Arp2/3 complex-dependent actin networks constrain myosin II function in driving retrograde actin flow.
The Arp2/3 complex nucleates actin filaments to generate networks at the leading edge of motile cells. Nonmuscle myosin II produces contractile forces involved in driving actin network translocation. We inhibited the Arp2/3 complex and/or myosin II with small molecules to investigate their respective functions in neuronal growth cone actin dynamics. Inhibition of the Arp2/3 complex with CK666 reduced barbed end actin assembly site density at the leading edge, disrupted actin veils, and resulted in veil retraction. Strikingly, retrograde actin flow rates increased with Arp2/3 complex inhibition; however, when myosin II activity was blocked, Arp2/3 complex inhibition now resulted in slowing of retrograde actin flow and veils no longer retracted. Retrograde flow rate increases induced by Arp2/3 complex inhibition were independent of Rho kinase activity. These results provide evidence that, although the Arp2/3 complex and myosin II are spatially segregated, actin networks assembled by the Arp2/3 complex can restrict myosin II-dependent contractility with consequent effects on growth cone motility.
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511, USA.
Qing
Q
Yang
Xiao-Feng
XF
Zhang
Thomas D
TD
Pollard
Paul
P
Forscher
D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001048:Aplysia / Q000378:metabolism* / Q000648:ultrastructure; D020439:Growth Cones / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D024462:Myosin Type II / Q000378:metabolism*
D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D024462:Myosin Type II