Accumulation of free amino acids in growing Xenopus laevis oocytes

Ma, Taylor; Ld, Smith

doi:10.1016/0012-1606(87)90480-5

Cited by 38 publications

(39 citation statements)

References 12 publications

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“…Here we demonstrate that the amino acid transport activity induced by human rBAT in oocytes can be fully explained by system b o,ϩ -like activity, as We have also shown that the amino acid exchange activity of system b o,ϩ -like is tightly coupled and allows intracellular concentration of amino acid substrates until the complete replacement of the internal system b o,ϩ -like substrates of the oocyte. The maximum level of accumulation of substrates via system b o,ϩ -like (ϳ1,000 pmol/oocyte) fits well with the reported content of free amino acid substrates of this system in stage VI oocytes (31). Interestingly, the level of accumulation of substrates at low M concentration reached in rBAT-injected oocytes exceeds that obtained in uninjected or in CAT1-injected oocytes (i.e.…”

Section: Amino Acid Exchange Via Systems B Oϩ and Y ϩ L-likesupporting

confidence: 69%

“…If the accumulation of substrates via system b o,ϩ -like is due to exchange with the intracellular oocyte substrates, their total oocyte content (ϳ1,000 pmol/oocyte; Ref. 31) would limit this accumulation. The increase in L-[ 3 H]arginine concentration from 10 to 1,000 M resulted in a nonlinear increase in Larginine accumulation, which reached a maximum of Յ1,000 pmol/oocyte at ϳ500 M L-arginine (Fig.…”

Section: Methodsmentioning

confidence: 99%

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Obligatory Amino Acid Exchange via Systems bo,+-like and y+L-like

Chillarón

Estévez

Mora

et al. 1996

Journal of Biological Chemistry

162

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Section: Amino Acid Exchange Via Systems B Oϩ and Y ϩ L-likesupporting

confidence: 69%

Section: Methodsmentioning

confidence: 99%

Obligatory Amino Acid Exchange via Systems bo,+-like and y+L-like

Chillarón

Estévez

Mora

et al. 1996

Journal of Biological Chemistry

162

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“…Moreover, the expression of human 4F2hc and xCT alone or in combination did not change the oocyte content of L-glutamate (Table 1). This free L-glutamate pool is very large; in comparison the L-aspartate and cystine/cysteine content is almost negligible [59]. Taken together, these results and the fact that the Hill coefficient of the glutamate transport is close to 1 (see above), indicates that cystine/glutamate exchange via the human amino acid transporter 4F2hc/xCT occurred at a 1:1 molar ratio.…”

Section: Glutamatementioning

confidence: 71%

Identification and characterisation of human xCT that co-expresses, with 4F2 heavy chain, the amino acid transport activity system x c -

Bassi

Gasol

Manzoni

et al. 2001

Pfl�gers Archiv European Journal of Physiology

136

101

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We have identified a new human complementary deoxyribonucleic acid (cDNA), for the xc- amino acid transporter (HGMW-approved name SLC7A11; also known as human xCT), that, when co-expressed with the heavy chain of surface antigen 4F2 (4F2hc, also termed CD98), but not with rBAT, (related to the bo,+ amino acid transporter), induces system xc- transport activity in Xenopus oocytes. Human xCT is the seventh human member of the family of amino acid transporters that are subunits of 4F2hc or rBAT and, inview of its amino acid sequence identity (89%) with mouse xCT, is most probably the human orthologue thereof. The amino acid transport activity induced by the co-expression of human 4F2hc and xCT in Xenopus oocytes was sodium independent and specific for L-cystine, L-glutamate and L-aspartate. This activity also functioned in an exchange mode (e.g. cystine/glutamate) with a substrate stoichiometry of 1:1. Expression of human xCT alone in oocytes did not induce amino acid transport activity and the expressed xCT protein was localised intracellularly. When human xCT was co-expressed with 4F2hc, the former localised to the oocyte plasma membrane. Tissue-expression studies showed that human SLC7A11 mRNA is expressed mainly in the brain, but also in pancreas and in cultured cell lines. The transport characteristics of human xCT and the distribution of its tissue expression strongly suggest that it corresponds to the human amino acid transporter system xc-.

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“…This fragment of hRS1 is known to decrease the abundance of human SGLT1 in the trans-Golgi network in a post-transcriptional manner (Korn et al, 2001). With the assumption that the aqueous volume of oocytes is 0.4 l (Taylor and Smith, 1987), the concentration of GSThRS1-F is estimated to have been ϳ1 M. Figure 4B indicates that the expression of the three hCNTs was inhibited by ϳ50%. To prove that the post-transcriptional inhibition of hCNTs occurred at the trans-Golgi network, we measured the effect of GST-hRS1-F on the expression of hCNT1, hCNT2, and hCNT3 in the presence of the trans-Golgi network inhibitor brefeldin.…”

Section: Resultsmentioning

confidence: 99%

Role of the Transporter Regulator Protein (RS1) in the Modulation of Concentrative Nucleoside Transporters (CNTs) in Epithelia

Errasti-Murugarren

Fernández-Calotti²,

Veyhl-Wichmann³

et al. 2012

Molecular Pharmacology

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SLC28 genes encode three plasma membrane transporter proteins, human concentrative nucleoside transporter (CNT)1, CNT2, and CNT3, all of which are implicated in the uptake of natural nucleosides and a variety of nucleoside analogs used in the chemotherapy of cancer and viral and inflammatory diseases. Mechanisms determining their trafficking toward the plasma membrane are not well known, although this might eventually become a target for therapeutic intervention. The transporter regulator RS1, which was initially identified as a short-term, post-transcriptional regulator of the high-affinity, Na ϩ -coupled, glucose transporter sodium-dependent glucose cotransporter 1, was evaluated in this study as a candidate for coordinate regulation of membrane insertion of human CNTtype proteins. With a combination of studies with mammalian cells, Xenopus laevis oocytes, and RS1-null mice, evidence that RS1 down-regulates the localization and activity at the plasma membrane of the three members of this protein family (CNT1, CNT2, and CNT3) is provided, which indicates the biochemical basis for coordinate regulation of nucleoside uptake ability in epithelia and probably in other RS1-expressing cell types.

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Accumulation of free amino acids in growing Xenopus laevis oocytes

Cited by 38 publications

References 12 publications

Obligatory Amino Acid Exchange via Systems bo,+-like and y+L-like

Obligatory Amino Acid Exchange via Systems bo,+-like and y+L-like

Identification and characterisation of human xCT that co-expresses, with 4F2 heavy chain, the amino acid transport activity system x c -

Role of the Transporter Regulator Protein (RS1) in the Modulation of Concentrative Nucleoside Transporters (CNTs) in Epithelia

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