Exocytosis in Islet β-Cells
The development of technologies that allow for live optical imaging of exocytosis from β-cells has greatly improved our understanding of insulin secretion. Two-photon imaging, in particular, has enabled researchers to visualize the exocytosis of large dense-core vesicles (LDCVs) containing insulin from β-cells in intact islets of Langerhans. These studies have revealed that high glucose levels induce two phases of insulin secretion and that this release is dependent upon cytosolic Ca2+ and cAMP. This technology has also made it possible to examine the spatial profile of insulin exocytosis in these tissues and compare that profile with those of other secretory glands. Such studies have led to the discovery of the massive exocytosis of synaptic-like microvesicles (SLMVs) in β-cells. These imaging studies have also helped clarify facets of insulin exocytosis that cannot be properly addressed using the currently available electrophysiological techniques. This chapter provides a concise introduction to the field of optical imaging for those researchers who wish to characterize exocytosis from β-cells in the islets of Langerhans.
KeywordsInsulin secretion Pancreatic islet Sequential exocytosis Two-photon microscopy
This work was supported by Grants-in-Aid from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan and the Global COE Program (Integrative Life Science Based on the Study of Biosignaling Mechanisms) of MEXT.
- Fukui K, Yang Q, Cao Y, Takahashi N, Hatakeyama H, Wang H, Wada J, Zhang Y, Marselli L, Nammo T, Yoneda K, Onishi M, Higashiyama S, Matsuzawa Y, Gonzalez FJ, Weir GC, Kasai H, Shimomura I, Miyagawa J, Wollheim CB, Yamagata K (2005) The HNF-1 target collectrin controls insulin exocytosis by SNARE complex formation. Cell Metab 2:373–384PubMedGoogle Scholar
- In’t VP, Pipeleers DG, Gepts W (1984) Evidence against the presence of tight junctions in normal endocrine pancreas. Diabetes 33:101–104Google Scholar
- Kahn CR (2004) Joslin’s diabetes mellitus. Lippincott Williams & Wilkins, PhiladelphiaGoogle Scholar
- Kasai H, Takagi H, Ninomiya Y, Kishimoto T, Ito K, Yoshida A, Yoshioka T, Miyashita Y (1996) Two components of exocytosis and endocytosis in PC12 cells studied using caged-Ca2+ compounds. J Physiol (Lond) 494:53–65Google Scholar
- Kasai H, Suzuki T, Liu T, Kishimoto T, Takahashi T (2001) Fast and cAMP-sensitive mode of Ca2+-dependent insulin exocytosis in pancreatic β-cells. Diabetes 51:S19–S24Google Scholar
- Kasai H, Hatakeyama H, Kishimoto T, Liu T-T, Nemoto T, Takahashi N (2005a) A new quantitative (two-photon extracellular polar-tracer imaging-based quantification (TEPIQ)) analysis for diameters of exocytic vesicles and its application to mouse pancreatic islets. J Physiol 568:891–903PubMedPubMedCentralGoogle Scholar
- Miura A, Yamagata K, Kakei M, Hatakeyama H, Takahashi N, Fukui K, Nammo T, Yoneda K, Inoue Y, Sladek FM, Magnuson MA, Kasai H, Miyagawa J, Gonzalez FJ, Shimomura I (2006) Hepatocyte nuclear factor-4α is essential for glucose-stimulated insulin secretion by pancreatic β-cells. J Biol Chem 281:5246–5257PubMedGoogle Scholar
- Zhou Z, Misler S (1996) Amperometric detection of quantal secretion from patch-clamped rat pancreatic β-cells. J Biol Chem 270:270–277Google Scholar