McKee R L, Goldman M E, Caulfield M P, DeHaven P A, Levy J J, Nutt R F, Rosenblatt M
Parathyroid Hormone Laboratory, Merck Sharp & Dohme Research Laboratories, West Point, PA 19486.
Endocrinology. 1988 Jun;122(6):3008-10. doi: 10.1210/endo-122-6-3008.
The N-terminal fragment of human hypercalcemia factor (hHCF), hHCF-(1-34)NH2, has bioactivities similar to PTH in vitro and in vivo. Because it interacts with PTH receptors and is more potent than PTH in some systems, the hHCF sequence may provide interesting leads for the design of potent and selective PTH and hHCF antagonists. Based on the antagonist activity of [Tyr34]bovine PTH-(7-34)NH2 [( Tyr34]bPTH-(7-34)NH2), we synthesized the corresponding fragment of hHCF, hHCF-(7-34)NH2 and examined its properties in vitro. In the bone-derived rat osteosarcoma cell line ROS 17/2.8, hHCF-(7-34)NH2 and [Tyr34]bPTH-(7-34)NH2 were equipotent for inhibition of radiolabeled PTH-binding. In contrast, hHCF-(7-34)NH2 was 8-fold more potent that [Tyr34]bPTH-(7-34)NH2 for inhibiting PTH-stimulated cAMP production. hHCF-(7-34)NH2 also inhibited PTH-binding and PTH-stimulated adenylate cyclase activity in bovine renal cortical membranes: hHCF-(7-34)NH2 and [Tyr34]bPTH-(7-34)NH2 were equipotent in this system. In addition, hHCF-(7-34)NH2 antagonized hHCF-(1-34)NH2 action in both systems with similar inhibition constants. However, unlike the PTH analogue, hHCF-(7-34)NH2 (8 microM) was a weak partial agonist, producing a 2.4-fold increase in cAMP (5% of the maximal response) in ROS cells. This same system also detects agonism for [Nle8, 18Tyr34]bPTH-(3-34)NH2, another PTH partial agonist/antagonist. These results demonstrate that hHCF-(7-34)NH2 interacts with PTH receptors based in large part on the region which is not homologous to PTH, and suggest the utility of the ROS 17/2.8 cell system for identifying weak agonism of PTH and hHCF analogues in vitro.
人高钙血症因子（hHCF）的N端片段hHCF-(1-34)NH2在体外和体内均具有与甲状旁腺激素（PTH）相似的生物活性。由于它能与PTH受体相互作用，且在某些系统中比PTH更具活性，hHCF序列可能为设计强效且选择性的PTH和hHCF拮抗剂提供有趣的线索。基于[Tyr34]牛PTH-(7-34)NH2（[Tyr34]bPTH-(7-34)NH2）的拮抗活性，我们合成了hHCF的相应片段hHCF-(7-34)NH2，并在体外检测了其性质。在源自骨的大鼠骨肉瘤细胞系ROS 17/2.8中，hHCF-(7-34)NH2和[Tyr34]bPTH-(7-34)NH2在抑制放射性标记的PTH结合方面效力相当。相比之下，在抑制PTH刺激的cAMP产生方面，hHCF-(7-34)NH2的效力比[Tyr34]bPTH-(7-34)NH2高8倍。hHCF-(7-34)NH2还抑制了牛肾皮质膜中的PTH结合和PTH刺激的腺苷酸环化酶活性：在该系统中hHCF-(7-34)NH2和[Tyr34]bPTH-(7-34)NH2效力相当。此外，hHCF-(7-34)NH2在两个系统中均拮抗hHCF-(1-34)NH2的作用，且抑制常数相似。然而，与PTH类似物不同，hHCF-(7-34)NH2（8 microM）是一种弱部分激动剂，在ROS细胞中使cAMP增加2.4倍（最大反应的5%）。同一系统也能检测到另一种PTH部分激动剂/拮抗剂[Nle8, 18Tyr34]bPTH-(3-34)NH2的激动作用。这些结果表明，hHCF-(7-34)NH2与PTH受体的相互作用在很大程度上基于与PTH不同源的区域，并提示了ROS 17/2.8细胞系统在体外鉴定PTH和hHCF类似物弱激动作用方面的实用性。
