title: Protein kinase Czeta is up-regulated in osteoarthritic cartilage and is required for activation of NF-kappaB by tumor necrosis factor and interleukin-1 in articular chondrocytes.
abstract: 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.
authors.affiliation: Departments of Biological Technologies and Women's Health and Musculoskeletal Biology, Wyeth Research, Cambridge, Massachusetts 02140-2325, USA. elavallie@wyeth.com
authors.forename: Edward R
authors.initials: ER
authors.lastname: LaVallie
authors.forename: Priya S
authors.initials: PS
authors.lastname: Chockalingam
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Collins-Racie
authors.forename: Bethany A
authors.initials: BA
authors.lastname: Freeman
authors.forename: Cristin C
authors.initials: CC
authors.lastname: Keohan
authors.forename: Michael
authors.initials: M
authors.lastname: Leitges
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Dorner
authors.forename: Elisabeth A
authors.initials: EA
authors.lastname: Morris
authors.forename: Manas K
authors.initials: MK
authors.lastname: Majumdar
authors.forename: Maya
authors.initials: M
authors.lastname: Arai
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D000071121:ADAMTS4 Protein; D000071116:ADAMTS5 Protein; D000818:Animals; D002356:Cartilage / Q000378:metabolism / Q000473:pathology; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism*; D004790:Enzyme Induction / Q000187:drug effects; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D010003:Osteoarthritis / Q000378:metabolism* / Q000473:pathology; D011348:Procollagen N-Endopeptidase / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D000099221:Protein Kinase C zeta
chemical_list: D051722:ADAM Proteins; D000071121:ADAMTS4 Protein; D000071116:ADAMTS5 Protein; D007375:Interleukin-1; D016328:NF-kappa B; D011348:Procollagen N-Endopeptidase; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D014409:Tumor Necrosis Factor-alpha; D000099221:Protein Kinase C zeta; C121532:ADAMTS5 protein, human