Biology subjects

Morrison, E.

Publications and source records attributed to Morrison, E..

5 recordsLinked to original sources

bioRxiv2026

Increased CD33 levels tune activation and function of iinduced human microglial cells through inhibition of the TREM2 pathway

The microglial CD33 gene is overexpressed in the brains of individuals with Alzheimers disease, and multiple CD33 genetic variants are directly linked to disease risk. Here, we investigate CD33 function in induced human microglial cells by increasing or decreasing CD33 levels with AAV6-mediated gene transfer and with CD33-targeting siRNA, respectively. Phagocytosis of oligomeric amyloid beta into live microglia was doubled by reducing CD33 levels, with concomitant increases in secreted TREM2 and in TREM2 activation as assayed by phosphorylation of downstream SYK. Increasing CD33 had opposing effects on microglial activity, decreasing amyloid beta uptake by approximately half, reducing LPS-induced increases in IL-10, and decreasing the efficacy of a TREM2-activating antibody. Experiments combining siRNA and AAV6 demonstrated a linear relationship between CD33 protein and amyloid beta uptake. Results show that CD33 largely governs multiple microglial functions associated with Alzheimers disease and affects both pharmacological and physiological activation of TREM2.

neuroscience↗

bioRxiv2019

Dynamic Palmitoylation Events Following T-Cell Receptor Signaling

Palmitoylation is the reversible addition of palmitate to cysteine via a thioester linkage. Following stimulation of the T-cell receptor we find a number of proteins are newly palmitoylated, including those involved in vesicle-mediated transport and Ras signal transduction. Among these stimulation-dependent palmitoylation targets are the v-SNARE VAMP7, important for docking of vesicular LAT during TCR signaling, and the largely undescribed palmitoyl acyltransferase DHHC18 that is expressed in two isoforms in T cells. Using our newly developed On-Plate Palmitoylation Assay (OPPA), we show DHHC18 is capable of palmitoylating VAMP7 at Cys183. Cellular imaging shows that the palmitoylation-deficient protein fails to be retained at the Golgi.

biochemistry↗

bioRxiv2019

CD4+ Th immunogenicity of the Ascaris spp. secreted products

Ascaris spp. is a major health problem of humans and animals alike, and understanding the immunogenicity of its antigens is required for developing urgently needed vaccines. The parasite-secreted products represent the most relevant, yet highly complex (>250 proteins) antigens of Ascaris spp. as defining the pathogen-host interplay. We applied an in vitro antigen processing system coupled to quantitative proteomics to identify potential CD4+ Th cell epitopes in Ascaris suum-secreted products. This approach restricts the theoretical list of epitopes, based on affinity prediction, by a factor of [~]1200. More importantly, selection of 2 candidate peptides based on experimental evidence demonstrated the presence of epitope-reactive T cells in Ascaris-specific T cell lines generated from healthy human individuals. Thus, this stringent work pipeline identifies a human haplotype-specific T cell epitope of a major human pathogen. The methodology described represents an easily adaptable platform for characterization of highly complex pathogenic antigens and their MHCII-restriction.

immunology↗

bioRxiv2019

Physiological adaptations of leaf litter microbial communities to long-term drought

Drought represents a significant stress to soil microorganisms and is known to reduce microbial activity and organic matter decomposition in Mediterranean ecosystems. However, we still lack a detailed understanding of the drought stress adaptations of microbial decomposers. We hypothesised that drought causes greater microbial allocation to stress tolerance relative to growth pathways. Here we present metatranscriptomic and metabolomic data on the physiological response of in situ microbial communities on plant leaf litter to long-term drought and pulse wetting in Californian grass and shrub ecosystems. Wetting litter after a long dry summer caused only subtle shifts in gene expression. On grass litter, communities from the decade-long ambient and reduced precipitation treatments had distinct functional profiles. The most discernable physiological adaptations to drought were production or uptake of compatible solutes to maintain cellular osmotic balance, and synthesis of capsular and extracellular polymeric substances as a mechanism to retain water. The results show a clear functional response to drought in grass litter communities with greater allocation to survival relative to growth that could affect decomposition under drought. In contrast, communities on chemically more diverse and complex shrub litter had smaller physiological differences in response to long-term drought but higher investment in resource acquisition traits across treatments, suggesting that the functional response to drought is constrained by substrate quality. Our findings suggest, for the first time in a field setting, a trade-off between microbial drought stress tolerance, resource acquisition and growth traits in leaf litter microbial communities.

microbiology↗

bioRxiv2019

The conserved metalloprotease invadolysin is present in invertebrate haemolymph and vertebrate blood

We identified invadolysin, a novel essential metalloprotease, for functions in chromosome structure, cell proliferation and migration. Invadolysin also plays an important metabolic role in insulin signaling and is the only protease known to localise to lipid droplets, the main lipid storage organelle in the cell. In silico examination of the protein sequence of invadolysin predicts not only protease and lipase catalytic motifs, but also post-translational modifications and the secretion of invadolysin. Here we show that the protease motif of invadolysin is important for its role in lipid accumulation, but not in glycogen accumulation. The lipase motif does not appear to be functionally important for accumulation of lipids or glycogen. Post-translational modifications likely contribute to modulating the level, localisation or activity of invadolysin. We identified a secreted form of invadolysin in the soluble fraction of invertebrate hemolymph (where we observe sexually dimorphic forms) and also vertebrate plasma, including in the extracellular vesicle fraction. Biochemical analysis for various post-translational modifications demonstrated that secreted invadolysin is both N-and O-glycosylated, but not apparently GPI-linked. The discovery of invadolysin in the extracellular milieu suggests a role for invadolysin in normal organismal physiology.\n\nSummary StatementIn this study, we show that the conserved metalloprotease invadolysin is present in invertebrate hemolymph and vertebrate blood, suggesting the protein may function in organismal physiology.

cell biology↗