HtrA, a Temperature- and Stationary Phase-Activated Protease Involved in Maturation of a Key Microbial Virulence Determinant, Facilitates Borrelia burgdorferi Infection in Mammalian Hosts.
High-temperature requirement protease A (HtrA) represents a family of serine proteases that play important roles in microbial biology. Unlike the genomes of most organisms, that of Borrelia burgdorferi notably encodes a single HtrA gene product, termed BbHtrA. Previous studies identified a few substrates of BbHtrA; however, their physiological relevance could not be ascertained, as targeted deletion of the gene has not been successful. Here we show that BbhtrA transcripts are induced during spirochete growth either in the stationary phase or at elevated temperature. Successful generation of a BbhtrA deletion mutant and restoration by genetic complementation suggest a nonessential role for this protease in microbial viability; however, its remarkable growth, morphological, and structural defects during cultivation at 37°C confirm a high-temperature requirement for protease activation and function. The BbhtrA-deficient spirochetes were unable to establish infection of mice, as evidenced by assessment of culture, PCR, and serology. We show that transcript abundance as well as proteolytic processing of a borrelial protein required for cell fission and infectivity, BB0323, is impaired in BbhtrA mutants grown at 37°C, which likely contributed to their inability to survive in a mammalian host. Together, these results demonstrate the physiological relevance of a unique temperature-regulated borrelial protease, BbHtrA, which further enlightens our knowledge of intriguing aspects of spirochete biology and infectivity.
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA.|College of Laboratory Medicine, Wenzhou Medical University, Wenzhou, China.
Meiping
M
Ye
Department of Veterinary Medicine, University of Maryland, College Park, and Virginia-Maryland Regional College of Veterinary Medicine, College Park, Maryland, USA.
Kavita
K
Sharma
Department of Veterinary Medicine, University of Maryland, College Park, and Virginia-Maryland Regional College of Veterinary Medicine, College Park, Maryland, USA.
Meghna
M
Thakur
Department of Veterinary Medicine, University of Maryland, College Park, and Virginia-Maryland Regional College of Veterinary Medicine, College Park, Maryland, USA.
Alexis A
AA
Smith
Department of Microbiology, Faculty of Veterinary Medicine, Ondokuz Mayis University, Samsun, Turkey.
Ozlem
O
Buyuktanir
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Xuwu
X
Xiang
Department of Veterinary Medicine, University of Maryland, College Park, and Virginia-Maryland Regional College of Veterinary Medicine, College Park, Maryland, USA.
Xiuli
X
Yang
Department of Veterinary Medicine, University of Maryland, College Park, and Virginia-Maryland Regional College of Veterinary Medicine, College Park, Maryland, USA.
Kamoltip
K
Promnares
College of Laboratory Medicine, Wenzhou Medical University, Wenzhou, China.
Yongliang
Y
Lou
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
X Frank
XF
Yang
Department of Veterinary Medicine, University of Maryland, College Park, and Virginia-Maryland Regional College of Veterinary Medicine, College Park, Maryland, USA upal@umd.edu.
Utpal
U
Pal
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D025065:Borrelia burgdorferi / Q000502:physiology*; D004195:Disease Models, Animal; D008193:Lyme Disease / Q000382:microbiology*; D051379:Mice; D011485:Protein Binding; D059748:Proteolysis; D017384:Sequence Deletion; D012697:Serine Endopeptidases / Q000378:metabolism*; D013696:Temperature; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism*
D001426:Bacterial Proteins; D037521:Virulence Factors; D012697:Serine Endopeptidases