Rapid Regulation of Human Multidrug and Extrusion Transporters hMATE1 and hMATE2K

Abstract

Vectorial transport of organic cations (OCs) in renal proximal tubules is mediated by sequential action of human OC transporter 2 (hOCT2) and human multidrug and toxic extrusion protein 1 and 2K (hMATE1 and hMATE2K), expressed in the basolateral (hOCT2) and luminal (hMATE1 and hMATE2K) plasma membranes, respectively. It is well known that hOCT2 activity is subjected to rapid regulation by several signaling pathways, suggesting that renal OC secretion may be acutely adapted to physiological requirements. Therefore, in this work, the acute regulation of hMATEs stably expressed in human embryonic kidney cells was characterized using the fluorescent substrate 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP+) as a marker. A specific regulation of ASP+ transport by hMATE1 and hMATE2K measured in uptake and efflux configurations was observed. In the example of hMATE1 efflux reduction by inhibition of casein kinase II, it was also shown that this regulation is able to modify transcellular transport of ASP+ in Madin–Darby canine kidney II cells expressing hOCT2 and hMATE1 on the basolateral and apical membrane domains, respectively. The activity of hMATEs can be rapidly regulated by some intracellular pathways, which sometimes are common to those found for hOCTs. Interference with these pathways may be important to regulate renal secretion of OCs.

Properties of Transport Mediated by the Human Organic Cation Transporter 2 Studied in a Polarized Three-Dimensional Epithelial Cell Culture Model

“…The MDCK cells are a very important system for studying epithelial polarization [34]. Indeed, there are several works using MDCK cells as the expression system for hOCT2 and other organic cation transporters [35][36][37]. Usually, MDCK cells are cultured on filters to allow distinct experimental access to basolateral and apical membrane domain compartments.…”

“…In further experiments, acute regulation of the ASP + uptake (1 and 4 µM ASP + for hOCT2-HEK and hOCT2-MDCK cysts, respectively) by short-time incubation (10 min) with 10 µM aminogenistein, 5 µM calmidazolium or 10 µM TBBz as inhibitors of p56 lck tyrosine kinase, Ca 2+ -calmodulin or CKII, respectively, was measured. These inhibitors at these concentrations were chosen because they had already been demonstrated to be effective in regulating hOCT2 activity [37,56]. Solvents (DMSO or ethanol) at the concentration used in the regulation experiments did not change the ASP + uptake (not shown).…”

Protein Kinases and Cross-talk between Post-translational Modifications in the Regulation of Drug Transporters

“…When the efflux function of MATE was analyzed, it was found that CK2 inhibitor reduced function of MATE1 and the effect of TBBz on MATE2 disappeared, which is in strong contrast to its dramatic up-regulation effect on the uptake function of the transporters, and it was proposed that TBBz may stabilize MATEs in an uptake configuration. Additionally, activators of PKA (forskolin) and PKC (1,2-dioctanoyl-sn-glycerol, DOG) significantly reduced MATE2K efflux function, implicating a regulatory role of these kinases in the process (Kantauskaitė et al, 2020).…”

Regulation Mechanisms of Expression and Function of Organic Cation Transporter 1

“…Both in the liver and at least in the rodent kidneys, OCT1 mediates the first step of organic cation secretion, that is, the uptake of substrates into hepatocytes and into cells of the renal proximal tubules, respectively. For this reason, it should be investigated whether a regulation pathway able to stimulate the second step of secretion process, that is, the excretion of organic cations into the bile and urine, by, for example, the multidrug and toxin extrusion proteins (MATEs) ( Kantauskaite et al, 2020 ), can work together with OCT regulation to globally modulated hepatic and renal substrate secretion.…”