A gene cluster encoding cholesterol catabolism in a soil actinomycete provides insight into Mycobacterium tuberculosis survival in macrophages

Abstract

Rhodococcus sp. strain RHA1, a soil bacterium related to Mycobacterium tuberculosis, degrades an exceptionally broad range of organic compounds. Transcriptomic analysis of cholesterol-grown RHA1 revealed a catabolic pathway predicted to proceed via 4-androstene-3,17-dione and 3,4-dihydroxy-9,10-seconandrost-1,3,5(10)-triene-9,17-dione (3,4-DHSA). Inactivation of each of the hsaC, supAB, and mce4 genes in RHA1 substantiated their roles in cholesterol catabolism. Moreover, the hsaC ؊ mutant accumulated 3,4-DHSA, indicating that HsaCRHA1, formerly annotated as a biphenyl-degrading dioxygenase, catalyzes the oxygenolytic cleavage of steroid ring A. Bioinformatic analyses revealed that 51 rhodococcal genes specifically expressed during growth on cholesterol, including all predicted to specify the catabolism of rings A and B, are conserved within an 82-gene cluster in M. tuberculosis H37Rv and Mycobacterium bovis bacillus Calmette-Gué rin. M. bovis bacillus Calmette-Gué rin grew on cholesterol, and hsaC and kshA were up-regulated under these conditions. Heterologously produced HsaCH37Rv and HsaDH37Rv transformed 3,4-DHSA and its ring-cleaved product, respectively, with apparent specificities Ϸ40-fold higher than for the corresponding biphenyl metabolites. Overall, we annotated 28 RHA1 genes and proposed physiological roles for a similar number of mycobacterial genes. During survival of M. tuberculosis in the macrophage, these genes are specifically expressed, and many appear to be essential. We have delineated a complete suite of genes necessary for microbial steroid degradation, and pathogenic mycobacteria have been shown to catabolize cholesterol. The results suggest that cholesterol metabolism is central to M. tuberculosis's unusual ability to survive in macrophages and provide insights into potential targets for novel therapeutics.catabolic pathway ͉ oxygenase ͉ Rhodococcus ͉ steroid degradation

Towards understanding the functional diversity of cell wall mycolic acids of Mycobacterium tuberculosis

“…In Mycobacterium tuberculosis, this property is manifested as an ability to attract cholesterol into the lipid-free zone that surrounds the cell wall mycolic acid layer [146] and is at the basis of the requirement for host cell membrane cholesterol to enable entry of the bacillus into its host macrophage [139,147]. Besides being essential for the phagocytosis of the bacterium by the macrophage, cholesterol is also used by the bacilli as an energy and carbon source that is critically linked with mycobacterial persistence [148,149] and depends on a sufficient availability of the sterol within the host cell. Mycolic acids may in fact constitute a direct means by which intracellular M.…”

Mce3R, a TetR-type transcriptional repressor, controls the expression of a regulon involved in lipid metabolism in Mycobacterium tuberculosis

“…One spot consisted of a mixture of two proteins (Rv2315c and Rv0234c). Geize et al, 2007). The Rv1936-Rv1941 operon encodes enzymes with probable b-oxidation and redox activities, likely to be involved in lipid metabolism.…”

Integrated multi-omics analyses reveal the biochemical mechanisms and phylogenetic relevance of anaerobic androgen biodegradation in the environment

“…Furthermore, they validated atcA as a competent and reliable biomarker for monitoring anaerobic steroid biodegradation. Androgens serve as intermediates in both aerobic and anaerobic catabolism of cholesterol (Van der Geize et al, 2007;Wang et al, 2013a). For example, in the anaerobic catabolic pathway, Stl.…”