N-propargylputrescine as a minimal-tag probe for imaging putrescine dynamics in cellular homeostasis and stress.

Polyamines regulate multiple cellular pathways, and their intracellular availability is controlled in part by transport. We developed imaging putrescine (iPUT), a clickable putrescine analog expected to retain key properties of native putrescine and enable bio-orthogonal fluorophore conjugation for high-resolution imaging. In MCF-7 cells, iPUT accumulated predominantly in nuclei, unlike the directly fluorophore-conjugated probe BODIPY-PUT, highlighting the value of minimal tagging. In hippocampal co-cultures, iPUT accumulated predominantly in neurons. Neuronal labeling was also more frequent than astrocytic labeling in acute hippocampal slices, contrasting with reported glial storage of spermidine and spermine. Subcellular distribution differed across models, with nuclear enrichment in dividing MCF-7 and predominantly extranuclear localization in mature neurons in hippocampal slices. Mimetic hypoxia and excitotoxicity reduced iPUT accumulation in CA1 but not in CA2/3 neurons, and promoted nuclear redistribution in CA1. Thus, iPUT enables investigation of cell-, region-, and stress-dependent putrescine handling.