The Cytoskeleton & Cell Motility

Three Main Cytoskeletal Components

Actin filaments, Microtubules, and Intermediate filaments.

cytoskeleton role

structure, cell movement, organize and drive intracellular traffic

guide mitosis and meiosis

Microtubule Subunits & Structure

Hollow cylinders made of α and β tubulin heterodimers arranged into protofilaments (usually 13).

Microtubule Polarity

Plus end (β-tubulin exposed, faster growing); Minus end (α-tubulin exposed, nucleated at centrosome).

Mechanism of Taxol (Paclitaxel)

Stabilizes microtubules, preventing disassembly; used in cancer treatment.

Mechanism of Colchicine and Vinblastine

Binds tubulin subunits and prevents microtubule polymerization.

Actin Filament Structure

Two-stranded helical polymers composed of α, β, or γ actin monomers.

Three Steps of Cell Locomotion

1. Protrusion of leading edge

2. Adhesion at front / detachment at rear

3. Movement of cell body

Role of Rac1 in Cell Movement

Rho GTPase that stimulates leading edge protrusion via actin nucleation (e.g., Arp2/3 complex).

Role of RhoA in Cell Movement

Rho GTPase that regulates retraction of the trailing/lagging edge.

Molecular Clutch Engaged vs. Disengaged

Engaged: links actin to integrins/ECM driving cell forward. Disengaged: results in actin retrograde flow without movement.