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Myosin VI has a one track mind versus myosin Va when moving on actin bundles or at an intersection

M Yusuf Ali1, Samantha B Previs, Kathleen M Trybus

  • 1Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA. yusuf.ali@uvm.edu

Traffic (Copenhagen, Denmark)
|October 11, 2012
PubMed

Insights

Myosin VI (myoVI) and myosin Va (myoVa) motors navigate the actin cytoskeleton differently. MyoVI prefers to stay on its current filament, while myoVa frequently switches tracks, revealing distinct motor behaviors.

Area of Science:

  • Cell Biology
  • Biophysics
  • Cytoskeletal Dynamics

Background:

  • Myosin motors (myoVI and myoVa) function as intracellular transporters and anchors, moving along actin filaments.
  • The actin cytoskeleton's complex, intersecting structure poses challenges for motor protein navigation.
  • Understanding motor protein maneuverability is key to elucidating their cellular roles.

Purpose of the Study:

  • To investigate the inherent differences in how myoVI and myoVa interact with and maneuver through complex actin cytoskeletal networks.
  • To determine if motor protein behavior at actin intersections is distinct between myoVI and myoVa.

Main Methods:

  • Development of an in vitro model system using intersecting actin filaments and bundles of varying polarity (fascin-actin and α-actinin-actin).
  • Utilizing individual quantum dot-labeled myoVI and myoVa motors to analyze stepping dynamics on these actin tracks.
  • Employing a myoVI chimera mutant with an altered lever arm (myoVa IQs) to probe structural influences on motor behavior.

Main Results:

  • Myosin VI exhibits a preference for remaining on its original actin filament, demonstrating reduced filament switching.
  • Myosin Va displays a higher probability of switching filaments at intersections and within bundles.
  • A myoVI chimera with a myoVa lever arm mimicked myoVI's on-track behavior, suggesting the lever arm is not the primary determinant of this difference.

Conclusions:

  • Myosin VI and Myosin Va possess distinct intrinsic mechanisms for navigating the actin cytoskeleton.
  • Myosin VI's tendency to stay on track may be crucial for its function as an intracellular anchor.
  • Structural elements beyond the lever arm likely dictate Myosin VI's unique maneuverability on actin networks.

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