Zhernosiekov D. Polyfunctional role of adhesive proteins in the formation of intercellular contacts in mammalian tissues in ontogenesis and under pathological states

The thesis describes the peculiarities of expression of adhesive proteins in mammalian tissues under physiological state and pathology. It was investigared the expression of cell adhesion protein N-CAM1 at the developing and aging tissues. It was determined the expression of minor exons of N-CAM1 in skeletal and heart muscles in rats at the different steps of the postnatal age. The classes of m-RNA that are responsible for synthesis of N-CAM1 isoforms in skeletal and heart muscles were determined. It was found that m-RNA expression of N-CAM1 was decreased during postnatal development, but increased at the aging tissues. The expression of minor exons was investigated in rat skeletal and heart tissue at postnatal development and aging. It was found that this expression was related with m-RNA of 5.2 and 2.9 kb. It was shown that VASE exon, which was expressed in heart, was practically absent in skeletal muscle. It was made the conclusion about tissue specific expression of this minor exon. The expression of N-CAM1 isoforms in skeletal and heart muscles was determined at all ages. There was no correlation between the m-RNA expression and the proportion of polypeptide isoforms of N-CAM1 in skeletal and heart tissue. Quantification of N-CAM1 protein, which was determined by enzyme-linked immunosorbent assay, showed that the amount of this protein was changed according to the animal’s age: there was a down regulation during postnatal development but the increase during aging in skeletal and heart muscles. It was concluded that N-CAM1 was involved in the compensatory mechanisms that took place in muscles during the aging of mammals. The expression of N-cadherin in rat tissues was investigated. Unlike N-CAM1 expression, there were no significant changes in N-cadherin m-RNA expression at all ages of skeletal and heart rat tissues. The classes of m-RNA which are responsible for N-, E- and P-cadherin expression in brain, liver, kidney, lung, heart and skeletal muscles were determined. We concluded that each of the investigated cadherins was characterized by tissue-specific distribution. The analysis of N-cadherin polypeptide isoforms in rat tissues showed the presence of the main isoform with molecular mass 130 kDa. The crucial role of of N-cadherin in memory formation was not shown on the model of passive avoidance in rats. The blocking of cadherin proteins with specific antibodies in brain and hippocampus structures did not lead to disruption of memory formation in animals. It was shown that components of plasminogen/plasmin system made a modulating effect on adhesive interaction between platelets. Lys-plasminogen unlike Glu-form showed an inhibitory effect on platelet aggregation induced by ADP, thrombin and collagen. It was determined that inhibitory effect of Lys-plasminogen was mediated by LBS of its kringle structures. Lys-plasminogen had no inhibitory effect of on the adhesive contacts which were mediated by GP Іb-IX-V and von Willebrand factor. Lys-plasminogen caused the negative influence on actin rearrangement in platelets stimulated by thrombin or collagen. It could be one of the possible mechanisms of antiadhesive and antisecretory action of Lys-plasminogen because, as it was shown, the preliminary incubation of platelets with Lys-plasminogen followed by thrombin stimulation led to the decrease of P-selectin-positive platelets in preparations. Lys-plasminogen had a modulating effect on vitronectin exposure on the surface of activated platelets. We proposed the mechanism of bivalent interaction of Lys-plasminogen with a surface platelet receptor and vitronectin that was released from alpha-granules due to platelet activation. So, it was proved that functional changes in tissues of mammalian organisms are related with the changes of the expression of specific adhesive proteins. Adhesive interactions between platelets, which provide the functional destination of these cells, are modulated by the components of plasminogen/plasmin system.