Abstract
We studied the translocation of protein kinase C (PKC), the endogenous phosphorylation and presence in the membrane fraction of p47phox (the 47-kDa cytosolic component of the phagocyte NADPH oxidase), and the O-.2 production in human adherent monocytes (HAMs). This was performed under phorbol myristate acetate (PMA) or diacylglycerol stimulation after cell preincubation in the presence of either 13-methyltetradecanoate or arachidonate. At 3 nM and 30 microM, both fatty acids had enhancing and depressing effects, respectively, on PKC translocation and O-.2 production strictly depending on the PMA- or diacylglycerol-stimulated state of the cell. Endogenous phosphorylation and membrane presence of p47phox were markedly reinforced in PMA-stimulated HAMs in the presence as compared to the absence of 13-methyltetradecanoate. These results emphasize the fact that in intact cells the capacity of both FAs to potentiate or depress the HAM O-.2 production is mediated by a direct action on the PKC membrane translocation leading to a simultaneous endogenous phosphorylation and membrane translocation of p47phox. They confirm the recent findings (Kadri-Hassani, N., Léger, C. L., and Descomps, B. (1995) J. Lipid Med. Cell Signal. 11, 159-173) on the PKC-mediated, adherent monocyte-specific capacity of these fatty acids and others (with the exception of linear saturated fatty acids) to enhance the PMA-stimulated O-.2 production at nanomolar concentrations and to depress it at micromolar concentrations.
Highlights
We studied the translocation of protein kinase C (PKC), the endogenous phosphorylation and presence in the membrane fraction of p47p h ox, and the
Before adding phorbol myristate acetate (PMA), more than 90% of the activity was localized in the cytosol, whereas adding 100 nM PMA brought about a redistribution of the PKC activity resulting in a substantial increase in the proportion of the activity recovered in the membrane fraction
Our results demonstrate the fact that, in intact cells, the capacity of both is015:0 and 20:4n-6 to potentiate or depress the human adherent monocytes (HAMs) 0; production is mediated by an action on the PKC
Summary
Human Adherent Monocytes under Phorbol I2-Myristate I3-Acetate or Diacylglycerol Activation Can Be Explained by the Modulation of Protein Kinase C and p47p h ox Translocation*. It was established that (i) they activate PKC in the absence of the usual cofactors PtdSer and Ca 2 + , these latter being needed, in the case of DAG or PMA activation, and (ii) they are able in particular to activate the cytosolic form ofPKC [11], In a cell-free system and in the presence of phospholipids and Ca2 + , evidence for a synergistic action ofDAG and unsaturated FAs was provided [12]. Fatty Acid Bimodal Action on PKC and p47 ofAdherent Monocytes nanomolar concentrations and a depressing effect at micromolar concentrations on the NADPH oxidase-mediated production of O~ [16] This novel bimodal action was assumed to be linked to PKC activity, and its magnitude was found to be largely dependent on the FA chain structure. We concluded that FAs act on PKC and p47p h ox translocation and endogenous p47p h ox phosphorylation in a manner that accounts for their concentration-dependent bimodal action on the PMA-stimulated O~ production
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