- Peptide (C)EPQKPGKPSVFVVFRK, corresponding to amino acid residues 273-288 of rat ENT2 (Accession O54699). 3rd intracellular loop.
- Western blot analysis of rat heart (lanes 1 and 3) and mouse brain (lanes 2 and 4) lysates:1,2. Anti-ENT2 (SLC29A2) Antibody (#ANT-052), (1:200).
3,4. Anti-ENT2 (SLC29A2) Antibody, preincubated with ENT2/SLC29A2 Blocking Peptide (#BLP-NT052).
- Expression of ENT2 in rat hippocampusImmunohistochemical staining of perfusion-fixed frozen rat brain sections with Anti-ENT2 (SLC29A2) Antibody (#ANT-052), (1:300), followed by donkey anti-rabbit-biotin and streptatividin-Cy3. ENT2 staining (red) in the rat hippocampal dentate gyrus is detected in the granule layer (G), in hilar neurons (vertical arrows) and astrocytes (horizontal arrows). Cell nuclei are stained with DAPI (blue).
- Expression of ENT2 in mouse C2C12 myoblast cellsImmunocytochemical staining of fixed and permeabilized mouse C2C12 myoblast cells. A. Cells were stained with Anti-ENT2 (SLC29A2) Antibody (#ANT-052), (1:500), followed by goat anti-rabbit-AlexaFluor-594 secondary antibody (red). B. Cell nuclei were visualized using Hoechst 33342 (blue). C. Merge of the two images.
- Molina-Arcas, M. et al. (2009) Curr. Vasc. Pharmacol. 7, 426.
- Rose, J.B. and Coe, I.R. (2008) Physiology 23, 41.
- Baldwin, S.A. et al. (2004) Pflugers Arch. 447, 735.
- Crawford, C.R. et al. (1998) J. Biol. Chem. 273, 288.
- Baldwin, S.A. et al. (2005) J. Biol. Chem. 280, 15880.
- Barnes, K. (2006) Circ. Res. 99, 510.
Nucleosides play other important roles beyond their nucleic acid synthesis building block role. For example, they are involved in energy metabolism; they serve as ligands of purinergic receptors and act as influential signaling molecules1. Being hydrophilic, nucleosides cannot simply diffuse across the plasma membrane in order to exert their various functions, but rather need to be physically transported via nucleoside transporters1,2.
Two different transporter families are responsible for transporting nucleosides across the plasma membrane: The Concentrative Nucleoside Transporter proteins (CNT, SLC28 family), which consist of three members, CNT1-3, and act as Na+-dependent symporters1,3, and the Equilibrative Nucleoside Transporter proteins ENT1-4 (ENT, SLC29 family), which mediate Na+-independent facilitated diffusion. ENTs act as bidirectional carriers, responsible for the influx and efflux of substrates1.
Structurally, ENT transporters have eleven transmembrane domains with an intracellular N-terminal and an extracellular C-terminal1.
The best characterized ENT transporters are ENT1 and ENT2, which, although display a broader range of substrate selectivity, have lower affinities for nucleosides compared to concentrative transporters. They are ubiquitously expressed. For example, ENT1 is expressed in erythrocytes, vascular endothelium, the placenta, brain, heart, liver and colon1,4. ENT2 displays more or less the same expression pattern but in addition, is strongly expressed in skeletal muscle1,5. ENT3 is a lysosomal pH-dependent transporter capable of transporting adenine, and ENT4 also transports adenine at acidic pH. They are also broadly expressed with ENT3 displaying high expression in the placenta and ENT4 in the heart6,7.
As mentioned above, nucleosides have a variety of cellular/physiological functions suggesting that transporters responsible for their trafficking may also have functional attributes. Indeed, ENT1 plays a role in proliferation and therefore is responsible for the constitutive trafficking of nucleosides1.
There is no evidence that nucleoside transporters are directly involved in pathophysiologies, but they are clinically significant. For example, nucleoside transporters are responsible for the cellular uptake of a number of nucleoside-derived anticancer drugs1.
Species reactivity key:
Anti-ENT2 (SLC29A2) Antibody (#ANT-052) is a highly specific antibody directed against an epitope of the rat equilibrative nucleoside transporter 2. The antibody can be used in western blot, immunohistochemistry, and immunocytochemistry applications. It has been designed to recognize ENT2 from rat, mouse, and human samples.