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Regulation of hexose transport in L 8 myocytes by glucose: Possible sites of interaction
Author(s) -
Wertheimer Efrat,
Sasson Shlomo,
Cerasi Erol
Publication year - 1990
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041430217
Subject(s) - cycloheximide , hexose , glucose transporter , tunicamycin , glucose uptake , snf3 , membrane transport , biochemistry , myocyte , glycosylation , transporter , chemistry , carbohydrate metabolism , biology , protein biosynthesis , medicine , endocrinology , insulin , membrane , apoptosis , enzyme , unfolded protein response , gene
Previous work demonstrated that glucose controls its own transport rate in rat skeletal muscle: exposure to high glucose levels down‐regulates muscle hexose transport, while glucose withdrawal results in elevated transport rates ( J. Biol. Chem. 261:16827–;16833, 1986). The present study investigates the mechanism of this autoregulatory system. Preincubation of L 8 myocytes at 16 mM glucose reduced subsequent 2‐deoxy‐D‐glucose (dGlc) uptake by 40% within 3 h. Cyc‐loheximide (1 μM) mimicked the action of glucose; the effects of glucose and cycloheximide were not additive. At 50 μM, cycloheximide prevented the modulations of glucose transport induced by exposure of muscle cells to high or low glucose concentrations. Inhibition of glycosylation with tunicamycin A 1 reduced the basal dGlc uptake, but did not prevent its up‐regulation following glucose withdrawal. Inhibition of RNA synthesis by actinomycin D prevented the down‐regulatory effect of glucose. These results indicate that continuous protein synthesis and protein glycosylation are required for the maintenance of the steady‐state dGlc uptake. We suggest that glucose exerts its autoregulatory effect on hexose transport by modifying the incorporation of active glucose transporters into the plasma membrane rather than changing their rate of degradation. It is hypothesized that this effect is mediated by a non‐glycosylated protein involved in the translocation or activation of glucose transporters.