Distribution of the zinc transporter ZnT‐1 in comparison with chelatable zinc in the mouse brain

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Abstract
Zinc maintains a diverse array of functions in the mammalian central nervous system as a key component of numerous enzymes, via its role in the activation of transcription factors, and as a neuroregulator, modulating neuronal receptors such as N‐methyl‐D‐aspartate and γ‐aminobutyric acid. Zinc has a dark side, however, with massive influx of Zn2+ to neurons considered to be a key factor in neuronal death secondary to ischemia and seizure. Several different putative zinc transporters, ZnT‐1–4, have recently been identified and characterized. Among them, ZnT‐1 has been suggested to play a key role in reducing cellular Zn2+ toxicity. In the present study, we describe the regional and cellular distribution of ZnT‐1 in the adult mouse brain using an antibody raised against the C‐terminal domain of mouse ZnT‐1. The distribution of ZnT‐1 was compared to that of chelatable Zn2+, visualized by means of neoTimm histochemistry or N‐(6‐methoxy‐8‐quinolyl)‐p‐toluene‐sulfonamide (TSQ) histofluorescence. Extracts from various brain regions specifically stained a 60‐kDa peptide corresponding to the expected molecular weight of ZnT‐1. The expression of ZnT‐1 was highest in the cerebral cortex and cerebellum, moderate in the hippocampus, hypothalamus, and olfactory bulb, and lowest in the striatum and septum. In brain sections, ZnT‐1‐immunoreactive neurons, in particular principle neurons, in the somatosensory cortex, hippocampus, and olfactory bulb, were closely related to synaptic Zn2+. Robust ZnT‐1 immunoreactivity was also observed in cerebellar Purkinje cells. Although the function of the protein in these cells is unclear, in the forebrain, ZnT‐1 is strikingly present in cells and regions where significant Zn2+ homeostasis is required. This finding suggests a protective role for neuronal ZnT‐1 in the context of both normal and pathophysiological activity. J. Comp. Neurol. 447:201–209, 2002.