SLC Transporter Assays

Background of SLC Transporters

The solute carrier (SLC) transporters of solute carriers are the second largest superfamily following G protein-coupled receptors, which play a role in the translocation of different substances across the cellular membranes. SLCs are composed of a number of transmembrane α-helices linked by intra- and extracellular loops. Similar to ABC transporters, SLC transporters primarily determine the drug efficacy rather than therapeutic effects.

Fig.1 A widespread role for SLC transmembrane transporters in resistance to cytotoxic drugs. (Girardi, 2020)

Distributions and Functions of SLC Transporters

SLC transporters are generally present in the membranes of cells, mitochondria, or other intracellular organelles. Diverse group members of the SLC transporter family modulate the translocation of distinct substances across the membranes, such as amino acids and peptides, saccharides, neurotransmitters, metal ions, ion-coupled substances, phosphate, vitamins, metabolites, etc. They play roles in primary and secondary active transport, water channels, ion exchange, ion pump, facilitating transport, and absorption and cellular activity of drugs. Inhibitors and activators of SLC transporters for therapeutic purposes for the transportation of organic acids, neuropsychosis, diabetes, diuretics, and other metabolic and inherited diseases are under development.

Subtypes and Mechanisms of SLC Transporters

SLC transporters are a family of transporters classified into over 400 membrane proteins within more than 60 subfamilies. The diverse structures of SLC transporters determine the variety of solutes that they migrate. The transport mechanisms of SLC transporters are divided into the rocker-switch-corresponding fold transportation, the gated-pore or rocking bundle, and the elevator mechanism.

SLC Transporters	Gene	Substrates	Inhibitors
MATE1 (SLC47A1)	SLC47A1	Endogenous substrates: creatine and thiamine Substrates: quinidine, paraquat, cephradine, cephalexin, cimetidine, and metformin	pyrimethamine cimetidine
OCT1 (SLC22A1)	SLC22A1	Endogenous substrates: 5-hydroxytryptamine, PGE2, PGF2α, and choline Substrates: tetraethylammonium, desipramine, MPP+, metformin, and aciclovir	clonidine
OCT2 (SLC22A2)	SLC22A2	Endogenous substrates: dopamine, histamine and PGE2. Substrates: tubocurarine, tetraethylammonium, pancuronium, MPP+, metformin, and cisplatin	decynium 22
OATP1B1 (SLCO1B1)	SLCO1B1	Endogenous substrates: bilirubin, bile acids, leukotrienes, steroid conjugates, and thyroid hormones Substrates: rifampicin, bromsulphthalein, fexofenadine, ACE inhibitors, anticancer drugs, antifungals β-lactam antibiotics, bile acid derivatives, and conjugates, endothelin receptor antagonists, HIV protease inhibitors, opioids, sartans, and statins	cyclosporin A rifampicin rifamycin SV gemfibrozil glycyrrhizin indocyanine green fibrates flavonoids glitazones
OATP1B3 (SLCO1B3)	SLCO1B3	Endogenous substrates: CCK-8, LTC4, bilirubin, bile acids, steroid conjugates, and thyroid hormones Substrates: erythromycin, rifampicin, bromsulphthalein, amanitin, digoxin, phalloidin, saquinavir, fexofenadine, ouabain, anticancer drugs, β-lactam antibiotics, bile acid derivatives, and conjugates, opioids, sartans, and statins	cyclosporin A sildenafil rifampicin gemfibrozil rifamycin SV glycyrrhizin HIV protease inhibitors glitazones
OAT1 (SLC22A6)	SLC22A6	Substrates: uric acid, aminohippuric acid, tenofovir, and non-steroidal anti-inflammatory drugs
OAT3 (SLC22A8)	SLC22A8	Substrates: cimetidine, ochratoxin A, uric acid, estrone-3-sulphate, and aminohippuric acid
NTCP (SLC10A1)	SLC10A1	Endogenous substrates: tauroursodeoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, glycocholic acid, cholic acid, dehydroepiandrosterone sulphate, estrone-3-sulphate, and iodothyronine sulphates	cyclosporin A irbesartan (-)-propranolol cyclosporin A (+)-propranolol

Assay List of SLC Transporters

Creative Biolabs can provide a range of assays of SLC Transporters. You can choose the assay in the list or contact us for more information:

SLC Transporters

Assay No.	Assay Name	Host Cell	Assay Type
S01YF-1122-KX206	Magic™ Human SLC6A3 In Vitro Radioligand Binding Assay	CHO-K1	Radioligand Binding Assay
S01YF-1122-KX207	Magic™ Human SLC6A2 In Vitro Radioligand Binding Assay	MDCK	Radioligand Binding Assay
S01YF-1122-KX208	Magic™ Human SLC6A4 In Vitro Radioligand Binding Assay	HEK293	Radioligand Binding Assay

Published Data

Paper Title	Detection of chemical engagement of solute carrier proteins by a cellular thermal shift assay
Journal	ACS chemical biology
Published	2018
Abstract	SLC transporters are the second-largest fraction of the membrane proteome following G-protein-coupled receptors, transporting a variety of nutrients, metabolites, and drugs across cellular membranes. The knowledge about endobiotic or xenobiotic ligands of SLC transporters remains understudied. There are roughly 20 SLC inhibitors that have been characterized. The assays in cells are limited to the accessibility of radiolabeled or fluorescent probes. The cellular thermal shift assay (CETSA) may exert as a powerful method to assess target engagement by monitoring ligand-induced changes in the thermal stability of cellular proteins. The study aimed to test the feasibility of the CETSA approach for the detection of SLC-binding events. They chose SLC1A2 and SLC16A1 receptors for the study, which are also currently studied as drug targets for neurodegenerative diseases and cancer.
Result	They used SLC16A1 (MCT1) and SLC1A2 (EAAT2) as targets to establish robust conditions. The cellular thermal shift assay was applied so that the chemical engagement of SLCs could be detected. They used immunoblotting to demonstrate that treatment with the SLC16A1 inhibitors AZD3965 and AR-C155858 stabilized endogenous SLC16A1 in HEK293 cell lysates as well as intact cells. Besides, the high-affinity ligand of SLC16A1, l-lactate resulted in strong stabilization of SLC16A1, while the low-affinity ligand showed weak stabilization of SLC16A1. Furthermore, the results have demonstrated stabilization of SLC1A2 upon treatment with the selective inhibitor WAY-213613. The study suggested that the experimental approach can be a general and easy approach applied for monitoring the engagement of chemical ligands by SLCs in cellular settings and thus assisting in their deorphanization. Fig.2 CETSA for SLC16A1 inhibitors in HEK293 cell lysates and intact cells. (Hashimoto, 2018)

References

Girardi, E.; et al. A widespread role for SLC transmembrane transporters in resistance to cytotoxic drugs. Nature chemical biology. 2020,16(4): 469-478.
Hashimoto, M.; et al. Detection of chemical engagement of solute carrier proteins by a cellular thermal shift assay. ACS chemical biology. 2018, 13(6): 1480-1486.

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