Arp2/3 Complex : downstream target of multiple signaling pathways leading to actin assembly
•  Localized in actin-based motility processes:
•  Listeria and Shigella propulsion (Welch, 1997; Egile et al., 1998)
•  Lamellipodium extension (Svitkina and Borisy, 1999)
•  Phagocytic cups (Machesky, 2000)
•  Endocytic vesicles (Taunton et al., 1999)
•  Actin patches (Li 1997; Cooper 1999)
•  Cadherin-mediated adhesion (Yap, 2002)
•  Morphological events in Drosophila (Cooley, 2002)
•  Must interact with an activator:
• ActA on Listeria
• WASP and Scar/WAVE proteins in eukaryotes
•  Cortactin, Abp1p,…, others ?
Arp3
47
Arp2
42
40
34
20
21
16
Non-zero crosslink
Two hybrid
Zero-length crosslink
(Higgs and Pollard, 1999)
R. Robinson et al
 (Science, 2001)
Topology of Arp2/3 complex, localization, activation of polymerization by ActA. (Slide 10)
Physiological activators of Arp2/3 complex : the WASp family. (Slide 11).