PUMA is critical for neonatal cardiomyocyte apoptosis induced by endoplasmic reticulum stress.

Objective: Puma (p53-upregulated modulator of apoptosis), a proapoptotic BH3-only member of the Bcl-2 protein family, has been implicated in the pathomechanism of several diseases, including cancer, AIDS, and ischemic brain disease. We have recently shown that Puma is required for cardiac cell death upon ischemia/reperfusion of mouse hearts. Since ischemia/reperfusion is also associated with endoplasmic reticulum (ER) stress, in the present study we investigated whether Puma contributes to the ER stress-dependent component of cardiomyocyte apoptosis.

Targeted deletion of Puma attenuates cardiomyocyte death and improves cardiac function during ischemia-reperfusion.

The p53-upregulated modulator of apoptosis (Puma), a BH3-only member of the Bcl-2 protein family, is required for p53-dependent and -independent forms of apoptosis and has been implicated in the pathomechanism of several diseases, including cancer, acquired immunodeficiency syndrome, and ischemic brain disease. The role of Puma in cardiomyocyte death, however, has not been analyzed. On the basis of the ability of Puma to integrate diverse cell death stimuli, we hypothesized that Puma might be critical for cardiomyocyte death upon ischemia-reperfusion (I/R) of the heart.

Differential regulation of cardiomyocyte survival and hypertrophy by MDM2, an E3 ubiquitin ligase.

MDM2 is an E3 ubiquitin ligase that regulates the proteasomal degradation and activity of proteins involved in cell growth and apoptosis, including the tumor suppressors p53 and retinoblastoma and the transcription factor E2F1. Although the effect of several MDM2 targets on cardiomyocyte survival and hypertrophy has already been investigated, the role of MDM2 in these processes has not yet been established. We have, therefore, analyzed the effect of overexpression as well as inhibition of MDM2 on cardiac ischemia/reperfusion injury and hypertrophy.