Biology subjects

Prince, L.

Publications and source records attributed to Prince, L..

5 recordsLinked to original sources

bioRxiv2026

Macrophages use sub-micron actin ridges in phagocytosis of encapsulated fungal pathogens

Ingestion and killing of pathogens by phagocytic cells is a key aspect of animal immunity. Cryptococcus neoformans is a major pathogen of AIDS patients that has a polysaccharide capsule that is critical for virulence. Phagocytic function is necessary for normal immunity to cryptococcal infection, and we sought to determine how Cryptococcus capsule prevents phagocytosis. In doing so, we discovered a new sub-micron actin structure, the ridge, that is present on macrophages, neutrophils and amoebae. Macrophages preferentially bind cryptococci via ridges and suppression of ridges is sufficient to prevent phagocytosis. Ridges are present on macrophages in vivo and are lost in interleukin 10 stimulated macrophages. The discovery and functional description of macrophage surface ridges fills a critical gap in our understanding of how phagocytes ingest encapsulated fungal pathogens, a crucial step in treating infection.

cell biology↗

bioRxiv2024

Pulses of Class I PI3kinase activity identify the release and recapture of prey from neutrophil phagosomes

Class I PI3kinases coordinate the delivery of microbicidal effectors to the phagosome by forming the phosphoinositide lipid second messenger, phosphatidylinositol (3, 4, 5)-trisphosphate (PIP3). However, the dynamics of PIP3 in neutrophils during a bacterial infection are unknown. We have therefore developed an in vivo, live zebrafish infection model that enables visualisation of dynamic changes in Class 1 PI3kinases (PI3K) signalling on neutrophil phagosomes in real-time. We have identified that on approximately 12% of neutrophil phagosomes PHAkt-eGFP, a reporter for Class 1 PI3K signalling, re-recruits in pulsatile bursts. This phenomenon occurred on phagosomes containing structurally and morphologically distinct prey, including Staphylococcus aureus and Mycobacterium abscessus, and was dependent on the activity of the Class 1 PI3K isoform, PI3kinase {gamma}. Detailed imaging suggested that pulsing phagosomes represent neutrophils transiently reopening and reclosing phagosomes. This finding challenges the concept that phagosomes remain closed after prey engulfment and we propose that neutrophils occasionally use this alternative pathway of phagosome maturation to release phagosome contents and/or to restart phagosome maturation if digestion has stalled.

cell biology↗

bioRxiv2023

Determining the importance of the stringent response for methicillin-resistant Staphylococcus aureus virulence using a zebrafish model of infection

Staphylococcus aureus is a bacterial pathogen that poses a major threat to human health. The ability of this bacterium to adapt to stresses encountered in the host is essential for disease. The stringent response is a signalling pathway utilised by all bacteria to alarm cells when stressed, and has been linked to the virulence of a number of species. This signalling pathway is controlled by the nucleotide alarmones guanosine tetra-(ppGpp) and pentaphosphate (pppGpp: collectively termed (p)ppGpp), produced in S. aureus by three synthetase enzymes: Rel, RelP and RelQ. Here, we used a triple (p)ppGpp synthetase mutant ((p)ppGpp0) to examine the importance of this signalling network for the survival and virulence of S. aureus in vivo. Using an established zebrafish larval infection model, we observed that infection with (p)ppGpp0 resulted in attenuated virulence, which was not due to a reduced ability of the mutant to replicate in vivo. Of the three (p)ppGpp synthetases, Rel was established as key during infection, but roles for RelP and RelQ were also observed. Zebrafish myeloid cell depletion restored the virulence of (p)ppGpp0 during systemic infection, indicating that (p)ppGpp is important for survival within host phagocytes. Primary macrophages infection studies, followed by in vitro tolerance assays to key innate immune effectors, demonstrated that (p)ppGpp0 was more susceptible to stressors found within the intracellular macrophage environment, with roles for all three synthetases implicated. Lastly, the absence of CodY, a transcription factor linked to the stringent response, significantly increased the tolerance of S. aureus to phagolysosomal-like stressors in vitro, but had no impact in vivo. Taken together, these results define the importance of the stringent response for S. aureus infection, revealing that (p)ppGpp produced by all three synthetases is required for bacterial survival within the host environment by mediating adaptation to the phagolysosome.

microbiology↗

bioRxiv2021

Multi-modal imaging reveals dynamic interactions of Staphylococcus aureus within human neutrophils

Staphylococcus aureus is an important human pathogen that causes a wide range of infections. Neutrophils are an essential component of our innate immune system and understanding S. aureus-neutrophil interactions on a sub-cellular level is crucial to developing new therapeutic strategies to promote immunity during S. aureus infections. To this end we have developed a multi-modal imaging platform capable of following host-pathogen processes in biological systems, this is achieved by switching imaging modalities between a low photo-toxicity and low resolution imaging modality through an increasing illumination intensity to achieve live super-resolution imaging. This novel imaging platform was applied to the study of human neutrophils infected by S. aureus. We show that we can image different infection stages of S. aureus in live neutrophils with super resolution microscopy. We see evidence of binary fission occurring in intracellular S. aureus within a neutrophil.

biophysics↗

bioRxiv2019

Inhibition of ErbB kinase signalling promotes resolution of neutrophilic inflammation

Neutrophilic inflammation with prolonged neutrophil survival is common to many inflammatory conditions, including chronic obstructive pulmonary disease (COPD). There are few specific therapies that reverse neutrophilic inflammation, but uncovering mechanisms regulating neutrophil survival is likely to identify novel therapeutic targets. Screening of 367 kinase inhibitors in human neutrophils and a zebrafish tail fin injury model identified ErbBs as common targets of compounds that accelerated inflammation resolution. The ErbB inhibitors gefitinib, CP-724714, erbstatin and tyrphostin AG825 significantly accelerated apoptosis of human neutrophils, including neutrophils from people with COPD. Neutrophil apoptosis was also increased in Tyrphostin AG825 treated-zebrafish in vivo. Tyrphostin AG825 decreased peritoneal inflammation in zymosan-treated mice, and increased lung neutrophil apoptosis and macrophage efferocytosis in a murine acute lung injury model. Tyrphostin AG825 and knockdown of egfra and erbb2 by CRISPR/Cas9 reduced inflammation in zebrafish. Our work shows that inhibitors of ErbB kinases have therapeutic potential in neutrophilic inflammatory disease.

immunology↗