Lipidomics analysis of long-chain fatty acyl-coenzyme As in liver, brain, muscle and adipose tissue by liquid chromatography/tandem mass spectrometry

Competition for cysteine acylation by C16:0 and C18:0 derived lipids is a global phenomenon in the proteome

S-acylation is a reversible posttranslational protein modification consisting of attachment of a fatty acid to a cysteine via a thioester bond. Research over the last few years has shown that a variety of different fatty acids, such as palmitic acid (C16:0), stearate (C18:0), or oleate (C18:1), are used in cells to S-acylate proteins. We recently showed that GNAI proteins can be acylated on a single residue, Cys3, with either C16:0 or C18:1, and that the relative proportion of acylation with these fatty acids depends on the level of the respective fatty acid in the cell's environment. This has functional consequences for GNAI proteins, with the identity of the acylating fatty acid affecting the subcellular localization of GNAIs. Unclear is whether this competitive acylation is specific to GNAI proteins or a more general phenomenon in the proteome. We perform here a proteome screen to identify proteins acylated with different fatty acids. We identify 218 proteins acylated with C16:0 and 308 proteins acylated with C18-lipids, thereby uncovering novel targets of acylation. We find that most proteins that can be acylated by C16:0 can also be acylated with C18-fatty acids. For proteins with more than one acylation site, we find that this competitive acylation occurs on each individual cysteine residue. This raises the possibility that the function of many different proteins can be regulated by the lipid environment via differential S-acylation.

Stearic acid blunts growth-factor signaling via oleoylation of GNAI proteins

Covalent attachment of C16:0 to proteins (palmitoylation) regulates protein function. Proteins are also S-acylated by other fatty acids including C18:0. Whether protein acylation with different fatty acids has different functional outcomes is not well studied. We show here that C18:0 (stearate) and C18:1 (oleate) compete with C16:0 to S-acylate Cys3 of GNAI proteins. C18:0 becomes desaturated so that C18:0 and C18:1 both cause S-oleoylation of GNAI. Exposure of cells to C16:0 or C18:0 shifts GNAI acylation towards palmitoylation or oleoylation, respectively. Oleoylation causes GNAI proteins to shift out of cell membrane detergent-resistant fractions where they potentiate EGFR signaling. Consequently, exposure of cells to C18:0 reduces recruitment of Gab1 to EGFR and reduces AKT activation. This provides a molecular mechanism for the anti-tumor effects of C18:0, uncovers a mechanistic link how metabolites affect cell signaling, and provides evidence that the identity of the fatty acid acylating a protein can have functional consequences.

A Ratiometric Fluorescent Biosensor Reveals Dynamic Regulation of Long-Chain Fatty Acyl-CoA Esters Metabolism

Despite increasing awareness of the biological impacts of long-chain fatty acyl-CoA esters (LCACoAs), our knowledge about the subcellular distribution and regulatory functions of these acyl-CoA molecules is limited by a lack of methods for detecting LCACoAs in living cells. Here, we report development of a genetically encoded fluorescent sensor that enables ratiometric quantification of LCACoAs in living cells and subcellular compartments. We demonstrate how this FadR-cpYFP fusion "LACSer sensor" undergoes LCACoA-induced conformational changes reflected in easily detectable fluorescence responses, and show proof-of-concept for real-time monitoring of LCACoAs in human cells. Subsequently, we applied LACSer in scientific studies investigating how disruption of ACSL enzymes differentially reduces cytosolic and mitochondrial LCACoA levels, and show how genetic disruption of an acyl-CoA binding protein (ACBP) alters mitochondrial accumulation of LCACoAs.

Targeted Profiling of Short-, Medium-, and Long-Chain Fatty Acyl-Coenzyme As in Biological Samples by Phosphate Methylation Coupled to Liquid Chromatography-Tandem Mass Spectrometry

Fatty acyl-coenzyme As (acyl-CoAs) are of central importance in lipid metabolism pathways. Short-chain acyl-CoAs are usually part of metabolomics, and medium- to (very) long-chain acyl-CoAs are focus of lipidomics studies. However, owing to the specific complex and amphiphilic nature contributed by fatty acyl chains and hydrophilic CoA moiety, lipidomic analysis of acyl-CoAs is still challenging, especially in terms of sample preparation and chromatographic coverage. In this work, we propose a derivatization strategy of acyl-CoAs based on phosphate methylation. After derivatization, full coverage (from free CoA to C25:0-CoA) and good peak shape in liquid chromatography were achieved. At the same time, analyte loss due to the high affinity of phosphate groups to glass and metallic surfaces was resolved, which is beneficial for routine analysis in large-scale lipidomics studies. A sample preparation method based on mixed-mode SPE was developed to optimize extraction recoveries and allow optimal integration of the derivatization process in the analytical workflow. LC-MS/MS was performed with targeted data acquisition by SRM transitions, which were constructed based on similar fragmentation rules observed for all methylated acyl-CoAs. To achieve accurate quantification, uniformly ¹³C-labeled metabolite extract from yeast cells was taken as internal standards. Odd-chain and stable isotope-labeled acyl-CoAs were used as surrogate calibrants in the same matrix. LOQs were between 16.9 nM (short-chain acyl-CoAs) and 4.2 nM (very-long-chain acyl-CoAs). This method was validated in cultured cells and was applied in HeLa cells and human platelets of coronary artery disease patients. It revealed distinct acyl-CoA profiles in HeLa cells and platelets. The results showed that this method can effectively detect acyl-CoAs in biological samples. Considering their central importance in many de novo lipid biosynthesis and remodeling processes, this targeted method offers a valid foundation for future lipidomics analysis of acyl-CoA profiles in biological samples, particularly those concerning metabolic syndrome.

A robust, integrated platform for comprehensive analyses of acyl-coenzyme As and acyl-carnitines revealed chain length-dependent disparity in fatty acyl metabolic fates across Drosophila development

Acyl-coenzyme A thioesters (acyl-CoAs) denote a key class of intermediary metabolites that lies at the hub of major metabolic pathways. The great diversity in polarity between short- and long-chain acyl-CoAs makes it technically challenging to cover an inclusive range of acyl-CoAs within a single method. Levels of acyl-carnitines, which function to convey fatty acyls into mitochondria matrix for β-oxidation, indicate the efficiency of mitochondrial import and utilization of corresponding acyl-CoAs. Herein, we report a robust, integrated platform to allow simultaneous quantitation of endogenous acyl-CoAs and acyl-carnitines. Using this method, we monitored changes in intermediary lipid profiles across Drosophila development under control (ND) and high-fat diet (HFD). We observed specific accumulations of medium-chain (C8-C12) and long-chain (≥C16) acyl-carnitines distinct to L3 larval and pupal stages, respectively. These observations suggested development-specific, chain length-dependent disparity in metabolic fates of acyl-CoAs across Drosophila development, which was validated by deploying the same platform to monitor isotope incorporation introduced from labelled 12:0 and 16:0 fatty acids into extra- and intra-mitochondrial acyl-CoA pools. We found that pupal mitochondria preferentially import and oxidise C12:0-CoAs (accumulated as C12:0-carnitines in L3 stage) over C16:0-CoAs. Preferential oxidation of medium-chain acyl-CoAs limits mitochondrial utilization of long-chain acyl-CoAs (C16-C18), leading to pupal-specific accumulation of long-chain acyl-carnitines mediated by enhanced CPT1-6A activity. HFD skewed C16:0-CoAs towards catabolism over anabolism in pupa, thereby adversely affecting overall development. Our developed platform emphasizes the importance of integrating biological knowledge in the design of pathway-oriented platforms to derive maximal physiological insights from analysis of complex biological systems.

Mass spectrometry-based determination of lipids and small molecules composing adipose tissue with a focus on brown adipose tissue

Adipose tissue has been the subject of research for a very long time. Many studies perform a comprehensive analysis of different types of adipose tissue with an emphasis on brown adipose tissue. Mass spectrometry-based approaches are particularly useful in the exploration not only of the metabolic composition of adipose tissue but also its function. In the presented review, a complex and critical overview of publications devoted to the analysis of adipose tissue by means of mass spectrometry was performed. Detailed investigation of analytical aspects related to either untargeted or targeted analysis of adipose tissue was performed, leading to the formation of a collection of hints at the available analytical methods. Moreover, a profound analysis of the metabolic composition of brown adipose tissue was performed. Brown adipose tissue metabolome was characterized on structural and functional levels, providing information about its exact metabolic composition but also connecting these molecules and placing them into biochemical pathways. All our work resulted in a very broad picture of the analysis of adipose tissue, starting from the analytical aspects and finishing on the current knowledge about its composition.

Revelation of Acyl Double Bond Positions on Fatty Acyl Coenzyme A Esters by MALDI/TOF Mass Spectrometry

Fatty acyl coenzyme A esters (FA-CoAs) are important crossroad intermediates in lipid catabolism and anabolism, and the structures are complicated. Several mass spectrometric approaches have been previously described to elucidate their structures. However, a direct mass spectrometric approach toward a complete identification of the molecule, including the location of unsaturated bond(s) in the fatty acid chain has not been reported. In this study, we applied a simple MALDI/TOF mass spectrometric method to a near-complete characterization of long-chain FA-CoAs, including the location(s) of the double bond in the fatty acyl chain, and the common structural features that recognize FA-CoAs. Negative ion mass spectra of saturated, monounsaturated, and polyunsaturated FA-CoAs were acquired with a MALDI/TOF mass spectrometer using 2,5-dihydroxybenzoic acid as the matrix and ionized with a laser fluence two folds of the threshold to induce the in-source fragmentation (ISF) of the analytes. The resulting ISF spectra contained fragment ions arising from specific cleavages of the C-C bond immediate adjacent to the acyl double-bond. This structural feature affords locating the double-bond position(s) of the fatty acyl substituent. Thereby, positional isomer such as 18:3(n - 3) and 18:3(n - 6) FA-CoA can be differentiated without applying tandem mass spectrometry.

Considerations for mass spectrometry-based multi-omic analysis of clinical samples

Introduction: The role of mass spectrometry in biomolecule analysis has become paramount over the last several decades ranging in the analysis across model systems and human specimens. Accordingly, the presence of mass spectrometers in clinical laboratories has also expanded alongside the number of researchers investigating the protein, lipid, and metabolite composition of an array of biospecimens. With this increase in the number of omic investigations, it is important to consider the entire experimental strategy from sample collection and storage, data collection and analysis.Areas covered: In this short review, we outline considerations for working with clinical (e.g. human) specimens including blood, urine, and cerebrospinal fluid, with emphasis on sample handling, profiling composition, targeted measurements and relevance to disease. Discussions of integrated genomic or transcriptomic datasets are not included. A brief commentary is also provided regarding new technologies with clinical relevance.Expert opinion: The role of mass spectrometry to investigate clinically related specimens is on the rise and the ability to integrate multiple omics datasets from mass spectrometry measurements will be crucial to further understanding human health and disease.

Variant analysis of PEX11B gene from a family with peroxisome biogenesis disorder 14B by whole exome sequencing

BACKGROUND

Peroxisome biogenesis disorder 14B (PBD14B) is an autosomal recessive peroxisome biogenesis disorder characterized clinically by mild intellectual disability, congenital cataracts, progressive hearing loss, and polyneuropathy peroxisome biogenesis disorders are genetically heterogeneous group of disorders caused by biallelic mutations in peroxin (PEX) genes.

METHODOLOGY/LABORATORY EXAMINATION

DNA of the family was extracted and sequenced by whole exome sequencing. The results were validated with Sanger sequencing analyzed with Bioinformatics software.

RESULTS

Sequencing result showed that the patient has carried a homozygous variant of c.277C>T of the PEX11B gene. The patient's brother has carried a homozygous variant of c.277C>T of the PEX11B gene and their variants of c.277C>T of the PEX11B gene were inherited, respectively, from his mother and father.

DISCUSSION AND CONCLUSION

The homozygous variant of c.277C>T of the PEX11B gene probably underlie the disease in this child and her brother.

Comprehensive Analysis of Short-, Medium-, and Long-Chain Acyl-Coenzyme A by Online Two-Dimensional Liquid Chromatography/Mass Spectrometry

Acyl-coenzyme A (CoA) is a pivotal metabolic intermediate in numerous biological processes. However, comprehensive analysis of acyl-CoAs is still challenging as the properties of acyl-CoAs greatly vary with different carbon chains. Here, we designed a two-dimensional liquid chromatography method coupled with high-resolution mass spectrometry (2D LC/HRMS) to cover all short-, medium-, and long-chain acyl-CoAs within one analytical run. Complex acyl-CoAs were separated into two fractions according to their acyl chains by the first dimensional prefractionation. Then, two fractions containing short-chain acyl-CoAs or medium- and long-chain acyl-CoAs were further separated by the two parallel columns in the second dimension. Nineteen representative standards were chosen to optimize the analytical conditions of the 2D LC/HRMS method. Resolution and sensitivity were demonstrated to be improved greatly, and lowly abundant acyl-CoAs and acyl-CoA isomers could be detected and distinguished. By using the 2D LC/HRMS method, 90 acyl-CoAs (including 21 acyl-dephospho-CoAs) were identified from liver extracts, which indicated that our method was one of the most powerful approaches for obtaining comprehensive profiling of acyl-CoAs so far. The method was further employed in the metabolomics study of malignant glioma cells with an isocitrate dehydrogenase 1 (IDH1) mutation to explore their metabolic differences. A total of 46 acyl-CoAs (including 2 acyl-dephospho-CoAs) were detected, and 12 of them were dysregulated in glioma cells with the IDH1 mutation. These results demonstrated the practicability and the superiority of the established method. Therefore, the 2D LC/HRMS method provides a robust and reproducible approach to the comprehensive analysis of acyl-CoAs in tissues, cells, and other biological samples.