Functional changes in the properties of beta-adrenoreceptors of pigeon erythrocytes after treatment with a catalytic subunit of cAMP-dependent protein kinase
Popov, K.M.; Bulargina, T.V.; Severin, E.S.
Biokhimiia 50(9): 1535-1538
1985
ISSN/ISBN: 0320-9725 PMID: 2996638 Document Number: 249250
beta-Adrenoreceptors were solubilized by deoxycholate from pigeon erythrocyte plasma membranes treated with N-ethylmaleimide. Removal of the detergent resulted in the incorporation of receptors into phospholipid vesicles as well as in the reconstitution of their biological activity. After fusion of vesicles containing reconstituted receptors to vesicles containing the Ns protein and a catalytic component, the hormonal activation of the enzyme was restored. When prior to fusion the beta-adrenoreceptor-containing vesicles were preincubated with the catalytic subunit of cAMP dependent protein kinase, the hormone-induced activation of the enzyme diminished by 45-50%. The decrease of activation is due to the increase in the lag phase of the enzyme activation in the presence of isoproterenol and Gpp(NH)p as well as to the loss of activity in the steady-state phase of activation. Phosphorylation of beta-adrenoreceptors decreased the concentration of the ternary isoproterenol-receptor-Ns protein complex involved in the activation of adenylate cyclase. Thus, the phosphorylation of receptors is responsible for the disturbances in the mechanism of hormonal signal transmission that are similar to those observed in adenylate cyclase desensitization.