Increased Zap-70 Association with CD3ζ in CD4 T Cells from Old Mice

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Previous research has shown that many of the CD4 T cells from older mice do not form functional immune synapses after conjugation with peptide-pulsed APC. We now show that the defect lies at a very early stage in the cytoskeletal reorganization that precedes movement of protein kinases and their substrates to the TCR/APC interface. Antagonist peptides presented to T cells from young mice induce migration of talin (but not paxillin, vinculin, or F-actin) to the APC contact zone, but CD4 T cells from older donors typically fail to show the talin polarization response. A spreading assay in which contact with anti-CD3-coated slides induces CD4 T cells to assume a conical shape and develop lammelopodia also shows a decline with age in the proportion of T cells that can initiate cytoskeletal changes in response to this simplified stimulus. Finally, the transition from detergent-soluble to cytoskeletal forms of the p16, p21, and p23 isoforms of CD3ζ in response to CD3/CD4/CD28 cross-linking is much stronger in young than in old T cells. Thus, defects in cytoskeletal reorganization triggered by initial contact between TCR and peptide-bearing APC precede, and presumably contribute to, defective activation of protein kinase-mediated signals in the first few minutes of the activation cascade in T cells from aged mice.

contrasting

confidence: 96%

Section: Cytoskeleton Purification Immunoprecipitation and Western mentioning

confidence: 99%

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Age-Dependent Defects in TCR-Triggered Cytoskeletal Rearrangement in CD4+ T Cells

Garcia¹,

Miller

2002

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“…One of the earliest detectable age-related defects is the decline with age in the phosphorylation of LAT by Zap-70 (28). In vitro kinase assays showed no effects of aging on Zap-70 protein kinase activity in CD4 T cells from young and old mice stimulated by anti-CD3/ anti-CD4 cross-linking (29), suggesting that defective LAT phosphorylation might result from altered accessibility, i.e., differential compartmentalization of Zap-70 and its substrates. Indeed, confocal microscopic studies using anti-CD3 hybridoma cells as polyclonal APC analogs showed that the majority of CD4 T cells from old mice could not efficiently relocate protein kinase C (PKC) , LAT, and p95 vav (Vav) to the immune synapse (28, 30 -31), suggesting that at least some of the age-associated defects in the early stages of signal transduction could be the result of defects in the formation of immune synapses at the site of T cell/APC interaction.…”

Section: Single-cell Analyses Reveal Two Defects Inmentioning

confidence: 97%

Single-Cell Analyses Reveal Two Defects in Peptide-Specific Activation of Naive T Cells from Aged Mice

Garcia

Miller

2001

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114

Confocal fluorescent microscopy was used to study redistribution of membrane-associated proteins in naive T cells from young and old mice from a transgenic stock whose T cells express a TCR specific for a peptide derived from pigeon cytochrome C. About 50% of the T cells from young mice that formed conjugates with peptide-pulsed APC were found to form complexes, at the site of binding to the APC, containing CD3ε, linker for activation of T cells (LAT), and Zap-70 in a central area and c-Cbl, p95vav, Grb-2, PLCγ, Fyn, and Lck distributed more uniformly across the interface area. Two-color staining showed that those cells that were able to relocalize c-Cbl, LAT, CD3ε, or PLCγ typically relocalized all four of these components of the activation complex. About 75% of conjugates that rearranged LAT, c-Cbl, or PLCγ also exhibited cytoplasmic NF-AT migration to the T cell nucleus. Aging had two effects. First, it led to a diminution of ∼2-fold in the proportion of T cell/APC conjugates that could relocalize any of the nine tested proteins to the immune synapse. Second, aging diminished by ∼2-fold the frequency of cytoplasmic NF-AT migration among cells that could generate immune synapses containing LAT, c-Cbl, or PLCγ. Thus naive CD4 T cells from old mice exhibit at least two separable defects in the earliest stages of activation induced by peptide/MHC complexes.

“…CD4 ϩ T cells from old mice show defects in TCR signal transduction that include diminished TCR-phosphorylation, decreased elevation of intracellular Ca ϩ , and diminished activation of the MEK/ERK pathway (20,27,28). In contrast, aging does not affect Zap70-TCR-association (29).…”

mentioning

confidence: 98%

Impaired GATA3-Dependent Chromatin Remodeling and Th2 Cell Differentiation Leading to Attenuated Allergic Airway Inflammation in Aging Mice

Hasegawa

Miki

Hosokawa

et al. 2006

Age-related changes in lymphocytes are most prominent in the T cell compartment. There have been substantial numbers of reports on T cell function in aged mice and humans, such as on the production of Th1 and Th2 cytokines, but the results show considerable variation and contradictions. In the present study, we used 8- to 12-mo-old aging mice and a well-established in vitro Th1/Th2 cell differentiation culture system to identify molecular defects in Th1/Th2 cell differentiation that can be detected in the relatively early stages of aging. The capability to differentiate into Th2 cells is reduced in aging mouse CD4+ T cells. Decreased activation of the ERK MAPK cascade upon TCR stimulation, but normal intracellular-free calcium ion concentration mobilization and normal IL-4-induced STAT6 activation were observed in aging mouse CD4+ T cells. In addition, reduced expression of GATA3 was detected in developing Th2 cells. Chromatin remodeling of the Th2 cytokine gene locus was found to be impaired. Th2-dependent allergic airway inflammation was milder in aging mice compared with in young adult mice. These results suggest that the levels of Th2 cell differentiation and resulting Th2-dependent immune responses, including allergic airway inflammation, decline during aging through defects in the activation of the ERK MAPK cascade, expression of GATA3 protein and GATA3-dependent chromatin remodeling of the Th2 cytokine gene locus. In the present study, we provide the first evidence indicating that a chromatin-remodeling event in T cells is impaired by aging.