In vivo evaluation of hsp27 as an inhibitor of actin polymerization: Hsp27limits actin stress fiber and focal adhesion formation after heat shock

The role of hsp27 as an inhibitor of actin polymerization was considered in the context of the actin cytoskeleton and its relationship with focal adhe sion formation. The aim of this study was to evaluate the potential effects of hsp27 on focal adhesion formation as a relevant biological consequence of actin stress fiber formation. When hsp27 was overexpressed in stably tra nsfected cells, cell attachment was delayed and recovery of disrupted stres s fibers and focal adhesions was limited. In ROS 17/2.8 cells, heat shock c aused the reversible disruption of stress fibers and focal adhesions. The l oss of stress fibers and focal adhesions was associated with reduced phosph otyrosine on the focal adhesion kinase (FAK). Microinjection of recombinant 6-His hsp27 and phosphorylated 6-His hsp27 was used to demonstrate that no nphosphorylated hsp27 prevented the recovery of stress fibers and focal adh esions. These results provide in vivo evidence that hsp27 acts as an inhibi tor of actin polymerization that can alter cellular interactions with extra cellular environments by perturbation of stress fibers, and subsequently fo cal adhesions. J. Cell. Physiol. 177:575-584, 1998. (C) 1998 Wiley-Liss, In c.