Transport of antiviral 3'-deoxy-nucleoside drugs by recombinant human and rat equilibrative, nitrobenzylthioinosine (NBMPR)-insensitive (ENT2) nucleoside transporter proteins produced in Xenopus oocytes

Mol Membr Biol. Apr-Jun 2001;18(2):161-7. doi: 10.1080/09687680110048318.


In the present study, one has determined the relative role of plasma membrane equilibrative (Na+-independent) ENT nucleoside transport proteins (particularly ENT2) in the uptake of antiviral nucleoside analogues for comparison with the previously reported drug transport properties of concentrative (Na+-dependent) CNT nucleoside transport proteins. The human and rat nucleoside transport proteins hENT1, rENT1, hENT2 and rENT2 were produced in Xenopus oocytes and investigated for their ability to transport three 3'-deoxy-nucleoside analogues, ddC (2'3'-dideoxycytidine), AZT (3'-azido-3'-deoxythymidine) and ddI (2'3'-dideoxyinosine), used in human immunodeficiency virus (HIV) therapy. The results show, for the first time, that the ENT2 transporter isoform represents a mechanism for cellular uptake of these clinically important nucleoside drugs. Recombinant h/rENT2 transported ddC, ddI and AZT, whilst h/rENT1 transported only ddC and ddI. Relative to uridine, h/rENT2 mediated substantially larger fluxes of ddC and ddI than h/rENT1. Transplanting the amino-terminal half of rENT2 into rENT1 rendered rENT1 transport-positive for AZT and enhanced the uptake of both ddC and ddI, identifying this region as a major site of 3'-deoxy-nucleoside drug interaction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Anti-HIV Agents / metabolism*
  • Biological Transport
  • Didanosine / metabolism*
  • Equilibrative Nucleoside Transporter 1
  • Equilibrative-Nucleoside Transporter 2*
  • Humans
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Molecular Sequence Data
  • Oocytes
  • Rats
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Reverse Transcriptase Inhibitors / metabolism*
  • Xenopus laevis
  • Zalcitabine / metabolism*
  • Zidovudine / metabolism*


  • Anti-HIV Agents
  • Equilibrative Nucleoside Transporter 1
  • Equilibrative-Nucleoside Transporter 2
  • Membrane Transport Proteins
  • Recombinant Fusion Proteins
  • Reverse Transcriptase Inhibitors
  • SLC29A1 protein, human
  • SLC29A2 protein, human
  • Slc29a1 protein, rat
  • Slc29a2 protein, rat
  • Zidovudine
  • Zalcitabine
  • Didanosine