Identification of Ligands of the PLD1 Protein from Klebsiella pneumoniae in Protein Extracts of Human THP-1 Macrophages

ABSTRACT: Klebsiella pneumoniae is a widespread enterobacterium responsible for opportunistic infections in humans. It is commonly found in healthcare settings, carrying genes that provide resistance to several antimicrobials, including carbapenems and third-generation cephalosporins. Community-acquired infections have also become a major concern due to the emergence of hypervirulent strains. The World Health Organization has placed this bacterium at the top of its priority list for developing new treatment strategies. Research into molecular mechanisms of bacterial virulence may contribute to this goal, providing a knowledge basis for future innovation. It was previously described that a putative phospholipase D (PLD1) is involved in K. pneumoniae virulence, as a mutant strain is avirulent in a mouse pneumonia model. However, the PLD1 function was not yet described. In the current study, we did not detect the interaction between PLD1 and lipids in a fat-blot assay. To shed light on the role of PLD1, we compared the gene expression profile of wild-type x pld1 mutant bacteria by RNA-Seq. The pld1 gene mutation modulated the expression of 330 genes. Noteworthy, capsular polysaccharide genes and their transcriptional regulators presented increased expression in the wild-type strain. In another hand, mutant strains expressed higher levels of fimbriae, conjugation systems, and proteins involved in cellular stress protection. Accordingly, phenotypic characterization detected a loose capsule in the pld1 mutant strain by electron microscopy and found that the mutant strain presented enhanced bacterial adhesion in Caco-2 intestinal epithelial cells. This set of data indicates that, to some extent, the pld1 avirulence in the mouse model might be a result of indirect effects over the expression of other virulence factors. In addition, we performed a pulldown experiment using the recombinant PLD1 protein as bait and identified 48 proteins as putative ligands in a human macrophage extract. Those proteins are mainly ribosomal and RNA-related proteins, as well as small GTPases and cytoskeleton-related proteins. Some of them may belong to focal adhesions and adherens junctions. Therefore, we hypothesize that PLD1 may have an additional role in bacterial pathogenesis, by modulating host cell complexes, favoring the infection. In conclusion, this study provides novel clues about the role of PLD1 in virulence, paving the way for further investigations.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Monocyte, Cell Culture

DISEASE(S): Acute Leukemia

SUBMITTER: Mayara de Mattos Lacerda de Carvalho  

LAB HEAD: Leticia Miranda Santos Lery

PROVIDER: PXD059279 | Pride | 2025-06-16

REPOSITORIES: Pride