| Mitochondria are organelles with critical roles in key processes within eukaryotic cells, and their dysfunction is linked with numerous diseases including neurodegenerative disorders and cancer. Pharmacological manipulation of mitochondrial function is therefore important both for basic science research and eventually, clinical medicine. However, in comparison to other organelles, mitochondria are difficult to access due to their hydrophobic and dense double membrane system as well as their negative membrane potential.;To tackle the challenge of targeting these important subcellular compartments, we have developed peptide-based vectors in order to deliver therapeutic agents and probes to mitochondria. Interestingly, mitochondria-targeted DNA damaging agents demonstrate high potency and the ability to evade resistance mechanisms and off-target effects. In this thesis, we demonstrated that we can control the biological activity of these mitochondria-targeted DNA damaging agents via structural modification. In a related study, a mitochondria-targeted anticancer drug has been used to probe and eliminate secondary effects of the untargeted parent compound in healthy and disease-relevant cellular and animal models. Interestingly, analysis of the targeted drug's activity in healthy and xenograft mice revealed that mitochondria-targeting can served as a promising approach to enhancing the therapeutic window. Moreover, a combination of these mitochondria-targeted DNA damaging agents was applied to an siRNA screen for the elucidation of poorly understood mitochondrial DNA repair and replication pathways. Significantly, multiple proteins were identified that are essential for the maintenance of mitochondrial nucleic acids including a new DNA polymerase (POLtheta).;This thesis outlines the various ways to probe and manipulate mitochondrial biology for basic scientific studies and clinical applications. Nevertheless, the mitochondrial targeting field is quite nascent and many exciting applications of organelle-specific conjugates remain to be explored. |
