A water-soluble, cell-permeable Mn(ii) sensor enables visualization of manganese dynamics in live mammalian cells.

Central roles of Mn2+ ions in immunity, brain function, and photosynthesis necessitate probes for tracking this essential metal ion in living systems. However, developing a cell-permeable, fluorescent sensor for selective imaging of Mn2+ ions in the aqueous cellular milieu has remained a challenge. This is because Mn2+ is a weak binder to ligand-scaffolds and Mn2+ ions quench fluorescent dyes leading to turn-off sensors that are not applicable for in vivo imaging. Sensors with a unique combination of Mn2+ selectivity, µM sensitivity, and response in aqueous media are necessary for not only visualizing labile cellular Mn2+ ions live, but also for measuring Mn2+ concentrations in living cells. No sensor has achieved this combination thus far. Here we report a novel, completely water-soluble, reversible, fluorescent turn-on, Mn2+ selective sensor, M4, with a K d of 1.4 µM for Mn2+ ions. M4 entered cells within 15 min of direct incubation and was applied to image Mn2+ ions in living mammalian cells in both confocal fluorescence intensity and lifetime-based set-ups. The probe was able to visualize Mn2+ dynamics in live cells revealing differential Mn2+ localization and uptake dynamics under pathophysiological versus physiological conditions. In a key experiment, we generated an in-cell Mn2+ response curve for the sensor which allowed the measurement of the endogenous labile Mn2+ concentration in HeLa cells as 1.14 ± 0.15 µM. Thus, our computationally designed, selective, sensitive, and cell-permeable sensor with a 620 nM limit of detection for Mn2+ in water provides the first estimate of endogenous labile Mn2+ levels in mammalian cells.

Chromosomal 3q amplicon encodes essential regulators of secretory vesicles that drive secretory addiction in cancer.

Cancer cells exhibit heightened secretory states that drive tumor progression. Here, we identify a chromosome 3q amplicon that serves as a platform for secretory regulation in cancer. The 3q amplicon encodes multiple Golgi-resident proteins, including the scaffold Golgi integral membrane protein 4 (GOLIM4) and the ion channel ATPase Secretory Pathway Ca2+ Transporting 1 (ATP2C1). We show that GOLIM4 recruits ATP2C1 and Golgi phosphoprotein 3 (GOLPH3) to coordinate calcium-dependent cargo loading and Golgi membrane bending and vesicle scission. GOLIM4 depletion disrupts the protein complex, resulting in a secretory blockade that inhibits the progression of 3q-amplified malignancies. In addition to its role as a scaffold, GOLIM4 maintains intracellular manganese (Mn) homeostasis by binding excess Mn in the Golgi lumen, which initiates the routing of Mn-bound GOLIM4 to lysosomes for degradation. We show that Mn treatment inhibits the progression of multiple types of 3q-amplified malignancies by degrading GOLIM4, resulting in a secretory blockade that interrupts pro-survival autocrine loops and attenuates pro-metastatic processes in the tumor microenvironment. Potentially underlying the selective activity of Mn against 3q-amplified malignancies, ATP2C1 co-amplification increases Mn influx into the Golgi lumen, resulting in a more rapid degradation of GOLIM4. These findings show that functional cooperativity between co-amplified genes underlies heightened secretion and a targetable secretory addiction in 3q-amplified malignancies.

An activity-based fluorescent sensor with a penta-coordinate N-donor binding site detects Cu ions in living systems.

An activity-based sensor afforded a 63 times fluorescence-enhancement with Cu2+/Cu+ ions and could image Cu2+/Cu+ in living cells and in a multicellular organism. The sensor functioned only in the presence of ambient dioxygen and glutathione, and the characterization of intermediates and products hinted toward a sensing mechanism involving a CuII hydroperoxo species.

Correction: An activity-based fluorescent sensor with a penta-coordinate N-donor binding site detects Cu ions in living systems.

Correction for 'An activity-based fluorescent sensor with a penta-coordinate N-donor binding site detects Cu ions in living systems' by Kunika Gupta et al., Chem. Commun., 2023, 59, 8282-8285, https://doi.org/10.1039/D3CC02201C.