Visualization of long-term Mg dynamics in apoptotic cells using a novel targetable fluorescent probe.

Mg plays important roles in many physiological processes. However, the underlying molecular mechanisms, especially in the apoptotic pathway, remain unclear due to the diffusion of Mg probes, which hinders long-term imaging in specific organelles. We developed an immobilized Mg probe, MGH, which is covalently conjugated with the HaloTag protein in various organelles. HaloTag-coupled MGH enabled long-term imaging of intracellular local Mg dynamics for 24 h. To exploit this remarkable property, MGH was applied to the investigation of intracellular Mg dynamics during apoptosis. Time-lapse imaging revealed an increase in the Mg concentration after apoptotic cell shrinkage. Combined imaging analyses of intracellular Mg and ATP concentrations strongly suggested that this Mg concentration increase was caused by the dissociation of Mg from ATP, along with a decrease in the intracellular ATP concentration. Thus, this protein-coupled Mg probe could be a new chemical tool to elucidate intracellular Mg dynamics with high spatiotemporal resolution.