Downregulation of ubiquitin-dependent proteolysis by eicosapentaenoic acid in acute starvation

A number of acute wasting conditions are associated with an upregulation of the ubiquitin-proteasome system in skeletal muscle. Eicosapentaenoic acid (EPA) is effective in attenuating the increased protein catabolism in muscle in cancer cachexia, possibly due to inhibition of 15-hydroxyeicosatetraenoic acid (15-HETE) formation. To determine if a similar pathway is involved in other catabolic conditions, the effect of EPA on muscle protein degradation and activation of the ubiquitin-proteasome pathway has been determined during acute fasting in mice. When compared with a vehicle control group (olive oil) there was a significant decrease in proteolysis of the soleus muscles of mice treated with EPA after starvation for 24 h, together with an attenuation of the proteasome 'chymotryptic-like' enzyme activity and the induction of the expression of the 20S proteasome α-subunits, the 19S regulator and p42, an ATPase subunit of the 19S regulator in gastrocnemius muscle, and the ubiquitin-conjugating enzyme E214k. The effect was not shown with the related (n-3) fatty acid docosahexaenoic acid (DHA) or with linoleic acid. However, 2,3,5trimethyl-6-(3-pyridylmethyl)1,4-benzoquinone (CV-6504), an inhibitor of 5-, 12- and 15-lipoxygenases also attenuated muscle protein catabolism, proteasome 'chymotryptic-like' enzyme activity and expression of proteasome 20S α-subunits in soleus muscles from acute fasted mice. These results suggest that protein catabolism in starvation and cancer cachexia is mediated through a common pathway, which is inhibited by EPA and is likely to involve a lipoxygenase metabolite as a signal transducer. © 2001 Academic Press.

Effect of catechol derivatives on cell growth and lipoxygenase activity

Derivatives of salicylic acid have been synthesized as potential lipoxygenase inhibitors. Agents containing a phenolic dihydroxy moiety showed potent (IC 5010 -6-10 -7 M) inhibition of the growth of murine colonic tumour cells in vitro, and were effective inhibitors of 5-, 12- and 15-lipoxygenase in intact cells. The catechols were also potent inhibitors of rabbit reticulocyte 15-lipoxygenase (IC 50 ∼1 μM). © 2003 Elsevier Ltd. All rights reserved.

Alpha helical trans-membrane proteins:enhanced prediction using a Bayesian approach

Membrane proteins, which constitute approximately 20% of most genomes, are poorly tractable targets for experimental structure determination, thus analysis by prediction and modelling makes an important contribution to their on-going study. Membrane proteins form two main classes: alpha helical and beta barrel trans-membrane proteins. By using a method based on Bayesian Networks, which provides a flexible and powerful framework for statistical inference, we addressed alpha-helical topology prediction. This method has accuracies of 77.4% for prokaryotic proteins and 61.4% for eukaryotic proteins. The method described here represents an important advance in the computational determination of membrane protein topology and offers a useful, and complementary, tool for the analysis of membrane proteins for a range of applications.

Beta barrel trans-membrane proteins:enhanced prediction using a Bayesian approach

Membrane proteins, which constitute approximately 20% of most genomes, form two main classes: alpha helical and beta barrel transmembrane proteins. Using methods based on Bayesian Networks, a powerful approach for statistical inference, we have sought to address beta-barrel topology prediction. The beta-barrel topology predictor reports individual strand accuracies of 88.6%. The method outlined here represents a potentially important advance in the computational determination of membrane protein topology.