Inhibiting long chain fatty Acyl CoA synthetase increases basal and agonist-stimulated NO synthesis in endothelium

Fatty Acid Synthase inhibitor TVB-3166 prevents S-acylation of the Spike protein of human coronaviruses

The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other coronaviruses mediates host cell entry and is S-acylated on multiple phylogenetically conserved cysteine residues. Multiple protein acyltransferase enzymes have been reported to post-translationally modify spike proteins; however, strategies to exploit this modification are lacking. Using resin-assisted capture MS, we demonstrate that the spike protein is S-acylated in SARS-CoV-2-infected human and monkey epithelial cells. We further show that increased abundance of the acyltransferase ZDHHC5 associates with increased S-acylation of the spike protein, whereas ZDHHC5 knockout cells had a 40% reduction in the incorporation of an alkynyl-palmitate using click chemistry detection. We also found that the S-acylation of the spike protein is not limited to palmitate, as clickable versions of myristate and stearate were also labelled the protein. Yet, we observed that ZDHHC5 was only modified when incubated with alkyne-palmitate, suggesting it has specificity for this acyl-CoA, and that other ZDHHC enzymes may use additional fatty acids to modify the spike protein. Since multiple ZDHHC isoforms may modify the spike protein, we also examined the ability of the FASN inhibitor TVB-3166 to prevent S-acylation of the spike proteins of SARS-CoV-2 and human CoV-229E. We show that treating cells with TVB-3166 inhibited S-acylation of expressed spike proteins and attenuated the ability of SARS-CoV-2 and human CoV-229E to spread in vitro. Our findings further substantiate the necessity of CoV spike protein S-acylation and demonstrate that de novo fatty acid synthesis is critical for the proper S-acylation of the spike protein.

Lipid-induced S-palmitoylation as a Vital Regulator of Cell Signaling and Disease Development

Lipid metabolites are emerging as pivotal regulators of protein function and cell signaling. The availability of intracellular fatty acid is tightly regulated by glycolipid metabolism and may affect human body through many biological mechanisms. Recent studies have demonstrated palmitate, either from exogenous fatty acid uptake or de novo fatty acid synthesis, may serve as the substrate for protein palmitoylation and regulate protein function via palmitoylation. Palmitoylation, the most-studied protein lipidation, encompasses the reversible covalent attachment of palmitate moieties to protein cysteine residues. It controls various cellular physiological processes and alters protein stability, conformation, localization, membrane association and interaction with other effectors. Dysregulation of palmitoylation has been implicated in a plethora of diseases, such as metabolic syndrome, cancers, neurological disorders and infections. Accordingly, it could be one of the molecular mechanisms underlying the impact of palmitate metabolite on cellular homeostasis and human diseases. Herein, we explore the relationship between lipid metabolites and the regulation of protein function through palmitoylation. We review the current progress made on the putative role of palmitate in altering the palmitoylation of key proteins and thus contributing to the pathogenesis of various diseases, among which we focus on metabolic disorders, cancers, inflammation and infections, neurodegenerative diseases. We also highlight the opportunities and new therapeutics to target palmitoylation in disease development.

Inhibition of long chain fatty acyl-CoA synthetase (ACSL) and ischemia reperfusion injury

Various triacsin C analogs, containing different alkenyl chains and carboxylic acid bioisoteres including 4-aminobenzoic acid, isothiazolidine dioxide, hydroxylamine, hydroxytriazene, and oxadiazolidine dione, were synthesized and their inhibitions of long chain fatty acyl-CoA synthetase (ACSL) were examined. Two methods, a cell-based assay of ACSL activity and an in situ [(14)C]-palmitate incorporation into extractable lipids were used to study the inhibition. Using an in vivo leukocyte recruitment inhibition protocol, the translocation of one or more cell adhesion molecules from the cytoplasm to the plasma membrane on either the endothelium or leukocyte or both was inhibited by inhibitors 1, 9, and triacsin C. The results suggest that inhibition of ACSL may attenuate the vascular inflammatory component associated with ischemia reperfusion injury and lead to a decrease of infarct expansion.

Activity of long-chain acyl-CoA synthetase is required for maintaining meiotic arrest in Xenopus laevis

In most vertebrates, fully grown oocytes are arrested in meiotic prophase I and only resume the cell cycle upon external stimuli, such as hormones. The proper arrest and resumption of the meiotic cycle is critical for reproduction. A Galpha(S) signaling pathway essential for the arrest is conserved in organisms from Xenopus to mouse and human. A previous gene association study implicated that mutations of human ACSL6 may be related to premature ovarian failure. However, functional roles of ACSL6 in human infertility have yet to be reported. In the present study, we found that triacsin C, a potent and specific inhibitor for ACSL, triggers maturation in Xenopus and mouse oocytes in the absence of hormone, suggesting ACSL activity is required for the oocyte arrest. In Xenopus, acsl1b may fulfill a major role in the process, because inhibition of acsl1b by knocking down its RNA results in abnormal acceleration of oocyte maturation. Such abnormally matured eggs cannot support early embryonic development. Moreover, direct inhibition of protein palmitoylation, which lies downstream of ACSLs, also causes oocyte maturation. Furthermore, palmitoylation of Galpha(s), which is essential for its function, is inhibited when the ACSL activity is blocked by triacsin C in Xenopus. Thus, disruption of ACSL activity causes inhibition of the Galpha(s) signaling pathway in the oocytes, which may result in premature ovarian failure in human.

Fatty acid synthase modulates homeostatic responses to myocardial stress

Fatty acid synthase (FAS) promotes energy storage through de novo lipogenesis and participates in signaling by the nuclear receptor PPARα in noncardiac tissues. To determine if de novo lipogenesis is relevant to cardiac physiology, we generated and characterized FAS knockout in the myocardium (FASKard) mice. FASKard mice develop normally, manifest normal resting heart function, and have normal cardiac PPARα signaling as well as fatty acid oxidation. However, they decompensate with stress. Most die within 1 h of transverse aortic constriction, probably due to arrhythmia. Voltage clamp measurements of FASKard cardiomyocytes show hyperactivation of L-type calcium channel current that could not be reversed with palmitate supplementation. Of the classic regulators of this current, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) but not protein kinase A signaling is activated in FASKard hearts, and knockdown of FAS in cultured cells activates CaMKII. In addition to being intolerant of the stress of acute pressure, FASKard hearts were also intolerant of the stress of aging, reflected as persistent CaMKII hyperactivation, progression to dilatation, and premature death by ∼1 year of age. CaMKII signaling appears to be pathogenic in FASKard hearts because inhibition of its signaling in vivo rescues mice from early mortality after transverse aortic constriction. FAS was also increased in two mechanistically distinct mouse models of heart failure and in the hearts of humans with end stage cardiomyopathy. These data implicate a novel relationship between FAS and calcium signaling in the heart and suggest that FAS induction in stressed myocardium represents a compensatory response to protect cardiomyocytes from pathological calcium flux.

Expression and vitamin D3 regulation of long-chain fatty-acid-CoA ligase 3 in human prostate cancer cells

We found previously that long-chain fatty-acid-CoA ligase 3 (FACL3), a critical enzyme for activation of long-chain fatty acids, was upregulated by 1α, 25(OH)(2)D(3) at an mRNA and enzyme activity levels in prostate cancer cells. Our further study indicated that the FACL3 mediated 1α,25(OH)(2)D(3) inhibition of fatty acid synthase (FAS), which is associated with many cancers, including prostate cancer. In the current study, we investigated an FACL3 protein expression and its regulation by 1α, 25(OH)(2)D(3) and its synthetic analogs EB1089 and CB1093 in prostate cancer cells. The results showed that the expression of an FACL3 protein was upregulated by 1α, 25(OH)(2)D(3), EB1089 and CB1093 in LNCaP cells, consistent with their upregulation of an FACL3 mRNA expression. In addition, the FACL3 expression was found to be markedly low at both mRNA and protein levels in more transformed prostate cancer PC-3 and DU145 cells compared with less transformed LNCaP cells. The data suggest that decreased FACL3 expression might be associated with a more malignant phenotype of prostate cancer.

Anti-atherosclerotic activity of triacsin C, an acyl-CoA synthetase inhibitor

As previously reported, triacsin C, a selective inhibitor of acyl-CoA synthetase, inhibited the synthesis of cholesteryl ester and triacylglycerol in mouse peritoneal macrophages, leading to a reduction of lipid droplets. Therefore, the in vivo efficacy was studied. Low-density lipoprotein receptor-knockout (LDLR-/-) mice were fed a high cholesterol diet (0.15%) for two months to measure the atherogenic areas of the hearts and aortas. When triacsin C was orally administered (10 mg/kg/day), the atherosclerotic areas were significantly reduced by 86% in aorta and 36% in hearts. The results strongly suggested that triacsin C shows anti-atherogenic activity by inhibiting acyl-CoA synthetase activity.

Mode of action of mood stabilizers: is the arachidonic acid cascade a common target?

Bipolar disorder is a major medical, social and economic burden worldwide. However, the mechanisms of action of effective antibipolar disorder drugs remain elusive. In this paper, we review studies using a neuropharmacological approach in unanesthetized rats, combined with kinetic, biochemical and molecular biology techniques, showing that chronic administration of three Food and Drug Administration-approved mood stabilizers (lithium, valproate and carbamazepine) at therapeutically relevant doses, selectively target the brain arachidonic acid (AA) cascade. Whereas chronic lithium and carbamazepine decrease the binding activity of activator protein-2 and in turn the transcription, translation and activity of its AA-selective calcium-dependent phospholipase A(2) gene product, valproate appears to be a non-competitive inhibitor of long-chain acyl-CoA synthetase. The net overlapping effects of the three drugs are decreased turnover of AA but not of docosahexaenoic acid in rat brain phospholipids, and decreased brain cyclooxygenase-2 and prostaglandin E(2). Although these observations support the hypothesis proposed by Rapoport and colleagues that the AA cascade is a common target of mood stabilizers, this hypothesis is not necessarily exclusive of other targets. Targeting the AA cascade with drugs or diet may be a useful therapeutic approach in bipolar disorder, and examining the AA cascade in patients might help in better understanding the disease.

Inhibiting long-chain fatty acyl CoA synthetase does not increase agonist-induced release of arachidonate metabolites from human endothelial cells

BACKGROUND

Triacsin C, a fatty acid analog, inhibits endothelial nitric oxide synthetase (eNOS) palmitoylation, increases nitric oxide synthesis and enhances methacholine-induced relaxation of vascular rings. The experiments presented here tested the hypothesis that triacsin C increases the synthesis of PGI(2) and/or endothelial-derived hyperpolarizing factor.

METHODS

Long-chain fatty acyl CoA synthetase activity (LCFACoAS), agonist-induced prostacyclin synthesis and agonist-induced release of radioactivity in endothelial cells labeled with [(3)H]arachidonic acid were measured in the presence and absence of triacsin C.

RESULTS

Inhibition by triacsin C of palmitoyl CoA formation was significantly greater than inhibition of arachidonoyl CoA formation in solubilized endothelial cell preparations. While 24-hour triacsin C treatment significantly reduced basal 6-keto synthesis, it had no effect on agonist-stimulated synthesis. The release of arachidonic acid metabolites was examined in [(3)H]arachidonate-labeled cells. Triacsin C treatment had no effect on basal or vasopressin-, angiotensin-II-, bradykinin- or ionomycin-induced release of radioactivity, but significantly reduced release in response to isoproterenol or phenylephrine. Expression of neither immunoreactive eNOS nor immunoreactive inducible nitric oxide synthetase (iNOS) was changed by triacsin C treatment, but the fraction of immunoreactive eNOS in the cytoplasm of treated cells was significantly greater as compared to vehicle control cells. Phorbol myristoyl acetate or fenofibrate significantly increased in vitro LCFACoAS activity, and significantly decreased the nitrite/eNOS ratio.

CONCLUSIONS

These data indicate that, while triacsin C can inhibit arachidonoyl CoA synthetase in endothelial cells, it does not increase the availability of endogenous substrate for basal or agonist-induced PGI(2) synthesis, nor does it enhance release of arachidonic acid or its metabolites.