Construing the communication between powerhouse and ribosomal factory of cell: A small molecular viscometer comes to the rescue

Fluorescent probes for specific inter-organelle communication are of massive significance as such communication is essential for a diverse range of cellular events. Here, we present the microviscosity-sensitive fluorescence marker, Quinaldine red (QR), and its dual organelle targeting light-up response in live cells. This biocompatible probe was able to localize in mitochondria and nucleolus simultaneously. While QR was able to sense the viscosity change inside these compartments under the induced effect of an ionophore and ROS-rich microenvironment, the probe’s ability to stain mitochondria remained unperturbed even after protonophore-induced depolarization. Consequently, a systematic quantification was performed to understand the alteration of microviscosity. Similar behavior in two distinct organelles implied that QR binds to Metaxin-2 protein, common to mitochondrial and nucleolar proteomes. We believe this is the first of its kind investigation that identifies the inter-organelle communications marker and opens up a new dimension in this field.