Pim-2 protects H9c2 cardiomyocytes from hypoxia/reoxygenation-induced apoptosis via downregulation of Bim expression

- H/R augments the apoptosis of H9c2 cells and upregulates Bim, Pim-2 expression.
- Overexpression of Pim-2 attenuates H/R-induced apoptosis via downregulation of Bim.
- Co-IP shows the interaction between Pim-2 and Bim protein.
- Blocking proteasome activity by MG132 prevents the degradation of Bim.
- Mutation of Bim S65A recovered its pro-apoptotic potential.

We know that silencing Bim, a pro-apoptosis protein, significantly attenuates glucose and oxygen-deprived induced apoptosis in cardiomyocytes. However, the mechanisms underlying the regulation of the Bim activation in the heart have remained unknown. Pim-2 is one of three Pim serine/threonine kinase family members thought to be involved in cell survival and proliferation. H9c2 cardiomyocytes were subjected to a hypoxia/reoxygenation (H/R) condition in vitro, mimicking ischemic/reperfusion injury in vivo. H/R augmented the expression of Bim, Cyt C, and Pim-2 and induced H9c2 cell apoptosis. Overexpression of Pim-2 attenuated apoptosis which induced by H/R in H9c2 cells, via downregulation of Bim and Cyt C expression. Silencing of Pim-2 promoted H/R-induced apoptosis via upregulation of Bim and Cyt C expression. Co-IP revealed the interaction between Pim-2 and Bim protein, with Bim Ser65 phosphorylated by Pim-2. Furthermore, blocking proteasome activity by MG132 prevented Bim degradation, and Bim S65A mutation could reverse the anti-apoptotic role of Pim-2 which induced by H/R. These data demonstrated that Pim-2 is a novel Bim-interacting protein, which negatively regulates Bim degradation and protects H9c2 cardiomyocytes from H/R-induced apoptosis.