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A novel gastrin-binding protein in the human eosinophil
M Praissman1, R L Fox, M Walden
1Division of Endocrinology, Nassau County Medical Center, East Meadow, New York 11554, USA. mp@ncmc.co.nassau.ny.us
Biochemical and Biophysical Research Communications
|March 17, 1998
Summary
Researchers found gastrin binds to eosinophils, a type of white blood cell (WBC). This interaction involves major basic protein (MBP) and may regulate gastric acid secretion and mucosal growth.
Area of Science:
- Gastroenterology
- Immunology
- Cell Biology
Background:
- Gastrin plays a key role in regulating gastric acid secretion and mucosal growth.
- Eosinophils are immune cells involved in inflammatory responses.
- The specific interactions between gastrin and eosinophils were not well understood.
Purpose of the Study:
- To investigate the specific interaction between gastrin and human eosinophils.
- To characterize the binding site and molecular properties of the gastrin-binding protein on eosinophils.
Main Methods:
- Autoradiography of human gastric mucosal tissue.
- Isolation and enrichment of white blood cells (WBCs), specifically eosinophils.
- Displacement assays using gastrin to compete with 125I-gastrin binding.
- Scatchard analysis to determine binding kinetics (Kd, Bmax).
- Chemical crosslinking and SDS-PAGE to determine the molecular weight of the binding protein.
Main Results:
- A specific and saturable binding of 125I-gastrin to eosinophils was demonstrated.
- Gastrin displaced 125I-gastrin in a dose-dependent manner (D50 = 11 uM).
- Scatchard analysis revealed a single binding site with low affinity (Kd = 4.14 uM) and high capacity (Bmax = 430 umoles/mg protein).
- The gastrin binding protein, with an approximate molecular weight of 15 kDa, is localized to the granular core of eosinophils.
- The binding protein is likely major basic protein (MBP) based on its characteristics.
Conclusions:
- Human eosinophils possess a specific binding site for gastrin, likely major basic protein (MBP).
- This interaction may serve to limit the cytotoxic effects of MBP on tissues.
- The binding may also attenuate gastrin concentrations, potentially regulating gastric acid secretion and mucosal growth.
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