Phosphorylation of adrenal histone H3 is affected by angiotensin, ACTH, dibutyryl cAMP, and atrial natriuretic peptide

A Novel Systems-Biology Algorithm for the Analysis of Coordinated Protein Responses Using Quantitative Proteomics

The coordinated behavior of proteins is central to systems biology. However, the underlying mechanisms are poorly known and methods to analyze coordination by conventional quantitative proteomics are still lacking. We present the Systems Biology Triangle (SBT), a new algorithm that allows the study of protein coordination by pairwise quantitative proteomics. The Systems Biology Triangle detected statistically significant coordination in diverse biological models of very different nature and subjected to different kinds of perturbations. The Systems Biology Triangle also revealed with unprecedented molecular detail an array of coordinated, early protein responses in vascular smooth muscle cells treated at different times with angiotensin-II. These responses included activation of protein synthesis, folding, turnover, and muscle contraction - consistent with a differentiated phenotype-as well as the induction of migration and the repression of cell proliferation and secretion. Remarkably, the majority of the altered functional categories were protein complexes, interaction networks, or metabolic pathways. These changes could not be detected by other algorithms widely used by the proteomics community, and the vast majority of proteins involved have not been described before to be regulated by AngII. The unique capabilities of The Systems Biology Triangle to detect functional protein alterations produced by the coordinated action of proteins in pairwise quantitative proteomics experiments make this algorithm an attractive choice for the biological interpretation of results on a routine basis.

Apoptosis induced by gliotoxin is preceded by phosphorylation of histone H3 and enhanced sensitivity of chromatin to nuclease digestion

The fungal toxin gliotoxin induces apoptotic cell death in a variety of cells. Apoptosis induced in thymocytes by gliotoxin is rapid, and DNA fragmentation is observable within 4 h treatment. Apoptosis induced by gliotoxin is calcium-independent and unaffected by protein synthesis inhibitors. We have previously shown that gliotoxin results in phosphorylation of a 16.3-kDa protein within 10 min treatment of thymocytes. Here we show that this protein is histone H3 and phosphorylation occurs on Ser-10. Cyclic AMP levels and activity of protein kinase A (PKA) are raised in cells treated with gliotoxin. Apoptosis is inhibited by genistein which also inhibits PKA and histone H3 phosphorylation. Apoptosis is also inhibited by a number of specific inhibitors of PKA suggesting apoptosis induced by gliotoxin is modulated by this kinase. The agents forskolin and cholera toxin do not induce rapid phosphorylation of H3 although some increase in phosphorylation of H3 does occur after 8 h with these agents. Forskolin and cholera toxin also induce apoptosis but over a longer time course than gliotoxin. In all cases levels of apoptosis correlate with degree of H3 phosphorylation. Cells treated with gliotoxin show an early sensitivity to micrococcal nuclease and DNase I digestion indicating a functional relationship between DNA fragmentation and H3 phosphorylation.

Effect of protein kinase inhibitors on ACTH-stimulated aldosterone production in rat zona glomerulosa cells

In order to obtain further evidence for the involvement of protein kinases in the short-term ACTH-stimulated aldosterone synthesis in rat zona glomerulosa cells, the effects of three different compounds with protein kinase inhibitory properties were investigated. Staurosporine, H-7 and trifluoperazine inhibited ACTH-stimulated aldosterone release in a dose-dependent manner. While the inhibitory effect of H-7 was reversible upon washing of the cells with inhibitor-free medium, the inhibition was maintained in cells treated with staurosporine or trifluoperazine. In contrast to the stimulated production, basal release of aldosterone even at the highest drug concentrations tested was not completely inhibited. We thus conclude that protein kinases may play a crucial role in short-term ACTH-stimulated aldosterone production in rat glomerulosa cells.