Positive and Negative Regulation of Glycerol Utilization by the c-di-GMP Binding Protein PlzA in Borrelia burgdorferi

Abstract

, the causative agent of Lyme disease, encounters two disparate host environments during its enzootic life cycle, ticks and mammalian hosts. has a small genome that encodes a streamlined cyclic dimeric GMP (c-di-GMP) signaling system comprising a single diguanylate cyclase, Rrp1, and two phosphodiesterases. This system is essential for spirochete survival in ticks, in part because it controls the expression of the operon involved in glycerol utilization. In this study, we showed that a c-di-GMP receptor, PlzA, functions as both a positive and a negative regulator for expression. Deletion of or mutation in that impaired c-di-GMP binding abolished expression. On the other hand, overexpression of resulted in repression, which could be rescued by simultaneous overexpression of overexpression in the mutant, which is devoid of c-di-GMP, or overexpression of a mutant incapable of c-di-GMP binding further enhanced repression. Combined results suggest that c-di-GMP-bound PlzA functions as a positive regulator, whereas ligand-free PlzA acts as a negative regulator for expression. Thus, PlzA of with a streamlined c-di-GMP signaling system not only controls multiple targets, as previously envisioned, but has also evolved different modes of action. The Lyme disease pathogen, , has a simple cyclic dimeric GMP (c-di-GMP) signaling system essential for adaptation of the pathogen to the complicated tick environment. The c-di-GMP effector of, PlzA, has been shown to regulate multiple cellular processes, including motility, osmolality sensing, and nutrient utilization. The findings of this study demonstrate that PlzA not only controls multiple targets but also has different functional modalities, allowing it to act as both positive and negative regulator of the operon expression. This work highlights how bacteria with a small genome can compensate for the limited regulatory repertoire by increasing the complexity of targets and modes of action in their regulatory proteins.

The Borrelia burgdorferi Adenylate Cyclase, CyaB, Is Important for Virulence Factor Production and Mammalian Infection

“…cAMP is used by numerous bacterial pathogens to alter both the host and pathogen at the level of posttranscriptional regulation for signal reception, signal transduction, AC activity, virulence gene regulation, resistance to oxidative stress, and persistence (Molina-Quiroz et al, 2018). It is well documented that B. burgdorferi utilizes cyclic dinucleotides during the tick and mammalian stages of pathogenesis to modulate the necessary gene regulation for its response to environmental pressures; therefore, it is plausible that it also relies on cyclic nucleotides for regulation (Rogers et al, 2009;He et al, 2011;Ye et al, 2014;Savage et al, 2015;Melissa J. Caimano et al, 2015;Zhang et al, 2018). It is important to understand the strategies employed by B. burgdorferi to adapt to changing environmental conditions to evaluate borrelial pathogenesis in the context of mammalian infection.…”

“…It is well documented that B. burgdorferi utilizes cyclic dinucleotides during the tick and mammalian stages of pathogenesis to modulate the necessary gene regulation for its response to environmental pressures; therefore, it is plausible that it also relies on cyclic nucleotides for regulation ( Rogers et al, 2009 ; He et al, 2011 ; Ye et al, 2014 ; Savage et al, 2015 ; Melissa J. Caimano et al, 2015 ; Zhang et al, 2018 ). It is important to understand the strategies employed by B. burgdorferi to adapt to changing environmental conditions to evaluate borrelial pathogenesis in the context of mammalian infection.…”

“…In B. burgdorferi , the second messenger cyclic di-adenosine monophosphate (c-di-AMP) is essential for in vitro growth and the production of mammalian virulence factors ( Ye et al, 2014 ; Savage et al, 2015 ). Cyclic di-guanosine monophosphate (c-di-GMP) is a key component of the Hk1–Rrp1 two-component system pathway involved in mammal to tick transmission, midgut survival, motility, and glycerol utilization by B. burgdorferi ( He et al, 2011 ; Sultan et al, 2011 ; Novak et al, 2014 ; Caimano et al, 2015 ; Bontemps-Gallo et al, 2016 ; Zhang et al, 2018 ). c-di-GMP is produced by Rrp1 and bound by PlzA to positively regulate glucose metabolism ( Rogers et al, 2009 ; Freedman et al, 2010 ; Sultan et al, 2010 ; Kostick et al, 2011 ; He et al, 2014 ; Mallory et al, 2016 ; Kostick-Dunn et al, 2018 ; Zhang et al, 2018 ).…”

TheBorrelia burgdorferiadenylyl cyclase, CyaB, is important for virulence factor production and mammalian infection

“…cAMP is used by numerous bacterial pathogens to alter both the host and pathogen at the level of post-transcriptional regulation for signal reception, signal transduction, AC activity, virulence gene regulation, resistance to oxidative stress, and persistence (Molina-Quiroz et al 2018). It is well documented that B. burgdorferi utilizes cyclic dinucleotides during the tick and mammalian stages of pathogenesis to modulate the necessary gene regulation for response to environmental pressures, therefore it is plausible it also relies on cyclic nucleotides for regulation (Savage et al 2015; Ye et al 2014; Melissa J. Caimano et al 2015; He et al 2011; Zhang et al 2018; Rogers et al 2009). It is important to understand the strategies employed by B. burgdorferi to adapt to changing environmental conditions to evaluate borrelial pathogenesis in the context of mammalian infection.…”

“…In B. burgdorferi , the second messenger cyclic di-adenosine monophosphate (c-di-AMP) is essential for in vitro growth and the production of mammalian virulence factors (Ye et al 2014; Savage et al 2015). Cyclic di-guanosine monophosphate (c-di-GMP) is a key component of the Hk1-Rrp1 two-component system pathway involved in mammal to tick transmission, midgut survival, motility, and glycerol utilization by B. burgdorferi (Zhang et al 2018; Novak, Sultan, and Motaleb 2014; He et al 2011; Sultan et al 2011; Bontemps-Gallo, Lawrence, and Gherardini 2016; Melissa J. Caimano et al 2015). c-di-GMP is produced by Rrp1 and bound by PlzA to positively regulate glucose metabolism (Rogers et al 2009; Freedman et al 2010; Kostick-Dunn et al 2018; Kostick et al 2011; Mallory et al 2016; Sultan et al 2010; He et al 2014).…”