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The molecular basis of enzyme secretion
1Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, Massachusetts.
Gastroenterology
|October 1, 1990
Summary
Pancreatic acinar cells secrete enzymes through complex signaling pathways, challenging the traditional view of calcium as the sole trigger. Novel research highlights the inositol lipid pathway
Area of Science:
- Cellular Biology
- Molecular Biology
- Biochemistry
Background:
- Acinar cells are a well-established model for studying exocytotic secretion.
- The classical model posits that pancreatic secretagogues stimulate enzyme release via increased cytosolic free Ca2+ or cyclic adenosine monophosphate.
- Recent findings challenge this model, emphasizing the role of phospholipid metabolism and advanced Ca2+ monitoring techniques.
Purpose of the Study:
- To review recent advances in understanding signal transduction mechanisms in acinar cells.
- To emphasize the role of the inositol lipid pathway in enzyme secretion.
- To propose a new working model for enzyme secretion from acinar cells.
Main Methods:
- Review of existing literature on acinar cell secretion and signal transduction.
- Analysis of studies utilizing sensitive techniques to monitor cytosolic free Ca2+.
- Integration of data on phospholipid metabolism and second messenger systems.
Main Results:
- Evidence suggests a generalized increase in cytosolic free Ca2+ is not sufficient or necessary for exocytosis in nonexcitable cells.
- A single agonist can activate multiple signal transduction pathways, refuting the single second messenger system model.
- The inositol lipid pathway plays a pivotal role in the cascade of events leading to secretion.
Conclusions:
- The classical model of pancreatic acinar cell secretion requires revision.
- Signal transduction involves complex interplay of multiple pathways, not solely Ca2+ elevation.
- A new working model integrating phospholipid metabolism and diverse signaling is proposed.
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