Identification of a novel sodium-coupled oligopeptide transporter (SOPT2) in mouse and human retinal pigment epithelial cells

Paresh P. Chothe, Santoshanand V. Thakkar, Jaya P. Gnana-Prakasam, Sudha Ananth, David R. Hinton, Ram Kannan, Sylvia B. Smith, Pamela M. Martin, Vadivel Ganapathy

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

PURPOSE. A sodium-coupled oligopeptide transporter (SOPT1) was described originally in ARPE-19 cells. The transporter is inducible by HIV-1 Tat. Recent studies of conjunctival epithelial cells have identified a second oligopeptide transporter (SOPT2). This study was conducted to determine whether the newly discovered SOPT2 is expressed in ARPE-19 cells, to examine whether the new transporter is also inducible by HIV-1 Tat, and to find out whether this transporter is expressed in primary RPE cells. METHODS. The transport activity of SOPT2 was monitored in control and Tat-expressing ARPE-19 cells and in primary mouse and human fetal RPE cells by the uptake of the synthetic opioid peptide DADLE ((H-Tyr-D-Ala-Gly-Phe-D-Leu-OH) and by its susceptibility to inhibition by small peptides. Substrate selectivity was examined by competition studies and kinetic parameters were determined by saturation analysis. RESULTS. ARPE-19 cells express DADLE uptake activity that is inhibited by small peptides, indicating expression of SOPT2 in these cells. The activity of SOPT2 is induced by HIV-1 Tat. SOPT2 accepts endogenous and synthetic opioid peptides as substrates, but nonpeptide opiate antagonists are excluded. An 11-amino-acid HIV-1 Tat peptide also serves as a high-affinity substrate for the transporter. Primary cultures of mouse and human fetal RPE cells express SOPT2. The transporter is partially Na +-dependent with comparable substrate selectivity and inhibitor specificity in the presence and absence of Na +. CONCLUSIONS. ARPE-19 cells as well as primary mouse and human fetal RPE cells express the newly discovered oligopeptide transporter SOPT2, and the transporter is induced by HIV-1 Tat in ARPE-19 cells.

Original languageEnglish (US)
Pages (from-to)413-420
Number of pages8
JournalInvestigative Ophthalmology and Visual Science
Volume51
Issue number1
DOIs
StatePublished - Jan 1 2010

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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