Fig. 1

Organization in pancreas. (A) Pancreas, its compartments and microenvironment. Pancreas has two compartments: Endocrine and exocrine pancreas. Endocrine pancreas contains islets wrapped by peri-islet basement membrane. In islets, 5 different endocrine cells are present: Alpha-cells, beta-cells, delta-cells, epsilon-cells and gamma-cells. Exocrine pancreas is formed by acinar cells and ducts that contain ductal cells and centroacinar cells. In addition, resident-immune system cells and PSCs, as well as nerve fibers are found in the pancreas tissue. The pancreas also accommodates blood vessels. In figure as example, capillaries are shown. In general, capillaries are made of endothelial cells facing the blood and they are covered by pericytes and basement membrane. The acellular part of the pancreas is ECM that is rich in proteins, glycosaminoglycans and proteoglycans. (B) Polarity determinants for beta-cells. Beta-cells express Dlg and scribble in different regions, but their expression is enriched in lateral surfaces. Par3 is abundant in the apical domain away from vasculature. The capillary interface/vascular face is marked with the presynaptic scaffold proteins of liprin, RIM2, ELKS and piccolo. (C) Proteins on beta-cells used to form junctions for cell-cell interactions. ZO-1, claudins and occludin containing tight junctions, connexin-36-based gap junctions provide intercellular communication between beta-cells. Adherens junctions established between beta-cell and beta-cell and, between beta-cell and alpha-cell contain several cadherin family members and N-CAM. Apart from these junctions, EphA receptor tyrosine kinases and their ephrin-A ligands are located on beta-cells and alpha-cells for cellular communication and insulin secretion. Transcellular neuroligin-2 is an important protein of beta-cells to control insulin secretion. Dlg: Discs large protein, ECM: Extracellular matrix, N-CAM: Neural cell adhesion molecule, Par3: Partitioning defective 3 homologue, PSC: Pancreatic stellate cell, RIM2: Rab3-interacting protein. In labeling of endocrine cells for (A), the shapes and sizes of the cell representations are not relevant to the actual morphology and size of the cells. Figure 1 contains images from Servier Medical Art, which were modified in color and size where necessary. Servier Medical Art (smart.servier.com) is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0) (https://creativecommons.org/licenses/by/4.0/)