Live-cell dynamic sensing of Cd(2+) with a FRET-based indicator

Area of Science:

• Biochemistry
• Cell Biology
• Toxicology

Background:

• Cadmium (Cd2+) is a toxic heavy metal causing significant human tissue damage.
• While toxicological mechanisms are known, cadmium's cellular entry and sequestration remain incompletely understood.

Purpose of the Study:

• To develop a novel biosensor for real-time monitoring of intracellular cadmium (Cd2+) levels.
• To investigate cadmium entry pathways and sub-cellular distribution in human cells.

Main Methods:

• Construction of Met-cad 1.57, a FRET-based Cd2+ indicator utilizing a bacterial cadmium-binding protein.
• Generation of a human embryonic kidney cell line (HEK-MCD157) stably expressing the Met-cad 1.57 indicator.
• Application of fluorescence spectroscopy and FRET microscopy to quantify intracellular Cd2+ concentrations.

Main Results:

• The Met-cad 1.57 indicator demonstrated a dissociation constant of approximately 271 nM.
• Confirmed the role of calcium (Ca2+) channels as a cadmium entry pathway in HEK-MCD157 cells.
• Observed and visualized cadmium accumulation within the nucleus using the organelle-targeted indicator.

Conclusions:

• A stable human cell line expressing a FRET-based cadmium indicator (Met-cad 1.57) was successfully created.
• This system provides a reliable method for investigating intracellular cadmium dynamics, including entry and sequestration.
• The study identified calcium channels as a key cadmium entry route and revealed nuclear accumulation of cadmium.