Biology subjects

Fejer, G.

Publications and source records attributed to Fejer, G..

7 recordsLinked to original sources

bioRxiv2024

Loss of the scavenger receptor MARCO results in uncontrolled vomocytosis of fungi from macrophages.

Vomocytosis, also known as nonlytic exocytosis, is a process whereby fully phagocytosed microbes are expelled from phagocytes without discernible damage to either the phagocyte or microbe. Although this phenomenon was first described in the opportunistic fungal pathogen Cryptococcus neoformans in 2006, to date, mechanistic studies have been hampered by an inability to reliably stimulate or inhibit vomocytosis. Here we present the fortuitous discovery that macrophages lacking the scavenger receptor MAcrophage Receptor with COllagenous domain (MARCO), exhibit near-total vomocytosis of internalised cryptococci within a few hours of infection. Our findings suggest that MARCOs role in modulating vomocytosis is independent of its role as a phagocytic receptor and instead may be driven by variation in cytoskeletal arrangement between wildtype and MARCO-deficient macrophages.

immunology↗

bioRxiv2023

LPCAT2 Regulates CD14 Expression During Macrophage Inflammatory Response to E. coli O111:B4.

LPCAT2 is a lipid-modifying enzyme that co-localises in lipid rafts with TLR4 and regulates macrophage inflammatory response; however, its effect on TLR4 co-receptor-CD14 is unknown. RAW264.7 cells, a common murine macrophage experimental model, were used to study the effect of LPCAT2 on CD14 expression. The expression of LPCAT2 in RAW264.7 cells was silenced using RNA interference and treated with 100ng/ml of various lipopolysaccharide chemotypes. We found that CD14 expression induced by smooth lipopolysaccharide was significantly decreased (p < 0.05) in RAW264.7 macrophages with LPCAT2 silenced. This study suggests that LPCAT2 regulates CD14 gene and protein expression. This implies that LPCAT2 can regulate CD14-dependent cellular activities.

molecular biology↗

bioRxiv2023

Reciprocal regulation of TLR4, TLR3 and Macrophage Scavenger Receptor 1 regulates nonopsonic phagocytosis of the fungal pathogen Cryptococcus neoformans.

The opportunistic fungal pathogen Cryptococcus neoformans causes lethal infections in immunocompromised patients. Macrophages are central to the host response to cryptococci; however, it is unclear how C. neoformans is recognized and phagocytosed by macrophages. Here we investigate the role of TLR4 in the nonopsonic phagocytosis of C. neoformans. We find that loss of TLR4 function unexpectedly increases phagocytosis of nonopsonized cryptococci. The increased phagocytosis observed in Tlr4-/- cells was dampened by pre-treatment of macrophages with either a TLR3 inhibitor or oxidised-LDL, a known ligand of scavenger receptors. The scavenger receptor, macrophage scavenger receptor 1 (MSR1) (also known as SR-A1 or CD204) was upregulated in Tlr4-/- macrophages and there was a 75% decrease in phagocytosis of nonopsonized cryptococci by Msr1-/- macrophages. Furthermore, immunofluorescence imaging revealed colocalization of MSR1 and internalised cryptococci. Together, these results identify MSR1 as a key receptor for the phagocytosis of nonopsonized C. neoformans and demonstrate TLR4/MSR1 crosstalk in the phagocytosis of C. neoformans.

microbiology↗

bioRxiv2023

No trade-off between the use of space and time for working memory

Space and time can each act as scaffolds for the individuation and selection of visual objects in working memory. Here we ask whether there is a trade-off between the use of space and time for visual working memory: whether observers will rely less on space, when memoranda can additionally be individuated through time. We tracked the use of space through directional biases in microsaccades after attention was directed to memory contents that had been encoded simultaneously or sequentially to the left and right of fixation. We found that spatial gaze biases were preserved when participants could (Experiment 1) and even when they had to (Experiment 2) additionally rely on time for object individuation. Thus, space remains a profound organizing medium for working memory even when other organizing sources are available and utilised, with no evidence for a trade-off between the use of space and time. SIGNIFICANCE STATEMENTSpace and time provide two foundational dimensions that govern not only our sensations and actions, but also the organisation of internal representations in working memory. Space and time have each been shown to provide an automatic organising principle - or scaffold - for memory retention. We uniquely address whether there is a trade-off between the use of space and time for working memory. We show that the profound and automatic reliance on memorised space is preserved not only when time can, but even when time has to be used for individuation and selection of memory contents. This shows there is no trade-off between spatial and temporal codes available for memory organisation, advancing our understanding of the spatial-temporal architecture of mind.

neuroscience↗

bioRxiv2021

Lysophosphatidylcholine acyltransferase 2 (LPCAT2) Regulates The Expression of Macrophage Phenotype Markers in RAW264.7 Cells.

1Macrophages are key antigen presenting cells that also secrete cytokines during inflammation. They can be polarised to M1 or M2 phenotypes. Molecules such as CD206 and inducible Nitric Oxide Synthase are considered macrophage phenotype markers because they are highly expressed in either M1 or M2 macrophages. LPCAT2 is a phospholipid modifying enzyme that influences inflammatory responses in macrophages. However, how LPCAT2 influences inflammation is not fully understood. In this study, we have used genetic technology to study the influence of LPCAT2 on macrophage phenotype markers. Our results show for the first time that overexpression of LPCAT2 promotes the expression of M1 macrophage phenotype markers, and attenuates the expression of M2 macrophage markers.

immunology↗

bioRxiv2021

Possible Regulation of Toll-Like Receptor 4 By Lysine Acetylation Through LPCAT2 Activity in RAW264.7 Cells.

1Inflammation is central to several diseases. TLR4 mediates inflammatory signals, however, there are gaps in the understanding of its mechanisms. Recently, TLR4 was found to co-localise with LPCAT2, a lysophospholipid acetyltransferase. This interaction influenced TLR4 subcellular localisation through an unknown mechanism. In this study, we have combined computational analysis, RNA interference technology, and biochemical analysis to investigate the possibility of TLR4 lysine acetylation and the influence of LPCAT2 on the detected lysine acetylation. The results suggest for the first time that TLR4 can undergo lysine acetylation and LPCAT2 can influence TLR4 lysine acetylation. This lays a foundation for further research on the role of lysine acetylation on TLR4 and characterisation of LPCAT2 as a protein acetyltransferase.

biochemistry↗

bioRxiv2019

Oropouche virus cases identified in Ecuador using an optimised rRT-PCR informed by metagenomic sequencing

Oropouche virus (OROV) is responsible for outbreaks of Oropouche fever in parts of South America. We recently identified and isolated OROV from a febrile Ecuadorian patient, however, a previously published rRT-PCR assay did not detect OROV in the patient sample. A primer mismatch to the Ecuadorian OROV lineage was identified from metagenomic sequencing data. We report the optimisation of an rRT-PCR assay for the Ecuadorian OROV lineage, which subsequently identified a further five cases in a cohort of 196 febrile patients. We isolated OROV via cell culture and developed an algorithmically-designed primer set for whole-genome amplification of the virus. Metagenomic sequencing of the patient samples provided OROV genome coverage ranging from 68 - 99%. The additional cases formed a single phylogenetic cluster together with the initial case. OROV should be considered as a differential diagnosis for Ecuadorian patients with febrile illness to avoid mis-diagnosis with other circulating pathogens.

genomics↗