A role for sulfation-desulfation in the uptake of bisphenol a into breast tumor cells.

Bisphenol A (BPA) is a widely used plasticizer whose estrogenic properties may impact hormone-responsive disorders and fetal development. In vivo, BPA appears to have greater activity than is suggested by its estrogen receptor (ER) binding affinity. This may be a result of BPA sulfation/desulfation providing a pathway for selective uptake into hormone-responsive cells. BPA is a substrate for estrogen sulfotransferase, and bisphenol A sulfate (BPAS) and disulfate are substrates for estrone sulfatase. Although the sulfated xenobiotics bind poorly to the ER, both stimulated the growth of receptor-positive breast tumor cells. Treatment of MCF-7 cells with BPAS leads to desulfation and uptake of BPA. No BPAS is found inside the cells. These findings suggest a mechanism for the selective uptake of BPA into cells expressing estrone sulfatase. Therefore, sulfation may increase the estrogenic potential of xenobiotics.

A 96-well dot-blot assay for carbohydrate sulfotransferases.

Here we describe an efficient dot-blot assay for high-throughput screening of two enzymes, heparan sulfate N-deacetylase/N-sulfotransferase (NDST-1) and high-endothelial cell GlcNAc-6-sulfotransferase (HEC-GlcNAc-6-ST). The assay proceeds by transfer of 35S-labeled sulfate from [35S]-3(')-phosphoadenosine-5(')-phosphosulfate (PAPS) to the free amino groups of de-N-sulfated heparin (NDST-1), or the 6-hydroxyl groups of N-acetylglucosamine residues linked to a polyacrylamide scaffold (HEC-GlcNAc-6-ST). The 35S-labeled products are then captured on an appropriate membrane, taking advantage of their polymeric architecture. In one step, 35S-labeled by-products are then eluted from the membrane, leaving spatially separated 35S-labeled product "dots" for subsequent quantification. This assay allows for direct product detection on the membrane, obviating excessive washing and elution steps endemic to other assays. The assay was validated by measuring K(M) values for PAPS and K(I) values for PAP, the product of sulfuryl transfer. The assay method should be useful for inhibitor screens for both enzymes. In addition, the general assay architecture should be readily applicable to high-throughput screens of other carbohydrate sulfotransferases.

Synthesis of a bisubstrate analogue targeting estrogen sulfotransferase.

Sulfotransferases catalyze the transfer of a sulfuryl group from the eukaryotic sulfate donor 3'-phosphoadenosine 5'-phosphosulfate to an acceptor biomolecule. Sulfotransferases have been linked with several disease states, prompting our investigation of specific sulfotransferase inhibitors. Presented herein is the synthesis and evaluation of a bisubstrate analogue designed to inhibit estrogen sulfotransferase. The synthesis utilizes a novel, orthogonally protected 3'-phosphoadenosine 5'-phosphate (PAP) derivative allowing the selective functionalization of the 5'-phosphate with a sulfate acceptor mimic. Kinetic studies revealed significant inhibitory activity and provide guidance for improved inhibitor design.

Tyrosylprotein sulfotransferase inhibitors generated by combinatorial target-guided ligand assembly.

Tyrosylprotein sulfotransferases (TPSTs) catalyze the sulfation of tyrosine residues within secreted and membrane-bound proteins. The modification modulates protein-protein interactions in the extracellular environment. Here we use combinatorial target-guided ligand assembly to discover the first known inhibitors of human TPST-2.