title: Hydroxylated serotonin and dopamine as substrates and inhibitors for human cytosolic SULT1A3.
abstract: Sulfation as catalyzed by the cytosolic sulfotransferases (SULTs) is known to play an important role in the regulation and homeostasis of monoamine neurotransmitters. The current study was designed to examine the occurrence of the sulfation of 7-hydroxyserotonin and 6-hydroxydopamine by human cytosolic SULTs and to investigate the inhibitory effects of these hydroxylated derivatives on the sulfation of their unhydroxylated counterparts, serotonin and dopamine. A systematic study using 11 known human cytosolic SULTs revealed SULT1A3 as the responsible enzyme for the sulfation of 7-hydroxyserotonin and 6-hydroxydopamine. The pH-dependence and kinetic constants of SULT1A3 with 7-hydroxyserotonin or 6-hydroxydopamine as substrate were determined. The inhibitory effects of 7-hydroxyserotonin and 6-hydroxydopamine on the sulfation of serotonin and dopamine were evaluated. Kinetic analyses indicated that the mechanism underlying the inhibition by these hydroxylated monoamine derivatives is of a competitive-type. Metabolic labeling experiments showed the generation and release of [(35) S]sulfated 7-hydroxyserotonin and [(35) S]sulfated 6-hydroxydopamine when SK-N-MC human neuroblastoma cells were labeled with [(35) S]sulfate in the presence of 7-hydroxyserotonin or 6-hydroxydopamine. Upon transfection of the cells with siRNAs targeted at SULT1A3, diminishment of the SULT1A3 protein and concomitantly the sulfating activity toward these hydroxylated monoamines was observed. Taken together, these results indicated clearly the involvement of sulfation in the metabolism of 7-hydroxyserotonin and 6-hydroxydopamine. By serving as substrates for SULT1A3, these hydroxylated monoamines may interfere with the homeostasis of endogenous serotonin and dopamine.
authors: Department of Pharmacology, College of Pharmacy, The University of Toledo, Toledo, Ohio, USA.
authors: Shin
authors: S
authors: Yasuda
authors: Ming-Yih
authors: MY
authors: Liu
authors: Masahito
authors: M
authors: Suiko
authors: Yoichi
authors: Y
authors: Sakakibara
authors: Ming-Cheh
authors: MC
authors: Liu
mesh_terms: D015116:5,7-Dihydroxytryptamine / Q000378:metabolism* / Q000494:pharmacology*; D015239:Arylsulfotransferase; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002855:Chromatography, Thin Layer; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology*; D004295:Dihydroxyphenylalanine / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D004791:Enzyme Inhibitors; D020868:Gene Silencing; D006801:Humans; D006900:Hydroxylation; D007700:Kinetics; D016627:Oxidopamine / Q000378:metabolism* / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism; D015238:Sulfotransferases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D013462:Sulfur Radioisotopes
chemical_list: D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D013462:Sulfur Radioisotopes; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D004295:Dihydroxyphenylalanine; D016627:Oxidopamine; D015238:Sulfotransferases; D015239:Arylsulfotransferase; C403170:monoamine-sulfating phenol sulfotransferase; D004298:Dopamine