Microbial Cell最新文献

Fungi were among the first eukaryotes to transition from aquatic to terrestrial life, developing multicellular hyphae, polar growth, and expanded secretomes for nutrient processing, defense, and symbiosis. We present a reliable method for purifying and characterizing extracellular vesicles (EVs) from Aspergillus nidulans and demonstrate that the induction of xylanase C is associated with increased EV release and EV-associated enzymatic activity. Using a mCherry reporter replacing xylanase C, we generalized this effect, showing that reporter induction increases EV production and reporter loading into EVs. This phenomenon primarily depends on the signal peptide (SP), suggesting that the induction of endoplasmic reticulum (ER)- trafficked proteins has a pronounced effect on EV production and cargo loading. We speculate that EV biogenesis may originate at the ER, where ER-translated proteins could be selectively loaded into vesicles and subsequently trafficked directly to the plasma membrane or through multivesicular bodies (MVBs). EV secretion is minimal in the first 24-48 hours but increases later in growth, coinciding with biofilm formation. This timing allows A. nidulans to modify the secretome, adapting it to new nutrient sources.

Heme is an essential molecule for most organisms, yet some parasites, like Trypanosoma cruzi, the causative agent of Chagas disease, cannot synthesize it. These parasites must acquire heme from their hosts, making this process critical for their survival. In the midgut of the insect vector, T. cruzi epimastigotes are exposed to both hemoglobin (Hb) and free heme resulting from its degradation. Despite the importance of this nutrient, how different heme sources influence parasite gene expression remains poorly understood. Here, we showed that heme restitution either as hemin or Hb to heme-starved parasites induces an early and distinct transcriptional response in T. cruzi epimastigotes. Using RNA sequencing at 4- and 24-hours post-supplementation, we identified gene subsets commonly or uniquely regulated by each heme source, including genes putatively linked to heme acquisition and metabolism. The study includes the first focused characterization of CRAL/TRIO domain-containing protein (TcCRAL/TRIO), a novel heme-responsive hemoprotein. Our results provide a more detailed picture of T. cruzi biology and highlights heme acquisition as a promising point of vulnerability to control parasite proliferation.

Autophagy contributes to cellular homeostasis by degrading and recycling intracellular components, especially under nutrient-limited conditions. While autophagy is well characterized under acute starvation in synthetic media in Saccharomyces cerevisiae, its regulation during the stationary phase of prolonged growth in nutrient-rich complex media, when cells experience gradual metabolic shifts and sustained stress, remains poorly understood. In this study, we identified Sir2, an NAD ${}^{+}$ -dependent histone deacetylase, as a key suppressor of autophagy during the stationary phase in YPD complex medium. Using GFP-Atg8 processing as a readout of autophagic flux, we demonstrated that SIR2 deletion led to sustained autophagy activation. Notably, Sir2 selectively inhibited mitophagy, pexophagy, and the Cvt pathway, while non-selective autophagy remained largely unaffected. Transcriptomic analysis revealed that Sir2 facilitates a coordinated entry into quiescence, in part by regulating ribosome biogenesis and nutrient-responsive pathways during the stationary phase. Mechanistically, Sir2 stabilized Ume6, a repressor of ATG8 transcription, thereby limiting autophagic activity. Deletion of SIR2 drastically increased the phosphorylation and stabilization of the mitochondrial receptor Atg32 during the stationary phase, leading to enhanced mitophagy. Additionally, we found that ROS generated by mitophagy enhanced autophagy through a positive feedback loop. Collectively, our findings establish Sir2 as a previously unrecognized regulator of selective autophagy during the stationary phase in complex medium and highlight how cells dynamically control organelle degradation to maintain viability under extended metabolic stress.

Post-translational modifications of microtubules regulate their stability and dynamics. Acetylation of $\alpha$ tubulin at lysine 40 (K40) by $\alpha$ -acetyltransferase ( $\alpha$ TAT) occurs on the luminal side of microtubules, stabilizes their structure, and plays essential roles in various cellular processes across eukaryotes. Apicomplexan parasites include the malaria-causing Plasmodium species and Toxoplasma gondii, both of which possess unusually stable subpellicular microtubules, a set of cytoskeletal filaments underlying the parasite's inner membrane complex. Interestingly, while Toxoplasma gondii and human-infecting Plasmodium species retain both K40 and $\alpha$ TAT, rodent-infecting Plasmodium species have lost $\alpha$ TAT, and K40 has been replaced by glutamine (Q40), a residue that can mimic acetylated lysine. Here, we investigate the role of microtubule acetylation in apicomplexan parasites by generating and characterizing genetic mutants in Plasmodium berghei and Toxoplasma gondii. In Plasmodium berghei, introduction of a Q40K mutation in $\alpha$ 1 tubulin did not affect parasite development or infectivity, suggesting that the absence of K40 acetylation is not detrimental. In Toxoplasma gondii, we confirmed that $\alpha$ TAT is responsible for microtubule acetylation but, contrary to previous reports, its deletion had no impact on parasite growth in vitro. Together, these results indicate that luminal K40 acetylation is not essential for microtubule function in either species, pointing to functional redundancy and highlighting the plasticity of cytoskeletal regulation in apicomplexan parasites.

Glioblastoma is a malignant astrocytic tumor of the brain. A significantly decrease of glioblastoma cell proliferation and survival can be achieved by activating the M2 muscarinic acetylcholine receptor (a G protein-coupled receptor, or GPCR) with two agonist molecules, the orthosteric agonist Arecaidine Propargyl Ester (APE) and the dual-steric agonist Iper-8-naphthalimide (N-8-Iper). In glioblastoma cells, these agonists caused mitochondrial damage and an altered lipid profile. To characterize the mitochondrial dysfunction induced by the muscarinic agonists, we tested APE and N-8-Iper in S. cerevisiae, a yeast model system specifically suitable to study the activity of molecules of pharmaceutical interest on mitochondria. N-8-Iper, but not APE, induced mitochondrial dysfunction in S. cerevisiae cells in a time- and concentration-dependent manner. These results suggest that the agonist N-8-Iper on glioblastoma cell cultures has a direct effect on mitochondrial function. Moreover, since GPCRs are evolutionarily conserved from yeast to humans, these results confirm that the yeast system is a suitable model for studying human GPCRs.

The chronological lifespan of Saccharomyces cerevisiae has significantly contributed to our understanding of aging in eukaryotic cells. However, gaining a genome-wide perspective of this trait remains challenging due to substantial discrepancies observed across genome-wide gene-deletion screens. In this study, we systematically compiled nine chronological-lifespan datasets and evaluated how shared experimental variables influenced screen variability. Furthermore, we performed a meta-analysis to compile a ranked catalog of key processes and regulators driving chronological longevity in yeast, ensuring their robustness across diverse experimental setups. These consistent chronological aging factors were enriched in genes associated with yeast replicative lifespan and orthologs implicated in aging across other model organisms. Functional analysis revealed that the downstream cellular mechanisms underlying chronological longevity in yeast align with well-established, universal hallmarks of aging. Importantly, we identified transcriptional regulators associated with these consistent genetic factors, uncovering potential global and local modulators of chronological aging. Our findings provide an integrated view of the core genetic landscape underlying aging in yeast, highlighting the value of the chronological lifespan paradigm for investigating conserved mechanisms of aging.

Eucaryotic cell functioning and development depend on the concerted activity of its organelles. In the model fungus Podospora anserina, sexual development involves a dynamic regulation of mitochondria, peroxisomes and the endoplasmic reticulum (ER), suggesting that their activity during this process is coordinated. The ER-Mitochondria Encounter Structure (ERMES) is a tether complex composed of the ER protein Mmm1 and the mitochondrial proteins Mdm10, Mdm12 and Mdm34, which mediates membrane contact-site formation between these organelles. This complex also mediates interactions between mitochondria and peroxisomes. Here we analyzed the role of the ERMES complex during P. anserina development. By studying a thermosensitive MDM10 mutant, we show that MDM10 is required for mitochondrial morphology and distribution, as well as for peroxisome membrane-remodeling and motility. We discovered that lipid droplets exhibit a subapical hyphal localization, which depends on MDM10. MDM10 is also required for ER shaping and dynamics, notably of the apical ER domains of the polarized-growing hyphal region, in a process that involves the activity of the protein YOP1. We also show that apical ER shaping involves a Spitzenkörper-associated membrane traffic, which implicates MDM10, and that the mycelial growth defect of mdm10 mutants is exacerbated when the ER-shaping proteins YOP1 or RTN1 are loss. Finaly, we show that MMM1 is strictly required for mycelial growth and sexual development, suggesting that its activity is essential. Our results show that the activity of distinct organelles depends on the ERMES complex, and that the function of this complex is critical for P. anserina growth and development.

Mitochondria are essential organelles that form a dynamic network within cells. The fusion, fission, and transport processes among mitochondria must reach a balance, which is achieved through complex regulatory mechanisms. These dynamic processes and regulatory pathways are highly conserved across species and are coordinated to help cells respond to environmental stress. The budding yeast Saccharomyces cerevisiae has become an important model organism for studying mitochondria dynamics due to its genetic tractability and the conservation of key mitochondrial regulators. Previous research on mitochondria dynamics in yeast has provided valuable insights into the regulatory pathways in eukaryotic cells. It has helped to elucidate the mechanisms related to diseases associated with disrupted mitochondria dynamics. This review explores the molecular mechanisms underlying mitochondria dynamics and their physiological roles in Saccharomyces cerevisiae. The knowledge we learned from the primary eukaryotic yeast cell will aid us in advancing future research on the regulatory mechanisms of mitochondria in both health and disease.

Programmed cell death (PCD) in unicellular organisms is not well characterized. This study investigated the transcriptomic response of Acanthamoeba castellanii to G418-induced PCD, focusing on the role of alternative splicing (AS). RNA sequencing revealed extensive transcriptional changes, affecting approximately 70% of annotated genes over six hours of treatment. This analysis also highlighted significant alterations in pathways related to cell cycle, proteolysis, and RNA splicing. Analysis of AS events identified 18,748 differentially spliced events, predominantly intron retention (IR). Interestingly, retained introns displayed a 3' bias in untreated cells, a pattern that shifted towards uniform distribution throughout the gene body during PCD. Additionally, we characterized retained introns during trophozoite stage and during PCD of the amoeba. Correlational analysis revealed a significant negative correlation between IR and transcript levels, suggesting a complex interplay between transcriptional and post-transcriptional regulation. The predominance of IR, coupled with its dynamic positional shift during PCD, points to a novel regulatory mechanism in A. castellanii PCD. These findings provide insights into the molecular mechanisms underlying PCD in this organism, potentially identifying new therapeutic targets and allowing us a better understanding of such process in A. castellanii, a facultative human pathogen.

Ankylosing spondylitis (AS) is a chronic inflammatory disease with complex pathogenesis influenced by genetic, immunological and environmental factors. Recent evidence suggests that gut microbiota significantly contributes to AS etiopathogenesis. Dysbiosis and altered immune responses in the gut potentially trigger or exacerbate the disease through intestinal barrier disruption, alteration of the IL-23/17 axis and metabolite production. This review explores the growing role of gut microbiota in AS and its potential to reshape targeted treatment strategies and facilitate development of adjunct therapies to address disease onset and progression. AS is a multifactorial disease in which gut dysbiosis plays a significant role influencing immune regulation notably through the IL-23/17 pathway. Alterations in gut microbiota composition and its metabolites contribute to systemic inflammation, reinforcing a self-perpetuating feedback loop between gut and spinal inflammation that drives disease progression. Emerging evidence has linked microbial mechanisms to HLA-B27 misfolding promoting endoplasmic reticulum stress and triggering molecular mimicry through gut microbial-associated molecular patterns further contributing to AS pathogenesis. Given the crucial role of gut microbiota in AS, targeting microbiota imbalances presents a promising avenue for novel therapeutic strategies. Although it remains unclear whether gut inflammation and microbial changes precedes AS onset, current evidence suggests an ongoing cycle of autoimmune inflammation involving both the gut and joints. Further research, particularly longitudinal studies, are needed to better understand the gut-joint axis and its potential therapeutic implications in AS management.