Lateral opening site of human oligopeptide transporter 2 plays a key role in the interaction with polymyxins

Multidrug-resistant bacteria, such as Gram-negative pathogens, represent a pressing global health concern, with polymyxins currently serving as the last-resort treatment option. However, their clinical application is hindered by nephrotoxicity. The human oligopeptide transporter 2 (hPepT2) plays a crucial role in the reabsorption of polymyxins within renal cells, which in turn contributes to the drug's nephrotoxic effects.

While the molecular basis of the hPepT2-polymyxin interaction remains unclear, this research aimed to elucidate this relationship through a combination of computational, chemical, and cell biology techniques.

Bioinformatic modeling suggested an outward-facing structure of hPepT2 and identified the lateral opening as the primary site of polymyxin binding, particularly involving residues E214, D215, D317, D342, and E622. Further validation via transporter mutagenesis and molecular analyses confirmed the critical role of D215 in polymyxin binding, while other residues were found to influence transporter turnover and/or expression.

To address the issue of nephrotoxicity, researchers synthesized polymyxin analogs with modifications at key positions Dab1, Dab3, Dab5, and Dab9. Their findings revealed that alanine substitution at Dab3 reduced the interaction between hPepT2 and polymyxins, while simultaneously maintaining antibacterial efficacy.

The implications of these findings are significant, as they suggest that understanding the structure-interaction relationship between hPepT2 and polymyxins could pave the way for the development of safer, more effective lipopeptide antibiotics. This proof-of-concept study highlights the potential of the hPepT2-polymyxin SIR model as a promising strategy in the fight against drug-resistant infections and their associated toxicities.