Sulfation by human lung fibroblasts: SO4(2-) and sulfur-containing amino acids as sources for macromolecular sulfation.
Studies were carried out in human lung fibroblasts (IMR-90) to investigate 1) the relative contribution of two extracellular pools, inorganic sulfate and sulfur-containing amino acids, to the intracellular fraction precipitable by trichloroacetic acid and 2) the possibility that the transport of these sulfur-containing substrates at the plasma membrane may be a limiting step for macromolecular sulfation. Our studies indicate that the ability to use SO4(2-) released by intracellular catabolism of the sulfur-containing amino acid L-cysteine differs from one cell system to another. In contrast to smooth muscle cells, in the human lung fibroblast, L-cysteine contributes significantly to the intercellular pool of SO4(2-) used for sulfation at extracellular [SO4(2-)] less than 100 microM. However, under physiological conditions with respect to SO4(2-) ([SO4(2-)]0 = 300 microM), L-cysteine does not contribute greater than 30% of the sulfate incorporated into the cellular fraction. Taurine (2-aminoethanesulfonic acid) inhibits SO4(2-) incorporation into the cell-associated macromolecular fraction. However, results suggest that the effect is not due to either SO4(2-) released by its catabolism or to an effect on SO4(2-) transport into the cell. The fact that the transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid inhibits sulfate incorporation indicates that carrier-mediated sulfate transport at the cellular plasma membrane may be a limiting step for sulfate incorporation. In conclusion, under physiological conditions with respect to SO4(2-), inorganic sulfate is a major source of sulfate for sulfation in human lung fibroblasts and macromolecular sulfation may be limited by its transport into the cells.
Elgavish
A
A
Department of Comparative Medicine, University of Alabama, Birmingham 35294.
Meezan
E
E
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D003545:Cysteine / Q000187:drug effects / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005944:Glucosamine / Q000378:metabolism; D006025:Glycosaminoglycans / Q000096:biosynthesis; D006801:Humans; D007700:Kinetics; D008168:Lung; D013431:Sulfates / Q000378:metabolism*; D013654:Taurine / Q000494:pharmacology; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000494:pharmacology
D006025:Glycosaminoglycans; D013431:Sulfates; C012036:sodium sulfate; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D013654:Taurine; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D003545:Cysteine; D005944:Glucosamine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid