Biology subjects

Kanaji, S.

Publications and source records attributed to Kanaji, S..

4 recordsLinked to original sources

bioRxiv2026

Cardioselective β-blocker Therapy Resolves Staphylococcus aureus Toxin-Induced Innate Immunoparalysis

During Staphylococcus aureus sepsis, the pore-forming -toxin (Hla) triggers lytic platelet death and provokes the release of catecholamines that modulate leukocyte effector function. The resulting surge in catecholaminergic action paralyzes host antimicrobial capacity by upregulating interleukin-10 (IL-10), profoundly suppressing the protective interferon (IFN) response to orchestrate innate immunoparalysis. Here, we deconvolute a multi-cellular regulatory pathway in the blood and highlight a pivotal immunological checkpoint, where pharmacological intervention with cardioselective {beta}-blockers uncouples the immunosuppressive cascade, restores host antimicrobial function, and significantly improves survival outcomes.

microbiology↗

bioRxiv2025

Human PAR1 expressed on mouse platelets contributes to hemostasis and arterial occlusion

Thrombin (FIIa) signaling through protease-activated receptors (PARs) is a relevant platelet activation mechanism. Human (h) PAR1 antagonists are approved for antithrombotic therapy, but bleeding is a concerning complication. In addition to PARs, platelet glycoprotein (GP) Ib also binds FIIa enhancing human platelet response to lower agonist concentrations ex vivo. Signaling through GPCRs is well understood, but how GPIb association with distinct PARs modulates FIIa-dependent platelet activation in vivo remains unclear. One obstacle in addressing this question is the distinct human platelet PAR1/PAR4 expression as opposed to mouse (m) PAR3/PAR4. Previous attempts to express functioning hPAR1 in mouse platelets using platelet-specific promoters or targeting into the mPAR3 locus have not been successful. Here we report our studies using a hPAR1 transgene with a floxed STOP sequence and strong synthetic (CAG) promoter targeted into the mouse Rosa26 locus. Generated Rosa26-hPAR1Tgfl mice were then sequentially crossbred with PF4-Cre and PAR3-/- mice, yielding mP3-/-hP1Tg mice whose platelets expressed hPAR1 with endogenous mPAR4. These mice, unlike PAR3-/-, had no excessive bleeding after tail clipping, but bled profusely after administration of the hPAR1 antagonist, vorapaxar. Accordingly, mP3-/-hP1Tg mice had more frequent and stable post injury occlusion of the carotid artery than PAR3-/- mice, but this difference was abolished by vorapaxar treatment. We anticipate that studies in this mouse strain will help unravel the regulation of PAR-mediated thrombin-induced platelet activation in vivo with findings more directly relevant to human pathophysiology. Key Points (<140 characters each)O_LIHuman (h) PAR1 expressed in the platelets of PAR3-/- mice shortens the bleeding time and promotes more frequent and stable post injury carotid artery occlusion. C_LIO_LIThe specific hPAR1 antagonist drug, vorapaxar reverses the phenotypic changes associated with hPAR1 expression in PAR3-/- mice expressing mouse PAR4. C_LIO_LIExperimental data from PAR3-/- mice expressing hPAR1 should be directly relevant to the development of specific thrombin-induced platelet activation inhibitors. C_LI

physiology↗

bioRxiv2025

WHEP Domain of Glycyl-tRNA Synthetase Regulates Neuropilin 1 Binding and Vascular Permeability

AbstractAminoacyl-tRNA synthetases (aaRSs) charge tRNAs with their cognate amino acids, ensuring accurate translation of the genetic code from mRNA to protein. During eukaryotic evolution, aaRSs acquired additional domains with unclear functions, including the WHEP domain, a two-helix bundle found in several eukaryotic aaRSs such as glycyl-tRNA synthetase (GlyRS, encoded by GARS1). We generated Gars1{Delta}WHEP mutant mice lacking exon 2, which disrupts most of the WHEP domain. Homozygous Gars1{Delta}WHEP/{Delta}WHEP mice exhibited late embryonic or neonatal lethality, with delayed lung development, characterized by reduced airway dilation (inflatability), and increased vascular leakage. Disruption of the WHEP domain did not impair tRNA aminoacylation but inhibited the free release of GlyRS from cells. Instead, GlyRS{Delta}WHEP was found in the membrane fractions and showed a stronger interaction with the extracellular region of neuropilin 1 (Nrp1) receptor compared to full-length GlyRS. This aberrant interaction enhanced Nrp1s endocytic activity and significantly reduced the localization of the Nrp1 interactor VE-cadherin at the adherens junctions of endothelial cells. A heterozygous knockout of Nrp1 in the Gars1 {Delta}WHEP/{Delta}WHEP mice partially rescued body weight and vascular permeability defects. This study establishes a physiological role for the GlyRS WHEP domain in lung development and its regulation of GlyRS-Nrp1 interaction and vascular permeability.

molecular biology↗

bioRxiv2020

Repurposed Drugs Block Toxin-Driven Platelet Clearance by the Hepatic Ashwell-Morell Receptor to Clear Staphylococcus aureus Bacteremia

ABSTRACTStaphylococcus aureus (SA) bloodstream infections cause high morbidity and mortality (20-30%) despite modern supportive care. In a human bacteremia cohort, development of thrombocytopenia was correlated to increased mortality and increased α-toxin expression by the pathogen. Platelet-derived antibacterial peptides are important in bloodstream defense against SA, but α-toxin decreased platelet viability, induced platelet sialidase to cause desialylation of platelet glycoproteins, and accelerated platelet clearance by the hepatic Ashwell-Morell receptor (AMR). Ticagrelor (Brilinta®), a commonly prescribed P2Y12 receptor inhibitor used post-myocardial infarction, blocked α-toxin-mediated platelet injury and resulting thrombocytopenia, thus providing protection from lethal SA infection in a murine intravenous challenge model. Genetic deletion or pharmacological inhibition of AMR stabilized platelet counts and enhanced resistance to SA infection, and the anti-influenza sialidase inhibitor oseltamivir (Tamiflu®) provided similar therapeutic benefit. Thus a “toxin-platelet-AMR” regulatory pathway plays a critical role in the pathogenesis of SA bloodstream infection, and its elucidation provides proof-of-concept for repurposing two FDA-approved drugs as adjunctive therapies to improve patient outcomes.Competing Interest StatementThe authors have declared no competing interest.View Full Text

microbiology↗