Membrane transport of neuronal nitric oxide synthase substrate L-arginine is constitutively expressed with CAT1 and 4F2hc, but not CAT2 or rBAT.
The potential induction of cationic and zwitterionic amino acid transport systems and mRNA transcripts was investigated in primary neuronal cultures from rat hypothalamus/brainstem. Cultures exposed to bacterial lipopolysaccharide (LPS) plus interferon-gamma (IFNgamma) were assessed with respect to northern blot analyses, L-leucine/L-arginine cross-inhibition uptake profiles in the presence and absence of Na+, and initial rate sodium-independent L-arginine transport kinetics. L-Arginine uptake activity was constitutively expressed along with uninduced steady-state levels of CAT1 and 4F2hc transcripts. However, neither the high-affinity nor the low-affinity alternatively spliced inducible isoforms of CAT2 or CAT2a transcripts (encoding system y+ in control astrocytes, lymphocytes, or liver) nor the rBAT transcripts (encoding system b(o,+) in control intestinal epithelial cells) were detected by northern analysis of neuronal mRNA. Cross-inhibition profiles were consistent with physiologic system y+ activity, but not system b(o,+) or system y+ L. Transport kinetics gave a single component with Vmax = 113 +/- 7 pmol/min/mg of protein and Km = 47 +/- 8 microM L-arginine; these kinetic parameters were not influenced by addition of LPS/IFNgamma at concentrations that up-regulated CAT2 mRNA and system y+ activity in control astroglia from the same area of the brain. The data are consistent with L-arginine membrane uptake occurring via only system y+ encoded by constitutive CAT1, with possible physiologic contribution by constitutive 4F2hc transcripts in primary neuronal cultures.
Department of Physiology, University of Florida College of Medicine, Gainesville 32610-0274, USA.
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Stevens
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D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D015703:Antigens, CD / Q000235:genetics* / Q000378:metabolism; D000954:Antigens, Surface / Q000235:genetics / Q000378:metabolism; D001120:Arginine / Q000378:metabolism* / Q000493:pharmacokinetics; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002374:Catalase / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D027261:Fusion Regulatory Protein-1; D015971:Gene Expression Regulation, Enzymologic; D007930:Leucine / Q000493:pharmacokinetics; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D011506:Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D012249:Rhombencephalon / Q000166:cytology; D050916:TRPV Cation Channels; D014316:Tritium
D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids; D015703:Antigens, CD; D000954:Antigens, Surface; D002352:Carrier Proteins; D027261:Fusion Regulatory Protein-1; D008562:Membrane Glycoproteins; D011506:Proteins; C490274:Slc7a2 protein, rat; D050916:TRPV Cation Channels; C120776:TRPV6 channel; D014316:Tritium; D001120:Arginine; D002374:Catalase; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D007930:Leucine