Expression of the activity of cystine/glutamate exchange transporter, system x(c)(-), by xCT and rBAT.
The expression of the activity of cystine/glutamate exchange transporter, designated system x(c)(-), requires two components, xCT and 4F2 heavy chain (4F2hc) in Xenopus oocytes. rBAT (related to b(0,+) amino acid transporter) has a significant homology to 4F2hc and is known to be located in the apical membrane of epithelial cells. To determine whether xCT can associate with rBAT and express the activity of system x(c)(-), xCT, and rBAT were co-expressed in Xenopus oocytes and in mammalian cultured cells. In the oocytes injected with rBAT cRNA alone, the activities of cystine and arginine transport were induced, indicating that the system b(0,+)-like transporter was expressed by associating the exogenous rBAT with an endogenous b(0,+)AT-like factor as reported previously. In the oocytes injected with xCT and rBAT cRNAs, the activity of cystine transport was further induced. This induced activity of cystine transport was partially inhibited by glutamate or arginine and completely inhibited by adding both amino acids. In these oocytes, the activity of glutamate transport was also induced and it was strongly inhibited by cystine. In NIH3T3 cells transfected with xCT cDNA alone, the activity of cystine transport was significantly increased, and in the cells transfected with both xCT and rBAT cDNAs, the activity of cystine transport was further enhanced. The enhanced activity was Na(+)-independent and was inhibited by glutamate and homocysteate. These results indicate that rBAT can replace 4F2hc in the expression of the activity of system x(c)(-) and suggest that system x(c)(-) activity could be expressed in the apical membrane of epithelial cells.
Wang
Hongyu
H
Department of Biochemistry, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
Tamba
Michiko
M
Kimata
Mayumi
M
Sakamoto
Kazuichi
K
Bannai
Shiro
S
Sato
Hideyo
H
D016475:3T3 Cells; D027182:Amino Acid Transport System y+; D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003553:Cystine / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D027282:Fusion Regulatory Protein 1, Heavy Chain / Q000235:genetics / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009865:Oocytes / Q000378:metabolism; D021122:Protein Subunits; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis; D014981:Xenopus
D027182:Amino Acid Transport System y+; D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids; D002352:Carrier Proteins; D027282:Fusion Regulatory Protein 1, Heavy Chain; D008562:Membrane Glycoproteins; D021122:Protein Subunits; D012333:RNA, Messenger; C492255:Slc7a11 protein, mouse; C499488:Slc7a9 protein, mouse; D018698:Glutamic Acid; D003553:Cystine