MPP+-Induced Changes in Cellular Impedance as a Measure for Organic Cation Transporter (SLC22A1-3) Activity and Inhibition

Int J Mol Sci. 2022 Jan 21;23(3):1203. doi: 10.3390/ijms23031203.


The organic cation transporters OCT1-3 (SLC22A1-3) facilitate the transport of cationic endo- and xenobiotics and are important mediators of drug distribution and elimination. Their polyspecific nature makes OCTs highly susceptible to drug-drug interactions (DDIs). Currently, screening of OCT inhibitors depends on uptake assays that require labeled substrates to detect transport activity. However, these uptake assays have several limitations. Hence, there is a need to develop novel assays to study OCT activity in a physiological relevant environment without the need to label the substrate. Here, a label-free impedance-based transport assay is established that detects OCT-mediated transport activity and inhibition utilizing the neurotoxin MPP+. Uptake of MPP+ by OCTs induced concentration-dependent changes in cellular impedance that were inhibited by decynium-22, corticosterone, and Tyrosine Kinase inhibitors. OCT-mediated MPP+ transport activity and inhibition were quantified on both OCT1-3 overexpressing cells and HeLa cells endogenously expressing OCT3. Moreover, the method presented here is a valuable tool to identify novel inhibitors and potential DDI partners for MPP+ transporting solute carrier proteins (SLCs) in general.

Keywords: MPP+; OCT; SLC22A1-3; label-free; transport; xCELLigence.

MeSH terms

  • 1-Methyl-4-phenylpyridinium / adverse effects
  • Biological Transport
  • Biological Transport, Active
  • Electric Impedance*
  • Gene Expression Regulation / drug effects*
  • HEK293 Cells
  • Herbicides / adverse effects
  • Humans
  • Organic Cation Transport Proteins / antagonists & inhibitors
  • Organic Cation Transport Proteins / genetics
  • Organic Cation Transport Proteins / metabolism*
  • Organic Cation Transporter 1 / antagonists & inhibitors
  • Organic Cation Transporter 1 / genetics
  • Organic Cation Transporter 1 / metabolism*
  • Organic Cation Transporter 2 / antagonists & inhibitors
  • Organic Cation Transporter 2 / genetics
  • Organic Cation Transporter 2 / metabolism*


  • Herbicides
  • Organic Cation Transport Proteins
  • Organic Cation Transporter 1
  • Organic Cation Transporter 2
  • SLC22A2 protein, human
  • solute carrier family 22 (organic cation transporter), member 3
  • 1-Methyl-4-phenylpyridinium