Angewandte
Chemie
DOI: 10.1002/anie.201306295
Enzyme Inhibition
Hot Paper
Development of an Activity-Based Probe and In Silico Design Reveal
Highly Selective Inhibitors for Diacylglycerol Lipase-a in Brain**
Marc P. Baggelaar, Freek J. Janssen, Annelot C. M. van Esbroeck, Hans den Dulk,
Marco Allarꢀ, Sascha Hoogendoorn, Ross McGuire, Bogdan I. Florea, Nico Meeuwenoord,
Hans van den Elst, Gijsbert A. van der Marel, Jaap Brouwer, Vincenzo Di Marzo,
Herman S. Overkleeft, and Mario van der Stelt*
Diacylglycerol lipase-a (DAGL-a) is an intracellular, multi-
domain protein responsible for the formation of the endo-
cannabinoid 2-arachidonoylglycerol (2-AG) in the central
nervous system.[1] 2-AG is an endogenous signaling lipid that
interacts with the cannabinoid CB1 and CB2 receptors.[2]
Little is known about the regulation of its biosynthetic
pathway and it is largely unclear to what extent 2-AG is
responsible for distinct cannabinoid CB1 receptor mediated
biological processes. Selective inhibitors of DAGL-a may
contribute to a more fundamental understanding of the
physiological role of 2-AG and may serve as potential drug
candidates for the treatment of obesity and neurodegener-
ative diseases.[3] Currently, there are no selective inhibitors
and activity-based probes available for the study of
DAGL-a.[4]
various physiological functions.[5] Fluorophosphonate (FP)-
based probes are routinely employed in competitive activity-
based protein profiling (ABPP) experiments to determine the
selectivity of serine hydrolase inhibitors in complex pro-
teomes. DAGL-a, however, does not react with these activity-
based probes.[6] Therefore, a new probe that can label native
DAGL-a would be of value for studying the potency and
selectivity of novel DAGL-a inhibitors in brain proteomes.
Here we present a strategy that combines a knowledge-based
in silico design approach and the development of a novel
activity-based probe (ABP), based on the nonselective
DAGL-a inhibitor tetrahydrolipstatin (THL; also known as
Orlistat, a drug used for the treatment of obesity). This
strategy resulted in the rapid identification of DAGL-a
inhibitors with a new chemotype and high selectivity in the
brain proteome.
To identify novel DAGL-a inhibitors, we built a pharma-
cophore model based on THL using Discovery Studio
Software Suite from Accelrys. Since THL can assume many
different conformations, we searched the protein crystallo-
graphic database for crystal structures with a bioactive
conformation for THL. A cocrystal structure of THL with
fatty acid synthase (pdb-code: 2PX6) was identified (Fig-
ure 1A)[7] that contains the same Ser-His-Asp catalytic triad
and typical a/b hydrolase fold motif as DAGL-a. In this
cocrystal structure, the nucleophilic Ser of the enzyme is
covalently attached to the carbonyl moiety of the lactone. We
reconstituted the ester to form the b-lactone to recover the
active warhead of THL. After optimization of the geometry
of the lactone, the resulting conformation was used to
generate two pharmacophore models (Figure 1B,C).
The essential features of both models are 1) a hydrogen-
bond acceptor mimicking the carbonyl from the b-lactone;
2) hydrophobic hot spots corresponding to the lipophilic tails
of THL; 3) a hydrogen-bond acceptor positioned at the sn-2
ester functionality; and 4) exclusion volumes representing the
space occupied by the nucleophilic Ser and the backbone
oxyanion hole residues in the active site of DAGL-a. Model 2
contained an additional hydrogen-bond donor feature
derived from the leucinyl formamide moiety of THL. Using
these models, we virtually screened a set of commercially
available lipase inhibitors, which were mainly selected for
their reactivity towards enzymes involved in endocannabi-
noid signaling (Table S1 in the Supporting Information).
Analysis of the docking results revealed that two compounds
ranked in the top five of both models, LEI103 (1) and LEI104
The identification of selective DAGL-a inhibitors is
hampered by a lack of structural knowledge of the target,
and
a lack of assays that make use of endogenous
DAGL-a activity in proteomes. No crystal structures are
available and no homology models have been reported to aid
hit identification and to guide optimization of the inhibitors.
Determination of the selectivity of the inhibitors in native
tissues is important because DAGL-a belongs to the serine
hydrolase family, which contains more than 200 members with
[*] M. Sc. M. P. Baggelaar, M. Sc. F. J. Janssen, A. C. M. van Esbroeck,
M. Sc. S. Hoogendoorn, Dr. B. I. Florea, Ing. N. Meeuwenoord,
Ing. H. van den Elst, Prof. Dr. G. A. van der Marel,
Prof. Dr. H. S. Overkleeft, Dr. M. van der Stelt
Dept. of Bio-organic Synthesis, Leiden University
Einsteinweg 55, 2333 CC Leiden (The Netherlands)
E-mail: m.van.der.stelt@chem.leidenuniv.nl
M. Sc. M. Allarꢀ, Prof. Dr. V. Di Marzo
Endocannabinoid Research Group
Institute of Biomolecular Chemistry, C.N.R.
Via Campi Flegrei 34, 80078, Pozzuoli (Italy)
Ing. H. den Dulk, Prof. Dr. J. Brouwer
Dept. of Molecular Genetics, Leiden University
Einsteinweg 55, 2333 CC Leiden (The Netherlands)
Dr. R. McGuire
Bioaxis Research
Bergse Heihoek 56, Berghem (The Netherlands)
[**] We would like to thank Prof. Dr. P. Doherty (King’s College London
(UK)) for his kind gift of wild type and DAGL-a knockout mouse
brains.
Supporting information for this article is available on the WWW
Angew. Chem. Int. Ed. 2013, 52, 1 – 6
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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