Separate and shared lysosomal transport of branched and aromatic dipolar amino acids.
Transport systems analogous to the T and L carriers for aromatic and bulky dipolar amino acids in plasma membranes have been characterized in the membranes of intact lysosomes isolated from human fetal skin fibroblasts. While system L appears ubiquitous in plasma membranes, system T has previously been discriminated only in the plasmalemma of human red blood cells and freshly isolated rat hepatocytes. Our findings with the lysosomal systems, provisionally designated t and l, reveal both shared and dissimilar properties with the plasma membrane systems. These properties include a lack of dependency on extralysosomal Na+, differential sensitivities to the classical system L analog, 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (BCH), and the system T analog, D-tryptophan, as well as susceptibility to thiol modification at the membrane by reactivity with N-ethylmaleimide. A transport system in lysosomes from the FRTL-5 rat thyroid cell line has been described by Bernar et al. ((1986) J. Biol. Chem. 261, 17107-17112) resembles a composite of both carrier systems reported in this work.
Stewart
B H
BH
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor.
Collarini
E J
EJ
Pisoni
R L
RL
Christensen
H N
HN
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000596:Amino Acids / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D000597:Amino Acids, Branched-Chain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000598:Amino Acids, Cyclic; D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D005033:Ethylmaleimide / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008247:Lysosomes / Q000378:metabolism*; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology
D000596:Amino Acids; D000597:Amino Acids, Branched-Chain; D000598:Amino Acids, Cyclic; C006504:2-aminobicyclo(2,2,1)heptane-2-carboxylic acid; D012965:Sodium Chloride; D000255:Adenosine Triphosphate; D005033:Ethylmaleimide