title: Relationship between an altered membrane form and a low affinity form of the beta-adrenergic receptor occurring during catecholamine-induced desensitization. Evidence for receptor internalization.
abstract: We have investigated the relationship between the catecholamine-induced occurrence in 1321N1 human astrocytoma cells of beta-adrenergic receptors that exhibit low apparent affinity for hydrophilic ligands in short-time assays with intact cells and a population of beta-adrenergic receptors that migrate in a light vesicle fraction on sucrose density gradients. Pretreatment of cells with concanavalin A prevents the generation of both of these forms of the receptor during incubation with agonists but does not prevent the agonist-induced decrease in isoproterenol-stimulated cyclic AMP production that also occurs during desensitization. Selective labeling of the low affinity beta-receptors with 125I-pindolol followed by centrifugation on sucrose density gradients revealed that all of the receptors in the light vesicle fraction from desensitized cells were of the low affinity type, but that a portion of the low affinity receptors also migrated in a heavier sucrose fraction together with the plasma membrane. In contrast, in control cells, no low affinity receptors were present in the heavy sucrose fractions. The agonist-induced occurrence of these various forms of the beta-adrenergic receptor can be explained on the basis of current models of desensitization involving agonist-induced internalization of beta-adrenergic receptors.
mesh_terms: D001254:Astrocytoma / Q000378:metabolism; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D003208:Concanavalin A / Q000494:pharmacology; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D008766:Methylmannosides / Q000494:pharmacology; D010869:Pindolol / Q000378:metabolism; D011412:Propanolamines / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013997:Time Factors
chemical_list: D008766:Methylmannosides; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D003208:Concanavalin A; C008466:methylmannoside; D010869:Pindolol; D007545:Isoproterenol; C033394:CGP 12177