Professor Mike Coughtrie

Biology and Function of Drug Conjugating Enzymes and Transporters

We are continuously exposed to a host of toxic or potentially toxic chemicals from our environment, both internal and external, and this represents a serious threat to health. To combat this threat, we have evolved a complex and effective chemical defence system comprising, among other components, a series of enzyme and transporter families whose main function is generally accepted to be the detoxification and elimination of xenobiotics and endogenous toxins. Our laboratory seeks to understand the normal cellular function of a number of these important proteins, and the functional consequences of disruption of this function by genetic and other factors.

Sulfation

Our interest is in the enzyme families that participate in the addition and removal of sulfate to a host of endogenous and environmental chemicals - the sulfotransferases (SULTs) and sulfatases, respectively. Sulfation has a well-established role in drug metabolism and chemical defence, but it is in the area of steroid and thyroid hormone and neurotransmitter homeostasis that the most exciting possibilities lie, since reversible sulfation can provide an exquisitely sensitive and specific means of regulating the biological activity of these compounds in target and non-target cells. This is particularly relevant in breast cancer, where we are investigating the role of steroid sulfatase. More recently, in collaboration with Professor Sylvie Fournel-Gigleux (Nancy, France), we have been working on the epigenetic regulation of the sulfotransferases involved the synthesis of glycosaminoglycans in human cancers.

Glucuronidation

A major pathway of metabolism for many drugs, glucuronidation is catalysed by members of the UDP-glucuronosyltransferase (UGT) enzyme family. We are interested in the functional consequences of common genetic variants of key drug metabolising UGTs, and have applied novel expression systems to study these in vitro, and quantify expression in human tissues. We are also interested in biocatalysis relevant to glucuronidation.

Transport

The proteins that govern entry and exit of xenobiotics and their metabolites from cells and subcellular compartments play a key role in drug handling. We recently discovered the identity of the transporters that control the entry of the glucuronidation co-substrate UDP-glucuronic acid into the endoplasmic reticulum. We are presently developing novel methods to identify and quantify expression of a variety of transporters, including members of the BCRP, MRP and MDR families in human tissues.

Work is currently supported by the Engineering and Physical Sciences Research Council, The Biotechnology & Biological Sciences Research Council, The Royal Society, and we have active collaborations with a number of industrial partners including Pfizer and Novacta Biosystems.

Kanika Choughule (PhD Student)

Alison Milne (Senior Scientific Officer)

Sylvie Fournel-Gigleux (Visiting Professor)

Chris Jones (PhD Student)

Stanley EL, Hume R, Coughtrie MWH. Expression profiling of human fetal cytosolic sulfotransferases involved in steroid and thyroid hormone metabolism and in detoxification. Mol Cell Endocrinol 240, 32-42 (2005).

Burchell B, Lockley DJ, Coughtrie MWH. Substrate specificity of human hepatic UDP-glucuronosyltransferases. Methods Enzymol. 400, 46- 57 (2005).

Kobayashi T, Coughtrie MWH, Burchell B. Molecular and functional characterisation of microsomal UDP-glucuronic acid uptake by members of the nucleotide sugar transporter (NST) family. Biochem J 400, 281-289 (2006).

Riches Z, Bloomer JC, Coughtrie MWH. Comparison of 2-aminophenol and 4-nitrophenol as in vitro probe substrates for the major human hepatic sulfotransferase, SULT1A1, demonstrates improved selectivity with 2-aminophenol. Biochem Pharmacol 74, 352-358 (2007).

Itäaho K, Alakurtti S, Yli-Kauhaluoma J, Taskinen J, Coughtrie MWH and Kostiainen R. Regioselective sulfonation of dopamine by SULT1A3 in vitro provides a molecular explanation for the preponderance of dopamine-3-O-sulfate in human blood circulation. Biochem Pharmacol 74, 504-510 (2007).

Fondeur-Gelinotte M, Lattard V, Gulberti S, Oriol R, Mulliert G, Coughtrie MWH, Magdalou J, Netter P, Ouzzine M and Fournel-Gigleux S. Molecular basis for acceptor substrate specificity of the human ÿ,3-glucuronosyltransferases GlcAT-I and GlcAT-P involved in glycosaminoglycan and HNK-1 carbohydrate epitope biosynthesis, respectively. Glycobiology 17, 857-867 (2007).