Amino acid transport of y+L-type by heterodimers of 4F2hc/CD98 and members of the glycoprotein-associated amino acid transporter family

Pfeiffer, Rahel; Rossier, Grégoire; Spindler, Benjamin; Meier, Christian; Kühn, Lukas C.; Verrey, François

doi:10.1093/emboj/18.1.49

Cited by 241 publications

(217 citation statements)

References 38 publications

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“…The band shift from 140 kDa to 40 kDa was presumably due to the breakage of a disulfide bridge between AGT1 and its heavy chain in the reducing condition. The band over 240 kDa seems to be oligomers of heteromeric complexes similar to those observed for HATs (5,(18)(19)(20).…”

Section: Resultssupporting

confidence: 70%

Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Nagamori

Wiriyasermkul

Guarch

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Heterodimeric amino acid transporters play crucial roles in epithelial transport, as well as in cellular nutrition. Among them, the heterodimer of a membrane protein b 0,+ AT/SLC7A9 and its auxiliary subunit rBAT/ SLC3A1 is responsible for cystine reabsorption in renal proximal tubules. The mutations in either subunit cause cystinuria, an inherited amino aciduria with impaired renal reabsorption of cystine and dibasic amino acids. However, an unsolved paradox is that rBAT is highly expressed in the S3 segment, the late proximal tubules, whereas b 0,+ AT expression is highest in the S1 segment, the early proximal tubules, so that the presence of an unknown partner of rBAT in the S3 segment has been proposed. In this study, by means of coimmunoprecipitation followed by mass spectrometry, we have found that a membrane protein AGT1/SLC7A13 is the second partner of rBAT. AGT1 is localized in the apical membrane of the S3 segment, where it forms a heterodimer with rBAT. Depletion of rBAT in mice eliminates the expression of AGT1 in the renal apical membrane. We have reconstituted the purified AGT1-rBAT heterodimer into proteoliposomes and showed that AGT1 transports cystine, aspartate, and glutamate. In the apical membrane of the S3 segment, AGT1 is suggested to locate itself in close proximity to sodium-dependent acidic amino acid transporter EAAC1 for efficient functional coupling. EAAC1 is proposed to take up aspartate and glutamate released into luminal fluid by AGT1 due to its countertransport so that preventing the urinary loss of aspartate and glutamate. Taken all together, AGT1 is the long-postulated second cystine transporter in the S3 segment of proximal tubules and a possible candidate to be involved in isolated cystinuria.amino acid transporter | cystine reabsorption | cystinuria | kidney T he heteromeric amino acid transporter (HAT) family is one of the major amino acid transporter families responsible for cellular uptake and epithelial transport (1-3). HATs form heterodimers composed of a 12 membrane spanning light chain (SLC7) that catalyzes transport functions and a single membrane spanning heavy chain (SLC3) essential for plasma membrane localization and stabilization of the light chains. Two heavy chains, SLC3A1/ rBAT and SLC3A2/4F2hc/CD98hc, covalently bound to light chains via a disulfide bridge have been identified so far (4-6). 4F2hc interacts with most of the light chains in HATs whereas rBAT has been known to form a heterodimer only with b 0,+ AT/ SLC7A9. Because the rBAT-b 0,+ AT complex is presented on the apical membrane of proximal tubules in the kidney and involved in the reabsorption of cystine and dibasic amino acids, the mutations of either rBAT or b 0,+ AT cause cystinuria, a disorder of renal reabsorption of cystine and dibasic amino acids leading to serious renal lithiasis due to low solubility of cystine (7).An unsolved paradox on rBAT and b 0,+ AT has been the discrepancy between the distribution of rBAT and that of b 0,+ AT (5,(8)(9)(10). rBAT is the most abundant in the S3 segmen...

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Section: Resultssupporting

confidence: 70%

Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Nagamori

Wiriyasermkul

Guarch

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The trans-stimulation effect of L-leucine was blunted in the absence of Na ϩ . This activity is similar to y ϩ LAT-1/4F2hc activity when both are coexpressed in oocytes (12)(13)(14). Basolateral efflux of L-arginine via system y ϩ L was already detected 3 d after seeding the cells on the filters.…”

Section: Ok Cells Express Lat-2 and Y ϩ Lat-1 Related Transport Activsupporting

confidence: 59%

“…Indeed, mutations in the rBAT (SLC3A1) gene cause type I cystinuria, and mutations in the b o,ϩ AT (SLC7A9) gene cause mainly non-type I and also type I cystinuria (recessive inherited aminoacidurias of cystine and dibasic amino acids) (6,10,11). Second, y ϩ LAT-1 dimerizes with 4F2hc to form the amino acid transporter y ϩ L, which mediates the efflux of cationic amino acids coupled with the influx of neutral amino acids plus sodium (12)(13)(14). Mutations in y ϩ LAT-1 (SLC7A7) cause lysinuric protein intolerance (15,16), an inherited aminoaciduria due to defective dibasic amino acid efflux from the basolateral membrane of proximal tubule epithelial cells (17).…”

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confidence: 99%

Basolateral LAT-2 Has a Major Role in the Transepithelial Flux of L-Cystine in the Renal Proximal Tubule Cell Line OK

Fernández¹,

Torrents²,

Chillarón³

et al. 2003

Journal of the American Society of Nephrology

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Abstract. During renal reabsorption, the amino acid transporters b o,ϩ and y ϩ L have a major role in the apical uptake of cystine and dibasic amino acids and in the basolateral efflux of dibasic amino acids, respectively. In contrast, the transporters responsible for the basolateral efflux of the apically transported cystine are unknown. This study shows the expression of system L and y ϩ L transport activities in the basolateral domain of the proximal tubule-derived cell line OK and the cloning of the corresponding LAT-2 and y ϩ LAT-1 cDNAs. Stable transfection with a LAT-2 antisense sequence demonstrated the specific role of LAT-2 in the basolateral system L amino acid exchange activity in OK cells. This partial reduction of LAT-2 expression decreased apical-to-basolateral trans-epithelial flux of cystine and resulted in a twofold to threefold increase in the intracellular content of cysteine. In contrast, the content of serine, threonine, and alanine showed a tendency to decrease, whereas other LAT-2 substrates were not affected. This demonstrates that LAT-2 plays a major specific role in the net basolateral efflux of cysteine and points to LAT-2 as a candidate gene to modulate cystine reabsorption.In the kidney, most glomerulus-filtered amino acids are reabsorbed in the early proximal tubule (1). The amino acids are taken up through the brush border membrane and exit the epithelial cells through the basolateral membrane to the interstitial space. Two heteromeric amino acid transport exchangers (systems b o,ϩ and y ϩ L) have a major role in the reabsorption of cystine and dibasic amino acids (2-4). First, the heterodimer formed by rBAT and b o,ϩ AT is the amino acid transporter b o,ϩ , which mediates high-affinity uptake of cystine and dibasic amino acids coupled with the efflux of neutral amino acids (5-8) at the apical membrane of epithelial cells of the proximal tubule (9). Indeed, mutations in the rBAT (SLC3A1) gene cause type I cystinuria, and mutations in the b o,ϩ AT (SLC7A9) gene cause mainly non-type I and also type I cystinuria (recessive inherited aminoacidurias of cystine and dibasic amino acids) (6,10,11). Second, y ϩ LAT-1 dimerizes with 4F2hc to form the amino acid transporter y ϩ L, which mediates the efflux of cationic amino acids coupled with the influx of neutral amino acids plus sodium (12-14). Mutations in y ϩ LAT-1 (SLC7A7) cause lysinuric protein intolerance (15,16), an inherited aminoaciduria due to defective dibasic amino acid efflux from the basolateral membrane of proximal tubule epithelial cells (17). Thus, systems b o,ϩ and y ϩ L explain the trans-epithelial transport of dibasic amino acids. In contrast, the amino acid transporters that play a major role in the basolateral efflux of the apically taken-up cystine remain to be identified.Polarized OK cells, a proximal tubule-derived cell line from the American opossum, has been extensively used as a model for transport studies in renal epithelial cells. Indeed, OK cells express rBAT-associated system b o,ϩ transport activity in the...

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“…9b). DISCUSSION In the present study, we have identified a novel protein (LAT-2) that is structurally related to the formerly identified system L amino acid transporter LAT-1 (18) and system y ϩ L transporters y ϩ LAT-1 and KIAA0245/y ϩ LAT-2 (25,26). LAT-2 transports neutral amino acids in a Na ϩ -independent manner and is sensitive to a system L-specific inhibitor, BCH.…”

Section: Amino Acid Efflux Mediated Via Lat-2-thementioning

confidence: 69%

“…It has been shown that LAT-1 is one of the proteins formerly referred to as 4F2 light chain (22)(23)(24). 4F2hc also associates with y ϩ LAT-1 and KIAA0245/y ϩ LAT-2 system y ϩ L transporters, which accept both neutral and basic amino acids (25,26).…”

Section: 32437-32445) Lat-2 Is a Nonglycosylated Membrane Protementioning

confidence: 99%

Identification and Functional Characterization of a Na+-independent Neutral Amino Acid Transporter with Broad Substrate Selectivity

Segawa¹,

Fukasawa²,

Miyamoto³

et al. 1999

Journal of Biological Chemistry

451

435

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We have isolated a cDNA from rat small intestine that encodes a novel Na ؉ -independent neutral amino acid transporter with distinctive characteristics in substrate selectivity and transport property. The encoded protein, designated L-type amino acid transporter-2 (LAT-2), shows amino acid sequence similarity to the system L Na ؉ -independent neutral amino acid transporter LAT-1 (Kanai, Y., Segawa, H., Miyamoto, K., Uchino, H., Takeda 273, 32437-32445). LAT-2 is a nonglycosylated membrane protein. It requires 4F2 heavy chain, a type II membrane glycoprotein, for its functional expression in Xenopus oocytes. LAT-2-mediated transport is not dependent on Na؉ or Cl ؊ and is inhibited by a system L-specific inhibitor, 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), indicating that LAT-2 is a second isoform of the system L transporter. Compared with LAT-1, which prefers large neutral amino acids with branched or aromatic side chains, LAT-2 exhibits remarkably broad substrate selectivity. It transports all of the L-isomers of neutral ␣-amino acids. LAT-2 exhibits higher affinity (K m ‫؍‬ 30 -50 M) to Tyr, Phe, Trp, Thr, Asn, Ile, Cys, Ser, Leu, Val, and Gln and relatively lower affinity (K m ‫؍‬ 180 -300 M) to His, Ala, Met, and Gly. In addition, LAT-2 mediates facilitated diffusion of substrate amino acids, as distinct from LAT-1, which mediates amino acid exchange. LAT-2-mediated transport is increased by lowering the pH level, with peak activity at pH 6.25, because of the decrease in the K m value without changing the V max value. Because of these functional properties and a high level of expression of LAT-2 in the small intestine, kidney, placenta, and brain, it is suggested that the heterodimeric complex of LAT-2 and 4F2 heavy chain is involved in the trans-cellular transport of neutral amino acids in epithelia and blood-tissue barriers.

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Amino acid transport of y+L-type by heterodimers of 4F2hc/CD98 and members of the glycoprotein-associated amino acid transporter family

Cited by 241 publications

References 38 publications

Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Basolateral LAT-2 Has a Major Role in the Transepithelial Flux of L-Cystine in the Renal Proximal Tubule Cell Line OK

Identification and Functional Characterization of a Na+-independent Neutral Amino Acid Transporter with Broad Substrate Selectivity

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