scholarly journals Cysteine residues in the organic anion transporter mOAT1

2004 ◽  
Vol 380 (1) ◽  
pp. 283-287 ◽  
Author(s):  
Kunihiko TANAKA ◽  
Fanfan ZHOU ◽  
Kogo KUZE ◽  
Guofeng YOU
Keyword(s):  
Organic Anion ◽  
Cysteine Residue ◽  
The Body ◽  
Organic Anion Transporter ◽  
Site Directed Mutagenesis ◽  
Cysteine Residues ◽  
Transport Activity ◽  
Anion Transporters ◽  
Anion Transporter

Mouse organic anion transporter 1 (mOAT1) belongs to a family of organic anion transporters, which play critical roles in the body disposition of clinically important drugs, including anti-HIV therapeutics, anti-tumour drugs, antibiotics, anti-hypertensives and anti-inflammatories. mOAT1-mediated transport of organic anion PAH (p-aminohippurate) in HeLa cells was inhibited by the cysteine-modifying reagent PCMBS (p-chloromercuribenzenesulphonate). Therefore the role of cysteine residues in the function of mOAT1 was examined by site-directed mutagenesis. All 13 cysteine residues in mOAT1 were replaced by alanine, singly or in combination. Single replacement of these residues had no significant effect on mOAT1-mediated PAH transport, indicating that no individual cysteine residue is necessary for function. Multiple replacements at a C-terminal region (C335/379/427/434A; Cys335/379/427/434→Ala) resulted in a substantial decrease in transport activity. A simultaneous replacement of all 13 cysteine residues (C-less) led to a complete loss of transport function. The decreased or lack of transport activity of the mutants C335/379/427/434A and C-less was due to the impaired trafficking of the mutant transporters to the cell surface. These results suggest that although cysteine residues are not required for function in mOAT1, their presence appears to be important for the targeting of the transporter to the plasma membrane. We also showed that, although all cysteine mutants of mOAT1 were sensitive to the inhibition by PCMBS, C49A was less sensitive than the wild-type mOAT1, suggesting that the modification of Cys49 may play a role in the inhibition of mOAT1 by PCMBS.

scholarly journals Mutational analysis of histidine residues in human organic anion transporter 4 (hOAT4)

2004 ◽  
Vol 384 (1) ◽  
pp. 87-92 ◽  
Author(s):  
Fanfan ZHOU ◽  
Zui PAN ◽  
Jianjie MA ◽  
Guofeng YOU
Keyword(s):  
Mutational Analysis ◽  
Organic Anion ◽  
The Body ◽  
Organic Anion Transporter ◽  
Site Directed Mutagenesis ◽  
Cell Surface Expression ◽  
Transport Activity ◽  
Membrane Expression ◽  
Histidine Residues ◽  
Anion Transporter

Human organic anion transporter 4 (hOAT4) belongs to a family of organic anion transporters which play critical roles in the body disposition of clinically important drugs, including anti-HIV therapeutics, antitumour drugs, antibiotics, anti-hypertensives and anti-inflammatories. hOAT4-mediated transport of the organic anion oestrone sulphate in COS-7 cells was inhibited by the histidine-modifying reagent DEPC (diethyl pyrocarbonate). Therefore the role of histidine residues in the function of hOAT4 was examined by site-directed mutagenesis. All five histidine residues of hOAT4 were converted into alanine, singly or in combination. Single replacement of His-47, or simultaneous replacement of His-47/52/83 or His-47/52/83/305/469 (H-less) led to a 50–80% decrease in transport activity. The decreased transport activity of these mutants was correlated with a decreased amount of cell-surface expression, although the total cell expression of these mutants was similar to that of wild-type hOAT4. These results suggest that mutation at positions 47, 47/52/83 and 47/52/83/305/469 impaired membrane expression rather than function. We also showed that, although most of the histidine mutants of hOAT4 were sensitive to inhibition by DEPC, H469A (His-469→Ala) was completely insensitive to inhibition by this reagent. Therefore modification of His-469 is responsible for the inhibition of hOAT4 by DEPC.

scholarly journals Nedd4-2 but not Nedd4-1 is critical for protein kinase C-regulated ubiquitination, expression, and transport activity of human organic anion transporter 1

2016 ◽  
Vol 310 (9) ◽  
pp. F821-F831 ◽  
Author(s):  
Da Xu ◽  
Haoxun Wang ◽  
Qiang Zhang ◽  
Guofeng You
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cell Surface ◽  
Organic Anion ◽  
The Body ◽  
Organic Anion Transporter ◽  
Transport Activity ◽  
Kinase C ◽  
Anion Transporter ◽  
In Cells

Human organic anion transporter 1 (hOAT1) expressed at the membrane of the kidney proximal tubule cells mediates the body disposition of a diverse array of clinically important drugs, including anti-HIV therapeutics, antitumor drugs, antibiotics, antihypertensives, and antiinflammatories. Therefore, understanding the regulation of hOAT1 will provide significant insights into kidney function and dysfunction. We previously established that hOAT1 transport activity is inhibited by activation of protein kinase C (PKC) through accelerating hOAT1 internalization from cell surface into intracellular endosomes and subsequent degradation. We further established that PKC-induced hOAT1 ubiquitination is an important step preceding hOAT1 internalization. In the current study, we identified two closely related E3 ubiquitin ligases, neural precursor cell expressed, developmentally downregulated 4-1 and 4-2 (Nedd4-1 and Nedd4-2), as important regulators for hOAT1: overexpression of Nedd4-1 or Nedd4-2 enhanced hOAT1 ubiquitination, reduced the hOAT1 amount at the cell surface, and suppressed hOAT1 transport activity. In further exploring the relationship among PKC, Nedd4-1, and Nedd4-2, we discovered that PKC-dependent changes in hOAT1 ubiquitination, expression, and transport activity were significantly blocked in cells transfected with the ligase-dead mutant of Nedd4-2 (Nedd4-2/C821A) or with Nedd4-2-specific siRNA to knockdown endogenous Nedd4-2 but not in cells transfected with the ligase-dead mutant of Nedd4-1 (Nedd4-1/C867S) or with Nedd4-1-specific siRNA to knockdown endogenous Nedd4-1. In conclusion, this is the first demonstration that both Nedd4-1 and Nedd4-2 are important regulators for hOAT1 ubiquitination, expression, and function. Yet they play distinct roles, as Nedd4-2 but not Nedd4-1 is a critical mediator for PKC-regulated hOAT1 ubiquitination, expression, and transport activity.

scholarly journals Cysteine residues in the Na+/dicarboxylate co-transporter, NaDC-1

1999 ◽  
Vol 344 (1) ◽  
pp. 205-209 ◽  
Author(s):  
Ana M. PAJOR ◽  
Sally J. KRAJEWSKI ◽  
Nina SUN ◽  
Rama GANGULA
Keyword(s):  
Protein Trafficking ◽  
Direct Relationship ◽  
Transmembrane Domain ◽  
Cysteine Residue ◽  
Site Directed Mutagenesis ◽  
Cysteine Residues ◽  
Directed Mutagenesis ◽  
Transport Activity ◽  
Specific Reagent

The role of cysteine residues in the Na+/dicarboxylate co-transporter (NaDC-1) was tested using site-directed mutagenesis. The transport activity of NaDC-1 was not affected by mutagenesis of any of the 11 cysteine residues, indicating that no individual cysteine residue is necessary for function. NaDC-1 is sensitive to inhibition by the impermeant cysteine-specific reagent, p-chloromercuribenzenesulphonate (pCMBS). The pCMBS-sensitive residues in NaDC-1 are Cys-227, found in transmembrane domain 5, and Cys-476, located in transmembrane domain 9. Although cysteine residues are not required for function in NaDC-1, their presence appears to be important for protein stability or trafficking to the plasma membrane. There was a direct relationship between the number of cysteine residues, regardless of location, and the transport activity and expression of NaDC-1. The results indicate that mutagenesis of multiple cysteine residues in NaDC-1 may alter the shape or configuration of the protein, leading to alterations in protein trafficking or stability.

Human organic anion transporter 1B1 and 1B3 function as bidirectional carriers and do not mediate GSH-bile acid cotransport

2007 ◽  
Vol 293 (1) ◽  
pp. G271-G278 ◽  
Author(s):  
Chitrawina Mahagita ◽  
Steven M. Grassl ◽  
Pawinee Piyachaturawat ◽  
Nazzareno Ballatori
Keyword(s):  
Bile Acid ◽  
Transport Mechanism ◽  
Organic Anion ◽  
Large Family ◽  
Organic Anion Transporter ◽  
Xenopus Laevis Oocytes ◽  
Facilitated Diffusion ◽  
Transport Activity ◽  
Estrone Sulfate ◽  
Anion Transporter

Organic anion transporting polypeptides (OATP/ SLCO) are generally believed to function as electroneutral anion exchangers, but direct evidence for this contention has only been provided for one member of this large family of genes, rat Oatp1a1/Oatp1 ( Slco1a1). In contrast, a recent study has indicated that human OATP1B3/OATP-8 ( SLCO1B3) functions as a GSH-bile acid cotransporter. The present study examined the transport mechanism and possible GSH requirement of the two members of this protein family that are expressed in relatively high levels in the human liver, OATP1B3/OATP-8 and OATP1B1/OATP-C ( SLCO1B1). Uptake of taurocholate in Xenopus laevis oocytes expressing either OATP1B1/OATP-C, OATP1B3/OATP-8, or polymorphic forms of OATP1B3/OATP-8 (namely, S112A and/or M233I) was cis-inhibited by taurocholate and estrone sulfate but was unaffected by GSH. Likewise, taurocholate and estrone sulfate transport were trans-stimulated by estrone sulfate and taurocholate but were unaffected by GSH. OATP1B3/OATP-8 also did not mediate GSH efflux or GSH-taurocholate cotransport out of cells, indicating that GSH is not required for transport activity. In addition, estrone sulfate uptake in oocytes microinjected with OATP1B3/OATP-8 or OATP1B1/OATP-C cRNA was unaffected by depolarization of the membrane potential or by changes in pH, suggesting an electroneutral transport mechanism. Overall, these results indicate that OATP1B3/OATP-8 and OATP1B1/OATP-C most likely function as bidirectional facilitated diffusion transporters and that GSH is not a substrate or activator of their transport activity.

scholarly journals SLCO4A1-AS1 Facilitates the Malignant Phenotype via miR-149-5p/STAT3 Axis in Gastric Cancer Cells

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qing Li ◽  
Dachuan Zhang ◽  
Hui Wang ◽  
Jun Xie ◽  
Lei Peng ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Cancer Cells ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Gastric Cancer Cells ◽  
Anion Transporter ◽  
Transporter Family ◽  
Cancer Tissues ◽  
Development Of Gastric Cancer

Solute carrier organic anion transporter family member 4A1 (SLCO4A1-AS1), a newly discovered lncRNA, may exert effects in tumors. Since its role in gastric cancer remains obscure, we sought to explore the mechanism of SLCO4A1-AS1 in gastric cancer. The relationship among SLCO4A1-AS1, miR-149-5p, and STAT3 was detected by bioinformatics, dual luciferase analysis, and Pearson’s test, and the expressions of these genes were determined by quantitative real-time PCR and Western blot. Moreover, CCK-8, flow cytometry, wound healing assay, and Transwell analysis were performed to verify the function of SLCO4A1-AS1 in gastric cancer. Rescue experiments were used to detect the role of miR-149-5p. The expressions of SLCO4A1-AS1 and STAT3 were increased, while the expression of miR-149-5p was suppressed in gastric cancer tissues and cell lines. In addition, STAT3 expression was negatively correlated with miR-149-5p expression but was positively correlated with SLCO4A1-AS1 expression. Overexpression of SLCO4A1-AS1 promoted cell viability, migration, invasion, and STAT3 expression but suppressed apoptosis, while knockdown of SLCO4A1-AS1 had the opposite effect. SLCO4A1-AS1 bound to miR-149-5p and targeted STAT3. Moreover, miR-149-5p mimic inhibited the malignant development of gastric cancer cells and obviously reversed the function of SLCO4A1-AS1 overexpression. Our research reveals that abnormally increased SLCO4A1-AS1 expression may be an important molecular mechanism in the development of gastric cancer.

scholarly journals Renal secretion of hydrochlorothiazide involves organic anion transporter 1/3, organic cation transporter 2, and multidrug and toxin extrusion protein 2-K

2019 ◽  
Vol 317 (4) ◽  
pp. F805-F814
Author(s):  
Jia Yin ◽  
David J. Wagner ◽  
Bhagwat Prasad ◽  
Nina Isoherranen ◽  
Kenneth E. Thummel ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Organic Cation ◽  
Organic Anion ◽  
Organic Cation Transporter ◽  
Tubular Secretion ◽  
Organic Anion Transporter ◽  
Anion Transporters ◽  
Anion Transporter ◽  
Organic Cation Transporter 2 ◽  
Toxin Extrusion

Hydrochlorothiazide (HCTZ) is the most widely used thiazide diuretic for the treatment of hypertension either alone or in combination with other antihypertensives. HCTZ is mainly cleared by the kidney via tubular secretion, but the underlying molecular mechanisms are unclear. Using cells stably expressing major renal organic anion and cation transporters [human organic anion transporter 1 (hOAT1), human organic anion transporter 3 (hOAT3), human organic cation transporter 2 (hOCT2), human multidrug and toxin extrusion 1 (hMATE1), and human multidrug and toxin extrusion 2-K (hMATE2-K)], we found that HCTZ interacted with both organic cation and anion transporters. Uptake experiments further showed that HCTZ is transported by hOAT1, hOAT3, hOCT2, and hMATE2-K but not by hMATE1. Detailed kinetic analysis coupled with quantification of membrane transporter proteins by targeted proteomics revealed that HCTZ is an excellent substrate for hOAT1 and hOAT3. The apparent affinities ( Km) for hOAT1 and hOAT3 were 112 ± 8 and 134 ± 13 μM, respectively, and the calculated turnover numbers ( kcat) were 2.48 and 0.79 s−1, respectively. On the other hand, hOCT2 and hMATE2-K showed much lower affinity for HCTZ. The calculated transport efficiency ( kcat/ Km) at the single transporter level followed the rank order of hOAT1> hOAT3 > hOCT2 and hMATE2-K, suggesting a major role of organic anion transporters in tubular secretion of HCTZ. In vitro inhibition experiments further suggested that HCTZ is not a clinically relevant inhibitor for hOAT1 or hOAT3. However, strong in vivo inhibitors of hOAT1/3 may alter renal secretion of HCTZ. Together, our study elucidated the molecular mechanisms underlying renal handling of HCTZ and revealed potential pathways involved in the disposition and drug-drug interactions for this important antihypertensive drug in the kidney.

scholarly journals Human organic anion transporter 2 is distinct from organic anion transporters 1 and 3 with respect to transport function

2015 ◽  
Vol 309 (10) ◽  
pp. F843-F851 ◽  
Author(s):  
Maja Henjakovic ◽  
Yohannes Hagos ◽  
Wolfgang Krick ◽  
Gerhard Burckhardt ◽  
Birgitta C. Burckhardt
Keyword(s):  
Organic Anion ◽  
Organic Anion Transporter ◽  
Substrate Uptake ◽  
Organic Anion Transporters ◽  
Counter Anion ◽  
Anion Transporters ◽  
Anion Transporter ◽  
293 Cells ◽  
High K ◽  
Resistance Protein

Phylogentically, organic anion transporter (OAT)1 and OAT3 are closely related, whereas OAT2 is more distant. Experiments with human embryonic kidney-293 cells stably transfected with human OAT1, OAT2, or OAT3 were performed to compare selected transport properties. Common to OAT1, OAT2, and OAT3 is their ability to transport cGMP. OAT2 interacted with prostaglandins, and cGMP uptake was inhibited by PGE2 and PGF2α with IC50 values of 40.8 and 12.7 μM, respectively. OAT1 (IC50: 23.7 μM), OAT2 (IC50: 9.5 μM), and OAT3 (IC50: 1.6 μM) were potently inhibited by MK571, an established multidrug resistance protein inhibitor. OAT2-mediated cGMP uptake was not inhibited by short-chain monocarboxylates and, as opposed to OAT1 and OAT3, not by dicarboxylates. Consequently, OAT2 showed no cGMP/glutarate exchange. OAT1 and OAT3 exhibited a pH and a Cl− dependence with higher substrate uptake at acidic pH and lower substrate uptake in the absence of Cl−, respectively. Such pH and Cl− dependencies were not observed with OAT2. Depolarization of membrane potential by high K+ concentrations in the presence of the K+ ionophore valinomycin left cGMP uptake unaffected. In addition to cGMP, OAT2 transported urate and glutamate, but cGMP/glutamate exchange could not be demonstrated. These experiments suggest that OAT2-mediated cGMP uptake does not occur via exchange with monocarboxylates, dicarboxylates, and hydroxyl ions. The counter anion for electroneutral cGMP uptake remains to be identified.

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