Phospholipases stimulate secretion in RBL mast cells
1Department of Molecular Medicine, Veterinary Medical Center, and Field of Biochemistry, Molecular and Cellular Biology, Cornell University, Ithaca, New York 14853-6401, USA.
Biochemistry
|May 31, 2001
Summary
Exogenous phospholipases triggering phosphatidylcholine hydrolysis can induce mast cell degranulation. This suggests a pathway for regulated secretion in vitro, independent of intracellular factors.
Area of Science:
- Cell Biology
- Biochemistry
- Immunology
Background:
- The role of glycerophospholipids in exocytosis, particularly in mast cells, remains debated.
- Phospholipase activity increases upon activation of the high-affinity immunoglobulin E (IgE) receptor in mast cells.
Purpose of the Study:
- To investigate the biochemical mechanisms underlying mast cell degranulation.
- To determine if exogenous phospholipases can induce degranulation in a cell-free system.
Main Methods:
- Utilized broken cell systems with permeabilized RBL-2H3 mast cells.
- Added three types of exogenous phospholipases (bcPLC, scPLD, tfPLA2) that hydrolyze phosphatidylcholine (PC).
Main Results:
- Exogenous phospholipases (bcPLC, scPLD, tfPLA2) triggered degranulation in permeabilized mast cells.
- The hydrolysis of phosphatidylcholine by these enzymes produced bioactive lipids that promoted granule release.
- This process occurred downstream of PKC, PIP(2), and Rho GTPases and bypassed IgE receptor signaling.
Conclusions:
- Regulated secretion can be achieved in vitro using exogenous phospholipase activation.
- Products of phosphatidylcholine hydrolysis are sufficient to promote exocytosis in mast cells, independent of cytosolic factors.
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