title: Down-regulation and recycling of the nitrobenzylthioinosine-sensitive nucleoside transporter in cultured chromaffin cells.
abstract: The dynamics of the nitrobenzylthioinosine (NBTI)-sensitive nucleoside transporter were studied in cultured chromaffin cells. Photolabelling of transporters with [3H]NBTI induced a down-regulation of this protein from the plasma membrane with a half-life value of 2.31 +/- 0.61 h, measured by specific isolation of plasma membrane on polycationic beads. In this internalization step 50-60% of transporters were destroyed. The remaining labelled protein reappeared in plasma membranes and underwent a new disappearance cycle with a longer half-life period (34.65 +/- 3.9 h). A similar pattern of internalization and reappearance of nucleoside transporters was observed in cells cross-linked with non-labelled NBTI, with a half value of reappearance of 33 h. Chromaffin cells cultured in the presence of the protein synthesis inhibitor, cycloheximide, had a component of disappearance for NBTI binding sites with a half-life value of 24.6 +/- 1.4 h.
authors.affiliation: Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Torres
authors.forename: E G
authors.initials: EG
authors.lastname: Delicado
authors.forename: M D
authors.initials: MD
authors.lastname: Fideu
authors.forename: M T
authors.initials: MT
authors.lastname: Miras-Portugal
mesh_terms: D000345:Affinity Labels / Q000494:pharmacology*; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002838:Chromaffin System / Q000166:cytology / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D006207:Half-Life; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D009474:Neurons / Q000378:metabolism*; D033703:Nucleoside Transport Proteins; D013868:Thioinosine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000345:Affinity Labels; D002352:Carrier Proteins; D008565:Membrane Proteins; D033703:Nucleoside Transport Proteins; D013868:Thioinosine; D003513:Cycloheximide; C001789:4-nitrobenzylthioinosine