Individual PKC-Phosphorylation Sites in Organic Cation Transporter 1 Determine Substrate Selectivity and Transport Regulation

Ciarimboli, Giuliano; Koepsell, Hermann; Iordanova, Mariya; Gorboulev, Valentin; Dürner, Brigitte; Lang, Detlef; Edemir, Bayram; Schröter, Rita; Le, Truc Van; Schlatter, Eberhard

doi:10.1681/asn.2004040256

Cited by 86 publications

(72 citation statements)

References 33 publications

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“…Structural studies show that N-glycosylation can affect the ␤-turn content of proteins, and perhaps the formation of covalent and hydrogen bonds in backbone and side-chain atoms (25). Ciarimboli et al (8) proposed that the intracellular loop between transmembrane domains 6 and 7 of OCT1 may also modulate the structure of the binding region. More in depth studies are required to determine how the intracellular and extracellular loops influence the organization of amino acids associated with interaction of substrate with OCTs.…”

Section: Discussionmentioning

confidence: 99%

Functional influence ofN-glycosylation in OCT2-mediated tetraethylammonium transport

Pelis¹,

Suhre²,

Wright³

2006

American Journal of Physiology-Renal Physiology

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Pelis, Ryan M., Wendy M. Suhre, and Stephen H. Wright. Functional influence of N-glycosylation in OCT2-mediated tetraethylammonium transport. Am J Physiol Renal Physiol 290: F1118 -F1126, 2006. First published December 20, 2005 doi:10.1152/ajprenal.00462.2005.-OCT2, an organic cation transporter critical for removal of many drugs and toxins from the body, contains consensus sites for N-glycosylation at amino acid position 71, 96, and 112. However, the extent to which these sites are glycosylated by the cell, and the influence glycosylation has on OCT2 function, remains unknown. To address these issues, the acquisition of N-glycosylation was disrupted by mutating the amino acid asparagine (N) to glutamine (Q) at these sites in the rabbit ortholog of OCT2, which was expressed in Chinese hamster ovary cells. Disruption of N-glycosylation followed by Western blotting indicated that each site is indeed glycosylated and that OCT2 contains no other sites of Nglycosylation. Plasma membrane expression (determined by surface biotinylation) of the N112Q mutant, but not N71Q or N96Q mutants, was fourfold lower than that of wild-type OCT2, and unglycosylated OCT2 (N71Q/N96Q/N112Q) was sequestered in an unidentified intracellular compartment. The N71Q, N96Q, and N112Q mutants had a higher affinity (ϳ2-fold) for tetraethylammonium (TEA). Maximum transport rate was reduced in the N96Q (3-fold) and N112Q (5-fold) mutants, but not the N71Q mutant, and unglycosylated OCT2 failed to transport TEA (associated with its absence in the plasma membrane). Whereas the reduction in maximum transport rate of the N112Q mutant is consistent with its reduced plasma membrane expression, the lower rate of the N96Q mutant, which appeared to traffic properly, suggests that glycosylation at N96 increases the transporter turnover number. SLC22A2; organic cation; rabbit ORGANIC CATION TRANSPORTERS (OCTs) in the SLC22A gene family transport a variety of organic cations (OCs), including clinically important therapeutics (e.g., cimetidine) and environmental toxins (e.g., nicotine). Three OCTs (OCT1, OCT2, and OCT3) have been cloned, and each appears to be restricted to the basolateral membrane of barrier epithelia (32). In the renal proximal tubule, an important site for controlling plasma levels of OCs, all three OCTs are expressed and provide an essential pathway for OC uptake, the first step in tubular secretion (32). Depending on the prevailing set of electrical and chemical gradients, OCT-mediated transport can occur either via electrogenic facilitated diffusion (i.e., driven by the negative membrane potential) or OC/OC exchange (4, 5, 13). In humans, OCT2 (SLC22A2) has been postulated to be the greatest contributor to tubular OC secretion since its expression (as indicated by mRNA and protein levels) predominates over that of OCT1 and OCT3 (19). However, both OCT1 and OCT3 may play significant roles in the renal handling of select OCs (e.g., those transported inefficiently by OCT2) (32, 34). OCT1, 2, and 3 belong to a larger family of solute carr...

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Section: Discussionmentioning

confidence: 99%

Functional influence ofN-glycosylation in OCT2-mediated tetraethylammonium transport

Pelis¹,

Suhre²,

Wright³

2006

American Journal of Physiology-Renal Physiology

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“…Polymorphisms of genes encoding proteins involved in the metabolism and subsequent renal elimination of drugs have been described and are correlated with various levels of drug sensitivity. Specific to the (29). In the future, more information regarding how patients differ in the function and regulation of channels, transporters, and carriers that regulate elimination of drugs and other compounds cleared by the kidney will be brought to light.…”

Section: Risk Factors For Nephrotoxicitymentioning

confidence: 99%

Renal Vulnerability to Drug Toxicity

Perazella¹

2009

Clinical Journal of the American Society of Nephrology

342

267

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Drug-induced kidney disease occurs primarily in patients with underlying risk factors. A number of factors enhance the vulnerability of the kidney to the nephrotoxic effects of drugs and toxins. They are broadly categorized as patient-specific, kidney-related, and drug-related factors. One, two, or all three of the factor categories can act to promote various forms of renal injury. Importantly, all compartments of the kidney can be affected and result in one or more classic clinical renal syndromes. These include acute kidney injury, various tubulopathies, proteinuric renal disease, and chronic kidney disease. Recognizing risk factors that increase renal vulnerability to drug-induced kidney disease is the first step in reducing the renal complications of drugs and toxins.

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“…13,14 Post-transcriptional regulation of OCT-1 by phosphorylation status 15 and such compounds as protein kinase A (PKA), Src-like p56, and CaM also have been demonstrated. [16][17][18] Both quantitative and qualitative changes in OCT-1 may have an impact on imatinib uptake. We hypothesized that a functional assay of imatinib uptake into patient cells may provide the most clinically predictive assay of OCT-1 function.…”

Section: Introductionmentioning

confidence: 99%

Most CML patients who have a suboptimal response to imatinib have low OCT-1 activity: higher doses of imatinib may overcome the negative impact of low OCT-1 activity

White

Saunders

Dang

et al. 2007

Blood

298

216

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Interpatient variability in intracellular uptake and retention (IUR) of imatinib may be due to variable function of the OCT-1 influx pump. OCT-1 activity was measured in pretherapy blood from chronic myeloid leukemia (CML) patients by calculating the difference in IUR of [14C]-imatinib with and without OCT-1 inhibition. Of patients with higher than median (high) OCT-1 activity, 85% achieved major molecular response (MMR) by 24 months, versus 45% with no more than a median (low) OCT-1 activity. Assessing patients receiving 600 mg imatinib per day and those averaging fewer than 600 mg over 12 months of therapy revealed patients with high OCT-1 activity achieved excellent molecular response regardless of dose, whereas response of patients with low OCT-1 activity was highly dose dependent. Of patients with low OCT-1 activity who received fewer than 600 mg, 45% failed to achieve a 2-log reduction by 12 months, and 82% failed to achieve a MMR by 18 months, compared with 8% and 17% in the cohort with high OCT-1 activity and dose less than 600 mg/day (P = .017 and P = .022). OCT-1 activity is an important determinant of molecular response to imatinib, with predictive value closely linked to dose. This pretherapy assay identifies patients at greatest risk of suboptimal response where dose intensity is critical, and those likely to respond equally well to standard dose imatinib.

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Individual PKC-Phosphorylation Sites in Organic Cation Transporter 1 Determine Substrate Selectivity and Transport Regulation

Cited by 86 publications

References 33 publications

Functional influence ofN-glycosylation in OCT2-mediated tetraethylammonium transport

Functional influence ofN-glycosylation in OCT2-mediated tetraethylammonium transport

Renal Vulnerability to Drug Toxicity

Most CML patients who have a suboptimal response to imatinib have low OCT-1 activity: higher doses of imatinib may overcome the negative impact of low OCT-1 activity

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