title: Photoaffinity labeling of the beta-adrenergic receptor from cultured lymphoma cells with [125I]iodoazidobenzylpindolol: loss of the label with desensitization.
abstract: The beta-adrenergic antagonist [125I]iodoazidobenzylpindolol ( [125I]IABP) specifically photolabeled two polypeptides in membrane preparations from wild-type (WT) and coupling protein-deficient cyc- cultured lymphoma cells. The molecular weights of the two polypeptides determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis were 65,000 and 55,000. They were labeled in a ratio of approximately 1:1. Pretreatment of intact WT or cyc- cells with 1.0 microM epinephrine for 15 min (desensitization) resulted in a greater loss of the 55,000 Mr polypeptide (40-60%) relative to the 65,000 Mr peptide (10-30% loss). An 18- to 24-hr pretreatment of WT cells with terbutaline (down-regulation) led to a greater than 90% reduction of the photolabeling of both polypeptides, whereas a similar pretreatment of cyc- cells resulted in no further loss of labeled receptor than that observed after only a 15-min pretreatment with epinephrine. There was no indication of a change in the electrophoretic mobility of the [125I]IABP-labeled receptors after either short- or long-term agonist pretreatment. These data provide direct evidence for heterogeneity of the beta-adrenergic receptor in lymphoma cells. The differential loss of the [125I]IABP labeling in the two polypeptides suggests a functional heterogeneity as well.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000345:Affinity Labels; D000818:Animals; D001386:Azides; D002478:Cells, Cultured; D008223:Lymphoma / Q000378:metabolism; D051379:Mice; D008970:Molecular Weight; D010869:Pindolol / Q000031:analogs & derivatives*; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000318:Adrenergic beta-Agonists; D000345:Affinity Labels; D001386:Azides; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; C029987:1-(indol-4-yloxy)-3-(1-(4-azido-3-iodophenyl)-2-isobutylamine)-2-propanol; D010869:Pindolol; D000262:Adenylyl Cyclases