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.
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 PKCalpha and association of RACK1 with PKCalpha and beta1 integrin was assessed.
Human articular chondrocytes express PKC isozymes alpha, gamma, delta, iota, and lambda. Following mechanical stimulation at 0.33Hz chondrocytes show a rapid, beta1 integrin dependent, translocation of PKCalpha to the cell membrane and increased association of RACK1 with PKCalpha and beta1 integrin.
RACK1 mediated translocation of activated PKCalpha 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.