| Identification of the p 16 Arc subunit of the Arp 2 / 3 complex as a substrate of MAPK activated protein kinase 2 by proteomic analysis . ^^^ In vitro studies confirmed that MAPKAPK 2 interacts with and phosphorylates the A isoform , but not the B isoform , of p 16 Arc with a stoichiometry of 0 . 6 to 0 . 7 . ^^^ MAPKAPK 2 also phosphorylated p 16 Arc in intact Arp2 / 3 complexes precipitated from neutrophil lysates . ^^^ The ability of MAPKAPK 2 to phosphorylate one isoform of p 16 Arc suggests a possible mechanism by which the p 38 MAPK cascade regulates remodeling of the actin cytoskeleton . . ^^^ |