Insights into thymic purine metabolism and adenosine deaminase deficiency revealed by transgenic mice overexpressing ecto-5'-nucleotidase (CD73).
The adenosine producing enzyme ecto-5'-nucleotidase (5'-NT) is not normally expressed during thymocyte development until the medullary stage. To determine whether earlier expression would lead to adenosine accumulation and/or be deleterious for thymocyte maturation, thymic purine metabolism, and T cell differentiation were studied in lckNT transgenic mice overexpressing 5'-NT in cortical thymocytes under the control of the lck proximal promoter. In spite of a 100-fold elevation in thymic 5'-NT activity, transgenic adenosine levels were unchanged and T cell immunity was normal. Inosine, the product of adenosine deamination, was elevated more than twofold, however, indicating that adenosine deaminase (ADA) can prevent the accumulation of adenosine, even with a dramatic increase in 5'-NT activity, and demonstrating the availability of 5'-NT substrates in the thymus for the first time. Thymic adenosine concentrations of mice treated with the ADA inhibitor 2'-deoxycoformycin (dCF) were elevated over 30-fold, suggesting that high ADA activity, rather than an absence of 5'-NT, is mainly responsible for low thymic adenosine levels. The adenosine concentrations in dCF-treated mice are sufficient to cause adenosine receptor-mediated thymocyte apoptosis in vitro, suggesting that adenosine accumulation could play a role in ADA-deficient severe combined immunodeficiency.
Resta
R
R
Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, Oklahoma City 73104, USA.
Hooker
S W
SW
Laurent
A B
AB
Jamshedur Rahman
S M
SM
Franklin
M
M
Knudsen
T B
TB
Nadon
N L
NL
Thompson
L F
LF
D015720:5'-Nucleotidase / Q000096:biosynthesis*; D000241:Adenosine / Q000378:metabolism; D000243:Adenosine Deaminase / Q000172:deficiency*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000276:immunology; D005260:Female; D007113:Immunity, Innate; D007136:Immunoglobulins / Q000097:blood; D016130:Immunophenotyping; D007288:Inosine / Q000378:metabolism; D008213:Lymphocyte Activation; D008221:Lymphoid Tissue / Q000166:cytology / Q000201:enzymology; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D058906:Purinergic P1 Receptor Agonists; D011687:Purines / Q000378:metabolism*; D011828:Radiation Chimera; D012098:Reproduction / Q000276:immunology; D016019:Survival Analysis; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000528:radiation effects; D013950:Thymus Gland / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism*; D019076:Transgenes / Q000276:immunology
D000911:Antibodies, Monoclonal; D007136:Immunoglobulins; D058906:Purinergic P1 Receptor Agonists; D011687:Purines; D007288:Inosine; D015720:5'-Nucleotidase; D000243:Adenosine Deaminase; D000241:Adenosine