Heat shock protein 70 interacts with nucleolin and inhibits its cleavage, downregulation and apoptosis induced by hydrogen peroxide in myocytes.

Abstract Increasing evidence proved that apoptosis plays a key role in the pathogenesis in a variety of cardiovascular diseases due to the loss of terminally differentiated cardiac myocytes. Nucleolin (C23) is a nucleolar anti-apoptotic protein and can be cleaved and down-regulated during the apoptotic process. It has been demonstrated that heat shock protein 70 (Hsp70) inhibits apoptosis in myocytes. However, the molecular mechanisms of Hsp70 inhibiting apoptosis are, at the present time, not well understood. Here, we report for the first time that oxidative stress induces an interaction between Hsp70 and C23, as a consequence of their interaction, Hsp70 inhibited the cleavage, down-regulation of C23, and apoptosis in myocytes. Hydrogen peroxide (H2O2, 0.5 mmol/L) induced the cleavage and down-regulation of C23, whereas over-expression of Hsp70 inhibited cleavage, down-regulation of C23 and apoptosis in C2C12 myogenic cells. Moreover, C23 regulated apoptosis by affecting the Bcl-2 expression, Cytochrome C (Cyt C) release and activity of Caspase-3. We further observed that C23 over-expression reversed the blockage of Hsp70 antisense oligonucleotides on the protection of Hsp70; and that Hsp70 redistributed into nucleus and interacted with C23 N-terminal via the peptide-binding domain (PBD) after H2O2 exposure. Finally, our results showed that the deletion of Hsp70 PBD blocked the interaction and abolished the protection of Hsp70 against the cleavage and down-regulation of C23 and apoptosis. In a word, we revealed that C23 is a novel binding partner of Hsp70 in the nucleus and their interaction is a novel mechanism by which Hsp70 inhibits apoptosis in myocytes.