V. P. Ivanova

A current viewpoint on structure and evolution of collagens. I. Fibrillar collagens

This review summarizes current data of structure of the most representative group of superfamily of collagens—fibrillar collagens. The attention is focused on structural organization of individual domains and their functional role in the hierarchical stacking of collagen α-chains. There are presented characteristics of the main stages of biosynthesis and the supramolecular processing of fibrillar collagens. Also considered are some aspects of evolution of fibrillar collagens. The role of duplication of genome and genes, intergene combination, and translocation of exons in evolution of collagen genes is discussed.

The effect of a collagen tripeptide fragment (GER) on fibroblast adhesion and spreading depends on properties of an adhesive surface

The effect of collagen tripeptide fragment GER on the adhesion and spreading of mouse embryonic fibroblasts STO to different substrates (polystyrene plastic, poly-L-lysine, fibronectin, gelatin) has been studied. It was found that tripeptide GER was involved in fibroblast adhesion and spreading. The cell response depended both on the mode of tripeptide addition to culture medium and the substrate type. Coincubation of fibroblasts with tripeptide stimulated the cell attachment and spreading to untreated plastic and plastic coated with fibronectin or gelatin but did not change cell adhesion to immobilized poly-L-lysine. Preincubation of cells with tripeptide resulted in partial inhibition of fibroblast adhesion and spreading on fibronectin- and gelatin-coated substrata. It was shown that activation and inhibition of adhesive processes after tripeptide treating was higher on fibronectin than gelatin. The data obtained support the assumption about concerted action of tripeptide GER (activity was dependent both on the used concentration of the tripeptide and the mode of tripeptide addition to culture medium) and chemical characteristics of substrate (polymers of styrene and L-lysine, ECM proteins in native (fibronectin) or partly denatured (gelatin) form) on the cell adhesion and spreading. The main targets that GER peptide may affect during the formation of cell-substrate interactions are discussed.

Effect of habitat and motor activity of molluscs on fatty acid composition of triglycerides and phospholipids

A comparative analysis of fatty acids (FA) in neutral lipids and phospholipids of digestive gland and pedal muscle has been performed in molluscs from various ecological groups differing by belonging to sea or fresh water, trophic types or the associated motor activity. In freshwater pulmonary gastropods Lymnaea stagnalis and Lymnaea ovalis and marine prosobranchial molluscs Buccinum undatum and Littorina littorea the total content of ω3-acids in phospholipids of the studied tissues differed more than twice, predominantly due to the combined effect of temperature and salinity of the habitat. The lower viscosity of cell membranes in marine species (ω3/ω6 < 1) is determined to the greatest degree by the presence of eicosapentaenoic acid that accounts for 22–25% of the FA sum in marine species. Comparison of the molluscs by their trophic belonging has revealed the presence of linoleic acid in triglycerides in digestive glands of phytophages (8–12%), but the practically complete absence of this acid in the predator B. undulatum (< 0.8%). By mobility, L. littorea inhabiting the high-low tide littoral was inferior to freshwater pulmonary gastropods and to the marine predator, as it stops moving twice a day during the low tide. In phospholipids of pedal muscle of this mollusc the amount of long-chain polyunsaturated C: 22 FA was 3–6 times lower than that in other studied species, which might possibly indicate the role of these acids in functioning of the pedal muscle contractile tissue. On the whole, use of the FA characteristics as the parameters determining belonging to certain ecological group requires a certain caution due to a complex action of biotic and abiotic factors on the animal metabolism. The exception is the ω3/ω6 ratio in total phospholipids of fresh water and marine gastropods.

Current viewpoint on structure and on evolution of collagens. II. Fibril-associated collagens

Fibril-associated collagens (FACITs) form one of subfamilies included in family of collagens. Being minor components of connective tissue of multicellular animals, FACITs play an important role in structurization of extracellular matrix whose peculiarities determine essential intertissue differences. FACITs participate in regulation of sizes of banded collagen fibrils as well as are connecting links between various components extracellular matrix and cells in different tissues. Functional characteristics of FACIT molecules are determined by peculiarities of structural organization of their α-chains (breakdowns in collagenous domains and module structure of N-terminal noncollagenous sites), trimeric molecules (domains of trimerization) and supramolecular assemblies (mainly association with banded collagen fibrils and the inability to form homopolymeric supramolecular aggregates). The problem of evolution of this group of collagen molecules is also discussed. A hypothetical model of structural changes leading to formation of the FACIT subfamily is proposed.

Effect of synthetic polycation polyallylamine on adhesion and viability of CHL V-79 RJK Chinese hamster fibroblasts with various heat resistance

The effects of synthetic polycation polyallylamine (PAA) on the adhesion of CHL V-79 RJK fibroblasts and CHL V-79 RJK40 cells resistant to 40°C and the attachment of these cells to polycation immobilized on a polystyrene surface have been studied. We also investigated PAA cytotoxicity. It was shown that cell adhesion on polystyrene plastic coated with PAA depended on the PAA dose and did not depend on the heat resistance of the cells. The effect of PAA on cell adhesion to uncoated polystyrene surface after cell exposure to PAA depended not only on the polycation concentration but also on cell heat resistance. Pretreatment of cells with nontoxic concentrations of PAA inhibited CHL V-79 RJK cell adhesion and did not change adhesive properties of thermotolerant cells. PAA is toxic for CHL V-79 RJK and CHL V-79 RJK40 cells only at concentration of 100 μg/ml (MTT assay). PAA-induced acute toxicity was accompanied by necrotic-like cell death. Possible mechanisms of the PAA effect on the behavior of cells with different metabolic characteristics defined by heat resistance are discussed.

About paired correlation of π-electrons in tissue lipid extracts of animals of different evolutionary levels

With aid of optical methods, the presence of the paired correlations of π-electrons has been revealed in phospholipids as well as in triacylglyceride molecules. Used for analysis were lipid extracts of individual representatives of animals of various evolutionary levels—cartilaginous and bony fish and mammals differing by the content of unsaturated fatty acids in lipids. It has been established that the necessary condition for formation of electron pairs is interaction of lipid molecules with each other. An opinion is put forward that in the liquid crystal structure of the membrane monolayer there are two zones able to form electron pairs—the zone of location of ester bonds and the zone in the region of double bonds. Besides, the paired correlation in the phospholipid molecule electron system is accompanied by the absence of electric resistance of the membrane monolayer, which provides the monolayer superconductivity at low rates of movements of the “electron fluid.” It is to be noted that the very fact of the presence of the electron pair implies transfer of energy by small portions, which does not allow excitation of individual phospholipid molecules in the monolayer and promotes stability of the native membrane. Our data agree with the known statement of A. Pulman and B. Pulman that the life dynamicity is determined by dynamicity of the electron cloud in coupled or partially coupled systems.

Role of collagen tripeptide fragment GER on activation of adhesion and modification of fatty acid composition in membrane phospholipids of CHO-K1 cells

It has been found that the multiply repeated tripeptide fragment GER (Gly-Glu-Arg) from different collagen types stimulates the nonspecific adhesion of CHO-K1 cells. Activation of cell adhesion is accompanied by modifications to the fatty acid composition in the phospholipids of the cell membrane. Cell incubation with the synthetic GER peptide increases the unsaturation index of phosphatidylcholin (PC), phosphatidylethanolamine (PEA), and phosphatidylinositol (PI). Arachidonic (C20:4ω6) acid is mainly contributed to the increased index of PI. Not only arachidonic acid but other unsaturated fatty acids, such as docosatetraenoic (C22:4ω6), docosapentaenoic (C22:5ω3), and docosahexaenoic (C22:6ω3), are responsible for the increased index of PC and PEA. In addition, the elevation of the relative content of polyenoic fatty acids in PI is concomitant with a reduced amount of monoenoic fatty acids, mainly due to decline in the oleic (C18:1) acid level. The role of GER peptide in (1) the activation of cell adhesion as a regulator of active or inactive states of integrin receptors; (2) modification of fatty acid composition in major classes of phospholipids as a modulator of the fluidity in annular lipid zones surrounding to the adhesive molecules is discussed.

Fibronectins: Structural-functional relationships

This review summarized current data on the structure of fibronectin (FN), a multifunctional glycoprotein of vertebrates. FN is not only a permanent component of the extracellular matrix (ECM) but also an important regulator of cell functions via transformation of the ECM composition and organization and/or interaction with receptor and other membranebound cell proteins. Multifunctionality of FN owes hierarchical relationships between its structuralfunctional determinants, which comprise the linear ones (FN peptide fragments), association zones (surface contacts between the FN molecule and a FN-associated protein) and functional domains (those binding fibrin, heparin, gelatin and integrins). The modular architectonic principle of FN organization is pivotal to intrinsic adaptation of this glycoprotein to changing microenvironmental conditions. We also discuss the issue of key stages of FN fibrillogenesis with a special focus on the molecular mechanisms that underlie polymerization of FN molecules.

The role of defensin fragment in the regulation of fatty acid composition of membrane phospholipids in epithelial-like cells

It is shown that a tetrapeptide fragment of defensin does not alter the phospholipid composition in the membranes of CHO-K1 cells but regulates the fatty acid composition of phosphatidylcholine, phosphatidylethanolamine (PEA), phosphatidylserine (PS), and phosphatidylinositol (PI). Incubation of the cells in the presence of this tetrapeptide resulted in modification of unsaturated fatty acid composition in the studied phospholipids. The content of monoenoic (mainly C18 : 1ω9) and/or dienoic (C18 : 2ω6) fatty acids increased, while the level of polyenoic fatty acids decreased. It was found that in the polyenoic fatty acid group of the PEA, PS and PI molecules, the ω3-/ω6-acid ratio decreased mainly due to the lower content of long-chain ω3-acids with 20 and/or 22 carbonic atoms. The possible role of this peptide in inhibition of the activity of Δ6- and Δ5-desaturases involved in the synthesis of long-chain polyenoic fatty acids, the quantitative alteration of which in phospholipids influences physicochemical parameters in cell membranes, is discussed.

A defensin fragment regulates CHO-K1 cell spreading and induces renewal of fatty acid composition in cell membrane phospholipids

A tetrapeptide defensin fragment has been shown to stimulate the spreading of CHOK1 cells. The tetrapeptide investigated had virtually no effect on the composition of cell membrane phospholipids but participated in the regulation of the renewal of fatty acid composition of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol. Incubation of cells with the peptide resulted in a change in the composition of the unsaturated fatty acid residues in the phospholipids investigated: specifically, the content of monoenoic and/or dienoic acids increased and that of polyenoic acids decreased. The possible role of the peptide investigated (1) in the regulation of the functional activity of integrin receptors, and (2) in changes in the packing density of the phospholipid acyl chains in cell membrane microdomains, which affects the rates of integrin clustering and adhesion complex formation, is discussed.