Coupling of catecholamine receptor from one cell with adenylate cyclase from another cell by cell fusion

Abstract

The experiments test the hypothesis that beta-adrenergic receptor is an independent unit that can be transferred from one adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4-6-1-1[ system to another. Turkey erythrocytes in which the catalytic activity of adenylate cyclase had been inactivated by N-ethylmaleimide or by heat contributed the beta-adrenergic receptor. Friend erythroleukemia cells (F cells) that possessed no measurable beta-adrenergic receptor contributed the adenylate cyclase. The erythrocytes in which the enzyme had been inactivated were fused with the F cells by Sendai virus. The cell ghosts of the fused preparation demonstrated adenylate cyclase activity which was strikingly enhanced by isoproterenol. Controls of fusion of F cells with each other or with human erythrocytes failed to show a response to isoproterenol. It was therefore concluded that the beta-adrenergic receptor of the turkey erythrocytes must have become functionally coupled to the adenylate cyclase of the mouse F cells. Activation by isoproterenol was demonstrable within a few minutes after fusion, and inhibitors of protein synthesis had no effect. Thus, coupling must have occurred between the preexisting components. The findings suggest that it may be possible in the future to confer on cells that possess an adenylate cyclase system new hormonal responses by inserting a receptor into their cell membrane. It is proposed that the procedure of massive heterologous cell fusion, as used in the present study, can be used to analyze the function of other cell membrane components.