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Sorting and secretion of salivary proteins
1Department of Anatomy and Cell Biology, University of Virginia, Charlottesville 22908.
Summary
Salivary proteins are stored in granules before secretion. Some proteins bypass storage by budding into vesicles, suggesting selective aggregation is key for protein sorting and transport.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Most salivary proteins are stored in secretion granules within acinar cells before regulated release.
- A subset of salivary proteins are secreted without prior storage, suggesting an alternative pathway.
- This unstimulated secretion may involve vesicles budding from maturing granules.
Purpose of the Study:
- To investigate the mechanism of unstimulated protein secretion from salivary acinar cells.
- To identify the molecular determinants responsible for protein storage in secretion granules.
- To explore the role of protein aggregation in intracellular transport and secretion.
Main Methods:
- Expression of a parotid proline-rich protein and its deletion mutants in pituitary AtT-20 cells.
- Analysis of protein localization and storage within secretion granules.
- Investigation of protein aggregation properties.
Main Results:
- An N-terminal domain of the proline-rich protein was found to be essential for its storage in secretion granules.
- Evidence suggests that self-aggregation of proline-rich protein, mediated by this N-terminal domain, is crucial for efficient intracellular transport.
- This aggregation appears to be a key factor for storage within granules.
Conclusions:
- Selective self-aggregation of proteins is a critical mechanism for sorting and storage in secretory pathways.
- The N-terminal domain of proline-rich proteins plays a vital role in granule storage.
- Understanding these mechanisms sheds light on the regulation of salivary protein secretion.