Zinc and copper play roles in neuronal synaptic functions, particularly in synaptogenesis and synaptic plasticity, but the molecular mechanisms are not fully understood. Due to low metal concentrations and sub-micron size of synaptic compartments, studying these roles is challenging. To address this, we developed a correlative nano-imaging approach that combines protein and metal detection. We used STED (stimulated emission depletion) super resolution microscopy to locate fluorescently labeled proteins and SXRF (synchrotron radiation X-ray fluorescence) for high-resolution imaging of metals in the same regions, to study the distribution of zinc and copper in synaptic compartments of primary rat hippocampal neurons. We found that zinc interacts with tubulin in dendrites and axons, is present in the postsynaptic density, and copper co-localizes with F-actin in synaptic compartments. Quantitative immunofluorescence data confirmed these interactions, showing that zinc affects tubulin expression and copper affects F-actin structures. Our results suggest that zinc is essential for the formation of the cytoskeletal structure in neurons, while copper plays a role in synaptic plasticity, key for memory processing.

SLC30A10 deficiency is a disease of severe manganese excess attributed to loss of SLC30A10-dependent manganese excretion via the gastrointestinal tract. Patients develop dystonia, cirrhosis, and polycythemia. They are treated with chelators but also respond to oral iron, suggesting that iron can outcompete manganese for absorption in this disease. While SLC11A2 (DMT1) and SLC40A1 (ferroportin) are essential for dietary iron absorption, their role in manganese homeostasis is debated. In this study, we explore potential overlaps in manganese and iron absorption in Slc30a10-deficient mice. We first establish that manganese absorption is paradoxically increased in Slc30a10-deficient mice despite manganese excess. We next show that intestinal deficiency in Dmt1 or ferroportin not only attenuates aberrant manganese absorption but also prominently decreases manganese levels in Slc30a10-deficient mice. Finally, we demonstrate that intestinal Slc30a10 deficiency is a key driver of aberrant Mn absorption, as it impairs manganese export from enterocytes back into the gastrointestinal tract. Our work demonstrates that aberrant absorption contributes prominently to SLC30A10 deficiency, a disease previously attributed solely to impaired excretion, and expands our understanding of biological interactions between iron and manganese. Based on these results, we propose a reconsideration of the role of iron transporters in manganese homeostasis is warranted.