We previously showed that endogenous Mst1 plays an essential role in mediating left ventricular (LV) dysfunction after MI 16. Heart failure is often accompanied by accumulation of damaged proteins and organelles, in the form of aggresomes. Microscopic analyses of the chronic MI mouse heart showed that aggresomes accumulate in the perinucleus of border zone and remote area CMs (Fig. 1a). The aggresomes co-localized with p62/SQSTM1 (p62), a protein known to be degraded by autophagy, suggesting insufficient clearance of aggresomes by autophagy (Fig. 1a). The accumulation of aggresomes and p62 was markedly attenuated in transgenic mice with cardiac-specific overexpression of DN-Mst1 (Tg-DN-Mst1) and Mst1−/− mice, suggesting that endogenous Mst1 negatively affects protein and organelle quality control in post MI hearts (Fig. 1a). Autophagy is activated in the post MI heart, as evidenced by increases in LC3-II (Fig. 1b) and accumulation of GFP-LC3 puncta in the border zone in transgenic mice harboring GFPLC3 (Tg-GFP-LC3)(Fig. 1c). Suppression of Mst1 enhanced the indicators of autophagy in the post MI hearts, suggesting that endogenous Mst1 negatively regulates autophagy (Fig. 1b, c). In order to elucidate the role of autophagy in mediating the protection observed in Tg-DN-Mst1 mice 16, we crossed Tg-DN-Mst1 mice with Beclin1+/− mice. The reduction in both protein aggregation and p62 accumulation observed in Tg-DN-Mst1 mice was reversed and the increase in GFP-LC3 puncta was suppressed in the Beclin1+/−-Tg-DN-Mst1 hearts, indicating suppression of autophagy (Fig. 1a–c and Supplementary Fig. 1a). Furthermore, the suppression of LV remodeling, MI scar contraction, and improved LV function and survival rate observed in Tg-DN-Mst1 mice were all reversed in the Beclin1+/−-Tg-DN-Mst1 mouse hearts (Fig. 1d, e and Supplementary Fig. 1b–d). These results suggest that autophagy plays an important role in mediating the protective effects of Mst1 suppression in the post MI heart.