Microscopic evidence that actin-interacting protein 1 actively disassembles actin-depolymerizing factor/Cofilin-bound actin filaments.
Actin-depolymerizing factor (ADF)/cofilin and gelsolin are the two major factors to enhance actin filament disassembly. Actin-interacting protein 1 (AIP1) enhances fragmentation of ADF/cofilin-bound filaments and caps the barbed ends. However, the mechanism by which AIP1 disassembles ADF/cofilin-bound filaments is not clearly understood. Here, we directly observed the effects of these proteins on filamentous actin by fluorescence microscopy and gained novel insight into the function of ADF/cofilin and AIP1. ADF/cofilin severed filaments and AIP1 strongly enhanced disassembly at nanomolar concentrations. However, gelsolin, gelsolin-actin complex, or cytochalasin D did not enhance disassembly by ADF/cofilin, suggesting that the strong activity of AIP1 cannot be explained by simple barbed end capping. Barbed end capping by ADF/cofilin and AIP1 was weak and allowed filament elongation, whereas gelsolin or gelsolin-actin complex strongly capped and inhibited elongation. These results suggest that AIP has an active role in filament severing or depolymerization and that ADF/cofilin and AIP1 are distinct from gelsolin in modulating filament elongation.
Ono
Shoichiro
S
Department of Pathology, Emory University, Atlanta, Georgia 30322, USA. sono@emory.edu
Mohri
Kurato
K
Ono
Kanako
K
D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors; D000199:Actins / Q000378:metabolism*; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D051345:Destrin; D018260:Gelsolin / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D011817:Rabbits
D051339:Actin Depolymerizing Factors; D000199:Actins; D029742:Caenorhabditis elegans Proteins; D051345:Destrin; D018260:Gelsolin; D008840:Microfilament Proteins; C495209:UNC-60 protein, C elegans; C115237:actin interacting protein 1