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Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
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Force Generation by Membrane-Associated Myosin-I

Serapion Pyrpassopoulos1, Göker Arpağ2, Elizabeth A Feeser1

  • 1The Pennsylvania Muscle Institute and Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia PA 19104-6085, USA.

Scientific Reports
|May 10, 2016
PubMed

Insights

Vertebrate myosin-IC (Myo1c) generates force parallel to cell membranes by interacting with actin filaments and lipid bilayers. Its force generation is enhanced when it operates away from the membrane plane or in slower-diffusing membrane regions.

Area of Science:

  • Cell biology
  • Biophysics
  • Molecular motors

Background:

  • Vertebrate myosin-IC (Myo1c) is a type-1 myosin crucial for linking cell membranes to the cytoskeleton.
  • It possesses an actin-binding motor domain and a phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2)-binding tail domain.
  • Previous studies showed Myo1c propels actin filaments in fluid bilayers but its force-generating capacity against load was unexplored.

Purpose of the Study:

  • To investigate the force-generating capabilities of membrane-bound Myo1c against external load.
  • To measure the diffusion coefficient of single membrane-bound Myo1c molecules.
  • To explore how Myo1c ensembles develop and sustain forces while interacting with fluid lipid bilayers.

Main Methods:

  • Utilized optical tweezers for force-relaxation experiments to measure single Myo1c diffusion.
  • Assessed the force development and sustainability by ensembles of membrane-bound Myo1c.
  • Developed a computational model to interpret experimental data on Myo1c force generation.

Main Results:

  • Single membrane-bound Myo1c molecules' diffusion coefficients were measured.
  • Ensembles of Myo1c demonstrated the ability to develop and sustain forces.
  • Computational modeling indicated Myo1c ensembles generate forces parallel to lipid bilayers.

Conclusions:

  • Myosin-IC ensembles can generate forces parallel to lipid bilayers.
  • Force generation is optimized when Myo1c operates away from the membrane plane.
  • Anchoring to slowly diffusing membrane regions enhances Myo1c force generation.

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