ADF/Cofilin Binds Phosphoinositides in a Multivalent Manner to Act as a PIP2-Density Sensor

作者：Zhao Hongxia^*; Hakala Markku; Lappalainen Pekka

来源：Biophysical Journal, 2010, 98(10): 2327-2336.

DOI：10.1016/j.bpj.2010.01.046

Actin-depolymerizing-factor (ADF)/cofilins have emerged as key regulators of cytoskeletal dynamics in cell motility, morphogenesis, endocytosis, and cytokinesis. The activities of ADF/cofilins are regulated by membrane phospholipid P1(4,5)P-2 in vitro and in cells, but the mechanism of the ADF/cofilin-P1(4,5)P-2 interaction has remained controversial. Recent studies suggested that ADF/cofilins interact with PI(4,5)P-2 through a specific binding pocket, and that this interaction is dependent on pH. Here, we combined systematic mutagenesis with biochemical and spectroscopic methods to elucidate the phosphoinositide-binding mechanism of ADF/cofilins. Our analysis revealed that cofilin does not harbor a specific PI(4,5)P-2-binding pocket, but instead interacts with PI(4,5)P-2 through a large, positively charged surface of the molecule. Cofilin interacts simultaneously with multiple PI(4,5)P-2 headgroups in a cooperative manner. Consequently, interactions of cofilin with membranes and actin exhibit sharp sensitivity to PI(4,5)P-2 density. Finally, we show that cofilin binding to PI(4,5)P-2 is not sensitive to changes in the pH at physiological salt concentration, although the PI(4,5)P-2-clustering activity of cofilin is moderately inhibited at elevated pH. Collectively, our data demonstrate that ADF/cofilins bind PI(4,5)P-2 headgroups through a multivalent, cooperative mechanism, and suggest that the actin filament disassembly activity of ADF/cofilin can be accurately regulated by small changes in the PI(4,5)P-2 density at cellular membranes.

• 出版日期2010-5-19