Anti-phospholipase A2 and anti-inflammatory activity of Santolina chamaecyparissus

The activity of the Santolina chamaecyparissus methanol extract was tested against the phospholipase A2 (PLA2)-induced mouse paw edema and in vitro inhibition of PLA2 activity. After fractionation, only the dichloromethane extract was active against the PLA2 in vitro test. In addition, it reduced the edema induced by arachidonic acid, and by 12-O-tetradecanoylphorbol-13-acetate in a multidose test. After chromatography on silicagel and gel filtration on Sephadex, and using an in vitro anti-PLA2 assay-guided process, we have isolated and identified from the dichloromethane extract the flavone nepetin and four sesquiterpenes.     

Anti-phospholipase C antibodies inhibit the lectin-induced proliferation of human lymphocytes

A novel approach was used to assess the role of phosphoinositide hydrolysis in the mitogenic action of phytohemagglutinin (PHA) or concanavalin A (ConA). The treatment of human peripheral blood leukocytes (PBL) with monospecific antibodies against phospholipase C (PLC) produced a dose-dependent inhibition (up to 100%) of PHA (10 g/ml) or ConA (25 g/ml) proliferative effects. Thus, the activation of membrane-bound PLC is asine-qua-non condition for lectin-induced proliferation of T lymphocytes. The key-role of PLC versus protein kinase C (PKC) is stressed by the fact that the inhibition of PKC with Hidaka's compound H-7 (40 M) produced only a partial blockade (about 25%) of lectin mitogenic effect.To whom correspondence should be addressed.     

Structured proteins and proteins with internal disorder

The point of view that a uniquely folded protein tertiary structure is required for the protein functioning has been prevailing in the literature quite recently. However of lately it has been found that many proteins in a cell have no such structure in an isolated state, though they have a well-defined function in physiological conditions. These proteins were named as proteins with natural or internal disorder. The portion of disordered regions in such proteins may vary from a sequence of several amino acids to a completely disordered sequence containing from tens to hundreds of amino acids. The main difference of these proteins from the structured (globular) ones is that they have no unique tertiary structure in an isolated state and acquire it after interaction with their partners. Their conformation in such a complex depends on the interacting partner and not only on their own amino acid sequence, which is specific for structured (globular) proteins. The problem of structural and functional relations in the structured proteins and proteins with internal disorder is discussed in this review. The complexity of the problem and its potential solutions are illustrated by the example of elongation factors EFlA.     

Structured proteins and proteins with intrinsic disorder

Until recently, the point of view that the unique tertiary structure is necessary for protein function has prevailed. However, recent data have demonstrated that many cell proteins do not possess such structure in isolation, although displaying a distinct function under physiological conditions. These proteins were named the naturally, or intrinsically, disordered proteins. The fraction of intrinsically disordered regions in such proteins may vary from several amino acid residues to a completely unordered sequence of several tens or even several hundreds of residues. The main distinction of these proteins from structured (globular) proteins is that they have no unique tertiary structure in isolation and acquire it only upon interaction with their partners. The conformation of these proteins in a complex is determined not only by their own amino acid sequence (as is typical of structured, or globular, proteins) but also by the interacting partner. This review discusses the structure-function relationships in structured and intrinsically disordered proteins. The intricateness of this problem and the possible ways to solve it are illustrated by the example of the EF1A elongation factor family.     

Ribosomal proteins

Summary Ribosomal proteins fromE. coli mutant N421 which is a spontaneous revertant from streptomycin dependence to independence have been compared to those of the wild type by two-dimensional polyacrylamide gel electrophoresis and by four immunochemical methods. The only detectable difference is a change in protein S5. This finding suggests that reversion from streptomycin dependence to independence can be caused not only by a mutation in protein S4, as described earlier, but also in protein S5.     

Autophagic proteins

Oxygen (O₂), while essential for aerobic life, can also cause metabolic toxicity through the excess generation of reactive oxygen species (ROS). Pathological changes in ROS production can originate through the partial reduction of O₂ during mitochondrial electron transport, as well as from enzymatic sources. This phenomenon, termed the oxygen paradox, has been implicated in aging and disease, and is especially evident in critical care medicine. Whereas high O₂ concentrations are utilized as a life-sustaining therapeutic for respiratory insufficiency, they in turn can cause acute lung injury. Alveolar epithelial cells represent a primary target of hyperoxia-induced lung injury. Recent studies have indicated that epithelial cells exposed to high O₂ concentrations die by apoptosis, or necrosis, and can also exhibit mixed-phenotypes of cell death (aponecrosis). Autophagy, a cellular homeostatic process responsible for the lysosomal turnover of organelles and proteins, has been implicated as a general response to oxidative stress in cells and tissues. This evolutionarily conserved process is finely regulated by a complex interplay of protein factors. During autophagy, senescent organelles and cellular proteins are sequestered in autophagic vacuoles (autophagosomes) and subsequently targeted to the lysosome, where they are degraded by lysosomal hydrolases, and the breakdown products released for reutilization in anabolic pathways. Autophagy has been implicated as a cell survival mechanism during nutrient-deficiency states, and more generally, as a determinant of cell fate. However, the mechanisms by which autophagy and/or autophagic proteins potentially interact with and/or regulate cell death pathways during high oxygen stress, remain only partially understood.     

Moonlighting proteins

The idea of one gene--one protein--one function has become too simple because increasing numbers of proteins are found to have two or more different functions. The multiple functions of such moonlighting proteins add another dimension to cellular complexity and benefit cells in several ways. However, cells have had to develop sophisticated mechanisms for switching between the distinct functions of these proteins.     

Cytokinin-binding proteins

This article is focused on the modalities of reception of cytokinins which remain largely unknown. It summarizes the main steps of the different protocols used to study cytokinin-binding proteins (CBPs). We place emphasis on the significance and specificity of the detection according to the properties of the probes used: radioactive or photoreactive cytokinins, fluorescent anticytokinins, anti-idiotype antibodies. The purification procedures are also examined. The cellular localisation and the putative physiological roles of the numerous and different CBPs found are considered. The interest of genetic and molecular studies is discussed.