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Regulation of human organic cation transporter hOCT2 by PKA, PI3K, and calmodulin-dependent kinases

2003; American Physical Society; Volume: 284; Issue: 2 Linguagem: Inglês

10.1152/ajprenal.00251.2002

1931-857X

Ibrahim Çetinkaya, Giuliano Ciarimboli, Gülay Yalçinkaya, Thomas Mehrens, Ana Velić, Jochen R. Hirsch, Valentin Gorboulev, Hermann Koepsell, Eberhard Schlatter,

Amino Acid Enzymes and Metabolism

Properties and regulation of the human organic cation (OC) transporter type 2 (hOCT2) expressed in HEK-293 cells were extensively characterized using the fluorescent OC 4-[4-(dimethylamino)styryl]- N-methylpyridinium (ASP + ). ASP + uptake was electrogenic and inhibited by TPA + (EC 50 = 2.7 μM), tetraethylammonium (EC 50 = 35 μM), cimetidine (EC 50 = 36 μM), or quinine (EC 50 = 6.7 μM). Stimulation with carbachol or ATP decreased initial uptake by 44 ± 3 ( n = 14) and 34 ± 4% ( n = 21), respectively, independently of PKC but dependent on phosphatidylinositol 3-kinase (PI3K). PKA stimulation decreased uptake by 18 ± 4% ( n = 40). Inhibition of calmodulin (CaM), Ca 2+ /CaM-dependent kinase II, or myosin light chain kinase decreased uptake by 63 ± 2 ( n = 15), 40 ± 4 ( n = 30), and 31 ± 4% ( n = 16), respectively. Inhibition of CaM resulted in a significant change in the EC 50 value for the inhibition of ASP + uptake by tetraethylammonium. In conclusion, we demonstrate that the hOCT2 is inhibited by PI3K and PKA and activated by a CaM-dependent signaling pathway, probably via a change in substrate affinity.