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Theo J. Visser - One of the best experts on this subject based on the ideXlab platform.
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effects of chemical chaperones on thyroid Hormone Transport by mct8 mutants in patient derived fibroblasts
Endocrinology, 2018Co-Authors: Stefan Groeneweg, Theo J. Visser, Amanda Van Den Berge, Marcel E Meima, Robin P Peeters, Edward W VisserAbstract:Mutations in the thyroid Hormone (TH) Transporter monocarboxylate Transporter 8 (MCT8) result in severe intellectual and motor disability. At present, no effective therapy is available to restore TH signaling in MCT8-dependent tissues. Recent in vitro studies in stable overexpression cell models suggested that the function of certain mutant MCT8 proteins, specifically those that affect protein stability and intracellular trafficking (e.g., p.F501del), could be partially recovered by chemical chaperones. However, the effects of chaperones have not been demonstrated in other commonly used models for MCT8 deficiency, including transient overexpression models and patient-derived fibroblasts. Here, we demonstrate that the chemical chaperone 4-phenylbutyric acid (PBA) similarly potentiates the T3 Transport function of wild-type and p.F501del mutant MCT8 in transiently transfected COS-1 cells by increasing MCT8 messenger RNA, total protein, and cell surface expression levels. Although PBA also increased the cell surface expression levels of the p.R445L mutant, no functional improvement was observed, which is in line with the proposed important role of Arg445 in substrate translocation. In contrast, PBA showed only minimal effects in ex vivo studies using control or p.F501del patient-derived fibroblasts. Moreover, the MCT8-specific inhibitor silychristin did not change these minimal effects, suggesting that the underlying mechanism is unrelated to the rescue of functional MCT8. Together, these findings indicate that the potency of chaperones to rescue mutant MCT8 function strongly depends on the cellular model and stress the need for further preclinical studies before clinically available chaperones should be considered as a treatment option in patients with MCT8 deficiency.
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disorder of thyroid Hormone Transport into the tissues
Best Practice & Research Clinical Endocrinology & Metabolism, 2017Co-Authors: Stefan Groeneweg, Edward W Visser, Theo J. VisserAbstract:Transport of thyroid Hormone (TH) across the plasma membrane is essential for intracellular TH metabolism and action, and this is mediated by specific Transporter proteins. During the last two decades several Transporters capable of Transporting TH have been identified, including monocarboxylate Transporter 8 (MCT8), MCT10 and organic anion Transporting polypeptide 1C1 (OATP1C1). In particular MCT8 and OATP1C1 are important for the regulation of local TH activity in the brain and thus for brain development. MCT8 is a protein containing 12 transmembrane domains, and is encoded by the SLC16A2 gene located on the X chromosome. It facilitates both TH uptake and efflux across the cell membrane. Male subjects with hemizygous mutations in MCT8 are afflicted with severe intellectual and motor disability, also known as the Allan-Herndon-Dudley syndrome (AHDS), which goes together with low serum T4 and high T3 levels. This review concerns molecular and clinical aspects of MCT8 function.
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genetics and phenomics of thyroid Hormone Transport by mct8
Molecular and Cellular Endocrinology, 2010Co-Authors: Edith C. H. Friesema, Edward W Visser, Theo J. VisserAbstract:Thyroid Hormone (TH) is crucial for the development of different organs, in particular the brain, as disturbances in TH supply cause severe neurological abnormalities. TH Transporters are necessary for the intracellular availability of TH to have access to the deiodinases and nuclear receptors inside the cell. The clinical importance of TH Transporters is dramatically shown in patients with mutations in MCT8, suffering from severe X-linked psychomotor retardation in combination with disturbed TH levels, especially high serum T(3) levels, now referred as Allan-Herndon-Dudley Syndrome (AHDS). Worldwide >45 families have now been identified with MCT8 mutations. Most MCT8 mutations result in a complete loss of TH Transport function when tested in vitro, but some mutations show significant residual activity and are associated with a somewhat milder clinical phenotype. It is difficult to identify MCT8 patients only on the basis of the clinical characteristics of X-linked mental retardation. Therefore, the criterion for MCT8 mutation screening in these patients is the profile of increased T(3) and low-normal to low FT(4) serum levels.
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Transport of thyroid Hormones is selectively inhibited by 3-iodothyronamine
Molecular BioSystems, 2010Co-Authors: Alexandra G Ianculescu, Edith C. H. Friesema, Theo J. Visser, Kathleen M. Giacomini, Thomas S ScanlanAbstract:Thyroid Hormone Transporters are responsible for the cellular uptake of thyroid Hormones, which is a prerequisite for their subsequent metabolism and action at nuclear thyroid Hormone receptors. A recently discovered thyroid Hormone derivative, 3-iodothyronamine (T1AM), has distinct biological effects that are opposite those of thyroid Hormone. Here we investigate the effects of T1AM on thyroid Hormone Transporters using COS-1 cells transfected with the multispecific organic anion Transporting polypeptides (OATPs) 1A2, 1B3, and 1C1, as well as the specific thyroid Hormone Transporters MCT8 and MCT10, and show that T1AM displays differential inhibition of T3 and T4 cellular uptake by these Transporters. T1AM inhibits T3 and T4 Transport by OATP1A2 with IC50 values of 0.27 and 2.1 μM, respectively. T4 Transport by OATP1C1, which is thought to play a key role in thyroid Hormone Transport across the blood-brain barrier, is inhibited by T1AM with an IC50 of 4.8 μM. T1AM also inhibits both T3 and T4 uptake via MCT8, the most specific thyroid Hormone Transporter identified to date, with IC50 values of 95 and 31 μM, respectively. By contrast, T1AM has no effect on thyroid Hormone Transport by OATP1B3 and MCT10. Given that OATP1A2, OATP1C1, and MCT8 are all present in the brain, T1AM may play an important role in modulating thyroid Hormone delivery and activity in specific target regions in the central nervous system.
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consequences of monocarboxylate Transporter 8 deficiency for renal Transport and metabolism of thyroid Hormones in mice
Endocrinology, 2010Co-Authors: Marija Trajkovicarsic, Edith C. H. Friesema, Theo J. Visser, Karl Bauer, Veerle Darras, Bernhard Schlott, Jens Mittag, Heike HeuerAbstract:Patients carrying inactivating mutations in the gene encoding the thyroid Hormone Transporting monocarboxylate Transporter (MCT)-8 suffer from a severe form of psychomotor retardation and exhibit abnormal serum thyroid Hormone levels. The thyroidal phenotype characterized by high-serum T3 and low-serum T4 levels is also found in mice mutants deficient in MCT8 although the cause of these abnormalities is still unknown. Here we describe the consequences of MCT8 deficiency for renal thyroid Hormone Transport, metabolism, and function by studying MCT8 null mice and wild-type littermates. Whereas serum and urinary parameters do not indicate a strongly altered renal function, a pronounced induction of iodothyronine deiodinase type 1 expression together with increased renal T3 and T4 content point to a general hyperthyroid state of the kidneys in the absence of MCT8. Surprisingly, accumulation of peripherally injected T4 and T3 into the kidneys was found to be enhanced in the absence of MCT8, indicating that MCT...
Gerd Krause - One of the best experts on this subject based on the ideXlab platform.
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Molecular Mechanisms of Thyroid Hormone Transport by l-Type Amino Acid Transporter.
Experimental and clinical endocrinology & diabetes : official journal German Society of Endocrinology [and] German Diabetes Association, 2019Co-Authors: Gerd Krause, Katrin M. HinzAbstract:Thyroid Hormones (TH) pass through the plasma membrane into the target cells via Transporter proteins. Thyroid Hormone Transporters that have been identified until now belong to two different solute carrier (SLC) subfamilies i) the major facilitator superfamily (MFS) and ii) the amino acid polyamine-organocation (APC) superfamily. Both are comprised by 12 transmembrane helices, however with different structural topology. The TH Transporter MCT8, MCT10 and OATP1C1 are members of the MSF. The l-type amino acid Transporters (LATs) are Transporting neutral amino acids across the membrane. Two LAT subtypes, LAT1 and LAT2 are members of the APC superfamily, need the escort protein 4F2hc and facilitate uptake but no efflux of TH-subtypes. Homology models of LAT2 that are based on crystal structures of APC Transporters guided mutagenesis, revealed molecular structure-function determinants for recognition and transition for import and export of TH-subtypes. The recently solved cryo-EM structure of LAT1 confirmed the structural input. Two other LAT subtypes, LAT3 and LAT4 are members of the MFS. From previous observed negative effect of LAT3 and LAT4 on 3,3’-T2 uptake by LAT1 and LAT2 it was indirectly concluded that LAT3 might export 3,3’-T2. There are still open questions that need to be addressed in order to fully understand the molecular recognition pattern and traversing mechanism of import and export of particular TH-subtypes by LAT1 and LAT2. Moreover, clarification is needed whether LAT3 and LAT4 are exporting TH. Recent new data could not verify the initial hypothesis of TH export by LAT3. Therefore, further investigations are necessary to explain the negative effect of LAT3 on the TH import by LAT2.
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Thyroid Hormone Transport across L-type amino acid Transporters: What can molecular modelling tell us?
Molecular and cellular endocrinology, 2017Co-Authors: Gerd Krause, Katrin M. HinzAbstract:Abstract Thyroid Hormones (THs) and their derivatives require transmembrane Transporters (TTs) to mediate their translocation across the cell membrane. Among these TTs, the L-type amino acid Transporters (LAT) not only Transport amino acids (AAs) but also certain THs and their derivatives. This review summarizes available knowledge concerning structure function patterns of the TH Transport by LAT1 and LAT2. For example, LAT2 imports 3,3′-T 2 and T 3 , but not rT 3 and T 4 . In contrast to amino acids, THs are not at all exported by LAT2. Homology modelling of LAT1 and LAT2 is based on available crystal structures from the same superfamily the amino acid/polyamine/organocation Transporter (APC). Molecular model guided mutagenesis has been used to predict substrate interaction sites. A common recognition feature for amino acid- and TH-derivatives has been suggested in an interior cavity of LAT1 and LAT2. Therein additional distinct molecular determinants that are responsible for the bidirectional AA Transport but allowing only unidirectional import of particular THs have been confirmed for LAT2 by mutagenesis. Characterized substrate features that are needed for TH translocation and distinct LAT2 properties will be highlighted to understand the molecular import and export mechanisms of this Transporter in more detail.
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membrane traversing mechanism of thyroid Hormone Transport by monocarboxylate Transporter 8
Cellular and Molecular Life Sciences, 2017Co-Authors: Jonas Protze, Katrin M. Hinz, Doreen Braun, Ulrich Schweizer, Dorothea Bayerkusch, Gerd KrauseAbstract:Monocarboxylate Transporter 8 (MCT8) mediates thyroid Hormone (TH) Transport across the plasma membrane in many cell types. In order to better understand its mechanism, we have generated three new MCT8 homology models based on sugar Transporters XylE in the intracellular opened (PDB ID: 4aj4) and the extracellular partly occluded (PDB ID: 4gby) conformations as well as FucP (PDB ID: 3o7q) and GLUT3 (PDB ID: 4zwc) in the fully extracellular opened conformation. T3-docking studies from both sides revealed interactions with His192, His415, Arg445 and Asp498 as previously identified. Selected mutations revealed further Transport-sensitive positions mainly at the discontinuous transmembrane helices TMH7 and 10. Lys418 is potentially involved in neutralising the charge of the TH substrate because it can be replaced by charged, but not by uncharged, amino acids. The side chain of Thr503 was hypothesised to stabilise a helix break at TMH10 that undergoes a prominent local shift during the Transport cycle. A T503V mutation accordingly affected Transport. The aromatic Tyr419, the polar Ser313 and Ser314 as well as the charged Glu422 and Glu423 lining the Transport channel have been studied. Based on related sugar Transporters, we suggest an alternating access mechanism for MCT8 involving a series of amino acid positions previously and newly identified as critical for Transport.
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Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3′-Diiodothyronine across the Plasma Membrane
European Thyroid Journal, 2015Co-Authors: Anita Kinne, Josef Köhrle, Katrin M. Hinz, Eva K. Wirth, Melanie Wittner, Ralf Schülein, Gerd KrauseAbstract:Thyroid Hormones are Transported across cell membranes by transmembrane Transporter proteins, for example by members of the monocarboxylate Transporter (MCT) and the L-type amino acid Transporter (LAT) families. LATs consist of a light chain (e.g. LAT2) and a heavy chain (CD98), which is essential for their cell surface expression and functionality. The specificity of Lat2 for thyroid Hormones and their metabolites and its role in their Transport was not fully clear. This fact motivated us to establish a cell system to elucidate the uptake of thyroid Hormones and their metabolites by mouse Lat2. The coinjection of cRNA coding for Lat2 and CD98 into Xenopus laevis oocytes resulted in a markedly increased level of 3,3′-diiodo-L-thyronine (3,3′-T2) and to some extent also enhanced T3 Transport. To gain insight into properties of thyroid Hormones and their metabolites Transported by Lat2, we inhibited 3,3′-T2 uptake by various iodothyronine derivatives. T1 and T2 derivatives as well as 2-aminobicyclo-[2,2,1]-heptane-2-carboxylic acid strongly competed with 3,3′-T2 uptake. In addition, we performed T2 uptake measurements with the thyroid Hormone-specific Transporter MCT8. For both Lat2 and MCT8, Km values in a low micromolar range were calculated. We demonstrated that oocytes are a suitable system for thyroid Hormone Transport studies mediated by Lat2. Our data indicates that Lat2 compared to other thyroid Hormone Transporters prefers 3,3′-T2 as the substrate. Thus, Lat2 might contribute to the availability of thyroid Hormone by importing and/or exporting 3,3′-T2, which is generated either by T3 inactivation or by rapid deiodinase 1-mediated rT3 degradation.
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Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3 ' -Diiodothyronine across the Plasma Membrane
European thyroid journal, 2015Co-Authors: Anita Kinne, Josef Köhrle, Katrin M. Hinz, Eva K. Wirth, Melanie Wittner, Ralf Schülein, Gerd KrauseAbstract:Thyroid Hormones are Transported across cell membranes by transmembrane Transporter proteins, for example by members of the monocarboxylate Transporter (MCT) and the L-type amino acid Transporter (LAT) families. LATs consist of a light chain (e.g. LAT2) and a heavy chain (CD98), which is essential for their cell surface expression and functionality. The specificity of Lat2 for thyroid Hormones and their metabolites and its role in their Transport was not fully clear. This fact motivated us to establish a cell system to elucidate the uptake of thyroid Hormones and their metabolites by mouse Lat2. The coinjection of cRNA coding for Lat2 and CD98 into Xenopus laevis oocytes resulted in a markedly increased level of 3,3'-diiodo-L-thyronine (3,3'-T2) and to some extent also enhanced T3 Transport. To gain insight into properties of thyroid Hormones and their metabolites Transported by Lat2, we inhibited 3,3'-T2 uptake by various iodothyronine derivatives. T1 and T2 derivatives as well as 2-aminobicyclo-[2, 2,1]-heptane-2-carboxylic acid strongly competed with 3,3'-T2 uptake. In addition, we performed T2 uptake measurements with the thyroid Hormone-specific Transporter MCT8. For both Lat2 and MCT8, Km values in a low micromolar range were calculated. We demonstrated that oocytes are a suitable system for thyroid Hormone Transport studies mediated by Lat2. Our data indicates that Lat2 compared to other thyroid Hormone Transporters prefers 3,3'-T2 as the substrate. Thus, Lat2 might contribute to the availability of thyroid Hormone by importing and/or exporting 3,3'-T2, which is generated either by T3 inactivation or by rapid deiodinase 1-mediated rT3 degradation.
Edith C. H. Friesema - One of the best experts on this subject based on the ideXlab platform.
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genetics and phenomics of thyroid Hormone Transport by mct8
Molecular and Cellular Endocrinology, 2010Co-Authors: Edith C. H. Friesema, Edward W Visser, Theo J. VisserAbstract:Thyroid Hormone (TH) is crucial for the development of different organs, in particular the brain, as disturbances in TH supply cause severe neurological abnormalities. TH Transporters are necessary for the intracellular availability of TH to have access to the deiodinases and nuclear receptors inside the cell. The clinical importance of TH Transporters is dramatically shown in patients with mutations in MCT8, suffering from severe X-linked psychomotor retardation in combination with disturbed TH levels, especially high serum T(3) levels, now referred as Allan-Herndon-Dudley Syndrome (AHDS). Worldwide >45 families have now been identified with MCT8 mutations. Most MCT8 mutations result in a complete loss of TH Transport function when tested in vitro, but some mutations show significant residual activity and are associated with a somewhat milder clinical phenotype. It is difficult to identify MCT8 patients only on the basis of the clinical characteristics of X-linked mental retardation. Therefore, the criterion for MCT8 mutation screening in these patients is the profile of increased T(3) and low-normal to low FT(4) serum levels.
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Transport of thyroid Hormones is selectively inhibited by 3-iodothyronamine
Molecular BioSystems, 2010Co-Authors: Alexandra G Ianculescu, Edith C. H. Friesema, Theo J. Visser, Kathleen M. Giacomini, Thomas S ScanlanAbstract:Thyroid Hormone Transporters are responsible for the cellular uptake of thyroid Hormones, which is a prerequisite for their subsequent metabolism and action at nuclear thyroid Hormone receptors. A recently discovered thyroid Hormone derivative, 3-iodothyronamine (T1AM), has distinct biological effects that are opposite those of thyroid Hormone. Here we investigate the effects of T1AM on thyroid Hormone Transporters using COS-1 cells transfected with the multispecific organic anion Transporting polypeptides (OATPs) 1A2, 1B3, and 1C1, as well as the specific thyroid Hormone Transporters MCT8 and MCT10, and show that T1AM displays differential inhibition of T3 and T4 cellular uptake by these Transporters. T1AM inhibits T3 and T4 Transport by OATP1A2 with IC50 values of 0.27 and 2.1 μM, respectively. T4 Transport by OATP1C1, which is thought to play a key role in thyroid Hormone Transport across the blood-brain barrier, is inhibited by T1AM with an IC50 of 4.8 μM. T1AM also inhibits both T3 and T4 uptake via MCT8, the most specific thyroid Hormone Transporter identified to date, with IC50 values of 95 and 31 μM, respectively. By contrast, T1AM has no effect on thyroid Hormone Transport by OATP1B3 and MCT10. Given that OATP1A2, OATP1C1, and MCT8 are all present in the brain, T1AM may play an important role in modulating thyroid Hormone delivery and activity in specific target regions in the central nervous system.
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consequences of monocarboxylate Transporter 8 deficiency for renal Transport and metabolism of thyroid Hormones in mice
Endocrinology, 2010Co-Authors: Marija Trajkovicarsic, Edith C. H. Friesema, Theo J. Visser, Karl Bauer, Veerle Darras, Bernhard Schlott, Jens Mittag, Heike HeuerAbstract:Patients carrying inactivating mutations in the gene encoding the thyroid Hormone Transporting monocarboxylate Transporter (MCT)-8 suffer from a severe form of psychomotor retardation and exhibit abnormal serum thyroid Hormone levels. The thyroidal phenotype characterized by high-serum T3 and low-serum T4 levels is also found in mice mutants deficient in MCT8 although the cause of these abnormalities is still unknown. Here we describe the consequences of MCT8 deficiency for renal thyroid Hormone Transport, metabolism, and function by studying MCT8 null mice and wild-type littermates. Whereas serum and urinary parameters do not indicate a strongly altered renal function, a pronounced induction of iodothyronine deiodinase type 1 expression together with increased renal T3 and T4 content point to a general hyperthyroid state of the kidneys in the absence of MCT8. Surprisingly, accumulation of peripherally injected T4 and T3 into the kidneys was found to be enhanced in the absence of MCT8, indicating that MCT...
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thyroid Hormone Transport and metabolism by organic anion Transporter 1c1 and consequences of genetic variation
Endocrinology, 2008Co-Authors: Wendy M Van Der Deure, Edith C. H. Friesema, Robin P Peeters, Pia Skov Hansen, Kirsten Ohm Kyvik, Laszlo Hegedus, Theo J. VisserAbstract:Organic anion Transporting polypeptide (OATP) 1C1 has been characterized as a specific thyroid Hormone Transporter. Based on its expression in capillaries in different brain regions, OATP1C1 is thought to play a key role in Transporting thyroid Hormone across the blood-brain barrier. For this reason, we studied the specificity of iodothyronine Transport by OATP1C1 in detail by analysis of thyroid Hormone uptake in OATP1C1-transfected COS1 cells. Furthermore, we examined whether OATP1C1 is rate limiting in subsequent thyroid Hormone metabolism in cells cotransfected with deiodinases. We also studied the effect of genetic variation in the OATP1C1 gene: polymorphisms were determined in 155 blood donors and 1192 Danish twins and related to serum thyroid Hormone levels. In vitro effects of the polymorphisms were analyzed in cells transfected with the variants. Cells transfected with OATP1C1 showed increased Transport of T4 and T4 sulfate (T4S), little Transport of rT3, and no Transport of T3 or T3 sulphate, compared with mock transfected cells. Metabolism of T4, T4S, and rT3 by cotransfected deiodinases was greatly augmented in the presence of OATP1C1. The OATP1C1intron3C>T, Pro143Thr, and C3035T polymorphisms were not consistently associated with thyroid Hormone levels, nor did they affect Transport function in vitro. In conclusion, OATP1C1 mediates Transport of T4, T4S, and rT3 and increases the access of these substrates to the intracellular active sites of the deiodinases. No effect of genetic variation on the function of OATP1C1 was observed. (Endocrinology 149: 5307–5314, 2008)
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thyroid Hormone Transport in and out of cells
Trends in Endocrinology and Metabolism, 2008Co-Authors: Edward W Visser, Edith C. H. Friesema, Jurgen Jansen, Theo J. VisserAbstract:Thyroid Hormone (TH) is essential for the proper development of numerous tissues, notably the brain. TH acts mostly intracellularly, which requires Transport by TH Transporters across the plasma membrane. Although several Transporter families have been identified, only monocarboxylate Transporter (MCT)8, MCT10 and organic anion-Transporting polypeptide (OATP)1C1 demonstrate a high degree of specificity towards TH. Recently, the biological importance of MCT8 has been elucidated. Mutations in MCT8 are associated with elevated serum T3 levels and severe psychomotor retardation, indicating a pivotal role for MCT8 in brain development. MCT8 knockout mice lack neurological damage, but mimic TH abnormalities of MCT8 patients. The exact pathophysiological mechanisms in MCT8 patients remain to be elucidated fully. Future research will probably identify novel TH Transporters and disorders based on TH Transporter defects.
Katrin M. Hinz - One of the best experts on this subject based on the ideXlab platform.
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Molecular Mechanisms of Thyroid Hormone Transport by l-Type Amino Acid Transporter.
Experimental and clinical endocrinology & diabetes : official journal German Society of Endocrinology [and] German Diabetes Association, 2019Co-Authors: Gerd Krause, Katrin M. HinzAbstract:Thyroid Hormones (TH) pass through the plasma membrane into the target cells via Transporter proteins. Thyroid Hormone Transporters that have been identified until now belong to two different solute carrier (SLC) subfamilies i) the major facilitator superfamily (MFS) and ii) the amino acid polyamine-organocation (APC) superfamily. Both are comprised by 12 transmembrane helices, however with different structural topology. The TH Transporter MCT8, MCT10 and OATP1C1 are members of the MSF. The l-type amino acid Transporters (LATs) are Transporting neutral amino acids across the membrane. Two LAT subtypes, LAT1 and LAT2 are members of the APC superfamily, need the escort protein 4F2hc and facilitate uptake but no efflux of TH-subtypes. Homology models of LAT2 that are based on crystal structures of APC Transporters guided mutagenesis, revealed molecular structure-function determinants for recognition and transition for import and export of TH-subtypes. The recently solved cryo-EM structure of LAT1 confirmed the structural input. Two other LAT subtypes, LAT3 and LAT4 are members of the MFS. From previous observed negative effect of LAT3 and LAT4 on 3,3’-T2 uptake by LAT1 and LAT2 it was indirectly concluded that LAT3 might export 3,3’-T2. There are still open questions that need to be addressed in order to fully understand the molecular recognition pattern and traversing mechanism of import and export of particular TH-subtypes by LAT1 and LAT2. Moreover, clarification is needed whether LAT3 and LAT4 are exporting TH. Recent new data could not verify the initial hypothesis of TH export by LAT3. Therefore, further investigations are necessary to explain the negative effect of LAT3 on the TH import by LAT2.
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Thyroid Hormone Transport across L-type amino acid Transporters: What can molecular modelling tell us?
Molecular and cellular endocrinology, 2017Co-Authors: Gerd Krause, Katrin M. HinzAbstract:Abstract Thyroid Hormones (THs) and their derivatives require transmembrane Transporters (TTs) to mediate their translocation across the cell membrane. Among these TTs, the L-type amino acid Transporters (LAT) not only Transport amino acids (AAs) but also certain THs and their derivatives. This review summarizes available knowledge concerning structure function patterns of the TH Transport by LAT1 and LAT2. For example, LAT2 imports 3,3′-T 2 and T 3 , but not rT 3 and T 4 . In contrast to amino acids, THs are not at all exported by LAT2. Homology modelling of LAT1 and LAT2 is based on available crystal structures from the same superfamily the amino acid/polyamine/organocation Transporter (APC). Molecular model guided mutagenesis has been used to predict substrate interaction sites. A common recognition feature for amino acid- and TH-derivatives has been suggested in an interior cavity of LAT1 and LAT2. Therein additional distinct molecular determinants that are responsible for the bidirectional AA Transport but allowing only unidirectional import of particular THs have been confirmed for LAT2 by mutagenesis. Characterized substrate features that are needed for TH translocation and distinct LAT2 properties will be highlighted to understand the molecular import and export mechanisms of this Transporter in more detail.
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membrane traversing mechanism of thyroid Hormone Transport by monocarboxylate Transporter 8
Cellular and Molecular Life Sciences, 2017Co-Authors: Jonas Protze, Katrin M. Hinz, Doreen Braun, Ulrich Schweizer, Dorothea Bayerkusch, Gerd KrauseAbstract:Monocarboxylate Transporter 8 (MCT8) mediates thyroid Hormone (TH) Transport across the plasma membrane in many cell types. In order to better understand its mechanism, we have generated three new MCT8 homology models based on sugar Transporters XylE in the intracellular opened (PDB ID: 4aj4) and the extracellular partly occluded (PDB ID: 4gby) conformations as well as FucP (PDB ID: 3o7q) and GLUT3 (PDB ID: 4zwc) in the fully extracellular opened conformation. T3-docking studies from both sides revealed interactions with His192, His415, Arg445 and Asp498 as previously identified. Selected mutations revealed further Transport-sensitive positions mainly at the discontinuous transmembrane helices TMH7 and 10. Lys418 is potentially involved in neutralising the charge of the TH substrate because it can be replaced by charged, but not by uncharged, amino acids. The side chain of Thr503 was hypothesised to stabilise a helix break at TMH10 that undergoes a prominent local shift during the Transport cycle. A T503V mutation accordingly affected Transport. The aromatic Tyr419, the polar Ser313 and Ser314 as well as the charged Glu422 and Glu423 lining the Transport channel have been studied. Based on related sugar Transporters, we suggest an alternating access mechanism for MCT8 involving a series of amino acid positions previously and newly identified as critical for Transport.
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Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3′-Diiodothyronine across the Plasma Membrane
European Thyroid Journal, 2015Co-Authors: Anita Kinne, Josef Köhrle, Katrin M. Hinz, Eva K. Wirth, Melanie Wittner, Ralf Schülein, Gerd KrauseAbstract:Thyroid Hormones are Transported across cell membranes by transmembrane Transporter proteins, for example by members of the monocarboxylate Transporter (MCT) and the L-type amino acid Transporter (LAT) families. LATs consist of a light chain (e.g. LAT2) and a heavy chain (CD98), which is essential for their cell surface expression and functionality. The specificity of Lat2 for thyroid Hormones and their metabolites and its role in their Transport was not fully clear. This fact motivated us to establish a cell system to elucidate the uptake of thyroid Hormones and their metabolites by mouse Lat2. The coinjection of cRNA coding for Lat2 and CD98 into Xenopus laevis oocytes resulted in a markedly increased level of 3,3′-diiodo-L-thyronine (3,3′-T2) and to some extent also enhanced T3 Transport. To gain insight into properties of thyroid Hormones and their metabolites Transported by Lat2, we inhibited 3,3′-T2 uptake by various iodothyronine derivatives. T1 and T2 derivatives as well as 2-aminobicyclo-[2,2,1]-heptane-2-carboxylic acid strongly competed with 3,3′-T2 uptake. In addition, we performed T2 uptake measurements with the thyroid Hormone-specific Transporter MCT8. For both Lat2 and MCT8, Km values in a low micromolar range were calculated. We demonstrated that oocytes are a suitable system for thyroid Hormone Transport studies mediated by Lat2. Our data indicates that Lat2 compared to other thyroid Hormone Transporters prefers 3,3′-T2 as the substrate. Thus, Lat2 might contribute to the availability of thyroid Hormone by importing and/or exporting 3,3′-T2, which is generated either by T3 inactivation or by rapid deiodinase 1-mediated rT3 degradation.
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Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3 ' -Diiodothyronine across the Plasma Membrane
European thyroid journal, 2015Co-Authors: Anita Kinne, Josef Köhrle, Katrin M. Hinz, Eva K. Wirth, Melanie Wittner, Ralf Schülein, Gerd KrauseAbstract:Thyroid Hormones are Transported across cell membranes by transmembrane Transporter proteins, for example by members of the monocarboxylate Transporter (MCT) and the L-type amino acid Transporter (LAT) families. LATs consist of a light chain (e.g. LAT2) and a heavy chain (CD98), which is essential for their cell surface expression and functionality. The specificity of Lat2 for thyroid Hormones and their metabolites and its role in their Transport was not fully clear. This fact motivated us to establish a cell system to elucidate the uptake of thyroid Hormones and their metabolites by mouse Lat2. The coinjection of cRNA coding for Lat2 and CD98 into Xenopus laevis oocytes resulted in a markedly increased level of 3,3'-diiodo-L-thyronine (3,3'-T2) and to some extent also enhanced T3 Transport. To gain insight into properties of thyroid Hormones and their metabolites Transported by Lat2, we inhibited 3,3'-T2 uptake by various iodothyronine derivatives. T1 and T2 derivatives as well as 2-aminobicyclo-[2, 2,1]-heptane-2-carboxylic acid strongly competed with 3,3'-T2 uptake. In addition, we performed T2 uptake measurements with the thyroid Hormone-specific Transporter MCT8. For both Lat2 and MCT8, Km values in a low micromolar range were calculated. We demonstrated that oocytes are a suitable system for thyroid Hormone Transport studies mediated by Lat2. Our data indicates that Lat2 compared to other thyroid Hormone Transporters prefers 3,3'-T2 as the substrate. Thus, Lat2 might contribute to the availability of thyroid Hormone by importing and/or exporting 3,3'-T2, which is generated either by T3 inactivation or by rapid deiodinase 1-mediated rT3 degradation.
Anita Kinne - One of the best experts on this subject based on the ideXlab platform.
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Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3′-Diiodothyronine across the Plasma Membrane
European Thyroid Journal, 2015Co-Authors: Anita Kinne, Josef Köhrle, Katrin M. Hinz, Eva K. Wirth, Melanie Wittner, Ralf Schülein, Gerd KrauseAbstract:Thyroid Hormones are Transported across cell membranes by transmembrane Transporter proteins, for example by members of the monocarboxylate Transporter (MCT) and the L-type amino acid Transporter (LAT) families. LATs consist of a light chain (e.g. LAT2) and a heavy chain (CD98), which is essential for their cell surface expression and functionality. The specificity of Lat2 for thyroid Hormones and their metabolites and its role in their Transport was not fully clear. This fact motivated us to establish a cell system to elucidate the uptake of thyroid Hormones and their metabolites by mouse Lat2. The coinjection of cRNA coding for Lat2 and CD98 into Xenopus laevis oocytes resulted in a markedly increased level of 3,3′-diiodo-L-thyronine (3,3′-T2) and to some extent also enhanced T3 Transport. To gain insight into properties of thyroid Hormones and their metabolites Transported by Lat2, we inhibited 3,3′-T2 uptake by various iodothyronine derivatives. T1 and T2 derivatives as well as 2-aminobicyclo-[2,2,1]-heptane-2-carboxylic acid strongly competed with 3,3′-T2 uptake. In addition, we performed T2 uptake measurements with the thyroid Hormone-specific Transporter MCT8. For both Lat2 and MCT8, Km values in a low micromolar range were calculated. We demonstrated that oocytes are a suitable system for thyroid Hormone Transport studies mediated by Lat2. Our data indicates that Lat2 compared to other thyroid Hormone Transporters prefers 3,3′-T2 as the substrate. Thus, Lat2 might contribute to the availability of thyroid Hormone by importing and/or exporting 3,3′-T2, which is generated either by T3 inactivation or by rapid deiodinase 1-mediated rT3 degradation.
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Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3 ' -Diiodothyronine across the Plasma Membrane
European thyroid journal, 2015Co-Authors: Anita Kinne, Josef Köhrle, Katrin M. Hinz, Eva K. Wirth, Melanie Wittner, Ralf Schülein, Gerd KrauseAbstract:Thyroid Hormones are Transported across cell membranes by transmembrane Transporter proteins, for example by members of the monocarboxylate Transporter (MCT) and the L-type amino acid Transporter (LAT) families. LATs consist of a light chain (e.g. LAT2) and a heavy chain (CD98), which is essential for their cell surface expression and functionality. The specificity of Lat2 for thyroid Hormones and their metabolites and its role in their Transport was not fully clear. This fact motivated us to establish a cell system to elucidate the uptake of thyroid Hormones and their metabolites by mouse Lat2. The coinjection of cRNA coding for Lat2 and CD98 into Xenopus laevis oocytes resulted in a markedly increased level of 3,3'-diiodo-L-thyronine (3,3'-T2) and to some extent also enhanced T3 Transport. To gain insight into properties of thyroid Hormones and their metabolites Transported by Lat2, we inhibited 3,3'-T2 uptake by various iodothyronine derivatives. T1 and T2 derivatives as well as 2-aminobicyclo-[2, 2,1]-heptane-2-carboxylic acid strongly competed with 3,3'-T2 uptake. In addition, we performed T2 uptake measurements with the thyroid Hormone-specific Transporter MCT8. For both Lat2 and MCT8, Km values in a low micromolar range were calculated. We demonstrated that oocytes are a suitable system for thyroid Hormone Transport studies mediated by Lat2. Our data indicates that Lat2 compared to other thyroid Hormone Transporters prefers 3,3'-T2 as the substrate. Thus, Lat2 might contribute to the availability of thyroid Hormone by importing and/or exporting 3,3'-T2, which is generated either by T3 inactivation or by rapid deiodinase 1-mediated rT3 degradation.
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structural insights into thyroid Hormone Transport mechanisms of the l type amino acid Transporter 2
Molecular Endocrinology, 2015Co-Authors: Katrin M. Hinz, Josef Köhrle, Anita Kinne, Ralf Schülein, Katja Meyer, Gerd KrauseAbstract:Thyroid Hormones (THs) are Transported across cell membranes by different transmembrane Transporter proteins. In previous studies, we showed marked 3,3′-diiodothyronine (3,3′-T2) but moderate T3 uptake by the L-type amino acid Transporter 2 (Lat2). We have now studied the structure-function relationships of this Transporter and TH-like molecules. Our Lat2 homology model is based on 2 crystal structures of the homologous 12-transmembrane helix Transporters arginine/agmatine antiporter and amino acid/polyamine/organocation Transporter. Model-driven mutagenesis of residues lining an extracellular recognition site and a TH-traversing channel identified 9 sensitive residues. Using Xenopus laevis oocytes as expression system, we found that side chain shortening (N51S, N133S, N248S, and Y130A) expanded the channel and increased 3,3′-T2 Transport. Side chain enlargements (T140F, Y130R, and I137M) decreased 3,3′-T2 uptake, indicating channel obstructions. The opposite results with mutations maintaining (F242W) or ...
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essential molecular determinants for thyroid Hormone Transport and first structural implications for monocarboxylate Transporter 8
Journal of Biological Chemistry, 2010Co-Authors: Anita Kinne, Josef Köhrle, Gerd Krause, Gunnar Kleinau, Carolin S Hoefig, Annette Gruters, Ulrich SchweizerAbstract:Monocarboxylate Transporter 8 (MCT8, SLC16A2) is a thyroid Hormone (TH) transmembrane Transport protein mutated in Allan-Herndon-Dudley syndrome, a severe X-linked psychomotor retardation. The neurological and endocrine phenotypes of patients deficient in MCT8 function underscore the physiological significance of carrier-mediated TH transmembrane Transport. MCT8 belongs to the major facilitator superfamily of 12 transmembrane-spanning proteins and mediates energy-independent bidirectional Transport of iodothyronines across the plasma membrane. Structural information is lacking for all TH transmembrane Transporters. To gain insight into structure-function relations in TH Transport, we chose human MCT8 as a paradigm. We systematically performed conventional and liquid chromatography-tandem mass spectrometry-based uptake measurements into MCT8-transfected cells using a large number of compounds structurally related to iodothyronines. We found that human MCT8 is specific for L-iodothyronines and requires at least one iodine atom per aromatic ring. Neither thyronamines, decarboxylated metabolites of iodothyronines, nor triiodothyroacetic acid and tetraiodothyroacetic acid, TH derivatives lacking both chiral center and amino group, are substrates for MCT8. The polyphenolic flavonoids naringenin and F21388, potent competitors for TH binding at transthyretin, did not inhibit T(3) Transport, suggesting that MCT8 can discriminate its ligand better than transthyretin. Bioinformatic studies and a first molecular homology model of MCT8 suggested amino acids potentially involved in substrate interaction. Indeed, alanine mutation of either Arg(445) (helix 8) or Asp(498) (helix 10) abrogated T(3) Transport activity of MCT8, supporting their predicted role in substrate recognition. The MCT8 model allows us to rationalize potential interactions of amino acids including those mutated in patients with Allan-Herndon-Dudley syndrome.