Acylation of glycerolipids in mycobacteria.

We report on the existence of two phosphatidic acid biosynthetic pathways in mycobacteria, a classical one wherein the acylation of the sn-1 position of glycerol-3-phosphate (G3P) precedes that of sn-2 and another wherein acylations proceed in the reverse order. Two unique acyltransferases, PlsM and PlsB2, participate in both pathways and hold the key to the unusual positional distribution of acyl chains typifying mycobacterial glycerolipids wherein unsaturated substituents principally esterify position sn-1 and palmitoyl principally occupies position sn-2. While PlsM selectively transfers a palmitoyl chain to the sn-2 position of G3P and sn-1-lysophosphatidic acid (LPA), PlsB2 preferentially transfers a stearoyl or oleoyl chain to the sn-1 position of G3P and an oleyl chain to sn-2-LPA.

Sortase A-Cleavable CD1d Identifies Sphingomyelins as Major Class of CD1d-Associated Lipids.

CD1d is an atypical MHC class I molecule which binds endogenous and exogenous lipids and can activate natural killer T (NKT) cells through the presentation of lipid antigens. CD1d surveys different cellular compartments including the secretory and the endolysosomal pathway and broadly binds lipids through its two hydrophobic pockets. Purification of the transmembrane protein CD1d for the analysis of bound lipids is technically challenging as the use of detergents releases CD1d-bound lipids.

The 5,6-epoxycholesterol metabolic pathway in breast cancer: Emergence of new pharmacological targets.

Metabolic pathways have emerged as cornerstones in carcinogenic deregulation providing new therapeutic strategies for cancer management. Recently, a new branch of cholesterol metabolism has been discovered involving the biochemical transformation of 5,6-epoxycholesterols (5,6-ECs). The 5,6-ECs are metabolized in breast cancers to the tumour promoter oncosterone whereas, in normal breast tissue, they are metabolized to the tumour suppressor metabolite, dendrogenin A (DDA).

A fast UPLC-HILIC method for an accurate quantification of dendrogenin A in human tissues.

Dendrogenin A (DDA) is a newly-discovered steroidal alkaloid, which remains to date the first ever found in mammals. DDA is a cholesterol metabolites that induces cancer cell differentiation and death in vitro and in vivo, and thus behave like a tumor suppressor metabolite. Preliminary studies performed on 10 patients with estrogen receptor positive breast cancers (ERBC) showed a strong decrease in DDA levels between normal matched tissue and tumors.

Identification of a tumor-promoter cholesterol metabolite in human breast cancers acting through the glucocorticoid receptor.

Breast cancer (BC) remains the primary cause of death from cancer among women worldwide. Cholesterol-5,6-epoxide (5,6-EC) metabolism is deregulated in BC but the molecular origin of this is unknown. Here, we have identified an oncometabolism downstream of 5,6-EC that promotes BC progression independently of estrogen receptor α expression.

Quantitative analysis of the tumor suppressor dendrogenin A using liquid chromatography tandem mass spectrometry.

Dendrogenin A (DDA) was recently identified as a mammalian cholesterol metabolite that displays tumor suppressor and neurostimulating properties at low doses. In breast tumors, DDA levels were found to be decreased compared to normal tissues, evidencing a metabolic deregulation of DDA production in cancers. DDA is an amino-oxysterol that contains three protonatable nitrogen atoms.

Click-chemistry approach to study mycoloylated proteins: Evidence for PorB and PorC porins mycoloylation in Corynebacterium glutamicum.

Protein mycoloylation is a recently identified, new form of protein acylation. This post-translational modification consists in the covalent attachment of mycolic acids residues to serine. Mycolic acids are long chain, α-branched, β-hydroxylated fatty acids that are exclusively found in the cell envelope of Corynebacteriales, a bacterial order that includes important genera such as Mycobacterium, Nocardia or Corynebacterium.

Assembling of the Mycobacterium tuberculosis Cell Wall Core.

The unique cell wall of mycobacteria is essential to their viability and the target of many clinically used anti-tuberculosis drugs and inhibitors under development. Despite intensive efforts to identify the ligase(s) responsible for the covalent attachment of the two major heteropolysaccharides of the mycobacterial cell wall, arabinogalactan (AG) and peptidoglycan (PG), the enzyme or enzymes responsible have remained elusive. We here report on the identification of the two enzymes of Mycobacterium tuberculosis, CpsA1 (Rv3267) and CpsA2 (Rv3484), responsible for this function.

Early-onset Crohn's disease and autoimmunity associated with a variant in CTLA-4.

Objective: IBD is a group of complex, systemic disorders associated with intestinal inflammation and extraintestinal manifestations. Recent studies revealed Mendelian forms of IBD, which contributed significantly to our understanding of disease pathogenesis and the heritability of IBD.

Design: We performed exome sequencing in a family with Crohn's disease (CD) and severe autoimmunity, analysed immune cell phenotype and function in affected and non-affected individuals, and performed in silico and in vitro analyses of cytotoxic T lymphocyte-associated protein 4 (CTLA-4) structure and function.

RND transporters protect Corynebacterium glutamicum from antibiotics by assembling the outer membrane.

Corynebacterium-Mycobacterium-Nocardia (CMN) group are the causative agents of a broad spectrum of diseases in humans. A distinctive feature of these Gram-positive bacteria is the presence of an outer membrane of unique structure and composition. Recently, resistance-nodulation-division (RND) transporters (nicknamed MmpLs, Mycobacterial membrane protein Large) have emerged as major contributors to the biogenesis of the outer membranes in mycobacteria and as promising drug targets.

The cell envelope glycoconjugates of Mycobacterium tuberculosis.

Tuberculosis (TB) remains the second most common cause of death due to a single infectious agent. The cell envelope of Mycobacterium tuberculosis (Mtb), the causative agent of the disease in humans, is a source of unique glycoconjugates and the most distinctive feature of the biology of this organism. It is the basis of much of Mtb pathogenesis and one of the major causes of its intrinsic resistance to chemotherapeutic agents.