AUTHOR=Becker Katja , Haldimann Klara , Selchow Petra , Reinau Lukas M. , Dal Molin Michael , Sander Peter 

TITLE=Lipoprotein Glycosylation by Protein-O-Mannosyltransferase (MAB_1122c) Contributes to Low Cell Envelope Permeability and Antibiotic Resistance of Mycobacterium abscessus

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02123

DOI=10.3389/fmicb.2017.02123

ISSN=1664-302X

ABSTRACT=<p>Lipoproteins are important components of the mycobacterial cell envelope due to their function in cell wall homeostasis and bacterial virulence. They are post-translationally modified with lipid- and glycosyl-residues in various species and interference with acylation or glycosylation leads to reduced growth and attenuated virulence in <italic>Mycobacterium tuberculosis</italic>. Lipoproteins are also expressed in the emerging and highly drug resistant pathogen <italic>Mycobacterium abscessus</italic> which frequently affects the lungs of patients with chronic pulmonary disease or cystic fibrosis. We investigated post-translational modification, acylation and glycosylation, of heterologously expressed (<italic>M. tuberculosis</italic> LppX and Mpt83) and endogenous (SodC) lipoproteins at the molecular level in <italic>M. abscessus</italic> and identified MAB_1122c as protein <italic>O</italic>-mannosyltransferase (Pmt). Both, heterologous and endogenous lipoproteins carried a characteristic lipid anchor with palmitic acid (C16), palmitoleic acid (C16:1), oleic acid (C18), or tuberculostearic acid (C19) modifications. Multiple hexose-moieties were detected in the <italic>N</italic>-terminal region of the model lipoproteins expressed in <italic>M. abscessus</italic>. Conservation of lipoprotein glycosylation in <italic>M. tuberculosis</italic> and <italic>M. abscessus</italic> was revealed and points toward the existence of an <italic>O</italic>-glycosylation motif or other regulatory mechanisms regarding this post-translational modification. Deletion of MAB_1122c prevented glycosylation and affected susceptibility to specific antibiotics which are large or target peptidoglycan synthesis and to lysozyme. Cell envelope permeability of <italic>M. abscessus</italic> Δ<italic>pmt</italic> was increased and mutant bacteria showed reduced survival inside macrophages. The results provide a link between post-translational modification of lipoproteins and the permeability of the mycobacterial cell envelope which stresses the importance of lipoproteins as components of this complex structure.</p>