A purine-selective nucleobaseucleoside transporter in PK15NTD cells

摘要

cell growth consumes nucleotides, the building blocks of DNA and RNA. Although most mammalian cells contain de novo biosynthetic pathways for nucleotides, salvage pathways, which utilize extracellular nucleosides and nucleobases, consume less ATP in nucleotide synthesis. The first step of salvage pathways is the transport of nucleosides and nucleobases through the plasma membranes by their respective transporters (8). Nucleoside transport in mammalian cells is divided into Na-dependent and -independent systems that are mediated by the family of concentrative nucleoside transporters [solute carrier family 28 (SLC28) (CNT1-3)] and the family of equilibrative nucleoside transporters [SLC29 (ENT1-4)], respectively (8). The transport of nucleobases into cells is also via Na-dependent and -independent processes (8,14). An Na-dependent hypoxanthine transport system has been described in LLC-PK1 cells, OK cells, guinea-pig kidney cortexes, and calf intestine brush-border membranes (13, 14, 19, 21).