scholarly journals Effective Cellular Uptake and Efflux of Thyroid Hormone by Human Monocarboxylate Transporter 10

2008 ◽  
Vol 22 (6) ◽  
pp. 1357-1369 ◽  
Author(s):  
Edith C. H. Friesema ◽  
Jurgen Jansen ◽  
Jan-willem Jachtenberg ◽  
W. Edward Visser ◽  
Monique H. A. Kester ◽  
...  
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Thyroid Hormone ◽  
Cellular Uptake ◽  
Aromatic Amino Acids ◽  
Significant Inhibition ◽  
Monocarboxylate Transporter ◽  
Strong Increase ◽  
Type I ◽  
Hormone Binding Protein

Abstract Cellular entry of thyroid hormone is mediated by plasma membrane transporters, among others a T-type (aromatic) amino acid transporter. Monocarboxylate transporter 10 (MCT10) has been reported to transport aromatic amino acids but not iodothyronines. Within the MCT family, MCT10 is most homologous to MCT8, which is a very important iodothyronine transporter but does not transport amino acids. In view of this paradox, we decided to reinvestigate the possible transport of thyroid hormone by human (h) MCT10 in comparison with hMCT8. Transfection of COS1 cells with hMCT10 cDNA resulted in 1) the production of an approximately 55 kDa protein located to the plasma membrane as shown by immunoblotting and confocal microscopy, 2) a strong increase in the affinity labeling of intracellular type I deiodinase by N-bromoacetyl-[125I]T3, 3) a marked stimulation of cellular T4 and, particularly, T3 uptake, 4) a significant inhibition of T3 uptake by phenylalanine, tyrosine, and tryptophan of 12.5%, 22.2%, and 51.4%, respectively, and 5) a marked increase in the intracellular deiodination of T4 and T3 by different deiodinases. Cotransfection studies using the cytosolic thyroid hormone-binding protein μ-crystallin (CRYM) indicated that hMCT10 facilitates both cellular uptake and efflux of T4 and T3. In the absence of CRYM, hMCT10 and hMCT8 increased T3 uptake after 5 min incubation up to 4.0- and 1.9-fold, and in the presence of CRYM up to 6.9- and 5.8-fold, respectively. hMCT10 was less active toward T4 than hMCT8. These findings establish that hMCT10 is at least as active a thyroid hormone transporter as hMCT8, and that both transporters facilitate iodothyronine uptake as well as efflux.

Age-related changes in renal and hepatic cellular mechanisms associated with variations in rat serum thyroid hormone levels

2008 ◽  
Vol 294 (6) ◽  
pp. E1160-E1168 ◽  
Author(s):  
Elena Silvestri ◽  
Assunta Lombardi ◽  
Pieter de Lange ◽  
Luigi Schiavo ◽  
Antonia Lanni ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Total Protein ◽  
Protein Level ◽  
Monocarboxylate Transporter ◽  
Type I ◽  
Peripheral Tissues ◽  
Protein Levels ◽  
Age Related ◽  
Liver And Kidney ◽  
Age Related Changes

Aging is associated with changes in thyroid gland physiology. Age-related changes in the contribution of peripheral tissues to thyroid hormone serum levels have yet to be systematically assessed. Here, we investigated age-related alterations in the contributions of the liver and kidney to thyroid hormone homeostasis using 6-, 12-, and 24-mo-old male Wistar rats. A significant and progressive decline in plasma thyroxine occurred with age, but triiodothyronine (T3) was decreased only at 24 mo. This was associated with an unchanged protein level of the thyroid hormone transporter monocarboxylate transporter 8 (MCT8) in the kidney and with a decreased MCT8 level in the liver at 24 mo. Hepatic type I deiodinase (D1) protein level and activity declined progressively with age. Renal D1 levels were decreased at both 12 and 24 mo but D1 activity was decreased only at 24 mo. In the liver, no changes occurred in thyroid hormone receptor (TR) TRα1, whereas a progressive increase in TRβ1 occurred at both mRNA and total protein levels. In the kidney, both TRα1 and TRβ1 mRNA and total protein levels were unchanged between 6 and 12 mo but increased at 24 mo. Interestingly, nuclear TRβ1 levels were decreased in both liver and kidney at 12 and 24 mo, whereas nuclear TRα1 levels were unchanged. Collectively, our data show differential age-related changes among hepatic and renal MCT8 and D1 and TR expressions, and they suggest that renal D1 activity is maintained with age to compensate for the decrease in hepatic T3 production.

scholarly journals Genotype-Phenotype Relationship in Patients with Mutations in Thyroid Hormone Transporter MCT8

Endocrinology ◽  
2008 ◽  
Vol 149 (5) ◽  
pp. 2184-2190 ◽  
Author(s):  
Jurgen Jansen ◽  
Edith C. H. Friesema ◽  
Monique H. A. Kester ◽  
Charles E. Schwartz ◽  
Theo J. Visser
Keyword(s):  
Plasma Membrane ◽  
Thyroid Hormone ◽  
Protein Expression ◽  
Elevated Serum ◽  
Monocarboxylate Transporter ◽  
Psychomotor Development ◽  
Substrate Affinity ◽  
Loss Of Function ◽  
Wild Type ◽  
Rt Pcr

Loss-of-function mutations in thyroid hormone transporter monocarboxylate transporter 8 (MCT8) lead to severe X-linked psychomotor retardation and elevated serum T3 levels. Most patients, for example those with mutations V235M, S448X, insI189, or delF230, cannot stand, walk, or speak. Patients with mutations L434W, L568P, and S194F, however, walk independently and/or develop some dysarthric speech. To study the relationship between mutation and phenotype, we transfected JEG3 and COS1 cells with wild-type or mutant MCT8. Expression and function of the transporter were studied by analyzing T3 and T4 uptake, T3 metabolism (by cotransfected type 3 deiodinase), Western blotting, affinity labeling with N-bromoacetyl-T3, immunocytochemistry, and quantitative RT-PCR. Wild-type MCT8 increased T3 uptake and metabolism about 5-fold compared with empty vector controls. Mutants V235M, S448X, insI189, and delF230 did not significantly increase transport. However, S194F, L568P, and L434W showed about 20, 23, and 37% of wild-type activity. RT-PCR did not show significant differences in mRNA expression between wild-type and mutant MCT8. Immunocytochemistry detected the nonfunctional mutants V235M, insI189, and delF230 mostly in the cytoplasm, whereas mutants with residual function were expressed at the plasma membrane. Mutants S194F and L434W showed high protein expression but low affinity for N-bromoacetyl-T3; L568P was detected in low amounts but showed relatively high affinity. Mutations in MCT8 cause loss of function through reduced protein expression, impaired trafficking to the plasma membrane, or reduced substrate affinity. Mutants L434W, L568P, and S194F showed significant residual transport capacity, which may underlie the more advanced psychomotor development observed in patients with these mutations.

scholarly journals Truncations of the C-terminal cytoplasmic domain of MG160, a medial Golgi sialoglycoprotein, result in its partial transport to the plasma membrane and filopodia

1998 ◽  
Vol 111 (2) ◽  
pp. 249-260 ◽  
Author(s):  
J.O. Gonatas ◽  
Y.J. Chen ◽  
A. Stieber ◽  
Z. Mourelatos ◽  
N.K. Gonatas
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Golgi Apparatus ◽  
Cell Surface ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Growth Factor Receptor ◽  
Cytoplasmic Domain ◽  
Type I ◽  
Ovary Cells

MG160, a type I cysteine-rich membrane sialoglycoprotein residing in the medial cisternae of the rat Golgi apparatus, is highly homologous to CFR, a fibroblast growth factor receptor, and ESL-1, an E-selectin ligand located at the cell surface of mouse myeloid cells and recently detected in the Golgi apparatus as well. The mechanism for the transport of MG160 from the Golgi apparatus to the cell surface is unknown. In this study we found that differential processing of the carboxy-terminal cytoplasmic domain (CD), consisting of amino acids Arg1159 Ile Thr Lys Arg Val Thr Arg Glu Leu Lys Asp Arg1171, resulted in the partial transport of the protein to the plasma membrane and filopodia. In Chinese hamster ovary cells (CHO), stably transfected with the entire cDNA encoding MG160, the protein was localized in the Golgi apparatus. However, when the terminal Arg1171 or up to nine distal amino acids were deleted, the protein was distributed to the plasma membrane and filopodia as well as the Golgi apparatus. This report shows that the CD of an endogenous type I Golgi protein is important for its efficient retention and identifies a unique residue preference in this process. Cleavage within the CD of MG160 may constitute a regulatory mechanism for the partial export of the protein from the Golgi apparatus to the plasma membrane and filopodia.

scholarly journals Aminoaciduria, but normal thyroid hormone levels and signalling, in mice lacking the amino acid and thyroid hormone transporter Slc7a8

2011 ◽  
Vol 439 (2) ◽  
pp. 249-255 ◽  
Author(s):  
Doreen Braun ◽  
Eva K. Wirth ◽  
Franziska Wohlgemuth ◽  
Nathalie Reix ◽  
Marc O. Klein ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Cell Types ◽  
Monocarboxylate Transporter ◽  
Functional Compensation ◽  
Neutral Amino Acids ◽  
System L ◽  
Neurological Phenotype

LAT2 (system L amino acid transporter 2) is composed of the subunits Slc7a8/Lat2 and Slc3a2/4F2hc. This transporter is highly expressed along the basolateral membranes of absorptive epithelia in kidney and small intestine, but is also abundant in the brain. Lat2 is an energy-independent exchanger of neutral amino acids, and was shown to transport thyroid hormones. We report in the present paper that targeted inactivation of Slc7a8 leads to increased urinary loss of small neutral amino acids. Development and growth of Slc7a8−/− mice appears normal, suggesting functional compensation of neutral amino acid transport by alternative transporters in kidney, intestine and placenta. Movement co-ordination is slightly impaired in mutant mice, although cerebellar development and structure remained inconspicuous. Circulating thyroid hormones, thyrotropin and thyroid hormone-responsive genes remained unchanged in Slc7a8−/− mice, possibly because of functional compensation by the thyroid hormone transporter Mct8 (monocarboxylate transporter 8), which is co-expressed in many cell types. The reason for the mild neurological phenotype remains unresolved.

scholarly journals Translational diffusion of class II major histocompatibility complex molecules is constrained by their cytoplasmic domains.

1989 ◽  
Vol 109 (6) ◽  
pp. 3325-3331 ◽  
Author(s):  
W F Wade ◽  
J H Freed ◽  
M Edidin
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Major Histocompatibility Complex ◽  
Cytoplasmic Domain ◽  
Translational Diffusion ◽  
Type I ◽  
Beta Chain ◽  
Wild Type ◽  
Alpha Chain ◽  
Histocompatibility Complex

Site-directed mutagenesis in vitro was used to introduce stop codons in the genomic DNA of the alpha and beta chains of the murine class II major histocompatibility complex antigen, I-Ak. Mutated DNA was transfected into B lymphoma cells that were then selected by neomycin resistance and for their ability to express I-Ak molecules on their plasma membrane. The translational diffusion coefficient (Dlat) of I-Ak molecules composed of a wild-type beta chain paired with an alpha chain missing either 6 or 12 amino acids from the cytoplasmic domain is on the average threefold higher than the Dlat of wild-type I-Ak molecules as measured by fluorescence photobleaching and recovery. The removal of 12 amino acids from the cytoplasmic domain of the beta chain did not change the Dlat value from that of wild-type I-Ak if the truncated beta chain was paired with a wild-type alpha chain. Removing all amino acids of the cytoplasmic domains of both the alpha and beta chains resulted in a 10-fold increase in the Dlat, the highest value for any of the truncated I-Ak molecules tested. These data indicate that the carboxy-terminal six amino acids of the cytoplasmic domain of the alpha chain and the six plasma membrane-proximal amino acids of the beta chain are important in constraining the translational diffusion of I-Ak molecules in the plasma membrane.

scholarly journals Flexibility of equine bioenergetics and muscle plasticity in response to different types of training: An integrative approach, questioning existing paradigms

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0249922
Author(s):  
Constance de Meeûs d’Argenteuil ◽  
Berit Boshuizen ◽  
Maarten Oosterlinck ◽  
Don van de Winkel ◽  
Ward De Spiegelaere ◽  
...  
Keyword(s):  
Amino Acids ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Aromatic Amino Acids ◽  
Treadmill Training ◽  
Integrative Approach ◽  
Type I ◽  
Cross Sectional ◽  
Branched Chain ◽  
Type I Fibers

Equine bioenergetics have predominantly been studied focusing on glycogen and fatty acids. Combining omics with conventional techniques allows for an integrative approach to broadly explore and identify important biomolecules. Friesian horses were aquatrained (n = 5) or dry treadmill trained (n = 7) (8 weeks) and monitored for: evolution of muscle diameter in response to aquatraining and dry treadmill training, fiber type composition and fiber cross-sectional area of the M. pectoralis, M. vastus lateralis and M. semitendinosus and untargeted metabolomics of the M. pectoralis and M. vastus lateralis in response to dry treadmill training. Aquatraining was superior to dry treadmill training to increase muscle diameter in the hindquarters, with maximum effect after 4 weeks. After dry treadmill training, the M. pectoralis showed increased muscle diameter, more type I fibers, decreased fiber mean cross sectional area, and an upregulated oxidative metabolic profile: increased β-oxidation (key metabolites: decreased long chain fatty acids and increased long chain acylcarnitines), TCA activity (intermediates including succinyl-carnitine and 2-methylcitrate), amino acid metabolism (glutamine, aromatic amino acids, serine, urea cycle metabolites such as proline, arginine and ornithine) and xenobiotic metabolism (especially p-cresol glucuronide). The M. vastus lateralis expanded its fast twitch profile, with decreased muscle diameter, type I fibers and an upregulation of glycolytic and pentose phosphate pathway activity, and increased branched-chain and aromatic amino acid metabolism (cis-urocanate, carnosine, homocarnosine, tyrosine, tryptophan, p-cresol-glucuronide, serine, methionine, cysteine, proline and ornithine). Trained Friesians showed increased collagen and elastin turn-over. Results show that branched-chain amino acids, aromatic amino acids and microbiome-derived xenobiotics need further study in horses. They feed the TCA cycle at steps further downstream from acetyl CoA and most likely, they are oxidized in type IIA fibers, the predominant fiber type of the horse. These study results underline the importance of reviewing existing paradigms on equine bioenergetics.

Effect of hypothyroidism on pathways for iodothyronine and tryptophan uptake into rat adipocytes

2001 ◽  
Vol 280 (2) ◽  
pp. E254-E259 ◽  
Author(s):  
James W. A. Ritchie ◽  
Charmian J. F. Collingwood ◽  
Peter M. Taylor
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Thyroid Hormone ◽  
Aromatic Amino Acids ◽  
Target Tissue ◽  
Large Neutral Amino Acid ◽  
Major Pathway ◽  
Transport Component ◽  
System L ◽  
Adipocyte Cell

Adipocytes are an important target tissue for thyroid hormone action, but little is known of the mechanisms of thyroid hormone entry into the cells. The present results show a strong interaction between transport of iodothyronines [l-thyroxine (T4),l-triiodothyronine (T3), reverset3 (rT3)], aromatic amino acids, and the System L amino acid transport inhibitor 2-amino[2,2,1]heptane-2-carboxylic acid (BCH) in white adipocytes. System L appears to be a major pathway of iodothyronine and large neutral amino acid entry into these cells in the euthyroid state. We also demonstrate expression of the CD98hc peptide subunit of the System L transporter in adipocyte cell membranes. Experimental hypothyroidism (28-day propylthiouracil treatment) has no significant effect on Systeml-like transport of the amino acid tryptophan in adipocytes. In contrast, uptake of T3 and especially T4 is substantially reduced in adipocytes from hypothyroid rats, partly due to reduction of the BCH-sensitive transport component. Transport of iodothyronines and amino acids in adipocytes therefore becomes decoupled in the hypothyroid state, as occurs similarly in liver cells. This may be due to downregulation or dissociation of iodothyronine receptors from the System L transporter complex. Regulation of iodothyronine turnover in fat cells by this type of mechanism could contribute significantly to modulation of T4-T3/rT3 metabolism in the hypothyroid state.

scholarly journals Few Amino Acid Exchanges Expand the Substrate Spectrum of Monocarboxylate Transporter 10*

2016 ◽  
Vol 30 (7) ◽  
pp. 796-808 ◽  
Author(s):  
Jörg Johannes ◽  
Doreen Braun ◽  
Anita Kinne ◽  
Daniel Rathmann ◽  
Josef Köhrle ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Aromatic Amino Acids ◽  
Homology Model ◽  
Amino Acid Identity ◽  
Psychomotor Retardation ◽  
Major Facilitator Superfamily ◽  
Monocarboxylate Transporter ◽  
Amino Acid Substitutions ◽  
Major Facilitator

Monocarboxylate transporters (MCTs) belong to the SLC16 family within the major facilitator superfamily of transmembrane transporters. MCT8 is a thyroid hormone transporter mutated in the Allan-Herndon-Dudley syndrome, a severe psychomotor retardation syndrome. MCT10 is closely related to MCT8 and is known as T-type amino acid transporter. Both transporters mediate T3 transport, but although MCT8 also transports rT3 and T4, these compounds are not efficiently transported by MCT10, which, in contrast, transports aromatic amino acids. Based on the 58% amino acid identity within the transmembrane regions among MCT8 and MCT10, we reasoned that substrate specificity may be primarily determined by a small number of amino acid differences between MCT8 and MCT10 along the substrate translocation channel. Inspecting the homology model of MCT8 and a structure-guided alignment between both proteins, we selected 8 amino acid positions and prepared chimeric MCT10 proteins with selected amino acids changed to the corresponding amino acids in MCT8. The MCT10 mutant harboring 8 amino acid substitutions was stably expressed in Madin-Darby canine kidney 1 cells and found to exhibit T4 transport activity. We then successively reduced the number of amino acid substitutions and eventually identified a minimal set of 2–3 amino acid exchanges which were sufficient to allow T4 transport. The resulting MCT10 chimeras exhibited KM values for T4 similar to MCT8 but transported T4 at a slower rate. The acquisition of T4 transport by MCT10 was associated with complete loss of the capacity to transport Phe, when Tyr184 was mutated to Phe.

scholarly journals The targeting of Lamp1 to lysosomes is dependent on the spacing of its cytoplasmic tail tyrosine sorting motif relative to the membrane.

1996 ◽  
Vol 132 (4) ◽  
pp. 565-576 ◽  
Author(s):  
J Rohrer ◽  
A Schweizer ◽  
D Russell ◽  
S Kornfeld
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Amino Acid ◽  
Cytoplasmic Tail ◽  
Kinetic Studies ◽  
Type I ◽  
Trans Golgi Network ◽  
Intracellular Targeting ◽  
Sorting Motif ◽  
Golgi Network

Lamp1 is a type I transmembrane glycoprotein that is localized primarily in lysosomes and late endosomes. Newly synthesized molecules are mostly transported from the trans-Golgi network directly to endosomes and then to lysosomes. A minor pathway involves transport via the plasma membrane. The 11-amino acid cytoplasmic tail of lamp1 contains a tyrosine-based motif that has been previously shown to mediate sorting in the trans-Golgi network and rapid internalization at the plasma membrane. We studied whether this motif also mediates sorting in endosomes. We found that mutant forms of lamp1 in which all the amino acids of the cytoplasmic tail were modified except for the RKR membrane anchor and the YXXI sorting motif still localized to dense lysosomes, indicating that the YXXI motif is sufficient to confer proper intracellular targeting. However, when the spacing of the YXXI motif relative to the membrane was changed by deleting one amino acid or adding five amino acids, lysosomal targeting was almost completely abolished. Kinetic studies showed that these mutants were trapped in a recycling pathway, involving trafficking between the plasma membrane and early endocytic compartments. These findings indicate that the YXXI signal of lamp1 is recognized at several sorting sites, including the trans-Golgi network, the plasma membrane, and the early/sorting endosomes. Small changes in the spacing of this motif relative to the membrane dramatically impair sorting in the early/sorting endosomes but have only a modest effect on internalization at the plasma membrane. The spacing of sorting signals relative to the membrane may prove to be an important determinant in the functioning of these signals.

scholarly journals High T3, Low T4 Serum Levels in Mct8 Deficiency Are Not Caused by Increased Hepatic Conversion through Type I Deiodinase

2015 ◽  
Vol 4 (Suppl. 1) ◽  
pp. 87-91 ◽  
Author(s):  
Eva K. Wirth ◽  
Eddy Rijntjes ◽  
Franziska Meyer ◽  
Josef Köhrle ◽  
Ulrich Schweizer
Keyword(s):  
Thyroid Hormone ◽  
Serum Levels ◽  
Underlying Mechanism ◽  
Psychomotor Retardation ◽  
Monocarboxylate Transporter ◽  
Type I ◽  
Hormone Levels ◽  
Thyroid Hormone Levels ◽  
Mct8 Deficiency ◽  
Deficient Mice

Background: The Allan-Herndon-Dudley syndrome is a severe psychomotor retardation accompanied by specific changes in circulating thyroid hormone levels (high T3, low T4). These are caused by mutations in the thyroid hormone transmembrane transport protein monocarboxylate transporter 8 (MCT8). Objective: To test the hypothesis that circulating low T4 and high T3 levels are caused by enhanced conversion of T4 via increased activity of hepatic type I deiodinase (Dio1). Methods: We crossed mice deficient in Mct8 with mice lacking Dio1 activity in hepatocytes. Translation of the selenoenzyme Dio1 was abrogated by hepatocyte-specific inactivation of selenoprotein biosynthesis. Results: Inactivation of Dio1 activity in the livers of global Mct8-deficient mice does not restore normal circulating thyroid hormone levels. Conclusions: Our data suggest that although hepatic Dio1 activity is increased in Mct8-deficient mice, it does not cause the observed abnormal circulating thyroid hormone levels. Since global inactivation of Dio1 in Mct8-deficient mice does normalize circulating thyroid hormone levels, the underlying mechanism and relevant tissues involved remain to be elucidated.

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