Bajzer Z, Myers A C, Vuk-Pavlović S
Division of Developmental Oncology Research, Mayo Foundation, Rochester, Minnesota 55905.
J Biol Chem. 1989 Aug 15;264(23):13623-31.
We measured time-dependent concentration changes of human interferon-alpha 2a (IFN) and human tumor necrosis factor-alpha (TNF) bound at the plasma membrane and internalized by human lung alveolar carcinoma A549 cells in the presence of excess free ligand. Concentration changes for these two ligands were substantially different. We modified our compartmental kinetic model encompassing receptor synthesis and receptor loss (Myers, A. C., Kovach, J. S., and Vuk-Pavlović, S. (1987) J. Biol. Chem. 262, 6494-6499) to include receptor recycling. We solved analytically the equations of three variants of the model of receptor recycling. All parameters (rate constants) were identifiable when the data sets consisted of time-resolved concentrations of IFN and TNF at the cell surface and internalized by cells. By least squares fitting we derived the best fit values for the first order rate constants for internalization of the ligand-receptor complex, receptor recycling, turnover of free receptors, elimination of the ligand from cells, and the rate of insertion of free receptors into the membrane. The best fit to data for interactions of cells with IFN was obtained without inclusion of the term for recycling of receptors to the membrane. The simplest model including receptor recycling was necessary and sufficient for the fit to the respective data for TNF. These results demonstrate that the contribution of receptor recycling to the metabolism of the ligand and the receptor can be quantitated by compartmental modeling. Receptor recycling does not contribute to the kinetics of Type I IFN receptor in A549 cells. In contrast, recycling contributes significantly to endocytosis mediated by the TNF receptor.
我们测量了在存在过量游离配体的情况下，人α-2a干扰素（IFN）和人肿瘤坏死因子-α（TNF）结合于质膜并被人肺腺癌A549细胞内化的时间依赖性浓度变化。这两种配体的浓度变化有很大差异。我们修改了包含受体合成和受体丢失的房室动力学模型（Myers, A. C., Kovach, J. S., and Vuk-Pavlović, S. (1987) J. Biol. Chem. 262, 6494 - 6499），以纳入受体再循环。我们解析求解了受体再循环模型三个变体的方程。当数据集由细胞表面和细胞内化的IFN和TNF的时间分辨浓度组成时，所有参数（速率常数）都是可识别的。通过最小二乘法拟合，我们得出了配体-受体复合物内化、受体再循环、游离受体周转、配体从细胞中消除以及游离受体插入膜的一级速率常数的最佳拟合值。在不包含受体再循环至膜的项的情况下，获得了细胞与IFN相互作用数据的最佳拟合。对于TNF的相应数据拟合，包含受体再循环的最简单模型是必要且充分的。这些结果表明，受体再循环对配体和受体代谢的贡献可以通过房室建模进行定量。受体再循环对A549细胞中I型IFN受体的动力学没有贡献。相比之下，再循环对TNF受体介导的内吞作用有显著贡献。
