Characterization of sulfate transport in the hepatic endoplasmic reticulum.
The transport of sulfate ion across the endoplasmic reticulum membrane was investigated using rapid filtration and light scattering assays. We found a protein-mediated, bi-directional, low-affinity, and high-capacity, facilitative sulfate transport in rat liver microsomes, which could be inhibited by the prototypical anion transport inhibitor, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid. It was resistant to various phosphate transport inhibitors and was not influenced by high concentration of phosphate or pyrophosphate, which is contradictory to involvement of phosphate transporters. It was sensitive to S3483 that has been reported to inhibit the glucose 6-phosphate transporter (G6PT), but the weak competition between sulfate and glucose 6-phosphate did not confirm the participation of this transporter. Moreover, the comparison of the activity and S3483 sensitivity of sulfate transport in microsomes prepared from G6PT-overexpressing or wild type COS-7 cells did not show any significant difference. Our results indicate that sulfate fluxes in the endoplasmic reticulum are mediated by a novel, S3483-sensitive transport pathway(s).
Csala
Miklós
M
Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Endoplasmic Reticulum Research Group of The Hungarian Academy of Sciences, H-1444, Budapest, P.O. Box 260, Hungary.
Senesi
Silvia
S
Bánhegyi
Gábor
G
Mandl
József
J
Benedetti
Angelo
A
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology*; D019556:COS Cells; D002478:Cells, Cultured; D002850:Chromatography, Gel; D003509:Cyclohexanecarboxylic Acids / Q000378:metabolism; D011756:Diphosphates / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D019298:Glucose-6-Phosphate / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D010710:Phosphates / Q000494:pharmacology; D051381:Rats; D012542:Scattering, Radiation; D013431:Sulfates / Q000378:metabolism*; D013997:Time Factors
D003509:Cyclohexanecarboxylic Acids; D011756:Diphosphates; D026901:Membrane Transport Proteins; D010710:Phosphates; C113180:S 3483; D013431:Sulfates; D019298:Glucose-6-Phosphate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid