Human heat shock 27-kDa protein 1 (HSPB1)/ heat shock protein (Hsp) 27 is a small heat shock protein which is thought to have several roles within the cell. One of these roles includes regulating actin filament dynamics in cell movement, since Hsp27 has previously been found to inhibit actin polymerization in vitro. In this study, the role of Hsp27 in regulating actin filament dynamics is further investigated. Hsp27 protein levels were reduced using siRNA in SW480 cells, a human colon cancer cell line. An in vitro wound closure assay showed that cells with knocked down Hsp27 levels were unable to close wounds, indicating that this protein is involved in regulating cell motility. Immunoprecipitation pull down assays were done, to observe if and when Hsp27 and actin are in the same complex within the cell, before and after heat shock. At all time points tested, Hsp27 and actin were present in the same cell lysate fraction. Lastly, indirect immunostaining was done before and after heat shock to evaluate Hsp27 and actin interaction in cells. Hsp27 and actin showed colocalization before heat shock, little association 3 h after heat shock, and increased association 24 h after heat shock. Cytoprotection was observed as early as 3 h after heat shock, yet cells were still able to move. These results show that Hsp27 and actin are in the same complex in cells and that Hsp27 is important for cell motility.

Investigations into the possible roles of human HSPB1 in aging have focused on its role as a molecular chaperone protecting partially folded or unfolded proteins, particularly during oxidative stress. A thorough analysis of potential roles of HSPB1 in aging cells has been hampered by a limited knowledge of its functions in living cells. Most studies have employed cell-free extracts and purified proteins. For example, HSPB1 is known to bind actin in vitro, and this observation led to the hypothesis that HSPB1 regulates actin filament dynamics. In the study summarized herein, the role of HSPB1 in regulating actin filament dynamics was further investigated by using cultured human cells. These results show that HSPB1 and actin form a complex in vivo and that HSPB1 is important for cell motility. A model for HSPB1 as a regulator of actin filament dynamics is presented, and evidence from the literature on cytoskeletal alterations in aging cells is discussed.

This meeting review highlights areas of mutual interest to investigators in the cellular stress response field and to those carrying out wound-healing research. Inflammation, perhaps the major unifying theme of this meeting, is an essential component of the adult wound response and understanding the control of inflammation is a common interest shared with researchers of the cellular stress response. The particular interest of the authors of this review is in chronic non-healing wounds that frequently occur in patients with major illnesses such as diabetes and diseases of the blood vessels. This orientation has undoubtedly influenced the selection of topics. It is fair to say that the authors were often surprised and certainly impressed with the overlapping interests and possibilities for collaboration among investigators of these two research areas.

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HSP27 is essential for mammalian cell movement. To further explore the effects of heat shock and the mechanistic role of HSP27, we have initiated a study using a well-established model of rapidly moving cells, the fi sh keratocyte. Here we report that heat shock causes a decrease in cell speed. Since changes in cell morphology can drastically affect cell movement, we also monitored changes in cell morphology. Heat shock caused a decrease in the number of polar cells and an increase in those with one stuck adherent edge, indicating the occurrence of both cytoskeletal re-organization and increased adhesion to substrata. Analyses of HSP27 levels using Western blots showed they were relatively high in keratocytes prior to heat shock and remained high afterward. In contrast, Western blot analysis of HSP70 showed that it was induced strongly by heat shock, indicating that fi sh keratocytes mounted a robust heat shock response. Surprisingly, given the propensity of HSP27 to localize in nuclear/perinuclear regions following heat shock, the location of HSP27 in fi sh keratocytes was unchanged as shown by indirect immunostaining with anti-HSP27 antibodies. Fluorescence intensities of immunostained images of cells before and after heat shock were quantifi ed using Image J software. The results of this analysis showed that fl uorescence intensity decreased following heat shock, suggesting changes in HSP27 that affected antibody recognition. Possible roles for HSP27 in regulating actin fi lament dynamics, cell speed and morphology are discussed.