Publications

• Functional analysis of the human concentrative nucleoside transporter-1 variant hCNT1S546P provides insight into the sodium-binding pocket.

  Cano-Soldado P., Gorraitz E., Errasti-Murugarren E., Casado F.J., Lostao M.P., Pastor-Anglada M.

  SLC28 genes, encoding concentrative nucleoside transporter proteins (CNT), show little genetic variability, although a few single nucleotide polymorphisms (SNPs) have been associated with marked functional disturbances. In particular, human CNT1S546P had been reported to result in negligible thymi ... >> More

  SLC28 genes, encoding concentrative nucleoside transporter proteins (CNT), show little genetic variability, although a few single nucleotide polymorphisms (SNPs) have been associated with marked functional disturbances. In particular, human CNT1S546P had been reported to result in negligible thymidine uptake. In this study we have characterized the molecular mechanisms responsible for this apparent loss of function. The hCNT1S546P variant showed an appropriate endoplasmic reticulum export and insertion into the plasma membrane, whereas loss of nucleoside translocation ability affected all tested nucleoside and nucleoside-derived drugs. Site-directed mutagenesis analysis revealed that it is the lack of the serine residue itself responsible for the loss of hCNT1 function. This serine residue is highly conserved, and mutation of the analogous serine in hCNT2 (Ser541) and hCNT3 (Ser568) resulted in total and partial loss of function, respectively. Moreover, hCNT3, the only member that shows a 2Na(+)/1 nucleoside stoichiometry, showed altered Na(+) binding properties associated with a shift in the Hill coefficient, consistent with one Na(+) binding site being affected by the mutation. Two-electrode voltage-clamp studies using the hCNT1S546P mutant revealed the occurrence of Na(+) leak, which was dependent on the concentration of extracellular Na(+) indicating that, although the variant is unable to transport nucleosides, there is an uncoupled sodium transport. << Less

  Am. J. Physiol. 302:C257-C266(2012) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Molecular identification and characterization of novel human and mouse concentrative Na+-nucleoside cotransporter proteins (hCNT3 and mCNT3) broadly selective for purine and pyrimidine nucleosides (system cib).

  Ritzel M.W.L., Ng A.M.L., Yao S.Y.M., Graham K., Loewen S.K., Smith K.M., Ritzel R.G., Mowles D.A., Carpenter P., Chen X.-Z., Karpinski E., Hyde R.J., Baldwin S.A., Cass C.E., Young J.D.

  The human concentrative (Na(+)-linked) plasma membrane transport proteins hCNT1 and hCNT2 are selective for pyrimidine nucleosides (system cit) and purine nucleosides (system cif), respectively. Both have homologs in other mammalian species and belong to a gene family (CNT) that also includes hfCN ... >> More

  The human concentrative (Na(+)-linked) plasma membrane transport proteins hCNT1 and hCNT2 are selective for pyrimidine nucleosides (system cit) and purine nucleosides (system cif), respectively. Both have homologs in other mammalian species and belong to a gene family (CNT) that also includes hfCNT, a newly identified broad specificity pyrimidine and purine Na(+)-nucleoside symporter (system cib) from the ancient marine vertebrate, the Pacific hagfish (Eptatretus stouti). We now report the cDNA cloning and characterization of cib homologs of hfCNT from human mammary gland, differentiated human myeloid HL-60 cells, and mouse liver. The 691- and 703-residue human and mouse proteins, designated hCNT3 and mCNT3, respectively, were 79% identical in amino acid sequence and contained 13 putative transmembrane helices. hCNT3 was 48, 47, and 57% identical to hCNT1, hCNT2, and hfCNT, respectively. When produced in Xenopus oocytes, both proteins exhibited Na(+)-dependent cib-type functional activities. hCNT3 was electrogenic, and a sigmoidal dependence of uridine influx on Na(+) concentration indicated a Na(+):uridine coupling ratio of at least 2:1 for both hCNT3 and mCNT3 (cf 1:1 for hCNT1/2). Phorbol myristate acetate-induced differentiation of HL-60 cells led to the parallel appearance of cib-type activity and hCNT3 mRNA. Tissues containing hCNT3 transcripts included pancreas, bone marrow, trachea, mammary gland, liver, prostate, and regions of intestine, brain, and heart. The hCNT3 gene mapped to chromosome 9q22.2 and included an upstream phorbol myristate acetate response element. << Less

  J. Biol. Chem. 276:2914-2927(2001) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.