Primary cilia regulate GLP-1 signaling in pancreatic β cells

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are mainstay therapies for diabetes and obesity, acting in part by enhancing glucose-dependent insulin secretion. While the primary cilium is a known signaling compartment for certain G-protein coupled receptors (GPCRs), its role in the β-cell response to incretins remains undefined. Here, we show that primary cilia are essential for full GLP-1R signaling. Loss of β-cell cilia in mouse and human islets severely impaired GLP-1-potentiated insulin secretion, an effect preceded by blunted whole-cell cAMP and Ca 2+ responses. Immunofluorescence and immunogold scanning electron microscopy revealed endogenous GLP-1R localized to the primary cilium. Adenylyl cyclase immunostaining was also enriched within cilia, and targeted inhibition of ciliary PKA reduced insulin secretion. Critically, disrupting ciliary GPCR trafficking via Tulp3 knockdown – while preserving cilia structure – recapitulated the signaling and secretory deficits, demonstrating a specific requirement for the ciliary receptor pool. These findings establish the primary cilium as a non-redundant signaling compartment for GLP-1R and uncover a new layer of subcellular organization in incretin action in β cells. • The GLP-1 receptor (GLP-1R) localizes to the primary cilium in pancreatic β-cells. • Primary cilia are required for full GLP-1R-mediated cAMP/Ca 2+ signaling and insulin secretion. • Selective disruption of ciliary GLP-1R impairs incretin responses, independent of cilia structure. • The primary cilium functions as a non-redundant signaling compartment essential for GLP-1R action.