A dual-labeling probe to track functional mitochondria\u2013lysosome interactions in live cells

Qixin Chen,Hongbao Fang,Xiaohe Tian,Zijian Guo,Yuming Zhang,Huaxun Fan,Pan Xiang,Shanshan Geng,Xintian Shao,Kai Zhang,Jiajie Diao,Weijiang He,Jie Zhang,Zhiqi Tian

doi:10.1038/s41467-020-20067-6

Abstract

Mitochondria–lysosome interactions are essential for maintaining intracellular homeostasis. Although various fluorescent probes have been developed to visualize such interactions, they remain unable to label mitochondria and lysosomes simultaneously and dynamically track their interaction. Here, we introduce a cell-permeable, biocompatible, viscosity-responsive, small organic molecular probe, Coupa, to monitor the interaction of mitochondria and lysosomes in living cells. Through a functional fluorescence conversion, Coupa can simultaneously label mitochondria with blue fluorescence and lysosomes with red fluorescence, and the correlation between the red–blue fluorescence intensity indicates the progress of mitochondria–lysosome interplay during mitophagy. Moreover, because its fluorescence is sensitive to viscosity, Coupa allowed us to precisely localize sites of mitochondria–lysosome contact and reveal increases in local viscosity on mitochondria associated with mitochondria–lysosome contact. Thus, our probe represents an attractive tool for the localization and dynamic tracking of functional mitochondria–lysosome interactions in living cells.

Highlights

Mitochondria–lysosome interactions are essential for maintaining intracellular homeostasis
Their indolenium positive charge may target them to mitochondria if they are suitably N-substituted on indolium
We developed Coupa, a dual-labeling probe enabling the simultaneous labeling of mitochondria and lysosomes in living cells through functional fluorescence conversion

Summary

Introduction

Mitochondria–lysosome interactions are essential for maintaining intracellular homeostasis. Through a functional fluorescence conversion, Coupa can simultaneously label mitochondria with blue fluorescence and lysosomes with red fluorescence, and the correlation between the red–blue fluorescence intensity indicates the progress of mitochondria–lysosome interplay during mitophagy. At least two fluorescent probes with different emission spectra—small-molecule dyes[3] or fluorescent proteins2-are needed to monitor mitochondria–lysosome interplay Those probes indicate only co-localization and cannot effectively track the dynamic changes of mitochondria–lysosome functional interactions, which are so valuable to understand cellular responses to stimulations and local environmental variations. To address this problem, we developed a small-molecule fluorescent probe of hemicyanine containing propionic acid (Coupa, Fig. 1) with specific organelle targeting ability and functional fluorescence conversion capabilities. Non-toxicity, and excellent photobleaching resistance, Coupa will offer new insights into the dynamic nature of mitochondria–lysosome interactions in living cells

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Results

Conclusion