Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fungal gliotoxin (GT) is a potent inhibitor of the O(2)(-)-generating NADPH oxidase of neutrophils. We reported that GT-treated neutrophils fail to phosphorylate p47(phox), a step essential for the enzyme activation, because GT prevents the colocalization of protein kinase C betaII with p47(phox) on the membrane. However, it remains unanswered whether GT directly affects any of NADPH oxidase components. Here, we examine the effect of GT on the NADPH oxidase components in the cell-free activation assay. The O(2)(-)-generating ability of membranes obtained from GT-treated neutrophils is 40.0 and 30.6% lower, respectively, than the untreated counterparts when assayed with two distinct electron acceptors, suggesting that flavocytochrome b(558) is affected in cells by GT. In contrast, the corresponding cytosol remains competent for activation. Next, GT addition in vitro to the assay consisting of flavocytochrome b(558) and cytosolic components (native cytosol or recombinant p67(phox), p47(phox), and Rac2) causes a striking inhibition (50% inhibitory concentration = 3.3 microM) when done prior to the stimulation with myristic acid. NADPH consumption is also prevented by GT, but the in vitro assembly of p67(phox), p47(phox), and Rac2 with flavocytochrome b(558) is normal. Posterior addition of GT to the activated enzyme is ineffective. The separate treatment of membranes with GT also causes a marked loss of flavocytochrome b(558)'s ability to reconstitute O(2)(-) generation, supporting the conclusion at the cellular level. The flavocytochrome b(558) heme spectrum of the GT-treated membranes stays, however, unchanged, showing that hemes remain intact. These results suggest that GT directly harms site(s) crucial for electron transport in flavocytochrome b(558), which is accessible only before oxidase activation.
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PMID:Fungal metabolite gliotoxin targets flavocytochrome b558 in the activation of the human neutrophil NADPH oxidase. 1561 59

The present study tests the hypothesis that age-related changes in patterns of agonist-induced myofilament Ca(2+) sensitization involve corresponding differences in the relative contributions of thick- and thin-filament regulation to overall myofilament Ca(2+) sensitivity. Posterior communicating cerebral arteries from term fetal and nonpregnant adult sheep were used in measurements of cytosolic Ca(2+), myosin light chain (MLC) phosphorylation, and contractile tensions induced by varying concentrations of K(+) or serotonin [5-hydroxytryptamine (5-HT)]. The results were used to assess the relative contributions of the relationships between cytosolic Ca(2+) and MLC phosphorylation (thick-filament reactivity), along with the relationships between MLC phosphorylation and contractile tension (thin-filament reactivity), to overall myofilament Ca(2+) sensitivity. For K(+)-induced contractions, both fetal and adult arteries exhibited similar basal myofilament Ca(2+) sensitivity. Despite this similarity, thick-filament reactivity was greater in fetal arteries, whereas thin-filament reactivity was greater in adult arteries. In contrast, 5-HT-induced contractions exhibited increased myofilament Ca(2+) sensitivity compared with K(+)-induced contractions for both fetal and adult cerebral arteries, and the magnitude of this effect was greater in fetal compared with adult arteries. When interpreted together with our previous studies of 5-HT-induced myofilament Ca(2+) sensitization, we attributed the present effects to agonist enhancement of thick-filament reactivity in fetal arteries mediated by G protein receptor activation of a PKC-independent but RhoA-dependent pathway. In adult arteries, agonist stimulation enhanced thin-filament reactivity was also probably mediated through G protein-coupled activation of RhoA-dependent and PKC-independent mechanisms. Overall, the present data demonstrate that agonist-enhanced myofilament Ca(2+) sensitivity can be partitioned into separate thick- and thin-filament effects, the magnitudes of which are different between fetal and adult cerebral arteries.
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PMID:Postnatal maturation modulates relationships among cytosolic Ca2+, myosin light chain phosphorylation, and contractile tone in ovine cerebral arteries. 1766 Mar 92