Functional Analysis of the Mycobacterium tuberculosis MprAB Two-Component SignalTransductionSystem

Abstract

The mechanisms utilized by Mycobacterium tuberculosis to establish, maintain, or reactivate from latent infection in the host are largely unknown but likely include genes that mediate adaptation to conditions encountered during persistence. Previously, a two-component signal transduction system, mprAB, was found to be required in M. tuberculosis for establishment and maintenance of persistent infection in a tissue-and stage-specific fashion. To begin to characterize the role of this system in M. tuberculosis physiology and virulence, a functional analysis of the mprA and mprB gene products was initiated. Here, evidence is presented demonstrating that sensor kinase MprB and response regulator MprA function as an intact signal-transducing pair in vitro and in vivo. Sensor kinase MprB can be autophosphorylated, can donate phosphate to MprA, and can act as a phospho-MprA phosphatase in vitro. Correspondingly, response regulator MprA can accept phosphate from MprB or from small phosphodonors including acetyl phosphate. Mutagenesis of residues His249 in MprB and Asp48 in MprA abolished the ability of these proteins to be phosphorylated in vitro. Introduction of these alleles into Mycobacterium bovis BCG attenuated virulence in macrophages in vivo. Together, these results support a role for the mprAB two-component system in M. tuberculosis physiology and pathogenesis. Characterization of two-component signal transduction systems will enhance our understanding of processes regulated by M. tuberculosis during acute and/or persistent infection in the host.Persistent Mycobacterium tuberculosis infections afflict nearly 2 billion people worldwide (31). The combination of M. tuberculosis reactivation in these individuals and subsequent primary infection of immunocompromised hosts unable to control the infection accounts for more than 2.4 million deaths annually due to tuberculosis (34). This disease is the world's leading cause of death due to infection by a single bacterial agent (24). While the majority of individuals latently infected with M. tuberculosis do not undergo reactivation of disease, factors that suppress the host's immune system, including infection with human immunodeficiency virus, steroid therapy, malnutrition, and age, can increase the risk of reactivation tuberculosis to 10% per annum (44). While antitubercular therapeutics are effective in treating individuals with acute primary or reactivated tuberculosis infections, these antibiotics are largely ineffective against M. tuberculosis in the latent stages of infection (40), a poorly understood disease state characterized by little or no bacterial proliferation and the lack of overt disease symptoms. With the continuing increase in human immunodeficiency virus infection in many parts of the world, the emergence of multidrug-resistant isolates of M. tuberculosis (35), and the lack of antitubercular drugs exhibiting activity against organisms during latent infection, new therapeutics targeting persistent bacilli or preventing reactivation are needed.The abili...

Evidence for complex interactions of stress-associated regulons in an mprAB deletion mutant of Mycobacterium tuberculosis

“…TCSs are histidine phosphotransfer systems involved in sensing environmental changes and triggering adaptive responses (Hoch & Varughese, 2001). Studies indicate that MprA is an autoregulatory transcription factor, which is phosphorylated by the histidine kinase MprB (He & Zahrt, 2005;Zahrt et al, 2003). Results of genome-wide transposon mutagenesis suggested that mprB was essential for growth in broth, whereas mprA was nonessential (Sassetti et al, 2003).…”

“…TCSs are histidine phosphotransfer systems involved in sensing environmental changes and triggering adaptive responses (Hoch & Varughese, 2001). Studies indicate that MprA is an autoregulatory transcription factor, which is phosphorylated by the histidine kinase MprB (He & Zahrt, 2005;Zahrt et al, 2003). …”

Modulation of Mycobacterium tuberculosis proliferation by MtrA, an essential two‐component response regulator

“…Of these, only the mtrA-mtrB system is essential (Via et al ., 1996;Zahrt and Deretic, 2000;Parish et al ., 2003a), while others are required under specific growth conditions, namely, mprA-B for maintenance of persistence (Zahrt and Deretic, 2001), devR-S for regulation of hypoxic response (Sherman et al ., 2001;Park et al ., 2003) and prrA-B for intramacrophage growth (Ewann et al ., 2002;. Deletion of regX-sensX , dev R, pho P-R and prrA-B and kdpD-kdp E affects growth and virulence in animal infection models (Perez et al ., 2001;Parish et al ., 2003a,b;Sassetti and Rubin, 2003;Zahrt et al ., 2003;Malhotra et al ., 2004;Roberts et al ., 2004;Tyagi and Sharma, 2004;Asensio et al ., 2006). The functional roles played by many of these response regulators, and the environmental signals they respond to, are poorly understood.…”

Cross talk between DevS sensor kinase homologue, Rv2027c, and DevR response regulator of Mycobacterium tuberculosis

“…These systems use transient phosphorylation of the sensory and regulatory proteins at conserved residues for transducing extracellular or intracellular signals, thereby leading to an appropriate cellular response [2]. Such phosphorylation-based signalling has been established for five of eleven systems in M. tuberculosis, RegX3-SenX3 [3], TrcR-TrcS [4], MprA-MprB [5], PrrA-PrrB [6] and DevR-DevS (Rv3133c-Rv3132c/DosR-DosS) [7]. The genes encoding two-component systems are generally located adjacent to each other and are also coexpressed.…”