Project description:S-acylation is a crucial post-translational modification that transfers long-chain fatty acids to cysteine residues within proteins, but the fatty acid specificity of this modification in plants remains entirely unknown. In this study, we established a robust system for characterizing the fatty acid specificity of protein S-acylation in plant cells via click chemistry. We applied this approach to identify various S-acylated proteins modified by myristic acid, palmitic acid, or stearic acid in Arabidopsis through chemical proteomics. Additionally, we investigated the preferences for different fatty acid chain lengths among 24 protein S-acyltransferases and examined how elevated temperatures influence the utilization of stearic acid. Functional analyses indicated that specific fatty acids regulate the distribution of protein substrates across distinct membrane regions. Our current research will pave the way for advancements in the field of plant protein S-acylation, providing a powerful tool and valuable resource for future studies involving Arabidopsis and other plant species.
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: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: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: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:Protein lipidation is a critical post-translational modification, but the relationship between the fine structure of fatty acids (FAs) and the specificity of lipidation remains largely unexplored. Here, we developed an isomer-resolved enzyme-centered chemoproteomic strategy to elucidate the intricate relationships between the key players involved in the lipidation modification process. By synthesizing alkyne-tagged FA isomer probes in combination with zDHHC enzyme overexpression and quantitative proteomics, we revealed at the proteomic level how minor isomeric differences in FAs affect their modification. Protein lipidation was shown to have a marked specificity for the C=C bond isomerism, and the comprehensive network between FA isomers, zDHHC enzymes, and S-acylated proteins was mapped. Furthermore, the isomeric selectivity and the spatial binding characteristics of autoacylation intermediates were elucidated, suggesting the molecular determinants governing this specificity. This study provides deep insights into the molecular basis of protein lipidation modification.
Project description:Numerous proteins synthesized in cells ranging from bacteria to humans have to be posttranslationally acylated to become biologically active. Bacterial Repeats in ToXin (RTX) cytolysins form a prominent group of proteins that are synthesized as inactive protoxins and undergo a posttranslational acylation on ε-amino groups of two internal conserved lysine residues by co-expressed toxin-activating acyltransferases. We investigated how the chemical nature, position and number of bound acyl chains govern the activities of Bordetella pertussis adenylate cyclase toxin (CyaA), Escherichia coli α-hemolysin (HlyA) and Kingella kingae cytotoxin (RtxA). The three protoxins were acylated in the same E. coli cell background by either of the CyaC, HlyC and RtxC acyltransferases. The results revealed that the acyltransferase itself selects from the acyl-ACP pool of the producing bacterium the type of the acyl chain of adapted length to be covalently linked to the protoxin. The acyltransferase also selects whether both or only one of two conserved lysine residues of the protoxin will be posttranslationally acylated. Functional assays then revealed that RtxA has to be modified by 14-carbon fatty acyl chains to be biologically active, while HlyA remains active also when modified by 16-carbon acyl chains and CyaA is activated exclusively by 16-carbon acyl chains. These results suggest a structural adaptation of the toxin molecules to the length of the acyl chains used for modification of their crucial acylated lysine residue in the second, more conserved acylation site
Project description:Efficient nucleic acid enrichment is pivotal for deciphering epigenetic modifications and disease biomarkers, yet current methods are constrained by insufficient specificity, poor versatility, and high costs. We developed a universal strategy named ‘Click-IP-Seq’ by leveraging the high-affinity binding between Protein G and Fc region of DBCO-modified IgG. This enabled the directional conjugation of DBCO-IgG with azide-modified nucleic acids via copper-free strain-promoted azide-alkyne cycloaddition (SPAAC) click chemistry, achieving specific capture and enrichment of modified nucleic acids. Firstly, this method efficiently enriched two major DNA modifications, 8-oxo-7,8-dihydroguanine (8-oxo-dG) and 5-hydroxymethylcytosine (5hmC) in model DNA systems. Then, genome-wide distribution of 8-oxodG from human cells and tissues align with previously reports. Finally, employing ‘Click-IP-Seq’, we performed the first comprehensive analysis of 8-oxo-dG spatial distribution and associated biological functions in human colorectal carcinoma tissues. This technology provides a high-specificity and versatile enrichment platform for nucleic acid modifications, which is expected to promote the application of cancer molecular diagnosis.