Project description:Protein lipidation plays critical roles in regulating protein function and localization. However, the chemical diversity and specificity of fatty acyl group utilization have not been investigated using untargeted approaches, and it is unclear to what extent structures and biosynthetic origins of S-acyl moieties differ from N- and O-fatty acylation. Here, we show that fatty acylation patterns in Caenorhabditis elegans differ markedly between different amino acid residues. Hydroxylamine capture revealed predominant cysteine S-acylation with 15-methylhexadecanoic acid (isoC17:0), a monomethyl branched-chain fatty acid (mmBCFA) derived from endogenous leucine catabolism. In contrast, enzymatic protein hydrolysis showed that N-terminal glycine was acylated almost exclusively with straight-chain myristic acid, whereas lysine was acylated preferentially with two different mmBCFAs and serine was acylated promiscuously with a broad range of fatty acids, including eicosapentaenoic acid. Global profiling of fatty acylated proteins using a set of click chemistry-capable alkyne probes for branched- and straight-chain fatty acids uncovered 1,013 S-acylated proteins and 510 hydroxylamine-resistant N- or O-acylated proteins. Subsets of S-acylated proteins were labeled almost exclusively by either a branched-chain or a straight-chain probe, demonstrating acylation specificity at the protein level. Acylation specificity was confirmed for selected examples, including the S-acyltransferase DHHC-10. Last, homology searches for the identified acylated proteins revealed a high degree of conservation of acylation site patterns across metazoa. Our results show that protein fatty acylation patterns integrate distinct branches of lipid metabolism in a residue- and protein-specific manner, providing a basis for mechanistic studies at both the amino acid and protein levels.
Project description:Dietary unsaturated fatty acids beneficially affect human health, in part by modulating the immune system, but the mechanism is not completely understood. Given that unsaturated fatty acids have been shown to be covalently incorporated into a small subset of proteins, we designed three alkyne-tagged chemical reporters of unsaturated fatty acids, alk-16:1, alk-17:1 and alk-18:1, to explore the generality and diversity of this protein modification. Following cell lysis, proteins labelled with the reporters could be captured by azido-functionalized reagents via CuAAC for fluorescence detection or enrichment for proteomics analysis. These reporters label many proteins in mammalian cells and can be incorporated site-specifically, notably on Cys residues. Quantitative proteomics analysis (n= 4 biological replicates) of LPS/IFN-gamma stimulated RAW264.7 labelled with oleic acid (control), alk-16 (palmitic acid chemical reporter), alk-16:1, alk-17:1 and alk-18:1, revealed that unsaturated fatty acids modify similar protein targets to saturated fatty acids, including several immune proteins. Interestingly, some proteins can be differentially labeled with unsaturated and saturated fatty acid.
Project description:Mammalian fatty acid synthase (FASN) is a lipogenic enzyme that catalyzes the formation of the long chain saturated fatty acid palmitate from acetyl and malonyl CoA in the presence of NADPH. Mammalian cells acquire fatty acids through dietary sources or through FASN. Although most mammalian cells express FASN at low levels, it is upregulated in cancers and during replication of many viruses. The precise role of FASN in disease pathogenesis is poorly understood, and whether de novo fatty acid synthesis contributes to host or viral protein acylation has been traditionally difficult to study. We describe a cell permeable, click-chemistry compatible alkynyl-acetate analog (5-Hexynoic acid, or "Alk-4") that functions as a reporter of FASN-dependent protein acylation. Alk-4 metabolic labeling enabled biotin-based purification and identification of more than 200 FASN-dependent acylated cellular proteins. Alk-4 also labeled the palmitoylated host protein IFITM3 (Interferon inducible transmembrane protein-3), a restriction factor for Influenza, and the myristoylated HIV-1 MA (Matrix) protein. Thus, Alk-4 is a useful bioorthogonal tool to selectively probe FASN-mediated protein acylation in normal and diseased states.
Project description:Intermediary metabolites and flux through various pathways have emerged as key determinants of post-translational modifications. Independently, dynamic fluctuations in their concentrations are known to drive cellular energetics in a bi-directional manner. Notably, intracellular fatty acid pools that drastically change during fed and fasted states act as precursors for both ATP production and fatty acylation of proteins. Protein fatty acylation is well regarded for its role in regulating structure and functions of diverse proteins; however, the effect of intracellular concentrations of fatty acids on protein modification is less understood. In this regard, we unequivocally demonstrate that metabolic contexts, viz. fed and fasted states, dictate the extent of global fatty acylation. Moreover, we show that presence or absence of glucose that influences cellular and mitochondrial uptake/utilization of fatty acids and affects palmitoylation and oleoylation, which is consistent with their intracellular abundance in fed and fasted states. Employing complementary approaches including click-chemistry, lipidomics, and imaging, we show the top-down control of cellular metabolic state. Importantly, our results establish the crucial role of mitochondria and retrograde signaling components like SIRT4, AMPK, and mTOR in orchestrating protein fatty acylation at a whole cell level. Specifically, pharmacogenetic perturbations that alter either mitochondrial functions and/or retrograde signaling affect protein fatty acylation. Besides illustrating the cross-talk between carbohydrate and lipid metabolism in mediating bulk post-translational modification, our findings also highlight the involvement of mitochondrial energetics.
Project description:The advances in chemical proteomics have significantly expanded our understanding of the diversity and abundance of fatty-acylated proteins in eukaryotes, and reveal novel functions for these lipid protein modifications. Nonetheless, quantitative comparative proteomic analysis of fatty-acylated proteins in different cellular states is still challenging. To address these limitations, we systematically evaluated different proteomic methods (alk-16 chemical reporter and acyl-RAC) and established robust conditions to selectively and quantitatively profile fatty-acylated proteins in mammalian cells. Using a combination of metabolic labeling with fatty acid chemical reporters, selective chemical enrichment and label-free proteomics, we performed a quantitative analysis of fatty-acylated proteins in naïve and activated macrophages. These studies revealed novel fatty-acylated proteins associated with host immunity that are differently expressed and lipid-modified in different cellular states.
Project description:Given our laboratory interest in IFITM3 S-fatty-acylation and antiviral activity, we sought to directly characterize fatty acids that are covalently attached to the Cys residues of IFITM3. IFITM3 comprises two S-fatty-acylation sites (C71 and C72) in proximity of a intramembrane domain, and another site adjacent to a transmembrane domain (C105). We directly identified the S-fatty-acylation sites of IFITM3 and further demonstrated that the highly conserved Cys residues are primarily modified by palmitic acid.
Project description:Given our laboratory interest in IFITM3 S-fatty-acylation and antiviral activity, we sought to directly characterize fatty acids that are covalently attached to the Cys residues of IFITM3. IFITM3 comprises two S-fatty-acylation sites (C71 and C72) in proximity of a intramembrane domain, and another site adjacent to a transmembrane domain (C105). We directly identified the S-fatty-acylation sites of IFITM3, and further demonstrated that the highly conserved Cys residues are primarily modified by palmitic acid.
Project description:The Bone Morphogenetic Proteins (BMPs) are secreted peptide ligands of the Transforming Growth Factor beta (TGF-β) family, initially identified for their roles in development and differentiation across animal species. They are now increasingly recognized for their roles in physiology and infectious disease. In the nematode Caenorhabditis elegans, the BMP ligand DBL-1 controls fat metabolism and immune response, in addition to its roles in body size regulation and development. DBL-1 regulates classical aspects of innate immunity, including the induction of anti-microbial peptides. We theorized that BMP-dependent regulation of fat metabolism could also promote resilience against microbial pathogens. We found that exposure to a bacterial pathogen alters total fat stores, lipid droplet dynamics, and lipid metabolism gene expression in a BMP-dependent manner. We further showed that fatty acid desaturation plays a major role in survival on a bacterial pathogen, while fatty acid β-oxidation plays a more minor role. We conclude that C. elegans mobilizes fatty acid metabolism in response to pathogen exposure to promote survival. Our investigation provides a framework to study potential metabolic interventions that could support therapeutics that are complementary to antibiotic strategies.
Project description:TEAD transcription factors are responsible for the transcriptional output of Hippo signalling1,2. TEAD activity is primarily regulated by phosphorylation of its coactivators YAP and TAZ3,4. In addition, cysteine palmitoylation has recently been shown to regulate TEAD activity5,6. Here, we report lysine long-chain fatty acylation as a novel posttranslational modification of TEADs. Lysine fatty acylation occurs spontaneously via intramolecular transfer of acyl groups from the proximal acylated cysteine residue. Lysine fatty acylation, like cysteine palmitoylation, contributes to the transcriptional activity of TEADs by enhancing the interaction with YAP and TAZ, but it is more stable than cysteine acylation, suggesting that the lysine fatty-acylated TEAD acts as a “stable active form”. Significantly, lysine fatty acylation of TEAD increased upon Hippo signalling activation, despite a decrease in cysteine acylation. Our results provide new insight into the role of fatty acyl modifications in the regulation of TEAD activity.
Project description:Early-life malnutrition increases adult disease risk in humans, but the causal changes in gene regulation, signaling, and metabolism are unclear. In the roundworm Caenorhabditis elegans, early-life starvation causes well-fed larvae to develop germline tumors and other gonad abnormalities as adults. Furthermore, reduced insulin/IGF signaling (IIS) during larval development suppresses these starvation-induced abnormalities. How early-life starvation and IIS affect adult pathology is unknown. We show that early-life starvation has pervasive effects on adult gene expression that are largely reversed by reduced IIS following recovery from starvation. Early-life starvation increases adult fatty-acid synthetase fasn-1 expression in daf-2 IIS receptor-dependent fashion, and fasn-1/FASN promotes starvation-induced abnormalities. Lipidomic analysis reveals increased levels of phosphatidylcholine in adults subjected to early-life starvation, and supplementation with unsaturated phosphatidylcholine during development suppresses starvation-induced abnormalities. Genetic analysis of fatty-acid desaturases reveals positive and negative effects of desaturation on development of starvation-induced abnormalities. In particular, the delta 3 fatty-acid desaturase fat-1 and the delta 5 fatty-acid desaturase fat-4 inhibit and promote development of abnormalities, respectively. fat-4 is epistatic to fat-1, suggesting that arachidonic acid, or lipids that contain it, promotes development of starvation-induced abnormalities. This work shows that early-life starvation and IIS converge on regulation of adult lipid metabolism, affecting stem-cell proliferation, tumor formation, and additional adult pathologies.