Intrinsically disordered protein biosensor tracks the physical-chemical effects of osmotic stress on cells

Methods to monitor osmolarity-dependent changes in cell are currently lacking. Here the authors use the Arabidopsis intrinsically disordered AtLEA4-5 protein, which is expressed in plants under water deficit, to develop a FRET biosensor (SED1) to monitor osmotic stress. Cell homeostasis is perturbed when dramatic shifts in the external environment cause the physical-chemical properties inside the cell to change. Experimental approaches for dynamically monitoring these intracellular effects are currently lacking. Here, we leverage the environmental sensitivity and structural plasticity of intrinsically disordered protein regions (IDRs) to develop a FRET biosensor capable of monitoring rapid intracellular changes caused by osmotic stress. The biosensor, named SED1, utilizes the Arabidopsis intrinsically disordered AtLEA4-5 protein expressed in plants under water deficit. Computational modeling and in vitro studies reveal that SED1 is highly sensitive to macromolecular crowding. SED1 exhibits large and near-linear osmolarity-dependent changes in FRET inside living bacteria, yeast, plant, and human cells, demonstrating the broad utility of this tool for studying water-associated stress. This study demonstrates the remarkable ability of IDRs to sense the cellular environment across the tree of life and provides a blueprint for their use as environmentally-responsive molecular tools.

Automated summary

This study introduces a new FRET biosensor, SED1, developed using Arabidopsis intrinsically disordered AtLEA4-5 protein to monitor osmotic stress induced changes in cells. The biosensor demonstrates high sensitivity to osmolarity changes and shows near-linear responses in various living cells, offering a valuable tool for studying water-associated stress. The research highlights the potential of intrinsically disordered protein regions as environmentally-responsive molecular tools across different organisms.