In biomedicine, studies on dynamic interactions between mitochondria and lysosomes are critical for understanding cellular metabolism and disease mechanisms. Yet, the interaction mechanism on the molecular level is still unclear due to a lack of suitable investigation tools. Here, we employ a synergistic microscopic platform that integrates quantitative phase contrast microscopy (QPCM), confocal fluorescent imaging, line-scanning fluorescence resonance energy transfer (ls-FRET), and line-scanning fluorescence correlation spectroscopy (ls-FCS) to reveal the mechanism of biomolecular interaction on mitochondria-lysosome contact membranes. Using ls-FRET, we quantified the FRET efficiency between (Rab7A) donors and (TOM20) acceptors situated in the mitochondrial-lysosomal contact membrane. It is found that FRET efficiency decreases under carbonyl cyanide m-chlorophenyl hydrazone (CCCP) treatment. The joint use of QPCM and ls-FCS elucidates the underlying mechanism behind the reduction of FRET efficiency. The above multi-modality imaging platform enables simultaneous mapping of molecular interactions and dynamics on subcellular membranes in living cells, offering multidimensional and complementary optical readouts.
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