Trained immunity, induced by β-glucan in monocytes, is mediated by activating metabolic pathways that result in epigenetic rewiring of cellular functional programs; however, molecular mechanisms underlying these changes remain unclear. Here, we report a key immunometabolic and epigenetic pathway mediated by the miR–9-5p -isocitrate dehydrogenase 3α (IDH3α) axis in trained immunity. We found that β-glucan–trained miR–9-5p ^–/– monocytes showed decreased IL-1β, IL-6, and TNF-α production after LPS stimulation. Trained miR–9-5p ^–/– mice produced decreased levels of proinflammatory cytokines upon rechallenge in vivo and had worse protection against Candida albicans infection. miR–9-5p targeted IDH3α and reduced α-ketoglutarate (α-KG) levels to stabilize HIF-1α, which promoted glycolysis. Accumulating succinate and fumarate via miR–9-5p action integrated immunometabolic circuits to induce histone modifications by inhibiting KDM5 demethylases. β-Glucan–trained monocytes exhibited low IDH3α levels, and IDH3α overexpression blocked the induction of trained immunity by monocytes. Monocytes with IDH3α variants from autosomal recessive retinitis pigmentosa patients showed a trained immunity phenotype at immunometabolic and epigenetic levels. These findings suggest that miR–9-5p and IDH3α act as critical metabolic and epigenetic switches in trained immunity.

To successfully metastasize, cancer cells must evade detachment induced cell death, known as anoikis. Unraveling the mechanisms that gastric cancer (GC) circumvent anoikis and achieve peritoneal metastasis especially during unanchored growth, could significantly improve patient outcomes. Our study reveals that GC cells exhibit increased lipid peroxidation, MDA production, and cell death during suspension culture, which can be mitigated by the intervention with liproxstatin-1 and ferrostatin-1. We discovered that oleic acid (OA) or adipocytes stimulate lipid accumulation in GC cells, thereby inhibiting lipid peroxidation and cell death. Lipid mass spectrometry confirmed an upregulation of triglyceride synthesis, indicating that the accumulation of lipid droplet may confer resistance to ferroptosis during suspension growth. In vitro assays demonstrated that OA not only induces lipid droplet accumulation but also upregulates the expression of ferroptosis suppressor protein 1 (FSP1), a process that can be abrogated by the double knockout of GPD1/1L genes. Additionally, we have demonstrated that a decrease in the ubiquitination of FSP1 in GC cells upon lipid droplet accumulation, as well as silencing or pharmacological targeting FSP1, promotes ferroptosis and disrupts the peritoneal metastatic potential of GC cells. Collectively, our findings highlight the potential of FSP1 as a promising therapeutic target for metastatic gastric cancer.

The voltage-gated potassium channel Kv1.4 is an important A-type potassium channel and modulates the excitability of neurons in central nervous system. Analysis of the interaction between Kv1.4 and its interacting proteins is helpful to elucidate the function and mechanism of the channel. In the present research, synaptotagmin I was for the first time demonstrated to be an interacting protein of Kv1.4 and its interaction with Kv1.4 channel did not require the mediation of other synaptic proteins. Using patch-clamp technique, synaptotagmin I was found to delay the inactivation of Kv1.4 in HEK293T cells in a Ca²⁺-dependent manner, and this interaction was proven to have specificity. Mutagenesis experiments indicated that synaptotagmin I interacted with the N-terminus of Kv1.4 and thus delayed its N-type fast inactivation. These data suggest that synaptotagmin I is an interacting protein of Kv1.4 channel and, as a negative modulator, may play an important role in regulating neuronal excitability and synaptic efficacy.