Characterization of L-glutamine transport by a human neuroblastoma cell line.
This study characterized the Na+-dependent transport of L-glutamine by a human neuroblastoma cell line, SK-N-SH. The Na+-dependent component represented >95% of the total glutamine uptake. Kinetic studies showed a single saturable high-affinity carrier with a Michaelis constant (K(m)) of 163 +/- 23 microM and a maximum transport velocity (Vmax) of 13,713 +/- 803 pmol x mg protein(-1) x min(-1). Glutamine uptake was markedly inhibited in the presence of L-alanine, L-asparagine, and L-serine. Li+ did not substitute for Na+. These data show that L-glutamine is predominantly taken up through system ASC. Glutamine deprivation resulted in the decrease of glutamine transport by a mechanism that decreased Vmax without affecting K(m). The expression of the system ASC subtype ASCT2 decreased in the glutamine-deprived group, whereas glutamine deprivation did not induce changes in system ASC subtype ASCT1 mRNA expression. Adaptive increases in Na+-dependent glutamate, Na+-dependent 2-(methylamino)isobutyric acid, and Na+-independent leucine transport were observed under glutamine-deprived conditions, which were completely blocked by actinomycin D and cycloheximide. These mechanisms may allow cells to survive and even grow under nutrient-deprived conditions.
Wasa
Masafumi
M
Department of Pediatric Surgery, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan. wasa@pedsurg.med.osaka-u.ac.jp
Wang
Hong-Sheng
HS
Okada
Akira
A
D026962:Amino Acid Transport System ASC / Q000235:genetics / Q000378:metabolism; D000596:Amino Acids / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002794:Choline / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism* / Q000493:pharmacokinetics / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008094:Lithium / Q000494:pharmacology; D015778:Minor Histocompatibility Antigens; D009447:Neuroblastoma / Q000378:metabolism*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D014407:Tumor Cells, Cultured
D026962:Amino Acid Transport System ASC; D000596:Amino Acids; D015778:Minor Histocompatibility Antigens; D019384:Nucleic Acid Synthesis Inhibitors; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; C498848:SLC1A4 protein, human; C420506:SLC1A5 protein, human; D005973:Glutamine; D008094:Lithium; D012964:Sodium; D002794:Choline