TY - JOUR
T1 - Cofilin produces newly polymerized actin filaments that are preferred for dendritic nucleation by the Arp2/3 complex
AU - Ichetovkin, Ilia
AU - Grant, Wayne
AU - Condeelis, John
N1 - Funding Information:
The authors wish to thank Mike Cammer, Jeff Wyckoff, and members of the Analytic Imaging Facility for help in imaging; and Corina Sormiento for double-blind counting of filaments. We also wish to thank Dr. Paul Janmey (University of Pennsylvania) for advise about the preparation of AMPPNP-actin. This work was supported by grants from the National Institutes of Health.
PY - 2002/1/8
Y1 - 2002/1/8
N2 - One of the earliest events in the process of cell motility is the massive generation of free actin barbed ends, which elongate to form filaments adjacent to the plasma membrane at the tip of the leading edge. Both cofilin and Arp2/3 complex have been proposed to contribute to barbed end formation during cell motility. Attempts to assess the functions of cofilin and Arp2/3 complex in vivo indicate that both cofilin and Arp2/3 complex contribute to actin polymerization: cofilin by severing and Arp2/3 by nucleating and branching. In order to determine if the activities of cofilin and Arp2/3 complex interact, we employed a light microscope-based assay to visualize actin polymerization directly in the presence of both proteins. The results indicate that cofilin generates barbed ends to increase the mass of freshly polymerized F-actin but does not directly affect the activity of Arp2/3 complex. However, while ADP, ADP-Pi, and newly polymerized ATP-filaments are all capable of supporting Arp2/3-mediated branching, newly polymerized F-actin supports most of the Arp2/3-induced branch formation. The results suggest that, in vivo, cofilin contributes to barbed end formation byinducing the initial increase in the number of barbed ends leading to increased ATP-F-actin, which in turn supports higher levels of dendritic nucleation by active Arp2/3 complex.
AB - One of the earliest events in the process of cell motility is the massive generation of free actin barbed ends, which elongate to form filaments adjacent to the plasma membrane at the tip of the leading edge. Both cofilin and Arp2/3 complex have been proposed to contribute to barbed end formation during cell motility. Attempts to assess the functions of cofilin and Arp2/3 complex in vivo indicate that both cofilin and Arp2/3 complex contribute to actin polymerization: cofilin by severing and Arp2/3 by nucleating and branching. In order to determine if the activities of cofilin and Arp2/3 complex interact, we employed a light microscope-based assay to visualize actin polymerization directly in the presence of both proteins. The results indicate that cofilin generates barbed ends to increase the mass of freshly polymerized F-actin but does not directly affect the activity of Arp2/3 complex. However, while ADP, ADP-Pi, and newly polymerized ATP-filaments are all capable of supporting Arp2/3-mediated branching, newly polymerized F-actin supports most of the Arp2/3-induced branch formation. The results suggest that, in vivo, cofilin contributes to barbed end formation byinducing the initial increase in the number of barbed ends leading to increased ATP-F-actin, which in turn supports higher levels of dendritic nucleation by active Arp2/3 complex.
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U2 - 10.1016/S0960-9822(01)00629-7
DO - 10.1016/S0960-9822(01)00629-7
M3 - Article
C2 - 11790308
AN - SCOPUS:0037039167
SN - 0960-9822
VL - 12
SP - 79
EP - 84
JO - Current Biology
JF - Current Biology
IS - 1
ER -