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Membrane gangliosides modulate interleukin-2-stimulated T-lymphocyte proliferation
F J Sharom1, A L Chiu, J W Chu
1Guelph-Waterloo Centre for Graduate Work in Chemistry, University of Guelph, Ontario, Canada.
Insights
Cholera toxin B subunit (CT-B) binding to GM1 ganglioside inhibits interleukin-2 (IL-2)-induced lymphocyte proliferation. This modulation occurs early in the IL-2 signaling pathway, independent of G protein involvement.
Area of Science:
- Cellular Biology
- Immunology
- Glycobiology
Background:
- Membrane gangliosides, such as GM1, are known to influence growth factor receptor signaling.
- Interleukin-2 (IL-2) is crucial for lymphocyte proliferation and immune responses.
Purpose of the Study:
- To investigate the role of gangliosides, specifically GM1, in regulating IL-2-induced lymphocyte proliferation.
- To determine the mechanism by which GM1 affects IL-2 signaling.
Main Methods:
- Utilized CTLL-2 and HT-2 cell lines with varying endogenous GM1 levels.
- Administered exogenous GM1 to alter membrane-associated GM1 content.
- Assessed proliferation via DNA synthesis following IL-2 stimulation.
- Investigated CT-B binding effects and IL-2 receptor interactions.
Main Results:
- Low concentrations of CT-B significantly inhibited IL-2-stimulated DNA synthesis in CTLL-2 cells, which have high GM1 levels.
- GM1-enriched HT-2 cells also showed significant inhibition by CT-B.
- CT-B inhibition occurred early in the IL-2 activation pathway and did not affect IL-2 binding.
- Inhibitory effects were GM1-specific and not mediated by G proteins.
Conclusions:
- CT-B binding to GM1 ganglioside modulates IL-2-induced lymphocyte proliferation.
- GM1 plays a regulatory role in IL-2 signaling pathways, impacting cell growth.
- This study highlights gangliosides as potential targets for modulating immune responses.
Abstract:
Membrane gangliosides appear to modulate signal transduction by several growth factor receptors. We have investigated the possible regulation of IL-2-induced proliferation signals by gangliosides. Low concentrations of cholera toxin B subunit (CT-B), which binds specifically to GM1 ganglioside, greatly inhibited IL-2-stimulated DNA synthesis in the IL-2-dependent cell line CTLL-2, but had no effect on proliferation of HT-2. GM1 levels proved to be very low in HT-2 compared to CTLL-2. Large increases in membrane-associated GM1 could be achieved in both cell lines by incubation with exogenous GM1, resulting in a high degree of inhibition of proliferation by CT-B for both CTLL-2 and HT-2. Inhibition was blocked by large unilamellar vesicles containing GM1, but not by vesicles of lipid alone. The time course of CT-B inhibition for CTLL-2 synchronized in G0-G1, indicated that the negative growth signal acts relatively early in the IL-2 activation pathway. CT-B did not affect binding of IL-2 to high-affinity IL-2r. The inhibitory effects of CT-B could not be reversed by pertussis toxin, suggesting that a G protein is probably not involved. These results show that CT-B binding to either endogenous or inserted GM1 can modulate IL-2-induced lymphocyte proliferation.