Motility and invasion are differentially modulated by Rho family GTPases.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Cell migration in vivo often involves tissue matrix invasion.
• Signaling pathways regulating cell invasion through 3D matrices are not well understood.
• Small GTPases Cdc42, Rac, and Rho are critical regulators of the actin cytoskeleton and cell adhesion.

Purpose of the Study:

• To investigate the roles of Cdc42, Rac, and Rho GTPases in PDGF-BB-stimulated cell invasion through 3D collagen matrices.
• To differentiate the roles of these GTPases in 3D invasion versus 2D migration.

Main Methods:

• Expression of dominant-negative and constitutively active forms of Cdc42, Rac, and Rho in Rat1 fibroblasts.
• Assessment of cell invasion into 3D collagen matrices.
• Assessment of cell locomotion across a planar substrate using a Boyden chamber assay.
• Investigation of the role of PI-3-kinase activity.

Main Results:

• Inhibition of Cdc42, Rac, or Rho GTPase activity blocked PDGF-BB-stimulated invasion into 3D matrices.
• Only Rac activation was essential for PDGF-BB-stimulated 2D migration.
• Constitutively active Cdc42 or Rho, and to a lesser extent Rac, inhibited PDGF-induced invasion.
• Constitutively active Rac stimulated basal invasion independently of PI-3-kinase, an effect dependent on its effector function.

Conclusions:

• Cellular invasion through 3D matrices necessitates optimal activation levels of Cdc42, Rho, and Rac GTPases.
• Cell migration and invasion are differentially regulated by Rho family GTPases.
• These findings provide insight into the molecular mechanisms governing cell invasion in complex 3D environments.