The Edges of Pancreatic Islet β Cells Constitute Adhesive and Signaling Microdomains

• Pancreatic β cells meet at sharp angles to form distinct edges
• Murine β cell edges display high levels of F-actin and E-cadherin
• Edges are also enriched in signaling molecules, generating polarized microdomains
• Human β cells show similar edge organization, underscoring functional significance

SummaryPancreatic islet β cells are organized in rosette-like structures around blood vessels and exhibit an artery-to-vein orientation, but they do not display the typical epithelial polarity. It is unclear whether these cells present a functional asymmetry related to their spatial organization. Here, we identify murine β cell edges, the sites at which adjacent cell faces meet at a sharp angle, as surface microdomains of cell-cell adhesion and signaling. The edges are marked by enrichment of F-actin and E-cadherin and are aligned between neighboring cells. The edge organization is E-cadherin contact dependent and correlates with insulin secretion capacity. Edges display elevated levels of glucose transporters and SNAP25 and extend numerous F-actin-rich filopodia. A similar β cell edge organization was observed in human islets. When stimulated, β cell edges exhibit high calcium levels. In view of the functional importance of intra-islet communication, the spatial architecture of their edges may prove fundamental for coordinating physiological insulin secretion.

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