It is known that PMA (phorbol-12-myristate-13-acetate) can activate the classical and novel protein kinase C isoenzymes (cPKC α, β, γ and nPKC δ, ε, η, ), while the calcium ion can induce only the activity of cPKC. Calcineurin binding protein (Cabin
1) belongs to the group of endogenous inhibitors of calcineurin. Cabin 1 becomes hyperphosphorylated in response to PKC activation and may play a negative role in calcineurin signalling. It was observed that both PMA treatment and the increase in intracellular Ca2+ contributed to the reduction
of calcineurin activity in human peripheral blood mononuclear cells without modulating the mRNA and the protein levels of calcineurin. PMA and Ca-ionophore (A23187), the activating agents of PKC, applied alone or in combination, significantly increased the phosphorylation state of Cabin 1
as revealed by immunoprecipitation of Cabin 1 detecting its phospho-Ser content by specific antibodies. GF109203X, an inhibitor of the classic and the novel protein kinase C isoenzymes, and Gö6976, the selective inhibitor of the classical cPKC isoenzymes were able to abolish the effect
of PMA or/and Ca-ionophore on the calcineurin activity with concomitant reversal of the hyperphosphorylation of Cabin 1. The calcineurin/Cabin 1 system was not influenced by Rottlerin, an inhibitor of PKC δ isoenzyme either in the absence or in the presence of Ca-ionophore and PMA. We
presented evidence for the prominent role of cPKC α, β, γ isoenzymes in the inhibition of calcineurin as induced by PMA and Ca-ionophore. We demonstrated also that hyperphosphorylation of Cabin 1 by PMA/Ca2+-activated cPKC isoenzymes resulted in a simultaneous inhibition of
calcineurin in peripheral blood mononuclear cells. These results suggest a negative regulatory role for Cabin 1 in calcineurin signalling and provide a possible mechanism of feedback inhibition through cross-talk between PKC and calcineurin.
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Document Type: Research Article
Cell Biology and Signalling Research Group of the Hungarian Academy of Sciences, Department of Medical Chemistry, Research Centre for Molecular Medicine, University of Debrecen, H-4032 Debrecen, Hungary
Publication date: September 1, 2007
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The International Journal of Molecular Medicine is a monthly, peer-reviewed journal devoted to the publication of high quality studies related to the molecular mechanisms of human disease. The journal welcomes research on all aspects of molecular and clinical research, ranging from biochemistry to immunology, pathology, genetics, human genomics, microbiology, molecular pathogenesis, molecular cardiology, molecular surgery and molecular psychology.
The International Journal of Molecular Medicine aims to provide an insight for researchers within the community in regard to developing molecular tools and identifying molecular targets for the diagnosis and treatment of a diverse number of human diseases.
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