Chang D Z, Wu Z, Ciardelli T L
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755-3835, USA.
J Biol Chem. 1996 Jun 7;271(23):13349-55. doi: 10.1074/jbc.271.23.13349.
In previous studies, we have identified an interleukin-2 (IL-2) analog containing a point mutation at position 51 (T51P) that expresses nearly wild-type bioactivity, yet has approximately 10-fold lower receptor binding affinity. Since ligand-dependent receptor internalization may be the rate-limiting step controlling the duration of IL-2 receptor signaling, a reduction in the receptor internalization rate could contribute to the observed response enhancement for this analog. To evaluate this possibility, we compared the internalization of IL-2 and T51P in three separate assays. While the internalization rate for IL-2 agreed with values determined by others, the internalization of T51P was markedly reduced. The receptor binding rate constants for this analog were only slightly different; thus, altered binding kinetics could not explain the decreased internalization rate. The effects of reduced internalization were also observable in bioassays, where T51P maintained T-cell proliferation for a longer period compared with IL-2. These results indicate that the T51P point mutation reduces the receptor internalization rate compared with IL-2 in a fashion that is independent of the dissociation rate. This analog may represent a new approach to the preparation of cytokine analogs with potentiated agonist and antagonist properties.
在先前的研究中，我们鉴定出一种白细胞介素-2（IL-2）类似物，其在第51位存在一个点突变（T51P），该类似物表现出近乎野生型的生物活性，但受体结合亲和力约低10倍。由于配体依赖性受体内化可能是控制IL-2受体信号传导持续时间的限速步骤，受体内化速率的降低可能有助于观察到的该类似物的反应增强。为了评估这种可能性，我们在三项独立的试验中比较了IL-2和T51P的内化情况。虽然IL-2的内化速率与其他人测定的值一致，但T51P的内化明显降低。该类似物的受体结合速率常数仅有轻微差异；因此，结合动力学的改变无法解释内化速率的降低。在生物测定中也可观察到内化减少的影响，与IL-2相比，T51P能使T细胞增殖维持更长时间。这些结果表明，与IL-2相比，T51P点突变以一种与解离速率无关的方式降低了受体内化速率。该类似物可能代表了一种制备具有增强激动剂和拮抗剂特性的细胞因子类似物的新方法。
