Biology subjects

Dragoi, A.-M.

Publications and source records attributed to Dragoi, A.-M..

7 recordsLinked to original sources

bioRxiv2026

Direct interaction between cancer cells and fibroblasts promotes early chemoresistance to standard-of-care drug therapy in small cell lung cancer (SCLC)

Cancer-associated fibroblasts (CAFs) are now recognized as key regulators of tumor progression and therapeutic resistance, yet the cancer cells-fibroblasts crosstalk that ultimately promotes chemoresistance remain incompletely understood. Here, we show that direct physical contact between small cell lung cancer (SCLC) cells and lung fibroblasts induces early resistance to standard-of-care chemotherapeutic agents, etoposide and cisplatin. Using both 2D and 3D co-culture models, we demonstrate that early acquired therapy resistance entails cell-cell contact and cannot be recapitulated by conditioned media alone. Mechanistically, direct interaction promotes transcriptional reprogramming in cancer cells, including upregulation of YAP1 and epithelial-to-mesenchymal transcription factors (EMT-TFs), which partially mediate the resistant phenotype. A high-throughput drug screening identified idarubicin as a compound that retains efficacy despite fibroblast-mediated protection, suggesting it could bypass microenvironment-induced resistance early on. Together, our findings identify direct tumor-fibroblasts contact as an early driver of chemoresistance and highlight a potential therapeutic strategy targeting cell-cell interactions within the tumor microenvironment.

cancer biology↗

bioRxiv2025

The Legionella pneumophila type IVb secretion system effector BinA subverts amino acid transport to sensitize TORC1 signaling in macrophages

Legionella pneumophila is an environmental Gram-negative bacterium that parasitizes unicellular protozoa and can cause severe pulmonary infections when aerosolized bacteria are inhaled by humans. One critical aspect of Legionella pathogenesis is the establishment in the cytosol of infected macrophages of a unique ER-derived vacuole, that requires a sustained supply of host lipids during expansion. Subversion of pro-lipogenic pathways downstream of the metabolic checkpoint kinase mTOR (Mechanistic Target of Rapamycin) are critical for niche expansion. In eukaryotic cells, amino acids sufficiency and growth factor sensory signals converge on mTOR to ensure metabolic processes are coupled to nutrients/energy availability. Legionella can trigger mTOR signaling in infected cells by increasing the intracellular abundance of amino acids through inhibition of host translation. Here, we describe a novel mechanism by which Legionella sensitizes mTOR in infected macrophages. A forward genetic screen identified Lpg0393 protein as a putative bacterial mTOR regulator that contains a VPS9-domain typically found in eukaryotic GEFs (Guanine nucleotide exchange factors) for Rab5 GTPase family members (Rab5/Rab21/Rab22). We uncovered that Lpg0393 lowers the activation threshold for mTOR signaling upon stimulation with arginine or leucine through rewiring of processes upstream of mTOR by removing Rab5-dependency and replacing it with a Rab21/Rab22-dependency. Data from cells expressing either a bacterial or a eukaryotic mTOR sensitizing factor uncovered two distinct intraorganellar Arg/Leu pools that fuel mTOR activation in parallel - one regulated by Rab21/22 and the other by Rab5. Consistent with the role of mTOR in expansion of the Legionella-occupied organelle, deletion of Lpg0393 also resulted in premature vacuolar rupture in a mTOR-dependent manner. All together, we have identified a novel bacterial mTOR regulator and consistent with its reported functions we propose Lpg0393 is named as BinA (Bacterial initiator of TORC1 signaling and an activator of Rab5 family GTPases). Author SummaryLegionella pneumophila - a prototypical vacuolar pathogen - manipulates host lipogenesis to sustain membrane biogenesis, which ensures the integrity of the vacuolar compartment is not compromised as demand for housing capacity increases during bacterial replication. Subversion of the host mTOR kinase signaling, which functions as a central regulatory hub coordinating nutrients sufficiency with metabolic output, is one mechanism by which Legionella increases de novo lipogenesis in infected cells. Here, we report a novel mechanism by which the bacteria sustain mTOR signaling through the actions of the type IV secretion system effector BinA. We found that BinA rewires amino acid transport mechanisms by manipulating Rab5 family GTPase to selectively sensitize mTOR to arginine and leucine but not methionine or glutamine stimulation. mTOR sensitization by BinA revealed a switch in upstream regulators from Rab5 to Rab21/Rab22. Our work provides novel insight into how pathogens exert metabolic control over host cells to maximize intracellular replication.

microbiology↗

bioRxiv2024

Characterization of Neisseria gonorrhoeae colonization of macrophages under distinct polarization states and nutrients environment

Neisseria gonorrhoeae (Ng) is a uniquely adapted human pathogen and the etiological agent of gonorrhea, a sexually transmitted disease. Ng has developed numerous mechanisms to avoid and actively suppress innate and adaptive immune responses. Ng successfully colonizes and establishes topologically distinct colonies in human macrophages and avoids phagocytic killing. During colonization, Ng manipulates the actin cytoskeleton to invade and create an intracellular niche supportive of bacterial replication. The cellular reservoir(s) supporting bacterial replication and persistence in gonorrhea infections are poorly defined. The manner in which gonococci colonize macrophages points to this innate immune phagocyte as a strong candidate for a cellular niche during natural infection. Here we investigate whether nutrients availability and immunological polarization alter macrophage colonization by Ng. Differentiation of macrophages in pro-inflammatory (M1-like) and tolerogenic (M2-like) phenotypes prior to infection reveals that Ng can invade macrophages in all activation states, albeit with lower efficiency in M1-like macrophages. These results suggest that during natural infection, bacteria could invade and grow within macrophages regardless of the nutrients availability and the macrophage immune activation status.

microbiology↗

bioRxiv2024

A nutritional immunity blockade controls extracellular bacterial replication in Legionella pneumophila infections.

The accidental human pathogen Legionella pneumophila (Lp) is the etiological agent for a severe atypical pneumonia known as Legionnaires disease. In human infections and animal models of disease alveolar macrophages are the primary cellular niche that supports bacterial replication within a unique intracellular membrane-bound organelle. The Dot/Icm apparatus - a type IV secretion system that translocates [~]300 bacterial proteins within the cytosol of the infected cell - is a central virulence factor required for intracellular growth. Mutant strains lacking functional Dot/Icm apparatus are transported to and degraded within the lysosomes of infected macrophages. The early foundational work from Dr. Horwitzs group unequivocally established that Legionella does not replicate extracellularly during infection - a phenomenon well supported by experimental evidence for four decades. Our data challenges the dogma in the field by demonstrating that macrophages and monocytes provide the necessary nutrients and support robust Legionella extracellular replication. We show that the previously reported lack of Lp extracellular replication is not a bacteria intrinsic feature but rather a result of robust restriction by serum-derived nutritional immunity factors. Specifically, the host iron-sequestering protein Transferrin was identified as a critical suppressor of Lp extracellular replication in an iron-dependent manner. In iron-overload conditions or in the absence of Transferrin, Lp bypasses growth restriction by IFN{psi}-primed macrophages though extracellular replication. It is well established that certain risk factors associated with development of Legionnaires disease, such as smoking, produce a chronic pulmonary environment of iron-overload. Our work indicates that iron-overload could be an important determinant of severe infection by allowing Lp to overcome nutritional immunity and replicate extracellularly, which in turn would circumvent intracellular cell intrinsic host defenses. Thus, we provide evidence for nutritional immunity as a key underappreciated host defense mechanism in Legionella pathogenesis.

microbiology↗

bioRxiv2023

The intracellular growth of the vacuolar pathogen Legionella pneumophila is dependent on the acyl chain composition of host membranes

Legionella pneumophila is an accidental human bacterial pathogen that infects and replicates within alveolar macrophages causing a severe atypical pneumonia known as Legionnaires disease. As a prototypical vacuolar pathogen L. pneumophila establishes a unique endoplasmic reticulum (ER)-derived organelle within which bacterial replication takes place. Bacteria-derived proteins are deposited in the host cytosol and in the lumen of the pathogen-occupied vacuole via a type IVb (T4bSS) and a type II (T2SS) secretion system respectively. These secretion system effector proteins manipulate multiple host functions to facilitate intracellular survival of the bacteria. Subversion of host membrane glycerophospholipids (GPLs) by the internalized bacteria via distinct mechanisms feature prominently in trafficking and biogenesis of the Legionella-containing vacuole (LCV). Conventional GPLs composed of a glycerol backbone linked to a polar headgroup and esterified with two fatty acids constitute the bulk of membrane lipids in eukaryotic cells. The acyl chain composition of GPLs dictates phase separation of the lipid bilayer and therefore determines the physiochemical properties of biological membranes - such as membrane disorder, fluidity and permeability. In mammalian cells, fatty acids esterified in membrane GPLs are sourced endogenously from de novo synthesis or via internalization from the exogenous pool of lipids present in serum and other interstitial fluids. Here, we exploited the preferential utilization of exogenous fatty acids for GPL synthesis by macrophages to reprogram the acyl chain composition of host membranes and investigated its impact on LCV homeostasis and L. pneumophila intracellular replication. Using saturated fatty acids as well as cis- and trans- isomers of monounsaturated fatty acids we discovered that under conditions promoting lipid packing and membrane rigidification L. pneumophila intracellular replication was significantly reduced. Palmitoleic acid - a C16:1 monounsaturated fatty acid - that promotes membrane disorder when enriched in GPLs significantly increased bacterial replication within human and murine macrophages but not in axenic growth assays. Lipidome analysis of infected macrophages showed that treatment with exogenous palmitoleic acid resulted in membrane acyl chain reprogramming in a manner that promotes membrane disorder and live-cell imaging revealed that the consequences of increasing membrane disorder impinge on several LCV homeostasis parameters. Collectively, we provide experimental evidence that L. pneumophila replication within its intracellular niche is a function of the lipid bilayer disorder and hydrophobic thickness.

microbiology↗

bioRxiv2023

Dual role of CASP8AP2/FLASH in regulating epithelial-to-mesenchymal (EMT) plasticity

Metastasis consists of sequential steps initiated by cancer cells invading from the primary tumor site into neighboring tissues, followed by entry into the circulatory system and completed by extravasation and growth in distal organs where secondary tumors are formed. Circulating tumor cells, thus, encounter and adapt to multiple environmental changes during their transition from the primary to the secondary tumor sites. Epithelial-to-mesenchymal transition (EMT) is a developmental program that consists of loss of epithelial features concomitant with acquisition of mesenchymal features. Activation of EMT in cancer facilitates acquisition of aggressive traits and cancer invasion. EMT plasticity (EMP), the dynamic transition between multiple hybrid states in which cancer cells display both epithelial and mesenchymal phenotypes, confers survival advantages for cancer cells in the constantly changing environment. Therefore, understanding the molecular mechanisms regulating intermediate phenotypic states along the E-M spectrum is critical. Core EMT transcription factors (EMT-TFs), ZEB, SNAI and TWIST families, play an important role in EMT and its plasticity. In the present study we characterize FLASH as a regulator of EMP and multiple EMT-TFs. We demonstrate that loss of FLASH gives rise to a hybrid E/M phenotype with high epithelial scores even in the presence of TGF{beta}, as determined by computational methods using expression of predetermined sets of epithelial and mesenchymal genes. We demonstrate that FLASH is regulating expression of multiple cell junction proteins with an established role in cancer progression and that its role in EMT is independent of its histone biogenesis role. Further, we show that FLASH expression in cancer lines is inversely correlated with the epithelial score, consistent with its function as a repressor of the epithelial phenotype. Nonetheless, activation of a distinct set of mesenchymal markers concomitant with epithelial markers reveals the complex role of FLASH in EMT and indicates that intermediate E/M states could arise from opposing control by FLASH on different families of EMT-TFs.

cancer biology↗

bioRxiv2021

Neisseria gonorrhoeae subverts formin-dependent actin polymerization to colonize human macrophages

Dynamic reorganization of the actin cytoskeleton dictates plasma membrane morphology and is frequently subverted by bacterial pathogens for entry and colonization of host cells. The human-adapted bacterial pathogen Neisseria gonorrhoeae can colonize and replicate when cultured with human macrophages, however the basic understanding of how this process occurs is incomplete. N. gonorrhoeae is the etiological agent of the sexually transmitted disease gonorrhea and tissue resident macrophages are present in the urogenital mucosa which is colonized by the bacteria. We uncovered that when gonococci colonize macrophages they can establish an intracellular or a cell surface-associated niche that support bacterial replication independently. Unlike other intracellular bacterial pathogens, which enter host cells as single bacterium, establish an intracellular niche and then replicate, gonococci invade human macrophages as a colony. Individual diplococci are rapidly phagocytosed by macrophages and transported to lysosomes for degradation. However, we found that surface-associated gonococcal colonies of various sizes can invade macrophages by triggering actin skeleton rearrangement resulting in plasma membrane invaginations that slowly engulf the colony. The resulting intracellular membrane-bound organelle supports robust bacterial replication. The gonococci-occupied vacuoles evaded fusion with the endosomal compartment and were enveloped by a network of actin filaments. We demonstrate that gonococcal colonies invade macrophages via a process mechanistically distinct from phagocytosis that is regulated by the actin nucleating factor FMNL3. Our work provides insights into the gonococci life-cycle in association with human macrophages and defines key host determinants for macrophage colonization.

microbiology↗