Ossendorp Ferry, Fu Nathalie, Camps Marcel, Granucci Francesca, Gobin Sam J P, van den Elsen Peter J, Schuurhuis Danita, Adema Gosse J, Lipford Grayson B, Chiba Tomoki, Sijts Alice, Kloetzel Peter-M, Ricciardi-Castagnoli Paola, Melief Cornelis J M
Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, The Netherlands.
J Immunol. 2005 Jun 15;174(12):7815-22. doi: 10.4049/jimmunol.174.12.7815.
Activation of dendritic cells (DC) by Th-dependent (CD40) or -independent (LPS, CpG, or immune complexes) agonistic stimuli strongly enhances the expression of the proteasome activator PA28alphabeta complex. Upon activation of DC, increased MHC class I presentation occurred of the melanocyte-associated epitope tyrosinase-related protein 2(180-188) in a PA28alphabeta-dependent manner. In contrast to other cell types, regulation of PA28alphabeta expression in DC after maturation was found to be IFN-gamma independent. In the present study, we show that expression of PA28alpha and beta subunits was differentially regulated. Firstly, PA28alpha expression is high in both immature and mature DC. In contrast, PA28beta expression is low in immature DC and strongly increased in mature DC. Secondly, we show the presence of a functional NF-kappaB site in the PA28beta promoter, which is absent in the PA28alpha promoter, indicating regulation of PA28beta expression by transcription factors of the NF-kappaB family. In addition, glycerol gradient analysis of DC lysates revealed elevated PA28alphabeta complex formation upon maturation. Thus, induction of PA28beta expression allows proper PA28alphabeta complex formation, thereby enhancing proteasome activity in activated DC. Therefore, maturation of DC not only improves costimulation but also MHC class I processing. This mechanism enhances the CD8(+) CTL (cross)-priming capacity of mature DC.
由Th依赖型（CD40）或非依赖型（脂多糖、CpG或免疫复合物）激动剂刺激激活的树突状细胞（DC），会强烈增强蛋白酶体激活剂PA28αβ复合物的表达。DC激活后，黑素细胞相关表位酪氨酸酶相关蛋白2（180 - 188）的MHC I类呈递以PA28αβ依赖的方式增加。与其他细胞类型不同，成熟后DC中PA28αβ表达的调节不依赖于γ干扰素。在本研究中，我们发现PA28α和β亚基的表达受到不同调节。首先，PA28α在未成熟和成熟DC中表达均较高。相比之下，PA28β在未成熟DC中表达较低，而在成熟DC中强烈增加。其次，我们发现在PA28β启动子中存在一个功能性NF-κB位点，而PA28α启动子中不存在，这表明PA28β的表达受NF-κB家族转录因子的调节。此外，对DC裂解物进行甘油梯度分析显示，成熟后PA28αβ复合物的形成增加。因此，PA28β表达的诱导可促进PA28αβ复合物的正确形成，从而增强激活的DC中的蛋白酶体活性。所以，DC的成熟不仅改善共刺激，还改善MHC I类加工。这种机制增强了成熟DC的CD8(+) CTL（交叉）启动能力。
