Kinetic characteristics and regulation of hexose transport in a galactokinase-negative Chinese hamster fibroblast cell line: A good model for studies on sugar transport in cultured mammalian cells
✍ Scribed by Ralph J. Germinario; Tannirkulam M. Lakshmi; Jean-Paul Thirion
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 574 KB
- Volume
- 138
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
We report the kinetic charactcristirs for D-galactose, 2-deoxy-D-glucose and 3-0-methyl-D-glucose transport in a galactokinase null-allele mutant of a Chinese hamster V79 cell line. GalKl cells exhibited a K, , and V, , , , , for D-galactose, 2-deoxy-D-glucose, and 3-0-methyl-D-glucose transport of 8.6 ? 2.6 mM and 26.1 2 7.2 n n i o h g phiin, 4.1 k 1.2 m M and 40.3 % 9.5 nmol/mg p/min, and 7.01 ? .85 m M and 11.6 ? 4.8 nmol/mg p/30 s, respectively. Nonsaturable hexose uptake was determined using cytochalasin R inhibition of galactose uptake (89.6 -i-3.7% of galactose uptake was cytochalasin B inhibitable) and L-glucose uptake ( 7 ~5 % of the galactose uptake). U-Galactose was not metabolized and effluxed rapidly from preloaded cells. The Kls for the inhibition of D-galactose transport were 4.5 ? 2.5 m M for D-glucose, 7.0 2 2.0 m M for 2-deoxy-D-glucose, 6 mM for 2-deoxy-D-galactose and 6.0 2 0.6 m M for 3-0-methyl-D-glucose. This indicates the operation of a single common carrier.
The hexose transport rate decreased SO-hO% after 24 h srrum deprivation. Addition of insulin was shown to increase hexose transport (more than twofold) in serum-deprived cells. Hexose transport rates increased substantially in glucosedeprived, D-fructose-or D-galactose-fed cells as compared to glucose-fed cells. Since CalKl does not metabolize galactose, the hexose transport increases induced by feeding cells galactose suggest that carrier interaction with ligand is not a significant factor in transport regulation in GalKI. The kinetic and regulatory characteristics of D-galactose trmsport in the GalKl cell line indicate that this sy3tem is a good model to study sugar transport from a mechanistic and regulatory point of view.