observe spontaneous and induced mitochondrial constrictions.
  • Immunofluorescence microscopy was utilized to track the localization of F-actin and non-muscle myosin II during mitochondrial fission.

Main Results:

  • Mitochondria are embedded within an interstitial cytoskeletal network rich in unbranched actin filaments.
  • Mitochondrial constrictions are associated with a criss-cross array of actin filaments.
  • Non-muscle myosin II localizes near constrictions, with F-actin clouds colocalizing with constriction sites during induced fission.

Conclusions:

  • A model is proposed where myosin II induces deformations in the interstitial actin network.
  • These deformations apply pressure on mitochondria, initiating curvature-sensing mechanisms for constriction.
  • This study clarifies the cytoskeletal basis of mitochondrial fission initiation.

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