| Research Abstract |
Indoleamine 2,3-dioxygenase (IDO) is a rate-limiting enzyme in the kynurenine pathway of tryplophan metabolism in various tissues of mammals. IDO is induced dramatically (10-100-fold) during many types of infection or inflammation, resulting in a marked increase in tryptophan metabolism locally or systemically. The IDO-mediated tryptophan metabolism deprives the amino acid almost completely from the cells expressing IDO. Such tryptophan deprivation is shown to be one of the mechanisms by which the host cells inhibit growth of infectious pathogens including viruses and intracellular parasites. The IDO induction, however, produces a large amount of metabolites in the kynurenine pathway of tryptophan metabolism, and some of such metabolites have adverse effects on the cellular function by modification of proteins with them and by then agonistic effects on surface receptors on some cells. For example, the metabolites, kynurenine, 3-hydroxykynurenine, and 3-hydroxykynurenine glucoside, bind covalently to lens proteins and the amount of modified proteins increases with age, probably being responsible in part for a cause of age-related cataract. Another metabolite of tryptophan, quinolinic acid, which has a structural similarity to glutamic acid, is found to be an excitatory neurotoxin through an interaction a glutamic acid (NMDA) receptor in vitro and quinolinic acid thus seems to damage neurons dining infection in the brain. IDO deficient mouse helps us to examine these possible adverse effects in vivo. In this research project, we have constructed a targeting vector for IDO gene with neomycin resistant gene and diphtheria toxin gene. Mouse ES cells transfected with ES cells by electroporation and finally 10 ES clones with disrupted IDO gene were obtained.
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