Exploring the Interplay between Polyphenols and Lysyl Oxidase Enzymes for Maintaining Extracellular Matrix Homeostasis.

Collagen, the most abundant structural protein found in mammals, plays a vital role as a constituent of the extracellular matrix (ECM) that surrounds cells. Collagen fibrils are strengthened through the formation of covalent cross-links, which involve complex enzymatic and non-enzymatic reactions. Lysyl oxidase (LOX) is responsible for catalyzing the oxidative deamination of lysine and hydroxylysine residues, resulting in the production of aldehydes, allysine, and hydroxyallysine. These intermediates undergo spontaneous condensation reactions, leading to the formation of immature cross-links, which are the initial step in the development of mature covalent cross-links. Additionally, non-enzymatic glycation contributes to the formation of abnormal cross-linking in collagen fibrils. During glycation, specific lysine and arginine residues in collagen are modified by reducing sugars, leading to the creation of Advanced Glycation End-products (AGEs). These AGEs have been associated with changes in the mechanical properties of collagen fibers. Interestingly, various studies have reported that plant polyphenols possess amine oxidase-like activity and can act as potent inhibitors of protein glycation. This review article focuses on compiling the literature describing polyphenols with amine oxidase-like activity and antiglycation properties. Specifically, we explore the molecular mechanisms by which specific flavonoids impact or protect the normal collagen cross-linking process. Furthermore, we discuss how these dual activities can be harnessed to generate properly cross-linked collagen molecules, thereby promoting the stabilization of highly organized collagen fibrils.

Yeast strain Saccharomyces cerevisiae BYT45 lacking the cation extrusion systems ENA1-5 and NHA1 is suitable for the characterization of TASK-3 potassium channel antagonists.

Finding new potential antagonists of potassium channels is a continuing task. TASK potassium channels operate over a large physiological range of membrane voltages, why they are thought to contribute to the excitability and resting potential of mammalian membrane potentials. Additionally, they are regulated by extracellular stimuli like changes in pH and K+ concentrations. TASK malfunctions are associated with diseases, which makes them popular targets for the search of new antagonists. Identification of channel inhibitors can be a time-consuming and expensive project. Here, we present an easy-to-use and inexpensive yeast system for the expression of the two-pore domain K+ channel TASK-3, and for the characterization of TASK-3 antagonists. The Saccharomyces cerevisiae strain BYT45 was used to express guinea pig TASK-3. The system allowed the expression and characterization of TASK-3 at variable pH values and K+ concentrations. Three known TASK-3 antagonists have been tested in the BYT45 yeast system: PK-THPP, ZnCl2 and Bupivacaine. Their inhibitory effect on TASK-3 was tested in solid and liquid media assays, and half maximal inhibitory concentrations were estimated. Although the system is less sensitive than more refined systems, the antagonistic activity could be confirmed for all three inhibitors.

A minimal cysteine motif required to activate the SKOR K+ channel of Arabidopsis by the reactive oxygen species H2O2.

Reactive oxygen species (ROS) are essential for development and stress signaling in plants. They contribute to plant defense against pathogens, regulate stomatal transpiration, and influence nutrient uptake and partitioning. Although both Ca(2+) and K(+) channels of plants are known to be affected, virtually nothing is known of the targets for ROS at a molecular level. Here we report that a single cysteine (Cys) residue within the Kv-like SKOR K(+) channel of Arabidopsis thaliana is essential for channel sensitivity to the ROS H(2)O(2). We show that H(2)O(2) rapidly enhanced current amplitude and activation kinetics of heterologously expressed SKOR, and the effects were reversed by the reducing agent dithiothreitol (DTT). Both H(2)O(2) and DTT were active at the outer face of the membrane and current enhancement was strongly dependent on membrane depolarization, consistent with a H(2)O(2)-sensitive site on the SKOR protein that is exposed to the outside when the channel is in the open conformation. Cys substitutions identified a single residue, Cys(168) located within the S3 α-helix of the voltage sensor complex, to be essential for sensitivity to H(2)O(2). The same Cys residue was a primary determinant for current block by covalent Cys S-methioylation with aqueous methanethiosulfonates. These, and additional data identify Cys(168) as a critical target for H(2)O(2), and implicate ROS-mediated control of the K(+) channel in regulating mineral nutrient partitioning within the plant.