Effect of age and oxidative stress on tyrosine phosphorylation of ZAP-70.
Oxidative stress is believed to be one of the leading contributors to the aging process and loss of cellular function with aging. Although, several age-associated phenomena have been correlated with reactive oxygen species, the role of oxidative stress in the age-related decline of T-cell activity is not yet clear. The present study was carried out to determine the effect of reactive oxygen species on tyrosine phosphorylation of ZAP-70, a key enzyme in the T-cell signal transduction pathway. Our previous as well as present studies have demonstrated an age-related down-regulation of tyrosine phosphorylation of ZAP-70 following activation of freshly isolated T cells with various stimulating agents. Currently, we observe that under mild and chronic oxidative stress, tyrosine phosphorylation of ZAP-70 is impaired following stimulation of the T cells with anti-CD3 antibody. Interestingly, in contrast to our observation using freshly isolated T cells, there is no age-associated impairment of tyrosine phosphorylation of ZAP-70 when T cells, cultured for 2 days in a serum-free medium in the presence or in the absence of oxidative stress, are stimulated with anti-CD3 antibody. The current observation suggests that the age-associated down-regulation of tyrosine phosphorylation of ZAP-70 is not an intrinsic defect inherent of the T cells due to aging and is reversible. We also observed that under oxidative stress in vitro, there was no significant difference in inhibition of tyrosine phosphorylation of ZAP-70 in T cells isolated from elderly and young donors. Finally, it was also noted that the down-regulation of tyrosine phosphorylation of ZAP-70 under oxidative stress in young and elderly donors was not due to impairment in the net expression of ZAP-70 under oxidative stress thereby suggesting that dysregulation in the balance of kinase-phosphatase activities under oxidative stress might have been implicated in the observed phenomenon.
Chakravarti
Bulbul
B
Department of Medicine and Center on Aging, University of Rochester Cancer Center, University of Rochester Medical Center, Rochester, New York, NY 14642, USA. bchak@firstclass.rit.edu
Abraham
George N
GN
D000328:Adult; D000368:Aged; D000375:Aging / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017252:CD3 Complex / Q000276:immunology; D002478:Cells, Cultured; D006801:Humans; D010085:Oxidative Phosphorylation; D018384:Oxidative Stress / Q000276:immunology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D014443:Tyrosine / Q000378:metabolism*; D051746:ZAP-70 Protein-Tyrosine Kinase
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human