Islet‐activating protein discriminates between different inhibitors of thyroidal cyclic AMP system

FEBS Letters

Van Sande, J.¹  Cochaux, P.¹  Dumont, J.E.¹ 

[1] Institut de Recherche Interdisciplinaire en Biologie Humaine et Nucleaire (IRIBHN), School of Medicine, Free University of Brussels (U.L.B.), Campus Erasme, Route de Lennik 808, 1070 Brussels, Belgium

关键词: IAP;    Thyroid;    Cyclic AMP;    Norepinephrine;    Iodide;    Ni;    inhibitory nucleotide binding regulatory component of adenylate cyclase;    TSH;    thyroid-stimulating hormone;    IAP;    islet-activating protein;   

DOI  :  10.1016/0014-5793(85)80539-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

TSH-induced cyclic AMP accumulation in dog thyroid slices is inhibited by norepinephrine through an α₂-adrenergic receptor, by carbamylcholine through a muscarinic cholinergic receptor, and by iodide. The inhibitory effect of iodide bears on the adenylate cyclase, but the exact mechanism of its action is still unknown. It is known that norepinephrine acts through activation of the N₁ subunit of the cyclase, and that carbamylcholine, activating a phosphodiesterase, acts independently of N_i IAP (islet-activating protein) has been shown to inactivate the N_i subunit. We studied the effect of IAP on the inhibitory action of iodide, norepinephrine, and carbamylcholine on cyclic AMP accumulation in TSH-stimulated thyroid slices. Incubations of 15 or 22 h, and relatively high concentrations of IAP (250 ) were necessary to demonstrate an effect of IAP on thyroid slices. We report here that, under those conditions, inhibition of cyclic AMP accumulation by norepinephrine, but not by carbamylcholine or iodide, was suppressed by IAP treatment. These results indicate that the cyclase inhibition by iodide, is either not mediated by N_i or if mediated by N_i involves a mode of regulation of this coupling protein that is different from that by which the other 'N_i-mediated' inhibitory hormones act on the enzyme.

【 授权许可】

Unknown