Indirect immunufluorescence localization of β-adrenergic receptors and G-proteins in human A431 cells

Polyclonal antibodies directed against (i) rodent lung β₂-adrenergic receptor, (ii) a synthetic fragment of an extracellular domain of the receptor, and (iii) human placenta G-protein β-subunits, were used to localize these antigens in situ in intact and permeabilized human epidermoid carcinoma A431 cells. Antibodies directed against β₂-adrenergic receptors showed a punctate immunofluorescence staining throughout the cell surface of fixed intact cells. Punctate staining was also observed in clones of Chinese hamster ovary cells transfected with an expression vector harbouring the gene for the hamster β₂-adrenergic receptor. The immunofluorescence observed with anti-receptor antibodies paralleled the level of receptor expression. In contrast, the β-subunits common to G-proteins were not stained in fixed intact cells, presumably reflecting their intracellular localization. In detergent-permeabilized fixed cells, strong punctate staining of G(β)-subunits was observed throughout the cytoplasm. This is the first indirect immunofluorescence localization of β-adrenergic receptor and G-proteins. Punctate immunofluorescence staining suggests that both antigens are distributed in clusters.