Immunoanalogue of vertebrate beta-adrenergic receptor in the unicellular eukaryote Paramecium.
Cell fractionation, SDS-PAGE, quantitative Western blot, confocal immunolocalization and immunogold labelling were performed to find an interpretation of the physiological response of the unicellular eukaryote Paramecium to beta-adrenergic ligands. The 69 kDa polypeptide separated by SDS-PAGE in S2 and P2 Paramecium subcellular fractions cross-reacted with antibody directed against human beta2-adrenergic receptor. This was detected by Western blotting followed by chemiluminescent detection. Quantitative image analysis showed that beta-selective adrenergic agonist (-)-isoproterenol--previously shown to enhance phagocytic activity--evoked redistribution of the adrenergic receptor analogue from membraneous (P2) to cytosolic (S2) fraction. The relative increase in immunoreactive band intensity in S2 reached 80% and was paralleled by a 59% decrease in P2 fraction. Confocal immunofluorescence revealed beta2-adrenergic receptor sites on the cell surface and at the ridge of the cytopharynx--where nascent phagosomes are formed. This localization was confirmed by immunoelectron microscopy. These results indicate that the 69 kDa Paramecium polypeptide immunorelated to vertebrate beta2-adrenergic receptor appeared in this evolutionary ancient cell as a nutrient receptor.
D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002458:Cell Fractionation; D002462:Cell Membrane / Q000737:chemistry / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D008970:Molecular Weight; D010247:Paramecium / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D018343:Receptors, Adrenergic, beta-2 / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D022161:Transport Vesicles / Q000737:chemistry / Q000276:immunology; D014714:Vertebrates / Q000276:immunology / Q000378:metabolism
D018343:Receptors, Adrenergic, beta-2; D007545:Isoproterenol