Characterization of glucose transport and glucose transporters in the human choriocarcinoma cell line, BeWo

In this study we have characterized 2-deoxyglucose (2DG) transport and hexose transporter expression in the human choriocarcinoma cell line, BeWo. 2DG uptake in BeWo cells displayed saturable kinetics (V-max, 29 +/- 1.5 nmol/min/mg protein; K-m, 1.5 +/- 0.02 mM) and was significantly inhibited in the presence of 2-deoxyglucose, mannose and 3-O-methyl glucose (all at a competing concentration of 30 mM) by up to 97 per cent, but not by galactose or fructose. Glucose uptake was not Na+-dependent, but was inhibited by cytochalasin B (by approx 85 per cent) indicating that hexose uptake was mediated via a facilitative glucose transport mechanism. Northern and immunoblot analyses revealed that BeWo cells expressed GLUT1 and GLUT5, but not GLUT2 or GLUT3. On immunoblots, GLUT1 migrated as a broad protein band on SDS-gels (average M-r of 55 kDa) and treatment with N-glycanase resulted in a significant shift in its electrophoretic mobility; the core protein migrating as a 40 kDa band indicating that the carrier was heavily glycosylated. GLUT5 was detected as a discrete 60 kDa band and like GLUT1, the observed immunoreactive signal was lost when using antiserum that had been pre-adsorbed with the antigenic peptide. Our findings indicate that BeWo cells express a facilitative glucose transport system with characteristics broadly similar to those reported in isolated human placental membrane vesicles and that they are likely to serve as a useful experimental system for studying the regulation of placental glucose transport and transporter expression. (C) 1999 Harcourt Publishers Ltd.