Commentary on paper: Small heat shock proteins and the cytoskeleton: An essential interplay for cell integrity? (Wettstein et al.)

► Effect of small heat shock protein HspB1 on actin polymerization is analyzed. ► Critical analysis of literature indicates that HspB1 is not an actin capping protein. ► Different mechanisms underlying stabilization of F-actin by HspB1 are discussed. ► It is concluded that HspB1 and HspB6 are not genuine actin-binding proteins. The recently published paper by Wettstein et al. (2012) reviews the data of literature dealing with participation of small heat shock proteins (sHsp) in cytoskeleton regulation. Analyzing the effect of sHsp on microfilaments, the authors come to conclusion that depending on phosphorylation HspB1 can function as barbed-end-capping protein and can prevent aggregation of F-actin under stress conditions. The modern data do not confirm all these suggestions. We propose that stabilization effect of HspB1 on microfilaments is due to HspB1 interaction with partially unfolded actin or with genuine actin-binding proteins. In addition, HspB1 can exert its stabilizing effect on F-actin by modulating other elements of the cytoskeleton (intermediate filaments and microtubules) or by controlling homeostasis (for instance, redox state). Without being genuine actin-binding proteins, HspB1 and HspB6 predominantly protect microfilaments via an indirect mechanism that is yet to be characterized.