The intracellular tyrosine residues of the ATP-gated P2X(1) ion channel are essential for its function

In order to gain a first insight into the effects of reactive oxygen species (ROS) on plant mitochondria, we studied the effect of the ROS producing system consisting of xanthine plus xanthine oxidase on the rate of membrane potential (DeltaPsi) generation due to either succinate or NADH addition to durum wheat mitochondria as monitored by safranin fluorescence. We show that the early ROS production inhibits the succinate-dependent, but not the NADH-dependent, DeltaPsi generation and oxygen uptake. This inhibition appears to depend on the impairment of mitochondrial permeability to succinate. It does not involve mitochondrial thiol groups sensitive to either mersalyl or N-ethylmaleimide and might involve both protein residues and/or membrane lipids, as suggested by the mixed nature. We propose that, during oxidative stress, early generation of ROS can affect plant mitochondria by impairing metabolite transport, thus preventing further substrate oxidation, DeltaPsi generation and consequent large-scale ROS production.     

Cathepsins B, K, and L are regulated by a defined collagen type II peptide via activation of classical protein kinase C and p38 MAP kinase in articular chondrocytes

Degradation of the extracellular matrix (ECM) is a prominent feature in osteoarthritis (OA), which is mainly because of the imbalance between anabolic and catabolic processes in chondrocytes resulting in cartilage and bone destruction. Various proteases act in concert to degrade matrix components, e.g. type II collagen, MMPs, ADAMTS, and cathepsins. Protease-generated collagen fragments may foster the destructive process. However, the signaling pathways associated with the action of collagen fragments on chondrocytes have not been clearly defined. The present data demonstrate that the N-terminal telopeptide of collagen type II enhances expression of cathepsins B, K, and L in articular chondrocytes at mRNA, protein, and activity levels, mediated at least in part through extracellular calcium. We also demonstrate that the induction is associated with the activation of protein kinase C and p38 MAP kinase.     

Identification of blapsins A and B as potent small-molecule 14-3-3 inhibitors from the insect Blaps japanensis

In this study, we report three novel naturally occurring compounds, blapsins A (1) and B (2), and blapsamide (3) from the ethanol extract of the stink beetle, Blaps japanensis. The structures of these compounds were determined using spectroscopic methods. Compound 3 is a phenolic compound bearing a formamido group in the structure. Functional studies revealed that compounds 1 and 2 potently inhibited 14-3-3 protein-protein interactions (PPIs) with IC(50) values of 9.2 and 10.0 μM as determined by an ELISA assay, and 2.0 and 2.5 μM in an FP assay, respectively. These compounds represent the first example of natural small-molecule 14-3-3 inhibitors.     

Discovery of thieno[2,3-c]pyridines as potent COT inhibitors

Evaluation of hit chemotypes from high throughput screening identified a novel series of 2,4-disubstituted thieno[2,3-c]pyridines as COT kinase inhibitors. Structural modifications exploring SAR at the 2- and 4-positions resulting in inhibitors with improved enzyme potency and cellular activity are disclosed.     

The heterotrimeric G protein G(i3) regulates hepatic autophagy downstream of the insulin receptor

Compelling evidence suggests that the heterotrimeric G protein G(i3) specifically transmits the antiautophagic effects of insulin and amino acids in the liver. This points to a previously unrecognized cross talk between the insulin receptor tyrosine kinase and G(i3). Interestingly, G(i3) is localized not only to plasma membranes but also to membranes of the autophagosomal compartment. Furthermore, as part of insulin's or phenylalanine's actions to inhibit autophagy, G(i3) is redistributed away from autophagosomes. Therefore, endomembrane-associated rather than plasma membrane-localized G(i3) may serve as the target of insulin's endocrine and metabolic actions. We therefore propose that the function and regulation of organelle-associated heterotrimeric G proteins may be different from their roles at the plasma membrane where they act as signal transducers of seven-transmembrane receptors. Here, we discuss recent findings and propose a function for G(i3) in mTOR-dependent signaling pathways. We hypothesize that G(i) family members may have tissue-specific roles in the regulation of autophagy under different physiological and pathological conditions.