Substrate-dependent regulation of human arylamine N-acetyltransferase-1 in cultured cells

Butcher, NJ, Ilett, KF and Minchin, RF (2000) Substrate-dependent regulation of human arylamine N-acetyltransferase-1 in cultured cells. Molecular Pharmacology, 57 3: 468-473.

Author Butcher, NJ
Ilett, KF
Minchin, RF
Title Substrate-dependent regulation of human arylamine N-acetyltransferase-1 in cultured cells
Journal name Molecular Pharmacology   Check publisher's open access policy
ISSN 0026-895X
Publication date 2000-01-01
Year available 2000
Sub-type Article (original research)
Open Access Status Not yet assessed
Volume 57
Issue 3
Start page 468
End page 473
Total pages 6
Place of publication BETHESDA
Publisher AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS
Language eng
Abstract Arylamine N-acetyltransferase-1 (NAT1) is a polymorphically expressed enzyme that is widely distributed throughout the body. In the present study, we provide evidence for substrate-dependent regulation of this enzyme. Human peripheral blood mononuclear cells cultured in medium supplemented with p-aminobenzoic acid (PABA; 6 mu M) for 24 h showed a significant decrease (50-80%) in NAT1 activity. The loss of activity was concentration-dependent (EC50 similar to 2 mu M) and selective because PABA had no effect on the activity of constitutively expressed lactate dehydrogenase or aspartate aminotransferase. PABA also induced down-regulation of NAT1 activity in several human cell lines grown at confluence. Substrate-dependent downregulation was not restricted to PABA. Addition of other NAT1 substrates, such as p-aminosalicylic acid, ethyl-p-aminobenzoate, or p-aminophenol to peripheral blood mononuclear cells in culture also resulted in significant (P < .05) decreases in NAT1 activity. However, addition of the NAT2-selective substrates sulfamethazine, dapsone, or procainamide did not alter NAT1 activity. Western blot analysis using a NAT1-specific antibody showed that the loss of NAT1 activity was associated with a parallel reduction in the amount of NAT1 protein (r(2) = 0.95). Arylamines that did not decrease NAT1 activity did not alter NAT1 protein levels. Semiquantitative reverse transcriptase polymerase chain reaction of mRNA isolated from treated and untreated cells revealed no effect of PABA on NAT1 mRNA levels. We conclude that NAT1 can be down-regulated by arylamines that are themselves NAT1 substrates. Because NAT1 is involved in the detoxification/activation of various drugs and carcinogens, substrate-dependent regulation may have important consequences with regard to drug toxicity and cancer risk.
Keyword Pharmacology & Pharmacy
N-acetyltransferase Nat1
Metabolic-activation
Folate Metabolism
Human-liver
Acetylation
Protein
Expression
Bladder
Alleles
Colon
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biomedical Sciences Publications
 
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Created: Mon, 13 Aug 2007, 21:37:18 EST