Zoon K C, Zur Nedden D, Hu R, Arnheiter H
J Biol Chem. 1986 Apr 15;261(11):4993-6.
Scatchard analyses of the equilibrium binding of radiolabeled human interferon-alpha2 (huIFN-alpha2) to Madin-Darby bovine kidney cells previously exposed to subsaturating concentrations of IFN-alpha showed approximately a 50% decrease in the number of cell surface receptors and no change in the apparent dissociation constant, Kd, compared with cells not exposed to interferon. The steady state equations describing the interaction of polypeptide ligands with cell surface receptors under physiological conditions (Wiley, H.S., and Cunningham, D.D. (1981) Cell 25, 433-440) have allowed us to determine, under steady state conditions, the rate of insertion of receptors into the cell membrane, the endocytic rate constant of occupied receptors, the rate constant of turnover of unoccupied receptors, and the rate of hydrolysis of internalized ligand. Our results indicate that occupied and unoccupied interferon receptors are cleared from the cell surface at approximately the same rate. This suggests that the down-regulation of the huIFN-alpha2 receptor on Madin-Darby bovine kidney cells by huIFN-alpha2 differs from that of several other surface receptors for polypeptide hormones and growth factors analyzed on cultured cells in that the binding of huIFN-alpha2 to its receptor does not increase the rate of receptor endocytosis.
用放射性标记的人α2干扰素（huIFN-α2）与先前暴露于亚饱和浓度α干扰素的马-达二氏牛肾细胞进行平衡结合的Scatchard分析显示，与未暴露于干扰素的细胞相比，细胞表面受体数量减少了约50%，而表观解离常数Kd没有变化。描述生理条件下多肽配体与细胞表面受体相互作用的稳态方程（Wiley, H.S., and Cunningham, D.D. (1981) Cell 25, 433 - 440）使我们能够在稳态条件下确定受体插入细胞膜的速率、被占据受体的内吞速率常数、未被占据受体的周转速率常数以及内化配体的水解速率。我们的结果表明，被占据和未被占据的干扰素受体从细胞表面清除的速率大致相同。这表明，huIFN-α2对马-达二氏牛肾细胞上huIFN-α2受体的下调与在培养细胞上分析的几种其他多肽激素和生长因子的表面受体不同，因为huIFN-α2与其受体的结合不会增加受体内吞的速率。
