Activated MAP kinase-activated protein kinase (MAPK/MAPKAPK) 2 and 3 in turn phosphorylate heat shock protein beta 1 (HSPB1, HSP27). HSP27 is an actin-capping protein. Its phosphorylation has been proposed to release it from actin filaments, thus allowing addition of actin monomers and elongation of filaments. Phosphorylation-induced conformational changes causes disaggregation of oligomeric complexes of HSP27 and subsequent disassociation from actin filaments, which may result in a higher rate of actin polymerization (Lamalice et al. 2007, Rousseau et al. 2000, Lavoie et al. 1995).