title: N6-Methyladenosine inhibition of hypoxanthine uptake by Chinese hamster ovary cells.
abstract: The effects of an adenosine analog, N6-methyladenosine, on the uptake of purines by Chinese hamster ovary (CHO) cells were investigated. Surprisingly, N6-methyladenosine was a more potent inhibitor of the uptake of the 6-hydroxy purines, hypoxanthine and inosine, than of the 6-amino purines, adenine and adenosine. Hypoxanthine uptake was the most profoundly inhibited. The inhibition of hypoxanthine uptake by N6-methyladenosine was dose dependent. Kinetics experiments demonstrated that N6-methyladenosine is a competitive inhibitor of hypoxanthine uptake with a Ki of 30 uM. The effect of N6-methyladenosine on hypoxanthine transport in the absence of metabolism was determined in CHO AK412 cells which lack hypoxanthine phosphoribosyltransferase (HPRT). Hypoxanthine transport by HPRT deficient cells suspended in serum-free medium containing 2 uM hypoxanthine was inhibited by N6-methyladenosine in a dose-dependent manner. When HPRT deficient cells were preincubated for 15 min in 200 uM N6-methyladenosine, a concentration which when present during the transport assay reduces transport to 5% of control, the subsequent transport of hypoxanthine in the absence of inhibitor was 65% of control. This finding suggests that the effects of N6-methyladenosine on hypoxanthine transport are readily reversible. In HPRT deficient cells N6-methyladenosine was a far more effective inhibitor of hypoxanthine transport than adenosine.
mesh_terms: D000225:Adenine / Q000378:metabolism; D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D019271:Hypoxanthine; D007041:Hypoxanthine Phosphoribosyltransferase / Q000172:deficiency; D007042:Hypoxanthines / Q000378:metabolism*; D007700:Kinetics
chemical_list: D007042:Hypoxanthines; D019271:Hypoxanthine; C010223:N-methyladenosine; D007041:Hypoxanthine Phosphoribosyltransferase; D000225:Adenine; D000241:Adenosine