Cloning of a novel isoform of the mouse NBMPR-sensitive equilibrative nucleoside transporter (ENT1) lacking a putative phosphorylation site

• Published in: Gene Vol. 262; no. 1-2; pp. 301 - 307
• Main Authors: Handa, M, Choi, D S, Caldeiro, R M, Messing, R O, Gordon, A S, Diamond, I
• Format: Journal Article
• Language: English
• Published: Netherlands 10.01.2001
• Subjects: Amino Acid Sequence; Animals; Carrier Proteins - antagonists & inhibitors; Carrier Proteins - genetics; Carrier Proteins - metabolism; Casein Kinase II; Cloning, Molecular; dipyridamole; Dipyridamole - pharmacology; ENT1 gene; Equilibrative Nucleoside Transporter 1; Gene Expression Regulation; Humans; Inhibitory Concentration 50; Leukemia, T-Cell - drug therapy; Leukemia, T-Cell - genetics; Membrane Proteins - antagonists & inhibitors; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Molecular Sequence Data; NBMPR-sensitive equilibrative nucleoside transporter; Nucleoside Transport Proteins; Phosphorylation; Protein Isoforms; Protein-Serine-Threonine Kinases - metabolism; Rats; Sequence Homology, Amino Acid; Thioinosine - analogs & derivatives; Thioinosine - pharmacology; Tumor Cells, Cultured
• ISSN: 0378-1119
• DOI: 10.1016/s0378-1119(00)00555-2

We have isolated a mouse cDNA clone corresponding to a novel isoform of the NBMPR-sensitive equilibrative nucleoside transporter (ENT1). The cDNA contains a 6 bp deletion in the open reading frame that changes the amino acid composition in a consensus casein kinase II (CKII) phosphorylation site at Ser-254. The clone containing Ser-254 is termed mENT1.1 and the clone lacking the serine termed mENT1.2. The deduced amino acid sequence of mENT1.1 corresponds to the previously cloned human and rat ENT1 proteins at Ser-254. Tissue distribution studies show that mRNA for both ENT1 isoforms are ubiquitously co-expressed in mouse. Analysis of genomic DNA corresponding to mouse ENT1 indicates the isoforms can be produced by alternative splicing at the end of exon 7. CEM/C19 cells stably expressing mENT1.1 and mENT1.2 show similar dose response curves for NBMPR and dipyridamole inhibition of [(3)H]adenosine uptake as well as exhibiting comparable selectivity for both purine and pyrimidine nucleosides but not the corresponding nucleobases.