The overall objective is to elucidate the molecular mechanism of action of hormone receptors coupled to adenylate cyclase.
Specific aims are: I. To identify the special lipid (non- phospholipid) apparently required for function of the beta- adrenergic receptor (R) in native turkey erythrocyte membranes. To investigate also whether such a lipid is required in other receptor-coupled adenylate cyclase systems. II. To study the specificity of compounds capable of functioning as the special lipid in the relipidated, reconstituted R-G system (G-stimulatory guanyl nucleotide binding protein). III. To determine the lipid requirements for the various partial reactions in the relipidated reconstituted R-G system. IV. To determine the potency of 4 stereoisomers of a new, high affinity congener of isoproterenol. To use the most potent isomer, (3H) labeled, for studies of agonist binding to R. V. To use the relipidated R-G system in order to determine whether specific lipids contribute to the high affinity of new isoproterenol congener. VI. To assess the effect of phosphorylation by added protein kinases on function of the relipidated R-G system in relation to specific lipids used. The work is health related in establishing the role of specific lipids in the function of the important epinephrine receptor and in analyzing the action of a new high potency agonist. Methodology: I. Turkey erythrocyte membranes will be treated with defatted BSA to remove the special lipid. The lipid will be extracted from the BSA and readded to the membranes to test for recoupling of R to the adenylate cyclase. HPLC will serve to purify the lipid for identification. II. Gangliosides, prostaglandins, glycerides phorbol esters, etc. will be tested in the R-G system relipidated with phospholipids. Function will be measured as isoproterenol dependent formation of G/GTPgammaS. III. Various lipids will be added to the delipidated R-G system to test for locking of (3H) isoproterenol in R by N- ethylmaleimide, for its prevention by GTP and for activation of the hormone dependent GTPase reaction. IV-VI, self-explanatory.
| Ben-Arie, N; Gileadi, C; Schramm, M (1988) Interaction of the beta-adrenergic receptor with Gs following delipidation. Specific lipid requirements for Gs activation and GTPase function. Eur J Biochem 176:649-54 |
