ATA2-mediated amino acid uptake following partial hepatectomy is regulated by redistribution to the plasma membrane.
System A, the Na(+)-dependent amino acid transport activity, is encoded by the ATA2 gene and up-regulated following partial hepatectomy (PH), and its competitive inhibition interferes with liver regeneration. Rabbit polyclonal antibody was raised against a portion of the ATA2 gene product followed by immunodetection of ATA2 in isolated liver plasma membrane and lysate. The level of ATA2 increased in the plasma membrane following PH, while the relatively high quantity of ATA2 found in liver lysate remained constant. We also have shown that Northern analysis of steady-state ATA2 mRNA revealed no significant change following PH. These data show that ATA2-mediated transport is not regulated by the steady-state level of ATA2 mRNA but is regulated by the amount of ATA2 and redistribution to the plasma membrane. We hypothesize that ATA2 activity is regulated by recruitment of ATA2 protein from an intracellular compartment. In addition, the pattern of expression of System A activity in oocytes, transport kinetics, and sensitivity to chemical modification indicate the presence of a second System A isoform in liver that differs substantially from ATA2.
Freeman
Thomas L
TL
Department of Internal Medicine, University of Nebraska Medical Center and Veterans Administration Medical Center, Alcohol Study Unit, Omaha, NE 68105, USA.
Thiele
Geoffrey M
GM
Tuma
Dean J
DJ
Machu
Tina K
TK
Mailliard
Mark E
ME
D026924:Amino Acid Transport System A / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism* / Q000493:pharmacokinetics; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002451:Cell Compartmentation / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D006498:Hepatectomy; D007424:Intracellular Fluid / Q000378:metabolism; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D009865:Oocytes / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014982:Xenopus laevis; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000378:metabolism
D026924:Amino Acid Transport System A; D000596:Amino Acids; D020033:Protein Isoforms; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D013439:Sulfhydryl Reagents; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D012964:Sodium; D005033:Ethylmaleimide