N-linked glycosylation is not required for Na+/glucose symport activity in LLC-PK1 cells

The role of N-linked glycosylation in Na+/glucose symporter function was investigated using LLC-PK1 cell cultures. Tunicamycin treatment did not inhibit Na(+)-dependent glucose transport or phlorizin binding activity assayed in intact LLC-PK1 cells. However apical membrane vesicles derived from tunicamycin-treated cells had no detectable Na(+)-dependent glucose transport activity but retained unchanged phlorizin binding to the symporter. These observations suggest that N-linked glycosylation is not required for transport function or insertion in the membrane in intact cells but may play a role in maintaining symporter transport activity in isolated membranes.