Proteomic Analysis of Drug-Resistant Mycobacteria: Co-Evolution of Copper and INH Resistance

Tuberculosis, caused by the pathogen Mycobacterium tuberculosis, is a worldwide public health threat. Mycobacterium tuberculosis is capable of resisting various stresses in host cells, including high levels of ROS and copper ions. To better understand the resistance mechanisms of mycobacteria to copper, we generated a copper-resistant strain of Mycobacterium smegmatis, mc(2)155-Cu from the selection of copper sulfate treated-bacteria. The mc(2)155-Cu strain has a 5-fold higher resistance to copper sulfate and a 2-fold higher resistance to isoniazid (INH) than its parental strain mc(2)155, respectively. Quantitative proteomics was carried out to find differentially expressed proteins between mc(2)155 and mc(2)155-Cu. Among 345 differentially expressed proteins, copper-translocating P-type ATPase was up-regulated, while all other ABC transporters were down-regulated in mc(2)155-Cu, suggesting copper-translocating P-type ATPase plays a crucial role in copper resistance. Results also indicated that the down-regulation of metabolic enzymes and decreases in cellular NAD, FAD, mycothiol, and glutamine levels in mc(2)155-Cu were responsible for its slowing growth rate as compared to mc(2)155. Down-regulation of KatG2 expression in both protein and mRNA levels indicates the co-evolution of copper and INH resistance in copper resistance bacteria, and provides new evidence to understanding of the molecular mechanisms of survival of mycobacteria under stress conditions.