Identification of irisin receptor in pancreatic beta-cells

Type 2 diabetes (T2D) is characterized by a progressive loss of pancreatic β-cell functional mass, highlighting the need for therapeutic strategies that preserve insulin secretory capacity. Irisin, a myokine induced by physical activity and nutritional cues, has been shown to promote β-cell survival and glucose-stimulated insulin secretion (GSIS); however, the molecular mechanisms underlying its action in pancreatic β-cells remain poorly defined. Here, we investigated the upstream signaling mechanisms mediating irisin action in pancreatic β-cells. Although integrin αV/β5 has been identified as a functional irisin receptor in other tissues, we demonstrate that irisin signaling in pancreatic β-cells is integrin-independent. Irisin failed to activate focal adhesion kinase (FAK), and inhibition or silencing of integrin αV did not impair irisin-induced AKT and CREB activation or its insulinotropic effect. Proteomic and in silico analyses suggested the involvement of intracellular compartments associated with endocytic trafficking. Consistently, we show that irisin undergoes cellular internalization in pancreatic β-cells through a lipid raft-dependent mechanism. Disruption of this pathway markedly reduced irisin uptake, while His-tagged irisin, which is not endocytosed, failed to stimulate insulin secretion, indicating that endocytosis is required for its biological activity. Ligand-receptor capture TriCEPS (LRC-TriCEPS) preliminary experiments further demonstrated that irisin binds the β-cell plasma membrane prior to internalization. Moreover, using LRC-TriCEPS coupled with quantitative mass spectrometry, we identified a restricted set of plasma membrane-associated proteins specifically enriched in irisin-treated samples, including F1M9V7, EPDR1, SCRB1 and LYPA1, suggesting potential candidate components involved in irisin binding and uptake. These results provide a starting point for future studies aimed at defining the molecular machinery underlying irisin internalization and signaling, with potential implications for the development of novel strategies to preserve β-cell function in T2D.