Colette Delavier-Klutchko

Structural basis for functional diversity of β1-, β2- and β3-adrenergic receptors

We evaluate the structural characteristics of β 1 -, β 2 - and β 3 -AR genes and proteins that may be the basis of the different activities of the three receptors which otherwise appear to respond to the same hormones and trigger the same second messenger pathway. We discuss the involvement of the β 3 -AR in mediating various atypical effects of catecholamines in adipocytes and other tissues

The human carcinoma cell line A431 possesses large numbers of functional β-adrenergic receptors

The existence of β‐adrenergic receptors was demonstrated on whole A431 cells as well as A431 membrane preparations by means of binding assays using the hydrophobic 1‐[3H]dihydroalprenolol and the hydrophilic antagonist [3H]CGP‐12,177 as β‐adrenergic ligands. Binding was stereospecific. The receptors, as shown by competition studies, proved to be of the β2‐subtype and appeared functional in the stimulation of adenylate cyclase. The number of receptors per cell and the yield of receptor sites/mg membrane protein render the A431 cell a useful tool for the study of human β‐adrenergic receptors.

Antibodies raised against β-adrenergic receptors stimulate adenylate cyclase

Abstract Antibodies raised in mice against β-adrenergic receptors purified from turkey erythrocyte membranes, specifically bind to cells which possess a β-adrenergic receptor and immunoprecipitate radiolabelled purified receptor. These antibodies stimulate the adenylate cyclase activity of the turkey erythrocytes, although they do not compete with the catecholamine hormones for binding to the β-adrenergic receptor. Thus the receptor-antibody interaction, although occuring at another site than the receptor-hormone interaction, may still trigger the enzymatic activity.

Towards the chemical and functional characterization of the β-adrenergic receptor

The biochemical characterization of the catecholamine β-adrenergic receptor from turkey erythrocyte membranes is rapidly progressing. The complex relationship with the adenylate cyclase and other membrane components which intervene in the hormonal stimulation of the cell is discussed in view of the effect of various ligands on the membrane-bound and affinity-purified receptor.

Altered binding properties of β-adrenergic receptors and lack of coupling to adenylate cyclase in P815 mastocytoma cells

P815, a murine mastocytoma cell line, possesses beta-adrenergic binding sites as assessed by using [3H]dihydroalprenolol (antagonist) and [3H]hydroxybenzylisoproterenol (agonist). The number of binding sites per cell was 29 000 for the agonist and 75 000 for the antagonist, as determined by direct binding assays and inhibition experiments on intact cells. On membrane preparations from the same cells, binding of alprenolol was only displaceable by antagonists, while stereospecific binding of hydroxybenzylisoproterenol was only displaceable by agonists. The P815 membranes also possessed an adenylate cyclase stimulated by Gpp(NH)p and NaF but not by 1-isoproterenol. The intracellular cAMP level of intact cells was not modulated by 1-isoproterenol or by 1-epinephrine, but was increased by forskolin. These results suggest that the beta-adrenergic receptor of P815 mastocytoma cells is non-functional. This may explain the failure of agonists to stimulate adenylate cyclase activity in these cells.

Assimilation of Ammonia During Sporogenesis of Saccharomyces cerevisiae: Effect of Ammonia and Glutamine

Summary: Comparison of the pools of glutamic acid and glutamine and of the specific activities of glutamine synthetase and glutamate dehydrogenases in sporulating a/α and non-sporulating α/α cells of Saccharomyces cerevisiae revealed a difference in their nitrogen metabolism. Glutamine synthetase and glutamine appeared to be necessary for the sporulation process, glutamine playing, at least, a catabolic role. However, exogenous glutamine as well as ammonia inhibited sporulation while glutamic acid did not. Glutamine seemed to act through its amino group. Both inhibitors had at least two sites of action, one effective early in sporulation and related to DNA synthesis and the other acting later and not related to it.

Effect of ammonia and glutamine on macromolecule synthesis and breakdown during sporulation of saccharomyces cerevisiae

Abstract The effect of two known inhibitors of sporulation in yeast, ammonia and glutamine, on certain biochemical events during sporogenesis have been studied using sporulating a α and non sporulating α α cells. Both strains gave similar results on the increase in dry cell weight, protein and RNA breakdown and the suppression of the intensive RNA and protein syntheses occurring after 4 hours. The inhibitory effect of ammonia and glutamine on RNA and protein syntheses is reversible under the same conditions which do so for sporulation.

Solubilization of a catecholamine-sensitive guanosine triphosphatase from turkey erythrocyte membranes

~ate~hol~~e hormone st~~iation of the turkey erythrocyte adenylate cyclase involves a /3-adrenergic receptor, probably associated with a guanyl nucleotide binding protein, a catecholamine-sensitive guanosine t~phosphat~~ (GTFase) and an adenylate cycfase catalytic unit [ 1,2 J_ The ~de~t~~g of the intricate regulatory mechanisms which modulate the activities of these 4 different components, requires an analytical appraach involving the sequential solubilization and purification of each functional unit. We have described [3,4] the solub~~zation and physical separation of the turkey erythrocyte padrenergic receptor from the adenylate cyclase catalytic component. A 20 OOO-fold purification of a pharmacoIog& cal active receptor was achieved by affinity chromatography 1% We now report the solub~zation of the catecholamine sensitive GTPase from the same membrane preparations.