A Global Map of Lipid-Binding Proteins and Their Ligandability in Cells.

Lipids play central roles in physiology and disease, where their structural, metabolic, and signaling functions often arise from interactions with proteins. Here, we describe a set of lipid-based chemical proteomic probes and their global interaction map in mammalian cells. These interactions involve hundreds of proteins from diverse functional classes and frequently occur at sites of drug action. We determine the target profiles for several drugs across the lipid-interaction proteome, revealing that its ligandable content extends far beyond traditionally defined categories of druggable proteins. In further support of this finding, we describe a selective ligand for the lipid-binding protein nucleobindin-1 (NUCB1) and show that this compound perturbs the hydrolytic and oxidative metabolism of endocannabinoids in cells. The described chemical proteomic platform thus provides an integrated path to both discover and pharmacologically characterize a wide range of proteins that participate in lipid pathways in cells.

Enzyme inhibitor discovery by activity-based protein profiling.

Eukaryotic and prokaryotic organisms possess huge numbers of uncharacterized enzymes. Selective inhibitors offer powerful probes for assigning functions to enzymes in native biological systems. Here, we discuss how the chemical proteomic platform activity-based protein profiling (ABPP) can be implemented to discover selective and in vivo-active inhibitors for enzymes. We further describe how these inhibitors have been used to delineate the biochemical and cellular functions of enzymes, leading to the discovery of metabolic and signaling pathways that make important contributions to human physiology and disease. These studies demonstrate the value of selective chemical probes as drivers of biological inquiry.

Chemoproteomic identification of a DPP4 homolog in Bacteroides thetaiotaomicron.

Serine hydrolases have important roles in signaling and human metabolism, yet little is known about their functions in gut commensal bacteria. Using bioinformatics and chemoproteomics, we identify serine hydrolases in the gut commensal Bacteroides thetaiotaomicron that are specific to the Bacteroidetes phylum. Two are predicted homologs of the human dipeptidyl peptidase 4 (hDPP4), a key enzyme that regulates insulin signaling. Our functional studies reveal that BT4193 is a true homolog of hDPP4 that can be inhibited by FDA-approved type 2 diabetes medications targeting hDPP4, while the other is a misannotated proline-specific triaminopeptidase. We demonstrate that BT4193 is important for envelope integrity and that loss of BT4193 reduces B. thetaiotaomicron fitness during in vitro growth within a diverse community. However, neither function is dependent on BT4193 proteolytic activity, suggesting a scaffolding or signaling function for this bacterial protease.

ABHD17 regulation of plasma membrane palmitoylation and N-Ras-dependent cancer growth.

Multiple Ras proteins, including N-Ras, depend on a palmitoylation/depalmitoylation cycle to regulate their subcellular trafficking and oncogenicity. General lipase inhibitors such as Palmostatin M (Palm M) block N-Ras depalmitoylation, but lack specificity and target several enzymes displaying depalmitoylase activity. Here, we describe ABD957, a potent and selective covalent inhibitor of the ABHD17 family of depalmitoylases, and show that this compound impairs N-Ras depalmitoylation in human acute myeloid leukemia (AML) cells. ABD957 produced partial effects on N-Ras palmitoylation compared with Palm M, but was much more selective across the proteome, reflecting a plasma membrane-delineated action on dynamically palmitoylated proteins. Finally, ABD957 impaired N-Ras signaling and the growth of NRAS-mutant AML cells in a manner that synergizes with MAP kinase kinase (MEK) inhibition. Our findings uncover a surprisingly restricted role for ABHD17 enzymes as regulators of the N-Ras palmitoylation cycle and suggest that ABHD17 inhibitors may have value as targeted therapies for NRAS-mutant cancers.

AIG1 and ADTRP are endogenous hydrolases of fatty acid esters of hydroxy fatty acids (FAHFAs) in mice.

Fatty acid esters of hydroxy fatty acids (FAHFAs) are a newly discovered class of signaling lipids with anti-inflammatory and anti-diabetic properties. However, the endogenous regulation of FAHFAs remains a pressing but unanswered question. Here, using MS-based FAHFA hydrolysis assays, LC-MS-based lipidomics analyses, and activity-based protein profiling, we found that androgen-induced gene 1 (AIG1) and androgen-dependent TFPI-regulating protein (ADTRP), two threonine hydrolases, control FAHFA levels in vivo in both genetic and pharmacologic mouse models. Tissues from mice lacking ADTRP (Adtrp-KO), or both AIG1 and ADTRP (DKO) had higher concentrations of FAHFAs particularly isomers with the ester bond at the 9th carbon due to decreased FAHFA hydrolysis activity. The levels of other lipid classes were unaltered indicating that AIG1 and ADTRP specifically hydrolyze FAHFAs. Complementing these genetic studies, we also identified a dual AIG1/ADTRP inhibitor, ABD-110207, which is active in vivo Acute treatment of WT mice with ABD-110207 resulted in elevated FAHFA levels, further supporting the notion that AIG1 and ADTRP activity control endogenous FAHFA levels. However, loss of AIG1/ADTRP did not mimic the changes associated with pharmacologically administered FAHFAs on extent of upregulation of FAHFA levels, glucose tolerance, or insulin sensitivity in mice, indicating that therapeutic strategies should weigh more on FAHFA administration. Together, these findings identify AIG1 and ADTRP as the first endogenous FAHFA hydrolases identified and provide critical genetic and chemical tools for further characterization of these enzymes and endogenous FAHFAs to unravel their physiological functions and roles in health and disease.

Diacylglycerol lipase disinhibits VTA dopamine neurons during chronic nicotine exposure.

Chronic nicotine exposure (CNE) alters synaptic transmission in the ventral tegmental area (VTA) in a manner that enhances dopaminergic signaling and promotes nicotine use. The present experiments identify a correlation between enhanced production of the endogenous cannabinoid 2-arachidonoylglycerol (2-AG) and diminished release of the inhibitory neurotransmitter GABA in the VTA following CNE. To study the functional role of on-demand 2-AG signaling in GABAergic synapses, we used 1,2,3-triazole urea compounds to selectively inhibit 2-AG biosynthesis by diacylglycerol lipase (DAGL). The potency and selectivity of these inhibitors were established in rats in vitro (rat brain proteome), ex vivo (brain slices), and in vivo (intracerebroventricular administration) using activity-based protein profiling and targeted metabolomics analyses. Inhibition of DAGL (2-AG biosynthesis) rescues nicotine-induced VTA GABA signaling following CNE. Conversely, enhancement of 2-AG signaling in naïve rats by inhibiting 2-AG degradation recapitulates the loss of nicotine-induced GABA signaling evident following CNE. DAGL inhibition reduces nicotine self-administration without disrupting operant responding for a nondrug reinforcer or motor activity. Collectively, these findings provide a detailed characterization of selective inhibitors of rat brain DAGL and demonstrate that excessive 2-AG signaling contributes to a loss of inhibitory GABAergic constraint of VTA excitability following CNE.

Monoacylglycerol Lipase Inhibitors Reverse Paclitaxel-Induced Nociceptive Behavior and Proinflammatory Markers in a Mouse Model of Chemotherapy-Induced Neuropathy.

Although paclitaxel effectively treats various cancers, its debilitating peripheral neuropathic pain side effects often persist long after treatment has ended. Therefore, a compelling need exists for the identification of novel pharmacologic strategies to mitigate this condition. As inhibitors of monoacylglycerol lipase (MAGL), the primary hydrolytic enzyme of the endogenous cannabinoid, 2-arachidonyolglycerol, produces antinociceptive effects in numerous rodent models of pain, we investigated whether inhibitors of this enzyme (i.e., JZL184 and MJN110) would reverse paclitaxel-induced mechanical allodynia in mice. These drugs dose dependently reversed allodynia with respective ED50 values (95% confidence limit) of 8.4 (5.2-13.6) and 1.8 (1.0-3.3) mg/kg. Complementary genetic and pharmacologic approaches revealed that the antiallodynic effects of each drug require both cannabinoid receptors, CB1 and CB2 MJN110 reduced paclitaxel-mediated increased expression of monocyte chemoattractant protein-1 (MCP-1, CCL2) and phospho-p38 MAPK in dorsal root ganglia as well as MCP-1 in spinal dorsal horn. Whereas the antinociceptive effects of high dose JZL184 (40 mg/kg) underwent tolerance following 6 days of repeated dosing, repeated administration of a threshold dose (i.e., 4 mg/kg) completely reversed paclitaxel-induced allodynia. In addition, we found that the administration of MJN110 to control mice lacked intrinsic rewarding effects in the conditioned place preference (CPP) paradigm. However, it produced a CPP in paclitaxel-treated animals, suggesting a reduced paclitaxel-induced aversive state. Importantly, JZL184 did not alter the antiproliferative and apoptotic effects of paclitaxel in A549 and H460 non-small cell lung cancer cells. Taken together, these data indicate that MAGL inhibitors reverse paclitaxel-induced neuropathic pain without interfering with chemotherapeutic efficacy.

Monoacylglycerol Lipase Inhibition in Human and Rodent Systems Supports Clinical Evaluation of Endocannabinoid Modulators.

Monoacylglycerol lipase (MGLL) is the primary degradative enzyme for the endocannabinoid 2-arachidonoylglycerol (2-AG). The first MGLL inhibitors have recently entered clinical development for the treatment of neurologic disorders. To support this clinical path, we report the pharmacological characterization of the highly potent and selective MGLL inhibitor ABD-1970 [1,1,1,3,3,3-hexafluoropropan-2-yl 4-(2-(8-oxa-3-azabicyclo[3.2.1]octan-3-yl)-4-chlorobenzyl)piperazine-1-carboxylate]. We used ABD-1970 to confirm the role of MGLL in human systems and to define the relationship between MGLL target engagement, brain 2-AG concentrations, and efficacy. Because MGLL contributes to arachidonic acid metabolism in a subset of rodent tissues, we further used ABD-1970 to evaluate whether selective MGLL inhibition would affect prostanoid production in several human assays known to be sensitive to cyclooxygenase inhibitors. ABD-1970 robustly elevated brain 2-AG content and displayed antinociceptive and antipruritic activity in a battery of rodent models (ED50 values of 1-2 mg/kg). The antinociceptive effects of ABD-1970 were potentiated when combined with analgesic standards of care and occurred without overt cannabimimetic effects. ABD-1970 also blocked 2-AG hydrolysis in human brain tissue and elevated 2-AG content in human blood without affecting stimulated prostanoid production. These findings support the clinical development of MGLL inhibitors as a differentiated mechanism to treat pain and other neurologic disorders.

The Selective Monoacylglycerol Lipase Inhibitor MJN110 Produces Opioid-Sparing Effects in a Mouse Neuropathic Pain Model.

Serious clinical liabilities associated with the prescription of opiates for pain control include constipation, respiratory depression, pruritus, tolerance, abuse, and addiction. A recognized strategy to circumvent these side effects is to combine opioids with other antinociceptive agents. The combination of opiates with the primary active constituent of cannabis (Δ(9)-tetrahydrocannabinol) produces enhanced antinociceptive actions, suggesting that cannabinoid receptor agonists can be opioid sparing. Here, we tested whether elevating the endogenous cannabinoid 2-arachidonoylglycerol through the inhibition of its primary hydrolytic enzyme monoacylglycerol lipase (MAGL), will produce opioid-sparing effects in the mouse chronic constriction injury (CCI) of the sciatic nerve model of neuropathic pain. The dose-response relationships of i.p. administration of morphine and the selective MAGL inhibitor 2,5-dioxopyrrolidin-1-yl 4-(bis(4-chlorophenyl)methyl)piperazine-1-carboxylate (MJN110) were tested alone and in combination at equieffective doses for reversal of CCI-induced mechanical allodynia and thermal hyperalgesia. The respective ED50 doses (95% confidence interval) of morphine and MJN110 were 2.4 (1.9-3.0) mg/kg and 0.43 (0.23-0.79) mg/kg. Isobolographic analysis of these drugs in combination revealed synergistic antiallodynic effects. Acute antinociceptive effects of the combination of morphine and MJN110 required µ-opioid, CB1, and CB2 receptors. This combination did not reduce gastric motility or produce subjective cannabimimetic effects in the drug discrimination assay. Importantly, combinations of MJN110 and morphine given repeatedly (i.e., twice a day for 6 days) continued to produce antiallodynic effects with no evidence of tolerance. Taken together, these findings suggest that MAGL inhibition produces opiate-sparing events with diminished tolerance, constipation, and cannabimimetic side effects.

Discriminative Stimulus Properties of the Endocannabinoid Catabolic Enzyme Inhibitor SA-57 in Mice.

Whereas the inhibition of fatty acid amide hydrolase (FAAH) or monoacylglycerol lipase (MAGL), the respective major hydrolytic enzymes of N-arachidonoyl ethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), elicits no or partial substitution for Δ(9)-tetrahydrocannabinol (THC) in drug-discrimination procedures, combined inhibition of both enzymes fully substitutes for THC, as well as produces a constellation of cannabimimetic effects. The present study tested whether C57BL/6J mice would learn to discriminate the dual FAAH-MAGL inhibitor SA-57 (4-[2-(4-chlorophenyl)ethyl]-1-piperidinecarboxylic acid 2-(methylamino)-2-oxoethyl ester) from vehicle in the drug-discrimination paradigm. In initial experiments, 10 mg/kg SA-57 fully substituted for CP55,940 ((-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol), a high-efficacy CB1 receptor agonist in C57BL/6J mice and for AEA in FAAH (-/-) mice. Most (i.e., 23 of 24) subjects achieved criteria for discriminating SA-57 (10 mg/kg) from vehicle within 40 sessions, with full generalization occurring 1 to 2 hours postinjection. CP55,940, the dual FAAH-MAGL inhibitor JZL195 (4-​nitrophenyl 4-​(3-​phenoxybenzyl)piperazine-​1-​carboxylate), and the MAGL inhibitors MJN110 (2,5-dioxopyrrolidin-1-yl 4-(bis(4-chlorophenyl)methyl)piperazine-1-carboxylate) and JZL184 (4-[Bis(1,3-benzodioxol-5-yl)hydroxymethyl]-1-piperidinecarboxylic acid 4-nitrophenyl ester) fully substituted for SA-57. Although the FAAH inhibitors PF-3845 ((N-3-pyridinyl-4-[[3-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenyl]methyl]-1-piperidinecarboxamide) and URB597 (cyclohexylcarbamic acid 3'-(aminocarbonyl)-[1,1'-biphenyl]-3-yl ester) did not substitute for SA-57, PF-3845 produced a 2-fold leftward shift in the MJN110 substitution dose-response curve. In addition, the CB1 receptor antagonist rimonabant blocked the generalization of SA-57, as well as substitution of CP55,940, JZL195, MJN110, and JZL184. These findings suggest that MAGL inhibition plays a major role in the CB1 receptor-mediated SA-57 training dose, which is further augmented by FAAH inhibition.

Proteome-wide mapping of cholesterol-interacting proteins in mammalian cells.

Cholesterol is an essential structural component of cellular membranes and serves as a precursor for several classes of signaling molecules. Cholesterol exerts its effects and is, itself, regulated in large part by engagement in specific interactions with proteins. The full complement of sterol-binding proteins that exist in mammalian cells, however, remains unknown. Here we describe a chemoproteomic strategy that uses clickable, photoreactive sterol probes in combination with quantitative mass spectrometry to globally map cholesterol-protein interactions directly in living cells. We identified over 250 cholesterol-binding proteins, including receptors, channels and enzymes involved in many established and previously unreported interactions. Prominent among the newly identified interacting proteins were enzymes that regulate sugars, glycerolipids and cholesterol itself as well as proteins involved in vesicular transport and protein glycosylation and degradation, pointing to key nodes in biochemical pathways that may couple sterol concentrations to the control of other metabolites and protein localization and modification.

Δ9-tetrahydrocannabinol and endocannabinoid degradative enzyme inhibitors attenuate intracranial self-stimulation in mice.

A growing body of evidence implicates endogenous cannabinoids as modulators of the mesolimbic dopamine system and motivated behavior. Paradoxically, the reinforcing effects of Δ(9)-tetrahydrocannabinol (THC), the primary psychoactive constituent of cannabis, have been difficult to detect in preclinical rodent models. In this study, we investigated the impact of THC and inhibitors of the endocannabinoid hydrolytic enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) on operant responding for electrical stimulation of the medial forebrain bundle [intracranial self-stimulation (ICSS)], which is known to activate the mesolimbic dopamine system. These drugs were also tested in assays of operant responding for food reinforcement and spontaneous locomotor activity. THC and the MAGL inhibitor JZL184 (4-[bis(1,3-benzodioxol-5-yl)hydroxymethyl]-1-piperidinecarboxylic acid 4-nitrophenyl ester) attenuated operant responding for ICSS and food, and also reduced spontaneous locomotor activity. In contrast, the FAAH inhibitor PF-3845 (N-3-pyridinyl-4-[[3-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenyl]methyl]-1-piperidinecarboxamide) was largely without effect in these assays. Consistent with previous studies showing that combined inhibition of FAAH and MAGL produces a substantially greater cannabimimetic profile than single enzyme inhibition, the dual FAAH-MAGL inhibitor SA-57 (4-[2-(4-chlorophenyl)ethyl]-1-piperidinecarboxylic acid 2-(methylamino)-2-oxoethyl ester) produced a similar magnitude of ICSS depression as that produced by THC. ICSS attenuation by JZL184 was associated with increased brain levels of 2-arachidonoylglycerol (2-AG), whereas peak effects of SA-57 were associated with increased levels of both N-arachidonoylethanolamine (anandamide) and 2-AG. The cannabinoid receptor type 1 receptor antagonist rimonabant, but not the cannabinoid receptor type 2 receptor antagonist SR144528, blocked the attenuating effects of THC, JZL184, and SA-57 on ICSS. Thus, THC, MAGL inhibition, and dual FAAH-MAGL inhibition not only reduce ICSS, but also decrease other reinforced and nonreinforced behaviors.

Mapping the protein interaction landscape for fully functionalized small-molecule probes in human cells.

Phenotypic screening provides a means to discover small molecules that perturb cell biological processes. Discerning the proteins and biochemical pathways targeted by screening hits, however, remains technically challenging. We recently described the use of small molecules bearing photoreactive groups and latent affinity handles as fully functionalized probes for integrated phenotypic screening and target identification. The general utility of such probes, or, for that matter, any small-molecule screening library, depends on the scope of their protein interactions in cells, a parameter that remains largely unexplored. Here, we describe the synthesis of an ~60-member fully functionalized probe library, prepared from Ugi-azide condensation reactions to impart structural diversity and introduce diazirine and alkyne functionalities for target capture and enrichment, respectively. In-depth mass spectrometry-based analysis revealed a diverse array of probe targets in human cells, including enzymes, channels, adaptor and scaffolding proteins, and proteins of uncharacterized function. For many of these proteins, ligands have not yet been described. Most of the probe-protein interactions showed well-defined structure-activity relationships across the probe library and were blocked by small-molecule competitors in cells. These findings indicate that fully functionalized small molecules canvas diverse segments of the human proteome and hold promise as pharmacological probes of cell biology.

Remodeling natural products: chemistry and serine hydrolase activity of a rocaglate-derived ß-lactone.

Flavaglines are a class of natural products with potent insecticidal and anticancer activities. ß-Lactones are a privileged structural motif found in both therapeutic agents and chemical probes. Herein, we report the synthesis, unexpected light-driven di-epimerization, and activity-based protein profiling of a novel rocaglate-derived ß-lactone. In addition to in vitro inhibition of the serine hydrolases ABHD10 and ACOT1/2, the most potent ß-lactone enantiomer was also found to inhibit these enzymes, as well as the serine peptidases CTSA and SCPEP1, in PC3 cells.

Ligand discovery by activity-based protein profiling.

Genomic technologies have led to massive gains in our understanding of human gene function and disease relevance. Chemical biologists are a primary beneficiary of this information, which can guide the prioritization of proteins for chemical probe and drug development. The vast functional and structural diversity of disease-relevant proteins, however, presents challenges for conventional small molecule screening libraries and assay development that in turn raise questions about the broader "druggability" of the human proteome. Here, we posit that activity-based protein profiling (ABPP), by generating global maps of small molecule-protein interactions in native biological systems, is well positioned to address major obstacles in human biology-guided chemical probe and drug discovery. We will support this viewpoint with case studies highlighting a range of small molecule mechanisms illuminated by ABPP that include the disruption and stabilization of biomolecular (protein-protein/nucleic acid) interactions and underscore allostery as a rich source of chemical tools for historically "undruggable" protein classes.

A helping HAND: therapeutic potential of MAGL inhibition against HIV-1-associated neuroinflammation.

Background: Human immunodeficiency virus (HIV) affects nearly 40 million people globally, with roughly 80% of all people living with HIV receiving antiretroviral therapy. Antiretroviral treatment suppresses viral load in peripheral tissues but does not effectively penetrate the blood-brain barrier. Thus, viral reservoirs persist in the central nervous system and continue to produce low levels of inflammatory factors and early viral proteins, including the transactivator of transcription (Tat). HIV Tat is known to contribute to chronic neuroinflammation and synaptodendritic damage, which is associated with the development of cognitive, motor, and/or mood problems, collectively known as HIV-associated neurocognitive disorders (HAND). Cannabinoid anti-inflammatory effects are well documented, but therapeutic utility of cannabis remains limited due to its psychotropic effects, including alterations within brain regions encoding reward processing and motivation, such as the nucleus accumbens. Alternatively, inhibiting monoacylglycerol lipase (MAGL) has demonstrated therapeutic potential through interactions with the endocannabinoid system. Methods: The present study utilized a reward-related operant behavioral task to quantify motivated behavior in female Tat transgenic mice treated with vehicle or MAGL inhibitor MJN110 (1 mg/kg). Brain tissue was collected to assess dendritic injury and neuroinflammatory profiles, including dendritic microtubule-associated protein (MAP2ab) intensity, microglia density, microglia morphology, astrocyte density, astrocytic interleukin-1ß (IL-1ß) colocalization, and various lipid mediators. Results: No significant behavioral differences were observed; however, MJN110 protected against Tat-induced dendritic injury by significantly upregulating MAP2ab intensity in the nucleus accumbens and in the infralimbic cortex of Tat(+) mice. No or only minor effects were noted for Iba-1+ microglia density and/or microglia morphology. Further, Tat increased GFAP+ astrocyte density in the infralimbic cortex and GFAP+ astrocytic IL-1ß colocalization in the nucleus accumbens, with MJN110 significantly reducing these measures in Tat(+) subjects. Lastly, selected HETE-related inflammatory lipid mediators in the striatum were downregulated by chronic MJN110 treatment. Conclusions: These findings demonstrate anti-inflammatory and neuroprotective properties of MJN110 without cannabimimetic behavioral effects and suggest a promising alternative to cannabis for managing neuroinflammation.

Inflammation causes insulin resistance in mice via interferon regulatory factor 3 (IRF3)-mediated reduction in FAHFA levels.

Obesity-induced inflammation causes metabolic dysfunction, but the mechanisms remain elusive. Here we show that the innate immune transcription factor interferon regulatory factor (IRF3) adversely affects glucose homeostasis through induction of the endogenous FAHFA hydrolase androgen induced gene 1 (AIG1) in adipocytes. Adipocyte-specific knockout of IRF3 protects male mice against high-fat diet-induced insulin resistance, whereas overexpression of IRF3 or AIG1 in adipocytes promotes insulin resistance on a high-fat diet. Furthermore, pharmacological inhibition of AIG1 reversed obesity-induced insulin resistance and restored glucose homeostasis in the setting of adipocyte IRF3 overexpression. We, therefore, identify the adipocyte IRF3/AIG1 axis as a crucial link between obesity-induced inflammation and insulin resistance and suggest an approach for limiting the metabolic dysfunction accompanying obesity.

Selective inhibitors and tailored activity probes for lipoprotein-associated phospholipase A(2).

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2) or PLA(2)G7) binds to low-density lipoprotein (LDL) particles, where it is thought to hydrolyze oxidatively truncated phospholipids. Lp-PLA(2) has also been implicated as a pro-tumorigenic enzyme in human prostate cancer. Several inhibitors of Lp-PLA(2) have been described, including darapladib, which is currently in phase 3 clinical development for the treatment of atherosclerosis. The selectivity that darapladib and other Lp-PLA(2) inhibitors display across the larger serine hydrolase family has not, however, been reported. Here, we describe the use of both general and tailored activity-based probes for profiling Lp-PLA(2) and inhibitors of this enzyme in native biological systems. We show that both darapladib and a novel class of structurally distinct carbamate inhibitors inactivate Lp-PLA(2) in mouse tissues and human cell lines with high selectivity. Our findings thus identify both inhibitors and chemoproteomic probes that are suitable for investigating Lp-PLA(2) function in biological systems.

Attenuating ABHD17 enhances S- palmitoylation, membrane localization and signal transduction of NOD2 and Crohn's disease-associated variants.

NOD2 is an intracellular innate immune receptor that senses bacterial peptidoglycans. Although soluble in the cytosol, a portion of the protein is associated with the plasma membrane and endosomal compartments for microbial surveillance. Palmitoylation of NOD2 by zDHHC5 promotes its membrane recruitment to drive proinflammatory and antimicrobial responses to pathogenic invasion. A depalmitoylation step by an unknown protein, thioesterase, releases NOD2 from membranes into the cytosol, where the protein can then enter a new cycle of palmitoylation-depalmitoylation. Here, we identify α/ß -hydrolase domain-containing protein 17 isoforms (ABHD17A, 17B, 17C) as the thioesterases responsible for depalmitoylation of NOD2. Inhibiting ABHD17 increased the plasmalemmal localization of both wild-type NOD2 and a subset of hypo-palmitoylated Crohn's disease-associated variants, resulting in increased NF-κB activation and production of pro-inflammatory cytokines in epithelial cells. These results suggest that targeted inhibition of ABHD17 may rescue some Crohn's disease-associated NOD2 variants.

Copper-assisted palladium(II)-catalyzed direct arylation of cyclic enaminones with arylboronic acids.

Described herein is a palladium(II)-catalyzed direct arylation of cyclic enaminones with arylboronic acids. The versatility of this method is that both electron-rich and electron-poor boronic acids can be coupled in high yields. A mixture of two Cu(II) additives was crucial for efficient cross-coupling. The role of each Cu(II) reagent appears to be distinct and complementary serving to assist catalyst reoxidation and transmetalation through a putative arylcopper intermediate.