Discrimination of two amino acid transport activities in 4F2 heavy chain- expressing Xenopus laevis oocytes

Hamprecht, Bernd; Bröer, Stefan

doi:10.1042/bj3330549

Cited by 27 publications

(21 citation statements)

References 35 publications

(45 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This observation is in line with findings from Friesema et al [13], who reported that uptake of iodothyronines by endogenous transporters in oocytes seems to be at least partially sodium dependent. In addition, this correlates to the already mentioned findings where the presence of a sodium-dependent LAT-like transporter in oocytes was reported [21]. …”

Section: Discussionsupporting

confidence: 74%

Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3′-Diiodothyronine across the Plasma Membrane

Kinne¹,

Wittner²,

Wirth³

et al. 2015

Eur Thyroid J

View full text Add to dashboard Cite

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, K_m 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.

show abstract

Section: Discussionsupporting

confidence: 74%

Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3′-Diiodothyronine across the Plasma Membrane

Kinne¹,

Wittner²,

Wirth³

et al. 2015

Eur Thyroid J

View full text Add to dashboard Cite

show abstract

“…It has been shown that the aromatic amino acids Tyr and Trp, which can be transported by both systems L and T, inhibit the uptake of T 3 in neonatal cardiomyocytes and transfected Xenopus oocytes (Everts et al 1996b, Ritchie et al 1999. Only system L is sensitive to the synthetic amino acid analogue BCH (Broer et al 1998, Ritchie et al 1999. Our results show that uptake of T 3 was not sensitive to BCH, from which we conclude that system L does not participate in uptake of T 3 in neonatal rat cardiomyocytes.…”

Section: Discussionsupporting

confidence: 46%

“…125 I]T 3 , cardiomyocytes were preincubated and incubated (15 min) with 0·5 or 2 mM Trp, 0·5 or 2 mM Tyr (substrates for system T and L) or 5 mM BCH, a specific system L inhibitor (Broer et al 1998) (Fig. 4).…”

Section: To Test the Possible Involvement Of Amino Acid Transport Sysmentioning

confidence: 99%

Characterization of uptake and compartmentalization of 3,5,3'-tri-iodothyronine in cultured neonatal rat cardiomyocytes

Putten

Joosten²,

Klaren³

et al. 2001

Journal of Endocrinology

View full text Add to dashboard Cite

The uptake of tri-iodothyronine (T 3 ) in cultured neonatal rat cardiomyocytes was investigated and compared with the uptake of reverse T 3 (rT 3 ) and thyroxine (T 4 ). Cellular compartmentalization of T 3 was studied by distinguishing T 3 activity associated with the plasma membrane from that in the cytosol or incorporated in the cell nucleus. T 3 and T 4 uptake displayed similar temperature dependencies which, in magnitude, differed from that of rT 3 uptake. T 3 uptake was Na + independent, and sensitive to oligomycin and monodansylcadaverine (42-49% and 25% inhibition of 15-min cellular uptake respectively). Furthermore, T 3 uptake could be inhibited by tryptophan (20%) and tyrosine (12%), while 2-aminobicyclo[2,2,1]heptanecarboxylic acid had no effect. Co-incubation with tryptophan and oligomycin resulted in an additive inhibition of T 3 uptake (77%). We therefore conclude that (i) T 3 uptake is energy dependent, (ii) receptor-mediated endocytosis may be involved and (iii) the aromatic amino acid transport system T may play a role, while system L is not involved in T 3 transport in cardiomyocytes. Co-incubation with unlabeled iodothyronines showed that 3,3 -di-iodothyronine and T 3 itself were the most effective inhibitors of T 3 uptake (30% and 36% inhibition of 15-min cellular uptake respectively). At 15-min incubation time, 38% of the total cell-associated T 3 was present in the cytosol and nucleus, and 62% remained associated to the plasma membrane. Unidirectional uptake rates did not saturate over a free T 3 concentration range up to 3·9 µM. We have concluded that T 3 uptake in neonatal rat cardiomyocytes occurs by an energy-and temperaturedependent mechanism that may include endocytosis and amino acid transport system T, and is not sensitive to the Na + gradient. Elucidation of the molecular basis for the T 3 transporter is the subject of current investigation.

show abstract

“…Similar, but more complex is the situation for the amino acid transport systems found after expression of the glycoproteins rBAT (related to b 0,+ amino acid transport) and 4F2hc (4F2 heavy chain, CD98). Expression of 4F2hc in Xenopus oocytes induces at least two distinct amino acid transport activities (corresponding to the amino acid transport systems L and y + L) [38]. This observation was explained after the identification of a new family of amino acid transporters [39].…”

Section: Interaction Of Expressed Proteins With Endogenous Proteinsmentioning

confidence: 99%

The Use of Xenopus laevis Oocytes for the Functional Characterization of Heterologously Expressed Membrane Proteins

Wagner

Friedrich

Setiawan

et al. 2000

Cell Physiol Biochem

Self Cite

173

144

View full text Add to dashboard Cite

The oocytes of the South African clawed frog X. laevis are widely used for the expression of heterologous proteins. The functional characterization of membrane proteins in particular has significantly profited from the use of this expression system. Heterologous cRNA can easily be injected and protein expression and function be studied with several techniques. This review will give a short overview into the variety of methods applicable. They span from different electrophysiological methods such as two electrode voltage clamp, patch clamp and ion-selective electrodes over cytochemistry to protein biochemistry. In spite of the wide usage of Xenopus oocytes, caution should be taken interpreting the results of protein expression. Heterologous proteins may either interact with endogenous proteins, the background of endogenous protein function may be relatively high, or altered protein behaviour may occur due to differences of the ambient temperature or altered cellular environment.

show abstract

Discrimination of two amino acid transport activities in 4F2 heavy chain- expressing Xenopus laevis oocytes

Cited by 27 publications

References 35 publications

Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3′-Diiodothyronine across the Plasma Membrane

Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3′-Diiodothyronine across the Plasma Membrane

Characterization of uptake and compartmentalization of 3,5,3'-tri-iodothyronine in cultured neonatal rat cardiomyocytes

The Use of Xenopus laevis Oocytes for the Functional Characterization of Heterologously Expressed Membrane Proteins

Contact Info

Product

Resources

About