Heat shock protein 27 (Hsp27) is a molecular chaperone protein which regulates cell apoptosis by interacting directly with the caspase activation components in the apoptotic pathways. With the assistance of the Tat protein transduction domain we directly delivered the Hsp27 into the myocardial cell line, H9c2 and demon-strate that this protein can reverse hypoxia-induced apoptosis of cells. In order to characterize the contribu-tion of Hsp27 in blocking the two major apoptotic pathways operational within cells, we exposed H9c2 cells to staurosporine and cobalt chloride, agents that induce mitochondria-dependent (intrinsic) and -independent (extrinsic) pathways of apoptosis in cells respectively. The Tat-Hsp27 fusion protein showed a greater propensity to inhibit the effect induced by the cobalt chloride treatment. These data suggest that the Hsp27 predominantly exerts its protective effect by interfering with the components of the extrinsic pathway of apop-tosis.

Keywords: apoptosis, cobalt chloride, extrinsic apoptosis, Fas-mediated apoptosis, heat shock protein 27, intrinsic apoptosis, mitochondria-dependent apoptosis, protein transduction domain, staurosporine, Tat peptide