Alzheimer’s disease (AD) research has primarily focused on amyloid beta (Aβ) and tau protein; however, drug development targeting these two proteins has been disappointing. Therefore, there is an urgent need to explore the novel pathogenic mechanisms underlying AD. Recently, we found that expression of the K670N/M671L-mutated amyloid precursor protein (APP) in 293T cells significantly reduced membrane ferroportin (FPN) levels. Furthermore, 2-month-old APP/PS1 mice exhibited a marked decrease in membrane FPN levels, while total FPN expression and Aβ levels remained unchanged. Further studies revealed that features of ferroptosis were present in the brains of 2-month-old APP/PS1 mice, and that treatment with ferroptosis inhibitors or iron chelation significantly alleviated early pathological changes and cognitive impairment in these animals. In addition, supplementation with an APP–FPN binding peptide during the early phase ameliorated AD-related pathologies, including Aβ deposition, neuroinflammation, oxidative stress, and synapse-associated protein deficits, in APP/PS1 mice. Collectively, our findings suggest that APP mutations may contribute to early brain pathological changes and subsequent memory impairment in AD by downregulating membrane trafficking of FPN and inducing ferroptosis, thereby providing new molecular targets for drug development.

Introduction: Gastric cancer is a prevalent and aggressive malignancy driven by complex signaling networks. Estrogen receptor-α36 (ER-α36), a membrane-localized receptor, mediates non-genomic signaling and promotes tumor progression. ER-α36 can interact with epidermal growth factor receptor (EGFR) to activate downstream mitogen-activated protein kinase (MAPK) signaling, but the detailed mechanism in gastric cancer remains unclear. This study aimed to explore whether ER-α36 promotes gastric cancer progression by regulating serum and glucocorticoid-regulated kinase 1 (SGK1)-mediated Erk1/2 activation.Methods:We collected 53 human gastric adenocarcinoma specimens and detected ER-α36 expression by immunohistochemistry. Bioinformatics analysis was used to identify ER-α36-related kinases. Gastric cancer cell lines (SGC7901, HGC27, NCI-N87, and MFC) were used for in vitro studies. Western blotting, qRT-PCR, immunofluorescence, co-immunoprecipitation (Co-IP), wound healing, MTT, and Transwell invasion analyses, and nude mouse orthotopic tumor models were applied to investigate the function and mechanism of the ER-α36/SGK1/Erk1/2 axis. Results: ER-α36 was positively expressed in 62.3% of gastric adenocarcinoma tissues and was associated with poor differentiation and prognosis. SGK1 was identified as a key kinase downstream of ER-α36. ER-α36, SGK1, and p-Erk1/2 were co-upregulated in gastric cancer tissues and cells. ER-α36 regulated Raf/MEK1/2/Erk1/2 phosphorylation in an SGK1-dependent manner. EGF-induced Erk1/2 activation required both ER-α36 and SGK1. Overexpression of ER-α36 promoted the proliferation, migration, and invasion of gastric cancer cells, while SGK1 knockdown abolished these oncogenic effects. In vivo experiments confirmed that ER-α36 promoted gastric tumor growth and EGFR/Erk signaling, which was attenuated by SGK1 knockdown. Conclusions: ER-α36 contributes to the malignant progression of gastric adenocarcinoma by activating the Erk1/2 pathway through SGK1. The ER-α36–SGK1–Erk1/2 axis may serve as a novel therapeutic target for gastric cancer.