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    The role of profilin in formin-nucleated actin cable assembly[Edit]

    Profilin binds simultaneously to formin and actin monomers; this interaction tethers multiple profilin-actin complexes near the growing end of actin filaments, which promotes the processive addition of actin subunits [1, 2]. Profilin uses the energy from ATP hydrolysis generated during actin polymerization to facilitate actin assembly [2]. Profilin binds to cytoplasmic ATP-actin monomers better than cytoplasmic ADP-actin monomers [3]. 

    Profilin has been suggested to generally increase the elongation rate of formin-associated filaments by:

    * Catalyzing the exchange of ADP for ATP on actin monomers [4, 5].
    * Blocking free monomers from elongating pointed ends [4].
    * Lowering the critical concentration at the barbed end [2].
    * Promoting the association of G-actin-ATP to the barbed end [6].

    Importantly however, profilin also promotes disassembly of actin filaments by sequestering monomeric G-actin, thereby blocking its association with the barbed ends and promoting its disassembly from the pointed ends of actin filaments [4]. The combined actions of profilin and ADF/cofilin synergize to enhance turnover of actin filaments [7].

    References

    1. Watanabe N., Madaule P., Reid T., Ishizaki T., Watanabe G., Kakizuka A., Saito Y., Nakao K., Jockusch BM., Narumiya S. p140mDia, a mammalian homolog of Drosophila diaphanous, is a target protein for Rho small GTPase and is a ligand for profilin. EMBO J. 1997; 16(11). [PMID: 9214622]
    2. Pantaloni D., Carlier MF. How profilin promotes actin filament assembly in the presence of thymosin beta 4. Cell 1993; 75(5). [PMID: 8252614]
    3. Perelroizen I., Didry D., Christensen H., Chua NH., Carlier MF. Role of nucleotide exchange and hydrolysis in the function of profilin in action assembly. J. Biol. Chem. 1996; 271(21). [PMID: 8647830]
    4. Ressad F., Didry D., Egile C., Pantaloni D., Carlier MF. Control of actin filament length and turnover by actin depolymerizing factor (ADF/cofilin) in the presence of capping proteins and ARP2/3 complex. J. Biol. Chem. 1999; 274(30). [PMID: 10409644]
    5. Yarmola EG., Dranishnikov DA., Bubb MR. Effect of profilin on actin critical concentration: a theoretical analysis. Biophys. J. 2008; 95(12). [PMID: 18835900]
    6. Kang F., Purich DL., Southwick FS. Profilin promotes barbed-end actin filament assembly without lowering the critical concentration. J. Biol. Chem. 1999; 274(52). [PMID: 10601251]
    7. Didry D., Carlier MF., Pantaloni D. Synergy between actin depolymerizing factor/cofilin and profilin in increasing actin filament turnover. J. Biol. Chem. 1998; 273(40). [PMID: 9748225]
    Updated on: Mon, 20 Oct 2014 09:40:51 GMT
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