Effects of Single Nucleotide Polymorphism Ala270Ser (rs316019) on the Function and Regulation of hOCT2.

Frenzel Frenzel,Bauer Bauer,Schröter Schröter,Karst Karst,Ciarimboli Ciarimboli,Tzvetkov Tzvetkov,Köppen Köppen

doi:10.3390/biom9100578

Abstract

The human organic cation transporter 2 (hOCT2) is highly expressed in proximal tubules of the kidneys, where it plays an important role in the secretion of organic cations. Since many drugs are organic cations, hOCT2 has relevant pharmacological implications. The hOCT2 gene is polymorphic, and the nonsynonymous single nucleotide polymorphism (SNP) causing the substitution of alanine at position 270 of the protein sequence with serine (Ala270Ser) is present with high frequency in the human population. Therefore, Ala270Ser has potentially important pharmacologic consequences. Here, we analyzed the transport properties and rapid regulation of hOCT2 wildtype and hOCT2 Ala270Ser expressed in human embryonic kidney cells using real-time uptake measurements. Moreover, we compared the expression of hOCT2 in the plasma membrane determined by biotinylation experiments and the cellular transport and toxicity of cisplatin measured by inductively coupled plasma mass spectrometry and a viability test, respectively. The transport characteristics and regulation of the wildtype and mutated hOCT2 were very similar. Interestingly, a higher affinity of hOCT2 Ala270Ser for creatinine was observed. Compared with hOCT2 wildtype, the plasma membrane expression, cisplatin transport, and cisplatin-associated toxicity of hOCT2 Ala270Ser were significantly lower. In conclusion, these findings suggest that Ala270Ser has subtle but important effects on hOCT2 function, which are probably difficult to detect in studies with patients.

Highlights

The human organic cation transporter 2 (SLC22A2/hOCT2) is highly expressed on the basolateral membrane of renal proximal tubules [1]
(4.0 ± 1.0 and 4.9 ± 1.6 μM for hOCT2 WT and hOCT2 Ala270Ser, respectively) and Vmax (516 ± 23 and 484 ± 50 arbitrary units/μg protein s2 for hOCT2 WT and hOCT2 Ala270Ser, respectively) of
Intracellular cisplatin targets the DNA and the cellular anti-oxidant defenses, decreasing the cell resistance against oxidative stress and disturbing DNA processing, causing cell apoptosis. This toxicity impairs the tubular functions and manifests as acute kidney injury (AKI), which can progress to chronic kidney disease

Summary

Introduction

The human organic cation transporter 2 (SLC22A2/hOCT2) is highly expressed on the basolateral membrane of renal proximal tubules [1]. It mediates the uptake of organic cations into the cells, which is the first step in their renal secretion. Endogenous substances such as creatinine, dopamine, histamine, and serotonin, and exogenous substances such important drugs such as cimetidine and metformin belong to the class of organic cations [2]. Because of its high allele frequency of 12.7% in many populations [11], the single nucleotide polymorphism (SNP) rs316019 is of Biomolecules 2019, 9, 578; doi:10.3390/biom9100578 www.mdpi.com/journal/biomolecules

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