All cells undergo some base level of secretion, but there are many cell types with specialized “regulated” secretion. For example, our endocrine cells secrete the hormones that regulate our bodies and throw teenagers into crazed states. Cells with regulated secretion store high concentrations of certain proteins in dense organelles called secretory granules, until there is a signal that triggers the release of these proteins. A recent paper asks how secretory granules are formed, and finds that two vesicle coat proteins, called AP-1 and clathrin, are required. Burgess and colleagues looked at secretory granules in larval fruit fly salivary glands, and found that AP1 and clathrin are localized at newly synthesized secretory proteins, Golgi structures (where the proteins are sorted), and maturing secretory granules. Images show salivary gland cells with AP1 (red) colocalizing with Golgi structures (green).
Burgess, J., Jauregui, M., Tan, J., Rollins, J., Lallet, S., Leventis, P., Boulianne, G., Chang, H., Le Borgne, R., Kramer, H., & Brill, J. (2011). AP-1 and clathrin are essential for secretory granule biogenesis in Drosophila. Molecular Biology of the Cell
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