Targeting cytochrome C oxidase in mitochondria with Pt(II)-porphyrins for photodynamic therapy

Abstract

Mitochondria are the power house of living cells, where the synthesis of the chemical "energy currency" adenosine triphosphate (ATP) occurs. Oxidative phosphorylation by a series of membrane protein complexes I to IV, that is, the electron transport chain, is the source of the electrochemical potential difference or proton motive force (PMF) of protons across the inner mitochondrial membrane. The PMF is required for ATP production by complex V of the electron transport chain, i.e. by F o F 1 -ATP synthase. Destroying cytochrome C oxidase (COX; complex IV) in Photodynamic Therapy (PDT) is achieved by the cationic photosensitizer Pt(II)-TMPyP. Electron microscopy revealed the disruption of the mitochondrial christae as a primary step of PDT. Time resolved phosphorescence measurements identified COX as the binding site for Pt(II)-TMPyP in living HeLa cells. As this photosensitizer competed with cytochrome C in binding to COX, destruction of COX might not only disturb ATP synthesis but could expedite the release of cytochrome C to the cytosol inducing apoptosis.

Visualizing Mitochondrial FoF1-ATP Synthase as the Target of the Immunomodulatory Drug Bz-423

“…One identified target was cytochrome C oxidase. This finding could be used to specifically induce photodamage by singlet oxygen as a reactive oxygen species [44][45][46] for Photodynamic Therapy. Beside photoaffinity labeling approaches, time-resolved FRET was applied to reveal that cytochrome C oxidase was a binding site of these lipophilic cationic photosensitizers acting as FRET donors [46,47].…”

“…This finding could be used to specifically induce photodamage by singlet oxygen as a ROS ( Cernay and Zimmermann, 1996 ; Dummin et al, 1997 ; Borsch, 2010 ) for Photodynamic Therapy. Beside photoaffinity labeling approaches, time-resolved FRET was applied to reveal that cytochrome C oxidase was a binding site of these lipophilic cationic photosensitizers acting as FRET donors ( Huglin et al, 1995 ; Borsch, 2010 ). Similarly, confocal imaging FRET donor lifetimes of mitochondrial F o F 1 -ATP synthases in the presence and absence of FRET acceptor-tagged Bz-423 derivatives could be employed to provide direct optical evidence for Bz-423 binding to F o F 1 -ATP synthase.…”

Imaging cytochrome C oxidase and FoF1-ATP synthase in mitochondrial cristae of living human cells by FLIM and superresolution microscopy

“…The IMM is folded into cristae to enlarge the membrane surface area and to optimize ATP production. Imaging mitochondria and the ultrastructure of the cristae with nanometer resolution is achievable by electron microscopy, either by negative staining 1 (Fig. 1a) or by electron cryotomography 2 .…”

“…Figure 1: a, Electron microscopic image of a mitochondrion in a fixed human cell (HeLa cell, negative stain 1 ). The diameter is approximately 500 nm.…”

Observing conformations of single FoF1-ATP synthases in a fast anti-Brownian electrokinetic trap

“…We apply a single-molecule biophysics approach to study the bacterial FoF1-ATP synthase from Escherichia coli (and other membrane transporters 6,17,[39][40][41][42][43][44][45][46][47][48][49][50][51][52] ). The analysis of rotary conformational dynamics of the enzyme is achieved by singlemolecule Förster resonance energy transfer (smFRET).…”