title: Mycobacterial phenolic glycolipid synthesis is regulated by cAMP-dependent lysine acylation of FadD22.
abstract: The mycobacterial cell envelope is unique in its chemical composition, and has an important role to play in pathogenesis. Phthiocerol dimycocerosates (PDIMs) and glycosylated phenolphthiocerol dimycocerosates, also known as phenolic glycolipids (PGLs), contribute significantly to the virulence of Mycobacterium tuberculosis. FadD22 is essential for PGL biosynthesis. We have recently shown in vitro that FadD22 is a substrate for lysine acylation by a unique cAMP-dependent, protein lysine acyltransferase found only in mycobacteria. The lysine residue that is acylated is at the active site of FadD22. Therefore, acylation is likely to inhibit FadD22 activity and reduce PGL biosynthesis. Here, we show accumulation of PGLs in a strain of M. bovis BCG deleted for the gene encoding the cAMP-dependent acyltransferase, katbcg, with no change seen in PDIM synthesis. Complementation using KATbcg mutants that are deficient in cAMP-binding or acyltransferase activity shows that PGL accumulation is regulated by cAMP-dependent protein acylation in vivo. Expression of FadD22 and KATbcg mutants in Mycobacterium smegmatis confirmed that FadD22 is a substrate for lysine acylation by KATbcg. We have therefore described a mechanism by which cAMP can regulate mycobacterial virulence as a result of the ability of this second messenger to modulate critical cell wall components that affect the host immune response.
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.|Present address: Indian Institute of Information Technology, Allahabad, India.
authors.forename: Sintu
authors.initials: S
authors.lastname: Samanta
authors.affiliation: School of Biosciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK.
authors.forename: Albel
authors.initials: A
authors.lastname: Singh
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Biswas
authors.affiliation: School of Biosciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK.
authors.forename: Apoorva
authors.initials: A
authors.lastname: Bhatt
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.
authors.forename: Sandhya S
authors.initials: SS
authors.lastname: Visweswariah
mesh_terms: D000215:Acylation; D000942:Antigens, Bacterial / Q000096:biosynthesis; D001426:Bacterial Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006017:Glycolipids / Q000096:biosynthesis*; D008025:Ligases / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism; D000070837:Lysine Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D009163:Mycobacterium bovis / Q000235:genetics* / Q000378:metabolism; D020102:Mycobacterium smegmatis / Q000235:genetics* / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D037521:Virulence Factors / Q000235:genetics
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D006017:Glycolipids; D037521:Virulence Factors; D000242:Cyclic AMP; D000070837:Lysine Acetyltransferases; D008025:Ligases; C550575:FadD22 protein, Mycobacterium tuberculosis; D008239:Lysine