Cloning of a novel isoform of the mouse NBMPR-sensitive equilibrative nucleoside transporter (ENT1) lacking a putative phosphorylation site.
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.
Handa
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Ernest Gallo Clinic and Research Center, Department of Neurology, University of California, San Francisco, CA 94608, USA.
Choi
D S
DS
Caldeiro
R M
RM
Messing
R O
RO
Gordon
A S
AS
Diamond
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I
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D047390:Casein Kinase II; D003001:Cloning, Molecular; D004176:Dipyridamole / Q000494:pharmacology; D033721:Equilibrative Nucleoside Transporter 1; D005786:Gene Expression Regulation; D006801:Humans; D020128:Inhibitory Concentration 50; D015458:Leukemia, T-Cell / Q000188:drug therapy / Q000235:genetics; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D033703:Nucleoside Transport Proteins; D010766:Phosphorylation; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013868:Thioinosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D033721:Equilibrative Nucleoside Transporter 1; D008565:Membrane Proteins; D033703:Nucleoside Transport Proteins; D020033:Protein Isoforms; C498476:SLC29A1 protein, mouse; C438652:Slc29a1 protein, rat; D013868:Thioinosine; D004176:Dipyridamole; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; C001789:4-nitrobenzylthioinosine