Human cytosolic sulfotransferase 2B1: isoform expression, tissue specificity and subcellular localization

Area of Science:

• Biochemistry
• Molecular Biology
• Endocrinology

Background:

• Sulfation is a critical Phase II conjugation reaction in human steroid synthesis and metabolism.
• The sulfotransferase (SULT) 2B1 gene encodes two isoforms, SULT2B1a and SULT2B1b, differing in their initial exons.
• While both isoforms' messages are found in human tissues, only SULT2B1b protein has been detected.

Purpose of the Study:

• To investigate the characteristics and cellular localization of SULT2B1b.
• To explore the role of SULT2B1b in steroid metabolism and cellular signaling.
• To understand the regulation of SULT2B1b nuclear localization.

Main Methods:

• Analysis of SULT2B1 gene transcription and protein expression.
• Cellular localization studies using human cell lines (e.g., BeWo placental choriocarcinoma cells).
• Investigation of factors influencing nuclear localization, such as 3'-extension and post-translational modifications (serine phosphorylation).

Main Results:

• SULT2B1b protein is localized in the cytosol and/or nuclei.
• A unique 3'-extension of SULT2B1b is necessary for its nuclear localization.
• Nuclear localization is enhanced by forskolin treatment and involves serine phosphorylation.
• SULT2B1b demonstrates selectivity for sulfating 3beta-hydroxysteroids like dehydroepiandrosterone and pregnenolone, and potentially cholesterol in human skin.

Conclusions:

• SULT2B1b's substrate specificity, subcellular localization, and tissue distribution suggest a role in modulating cellular responses to adrenal androgens.
• It may achieve this by directly inactivating androgens or by inhibiting their conversion to more potent estrogens and androgens.
• Further research into SULT2B1b function could elucidate mechanisms of steroid hormone regulation.