Nucleoside transporters: molecular biology and implications for therapeutic development

The uptake of nucleosides (for nucleobases) is essential for nucleic acid s ynthesis in many human cell types and in parasitic organisms that cannot sy nthesize nucleotides de novo. The transporters responsible are also the rou te of entry for many cytotoxic nucleoside analogues used in cancer and vira l chemotherapy. Moreover, by regulating adenosine concentrations in the vic inity of its cell-surface receptors, nucleoside transporters profoundly aff ect neurotransmission, vascular tone and other processes. The recent molecu lar characterization of two families of human nucleoside transporters has p rovided new insights into the mechanisms of natural nucleotide and drug upt ake and into future developments of improved therapies.