Structural and functional features of Rhodococcus ruber lipoarabinomannan

• Published in: Microbiology (Society for General Microbiology) Vol. 149; no. 6; pp. 1437 - 1445
• Main Authors: Gibson, Kevin J. C, Gilleron, Martine, Constant, Patricia, Puzo, Germain, Nigou, Jerome, Besra, Gurdyal S
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.06.2003; Society for General Microbiology; Microbiology Society
• Subjects: Animals; Bacteriology; Biochemistry; Biochemistry, Molecular Biology; Biological and medical sciences; Carbohydrate Sequence; Cell Line; Fundamental and applied biological sciences. Psychology; Humans; Life Sciences; Lipopolysaccharides - chemistry; Lipopolysaccharides - immunology; Lipopolysaccharides - pharmacology; Macrophages - immunology; Macrophages - microbiology; Mice; Microbiology; Miscellaneous; Molecular Sequence Data; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Rhodococcus - chemistry; Rhodococcus - pathogenicity; Rhodococcus ruber; Tumor Necrosis Factor-alpha - biosynthesis; Virulence; Bacteria; Rhodococcus; Actinomycetes
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.26161-0

1 Department of Microbiology and Immunology, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK 2 School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK 3 Department of Molecular Mechanisms of Mycobacterial Infections, Institut de Pharmacologie et de Biologie Structurale, CNRS, UMR 5089, 205 route de Narbonne, 31077 Toulouse cedex 4, France Correspondence Gurdyal S. Besra g.besra{at}bham.ac.uk The genus Rhodococcus is part of the phylogenetic group nocardioform actinomycetes, which also includes the genus Mycobacterium . Members of this phylogenetic group have a characteristic cell envelope structure, which is dominated by various complex lipids. Among these, lipoglycans are of particular interest since mycobacterial lipoarabinomannans are important immunomodulatory molecules that are likely to be involved in the subsequent fate of mycobacterial bacilli once inside phagocytic cells. Rhodococcus ruber is a species closely related to an established opportunistic human pathogen, Rhodococcus equi . This paper reports the isolation and characterization of R. ruber lipoarabinomannan, designated as RruLAM. SDS-PAGE and gas chromatography analyses revealed that RruLAM was of an intermediate size between Mycobacterium tuberculosis lipoarabinomannan and lipomannan. Using a combination of chemical degradation and 1 H, 13 C-NMR experiments, the carbohydrate structure of RruLAM was unambiguously shown to be composed of a linear ( 1 6)-Man p backbone substituted at some O -2 positions by a single t- -Ara f sugar unit. Integration of the anomeric proton signals provided an indication of the degree of branching as approximately 45 %. The RruLAM structure is much simpler than that established for M. tuberculosis lipoarabinomannan but is also different from that determined for the closely related species and opportunistic human pathogen, R. equi . RruLAM was unable to induce the production of TNF- by either human or murine macrophage cell lines, suggesting that more sophisticated structures, such as phosphoinositol capping motifs, are required for such activity. Abbreviations: 1D, one-dimensional; 2D, two-dimensional; APTS, 1-aminopyrene-3,6,8-trisulfonate; Ara f , arabinofuranose; CE-LIF, capillary electrophoresis-laser-induced fluorescence; Gro, glycerol; HMQC, heteronuclear multiple quantum correlation spectroscopy; HOHAHA, homonuclear Hartmann–Hahn spectroscopy; Ins, inositol; IL, interleukin; LAM, lipoarabinomannan; LM, lipomannan; Man p , mannopyranose; ManLAM, LAM with mannosyl caps; NOESY, nuclear Overhauser and exchange spectroscopy; MPI, mannosyl-phosphatidyl- myo -inositol; PILAM, LAM with phosphoinositide caps; PIM, phosphatidyl- myo -inositol mannoside; ReqLAM, lipoglycan of R. equi ; RruLAM, lipoglycan of R. ruber ; t-, terminal; TFA, trifluoroacetic acid; TMS, trimethylsilate; TNF- , tumour necrosis factor K. J. C. G. would like to dedicate this publication to the memory of a close friend, Jonathan D. T. Compton.