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

TL;DR

This study uses FLIM and superresolution microscopy to visualize and analyze the localization and environment of cytochrome C oxidase and FoF1-ATP synthase in the mitochondrial cristae of living human cells, revealing distinct nano-environmental properties.

Contribution

It is the first to combine FLIM and superresolution microscopy to study complex IV and V in live cells, providing new insights into their spatial distribution and local environment.

Findings

Different lifetimes and anisotropy values for the enzymes were observed.

FoF1-ATP synthases are mainly at cristae rims, while cytochrome C oxidases are in planar membrane areas.

Distinct nano-environmental properties of the enzymes were characterized.

Abstract

Cytochrome C oxidase and FoF1-ATP synthase constitute complex IV and V, respectively, of the five membrane-bound enzymes in mitochondria comprising the respiratory chain. These enzymes are located in the inner mitochondrial membrane (IMM), which exhibits large invaginations called cristae. According to recent cryo-tomography, FoF1-ATP synthases are located predominantly at the rim of the cristae, while cytochrome C oxidases are likely distributed in planar membrane areas of the cristae. Previous FLIM measurements (K. Busch and coworkers) of complex II and III unravelled differences in the local environment of the membrane enzymes in the cristae. Here, we tagged complex IV and V with mNeonGreen and investigated their mitochondrial nano-environment by FLIM and superresolution microscopy in living human cells. Different lifetimes and anisotropy values were found and will be discussed.