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Profilin enhances Cdc42-induced nucleation of actin polymerization
被引:106
作者:
Yang, CS
Huang, MZ
DeBiasio, J
Pring, M
Joyce, M
Miki, H
Takenawa, T
Zigmond, SH
[1
]
机构:
[1] Univ Penn, Dept Biol, Philadelphia, PA 19104 USA
[2] Univ Penn, Dept Physiol, Philadelphia, PA 19104 USA
[3] Univ Tokyo, Inst Med Sci, Dept Biochem, Tokyo 1088639, Japan
关键词:
actin polymerization;
nucleation;
Cdc42;
leukocytes;
profilin;
D O I:
10.1083/jcb.150.5.1001
中图分类号:
Q2 [细胞生物学];
学科分类号:
071009 ;
090102 ;
摘要:
We find that profilin contributes in several ways to Cdc42-induced nucleation of actin filaments in high speed supernatant of lysed neutrophils. Depletion of profilin inhibited Cdc42-induced nucleation; re-addition of profilin restored much Of the activity. Mutant profilins with a decreased affinity for either actin or poly-L-proline were less effective at restoring activity. Whereas Cdc42 must activate Wiskott-Aldrich Syndrome protein (WASP) to stimulate nucleation by the Arp2/3 complex, VCA (verpolin homology, cofilin, and acidic domain contained in the COOH-terminal fragment of N-WASP) constitutively activates the Arp2/3 complex. Nucleation by VCA was not inhibited by profilin depletion. With purified N-WASP and Arp2/3 complex, Cdc42-induced nucleation did not require profilin but was enhanced by profilin, wild-type profilin being more effective than mutant profilin with reduced affinity for poly-L-proline. Nucleation by the Arp2/3 complex is a function of the free G-actin concentration. Thus, when profilin addition decreased the free G-actin concentration, it inhibited Cdc42- and VCA-induced nucleation. However, when profilin was added with G-actin in a ratio that maintained the initial free G-actin concentration, it increased the rate of both Cdc42- and VCA-induced nucleation. This enhancement, also seen with purified proteins, was greatest when the free G-actin concentration was low. These data suggest that under conditions present in intact cells, profilin enhances nucleation by activated Arp2/3 complex.
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页码:1001 / 1012
页数:12
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