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Immunoglobulin-derived polypeptides enter the regulated secretory pathway in AtT-20 cells
A M Castle1, A Y Huang, J D Castle
1Department of Cell Biology, University of Virginia Health Sciences Center, Charlottesville 22908, USA. amc3c@virginia.edu
FEBS Letters
|December 9, 1998
Summary
Constitutively secreted proteins, like kappa light chain and Fc fragment, are found in the regulated secretory pathway. These proteins show stimulus-dependent secretion, challenging traditional views of protein sorting.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Secretion
Background:
- Traditionally, constitutively secreted proteins were thought to be excluded from the regulated secretory pathway.
- The regulated secretory pathway is crucial for storing and releasing hormones and neurotransmitters upon stimulation.
Purpose of the Study:
- To investigate whether proteins markers of the constitutive pathway are present in the regulated secretory pathway.
- To determine if these proteins exhibit stimulus-dependent secretion.
Main Methods:
- Utilized AtT-20 cells, a model for regulated secretion.
- Investigated the localization of kappa light chain and Fc fragment.
- Observed colocalization with adrenocorticotropic hormone (ACTH).
- Assessed stimulus-dependent secretion.
Main Results:
- Kappa light chain and Fc fragment were found in the regulated secretory pathway in AtT-20 cells.
- These proteins colocalized with the endogenous hormone ACTH.
- Fc fragment entered forming secretory granules but was partially lost during maturation.
- Both markers exhibited stimulus-dependent secretion.
Conclusions:
- Classic constitutive secretory markers are not excluded from the regulated secretory pathway.
- Efficient sorting for regulated secretion occurs alongside proteins that enter granules non-specifically.
- This challenges the strict dichotomy between constitutive and regulated secretion pathways.