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Updated: Mar 31, 2026
Measuring Peptide Translocation into Large Unilamellar Vesicles
Published on: January 27, 2012
Human oligopeptide transporter 2 (PEPT2) mediates cellular uptake of polymyxins
Xiaoxi Lu1, Ting Chan1, Chenghao Xu1
1Faculty of Pharmacy, The University of Sydney, Camperdown, NSW 2006, Australia.
Objectives:
Polymyxins are a last-line therapy to treat MDR Gram-negative bacterial infections. Nephrotoxicity is the dose-limiting factor for polymyxins and recent studies demonstrated significant accumulation of polymyxins in renal tubular cells. However, little is known about the mechanism of polymyxin uptake into these cells. Oligopeptide transporter 2 (PEPT2) is a solute carrier transporter (SLC) expressed at the apical membrane of renal proximal tubular cells and facilitates drug reabsorption in the kidney. In this study, we examined the role of PEPT2 in polymyxin uptake into renal tubular cells.
Methods:
We investigated the inhibitory effects of colistin and polymyxin B on the substrate uptake mediated through 15 essential SLCs in overexpressing HEK293 cells. The inhibitory potency of both polymyxins on PEPT2-mediated substrate uptake was measured. Fluorescence imaging was employed to investigate PEPT2-mediated uptake of the polymyxin fluorescent probe MIPS-9541 and a transport assay was conducted with MIPS-9541 and [(3)H]polymyxin B1.
Results:
Colistin and polymyxin B potently inhibited PEPT2-mediated [(3)H]glycyl-sarcosine uptake (IC50 11.4 ± 3.1 and 18.3 ± 4.2 μM, respectively). In contrast, they had no or only mild inhibitory effects on the transport activity of the other 14 SLCs evaluated. MIPS-9541 potently inhibited PEPT2-mediated [(3)H]glycyl-sarcosine uptake (IC50 15.9 μM) and is also a substrate of PEPT2 (Km 74.9 μM). [(3)H]polymyxin B1 was also significantly taken up by PEPT2-expressing cells (Km 87.3 μM).
Conclusions:
Our study provides the first evidence of PEPT2-mediated uptake of polymyxins and contributes to a better understanding of the accumulation of polymyxins in renal tubular cells.
Insights
This study reveals that the oligopeptide transporter 2 (PEPT2) mediates the uptake of polymyxins, last-line antibiotics, into renal tubular cells. This finding helps explain polymyxin accumulation in the kidneys, a key factor in their toxicity.
Area of Science:
- Pharmacology
- Nephrology
- Molecular Biology
Background:
- Polymyxins are critical last-line antibiotics for multidrug-resistant Gram-negative bacterial infections.
- Nephrotoxicity is a significant dose-limiting side effect of polymyxin therapy.
- Polymyxin accumulation in renal tubular cells is observed, but the uptake mechanism remains unclear.
Purpose of the Study:
- To investigate the role of oligopeptide transporter 2 (PEPT2) in the uptake of polymyxins into renal tubular cells.
- To elucidate the mechanism underlying polymyxin accumulation in the kidney.
Main Methods:
- Evaluated the inhibitory effects of colistin and polymyxin B on substrate uptake via 15 solute carrier (SLC) transporters in HEK293 cells.
- Measured the inhibitory potency of polymyxins on PEPT2-mediated substrate uptake.
- Utilized fluorescence imaging and transport assays with a polymyxin probe (MIPS-9541) and radiolabeled polymyxin B1 to assess PEPT2-mediated uptake.
Main Results:
- Colistin and polymyxin B potently inhibited PEPT2-mediated uptake of [(3)H]glycyl-sarcosine (IC50 values 11.4 and 18.3 μM, respectively).
- These polymyxins showed minimal inhibition of other tested SLC transporters.
- The polymyxin probe MIPS-9541 and [(3)H]polymyxin B1 were confirmed as substrates of PEPT2, with significant uptake observed in PEPT2-expressing cells.
Conclusions:
- This study provides the first evidence that PEPT2 mediates polymyxin uptake into renal tubular cells.
- Understanding PEPT2's role in polymyxin uptake is crucial for managing nephrotoxicity and optimizing antibiotic therapy.
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