Biology subjects

Tafesse, F.

Publications and source records attributed to Tafesse, F..

8 recordsLinked to original sources

bioRxiv2026

A critical signaling role for diacylglycerol in phagocytosis of M. tuberculosis

Mycobacterium tuberculosis (Mtb) establishes infection by entering host phagocytes through phagocytosis. While host lipids are known to influence this process, the specific contribution of the signaling lipid diacylglycerol (DAG) remains poorly defined. Here, we identify DAG as a critical regulator of phagocytosis. Disruption of DAG production, through inhibition or genetic deletion of adipose triglyceride lipase (ATGL) and phospholipase C gamma 2 (PLC{gamma}2), two major pathways that generate cellular DAG pools, markedly reduced uptake of both Mtb and zymosan-coated beads. Notably, loss of ATGL or PLC{gamma}2 did not impair receptor trafficking to the cell surface or cargo binding, indicating that DAG is not required for phagocytic recognition or initiation, but instead for a later step in phagosome formation. Mechanistically, cells lacking ATGL or PLC{gamma}2 displayed constitutive phosphoinositide 3-kinase (PI3K) phosphorylation, suggesting that dysregulated intracellular signaling prevents completion of phagocytosis. These findings uncover a previously unappreciated role for DAG biosynthesis in coordinating intracellular signaling required for phagocytosis and provide new insight into host pathways that govern Mtb entry.

microbiology↗

bioRxiv2025

Multi-Omic Profiling Identifies Conserved Metabolic Pathways Critical for SARS-CoV-2 Variants Infection

AO_SCPLOWBSTRACTC_SCPLOWThe rapid evolution of SARS-CoV-2 has led to the emergence of numerous variants with enhanced transmissibility and immune evasion. Despite widespread vaccination, infections persist, and the mechanisms by which SARS-CoV-2 reprograms host metabolism remain incompletely understood. Here, we investigated whether virus-induced lipid remodeling is conserved across variants and whether changes in lipid abundance correlate with alterations in lipid biosynthetic enzymes. Using global untargeted lipidomics and quantitative proteomics, we analyzed A549-ACE2 cells infected with the Delta (B.1.617.2) or Omicron (B.1.1.529) variants and compared them to cells infected with the ancestral WA1 strain. In parallel, we conducted quantitative proteomics to assess virus-induced changes in the host proteome. Our results reveal that SARS-CoV-2 drives a remarkably consistent pattern of metabolic rewiring at both the lipidomic and proteomic levels across all three variants. We mapped changes in the expression of host metabolic enzymes and compared these to corresponding shifts in lipid abundance. This integrative analysis identified key host proteins involved in virus-mediated lipid remodeling, including fatty acid synthase (FASN), lysosomal acid lipase (LIPA), and ORM1-like protein 2 (ORMDL2). Together, these findings highlight conserved metabolic dependencies of SARS-CoV-2 variants and underscore host lipid metabolism as a potential target for broad-spectrum antiviral strategies.

systems biology↗

bioRxiv2025

Analysis of factors that regulate HIV-1 fusion in reverse

Based on observations that HIV-1 envelope (Env) proteins on the surfaces of cells have the capacity to fuse with neighboring cells or enveloped viruses that express CD4 receptors and CXCR4 co-receptors, we tested factors that affect the capacities of lentiviral vectors pseudotyped with CD4 and CXCR4 variants to infect Env-expressing cells. The process, which we refer to as fusion in reverse, involves the binding and activation of cellular Env proteins to fuse membranes with lentiviruses carrying CD4 and CXCR4 proteins. We have found that infection via fusion in reverse depends on cell surface Env levels, is inhibitable by an HIV-1-specific fusion inhibitor, and preferentially requires lentiviral pseudotyping with a glycosylphosphatidylinositol (GPI) anchored CD4 variant, and a cytoplasmic tail-truncated CXCR4 protein. We have demonstrated that latently HIV-1-infected cells can be specifically infected using this mechanism, and that activation of latently infected cells increases infection efficiency. The fusion in reverse approach allowed us to characterize how alteration of CD4 plus CXCR4 lipid membranes affected Env protein activities. In particular, we found that perturbation of membrane cholesterol levels did not affect Env activity. In contrast, viruses assembled in cells deficient for long chain sphingolipids showed increased infectivities, while viruses that incorporated a lipid scramblase were non-infectious. Our results yield new insights as to factors that influence envelope protein functions.

molecular biology↗

bioRxiv2024

A Nanobody Interaction with SARS-CoV-2 Spike Allows the Versatile Targeting of Lentivirus Vectors

While investigating methods to target gene delivery vectors to specific cell types, we examined the potential of using a nanobody against the SARS-CoV-2 Spike protein receptor binding domain to direct lentivirus infection of Spike-expressing cells. Using three different approaches, we found that lentiviruses with surface-exposed nanobody domains selectively infect Spike-expressing cells. The targeting is dependent on the fusion function of Spike, and conforms to a model in which nanobody binding to the Spike protein triggers the Spike fusion machinery. The nanobody-Spike interaction also is capable of directing cell-cell fusion, and the selective infection of nanobody-expressing cells by Spike-pseudotyped lentivirus vectors. Significantly, cells infected with SARS-CoV-2 are efficiently and selectively infected by lentivirus vectors pseudotyped with a chimeric nanobody protein. Our results suggest that cells infected by any virus that forms syncytia may be targeted for gene delivery using an appropriate nanobody or virus receptor mimic. Vectors modified in this fashion may prove useful in the delivery of immunomodulators to infected foci to mitigate the effects of viral infections. IMPORTANCEWe have discovered that lentiviruses decorated on their surfaces with a nanobody against the SARS-CoV-2 Spike protein selectively infect Spike-expressing cells. Infection is dependent on the specificity of the nanobody and the fusion function of the Spike protein, and conforms to a reverse fusion model, in which nanobody binding to Spike triggers the Spike fusion machinery. The nanobody-Spike interaction also can drive cell-cell fusion, and infection of nanobody-expressing cells with viruses carrying the Spike protein. Importantly, cells infected with SARS-CoV-2 are selectively infected with nanobody-decorated lentiviruses. These results suggest that cells infected by any virus that expresses an active receptor-binding fusion protein may be targeted by vectors for delivery of cargoes to mitigate infections.

molecular biology↗

bioRxiv2024

Trifunctional fatty acid derivatives demonstrate the impact of diazirine placement

Functionalized lipid probes are a critical new tool to interrogate the function of individual lipid species, but the structural parameters that constrain their utility have not been thoroughly described. Here, we synthesize three palmitic acid derivatives with a diazirine at different positions on the acyl chain and examine their metabolism, subcellular localization, and protein interactions. We demonstrate that while they produce very similar metabolites and subcellular distributions, probes with the diazirine at either end pulldown distinct subsets of proteins after photo-crosslinking. This highlights the importance of thoughtful diazirine placement when developing probes based on biological molecules.

biochemistry↗

bioRxiv2023

Systematic analysis of the sphingomyelin synthase family in C. elegans

Sphingomyelin (SM) is a major component of mammalian cell membranes and particularly abundant in the myelin sheath that surrounds nerve fibers. Its production is catalyzed by SM synthases SMS1 and SMS2, which interconvert phosphatidylcholine and ceramide to diacylglycerol and SM in the Golgi and at the plasma membrane, respectively. As the lipids participating in this reaction fulfill both structural and signaling functions, SMS enzymes have considerable potential to influence diverse important cellular processes. The nematode Caenorhabditis elegans is an attractive model for studying both animal development and human disease. The organism contains five SMS homologues but none of these have been characterized in any detail. Here, we carried out the first systematic analysis of SMS family members in C. elegans. Using heterologous expression systems, genetic ablation, metabolic labeling and lipidome analyses, we show that C. elegans harbors at least three distinct SM synthases and one ceramide phosphoethanolamine (CPE) synthase. Moreover, C. elegans SMS family members have partially overlapping but also unique subcellular distributions and together occupy all principal compartments of the secretory pathway. Our findings shed light on crucial aspects of sphingolipid metabolism in a valuable animal model and opens avenues for exploring the role of SM and its metabolic intermediates in organismal development.

molecular biology↗

bioRxiv2022

A global lipid map reveals host dependency factors conserved across SARS-CoV-2 variants

A comprehensive understanding of host dependency factors for SARS-CoV-2 remains elusive. We mapped alterations in host lipids following SARS-CoV-2 infection using nontargeted lipidomics. We found that SARS-CoV-2 rewires host lipid metabolism, altering 409 lipid species up to 64-fold relative to controls. We correlated these changes with viral protein activity by transfecting human cells with each viral protein and performing lipidomics. We found that lipid droplet plasticity is a key feature of infection and that viral propagation can be blocked by small-molecule glycerolipid biosynthesis inhibitors. We found that this inhibition was effective against the main variants of concern (alpha, beta, gamma, and delta), indicating that glycerolipid biosynthesis is a conserved host dependency factor that supports this evolving virus.

microbiology↗

bioRxiv2019

Alternative Splicing of MR1 regulates antigen presentation to MAIT cells

Mucosal Associated Invariant T (MAIT) cells can sense intracellular infection by a broad array of pathogens. These cells are activated upon encountering microbial antigen(s) displayed by MR1 on the surface of an infected cell. Human MR1 undergoes alternative splicing. The full length isoform, MR1A, can activate MAIT cells, while the function of the isoforms, MR1B and MR1C, are not well characterized.\n\nIn this report, we sought to characterize these splice variants. Using a transcriptomic analysis in conjunction with qPCR, we find that that MR1A and MR1B transcripts are widely expressed. Despite the widespread expression of MR1A and MR1B, only MR1A can present mycobacterial antigen to MAIT cells. Coexpression of MR1B with MR1A serves to decrease MAIT cell activation following bacterial infection. However, expression of MR1B prior to MR1A lowers total MR1A abundance, suggesting competition between MR1A and MR1B for either ligands or chaperones required for folding and/or trafficking. Finally, we evaluated CD4/CD8 double positive thymocytes expressing surface MR1. Relative MR1A/MR1B expression in MR1-expressing thymocytes is associated with their prevalence.\n\nOur results suggest alternative splicing of MR1 represents a means of regulating MAIT activation in response to microbial ligand.\n\nFundingThis work was supported by NIH T32HL083808 (EK, GAN, EM), VA Merit Award I01CX001562 (MJH), NIH R01AI29976 (MJH), NIH R01AI048090 (DML), NIH R21AI124225-01A1 (FT) and VA Merit Award I01BX000533 (DML). The contents do not represent the views of the U.S. Department of Veterans Affairs or the United States Government.

immunology↗