A motif in the alphabeta T-cell receptor controls positive selection by modulating ERK activity.
Positive selection allows thymocytes that recognize an individual's own major histocompatibility complex (self-MHC) molecules to survive and differentiate, whereas negative selection removes overtly self-reactive thymocytes. Although both forms of thymic selection are mediated by the alphabeta T-cell receptor (TCR) and require self-MHC recognition, an important question is whether they are controlled by distinct signalling cascades. We have shown that mutation of an essential motif within the TCR alpha-chain-connecting peptide domain (alpha-CPM) profoundly affects positive but not negative selection. Using transgenic mice expressing a mutant alpha-CPM TCR we examined the contribution of several mitogen-activated protein kinase (MAPK) cascades to thymic selection. Here we show that in thymocytes expressing a mutant alpha-CPM receptor, a positively selecting peptide failed to activate the extracellular signal-regulated kinase (ERK), although other MAPK cascades were induced normally. The defect in ERK activation was associated with impaired recruitment of the activated tyrosine kinases Lck and ZAP-70, phosphorylated forms of the TCR component CD3zeta and the adaptor protein LAT to detergent-insoluble glycolipid-enriched microdomains (DIGs). Therefore, an intact DIG-associated signalosome is essential for sustained ERK activation, which leads to positive selection.
Basel Institute for Immunology, Switzerland. werlen@bii.ch
G
G
Werlen
B
B
Hausmann
E
E
Palmer
D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004789:Enzyme Activation; D019891:Leukopoiesis / Q000502:physiology; D020935:MAP Kinase Signaling System; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009154:Mutation; D009842:Oligopeptides / Q000378:metabolism; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D013950:Thymus Gland / Q000166:cytology*
D009842:Oligopeptides; D016693:Receptors, Antigen, T-Cell, alpha-beta; D020928:Mitogen-Activated Protein Kinases