Biology subjects

Svard, S.

Publications and source records attributed to Svard, S..

4 recordsLinked to original sources

bioRxiv2026

Adenosine impairs T cell function via activation of purine salvage pathway and AMP-induced inhibition of pyrimidine nucleotide biosynthesis

Extracellular adenosine (ADO) is a well-established immune checkpoint mediator suppressing T cells via activation of A2A receptors, yet intracellular mechanisms of ADO action remain less understood. Here, we show that activated human T cells transport extracellular ADO through equilibrative nucleoside transporter 1 (ENT1) and metabolize it through ATP salvage pathway. The generated ADO metabolite AMP inhibits UMP synthase (UMPS), the rate-limiting enzyme of de novo pyrimidine biosynthesis, leading to diminished ATP production via conventional bioenergetic pathways, increased apoptosis, and impaired effector functions of T cells. Flow cytometric and single-cell transcriptomic analyses further revealed that ADO restrains the exit of naive T cells from quiescence. All effects of ADO were phenocopied by treating T cells with the inhibitors of UMPS and reversed after pharmacological blockage of ENT1 or uridine supplementation. Additional molecular docking, molecular dynamics simulations, and free-energy analyses indicate that AMP can occupy the orotidine 5'-monophosphate (OMP) decarboxylase catalytic site of UMPS with the same anchoring contacts as substrate OMP and product UMP, providing a structural rationale for direct AMP-mediated inhibition of pyrimidine biosynthesis. These findings demonstrate that immunosuppressive effects of ADO extend beyond canonical adenosinergic signaling and involve cellular ADO uptake and modulation of purine and pyrimidine metabolism.

immunology↗

bioRxiv2026

A pooled image-based CRISPR screen identifies EAF1 as a T. gondii modulator of ESCRT subversion.

Intracellular pathogens remodel host cells by redirecting cellular machinery to the host-pathogen interface. The protozoan parasite Toxoplasma gondii co-opts host ESCRT proteins at the parasitophorous vacuole membrane (PVM), where they support budding of host-derived vesicles into the vacuole. Yet the parasite effectors that direct this process remain largely unknown. Here we developed spaCR (spatial phenotype analysis of CRISPR-Cas9 screens), a pooled image-based screening framework that combines deep-learning classification of single-cell spatial phenotypes with well-level barcode genotyping and regression-based deconvolution of gene effects. Screening T. gondii secretory proteins recovered the known TSG101 recruiter GRA14 and identified an uncharacterized effector, ESCRT-association factor 1 (EAF1), that promoted TSG101 recruitment to the PVM. Targeted deletion confirmed its role across Type I and II lineages, and IP-MS recovered ESCRT-I and ESCRT-III components, including TSG101. Together, these findings identify EAF1 as an ESCRT-associated parasite effector and establish spaCR as a general framework for linking CRISPR perturbations to spatial phenotypes.

microbiology↗

bioRxiv2022

The late ISC pathway interactome reveals mitosomal-cytoplasmic crosstalk in Giardia intestinalis

Mitochondrial metabolism is entirely dependent on the biosynthesis of the [4Fe-4S] clusters, which are part of the subunits of the respiratory chain. The mitochondrial late ISC pathway mediates the formation of these clusters from simpler [2Fe-2S] molecules and transfers them to client proteins. Here, we characterized the late ISC pathway in one of the simplest mitochondria, mitosomes, of the anaerobic protist Giardia intestinalis that lost the respiratory chain and other hallmarks of mitochondria. Identification of the late ISC interactome revealed unexpected involvement of the aerobic marker protein BolA and specific interaction of IscA with the outer mitosomal membrane. Although we confirmed that the synthesis of the Fe-S cluster remained the only metabolic role of mitosomes, we also showed that mitosomes lack client proteins that require the [4Fe-4S] cluster. Instead, by knocking out the bolA gene from the G. intestinalis genome, we showed that, unlike aerobic mitochondria, the late ISC mitosomal pathway is involved in the assembly of cytosolic [4Fe-4S] clusters. Thus, this work reveals an unexpected link between the formation of mitochondrial and cytosolic [4Fe- 4S] clusters. This may either be a consequence of mitochondrial adaptation to life without oxygen, or it represents a general metabolic coupling that has not been previously observed in the complex mitochondrial metabolism of aerobes.

cell biology↗

bioRxiv2022

Combined nanometric and phylogenetic analysis of unique endocytic compartments in Giardia lamblia sheds light on the evolution of endocytosis in Fornicata

Giardia lamblia, a parasitic protist of the metamonada supergroup, has evolved one of the most diverged endocytic compartment systems investigated so far. Peripheral endocytic compartments, currently known as peripheral vesicles or vacuoles (PVs), perform bulk uptake of fluid phase material which is then digested and sorted either to the cell cytosol or back to the extracellular space. Here, we present a quantitative morphological characterization of these organelles using volumetric electron microscopy and super-resolution microscopy (SRM). We defined a morphological classification for the heterogenous population of PVs and performed a comparative analysis of PVs and endosome-like organelles in representatives of phylogenetically-related taxa, Spironucleus spp. and Tritrichomonas foetus. To investigate the as-yet insufficiently understood connection between PVs and clathrin assemblies in G. lamblia, we further performed an in-depth search for two key elements of the endocytic machinery, clathrin heavy chain (CHC) and clathrin light chain (CLC) across different lineages in Metamonada. Our data point to the loss of a bona fide CLC in the last Fornicata common ancestor (LFCA) with the emergence of a protein analogous to CLC (GlACLC) in the Giardia genus. Taken together, this provides the first comprehensive nanometric view of Giardias endocytic system architecture and sheds light on the evolution of GLACLC analogues in the Fornicata supergroup and, specific to Giardia, as a possible adaptation to the formation and maintenance of stable clathrin assemblies at PVs.

cell biology↗