LaVallie Edward R, Chockalingam Priya S, Collins-Racie Lisa A, Freeman Bethany A, Keohan Cristin C, Leitges Michael, Dorner Andrew J, Morris Elisabeth A, Majumdar Manas K, Arai Maya
Departments of Biological Technologies and Women's Health and Musculoskeletal Biology, Wyeth Research, Cambridge, Massachusetts 02140-2325, USA.
J Biol Chem. 2006 Aug 25;281(34):24124-37. doi: 10.1074/jbc.M601905200. Epub 2006 Jun 23.
Protein kinase Czeta (PKCzeta) is an intracellular serine/threonine protein kinase that has been implicated in the signaling pathways for certain inflammatory cytokines, including interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-alpha), in some cell types. A study of gene expression in articular chondrocytes from osteoarthritis (OA) patients revealed that PKCzeta is transcriptionally up-regulated in human OA articular cartilage clinical samples. This finding led to the hypothesis that PKCzeta may be an important signaling component of cytokine-mediated cartilage matrix destruction in articular chondrocytes, believed to be an underlying factor in the pathophysiology of OA. IL-1 treatment of chondrocytes in culture resulted in rapidly increased phosphorylation of PKCzeta, implicating PKCzeta activation in the signaling pathway. Chondrocyte cell-based assays were used to evaluate the contribution of PKCzeta activity in NF-kappaB activation and extracellular matrix degradation mediated by IL-1, TNF, or sphingomyelinase. In primary chondrocytes, IL-1 and TNF-alpha caused an increase in NF-kappaB activity resulting in induction of aggrecanase-1 and aggrecanase-2 expression, with consequent increased proteoglycan degradation. This effect was blocked by the pan-specific PKC inhibitors RO 31-8220 and bisindolylmaleimide I, partially blocked by Gö 6976, and was unaffected by the PKCzeta-sparing inhibitor calphostin C. A cell-permeable PKCzeta pseudosubstrate peptide inhibitor was capable of blocking TNFand IL-1-mediated NF-kappaB activation and proteoglycan degradation in chondrocyte pellet cultures. In addition, overexpression of a dominant negative PKCzeta protein effectively prevented cytokine-mediated NF-kappaB activation in primary chondrocytes. These data implicate PKCzeta as a necessary component of the IL-1 and TNF signaling pathways in chondrocytes that result in catabolic destruction of extracellular matrix proteins in osteoarthritic cartilage.
蛋白激酶Cζ（PKCζ）是一种细胞内丝氨酸/苏氨酸蛋白激酶，在某些细胞类型中，它参与了包括白细胞介素-1（IL-1）和肿瘤坏死因子α（TNF-α）在内的某些炎性细胞因子的信号通路。一项对骨关节炎（OA）患者关节软骨细胞基因表达的研究表明，PKCζ在人类OA关节软骨临床样本中的转录上调。这一发现引发了一个假设，即PKCζ可能是细胞因子介导的关节软骨细胞中软骨基质破坏的重要信号成分，而这被认为是OA病理生理学的一个潜在因素。在培养中用IL-1处理软骨细胞导致PKCζ的磷酸化迅速增加，这表明PKCζ在信号通路中被激活。基于软骨细胞的试验用于评估PKCζ活性在由IL-1、TNF或鞘磷脂酶介导的核因子κB（NF-κB）激活和细胞外基质降解中的作用。在原代软骨细胞中，IL-1和TNF-α导致NF-κB活性增加，从而诱导聚集蛋白聚糖酶-1和聚集蛋白聚糖酶-2的表达，进而导致蛋白聚糖降解增加。这种效应被泛特异性PKC抑制剂RO 31-8220和双吲哚马来酰胺I阻断，被Gö 6976部分阻断，并且不受PKCζ选择性抑制剂钙泊三醇C的影响。一种细胞可渗透的PKCζ假底物肽抑制剂能够阻断TNF和IL-1介导的软骨细胞团块培养中的NF-κB激活和蛋白聚糖降解。此外，显性负性PKCζ蛋白的过表达有效地阻止了原代软骨细胞中细胞因子介导的NF-κB激活。这些数据表明PKCζ是软骨细胞中IL-1和TNF信号通路的必要组成部分，该信号通路导致骨关节炎软骨中细胞外基质蛋白的分解代谢破坏。
