Kuroda M, Honnor R C, Cushman S W, Londos C, Simpson I A
J Biol Chem. 1987 Jan 5;262(1):245-53.
This paper examines the modulation of insulin-stimulated glucose transport activity in rat adipose cells by ligands for receptors (R) that mediate stimulation (Rs; lipolytic) or inhibition (Ri; antilipolytic) of adenylate cyclase. The changes in glucose transport activity and cAMP, as assessed by 3-O-methylglucose uptake and (-/+) cAMP-dependent protein kinase (A-kinase) activity ratios, respectively, were monitored under conditions that maintain steady-state A-kinase activity ratios (Honnor, R. C., Dhillon, G. S., and Londos, C. (1985) J. Biol. Chem. 260, 15122-15129). Removal of endogenous adenosine with adenosine deaminase decreased insulin-stimulated glucose transport activity by approximately 30%, which was prevented or restored with Ri agonists such as phenylisopropyladenosine, nicotinic acid, and prostaglandin E1. These changes in transport activity were not accompanied by changes in A-kinase activity ratios, indicating that Ri-mediated effects on transport are independent of cAMP changes. Addition of an Rs ligand, isoproterenol, in the presence of adenosine increased kinase activity but did not change glucose transport activity. Conversely, upon removal of adenosine, addition of Rs ligands such as isoproterenol, adrenocorticotropic hormone, or glucagon strongly inhibited transport (approximately 50%) and stimulated kinase activity. However, subsequent addition of phenylisopropyladenosine nearly restored transport activity without alteration of A-kinase activity. These data and additional kinetic experiments suggest that Rs-mediated glucose transport modulations are also independent of cAMP. The interchangeability of ligands for both Rs and Ri receptors in modulating transport activity suggests that these cAMP-independent effects are mediated by the stimulatory (Ns) and inhibitory (Ni) guanyl nucleotide-binding regulatory proteins of adenylate cyclase. All Rs-and Ri-induced changes in transport activity occurred without a change in glucose transporter distribution, as assessed by D-glucose-inhibitable cytochalasin B binding, suggesting that Rs and Ri ligands modulate the intrinsic activity of the glucose transporter present in the plasma membrane.
本文研究了介导腺苷酸环化酶刺激（Rs；脂解）或抑制（Ri；抗脂解）的受体（R）的配体对大鼠脂肪细胞中胰岛素刺激的葡萄糖转运活性的调节作用。分别通过3-O-甲基葡萄糖摄取和（-/+）cAMP依赖性蛋白激酶（A激酶）活性比值评估葡萄糖转运活性和cAMP的变化，在维持稳态A激酶活性比值的条件下进行监测（Honnor，R.C.，Dhillon，G.S.，和Londos，C.（1985）J.Biol.Chem.260，15122 - 15129）。用腺苷脱氨酶去除内源性腺苷可使胰岛素刺激的葡萄糖转运活性降低约30%，而Ri激动剂如苯异丙基腺苷、烟酸和前列腺素E1可预防或恢复这种降低。转运活性的这些变化并未伴随A激酶活性比值的改变，表明Ri介导的对转运的影响与cAMP变化无关。在存在腺苷的情况下添加Rs配体异丙肾上腺素可增加激酶活性，但不改变葡萄糖转运活性。相反，去除腺苷后，添加异丙肾上腺素、促肾上腺皮质激素或胰高血糖素等Rs配体可强烈抑制转运（约50%）并刺激激酶活性。然而，随后添加苯异丙基腺苷几乎可恢复转运活性，而不改变A激酶活性。这些数据以及额外的动力学实验表明，Rs介导的葡萄糖转运调节也与cAMP无关。Rs和Ri受体的配体在调节转运活性方面的互换性表明，这些不依赖cAMP的效应是由腺苷酸环化酶的刺激性（Ns）和抑制性（Ni）鸟苷酸结合调节蛋白介导的。通过D-葡萄糖抑制的细胞松弛素B结合评估，所有Rs和Ri诱导的转运活性变化均未伴随葡萄糖转运体分布的改变，这表明Rs和Ri配体调节存在于质膜中的葡萄糖转运体的内在活性。
