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.
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.
LaVallie
Edward R
ER
Departments of Biological Technologies and Women's Health and Musculoskeletal Biology, Wyeth Research, Cambridge, Massachusetts 02140-2325, USA. elavallie@wyeth.com
Chockalingam
Priya S
PS
Collins-Racie
Lisa A
LA
Freeman
Bethany A
BA
Keohan
Cristin C
CC
Leitges
Michael
M
Dorner
Andrew J
AJ
Morris
Elisabeth A
EA
Majumdar
Manas K
MK
Arai
Maya
M
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
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