Biology subjects

Sze, C. W.

Publications and source records attributed to Sze, C. W..

3 recordsLinked to original sources

bioRxiv2025

Lactate dehydrogenase is the Achilles' heel of Lyme disease bacterium Borreliella burgdorferi

As a zoonotic pathogen, the Lyme disease bacterium Borreliella burgdorferi has evolved unique metabolic pathways, some of which are specific and essential for its survival and thus present as ideal targets for developing new therapeutics. B. burgdorferi dispenses with the use of thiamin as a cofactor and relies on lactate dehydrogenase (BbLDH) to convert pyruvate to lactate for balancing NADH/NAD+ ratios. This report first demonstrates that BbLDH is a canonical LDH with some unique biochemical and structural features. A loss-of-function study then reveals that BbLDH is essential for B. burgdorferi survival and infectivity, highlighting its therapeutic potential. Drug screening identifies four previously unknown LDH inhibitors with minimal cytotoxicity, two of which inhibit B. burgdorferi growth. This study provides mechanistic insights into the function of BbLDH in the pathophysiology of B. burgdorferi and lays the groundwork for developing genus-specific metabolic inhibitors against B. burgdorferi and potentially other tick-borne pathogens as well.

microbiology↗

bioRxiv2024

Gain-of-function study reveals the pleiotropic roles of serine protease HtrA in Borrelia burgdorferi

High-temperature requirement protease A (HtrA) is a family of serine proteases degrading misfolded and damaged proteins that are toxic to bacteria. The Lyme disease agent Borrelia burgdorferi encodes a single HtrA (BbHtrA). Previous studies have shown that BbHtrA is a key virulence determinant of B. burgdorferi as a deletion mutant of htrA ({Delta}htrA) fails to establish infection in mice. However, previous complementation could only restore protein expression but not infectivity in mice. In this report, we first identify the native promoter of BbHtrA which allows us to construct a fully complemented{Delta} htrA strain. Follow up promoter activity analysis reveals that BbHtrA is likely dually regulated by the house keeping sigma factor RpoD and the alternative sigma factor RpoS. The{Delta} htrA mutant exhibits growth defect upon entering the mid-log to stationary phase especially at high temperatures. Microscopic analysis further demonstrates that the absence of htrA induces extensive cell death. Additionally, the{Delta} htrA mutant has defects in cell locomotion as the expression of several key chemotaxis proteins are significantly downregulated. Cryo-electron tomography imaging of htrA mutant further reveals that deletion of htrA disrupts flagellar homeostasis. The failure of{Delta} htrA to establish an infection in mice is likely due to repressed expression of BosR and RpoS at the transcriptional level which ultimately causes dysregulation of the RpoS-induced virulence factors. Collectively, we conclude that the expression of htrA is finely tuned which is critical for its pleiotropic roles in the regulation of motility, stress response, and virulence gene expression in B. burgdorferi. IMPORTANCELyme borreliosis is the most commonly reported vector-borne illnesses in the United States, which is caused by Borrelia burgdorferi. As the enzootic pathogen alternates between the tick vector and mammalian hosts, adaptation to drastically different growth milieu is imperative to its survival. Hence, robust alteration of gene expression and proper quality control on protein synthesis and turnover are pivotal for its fitness. The family of HtrA serine proteases is mainly responsible for the maintenance of protein homeostasis particularly under stressful conditions. The significance of this report is to decode how BbHtrA contributes to the fitness of B. burgdorferi. BbHtrA is essential for mammalian host infection but little is known about its regulatory mechanism as well as its contribution to the virulence of B. burgdorferi. By deciphering the regulatory elements involved in the expression of BbHtrA, we are one step closer to comprehending its significance in the pathophysiology of B. burgdorferi.

microbiology↗

bioRxiv2024

MCP5, a methyl-accepting chemotaxis protein regulated by both the Hk1-Rrp1 and Rrp2-RpoN-RpoS pathways, is required for the immune evasion of Borrelia burgdorferi

Borrelia (or Borreliella) burgdorferi, the causative agent of Lyme disease, is a motile and invasive zoonotic pathogen, adept at navigating between its arthropod vector and mammalian host. While motility and chemotaxis are well established as essential for its enzootic cycle, the function of methyl-accepting chemotaxis proteins (MCPs) in the infectious cycle of B. burgdorferi remains unclear. In this study, we demonstrate that MCP5, one of the most abundant MCPs in B. burgdorferi, is differentially expressed in response to environmental signals as well as at different stages of the pathogens enzootic cycle. Specifically, the expression of mcp5 is regulated by the Hk1-Rrp1 and Rrp2-RpoN-RpoS pathways, which are critical for the spirochetes colonization of the tick vector and mammalian host, respectively. Infection experiments with an mcp5 mutant revealed that spirochetes lacking MCP5 could not establish infections in either C3H/HeN mice or Severe Combined Immunodeficiency (SCID) mice, which are defective in adaptive immunity, indicating the essential role of MCP5 in mammalian infection. However, the mcp5 mutant could establish infection and disseminate in NOD SCID Gamma (NSG) mice, which are deficient in both adaptive and most innate immune responses, suggesting a crucial role of MCP5 in evading host innate immunity. In the tick vector, the mcp5 mutants survived feeding but failed to transmit to mice, highlighting the importance of MCP5 in transmission. Our findings reveal that MCP5, regulated by the Rrp1 and Rrp2 pathways, is critical for the establishment of infection in mammalian hosts by evading host innate immunity and is important for the transmission of spirochetes from ticks to mammalian hosts, underscoring its potential as a target for intervention strategies. SUMMARYLyme disease is the most commonly reported arthropod-borne illness in the US, Europe, and Asia. The causative agent of Lyme disease, Borrelia burgdorferi, is maintained in an enzootic cycle involving arthropod vectors (Ixodes ticks) and rodent mammalian hosts. Understanding how B. burgdorferi moves within this natural cycle is crucial for developing new strategies to combat Lyme disease. The complex nature of the enzootic cycle necessitates sensory-guided movement in response to environmental stimuli. B. burgdorferi possesses a unique and intricate chemotaxis signaling system, with methyl-accepting chemotaxis proteins (MCPs) at its core. These proteins are responsible for sensing environmental signals and guiding bacterial movement toward or away from stimuli. This study found that one of the MCPs, MCP5, is highly expressed and differentially regulated during the enzootic cycle by the Hk1-Rrp1 and Rrp2-RpoN-RpoS pathways. MCP5 is crucial for mammalian infection, aiding in immune evasion and transmission from ticks to mammals, providing a foundation for further research into B. burgdorferis navigation within its hosts.

microbiology↗