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Effect of Hyperthermia on Activity of Three Glycosyltransferases in Chinese Hamster Ovary Cells¹

Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205 [K. J. H., A. S.]; and the Department of Gynecologic Oncology, Roswell Park Memorial Institute, Buffalo, New York 14263 [S. K. C.]

We measured activities of three glycosyltransferases at various times during heat-induced thermotolerance development. Glycosyltransferases are normally located in the Golgi apparatus and catalyze cellular glycosylation reactions. UDP-Gal:N-acetylglucosamine ß1,4-galactosyltransferase (ß1,4-GalT) is known to participate in the formation of N-linked glycoproteins; when compared to cell survival, ß1,4-GalT activity was significantly more heat resistant (50% loss of activity: 80 min, 45°C) and showed little elevation at a time when thermotolerance was fully expressed. However, ß1,4-GalT activity increased twofold by 24-h postheating when thermotolerance had begun to decay.

Activity of ß1,4-GalT was compared with glycosyltransferase activities that are considered to be specific for O-linked glycoproteins: UDP-Gal:N-acetylgalactosamine-ß1,3-galactosyltransferase (ß1,3-GalT), and UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase (Gal-NAcT). Heat-inactivation experiments with heating times up to 60 min at 45°C failed to reduce either activity below that of unheated control cells. Instead both ß1,3-GalT and GalNAcT activity increased approximately twofold immediately after 10 min at 45°C. Activity of ß1,3-GalT rapidly decreased with time after heating and returned to control levels by 6-h postheating. In contrast, GalNAcT activity continued to increase with time after 10 min at 45°C, and was 4.5-fold above unheated controls by 6-h postheating. GalNAcT activity returned to control levels 24- to 48-h postheating. A comparison with the cellular survival response showed that GalNAcT activity preceded thermotolerance expression by 2–4 h and also decayed more rapidly than heat resistance in thermotolerant cells. These data, together with other published results, suggest that expression of thermotolerance may be associated with enhanced glycosylation of intracellular proteins.

¹ This investigation was supported by USPHS Grants CA-33405 and CA-35689, awarded by the National Cancer Institute, DHHS.

² To whom requests for reprints should be addressed, at Medical Research 151, VA Medical Center, 4300 West 7th Street, Little Rock, AR 72205.

Received 2/17/88. Revised 6/ 1/88. Accepted 7/19/88.

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