Biology subjects

sa-Pessoa Graca Santos, J.

Publications and source records attributed to sa-Pessoa Graca Santos, J..

4 recordsLinked to original sources

bioRxiv2025

Klebsiella pneumoniae disrupts vasodilation by targeting eNOS post translational modifications via the type VI secretion system and the capsule polysaccharide

Vasodilation is a crucial protective response to inflammation and infection. Endothelial cells control vasodilation through the bioavailability of eNOS-produced nitric oxide (NO), and the generation of endothelium-dependent hyperpolarization (EDH). Here, we demonstrate that Klebsiella pneumoniae, one of the most prevalent blood stream infection pathogens, inhibits agonist-induced vasodilation by blunting the NO-dependent pathway and attenuating the EDH pathway. The type VI secretion system (T6SS) effector VgrG4 licences the kinase PKC{beta} in an NLRX1-controlled mitochondria reactive oxygen species (mtROS)-dependent manner to phosphorylate the eNOS inhibitory site Thr495, effectively dampening eNOS activity. The capsule polysaccharide, on the other hand, limits the phosphorylation of the eNOS activation site Ser1177 by inducing the phosphatase PP2Ac upon activation of an EGF receptor-dependent pathway. VgrG4-induced mtROS attenuates the EDH pathway. Overall, this work reveals a new anti-host activity of the T6SS and illustrates how pathogens can control vascular biology by targeting eNOS post translational modifications.

microbiology↗

bioRxiv2021

In vivo single cell transcriptomics reveals Klebsiella pneumoniae rewiring of lung macrophages to promote infection

The strategies deployed by antibiotic resistant bacteria to counteract host defences are poorly understood. Here, we elucidate a novel host-pathogen interaction that results in the control of lung macrophage polarisation by the human pathogen Klebsiella pneumoniae. We identify interstitial macrophages (IMs) as the main population of lung macrophages associated with Klebsiella. Single cell transcriptomics and trajectory analysis of cells uncover that type I IFN and IL10 signalling, and macrophage polarization are characteristic of infected IMs, whereas Toll-like receptor (TLR) and Nod-like receptor signalling are features of infected alveolar macrophages. Klebsiella-induced macrophage polarization is a singular M2-type we termed M(Kp). To rewire macrophages towards M(Kp), K. pneumoniae hijacks a hitherto unknown TLR-type I IFN-IL10-STAT6 innate axis. Absence of STAT6 limits the intracellular survival of Klebsiella whereas the inhibition of STAT6 facilitates the clearance of the pathogen in vivo. Glycolysis characterises M(Kp) metabolism, and inhibition of glycolysis results in clearance of intracellular Klebsiella. We demonstrate the capsule polysaccharide is the Klebsiella factor governing M(Kp). Klebsiella also skews human macrophage polarization towards M(Kp) in a type I IFN-IL10-STAT6-dependent manner. Altogether, our work demonstrates that Klebsiella induction of M(Kp) represents a hitherto unknown strategy to overcome host restriction during pneumonia.

microbiology↗

bioRxiv2021

Klebsiella pneumoniae hijacks the Toll-IL-1R protein SARM1 in a type I IFN-dependent manner to antagonize host immunity.

Many bacterial pathogens antagonize host defence responses by translocating effector proteins into cells. It remains an open question how those pathogens not encoding effectors counteract anti-bacterial immunity. Here, we show that Klebsiella pneumoniae hijacks the evolutionary conserved innate immune protein SARM1 to control cell intrinsic immunity. Klebsiella exploits SARM1 to regulate negatively MyD88 and TRIF-governed inflammation, and the activation of the MAP kinases ERK and JNK. SARM1 is required for Klebsiella induction of IL10 by fine-tuning the p38-type I IFN axis. SARM1 inhibits the activation of Klebsiella-induced absent in melanoma 2 inflammasome to limit IL1{beta} production, suppressing further inflammation. Klebsiella exploits type I IFNs to induce SARM1 in a capsule and LPS O-polysaccharide-dependent manner via TLR4-TRAM-TRIF-IRF3-IFNAR1 pathway. Absence of SARM1 reduces the intracellular survival of K. pneumonaie in macrophages whereas sarm1 deficient mice control the infection. Altogether, our results illustrate a hitherto unknown anti-immunology strategy deployed by a human pathogen.

microbiology↗

bioRxiv2019

Klebsiella pneumoniae type VI secretion system-mediated microbial competition is PhoPQ controlled and reactive oxygen species dependent

Klebsiella pneumoniae is recognized as an urgent threat to human health due to the increasing isolation of multidrug resistant strains. Hypervirulent strains are a major concern due to their ability to cause life-threating infections in healthy hosts. The type VI secretion system (T6SS) is widely implicated in microbial antagonism, and it mediates interactions with host eukaryotic cells in some cases. In silico search for genes orthologous to T6SS component genes and T6SS effector genes across 700 K. pneumoniae genomes shows extensive diversity in T6SS genes across the K. pneumoniae species. Temperature, oxygen tension, pH, osmolarity, iron levels, and NaCl regulate the expression of the T6SS encoded by a hypervirulent K. pneumoniae strain. Polymyxins and human defensin 3 also increase the activity of the T6SS. A screen for regulators governing T6SS uncover the correlation between the transcription of the T6SS and the ability to kill E. coli prey. Whereas H-NS represses the T6SS, PhoPQ, PmrAB, Hfq, Fur, RpoS and RpoN positively regulate the T6SS. K. pneumoniae T6SS mediates intra and inter species bacterial competition. This antagonism is only evident when the prey possess an active T6SS. The PhoPQ two component system governs the activation of K. pneumoniae T6SS in bacterial competitions. Mechanistically, PhoQ periplasmic domain, and the acid patch within, is essential to activate K. pneumoniae T6SS. Klebsiella T6SS also mediates anti-fungal competition. We have delineated the contribution of each of the individual VgrGs in microbial competition, and identified VgrG4 as a T6SS effector. Structurally, domain DUF2345 of VgrG4 is sufficient to intoxicate bacteria and yeast. ROS generation mediates the antibacterial effects of VgrG4, and the antitoxin Sel1E protects against the toxic activity of VgrG4. Our findings provide a better understanding of the regulation of the T6SS in bacterial competitions, and place ROS as an early event in microbial competition.\n\nAUTHOR SUMMARYKlebsiella pneumoniae has been singled out as an \"urgent threat to human health\" due to extremely drug resistant strains. Numerous studies investigate the molecular mechanisms underlying antibiotic resistance in K. pneumoniae, while others dissect the virulence strategies of this pathogen. However, there is still limited knowledge on the fitness of Klebsiella in the environment, and particularly the competition of Klebsiella with other species. Here, we demonstrated that Klebsiella exploits the type VI secretion system (T6SS) nanoweapon to kill bacterial competitors and fungi. K. pneumoniae perceives T6SS attacks from bacterial competitors, resulting in retaliation against the aggressive cell. The perception of the attack involved the sensor PhoPQ and led to the up-regulation of the T6SS. We identified one of the toxins deployed by the T6SS to antagonize other microbes, and revealed how Klebsiella protects itself from this toxin. Our findings provide a better understanding of the T6SS role in microbial competition and uncover new aspects on how bacteria regulate T6SS-mediated microbial antagonism.

microbiology↗