Divalent Metal Transporter 1 Knock-Down Modulates IL-1β Mediated Pancreatic Beta-Cell Pro-Apoptotic Signaling Pathways through the Autophagic Machinery

Pro-inflammatory cytokines promote cellular iron-import through enhanced divalent metal transporter-1 (DMT1) expression in pancreatic beta-cells, consequently cell death. Inhibition of beta-cell iron-import by DMT1 silencing protects against apoptosis in animal models of diabetes. However, how alterations of signaling networks contribute to the protective action of DMT1 knock-down is unknown. Here, we performed phosphoproteomics using our sequential enrichment strategy of mRNA, protein, and phosphopeptides, which enabled us to explore the concurrent molecular events in the same set of wildtype and DMT1-silenced beta-cells during IL-1 beta exposure. Our findings reveal new phosphosites in the IL-1 beta-induced proteins that are clearly reverted by DMT1 silencing towards their steady-state levels. We validated the levels of five novel phosphosites of the potential protective proteins using parallel reaction monitoring. We also confirmed the inactivation of autophagic flux that may be relevant for cell survival induced by DMT1 silencing during IL-1 beta exposure. Additionally, the potential protective proteins induced by DMT1 silencing were related to insulin secretion that may lead to improving beta-cell functions upon exposure to IL-1 beta. This global profiling has shed light on the signal transduction pathways driving the protection against inflammation-induced cell death in beta-cells after DMT1 silencing.

Automated summary

Pro-inflammatory cytokines promote iron-import in pancreatic beta-cells through upregulation of divalent metal transporter-1 (DMT1), leading to cell death. Silencing of DMT1 protects against apoptosis in diabetes animal models by reversing IL-1 beta-induced phosphosites levels and inactivating autophagic flux, potentially improving beta-cell functions. This study sheds light on the signal transduction pathways involved in protecting beta-cells against inflammation-induced cell death after DMT1 silencing.