{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,28]],"date-time":"2026-07-28T14:13:22Z","timestamp":1785248002383,"version":"3.55.0"},"reference-count":41,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2023,10,14]],"date-time":"2023-10-14T00:00:00Z","timestamp":1697241600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"German Research Foundation","award":["491454339"],"award-info":[{"award-number":["491454339"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Chronic kidney disease (CKD) is a global health concern affecting millions worldwide. One of the critical challenges in CKD is the accumulation of uremic toxins such as p-cresol sulfate (pCS) and indoxyl sulfate (IS), which contribute to systemic damage and CKD progression. Understanding the transport mechanisms of these prominent toxins is essential for developing effective treatments. Here, we investigated whether pCS and IS are routed to the plasma membrane or to the cytosol by two key transporters, SLC22A11 and OAT1. To distinguish between cytosolic transport and plasma membrane insertion, we used a hyperosmolarity assay in which the accumulation of substrates into HEK-293 cells in isotonic and hypertonic buffers was measured in parallel using LC-MS\/MS. Judging from the efficiency of transport (TE), pCS is a relevant substrate of SLC22A11 at 7.8 \u00b1 1.4 \u00b5L min\u22121 mg protein\u22121 but not as good as estrone-3-sulfate; OAT1 translocates pCS less efficiently. The TE of SLC22A11 for IS was similar to pCS. For OAT1, however, IS is an excellent substrate. With OAT1 and p-aminohippuric acid, our study revealed an influence of transporter abundance on the outcomes of the hyperosmolarity assay; very high transport activity confounded results. SLC22A11 was found to insert both pCS and IS into the plasma membrane, whereas OAT1 conveys these toxins to the cytosol. These disparate transport mechanisms bear profound ramifications for toxicity. Membrane insertion might promote membrane damage and microvesicle release. Our results underscore the imperative for detailed structural inquiries into the translocation of small molecules.<\/jats:p>","DOI":"10.3390\/ijms242015187","type":"journal-article","created":{"date-parts":[[2023,10,14]],"date-time":"2023-10-14T14:38:42Z","timestamp":1697294322000},"page":"15187","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["SLC22A11 Inserts the Uremic Toxins Indoxyl Sulfate and P-Cresol Sulfate into the Plasma Membrane"],"prefix":"10.3390","volume":"24","author":[{"given":"Maurice","family":"Tust","sequence":"first","affiliation":[{"name":"Department of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Gleueler Stra\u00dfe 24, 50931 Cologne, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Julian Peter","family":"M\u00fcller","sequence":"additional","affiliation":[{"name":"Department of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Gleueler Stra\u00dfe 24, 50931 Cologne, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1816-3014","authenticated-orcid":false,"given":"Dietmar","family":"Fischer","sequence":"additional","affiliation":[{"name":"Department of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Gleueler Stra\u00dfe 24, 50931 Cologne, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0914-0299","authenticated-orcid":false,"given":"Dirk","family":"Gr\u00fcndemann","sequence":"additional","affiliation":[{"name":"Department of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Gleueler Stra\u00dfe 24, 50931 Cologne, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,10,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"299","DOI":"10.1159\/000502331","article-title":"Uremic Toxins and their Relation to Dialysis Efficacy","volume":"48","author":"Clark","year":"2019","journal-title":"Blood Purif."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Lim, Y.J., Sidor, N.A., Tonial, N.C., Che, A., and Urquhart, B.L. (2021). Uremic Toxins in the Progression of Chronic Kidney Disease and Cardiovascular Disease: Mechanisms and Therapeutic Targets. Toxins, 13.","DOI":"10.3390\/toxins13020142"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"825","DOI":"10.7326\/0003-4819-158-11-201306040-00007","article-title":"Kidney Disease: Improving Global Outcomes Chronic Kidney Disease Guideline Development Work Group. Evaluation and Management of Chronic Kidney Disease: Synopsis of the Kidney Disease: Improving Global Outcomes 2012 Clinical Practice Guideline","volume":"158","author":"Stevens","year":"2013","journal-title":"Ann. Intern. Med."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1294","DOI":"10.1001\/jama.2019.14745","article-title":"Chronic Kidney Disease Diagnosis and Management: A Review","volume":"322","author":"Chen","year":"2019","journal-title":"J. Am. Med. Assoc."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1841","DOI":"10.1007\/s00216-012-5929-3","article-title":"Protein-bound uremic toxins in hemodialysis patients measured by liquid chromatography\/tandem mass spectrometry and their effects on endothelial ROS production","volume":"403","author":"Itoh","year":"2012","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Liu, W.-C., Tomino, Y., and Lu, K.-C. (2018). Impacts of Indoxyl Sulfate and p-Cresol Sulfate on Chronic Kidney Disease and Mitigating Effects of AST-120. Toxins, 10.","DOI":"10.3390\/toxins10090367"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Gryp, T., Vanholder, R., Vaneechoutte, M., and Glorieux, G. (2017). p-Cresyl sulfate. Toxins, 9.","DOI":"10.3390\/toxins9020052"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1093\/toxsci\/kfj061","article-title":"Human Sulfotransferases and Their Role in Chemical Metabolism","volume":"90","author":"Gamage","year":"2005","journal-title":"Toxicol. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Leong, S.C., and Sirich, T.L. (2016). Indoxyl Sulfate\u2014Review of Toxicity and Therapeutic Strategies. Toxins, 8.","DOI":"10.3390\/toxins8120358"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1007\/BF03226377","article-title":"Hepatic microsomal metabolism of indole to indoxyl, a precursor of indoxyl sulfate","volume":"26","author":"Banoglu","year":"2001","journal-title":"Eur. J. Drug Metab. Pharmacokinet."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1007\/BF03190428","article-title":"Sulfation of indoxyl by human and rat aryl (phenol) sulfotransferases to form indoxyl sulfate","volume":"27","author":"Banoglu","year":"2002","journal-title":"Eur. J. Drug Metab. Pharmacokinet."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1711","DOI":"10.1097\/01.ASN.0000022017.96399.B2","article-title":"Role of Organic Anion Transporters in the Tubular Transport of Indoxyl Sulfate and the Induction of its Nephrotoxicity","volume":"13","author":"Enomoto","year":"2002","journal-title":"J. Am. Soc. Nephrol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1016\/S0014-2999(03)01530-9","article-title":"Interactions of human organic anion as well as cation transporters with indoxyl sulfate","volume":"466","author":"Enomoto","year":"2003","journal-title":"Eur. J. Pharmacol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2498","DOI":"10.1093\/ndt\/gfq785","article-title":"Organic anion transporters play an important role in the uptake of p-cresyl sulfate, a uremic toxin, in the kidney","volume":"26","author":"Miyamoto","year":"2011","journal-title":"Nephrol. Dial. Transplant."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1152\/physrev.00025.2013","article-title":"The Organic Anion Transporter (OAT) Family: A Systems Biology Perspective","volume":"95","author":"Nigam","year":"2015","journal-title":"Physiol. Rev."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"4507","DOI":"10.1074\/jbc.275.6.4507","article-title":"Molecular Cloning and Characterization of Multispecific Organic Anion Transporter 4 Expressed in the Placenta","volume":"275","author":"Cha","year":"2000","journal-title":"J. Biol. Chem."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"430","DOI":"10.1681\/ASN.2006040415","article-title":"Human Renal Organic Anion Transporter 4 Operates as an Asymmetric Urate Transporter","volume":"18","author":"Hagos","year":"2007","journal-title":"J. Am. Soc. Nephrol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"74","DOI":"10.1016\/j.bcp.2016.12.020","article-title":"A novel mode of operation of SLC22A11: Membrane insertion of estrone sulfate versus translocation of uric acid and glutamate","volume":"128","author":"Skwara","year":"2017","journal-title":"Biochem. Pharmacol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1038\/nature07678","article-title":"Transmembrane passage of hydrophobic compounds through a protein channel wall","volume":"458","author":"Hearn","year":"2009","journal-title":"Nature"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"eaas9365","DOI":"10.1126\/sciadv.aas9365","article-title":"Powering the ABC multidrug exporter LmrA: How nucleotides embrace the ion-motive force","volume":"4","author":"Agboh","year":"2018","journal-title":"Sci. Adv."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"M\u00fcller, J.P., Keufgens, L., and Gr\u00fcndemann, D. (2021). Hyperosmolarity stimulates transporter-mediated insertion of estrone sulfate into the plasma membrane, but inhibits the uptake by SLC10A1 (NTCP). Biochem. Pharmacol., 186.","DOI":"10.1016\/j.bcp.2021.114484"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"jcs232579","DOI":"10.1242\/jcs.232579","article-title":"Acute decrease in plasma membrane tension induces macropinocytosis via PLD2 activation","volume":"132","author":"Loh","year":"2019","journal-title":"J. Cell Sci."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1006\/excr.1999.4792","article-title":"Caveolin Internalization by Heat Shock or Hyperosmotic Shock","volume":"255","author":"Kang","year":"2000","journal-title":"Exp. Cell Res."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"975","DOI":"10.1016\/j.bbamem.2010.01.015","article-title":"Lateral reorganization of plasma membrane is involved in the yeast resistance to severe dehydration","volume":"1798","author":"Dupont","year":"2010","journal-title":"Biochim. Biophys. Acta (BBA)-Biomembr."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"L560","DOI":"10.1152\/ajplung.00309.2010","article-title":"Endocytic response of type I alveolar epithelial cells to hypertonic stress","volume":"300","author":"Wang","year":"2011","journal-title":"Am. J. Physiol. Cell. Mol. Physiol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"24237","DOI":"10.1074\/jbc.M115.666883","article-title":"Regulation of plasma membrane localization of the Na+-taurocholate cotransporting polypeptide (Ntcp) by hyperosmolarity and tauroursodeoxycholate","volume":"290","author":"Sommerfeld","year":"2015","journal-title":"J. Biol. Chem."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Le Roux, A.-L., Quiroga, X., Walani, N., Arroyo, M., and Roca-Cusachs, P. (2019). The plasma membrane as a mechanochemical transducer. Philos. Trans. R. Soc. B Biol. Sci., 374.","DOI":"10.1098\/rstb.2018.0221"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"393","DOI":"10.1021\/bi901786x","article-title":"The Uremic Toxin 3-Indoxyl Sulfate Is a Potent Endogenous Agonist for the Human Aryl Hydrocarbon Receptor","volume":"49","author":"Schroeder","year":"2009","journal-title":"Biochemistry"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Cheng, T.-H., Ma, M.-C., Liao, M.-T., Zheng, C.-M., Lu, K.-C., Liao, C.-H., Hou, Y.-C., Liu, W.-C., and Lu, C.-L. (2020). Indoxyl Sulfate, a Tubular Toxin, Contributes to the Development of Chronic Kidney Disease. Toxins, 12.","DOI":"10.3390\/toxins12110684"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1671","DOI":"10.1046\/j.1523-1755.2003.00906.x","article-title":"Uremic toxins of organic anions up-regulate PAI-1 expression by induction of NF-kappa B and free radical in proximal tubular cells","volume":"63","author":"Motojima","year":"2003","journal-title":"Kidney Int."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Edamatsu, T., Fujieda, A., and Itoh, Y. (2018). Phenyl sulfate, indoxyl sulfate and p-cresyl sulfate decrease glutathione level to render cells vulnerable to oxidative stress in renal tubular cells. PLoS ONE, 13.","DOI":"10.1371\/journal.pone.0193342"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1016\/j.etp.2014.01.003","article-title":"Uremic toxins impair human bone marrow-derived mesenchymal stem cells functionality in vitro","volume":"66","author":"Idziak","year":"2014","journal-title":"Exp. Toxicol. Pathol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"953","DOI":"10.1016\/j.csbj.2020.04.006","article-title":"Microvesicles from indoxyl sulfate-treated endothelial cells induce vascular calcification in vitro","volume":"18","author":"Alique","year":"2020","journal-title":"Comput. Struct. Biotechnol. J."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"F853","DOI":"10.1152\/ajprenal.2000.278.6.F853","article-title":"Structure of renal organic anion and cation transporters","volume":"278","author":"Burckhardt","year":"2000","journal-title":"Am. J. Physiol. Physiol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"4191","DOI":"10.1042\/BCJ20200666","article-title":"Transporter tandems: Precise tools for normalizing active transporter in the plasma membrane","volume":"477","author":"Tschirka","year":"2020","journal-title":"Biochem. J."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"F122","DOI":"10.1152\/ajprenal.1999.276.1.F122","article-title":"Molecular cloning and functional expression of a multispecific organic anion transporter from human kidney","volume":"276","author":"Hosoyamada","year":"1999","journal-title":"Am. J. Physiol. Physiol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"F295","DOI":"10.1152\/ajprenal.1999.276.2.F295","article-title":"Cloning of the human kidney PAH transporter: Narrow substrate specificity and regulation by protein kinase C","volume":"276","author":"Lu","year":"1999","journal-title":"Am. J. Physiol. Physiol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1508","DOI":"10.2215\/CJN.00300113","article-title":"Renal Clearance and Intestinal Generation of p-Cresyl Sulfate and Indoxyl Sulfate in CKD","volume":"8","author":"Poesen","year":"2013","journal-title":"Clin. J. Am. Soc. Nephrol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"6714","DOI":"10.1038\/s41467-022-34284-8","article-title":"Structural basis of organic cation transporter-3 inhibition","volume":"13","author":"Khanppnavar","year":"2022","journal-title":"Nat. Commun."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"783","DOI":"10.1111\/j.1742-4658.2006.05623.x","article-title":"Fast set-up of doxycycline-inducible protein expression in human cell lines with a single plasmid based on Epstein-Barr virus replication and the simple tetracycline repressor","volume":"274","author":"Bach","year":"2007","journal-title":"FEBS J."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1042\/BJ20101904","article-title":"OAT2 catalyses efflux of glutamate and uptake of orotic acid","volume":"436","author":"Fork","year":"2011","journal-title":"Biochem. J."}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/24\/20\/15187\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:07:02Z","timestamp":1760130422000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/24\/20\/15187"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,10,14]]},"references-count":41,"journal-issue":{"issue":"20","published-online":{"date-parts":[[2023,10]]}},"alternative-id":["ijms242015187"],"URL":"https:\/\/doi.org\/10.3390\/ijms242015187","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,10,14]]}}}