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Friday 16 July 2004

Definition: The actin-related protein-2/3 (ARP2/3) complex is a 220-kD multiprotein complex, that is a central player in the regulation of the actin cytoskeleton.

This complex contains actin-related proteins (Arps) in the Arp2 and Arp3 families and therefore was named the Arp2/3 complex.

The cellular functions of the actin cytoskeleton require precise regulation of both the initiation of actin polymerization and the organization of the resulting filaments.



The cadherin-catenine system

β-catenin (CTNNB1) links cadherins with α-catenin, which, in turn, connects to actin, thus completing the connection with the cytoskeleton.

Cell-to-cell interactions mediated by cadherins (CDHs) and catenins (CTNNs) play a major role in regulating cell motility, proliferation, and differentiation and account for the inhibition of cell proliferation that occurs when cultured normal cells contact each other (contact inhibition).

The formation of cadherin-mediated cell-cell junctions is accompanied by a profound remodeling of the actin cytoskeleton.

The Arp2/3 complex and its activator cortactin drive the assembly of branching actin-filament arrays, and formin-1 promotes the nucleation of non-branching actin filaments. Recruitment of these actin nucleators to nascent adhesions, formation of the links between them and the cytoplasmic cadherin domain, and triggering of their actin-polymerizing functions are vital steps in the development of cell-cell junctions.


- The ARP2/3 complex promotes actin assembly in lamellipodia and may participate in lamellipodial protrusion.


- Listeria monocytogenes infection

  • This 220-kD multiprotein complex from human platelets induces actin polymerization at the L. monocytogenes cell surface and mediates bacterial motility.

See also

- actin assembly
- actin polymerization
- cytoskeleton
- actin filaments
- lamellipodia protrusion
- lamellipodia retraction


- Goley ED, Welch MD. The ARP2/3 complex: an actin nucleator comes of age. Nat Rev Mol Cell Biol. 2006 Oct;7(10):713-26. PMID: 16990851

- Stradal TE, Scita G. Protein complexes regulating Arp2/3-mediated actin assembly. Curr Opin Cell Biol. 2006 Feb;18(1):4-10. PMID: 16343889