Design and synthesis of sulfamoyl benzoic acid analogues with subnanomolar agonist activity specific to the LPA2 receptor

Article abstract of DOI:10.1021/jm5007116

Lysophosphatidic acid (LPA) is a growth factor-like mediator and a ligand for multiple GPCR. The LPA₂ GPCR mediates antiapoptotic and mucosal barrier-protective effects in the gut. We synthesized sulfamoyl benzoic acid (SBA) analogues that are the first specific agonists of LPA₂, some with subnanomolar activity. We developed an experimental SAR that is supported and rationalized by computational docking analysis of the SBA compounds into the LPA₂ ligand-binding pocket.

Full text of DOI:10.1021/jm5007116

Brief Article
pubs.acs.org/jmc
Open Access on 08/06/2015
Design and Synthesis of Sulfamoyl Benzoic Acid Analogues with
Subnanomolar Agonist Activity Specific to the LPA2 Receptor
Renukadevi Patil,†,∥ James I. Fells,‡,∥ Erzsebet Szabo,‡ Keng G. Lim,‡ Derek D. Norman,‡ Andrea Balogh,‡
́
́
Shivaputra Patil,† Jur Strobos,§ Duane D. Miller,† and Gabor J. Tigyi*,‡
́
†Departments of Pharmaceutical Sciences and Physiology, The University of Tennessee Health Science Center, Memphis,
‡
Tennessee 894 Union Avenue 38163 United States
§RxBio, Inc., Johnson City, Tennessee 37604 United States
S
* Supporting Information
ABSTRACT: Lysophosphatidic acid (LPA) is a growth factor-like mediator and a
ligand for multiple GPCR. The LPA2 GPCR mediates antiapoptotic and mucosal
barrier-protective effects in the gut. We synthesized sulfamoyl benzoic acid (SBA)
analogues that are the first specific agonists of LPA2, some with subnanomolar
activity. We developed an experimental SAR that is supported and rationalized by
computational docking analysis of the SBA compounds into the LPA2 ligand-binding
pocket.
receptors. LPA GPCR activate antiapoptotic kinase pathways,
inhibit apoptosis, promote cell regeneration, and augment DNA
repair, altogether.1−4 Our group has been interested in
developing LPA analogues for the attenuation of programmed
cell death elicited by radiation and chemotherapeutic
agents.2,5−7 In the course of our studies, we discovered
octadecenyl thiophosphate (OTP) (2, Figure 1), a synthetic
analogue of LPA, which showed strong radioprotective action
by rescuing cells from apoptosis and mice irradiated with lethal
doses of γ-irradiation.7 Although OTP is highly effective in
protecting animals from radiation injury, it activates multiple
LPA GPCRs, including LPA1 that has been linked to cause
apoptosis via anoikis.8,9 Recently, our group identified novel
nonlipid compounds that are selective, although not specific,
agonists of LPA2 and also inhibit LPA3.10 Among these nonlipid
compounds, GRI977143 (3, Figure 1), although much less
potent than LPA, nevertheless showed antiapoptotic efficacy in
cell-based models of apoptosis and it was modestly efficacious
against radiation-induced apoptosis in mice suffering from the
acute hematopoietic radiation syndrome.10 In continuation of
this line of research, we designed and synthesized sulfamoyl
benzoic acid (SBA) analogues of 3 by isoteric replacement of
−S− group with −NH-SO2 using a medicinal chemistry
approach guided by computational modeling.11,12 All 14 new
SBA analogues were tested for agonist and antagonist activity at
the LPA1/2/3/4/5 GPCR. We found several nonlipid specific
INTRODUCTION
■
Exposure to direct ionizing radiation can result in programmed
cell death due to the accompanying DNA damage.
Lysophosphatidic acid (LPA, 1-acyl-2-hydroxy-sn-3-glycero-
phosphate) (1, Figure 1) is a growth factor-like lipid mediator
with antiapoptotic actions elicited via a set of G protein coupled
Figure 1. Chemical structures of LPA (1), OTP (2), GRI977143 (3),
and SBA analogues.
Received: May 8, 2014
© XXXX American Chemical Society
A
dx.doi.org/10.1021/jm5007116 | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Brief Article
agonist of LPA2, one of which is 5-chloro-2-(N-(4-(1,3-dioxo-
1H-benzo[de]isoquinolin-2(3H)-yl)butyl)sulfamoyl)benzoic
acid (11d) (Scheme 4), with picomolar activity (EC50 = 5.06 ×
10−3 3.73 × 10−3 nM vs LPA 18:1; EC50 = 1.40 0.51 nM)
(Figure 2).
Scheme 2. Synthesis of Tail Group Modified SBA Analogues
(Compounds 7a,b)
carboxylic acid 1,1-dioxide (21) produced 2-(4-(1,3-dioxo-1H-
benzo[de]isoquinolin-2(3H)-yl)butyl)-3-oxo-2,3-dihydrobenzo-
[d]isothiazole-6-carboxylic acid 1,1-dioxide (9), which was then
treated with aqueous 1N NaOH to procure the desired
compound 2-(N-(4-(1,3-dioxo-1H-benzo[de]isoquinolin-
2(3H)-yl)butyl)sulfamoyl)terephthalic acid (10) (Scheme 3).
Figure 2. Fura-2AM Ca2+ assay of 11d versus LPA 18:1. Fura-2AM-
loaded LPA2 DKO MEF cells (closed symbols) or empty vector DKO
MEF cells (open symbols) were treated with LPA 18:1 (circles) or
11d (squares).
RESULTS AND DISCUSSION
■
Scheme 3. Synthesis of Head Group Modified SBA
Analogues (Compounds 8−10)
The synthesis of new novel SBA analogues, compounds 4−6,
7a−b, 8a−c, 9−10, and 11a−d, is outlined in Schemes 1−4,
respectively.
2-(Bromoalkyl)benzo[de]isoquinoline-1,3-dione (15a−c)
was obtained in high yield following a similar approach of
that already reported procedure.13 Compound 15a−c was
reacted with 2-sulfamoylbenzoic acid ethyl ester (16) using
K2CO3 in DMF to get compounds 4−6 in moderate yield
(Scheme 1). 2-[4-(1,3-Dioxo-1,3-dihydroisoindol-2-yl)-
Scheme 1. Synthesis of Carbon Linker Modified SBA
Analogues (Compounds 4−6)
N-Butylamino-1,8-naphthalimide (22)14 was coupled with
substituted sulfonyl chloride 23a−e using triethylamine in THF
to furnish corresponding ester derivatives (12a−e). Upon
treatment of compound 12b−c with LiOH in THF−water
(1:1) and compound 12d−e with K2CO3 in DMF afforded the
final acid derivatives 11a−b and 11c−d, respectively, in
moderate to quantitative yield (Scheme 4).
LPA receptor activation leads to a transient mobilization of
Ca2+ that can be quantified by measuring the fluorescence of
the indicator dye Fura-2AM. All compounds were tested using
cell lines established previously to overexpress a single LPA
GPCR subtype.10,11 For the human LPA1, LPA2, and LPA3
GPCR, we used mouse embryonic fibroblasts (MEF) derived
from LPA1xLPA2 double knockout mice (DKO) that lack
butylsulfamoyl]benzoic acid (7a) and 2-(N-(4-(2,3-dioxoindo-
lin-1-yl)butyl)sulfamoyl)benzoic acid (7b) were synthesized by
the reaction of commercially available 2-(3-bromobutyl)-
isoindole-1,3-dione (17) and 1-(4-bromobutyl)indoline-2,3-
dione (19) (which was prepared from 14b and isatin 18)
using 16, respectively (Scheme 2).
2-(N-(4-(1,3-Dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)-
butyl)sulfamoyl)-substituted benzoic acid (8a−c) was accom-
plished by the reaction of 15b and substituted benzo[d]-
isothiazol-3(2H)-one-1,1-dioxides (20a−c) in the presence of
K2CO3 and DMF under reflux conditions in moderate yield.
Reaction of 15b with 3-oxo-2,3-dihydrobenzo[d]isothiazole-6-
B
dx.doi.org/10.1021/jm5007116 | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Brief Article
scaffolds based on 3 were flexibly docked into the LPA2
homology model10,11 and first ranked by lowest energy docked
score. Each scaffold was then ranked based on the protein−
ligand interaction fingerprint, and a final ranking was
constructed based on visual inspection of pharmacophore
match. Using this strategy in combination with perceived ease
of synthesis, 2-(N-(3-(1,3-dioxo-1H-benzo[de]isoquinolin-
2(3H)-yl)propyl)sulfamoyl)benzoic acid (4) was selected.
Compound 4 had virtually identical overlay with respect to
the shape of 3 where sulfur was replaced by a sulfamoyl moiety
(Figure 1). Molecular modeling studies comparing compounds
3 and 4 suggested that the improved potency and selectivity of
compound 4 was attributed to the increased binding affinity of
compound 4 (−8.53 kcal/mol) compared to compound 3
(−7.94 kcal/mol). While both compounds can adopt similar
conformations in the binding pocket, compound 4 has a higher
conformation strain at 12.39 kcal/mol than compound 3 at 4.32
kcal/mol (Figure 3A). The pharmacological characterization of
compound 4 at LPA2 showed that, in spite of its low potency
(EC50 LPA2 ∼ 2 μM), it was a specific agonist of LPA2 without
activating or inhibiting LPA1/3/4/5 receptors. Of note is that,
unlike GRI977143, compound 4 lacked LPA3 antagonist
activity up to 10 μM, the highest concentration tested (Table
1). Therefore, this scaffold 4 was deemed an optimal template
for guiding lead optimization medicinal chemistry. Medicinal
chemistry focused SAR to increase the potency by synthesizing
derivatives of compound 4 by modifying at three target regions:
the head group, chain linker, and tail group (Figure 1). We
docked and evaluated the chain linker of compound 4 by
increasing the carbon numbers to four carbon (compound 5)
and five carbon (compound 6) linkers, which are similar in
length to the high-potency natural ligand LPA 18:1 of the
LPA2. Computational models of the docked linker analogues
predicted the overall length of compounds of these analogues at
14, 15, and 16 Å, respectively. Pharmacological characterization
of these three compounds 4, 5, and 6 showed that compound 5
Scheme 4. Synthesis of Head Group Modified SBA
Analogues (Compounds 11a−d)
endogenous LPA3 expression and do not respond to LPA with
Ca2+ transients (for assay details and the LPA4 and LPA5 cells,
see the Supporting Information). The compounds were
evaluated for agonist and antagonist activity (Table 1). For
agonists compounds, their dose−response was compared to
that elicited by LPA 18:1 using a FLEX-Station III robotic plate
reader as described in our previous publication.10
We embarked on a scaffold derivatization approach steered
by structure-based pharmacophore design. Studies were
initiated with GRI977143 (3) as a template scaffold with the
aim of achieving LPA2 subtype agonist specificity by eliminating
LPA3 antagonist activity and improving its potency through
molecular modifications. Our approach was to prioritize the
scaffold variants through several iterative steps. Ten different
Table 1. LPA Receptor Ligand Properties of Sulfamoyl Benzoic Acid (SBA) Analogues
c
LPA2
EC50 (μM)
LPA1
LPA3
LPA4
LPA5
vector
compd
Emax (%) EC50 (μM) Emax (%) EC50 (μM) Emax (%) EC50 (μM) Emax (%) EC50 (μM) Emax (%) EC50 (μM) Emax (%)
LPA 18:1
0.002
3.30
100
75
0.35
100
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
0.83
100
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
0.26
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
100
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
0.51
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
100
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
a
b
GRI-977143
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
4
2.16
100
100
100
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
5
0.11
6
1.42
7a
7b
8a
8b
8c
9
NE
NE
NE
NE
NE
0.05
100
104.15
100
NE
0.06
3.60
10
11a
11b
11c
11d
NE
NE
NE
NE
NE
1.5 × 10−4
5.06 × 10−6
119
124
a
b
NE: no detectable effect up to 10 μM concentration. GRI-977143 has no agonist activity at LPA3, however, it is an antagonist with an IC50
c
concentration of 6.6. μM against LPA 18:1 Vector control cells were DKO MEF (LPA2), RH7777 (LPA1/3), CHO (LPA4), and B103 (LPA5)
transfected with the human LPA receptor orthologue (in parentheses) or transduced with appropriate empty vector. EC50 concentration is given in
μM for dose−response curves covering the 0.0001 nM to 10 μM range. For determination of antagonist action, dose−response curves were
generated using an ∼Emax50 concentration of LPA 18:1 for any given LPA receptor subtype, and the ligand was coapplied in concentrations ranging
from 30 nM to 10 μM. Means represent the mean values of three assays.
C
dx.doi.org/10.1021/jm5007116 | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Brief Article
predicted to share approximately the same distance in critical
interactions with R3.28 and Q3.29 as compounds 3 and 4,
however, compound 11d binding affinity is −9.21 kcal/mol and
conformation strain is 6.50 (Figure 3B). To complete our SAR
studies, finally we prepared additional two compounds where
we changed the position of carboxy group on the head group of
phenyl ring of compound 4 from ortho to meta (compound
11a) and para (compound 11b) positions that abolished the
activity at LPA2. The corresponding methyl carboxy esters of
compounds 5 and 11a−d (compound 12a−e) were also
inactive at activating LPA2 up to 10 μM, the highest
concentration tested.
CONCLUSION
■
Here we designed and synthesized new SBA analogues using a
structure-based pharmacophore. Starting from our active
scaffold 4, the detailed structure−activity relationship profile
was established to understand the effect of particular
substituents on head and tail groups along with carbon linker.
We concluded that three important structural requirements are
critical to have potent and specific LPA2 agonistic activity; (i)
four carbon chain linker, (ii) keeping the same tail group 1H-
benzo[de]isoquinolyl-1,3(2H)-dione, and (iii) introducing the
electron withdrawing group such as chloro meta to the carboxy
group of compound 4. This approach yielded compound 11d,
which is the first nonlipid specific agonist of LPA2 with
picomolar affinity.
Figure 3. Docked positions of compound 4 (A) and compound 11d
(B), shown overlaid on compound 3 (purple) in the LPA2 binding
pocket. Critical residues for receptor activation are shown in stick.
Compounds were docked and energy minimized using the Molecular
Operating Environment, version 2009.10 software (Chemical
Computing Group Inc., 2012).
with a four carbon linker had the highest potency, lowering the
EC50 value of the compound from the micromolar to the
nanomolar range. Thus, the optimal length of these analogues is
at or near 15 Å that is the same as of LPA 18:1 (Scheme 1 and
Table 1). In continuation of our SAR, we explored the
modifications of compound 4 by keeping the linker length fixed
at four carbons. We replaced the 1H-benzo[de]isoquinolyl-
1,3(2H)-dione tail group with isoindolyl-1,3-dione (17) or
indolyl-2,3-dione (18) to obtain compounds 7a and 7b,
respectively. These two changes abolished the activation of
LPA2 up to 10 μM, the highest concentration tested. These tail
groups are predicted to occupy a highly hydrophobic region in
the LPA binding pocket. Modeling of the tail groups of
compounds 7a and 7b in the LPA2 binding pocket predicts
several missing π−π interactions (Supporting Information
Figure 1), which is the reason for their lack of activity. In our
final SAR modifications, we modified the phenyl head group of
compound 4. We replaced the hydrogen, which is para to the
carboxy group in compound 4 by an electron donating methoxy
group or withdrawing bromo group yielded compounds 8a and
8b, respectively. Compound 8a showed very weak agonist
activity, whereas compound 8b was more potent than
compound 4. We also introduced dicarboxy groups on the
head group to improve the potency because previous analysis of
intramolecular pH predicted that two negative charges of the
LPA phosphate interact with the receptor.10 During the
synthesis of the dicarboxy analogue (compound 10), we
obtained a cyclized intermediate compound 9, which was
further hydrolyzed to dicarboxy analogue 10. Compound 10
was considerably less potent than the compound 9. Next we
turned our attention to introduce the electron withdrawing
groups. Fluoro, chloro, and bromo substitutions in meta
position to the carboxy group of compound 4 produced
compounds 11c, 11d, and 8c, respectively. Among these three
analogues, compound 11d exhibited picomolar activity (EC50
(nM): 5.06 × 10−3 3.73 × 10−3 vs LPA 18:1; 1.40 0.51),
whereas compounds 11c and 8c showed 0.15 0.02 nM and
60.90 9.39 nM, respectively.
EXPERIMENTAL SECTION
■
Chemistry. All compounds were analyzed by 1H NMR, 13C NMR,
MASS, and HRMS. The purity of final compounds was ≥95% as
measured by HPLC. Full experimental procedures can be found in the
Supporting Information.
1
Analytical Data for Compound 11d. Yield 53%. H NMR (400
MHz, DMSO-d6) d 9.13 (bs, 1H), 8.52−8.44 (m, 4H), 7.88−7.85 (m,
2H), 7.71−7.68 (m, 1H), 7.61 (d, J = 2.4 Hz, 1H), 7.43 (dd, J = 2.0
Hz, 2.4 Hz, 1H), 3.99 (t, J = 7.2 Hz, 2H), 2.74 (q, J = 6.4 Hz, 2H),
1.65−1.57 (m, 2H), 1.47−1.39 (m, 2H). 13C NMR (400 MHz,
DMSO-d6) d 167.67, 163.38, 136.53, 135.18, 134.29, 131.28, 130.73,
130.19, 129.23, 127.35, 127.20, 127.12, 122.01, 42.72, 40.11, 26.73,
25.01. MS (ES−) m/z 485 (M − H)−. HPLC purity: tR = 2.23,
98.09%. HRMS calcd for C23H19ClN2O6S, 487.0731 (M − H)−;
found, 487.0737.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental details of chemical synthesis, computational and
biological tests. This material is available free of charge via the
Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*Phone: 901-448-4793. Fax: 901-448-7126. E-mail: gtigyi@
uthsc.edu.
Author Contributions
∥R.P. and J.I.F. contributed equally to this work.
Notes
The authors declare the following competing financial
interest(s): G.T. and D.M. are founders and stock holders of
RxBio Inc.
Molecular docking simulations revealed that the addition of
halogens at the para position would lead to compounds with a
conformation strain similar to compound 3. Compound 11d is
D
dx.doi.org/10.1021/jm5007116 | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Brief Article
(13) Kamal, A.; Ramu, R.; Tekumalla, V.; Khanna, G. B.; Barkume,
M. S.; Juvekar, A. S.; Zingde, S. M. Remarkable DNA binding affinity
and potential anticancer activity of pyrrolo[2,1-c][1,4]-
benzodiazepine−naphthalimide conjugates linked through piperazine
side-armed alkane spacers. Bioorg. Med. Chem. 2008, 16, 7218−7224.
(14) Tumiatti, V.; Milelli, A.; Minarini, A.; Micco, M.; Gasperi
Campani, A.; Roncuzzi, L.; Baiocchi, D.; Marinello, J.; Capranico, G.;
Zini, M.; Stefanelli, C.; Melchiorre, C. Design, synthesis, and biological
evaluation of substituted naphthalene imides and diimides as
anticancer agent. J. Med. Chem. 2009, 52, 7873−7877.
ACKNOWLEDGMENTS
■
This work was supported by grants from National Institute of
Allergy and Infectious Diseases (NIAID AI080405 to G. T.),
the American Cancer Society (ACS 122059-PF-12-107-01-
COD to J.I.F.), the Van Vleet Endowment (G. T.) and by
Award Number I01BX007080 from the Biomedical Laboratory
Research & Development Service of the VA Office of Research
and Development (G.T.).
ABBREVIATIONS USED
■
LPA, lysophosphatidic acid; K2CO3, potassium carbonate;
DMF, dimethylformamide; THF, tetrahydrofuran; RT, room
temperature; SBA, sulfamoyl benzoic acid; SAR, structure−
activity relationship
REFERENCES
■
(1) E, S.; Lai, Y. J.; Tsukahara, R.; Chen, C. S.; Fujiwara, Y.; Yue, J.;
Yu, J. H.; Guo, H.; Kihara, A.; Tigyi, G.; Lin, F. T. Lysophosphatidic
acid 2 receptor-mediated supramolecular complex formation regulates
its antiapoptotic effect. J. Biol. Chem. 2009, 284, 14558−14571.
(2) Kiss, G. N.; Lee, S. C.; Fells, J. I.; Liu, J.; Valentine, W. J.;
Fujiwara, Y.; Thompson, K. E.; Yates, C. R.; Sumegi, B.; Tigyi, G.
Mitigation of radiation injury by selective stimulation of the LPA(2)
receptor. Biochim. Biophys. Acta 2013, 1831, 117−125.
(3) Lin, F. T.; Lai, Y. J.; Makarova, N.; Tigyi, G.; Lin, W. C. The
lysophosphatidic acid 2 receptor mediates down-regulation of Siva-1 to
promote cell survival. J. Biol. Chem. 2007, 282, 37759−37769.
(4) Tigyi, G. Aiming drug discovery at lysophosphatidic acid targets.
Br. J. Pharmacol. 2010, 161, 241−270.
(5) Deng, W.; Balazs, L.; Wang, D. A.; Van Middlesworth, L.; Tigyi,
G.; Johnson, L. R. Lysophosphatidic acid protects and rescues
intestinal epithelial cells from radiation- and chemotherapy-induced
apoptosis. Gastroenterology 2002, 123, 206−216.
(6) Deng, W.; Poppleton, H.; Yasuda, S.; Makarova, N.; Shinozuka,
Y.; Wang, D. A.; Johnson, L. R.; Patel, T. B.; Tigyi, G. Optimal
lysophosphatidic acid-induced DNA synthesis and cell migration but
not survival require intact autophosphorylation sites of the epidermal
growth factor receptor. J. Biol. Chem. 2004, 279, 47871−47880.
(7) Deng, W.; Shuyu, E.; Tsukahara, R.; Valentine, W. J.; Durgam,
G.; Gududuru, V.; Balazs, L.; Manickam, V.; Arsura, M.;
VanMiddlesworth, L.; Johnson, L. R.; Parrill, A. L.; Miller, D. D.;
Tigyi, G. The lysophosphatidic acid type 2 receptor is required for
protection against radiation-induced intestinal injury. Gastroenterology
2007, 132, 1834−18351.
(8) Funke, M.; Zhao, Z.; Xu, Y.; Chun, J.; Tager, A. M. The
lysophosphatidic acid receptor LPA1 promotes epithelial cell apoptosis
after lung injury. Am. J. Respir. Cell Mol. Biol. 2012, 46, 355−64.
(9) Furui, T.; LaPushin, R.; Mao, M.; Khan, H.; Watt, S. R.; Watt, M.
A.; Lu, Y.; Fang, X.; Tsutsui, S.; Siddik, Z. H.; Bast, R. C.; Mills, G. B.
Overexpression of edg-2/vzg-1 induces apoptosis and anoikis in
ovarian cancer cells in a lysophosphatidic acid-independent manner.
Clin. Cancer Res. 1999, 5, 4308−18.
(10) Kiss, G. N.; Fells, J. I.; Gupte, R.; Lee, S. C.; Liu, J.; Nusser, N.;
Lim, K. G.; Ray, R. M.; Lin, F. T.; Parrill, A. L.; Sumegi, B.; Miller, D.
D.; Tigyi, G. Virtual screening for LPA2-specific agonists identifies a
nonlipid compound with antiapoptotic actions. Mol. Pharmacol. 2012,
82, 1162−1173.
(11) Fujiwara, Y.; Sardar, V.; Tokumura, A.; Baker, D.; Murakami-
Murofushi, K.; Parrill, A.; Tigyi, G. Identification of residues
responsible for ligand recognition and regioisomeric selectivity of
lysophosphatidic acid receptors expressed in mammalian cells. J. Biol.
Chem. 2005, 280, 35038−35050.
(12) Sardar, V. M.; Bautista, D. L.; Fischer, D. J.; Yokoyama, K.;
Nusser, N.; Virag, T.; Wang, D. A.; Baker, D. L.; Tigyi, G.; Parrill, A. L.
Molecular basis for lysophosphatidic acid receptor antagonist
selectivity. Biochim. Biophys. Acta 2002, 1582, 309−317.
E
dx.doi.org/10.1021/jm5007116 | J. Med. Chem. XXXX, XXX, XXX−XXX