Maturation of Secretory Granules

  • Sharon A. Tooze
Conference paper
Part of the NATO ASI Series book series (volume 74)


Secretory granules are found in most endocrine, exocrine, and neuronal cells. Their function is to store secretory proteins, such as horomes, in a highly concentrated form within the cell. A hallmark of secretory granules (SGs) is the presence of an electron dense-cored interior which contains the stored secretory proteins. The release of these stored molecules can only be induced by an extracellular signal, which causes the SGs to fuse with the plasma membrane and thereby release the contents. This situation is in contrast to the secretion of proteins by the constitutive pathway: fusion of the constitutive vesicle with the plasma membrane and release of the content occurs very rapidly and is independent of extracellular signals (Burgess and Kelly, 1987). As has been well documented morphologically (for example see Tooze and Tooze, 1986), SGs form in the trans-Golgi network (TGN) when a condensed core of secretory proteins becomes enveloped by membrane, and buds into the cytoplasm. The formation of SGs from the TGN is also being dissected using biochemical approaches. The first event in the formation of SGs, the condensation, or aggregation, of the secretory proteins in the TGN, has been demonstrated in vitro to require conditions similiar to those thought to exist in the TGN, specifically 110mM Calcium and pH6.4 (Chanat and Huttner, 1991). The second event, the budding of the newly formed granules from the TGN has been reconstituted in a cell-free assay (Tooze and Huttner, 1990), and appears to be regulated by a heterotrimeric G-protein (Barr, Leyte et al., 1991; and see abstract from F. Barr).


PC12 Cell Secretory Protein Secretory Granule Dense Core AtT20 Cell 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1993

Authors and Affiliations

  • Sharon A. Tooze
    • 1
  1. 1.European Molecular Biology LaboratoryHeidelbergGermany

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