The type 1 diabetes candidate genes PTPN2 and BACH2 regulate the IFN-α-induced crosstalk between JAK/STAT and MAPKs pathways in human beta cells.

BACKGROUND: Type 1 diabetes (T1D) is a chronic autoimmune disease that leads to the progressive loss of pancreatic beta cells. Interferons (IFNs) contribute to the initiation and amplification of beta cell autoimmunity. STAT1 is the main mediator of IFN signalling but little is known about its complex activation processes and role in the progression of beta cell failure. METHODS: We investigated the IFN-α-stimulated STAT1 pathway from three human beta cell models: EndoC-βH1 cells, iPSC-derived islet-like cells and human islets by directly targeting two T1D candidate genes, namely PTPN2 and BACH2. FINDINGS: We presently show that PTPN2 and BACH2 modulate STAT1 activation via two different pathways, namely the JAK/STAT, involved in the phosphorylation of its tyrosine residue (Y701), and the MAPKs pathway, involved in the phosphorylation of its serine residue (S727). Each STAT1 phosphorylation type can independently induce expression of CXCL10, but both residues are necessary for the expression of MHC class I molecules. IFN-α-induced STAT1 activation is dynamic and residue-dependent, being STAT1-Y701 fast but transitory, while STAT1-S727 increases slowly and is associated with the long-term effects of IFN-α exposure. INTERPRETATION: The present findings provide a better understanding of the dynamics of STAT1 activation in human beta cells and will be useful to develop new and targeted (i.e. favouring individuals with particular polymorphisms) therapies for T1D and other autoimmune diseases. FUNDING: EFSD and Sanofi European Diabetes Research Programme on autoimmunity in type 1 diabetes; Breakthrough T1D, HIRN-CBDS, NIDDK, Fondation Saint-Luc, Programme d'Investissement d'Avenir' to European Genomic Institute for Diabetes, and Fondation de la Recherche Médicale.