Activation of Integrin—RACK1/PKCα signalling in human articular chondrocyte mechanotransduction

AbstractObjective The objective of this study was to examine PKC isozyme expression in human articular chondrocytes and assess roles for RACK1, a receptor for activated C kinase in the mechanotransduction process.Methods Primary cultures of human articular chondrocytes and a human chondrocyte cell line were studied for expression of PKC isozymes and RACK1 by western blotting. Following mechanical stimulation of chondrocytes in vitro in the absence or presence of anti-integrin antibodies and RGD containing oligopeptides, subcellular localization of PKCα and association of RACK1 with PKCα and β1 integrin was assessed.ResultsHuman articular chondrocytes express PKC isozymes α, γ, δ, ι, and λ. Following mechanical stimulation at 0.33Hz chondrocytes show a rapid, β1 integrin dependent, translocation of PKCα to the cell membrane and increased association of RACK1 with PKCα and β1 integrin.Conclusions RACK1 mediated translocation of activated PKCα to the cell membrane and modulation of integrin-associated signaling are likely to be important in regulation of downstream signaling cascades controlling chondrocyte responses to mechanical stimuli. Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd. All rights reserved