HUMAN DEHYDROEPIANDROSTERONE SULFOTRANSFERASE PHARMACOGENETICS - QUANTITATIVE WESTERN ANALYSIS AND GENE SEQUENCE POLYMORPHISMS

Dehydroepiandrosterone sulfotransferase (DHEA ST) catalyzes the sulfat ion of DHEA and other hydroxysteroids. DHEA ST enzymatic activity in i ndividual human liver biopsy samples has been shown to vary over a fiv e-fold range, and frequency distribution histograms are bimodal, with approximately 25% of subjects included in a high activity subgroup. We set out to characterize the molecular basis for variation in human li ver DHEA ST activity. The first step involved performing quantitative Western analysis of cytosol preparations from 92 human liver samples t hat had been phenotyped with regard to level of DHEA ST enzymatic acti vity. There was a highly significant correlation (r(s) = 0.635, P < 0. 0001) between levels of DHEA ST activity and immunoreactive protein. W e next attempted to determine whether the expression of DHEA ST might be controlled, in part, by a genetic polymorphism. DNA was isolated fr om three ''low'' and three ''high'' DHEA ST activity liver samples. Ex ons and the 5'-flanking region of the DHEA ST gene (STD) were amplifie d for each of these samples with the polymerase chain reaction (PCR). When compared with ''wild type'' STD sequence, some of the samples con tained a T --> C transition at DHEA ST cDNA nucleotide 170, located wi thin exon 2, resulting in a Met 57 --> Thr change in amino acid. Other samples contained an A --> T transversion at nucleotide 557 within ST D exon 4 that resulted in a Glu 186 --> Val change. STD exons 2 and 4 were then sequenced for DNA isolated from an additional 87 liver sampl es that had been phenotyped with regard to level of DHEA ST enzymatic activity. The allele frequency for the exon 2 polymorphism in these sa mples was 0.027, whereas that for the exon 4 polymorphism was 0.038, b ut neither polymorphism was systematically related to the level of enz yme activity in these samples. Transient expression in COS-1 cells of cDNA that contained the nucleotide 170 and 557 polymorphisms, either s eparately or together, resulted in decreased expression of both DHEA S T enzymatic activity and level of immunoreactive protein, but only whe n the nucleotide 557 variant was present. Identification of common gen etic polymorphisms within STD will now make it possible to test the hy pothesis that those polymorphisms might alter in vivo expression and/o r function of this important human steroid-metabolizing enzyme. Copyri ght (C) 1996 Elsevier Science Ltd.