Mycobacterium tuberculosis ftsH expression in response to stress and viability.

FtsH is an essential membrane-bound protease that degrades integral membrane proteins as well as cytoplasmic proteins. We show that Mycobacterium tuberculosis (Mtb) ftsH expression levels are upregulated upon exposure to agents that produce reactive oxygen and nitrogen intermediates (ROI and RNI) and growth in macrophages. In partial support of this result is our observation that the Mtb merodiploid overexpressing ftsH shows increased resistance to ROI. ftsH transcript levels are downregulated during stationary phase and starvation. ftsH overexpression strain shows delayed growth and reduced viability in vitro and ex vivo. Finally, we show that the intracellular levels of FtsZ, an essential cell-division protein, are reduced in ftsH-overexpressing strain. Together, our results suggest that Mtb FtsH is a stress-response protein that promotes the pathogen's ability to deal with ROI stress and is possibly involved in the regulation of FtsZ levels.