Disassembly of actin filaments is important for many processes that involve rapid reorganization of cell shape such as cell movement and division. Cofilin is a vital disassembly protein however one limitation of cofilin is that it can stabilize filaments at saturating concentrations. Nadkarni and Brieher showed that the amount of cofilin in thymus extract is too high to allow disassembly of single actin filaments in solution. They discovered that Aip1 is able to disassemble filaments even in the presence of stabilizing concentrations of cofilin.
In the presence of Aip1, stable filaments underwent increased severing and disassembly at filament ends. This indicated that Aip1 could act all along the sides of cofilin-decorated actin filaments. However, previous work had shown that Aip1 was a capping factor that acted at filament ends. Nadkarni and Brieher went on to show that Aip1 acts differently than a well-characterized capping factor CapZ, and does not behave like a capping factor. This led to a revision of the view of Aip1's mode of action on actin filaments.