| Popis: |
The hexose transporter family, which mediates facilitated uptake in mammalian cells, consists of more than 10 members containing 12 membrane-spanning segments with a single N-glycosylation site. We previously demonstrated that glucose transporter 1 is organized into a raft-like detergent-resistant membrane domain but that glucose transporter 3 distributes to fluid membrane domains in nonpolarized mammalian cells. In this study, we further examined the structural basis responsible for the distribution by using a series of chimeric constructs. Glucose transporter 1 and glucose transporter 3 with a FLAG-tagged N-terminus were expressed in detergent-resistant membranes and non-detergent-resistant membranes of CHO-K1 cells, respectively. Replacement of either the C-terminal or N-terminal cytosolic portion of FLAG-tagged glucose transporter 1 and glucose transporter 3 did not affect the membrane distribution. However, a critical sorting signal may exist within the N-terminal half of the isoforms without affecting transport activity and its inhibition by cytochalasin B. Further shortening of these regions altered the critical distribution, suggesting that a large proportion or several parts of the intrinsic structure, including the N-terminus of each isoform, are involved in the regulation. |
