Ren Fucheng, Zhan Xin, Martens Gregory, Lee Jinhee, Center David, Hanson Sue Kim, Kornfeld Hardy
Division of Pulmonary and Critical Care Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA.
J Immunol. 2005 Mar 1;174(5):2738-45. doi: 10.4049/jimmunol.174.5.2738.
Prior DNA microarray studies suggested that IL-16 mRNA levels decrease following T cell activation, a property unique among cytokines. We examined pro-IL-16 mRNA and protein expression in resting and anti-CD3 mAb-activated primary murine CD4(+) T cells. Consistent with the microarray reports, pro-IL-16 mRNA levels fell within 4 h of activation, and this response is inhibited by cyclosporin A. Total cellular pro-IL-16 protein also fell, reaching a nadir at 48 h. Pro-IL-16 comprises a C-terminal cytokine domain and an N-terminal prodomain that are cleaved by caspase-3. Pro-IL-16 expressed in transfected tumor cells was previously shown to translocate to the nucleus and to promote G(0)/G(1) arrest by stabilizing the cyclin-dependent kinase inhibitor p27(Kip1). In the present study, we observed increased S-phase kinase-associated protein 2 mRNA expression in IL-16 null mice, but basal expression and activation-dependent regulation of p27(Kip1) were no different from wild-type mice. Stimulation with anti-CD3 mAb induced transiently greater thymidine incorporation in IL-16-deficient CD4(+) T cells than wild-type controls, but there was no difference in cell survival or in the CFSE dilution profiles. Analysis of CD4(+) T cell proliferation in vivo using BrdU labeling similarly failed to identify a hyperproliferative phenotype in T cells lacking IL-16. These data demonstrate that pro-IL-16 mRNA and protein expression are dynamically regulated during CD4(+) T cell activation by a calcineurin-dependent mechanism, and that pro-IL-16 might influence T cell cycle regulation, although not in a dominant manner.
先前的DNA微阵列研究表明，白细胞介素-16（IL-16）mRNA水平在T细胞活化后会下降，这是细胞因子中独一无二的特性。我们检测了静息状态和抗CD3单克隆抗体激活的原代小鼠CD4(+) T细胞中前体IL-16 mRNA和蛋白的表达。与微阵列报告一致，前体IL-16 mRNA水平在活化后4小时内下降，且这种反应受到环孢素A的抑制。总的细胞前体IL-16蛋白也下降，在48小时时达到最低点。前体IL-16由一个C末端细胞因子结构域和一个N末端前结构域组成，它们被半胱天冬酶-3切割。先前已证明，在转染的肿瘤细胞中表达的前体IL-16会转运至细胞核，并通过稳定细胞周期蛋白依赖性激酶抑制剂p27(Kip1)来促进G(0)/G(1)期阻滞。在本研究中，我们观察到IL-16基因敲除小鼠中S期激酶相关蛋白2 mRNA表达增加，但p27(Kip1)的基础表达和活化依赖性调节与野生型小鼠并无差异。用抗CD3单克隆抗体刺激后，IL-16缺陷型CD4(+) T细胞中胸苷掺入量瞬时高于野生型对照，但细胞存活率和羧基荧光素二乙酸琥珀酰亚胺酯（CFSE）稀释曲线并无差异。使用5-溴脱氧尿苷（BrdU）标记对体内CD4(+) T细胞增殖进行分析，同样未能在缺乏IL-16的T细胞中鉴定出增殖亢进表型。这些数据表明，前体IL-16 mRNA和蛋白表达在CD4(+) T细胞活化过程中通过钙调神经磷酸酶依赖性机制受到动态调节，并且前体IL-16可能影响T细胞周期调节，尽管并非以主导方式。
