An Alkyne-Directed Cleavage Approach for Activity-Based Cu(I) Sensing Reveals Manganese-Promoted Sensitization of Cuproptosis

Copper is an essential element for sustaining life. However, disruptions in copper homeostasis underpin disease, as illustrated by cuproptosis, an emerging form of cell death resulting from aberrant accumulation of copper pools in loosely bound, labile forms. Along these lines, activity-based sensing (ABS) offers a powerful strategy for tracking labile copper fluxes with metal and oxidation state selectivity by exploiting analyte reactivity for analyte detection. Traditional ABS probes for Cu(I), the major oxidation state of copper in cells, are selective but require O₂ as a coadditive, thus limiting their temporal resolution and sensitivity. Here, we present the design, synthesis, and biological evaluation of a first-generation ABS strategy for direct Cu(I) sensing by leveraging alkyne-directed cleavage reactivity. Copper Alkyne Probe-1 (CAP-1) features a rapid response to changes in intracellular Cu(I) pools with over 400-fold selectivity for Cu(I) over competing biological metals. We apply this probe to identify novel metal-metal crosstalk in cuproptosis, where we observe that Mn(II) exposure sensitizes cells to cuproptosis through upregulating the mitochondrial reductase FDX1 and depleting reduced glutathione, thus synergistically elevating labile Cu(I) levels. By revealing an interplay between copper and manganese in regulating cell death, this work provides a starting point for broader investigations of metal-metal nutrient crosstalk in biology and medicine.