@article {935,
	title = {Critical roles for lipomannan and lipoarabinomannan in cell wall integrity of mycobacteria and pathogenesis of tuberculosis.},
	journal = {MBio},
	volume = {4},
	year = {2013},
	month = {2013},
	abstract = {<p>ABSTRACT Lipomannan (LM) and lipoarabinomannan (LAM) are mycobacterial glycolipids containing a long mannose polymer. While they are implicated in immune modulations, the significance of LM and LAM as structural components of the mycobacterial cell wall remains unknown. We have previously reported that a branch-forming mannosyltransferase plays a critical role in controlling the sizes of LM and LAM and that deletion or overexpression of this enzyme results in gross changes in LM/LAM structures. Here, we show that such changes in LM/LAM structures have a significant impact on the cell wall integrity of mycobacteria. In Mycobacterium smegmatis, structural defects in LM and LAM resulted in loss of acid-fast staining, increased sensitivity to \&beta;-lactam antibiotics, and faster killing by THP-1 macrophages. Furthermore, equivalent Mycobacterium\&nbsp;tuberculosis mutants became more sensitive to \&beta;-lactams, and one mutant showed attenuated virulence in mice. Our results revealed previously unknown structural roles for LM and LAM and further demonstrated that they are important for the pathogenesis of tuberculosis. IMPORTANCE Tuberculosis (TB) is a global burden, affecting millions of people worldwide. Mycobacterium tuberculosis is a causative agent of TB, and understanding the biology of M.\&nbsp;tuberculosis is essential for tackling this devastating disease. The cell wall of M.\&nbsp;tuberculosis is highly impermeable and plays a protective role in establishing infection. Among the cell wall components, LM and LAM are major glycolipids found in all Mycobacterium species, show various immunomodulatory activities, and have been thought to play roles in TB pathogenesis. However, the roles of LM and LAM as integral parts of the cell wall structure have not been elucidated. Here we show that LM and LAM play critical roles in the integrity of mycobacterial cell wall and the pathogenesis of TB. These findings will now allow us to seek the possibility that the LM/LAM biosynthetic pathway is a chemotherapeutic target.</p>
},
	issn = {2150-7511},
	doi = {10.1128/mBio.00472-12},
	author = {Fukuda, Takeshi and Matsumura, Takayuki and Ato, Manabu and Hamasaki, Maho and Nishiuchi, Yukiko and Murakami, Yoshiko and Maeda, Yusuke and Yoshimori, Tamotsu and Matsumoto, Sohkichi and Kobayashi, Kazuo and Kinoshita, Taroh and Morita, Yasu S}
}
@article {687,
	title = {Inositol lipid metabolism in mycobacteria: biosynthesis and regulatory mechanisms.},
	journal = {Biochim Biophys Acta},
	volume = {1810},
	year = {2011},
	month = {2011 Jun},
	pages = {630-41},
	abstract = {BACKGROUND: The genus Mycobacterium includes a number of medically important pathogens. The cell walls of these bacteria have many unique features, including the abundance of various inositol lipids, such as phosphatidylinositol mannosides (PIMs), lipomannan (LM), and lipoarabinomannan (LAM). The biosynthesis of these lipids is believed to be prime drug targets, and has been clarified in detail over the past several years.

SCOPE OF REVIEW: Here we summarize our current understanding of the inositol lipid metabolism in mycobacteria. We will highlight unsolved issues and future directions especially in the context of metabolic regulation.

MAJOR CONCLUSIONS: Inositol is a building block of phosphatidylinositol (PI), which is further elaborated to become PIMs, LM and LAM. d-myo-inositol 3-phosphate is an intermediate of the de novo inositol synthesis, but it is also the starting substrate for mycothiol synthesis. Controlling the level of d-myo-inositol 3-phosphate appears to be important for maintaining the steady state levels of mycothiol and inositol lipids. Several additional control mechanisms must exist to control the complex biosynthetic pathways of PI, PIMs, LM and LAM. These may include regulatory proteins such as a lipoprotein LpqW, and spatial separation of enzymes, such as the amphipathic PimA mannosyltransferase and later enzymes in the PIMs/LM biosynthetic pathway. Finally, we discuss mechanisms that underlie control of LM/LAM glycan polymer elongation.

GENERAL SIGNIFICANCE: Mycobacteria have evolved a complex network of inositol metabolism. Clarifying its metabolism will not only provide better understanding of bacterial pathogenesis, but also understanding of the evolution and general functions of inositol lipids in nature.},
	keywords = {Inositol, Lipid Metabolism, Lipids, Models, Biological, Mycobacterium, Phosphatidylinositols},
	issn = {0006-3002},
	doi = {10.1016/j.bbagen.2011.03.017},
	author = {Morita, Yasu S and Fukuda, Takeshi and Sena, Chubert B C and Yamaryo-Botte, Yoshiki and McConville, Malcolm J and Kinoshita, Taroh}
}
@article {689,
	title = {Controlled expression of branch-forming mannosyltransferase is critical for mycobacterial lipoarabinomannan biosynthesis.},
	journal = {J Biol Chem},
	volume = {285},
	year = {2010},
	month = {2010 Apr 30},
	pages = {13326-36},
	abstract = {Lipomannan (LM) and lipoarabinomannan (LAM) are phosphatidylinositol-anchored glycans present in the mycobacterial cell wall. In Mycobacterium smegmatis, the mannan core of LM/LAM constitutes a linear chain of 20-25 alpha1,6-mannoses elaborated by 8-9 alpha1,2-monomannose side branches. At least two alpha1,6-mannosyltransferases mediate the linear mannose chain elongation, and one branching alpha1,2-mannosyltransferase (encoded by MSMEG_4247) transfers monomannose branches. An MSMEG_4247 deletion mutant accumulates branchless LAM and interestingly fails to accumulate LM, suggesting an unexpected role of mannose branching for LM synthesis or maintenance. To understand the roles of MSMEG_4247-mediated branching more clearly, we analyzed the MSMEG_4247 deletion mutant in detail. Our study showed that the deletion mutant restored the synthesis of wild-type LM and LAM upon the expression of MSMEG_4247 at wild-type levels. In striking contrast, overexpression of MSMEG_4247 resulted in the accumulation of dwarfed LM/LAM, although monomannose branching was restored. The dwarfed LAM carried a mannan chain less than half the length of wild-type LAM and was elaborated by an arabinan that was about 4 times smaller. Induced overexpression of an elongating alpha1,6-mannosyltransferase competed with the overexpressed branching enzyme, alleviating the dwarfing effect of the branching enzyme. In wild-type cells, LM and LAM decreased in quantity in the stationary phase, and the expression levels of branching and elongating mannosyltransferases were reduced in concert, presumably to avoid producing abnormal LM/LAM. These data suggest that the coordinated expressions of branching and elongating mannosyltransferases are critical for mannan backbone elongation.},
	keywords = {Bacterial Proteins, Cell Wall, Gene Deletion, Lipopolysaccharides, Mannose, Mannosyltransferases, Mycobacterium smegmatis},
	issn = {1083-351X},
	doi = {10.1074/jbc.M109.077297},
	author = {Sena, Chubert B C and Fukuda, Takeshi and Miyanagi, Kana and Matsumoto, Sohkichi and Kobayashi, Kazuo and Murakami, Yoshiko and Maeda, Yusuke and Kinoshita, Taroh and Morita, Yasu S}
}
