Nuclear accumulation of PANK4 in hippocampal astrocytes aggravates cuproptosis in association with mild cognitive impairment in aged mice.

BACKGROUND: Mild cognitive impairment (MCI), a condition that falls somewhere between normal aging and severe cognitive dysfunction (e.g., Alzheimer's disease), is a common manifestation of the neurocognitive function decline that seniors encounter as they age. The fundamental processes causing its beginning are still not well understood yet. METHODS: We employed aged (18-month-old) male C57BL/6J mice, including astrocyte-specific Pantothenate kinases 4 (PANK4) conditional knockout (Pank4 f/f ;Gfap-Cre, Pank4-CKO) mice. Cognitive function was assessed using the Barnes maze, Y-maze (spatial novelty preference, spontaneous alternation), novel object recognition (NOR) test, and open field test (OFT). Hippocampal PANK4 localization was analyzed via immunofluorescence (IF) and subcellular fractionation/western blotting (WB). Cuproptosis markers (FDX1, LIAS, DLAT), copper transporters (ATP7A, ATP7B, SLC31A1), and copper content (ICP-MS) were quantified in hippocampal tissue. In vitro studies used LPS-stimulated primary astrocytes for RNA-seq and qPCR validation. RESULTS: Aged wild-type (18M+WT) mice exhibited specific deficits in Barnes maze retention and reversal learning, indicative of mild cognitive impairment, while Pank4-CKO mice showed significant rescue. We discovered a novel age-dependent nuclear accumulation of PANK4 in hippocampal cells, which was absent in Pank4-CKO mice. Aged hippocampi displayed upregulated pro-cuproptotic factors (FDX1, LIAS) and reduced DLAT, alongside decreased expression of the copper exporter ATP7A, ATP7B, SLC31A1 and increased copper accumulation. Astrocyte-specific Pank4 knockout reversed these changes: it suppressed FDX1/LIAS upregulation, restored ATP7B expression and DLAT levels, and normalized hippocampal copper content. In vitro, LPS-induced neuroinflammation triggered PANK4 nuclear translocation and selectively downregulated Atp7b expression in astrocytes. Small interfering RNA (siRNA)-mediated knockdown of Pank4 significantly upregulated Atp7b expression. CONCLUSION: This study identifies a novel pathological mechanism in age-related MCI: the nuclear accumulation of PANK4 in hippocampal exacerbates cuproptosis susceptibility by specifically impairing ATP7B-dependent copper efflux, leading to copper overload. Astrocyte-specific PANK4 ablation mitigates these effects, highlighting PANK4 as a potential therapeutic target for preventing or treating age-associated cognitive decline.