Actin Cytoskeleton Signaling

Actin cytoskeleton signaling is the complex network of biochemical pathways that dynamically control the assembly, disassembly, and organization of the cell's actin filaments (microfilaments). This signaling system allows the cell to rapidly change its shape, motility, and internal structure in response to external and internal stimuli.

The actin cytoskeleton acts as both a target and a transducer of signals, linking information from cell-surface receptors to fundamental cellular actions.

Core Mechanism The primary players in actin signaling are the Rho family of small GTPases:

External Stimuli: Signals from transmembrane receptors—such as Integrins (for adhesion), Receptor Tyrosine Kinases (RTKs), and G protein-coupled receptors (GPCRs)—activate specific Guanosine Exchange Factors (GEFs).

GTPase Activation: The GEFs activate one of the main Rho GTPases: RhoA, Rac1, or Cdc42, by helping them exchange GDP (inactive) for GTP (active).

Downstream Effects: Each activated GTPase then signals to its specific downstream effector proteins, which directly manipulate the actin network to create distinct cellular structures: