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Influence of gangliosides on the IL-2- and IL-4-dependent cell proliferation
Irina M Molotkovskaya1, Roman V Kholodenko, Julian G Molotkovsky
1Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow. imm@ibch.ru
Abstract:
Ganglioside-induced apoptosis in the cells of IL-2-dependent cytotoxic murine cell line CTLL-2 was shown to be caspase dependent: GM1-, GM2-, and GD3-induced suppression of cell proliferation was cancelled by a general caspase inhibitor Z-VAD-FMK. Ganglioside-induced apoptosis pathways are different for different individual glycolipids; the differences exist both at the initiation and effector stages of the caspase cascade. Only for GM1-induced process, molecular mechanisms of signal transduction coincide with the ones for CD95 and TNFalpha: the participation of both the main initiation caspases 8, 1, and 4, and caspases 3 and 9 as well, has been shown. Caspase 3 participates in the pathway induced by GM3, GD1a, GD1b, and GT1b, but not by GM2. As morphological features show, tumor-associated ganglioside GM2 is also a stimulus of programmed cell death (PCD) for CTLL-2 cell line: addition of GM2 into cell culture has resulted in appearance of annexin V-positive cells and in accumulation of DNA breaks (shown by the TUNEL direct dyeing of the open ends). But a caspase 3 inhibitor Z-DEVD-FMK did not restore the cell proliferation suppressed by GM2, and addition of a fluorescent substrate of caspase 3 Ac-DEVD-AFC did not result in the fluorescence development. So caspase 3 does not participate in downstream pathways of GM2-induced cell apoptosis, and a PCD-effector system other than the apoptosome-mediated one is involved here.
Insights
Gangliosides induce programmed cell death (PCD) in CTLL-2 cells via caspase-dependent pathways. However, GM2 ganglioside triggers PCD through a caspase-3-independent mechanism, suggesting alternative cell death pathways.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Gangliosides are glycosphingolipids involved in cellular processes.
- Programmed cell death (PCD) pathways can be triggered by various stimuli.
- The CTLL-2 cell line is an IL-2-dependent cytotoxic murine cell line.
Purpose of the Study:
- To investigate the role of gangliosides in inducing apoptosis in CTLL-2 cells.
- To elucidate the specific caspase-dependent or independent pathways involved in ganglioside-induced PCD.
- To compare the mechanisms of apoptosis induced by different gangliosides.
Main Methods:
- Treatment of CTLL-2 cells with various gangliosides (GM1, GM2, GD3, GM3, GD1a, GD1b, GT1b).
- Use of general caspase inhibitor (Z-VAD-FMK) and caspase-3 inhibitor (Z-DEVD-FMK).
- Assessment of cell proliferation, annexin V staining, TUNEL assay, and caspase-3 activity (Ac-DEVD-AFC).
Main Results:
- GM1, GM2, and GD3 induced caspase-dependent suppression of cell proliferation.
- GM1-induced apoptosis involved caspases 8, 1, 4, 3, and 9, similar to CD95 and TNFalpha pathways.
- Caspase-3 was involved in apoptosis induced by GM3, GD1a, GD1b, and GT1b, but not by GM2.
- GM2 induced morphological features of PCD (annexin V positivity, DNA breaks) but was independent of caspase-3 activity.
Conclusions:
- Ganglioside-induced apoptosis pathways differ based on the specific glycolipid.
- GM1 utilizes signaling pathways similar to CD95 and TNFalpha.
- GM2 induces programmed cell death in CTLL-2 cells via a caspase-3-independent mechanism, indicating involvement of alternative effector systems.