Related Experiment Video

Updated: May 19, 2026

Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
08:57

Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays

Published on: February 4, 2021

Membrane-bound myo1c powers asymmetric motility of actin filaments

Serapion Pyrpassopoulos1, Elizabeth A Feeser, Jessica N Mazerik

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

Current Biology : CB
|August 7, 2012
PubMed

Insights

Myosin-Ic (myo1c) powers actin filament movement on cell membranes, exhibiting a unique counterclockwise turning motion. This specific motility is not shared by other myosin-I family members, suggesting a novel mechanism for membrane-related asymmetry.

Area of Science:

  • Cell Biology
  • Biophysics
  • Molecular Motors

Background:

  • Class I myosins are essential molecular motors connecting the actin cytoskeleton to cellular membranes.
  • Myosin-Ic (myo1c) binds to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)) via its tail domain, crucial for cellular localization.
  • Myosins are involved in membrane tension, dynamics, and mechanosignal transduction.

Purpose of the Study:

  • To investigate the motility of myosin-Ic (myo1c) on fluid membranes containing physiological PtdIns(4,5)P(2) concentrations.
  • To determine if the tail domain of myo1c is necessary for its observed motility characteristics.
  • To compare the motility of myo1c with other myosin-I isoforms (myo1a, myo1b).

Main Methods:

  • In vitro motility assays using fluid membranes with controlled phospholipid compositions.
  • Biochemical assays with truncated myo1c constructs (motor domain and lever arm).
  • Microscopic observation and analysis of actin filament movement and turning direction.

Main Results:

  • Myosin-Ic powers actin motility on PtdIns(4,5)P(2)-containing membranes, inhibited by high anionic phospholipid concentrations.
  • Actin filament motility driven by myo1c exhibits a distinct counterclockwise (leftward) curved path.
  • Truncated myo1c constructs lacking the tail domain also generate asymmetric, counterclockwise motility.
  • Myosin-Ia and myosin-Ib show actin gliding but lack the pronounced turning bias observed in myo1c.

Conclusions:

  • Myosin-Ic possesses a unique ability to generate counterclockwise actin motility on membranes.
  • The tail domain is not essential for this counterclockwise turning, suggesting the motor or lever arm contributes to asymmetry.
  • This directed motility may play a role in establishing cellular asymmetry relative to the plasma membrane.
  • Myosin-I family members exhibit distinct functional specializations in membrane-cytoskeleton interactions.

More Related Videos

Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers06:53

Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers

Published on: May 4, 2022

Reconstitution of Actin-Based Motility with Commercially Available Proteins08:40

Reconstitution of Actin-Based Motility with Commercially Available Proteins

Published on: October 28, 2022

Related Concept Videos

Role of Myosin in Cell Migration01:18

Role of Myosin in Cell Migration

Myosins are multimeric motor proteins involved in various cellular processes such as migration, adhesion, and proliferation. Myosin II is the most common type in animal cells, which binds and cross-links actin filaments.
Myosin II  is a hexamer comprising two heavy chains with globular heads and coiled-coil tails, two regulatory light chains, and two essential light chains. The ATPase sites on the myosin heads hydrolyze ATP, and the released phosphate generates the force for contraction. It is...
Overview of Myosin Structure and Function01:15

Overview of Myosin Structure and Function

Myosins are a family of molecular motor proteins, first identified in the skeletal muscles, where they are responsible for muscle contraction. Along with their role in muscle contraction, these proteins also play a role in the intracellular transport of molecules and vesicles. There are twenty-four classes of myosins based on their domain sequence and organization. Of the twenty-four, six classes (Myosin I, Myosin II, Myosin V, Myosin VI, Myosin VII, and Myosin X)  have been well characterized.
Actin Polymerization and Cell Motility01:13

Actin Polymerization and Cell Motility

Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
The Role of Actin and Myosin in Non-muscle Cells01:10

The Role of Actin and Myosin in Non-muscle Cells

Actin and myosin or actomyosin filaments also play a significant role in cells other than those involved in muscle contraction (which occurs within the sarcomere of muscle cells). The mechanism of non-muscle cell contractile bundles was first observed in Dictyostelium and Acanthamoeba. In non-muscle cells, two bundles are commonly found: stress fibers and actomyosin adherence belts. These contractile bundles are smaller and less organized than the ones found in muscle cells. They  are held...
Actin and Myosin in Muscle Contraction01:16

Actin and Myosin in Muscle Contraction

Actin and myosin are contractile proteins that form the sarcomere found in skeletal muscle tissues for regulating muscle contraction. Actin, a globular contractile protein, interacts with myosin for muscle contraction. The skeletal tissue appears striped or striated under a microscope due to the repeated arrangement of contractile proteins actin and myosin along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes...
Mechanism of Filopodia Formation01:39

Mechanism of Filopodia Formation

Filopodia are thin, actin-rich cellular protrusions that play an important role in many fundamental cellular functions. They vary in their occurrence, length, and positioning in different cell types, suggesting their diverse roles.
Their main function is to guide migrating cells during normal tissue morphogenesis or cancer metastasis by recognizing and making initial contacts with the extracellular matrix. However, they can also act as stationary cell anchors or help to establish communication...