In vitro modulation of UDP-glc-glucosiltransferase by progesterone. Study of the influence on the synthesis of asymmetric antibodies.

PRADOS MB, LITWIN S., GENTILE T., CARAMELO J., MIRANDA S.

Rio de Janeiro, Brasil

Congreso; 13th International Congress of Immunology; 2007

International Union of Immunology Societies

The role of UDP-glc-glucosiltransferase (GT) in the quality control of secretor proteins has been ascertained. However, its physiological relevance remains unknown. Two GT isoformes with different activity levels were described in human (HUGT1 and HUGT2), such isoformes were not reported in mouse. Here we studied the influence of progesterone (P4) on GT expression and activity, and on the synthesis of asymmetric antibodies (AAb) in a murine hybridome cell culture able to secrete symmetric and AAb. The cells were incubated with P4 (0, 10-5, 10-6, 10-8, 10-9 M) for 48 hs. GT activity was determined as the incorporation of [14C]-Glc to denatured thyroglobulin by cell microsomes. GT expression was measured by western blot using an anti-rat policlonal antibody, which proved to recognise HUGT1 but not HUGT2. AAb rate was calculated by ELISA. GT activity in control cultures was 1.20 cpm/mg protein. When P4 was added at 10-6M, 10-8M and 10-9M the expression levels and activity were similar between each other (0.90, 0.77 and 0.96 cpm/mg protein; p>0.05). On the contrary, P4 10-5 M induced a significant increase in GT activity (1.43 cpm/mg protein, p<0.05 respect the other doses) and a decrease in the GT expression (-30 %; p<0,05). AAb rates observed for control, P4 10-5M, 10-6M, 10-8M and 10-9M were 36%, 30%, 15% (p<0.01), 36% and 29% respectively.These results are not conclusive about the participation of GT on the synthesis of AAb, but the discrepancies observed between GT expression and activity with P4 10-5M could suggest that P4 might regulate a switch of GT isoforms with different functions.