Arp2/3 complex-deficient mouse fibroblasts are viable and have normal leading-edge actin structure and function

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The Arp2/3 complex is a key regulator of actin dynamics.
• Its role in cellular processes like motility and actin remodeling is crucial.
• Understanding its specific functions requires targeted genetic manipulation.

Purpose of the Study:

• To investigate the necessity of the Arp2/3 complex for cellular functions.
• To determine the Arp2/3 complex's role in Listeria monocytogenes intracellular motility.
• To assess the Arp2/3 complex's contribution to leading-edge actin remodeling.

Main Methods:

• RNA interference (RNAi) was used to silence Arp3 protein expression in mouse embryonic fibroblasts.
• Intracellular motility of Listeria monocytogenes was measured.
• Actin nucleation activity was assessed.
• Cellular processes including lamellipodial structure, locomotion, spreading, actin assembly, and ruffling were analyzed.
• Inhibition of Arp2/3 complex function was achieved using neural Wiskott-Aldrich syndrome protein-derived peptides.

Main Results:

• Silencing Arp3 protein, a major subunit of the Arp2/3 complex, reduced Listeria motility and Arp2/3-dependent actin nucleation by up to 90%.
• Arp2/3-deficient cells maintained normal lamellipodial actin network structure, locomotion, spreading, actin assembly, and ruffling.
• Arp3-silenced cells treated with Arp2/3-inhibiting peptides showed normal PDGF-induced ruffling.

Conclusions:

• The Arp2/3 complex is essential for Arp2/3-mediated actin nucleation and Listeria intracellular motility.
• Despite this, the Arp2/3 complex is dispensable for fundamental cellular processes like cell locomotion, spreading, and leading-edge actin remodeling.
• These findings suggest alternative pathways contribute to actin dynamics at the leading edge of cells.