Internalization and distribution of three alpha1-adrenoceptor subtypes in HEK293A cells before and after agonist stimulation

Aim: To examine the subcellular distribution of the 3 α₁-adrenoceptor (α₁-AR) subtypes and their internalization and trafficking upon agonist stimulation in human embryonic kidney 293A cells. Methods: Confocal real-time imaging, enzyme linked immunosorbent assay (ELISA) and whole cell [³H]-prazosin binding assay were applied to detect the distribution and localization of the 3 α₁-AR subtypes. Results: α_1A-AR was found both on the cell surface and in the cytoplasm; α_1B-AR, however, was predominantly detected on the cell surface, while α_1D-AR was detected mainly in the intracellular compartments. After stimulation with phenylephrine, localization changes were detected by confocal microscopy for α_1A- and α_1B-AR, but the localization of α_1D-AR were unaffected. Phenylephrine stimulation promoted a more rapid internalization of α_1B-AR than α_1A-AR. α_1D-AR internalization was detected only by ELISA. Whole cell [³H]-prazosin binding assay showed that α_1A-AR functional receptors were detected both on the cell surface and in the cytoplasm; α_1B-AR, however, were detected predominantly on the cell surface, while α_1D-AR were detected mainly in intracellular compartments. Phenylephrine stimulation promoted internalization of α_1A- and α_1B-AR. Conclusion: Phenylephrine stimulation induced changes in the localization of the 3 α₁-AR.