Cofilin is a pH sensor for actin free barbed end formation: role of phosphoinositide binding

Christian Frantz, Gabriela Barreiro, Laura Dominguez, Xiaoming Chen, Robert Eddy, John Condeelis, Mark J.S. Kelly, Matthew P. Jacobson, Diane L. Barber

Research output: Contribution to journalArticlepeer-review

151 Scopus citations


Newly generated actin free barbed ends at the front of motile cells provide sites for actin filament assembly driving membrane protrusion. Growth factors induce a rapid biphasic increase in actin free barbed ends, and we found both phases absent in fibroblasts lacking H + efflux by the Na-H exchanger NHE1. The first phase is restored by expression of mutant cofilin-H133A but not unphosphorylated cofilin-S3A. Constant pH molecular dynamics simulations and nuclear magnetic resonance (NMR) reveal pH-sensitive structural changes in the cofilin C-terminal filamentous actin binding site dependent on His1 33. However, cofilin-H133A retains pH-sensitive changes in NMR spectra and severing activity in vitro, which suggests that it has a more complex behavior in cells. Cofilin activity is inhibited by phosphoinositide binding, and we found that phosphoinositide binding is pH-dependent for wild-type cofilin, with decreased binding at a higher pH. In contrast, phosphoinositide binding by cofilin-H133A is attenuated and pH insensitive. These data suggest a molecular mechanism whereby cofilin acts as a pH sensor to mediate a pH-dependent actin filament dynamics.

Original languageEnglish (US)
Pages (from-to)865-879
Number of pages15
JournalJournal of Cell Biology
Issue number5
StatePublished - Dec 1 2008

ASJC Scopus subject areas

  • Cell Biology


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