Two YxxL segments of a single immunoreceptor tyrosine-based activation motif in the CD3zeta molecule differentially activate calcium mobilization and mitogen-activated protein kinase family pathways.
Immunoreceptor tyrosine-based activation motifs (ITAM), consisting of two YxxL segments, transmit signals leading to IL-2 gene activation in T cells. We investigated here the functional difference in signal transduction between these two YxxL segments in the CD3zeta membrane-proximal ITAM. N-terminal YxxL mutants failed to induce ZAP-70 phosphorylation, elevation of intracellular Ca2+ concentration ([Ca2+]i) or extracellular signal-regulated kinase (ERK) activation even in the presence of CD28 co-stimulation, whereas a mutant of the leucine residue at the C-terminal YxxL segment retained the ability to induce these events although this mutation abrogated the ability to induce IL-2 gene activation. In marked contrast to ERK activation, c-Jun N-terminal kinase (JNK) activation was observed in all mutants when co-stimulated with CD28. The mutant of the leucine residue at the C-terminal YxxL segment had a defect in the transcriptional activation at the NF-AT cis-element, which was restored to wild-type level by addition of a Ca2+ ionophore, suggesting that the intensity and/or duration of [Ca2+]i elevation defines the threshold of T cell activation in this mutant. Our data collectively indicate that the activation pathways of ERK, JNK and Ca2+ mobilization are differentially regulated through YxxL segments of an ITAM.
Tsuchihashi
N
N
Department of Microbiology and Immunology, Keo University School of Medicine, Tokyo, Japan.
Matsuda
S
S
Reinherz
E L
EL
Koyasu
S
S
D000595:Amino Acid Sequence; D001665:Binding Sites; D017252:CD3 Complex / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D051746:ZAP-70 Protein-Tyrosine Kinase
D017252:CD3 Complex; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D014157:Transcription Factors; D014443:Tyrosine; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium