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

Robert van der Geize, Katherine Yam, Thomas Heuser, Maarten H. Wilbrink, Hirofumi Hara, Matthew C. Anderton, Edith Sim, Lubbert Dijkhuizen, Julian E. Davies, William W. Mohn*, Lindsay D. Eltis

*Corresponding author for this work

Research output: Contribution to journalArticleAcademic

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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–Guérin. M. bovis bacillus Calmette–Guérin 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 ≈40-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.
Original languageEnglish
Pages (from-to)1947 - 1952
Number of pages6
JournalProceedings of the National Academy of Sciences
Volume104
Issue number6
DOIs
Publication statusPublished - 2007

Keywords

  • steroid degradation
  • Rhodococcus
  • oxygenase
  • catabolic pathway

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