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G proteins in T cell signal transduction
1Institute of Theoretical and Experimental Biophysics, USSR Academy of Sciences, Pushchino, Moscow Region.
Abstract:
This review summarises recent data on G protein implication in receptor signalling in T cells. The data show that PPI-specific PLC in T cell membranes is under G protein control. Some evidence indicates that a G protein couples PLC to TCR. Differences are revealed between the effects induced by direct G protein activators, such as GTP gamma S or AlF4-, and TCR ligands, which imply that TCR ligands may trigger some G-protein-independent signals. An analysis of the conflicting results on the action of PTX and CTX, one of the main tools in studying G proteins, has shown that the toxins produce both G protein-dependent and independent effects. The G protein which couples PLC to TCR appears insensitive to both PTX and CTX. Some findings suggest G protein involvement in signalling induced by interleukins; however, in this case the effector molecules implicate often remain unknown. Scarce data on G protein involvement in signalling from differentiation antigens, on direct G protein regulation of ion channels, and on identification of G proteins in T cells, are also discussed.
Insights
This review highlights G protein involvement in T cell receptor signaling. G proteins control phospholipase C activity and may link to T cell receptors, with some signals being G protein-independent.
Area of Science:
- Immunology
- Cellular Signaling
Background:
- G proteins are crucial regulators of cellular signaling pathways.
- T cell activation relies on complex signaling cascades initiated by the T cell receptor (TCR).
Purpose of the Study:
- To review recent data on the role of G proteins in T cell receptor signaling.
- To clarify the mechanisms by which G proteins influence T cell responses.
Main Methods:
- Literature review of recent studies on G protein signaling in T cells.
- Analysis of data concerning G protein activators, TCR ligands, and toxin effects.
Main Results:
- G proteins regulate phospholipase C (PLC) activity in T cell membranes.
- Evidence suggests G proteins couple PLC to the TCR, though some TCR-induced signals are G protein-independent.
- Pertussis toxin (PTX) and cholera toxin (CTX) exhibit both G protein-dependent and independent effects, with the TCR-coupling G protein being insensitive to these toxins.
- G protein involvement in interleukin signaling is suggested, but effectors remain largely unidentified.
Conclusions:
- G protein signaling is integral to T cell activation, particularly via the TCR.
- Further research is needed to fully elucidate G protein involvement in T cell differentiation antigen and ion channel signaling.