title: Cofilin is a pH sensor for actin free barbed end formation: role of phosphoinositide binding.
abstract: 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 His133. 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.
authors.affiliation: Department of Cell and Tissue Biology, University of California, San Francisco, CA 94143, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Frantz
authors.forename: Gabriela
authors.initials: G
authors.lastname: Barreiro
authors.forename: Laura
authors.initials: L
authors.lastname: Dominguez
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Chen
authors.forename: Robert
authors.initials: R
authors.lastname: Eddy
authors.forename: John
authors.initials: J
authors.lastname: Condeelis
authors.forename: Mark J S
authors.initials: MJ
authors.lastname: Kelly
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Jacobson
authors.forename: Diane L
authors.initials: DL
authors.lastname: Barber
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002465:Cell Movement; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008840:Microfilament Proteins / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D010716:Phosphatidylinositols / Q000378:metabolism*; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D008840:Microfilament Proteins; D010716:Phosphatidylinositols; D010982:Platelet-Derived Growth Factor; D015800:Protozoan Proteins; D017923:Sodium-Hydrogen Exchangers; C047604:actophorin protein, Acanthamoeba