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Latent tuberculosis, caused by dormant Mycobacterium tuberculosis (Mtb), poses a threat to global health through the incubation of undiagnosed infections within the community. Dormant Mtb, which is phenotypically tolerant to antibiotics, accumulates triacylglycerol (TAG) utilizing fatty acids obtained from macrophage lipid droplets. TAG is vital to mycobacteria, serving as a cell envelope component and energy reservoir during latency. TAG synthesis occurs by sequential acylation of glycerol‐3‐phosphate, wherein the second acylation step is catalyzed by acylglycerol‐3‐phosphate acyltransferase (AGPAT), resulting in the production of phosphatidic acid (PA), a precursor for the synthesis of TAG and various phospholipids. Here, we have characterized a putative acyltransferase of Mtb encoded by Rv3816c. We found that Rv3816c has all four characteristic motifs of AGPAT, exists as a membrane‐bound enzyme, and functions as 1‐acylglycerol‐3‐phosphate acyltransferase. The enzyme could transfer the acyl group to acylglycerol‐3‐phosphate (LPA) from monounsaturated fatty acyl‐coenzyme A of chain length 16 or 18 to produce PA. Complementation of Escherichia coli PlsC mutant in vivo by Rv3816c confirmed that it functions as AGPAT. Its active site mutants, H43A and D48A, were incapable of transferring the acyl group to LPA in vitro and were not able to rescue the growth defect of E. coli PlsC mutant in vivo. Identifying Rv3816c as AGPAT and comparing its properties with other AGPAT homologs is not only a step toward understanding the TAG biosynthesis in mycobacteria but has the potential to explore it as a drug target. [ABSTRACT FROM AUTHOR]

Mitochondrial cristae are extraordinarily crowded with proteins, which puts stress on the bilayer organization of lipids. We tested the hypothesis that the high concentration of proteins drives the tafazzin‐catalyzed remodeling of fatty acids in cardiolipin, thereby reducing bilayer stress in the membrane. Specifically, we tested whether protein crowding induces cardiolipin remodeling and whether the lack of cardiolipin remodeling prevents the membrane from accumulating proteins. In vitro, the incorporation of large amounts of proteins into liposomes altered the outcome of the remodeling reaction. In yeast, the concentration of proteins involved in oxidative phosphorylation (OXPHOS) correlated with the cardiolipin composition. Genetic ablation of either remodeling or biosynthesis of cardiolipin caused a substantial drop in the surface density of OXPHOS proteins in the inner membrane of the mouse heart and Drosophila flight muscle mitochondria. Our data suggest that OXPHOS protein crowding induces cardiolipin remodelling and that remodeled cardiolipin supports the high concentration of these proteins in the inner mitochondrial membrane. SYNOPSIS: In mitochondrial cristae, proteins are packaged at uniquely high density, imposing stress on the membrane lipid composition. This work uncovers acyl group remodeling of the membrane phospholipid cardiolipin as a precondition for concentrating oxidative phosphorylation (OXPHOS) proteins in the inner mitochondrial membrane. Protein crowding affects fatty acid remodeling of cardiolipin in vitro.The surface concentration of OXPHOS proteins correlates with the molecular species composition of cardiolipin.Ablation of cardiolipin remodeling or biosynthesis decreases surface concentration of OXPHOS proteins in mice and flies. [ABSTRACT FROM AUTHOR]

SUMMARY: Fatty acid‐derived volatile organic compounds (FA‐VOCs) make significant contributions to tomato (Solanum lycopersicum) fruit flavor and human preferences. Short‐chain FA‐VOCs (C5 and C6) are among the most abundant and important volatile compounds in tomato fruits. The precursors of these volatiles, linoleic acid (18:2) and linolenic acid (18:3), are derived from cleavage of glycerolipids. However, the initial step in synthesis of these FA‐VOCs has not been established. A metabolite‐based genome‐wide association study combined with genetic mapping and functional analysis identified a gene encoding a novel class III lipase family member, Sl‐LIP8, that is associated with accumulation of short‐chain FA‐VOCs in tomato fruit. In vitro assays indicated that Sl‐LIP8 can cleave 18:2 and 18:3 acyl groups from glycerolipids. A CRISPR/Cas9 gene edited Sl‐LIP8 mutant had much lower content of multiple fruit short‐chain FA‐VOCs, validating an important role for this enzyme in the pathway. Sl‐LIP8 RNA abundance was correlated with FA‐VOC content, consistent with transcriptional regulation of the first step in the pathway. Taken together, our work indicates that glycerolipid turnover by Sl‐LIP8 is an important early step in the synthesis of multiple short‐chain FA‐VOCs. Significance Statement: Reduced flavor in modern commercial tomatoes is a major consumer concern. Flavor is a highly complex trait involving many volatile chemicals synthesized via multiple biosynthetic pathways that all contribute to consumer liking. Elaborating their biosynthetic pathways and their regulation is a major step toward flavor improvement. Short chain fatty acid‐derived volatiles make significant contributions to fruit flavor. A metabolite‐based genome‐wide association study combined with genetic mapping and functional analysis identified a gene encoding a class III lipase family member, Sl‐LIP8, that is associated with accumulation of these volatiles in fruit. In vitro and in vivo functional analysis indicates that glycerolipid turnover by Sl‐LIP8 is an important early step in the synthesis of multiple short‐chain FA‐VOCs. [ABSTRACT FROM AUTHOR]

Acyl‐CoA‐binding proteins (ACBPs) are a family of proteins that bind acyl‐CoA esters at a conserved acyl‐CoA‐binding domain. ACBPs maintain intracellular acyl‐CoA pools to regulate lipid metabolism. Here, we report on the structure of rice OsACBP2 in complex with C18:3‐CoA ester. The residues Y33, K34 and K56 of OsACBP2 play a crucial role in binding the CoA group, while residues N23, L27, K52 and Y55 in one molecule of OsACBP2 cooperate with L27, L28, A59 and A62 from another anchoring the fatty acyl group. Multiangle light scattering assays indicate that OsACBP2 binds C18:3‐CoA as a monomer. The first complex structure of a plant ACBP binding with C18:3‐CoA is therefore presented, providing a novel model for the interaction between an acyl‐CoA ester and the acyl‐CoA‐binding domain(s). [ABSTRACT FROM AUTHOR]

Selective helper T cell 1 (Th1) priming agonists are a promising area of investigation for immunotherapeutic treatment of various diseases. α‐galactosylceramide (α‐GalCer, KRN7000), a well‐studied Th1‐polarizer, simultaneously induces helper T cell 2 (Th2)‐type responses, which is a major drawback for its clinical applications. Based on surflex‐docking computation, α‐GalCer‐diol, with added hydroxyl groups in the acyl chain, is designed and synthesized. Structural analyses reveal stronger affinity between α‐GalCer‐diol and cluster of differentiation 1d (CD1d), leading to enhanced antigen presentation by dendritic cells (DCs) and self‐activation, as reflected by tight binding of the T‐cell receptor (TCR)/KRN7000/CD1d ternary complex and elevated production of interleukin 12 (IL‐12) and interferon‐γ (IFN‐γ). Consequently, invariant natural killer T cells (iNKTs) are activated and exhibit an improved Th1‐type cytokine profile ex vivo and in vivo. Different from KRN7000, α‐GalCer‐diol markedly boosts the expansion of the CD11b+ subpopulation and enhances IFN‐γ content in CD11b+ cells. These reinforced Th1‐type responses collectively endow α‐GalCer‐diol more robust antitumor activity in a xenograft animal model using B16‐F10 melanoma cells. Together, the data demonstrate a new mechanism through which α‐GalCer‐diol induces stronger Th1‐type responses by stimulating CD11b+ leukocyte expansion and DC‐conducted CD1d‐restricted and TCR‐mediated iNKT activation. Hence, this study may facilitate the development of novel Th1 priming agonists. [ABSTRACT FROM AUTHOR]

Endocannabinoids are endogenous ligands of the cannabinoid receptors CB1 and CB2. Two arachidonic acid derivatives, arachidonoylethanolamide (anandamide) and 2-arachidonoylglycerol, are considered to be physiologically important endocannabinoids. In the known metabolic pathway in mammals, anandamide and other bioactive N-acylethanolamines, such as palmitoylethanolamide and oleoylethanolamide, are biosynthesized from glycerophospholipids by a combination of Ca2+-dependent N-acyltransferase and N-acyl-phosphatidylethanolamine-hydrolyzing phospholipase D, and are degraded by fatty acid amide hydrolase. However, recent studies have shown the involvement of other enzymes and pathways, which include the members of the tumor suppressor HRASLS family (the phospholipase A/acyltransferase family) functioning as Ca2+-independent N-acyltransferases, N-acyl-phosphatidylethanolamine-hydrolyzing phospholipase D-independent multistep pathways via N-acylated lysophospholipid, and N-acylethanolamine-hydrolyzing acid amidase, a lysosomal enzyme that preferentially hydrolyzes palmitoylethanolamide. Although their physiological significance is poorly understood, these new enzymes/pathways may serve as novel targets for the development of therapeutic drugs. For example, selective N-acylethanolamine-hydrolyzing acid amidase inhibitors are expected to be new anti-inflammatory and analgesic drugs. In this minireview, we focus on advances in the understanding of these enzymes/pathways. In addition, recent findings on 2-arachidonoylglycerol metabolism are described. [ABSTRACT FROM AUTHOR]