Abstract 1231: Competitive Displacement of A Kinase Anchor Protein 121 From Mitochondria Triggers DNA Damage And Lowers Tolerance to Oxidative Stress in Muscle Cells
cAMP signals are locally amplified by scaffold proteins (A Kinase Anchor Proteins, AKAPs) that tether cAMP-dependent Protein Kinase A (PKA) to discrete cellular locations. Here we hypothesized that mitochondrial anchoring of PKA promotes survival in muscle cells. We identified AKAP121 as the major mitochondrial AKAP in cardiomyocytes and aortic smooth muscle cells. In response to pressure overload, cardiac AKAP121 levels were significantly reduced, inducing marked mitochondrial dysfunction, DNA damage and activation of the DNA repair machinery. To test the role of AKAP121 in the modulation of cell survival, we synthesized peptides (AK-in) containing AKAP121 mitochondrial targeting domain but lacking its PKA binding motif, in order to competitively displace the endogenous AKAP121/PKA complex from mitochondria. Sequence-scrambled peptides were synthetized and used as controls (S). 24 hours after administration, FITC-conjugated AK-in peptides co-localized with mitochondria at confocal microscopy; in the same cells, AKAP121 mitochondrial targeting was reduced. AKAP121 displacement significantly reduced mitochondrial ATP synthesis and promoted nuclear DNA damage. Interestingly, pre-treatment with Ak-in peptides markedly reduced the tolerance to oxidative stress of smooth muscle cells (Figure⇓). These results suggest that AKAP121 plays a protective role in muscle cells and its downregulation might be involved in the progression from hypertrophy towards heart failure. Furthermore, our strategy of displacing AKAP121 from mitochondria might be a novel tool to prevent deregulated smooth muscle cell proliferation in restenosis or atherosclerosclerosis.