Glycine-extended gastrin regulates HEK cell growth
V M Stepan1, D F Krametter, M Matsushima
1Department of Pediatrics, University of Michigan, Medical Center, Ann Arbor, Michigan 48109, USA.
The American Journal of Physiology
|August 13, 1999
Summary
Carboxy-terminally amidated gastrin (G-NH(2)) and glycine-extended gastrin (G-Gly) stimulate human embryonic kidney cell growth. These peptides act cooperatively via distinct receptors in an autocrine manner.
Area of Science:
- Endocrinology
- Cell Biology
- Molecular Biology
Background:
- Progastrin is posttranslationally processed to G-NH(2), essential for gastric acid secretion and other effects via gastrin/CCK-B receptors.
- Glycine-extended gastrin (G-Gly), the precursor to G-NH(2), lacks gastric acid stimulating effects at physiological concentrations but is abundant during development.
- Both G-NH(2) and G-Gly exhibit potent growth-stimulatory effects on gastrointestinal tissues, with G-NH(2) also promoting human kidney cell proliferation.
Purpose of the Study:
- To investigate the actions of G-NH(2) and G-Gly on the human embryonic kidney cell line HEK 293.
- To determine if these gastrin forms influence cell proliferation and signaling pathways in a non-gastrointestinal cell line.
Main Methods:
- HEK 293 cells were assessed for specific binding sites for radiolabeled G-NH(2) and G-Gly.
- [(3)H]thymidine incorporation was measured to assess cell proliferation in response to G-NH(2) and G-Gly.
- Radioimmunoassay was used to detect G-NH(2) and G-Gly in conditioned media.
- Intracellular calcium (Ca(2+)) concentration changes were monitored.
- The effects of antibodies against G-NH(2) and G-Gly on proliferation were evaluated.
Main Results:
- HEK 293 cells displayed specific binding sites for both (125)I-labeled Leu(15)-G17-NH(2) and (125)I-Leu(15)-G(2-17)-Gly.
- Both G-NH(2) and G-Gly dose-dependently increased [(3)H]thymidine incorporation, with a synergistic effect when applied together.
- G-NH(2) and G-Gly were detected in serum-free conditioned media, indicating autocrine production.
- Antibodies against G-NH(2) and G-Gly significantly reduced [(3)H]thymidine incorporation.
- G-NH(2) elevated intracellular Ca(2+) concentration, whereas G-Gly did not.
Conclusions:
- G-NH(2) and G-Gly cooperatively stimulate the growth of the human embryonic kidney cell line HEK 293.
- These gastrin forms act via distinct receptors on HEK 293 cells.
- The observed growth stimulation occurs in an autocrine fashion.
- G-NH(2) and G-Gly play a role in regulating the proliferation of nongastrointestinal cells.
