Basolateral LAT-2 has a major role in the transepithelial flux of L-cystine in the renal proximal tubule cell line OK.
During renal reabsorption, the amino acid transporters b(o,+) and y(+)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(+)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(+)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.
Fernández
Esperanza
E
Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Spain.
Torrents
David
D
Chillarón
Josep
J
Martín Del Río
Rafael
R
Zorzano
Antonio
A
Palacín
Manuel
M
D027062:Amino Acid Transport System L / Q000378:metabolism; D027241:Amino Acid Transport System y+L; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D003545:Cysteine / Q000378:metabolism*; D018076:DNA, Complementary; D004847:Epithelial Cells / Q000378:metabolism*; D027301:Fusion Regulatory Protein 1, Light Chains / Q000235:genetics / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D023421:Models, Animal; D009893:Opossums; D014553:Urinary Tract Physiological Phenomena
D027062:Amino Acid Transport System L; D027241:Amino Acid Transport System y+L; D018076:DNA, Complementary; D027301:Fusion Regulatory Protein 1, Light Chains; C421261:SLC7A7 protein, human; D003545:Cysteine