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More than a half of all known proteins contain covalently attached oligosaccharides that represent a significant part of their molecular structure. It is estimated that over 500 specific enzymes (glycosidases and glycosyltransferases) are involved in the synthesis of carbohydrate structures on glycoconjugates, and the whole process is very complex and energetically expensive for the cell. Due to very high structural variability and the lack of adequate methods to analyze it, carbohydrate parts of glycoconjugates were ignored by most of the scientific community until only few years ago. However, thanks to the development of novel methods, in the last years there is an exponential increase in the knowledge about the physiological roles of carbohydrate structures. As well as many other diseases, rheumatoid arthritis is associated with specific changes in protein glycosylation. Majority of studies focused on galactosylation of IgG, but recently we demonstrated that the most prominent glycosylation change in both rheumatoid arthritis and juvenile rheumatoid arthritis is the increase in fucosylation. Using a novel method based on recently developed BioprobeŽ technology we were able to show that juvenile rheumatoid arthritis is also associated with changes in the activity of serum lectins. Although the functional significance of these changes are still not known, they could prove to be a valuable diagnostic marker for rheumatoid diseases.

GP62 is a member of the stress glycoprotein family that was proposed to have a chaperone-like function in the heat-shock response. Using lectin blotting we have analyzed glycosylation of GP62 in A1235 cells exposed to heat-shock (2 h at 42ºC), subculturing and UV-radiation. As expected, heat-shock resulted in the appearance of significant amounts of GP62, which was undetectable in the control cells. SNA, DSA and PHA-E lectins recognized GP62, while BSA I, Con A, RCA I, SJA, UEA-I, VVA and WGA did not. Based on this information, it is possible to identify some segments of carbohydrate structures attached to GP62. GP62 appears to contain a bianntenary complex-type oligosaccharide with at least one a(2,6)-linked sialic acid, N-acetyllactosamine and bissecting b(1,4)-linked N-acetylglucosamine. While performing these experiments we noticed that heat-shock is not necessary for the induction of GP62, and that even simple subculturing of cells was a sufficient stimulus. However, the dynamics of the induction was somewhat different. When GP62 was induced by a heat-shock, it appeared within 4 h after the end of heat treatment and remained on a relatively high level for at least next 24 h. After subculturing, GP62 appeared after only 2 h, stayed on a high level during the following 2 h, and virtually disappeared after 24 h. Interestingly, glycosylation of GP62 induced by subculturing was found to be different from glycosylation of GP62 induced by heat-shock. In addition to SNA, DSA and PHA-E lectins, which recognized GP62 induced by heat-shock, GP62 induced by subculturing was also recognized by RCA I and WGA lectins. Thus, in addition to carbohydrates present on GP62 induced by heat-shock, GP62 induced by subculturing contained terminal galactose and N-acetylglucosamine residues. Contrary to heat-shock and subculturing, when cells were exposed to UV-C radiation, GP62 did not appear, suggesting that it is associated with some, but not all, cellular stress-response pathway.

Metabolic response to psychological stress is a very complex and demanding physiological process. It involves many organs and diversely affects individual organ systems. Though highly important for survival in ever changing environment, when excessively activated, it becomes associated with various detrimental effects. A number of epidemiological and experimental studies conducted during the past few years have clearly demonstrated a link between stress and the development and course of many diseases from simple virus infections and gastric ulcers to cardiovascular diseases and cancer1. However, main biochemical pathways linking stress to the development of diseases are still not understood. We have shown that stress causes tissue- and stressor-specific changes of glycoprotein structure and glycosyltransferase activity2. We have also noticed that the expression of carbohydrate-binding proteins vary depending on the type of stress experience. When studying the effects of stress on the expression of galactoside-specific galectin-3, we have found that the extent and direction of changes of galectin-3 expression are strongly dependent on the origin of disturbance. While immobilization, heat-shock, and subculturing decreased cellular levels of galectin-3, UV-C irradiation and alkylating agents induced its expression. Transcription factors NFкB and Jun were shown to be involved in at least some of these stress related processes. 1. M.Flögel and G.Lauc, in Encyclopedia of Stress, G. Fink ed., Academic Press, 2000, p. 678-673. 2. G.Lauc and M.Flögel, in Encyclopedia of Stress, G. Fink ed., Academic Press, 2000, p 276-282.