Adenosine kinase inhibition promotes survival of fetal adenosine deaminase-deficient thymocytes by blocking dATP accumulation.
Thymocyte development past the CD4(-)CD8(-) stage is markedly inhibited in adenosine deaminase-deficient (ADA-deficient) murine fetal thymic organ cultures (FTOCs) due to the accumulation of ADA substrates derived from thymocytes failing developmental checkpoints. Such cultures can be rescued by overexpression of Bcl-2, suggesting that apoptosis is an important component of the mechanism by which ADA deficiency impairs thymocyte development. Consistent with this conclusion, ADA-deficient FTOCs were partially rescued by a rearranged T cell receptor beta transgene that permits virtually all thymocytes to pass the beta-selection checkpoint. ADA-deficient cultures were also rescued by the adenosine kinase inhibitor 5'-amino-5'-deoxyadenosine (5'A5'dAdo), indicating that the metabolite responsible for the inhibition of thymocyte development is not adenosine or deoxyadenosine, but a phosphorylated derivative of an ADA substrate. Correction of ADA-deficient FTOCs by 5'A5'dAdo correlated with reduced accumulation of dATP, implicating this compound as the toxic metabolite. In ADA-inhibited FTOCs rescued with a Bcl-2 transgene, however, dATP levels were superelevated, suggesting that cells failing positive and negative selection continued to contribute to the accumulation of ADA substrates. Our data are consistent with dATP-induced mitochondrial cytochrome c release followed by apoptosis as the mechanism by which ADA deficiency leads to reduced thymic T cell production.
Van De Wiele
C Justin
CJ
Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, Oklahoma City 73104, USA.
Vaughn
James G
JG
Blackburn
Michael R
MR
Ledent
Catherine A
CA
Jacobson
Marlene
M
Jiang
Hong
H
Thompson
Linda F
LF
D000243:Adenosine Deaminase / Q000378:metabolism*; D000248:Adenosine Kinase / Q000037:antagonists & inhibitors*; D043383:Adenosylhomocysteinase; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology; D002454:Cell Differentiation; D002470:Cell Survival; D003838:Deoxyadenine Nucleotides / Q000378:metabolism*; D003839:Deoxyadenosines / Q000494:pharmacology; D006867:Hydrolases / Q000037:antagonists & inhibitors; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043705:Receptor, Adenosine A2A; D043704:Receptor, Adenosine A2B; D043684:Receptor, Adenosine A3; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000502:physiology; D018047:Receptors, Purinergic P1 / Q000235:genetics; D013950:Thymus Gland / Q000166:cytology*
D003838:Deoxyadenine Nucleotides; D003839:Deoxyadenosines; D019253:Proto-Oncogene Proteins c-bcl-2; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043705:Receptor, Adenosine A2A; D043704:Receptor, Adenosine A2B; D043684:Receptor, Adenosine A3; D016693:Receptors, Antigen, T-Cell, alpha-beta; D018047:Receptors, Purinergic P1; C057928:5'-amino-5'-deoxyadenosine; D000248:Adenosine Kinase; D006867:Hydrolases; D043383:Adenosylhomocysteinase; D000243:Adenosine Deaminase; C026600:2'-deoxyadenosine triphosphate