Abstract 13768: Pim-1 Preserves Mitochondrial Morphology by Inhibiting Drp1 Translocation
Rationale: Mitochondrial morphologic dynamics affect cardiac ischemic injury. Dynamin Related Protein 1 (Drp1) mediates mitochondrial fission with mitochondrial localization during pathological challenge sensitizing cardiomyocytes to apoptosis. Therefore, Drp1 inhibition promotes reticular mitochondrial networks that may contribute to cardioprotection, but mechanisms regulating Drp1 are poorly understood. Since Pim1 kinase maintains mitochondrial integrity, the relationship between Pim1 and Drp1 was assessed as a novel mechanism to prevent Drp1 mediated mitochondrial fission.
Objective: Demonstrate Pim1 inhibits mitochondrial Drp1 translocation.
Methods and Results: Simulated ischemia (sI) and sI/reperfusion (sI/R) induced mitochondrial fragmentation with Drp1 translocation to mitochondria in neonatal rat cardiomyocytes (NRCM). Pharmacologic inhibition of Drp1 by mdivi1 preserved mitochondrial reticular morphology and inhibited apoptosis. Mice subjected to sI/R injury displayed Drp1 mitochondrial localization, while exposure to mdivi1 reduced infarct size. Overexpressing Pim1 decreased total Drp1 levels, increased phosphorylation of Drp1 at serine 637, and inhibited Drp1 localization to mitochondria while preserving reticular morphology after sI. Pim1 interacts directly with Drp1 in either immunoprecipitation or proximity ligation assays. Overexpression of Pim1 dominant negative (PDN) increased total mitochondrial Drp1, reduced phospho Drp1, and increased mitochondrial fragmentation. PDN hearts exhibit upregulation of BH3 only protein PUMA that mediates mitochondrial Drp1 accumulation and increases sensitivity to apoptotic stimuli. Combined Puma dominant negative and PDN overexpression in NRCM attenuated mitochondrial localization of Drp1 and inhibited cell death following sI.
Conclusion: Pim1 prevents Drp1 compartmentalization to mitochondria and preserves reticular network structure in response to sI. The molecular mechanism of Pim-1 mediated preservation of mitochondrial integrity operates, in part, through inhibition of Drp1 to promote cardioprotection.
- © 2012 by American Heart Association, Inc.