TY - JOUR
T1 - Functional expression and characterization of a sodium-dependent nucleoside transporter hCNT2 cloned from human duodenum
AU - Shin, Ho Chul
AU - Landowski, Christopher P.
AU - Sun, Duxin
AU - Vig, Balvinder S.
AU - Kim, Insook
AU - Mittal, Sachin
AU - Lane, Majella
AU - Rosania, Gustavo
AU - Drach, John C.
AU - Amidon, Gordon L.
PY - 2003/8/1
Y1 - 2003/8/1
N2 - We have cloned and functionally expressed a sodium-dependent human nucleoside transporter, hCNT2, from a CNS cancer cell line U251. Our cDNA clone of hCNT2 had the same predicted amino acid sequence as the previously cloned hCNT2 transporter. Of the several cell lines studied, the best hCNT2 transport function was obtained when transiently expressed in U251 cells. Na + -dependent uptake of [ 3 H]inosine in U251 cells transiently expressing hCNT2 was 50-fold greater than that in non-transfected cells, and uptake in Na + -containing medium was approximately 30-fold higher than that at Na + -free condition. The hCNT2 displayed saturable uptake of [ 3 H]inosine with K m of 12.8μM and V max of 6.66pmol/mg protein/5min. Uptake of [ 3 H]inosine was significantly inhibited by the purine nucleoside drugs dideoxyinosine and cladribine, but not by acyclic nucleosides including acyclovir, ganciclovir, and their prodrugs valacyclovir and valganciclovir. This indicates that the closed ribose ring is important for binding of nucleoside drugs to hCNT2. Among several pyrimidine nucleosides, hCNT2 favorably interacted with the uridine analogue floxuridine. Interestingly, we found that benzimidazole analogues, including maribavir, 5,6-dichloro-2-bromo-1-β-D-ribofuranosylbenzimidazole (BDCRB), and 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB), were strong inhibitors of inosine transport, even though they have a significantly different heterocycle structure compared to a typical purine ring. As measured by GeneChip arrays, mRNA expression of hCNT2 in human duodenum was 15-fold greater than that of hCNT1 or hENT2. Further, the rCNT2 expression in rat duodenum was 20-fold higher than rCNT1, rENT1 or rENT2. This suggests that hCNT2 (and rCNT2) may have a significant role in uptake of nucleoside drugs from the intestine and is a potential transporter target for the development of nucleoside and nucleoside-mimetic drugs.
AB - We have cloned and functionally expressed a sodium-dependent human nucleoside transporter, hCNT2, from a CNS cancer cell line U251. Our cDNA clone of hCNT2 had the same predicted amino acid sequence as the previously cloned hCNT2 transporter. Of the several cell lines studied, the best hCNT2 transport function was obtained when transiently expressed in U251 cells. Na + -dependent uptake of [ 3 H]inosine in U251 cells transiently expressing hCNT2 was 50-fold greater than that in non-transfected cells, and uptake in Na + -containing medium was approximately 30-fold higher than that at Na + -free condition. The hCNT2 displayed saturable uptake of [ 3 H]inosine with K m of 12.8μM and V max of 6.66pmol/mg protein/5min. Uptake of [ 3 H]inosine was significantly inhibited by the purine nucleoside drugs dideoxyinosine and cladribine, but not by acyclic nucleosides including acyclovir, ganciclovir, and their prodrugs valacyclovir and valganciclovir. This indicates that the closed ribose ring is important for binding of nucleoside drugs to hCNT2. Among several pyrimidine nucleosides, hCNT2 favorably interacted with the uridine analogue floxuridine. Interestingly, we found that benzimidazole analogues, including maribavir, 5,6-dichloro-2-bromo-1-β-D-ribofuranosylbenzimidazole (BDCRB), and 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB), were strong inhibitors of inosine transport, even though they have a significantly different heterocycle structure compared to a typical purine ring. As measured by GeneChip arrays, mRNA expression of hCNT2 in human duodenum was 15-fold greater than that of hCNT1 or hENT2. Further, the rCNT2 expression in rat duodenum was 20-fold higher than rCNT1, rENT1 or rENT2. This suggests that hCNT2 (and rCNT2) may have a significant role in uptake of nucleoside drugs from the intestine and is a potential transporter target for the development of nucleoside and nucleoside-mimetic drugs.
KW - BDCRB
KW - Cloning
KW - Floxuridine
KW - Functional expression
KW - GeneChip expression
KW - hCNT2
KW - Maribavir
KW - U251
UR - http://www.scopus.com/inward/record.url?scp=0042671494&partnerID=8YFLogxK
U2 - 10.1016/S0006-291X(03)01259-2
DO - 10.1016/S0006-291X(03)01259-2
M3 - Article
C2 - 12893280
AN - SCOPUS:0042671494
SN - 0006-291X
VL - 307
SP - 696
EP - 703
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
IS - 3
ER -
