Real-Time Intracellular Mg2+ Signaling and Wave Propagation by Subdiffraction-Limit Super-Resolution Microscopy

Magnesium ion (Mg2+) is an important intracellular component that plays a fundamental role in many cellular processes. The super-localization of intracellular Mg2+ signaling and wave propagation in a single cell with subdiffraction-limit image resolution is demonstrated for the first time by direct stochastic optical reconstruction microscopy (dSTORM). Mag-fluo-4-AM, an intracellular Mg2+ fluorescent indicator dye, is used for the fluorescence imaging of intracellular Mg2+ in human embryonic kidney 293 (HEK-293) cells as a model. Mag-fluo-4-AM is photoswitched between its fluorescent and dark states and the resulting super-resolution cell image reveals uniform and specific labeling of Mg2+ with thousands of fluorophores per cell and localization precision of 21 +/- 1nm. Furthermore, the real-time dynamics of Mg2+ wave propagation are studied by dSTORM. The sparks and waves show random temporal propagation patterns in nonhomogeneous substructures with 0.2s time intervals. Thus, dSTORM allows characterization of intracellular processes at sub-nanometre spatial resolution with high temporal resolution.