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Secretion in AtT-20 cells stably transfected with soluble synaptotagmins
1Howard Hughes Medical Institute, Stanford University, California 94305.
Molecular Endocrinology (Baltimore, Md.)
|August 1, 1994
Summary
Synaptotagmin (p65) is crucial for neurotransmitter release. However, this study found that synaptotagmin fragments did not affect regulated secretion or membrane traffic in endocrine cells, suggesting functional redundancy.
Area of Science:
- Neuroscience
- Cell Biology
- Endocrinology
Background:
- Synaptotagmin (p65) is a secretory vesicle protein involved in neurotransmitter release.
- Its role in endocrine cell secretion remains unclear.
Purpose of the Study:
- To investigate the function of synaptotagmin in endocrine cells.
- To determine if synaptotagmin is essential for regulated secretion in these cells.
Main Methods:
- Stable expression of rat synaptotagmin I fragments in mouse AtT-20 cells.
- Assays for regulated secretion (ACTH, [3H]choline release), constitutive secretion, and endocytosis (transferrin uptake).
- Co-immunoprecipitation to study protein interactions.
Main Results:
- Expressed synaptotagmin fragments localized to soluble and membrane fractions.
- The second C2 repeat co-immunoprecipitated with endogenous synaptotagmin.
- No significant effect on regulated secretion, constitutive secretion, or endocytosis was observed.
Conclusions:
- Regulated membrane traffic in endocrine cells may not require synaptotagmin.
- A redundant pathway for secretion might exist in these cells.