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The ISME Journal Jan 2024Previous studies have revealed tight metabolic complementarity between bivalves and their endosymbiotic chemosynthetic bacteria, but little is known about their...
Previous studies have revealed tight metabolic complementarity between bivalves and their endosymbiotic chemosynthetic bacteria, but little is known about their interactions with ectosymbionts. Our analysis of the ectosymbiosis between a deep-sea scallop (Catillopecten margaritatus) and a gammaproteobacterium showed that bivalves could be highly interdependent with their ectosymbionts as well. Our microscopic observation revealed abundant sulfur-oxidizing bacteria (SOB) on the surfaces of the gill epithelial cells. Microbial 16S rRNA gene amplicon sequencing of the gill tissues showed the dominance of the SOB. An analysis of the SOB genome showed that it is substantially smaller than its free-living relatives and has lost cellular components required for free-living. Genomic and transcriptomic analyses showed that this ectosymbiont relies on rhodanese-like proteins and SOX multienzyme complex for energy generation, mainly on the Calvin-Benson-Bassham (CBB) cycle and peripherally on a phosphoenolpyruvate carboxylase for carbon assimilation. Besides, the symbiont encodes an incomplete tricarboxylic acid (TCA) cycle. Observation of the scallop's digestive gland and its nitrogen metabolism pathways indicates it does not fully rely on the ectosymbiont for nutrition. Analysis of the host's gene expression provided evidence that it could offer intermediates for the ectosymbiont to complete its TCA cycle and some amino acid synthesis pathways using exosomes, and its phagosomes, endosomes, and lysosomes might be involved in harvesting nutrients from the symbionts. Overall, our study prompts us to rethink the intimacy between the hosts and ectosymbionts in Bivalvia and the evolution of chemosymbiosis in general.
Topics: Animals; Symbiosis; RNA, Ribosomal, 16S; Bacteria; Genomics; Bivalvia; Pectinidae; Genome, Bacterial; Phylogeny
PubMed: 38531780
DOI: 10.1093/ismejo/wrae048 -
American Journal of Respiratory Cell... Jun 2024
Topics: TRPV Cation Channels; Humans; Animals; Phagosomes; Mice
PubMed: 38502902
DOI: 10.1165/rcmb.2024-0070ED -
Molecular Metabolism May 2024Exposure of adipocytes to 'cool' temperatures often found in the periphery of the body induces expression of Stearoyl-CoA Desaturase-1 (Scd1), an enzyme that converts...
OBJECTIVE
Exposure of adipocytes to 'cool' temperatures often found in the periphery of the body induces expression of Stearoyl-CoA Desaturase-1 (Scd1), an enzyme that converts saturated fatty acids to monounsaturated fatty acids. The goal of this study is to further investigate the roles of Scd in adipocytes.
METHOD
In this study, we employed Scd1 knockout cells and mouse models, along with pharmacological Scd1 inhibition to dissect the enzyme's function in adipocyte physiology.
RESULTS
Our study reveals that production of monounsaturated lipids by Scd1 is necessary for fusion of autophagosomes to lysosomes and that with a Scd1-deficiency, autophagosomes accumulate. In addition, Scd1-deficiency impairs lysosomal and autolysosomal acidification resulting in vacuole accumulation and eventual cell death. Blocking autophagosome formation or supplementation with monounsaturated fatty acids maintains vitality of Scd1-deficient adipocytes.
CONCLUSION
This study demonstrates the indispensable role of Scd1 in adipocyte survival, with its inhibition in vivo triggering autophagy-dependent cell death and its depletion in vivo leading to the loss of bone marrow adipocytes.
Topics: Stearoyl-CoA Desaturase; Animals; Mice; Autophagy; Adipocytes; Fatty Acids, Monounsaturated; Mice, Knockout; Mice, Inbred C57BL; Lysosomes; Cell Survival; 3T3-L1 Cells; Male; Lipid Metabolism; Autophagosomes
PubMed: 38492843
DOI: 10.1016/j.molmet.2024.101916 -
Communications Biology Mar 2024VPS37A, an ESCRT-I complex component, is required for recruiting a subset of ESCRT proteins to the phagophore for autophagosome closure. However, the mechanism by which...
VPS37A, an ESCRT-I complex component, is required for recruiting a subset of ESCRT proteins to the phagophore for autophagosome closure. However, the mechanism by which VPS37A is targeted to the phagophore remains obscure. Here, we demonstrate that the VPS37A N-terminal domain exhibits selective interactions with highly curved membranes, mediated by two membrane-interacting motifs within the disordered regions surrounding its Ubiquitin E2 variant-like (UEVL) domain. Site-directed mutations of residues in these motifs disrupt ESCRT-I localization to the phagophore and result in defective phagophore closure and compromised autophagic flux in vivo, highlighting their essential role during autophagy. In conjunction with the UEVL domain, we postulate that these motifs guide a functional assembly of the ESCRT machinery at the highly curved tip of the phagophore for autophagosome closure. These results advance the notion that the distinctive membrane architecture of the cup-shaped phagophore spatially regulates autophagosome biogenesis.
Topics: Autophagosomes; Autophagy; Intracellular Membranes; Endosomes; Endosomal Sorting Complexes Required for Transport
PubMed: 38491121
DOI: 10.1038/s42003-024-06026-7 -
Scientific Reports Mar 2024Pseudomonas aeruginosa often colonizes immunocompromised patients, causing acute and chronic infections. This bacterium can reside transiently inside cultured...
Pseudomonas aeruginosa often colonizes immunocompromised patients, causing acute and chronic infections. This bacterium can reside transiently inside cultured macrophages, but the contribution of the intramacrophic stage during infection remains unclear. MgtC and OprF have been identified as important bacterial factors when P. aeruginosa resides inside cultured macrophages. In this study, we showed that P. aeruginosa mgtC and oprF mutants, particular the latter one, had attenuated virulence in both mouse and zebrafish animal models of acute infection. To further investigate P. aeruginosa pathogenesis in zebrafish at a stage different from acute infection, we monitored bacterial load and visualized fluorescent bacteria in live larvae up to 4 days after infection. Whereas the attenuated phenotype of the oprF mutant was associated with a rapid elimination of bacteria, the mgtC mutant was able to persist at low level, a feature also observed with the wild-type strain in surviving larvae. Interestingly, these persistent bacteria can be visualized in macrophages of zebrafish. In a short-time infection model using a macrophage cell line, electron microscopy revealed that internalized P. aeruginosa wild-type bacteria were either released after macrophage lysis or remained intracellularly, where they were localized in vacuoles or in the cytoplasm. The mgtC mutant could also be detected inside macrophages, but without causing cell damage, whereas the oprF mutant was almost completely eliminated after phagocytosis, or localized in phagolysosomes. Taken together, our results show that the main role of OprF for intramacrophage survival impacts both acute and persistent infection by this bacterium. On the other hand, MgtC plays a clear role in acute infection but is not essential for bacterial persistence, in relation with the finding that the mgtC mutant is not completely eliminated by macrophages.
Topics: Humans; Animals; Mice; Bacterial Proteins; Zebrafish; Pseudomonas Infections; Phagocytosis; Phagosomes; Pseudomonas aeruginosa
PubMed: 38491095
DOI: 10.1038/s41598-024-56725-8 -
Cell Apr 2024Microglia are brain-resident macrophages that shape neural circuit development and are implicated in neurodevelopmental diseases. Multiple microglial transcriptional...
Microglia are brain-resident macrophages that shape neural circuit development and are implicated in neurodevelopmental diseases. Multiple microglial transcriptional states have been defined, but their functional significance is unclear. Here, we identify a type I interferon (IFN-I)-responsive microglial state in the developing somatosensory cortex (postnatal day 5) that is actively engulfing whole neurons. This population expands during cortical remodeling induced by partial whisker deprivation. Global or microglial-specific loss of the IFN-I receptor resulted in microglia with phagolysosomal dysfunction and an accumulation of neurons with nuclear DNA damage. IFN-I gain of function increased neuronal engulfment by microglia in both mouse and zebrafish and restricted the accumulation of DNA-damaged neurons. Finally, IFN-I deficiency resulted in excess cortical excitatory neurons and tactile hypersensitivity. These data define a role for neuron-engulfing microglia during a critical window of brain development and reveal homeostatic functions of a canonical antiviral signaling pathway in the brain.
Topics: Animals; Mice; Interferon Type I; Microglia; Neurons; Zebrafish; Brain
PubMed: 38490196
DOI: 10.1016/j.cell.2024.02.020 -
Function (Oxford, England) 2024The skeletal system is crucial for supporting bodily functions, protecting vital organs, facilitating hematopoiesis, and storing essential minerals. Skeletal... (Review)
Review
The skeletal system is crucial for supporting bodily functions, protecting vital organs, facilitating hematopoiesis, and storing essential minerals. Skeletal homeostasis, which includes aspects such as bone density, structural integrity, and regenerative processes, is essential for normal skeletal function. Autophagy, an intricate intracellular mechanism for degrading and recycling cellular components, plays a multifaceted role in bone metabolism. It involves sequestering cellular waste, damaged proteins, and organelles within autophagosomes, which are then degraded and recycled. Autophagy's impact on bone health varies depending on factors such as regulation, cell type, environmental cues, and physiological context. Despite being traditionally considered a cytoplasmic process, autophagy is subject to transcriptional and epigenetic regulation within the nucleus. However, the precise influence of epigenetic regulation, including DNA methylation, histone modifications, and non-coding RNA expression, on cellular fate remains incompletely understood. The interplay between autophagy and epigenetic modifications adds complexity to bone cell regulation. This article provides an in-depth exploration of the intricate interplay between these two regulatory paradigms, with a focus on the epigenetic control of autophagy in bone metabolism. Such an understanding enhances our knowledge of bone metabolism-related disorders and offers insights for the development of targeted therapeutic strategies.
Topics: Humans; Epigenesis, Genetic; Autophagy; Homeostasis; Autophagosomes; Bone Density; Bone Diseases, Metabolic
PubMed: 38486976
DOI: 10.1093/function/zqae004 -
International Journal of Molecular... Mar 2024Ceramides regulate phagocytosis; however, their exact function remains poorly understood. Here, we sought (1) to develop genetically encoded fluorescent tools for...
Ceramides regulate phagocytosis; however, their exact function remains poorly understood. Here, we sought (1) to develop genetically encoded fluorescent tools for imaging ceramides, and (2) to use them to examine ceramide dynamics during phagocytosis. Fourteen enhanced green fluorescent protein (EGFP) fusion constructs based on four known ceramide-binding domains were generated and screened. While most constructs localized to the nucleus or cytosol, three based on the CA3 ceramide-binding domain of kinase suppressor of ras 1 (KSR1) localized to the plasma membrane or autolysosomes. C-terminally tagged CA3 with a vector-based (C-KSR) or glycine-serine linker (C-KSR-GS) responded sensitively and similarly to ceramide depletion and accumulation using a panel of ceramide modifying drugs, whereas N-terminally tagged CA3 (N-KSR) responded differently to a subset of treatments. Lipidomic and liposome microarray analysis suggested that, instead, N-KSR may preferentially bind glucosyl-ceramide. Additionally, the three probes showed distinct dynamics during phagocytosis. Despite partial autolysosomal degradation, C-KSR and C-KSR-GS accumulated at the plasma membrane during phagocytosis, whereas N-KSR did not. Moreover, the weak recruitment of C-KSR-GS to the endoplasmic reticulum and phagosomes was enhanced through overexpression of the endoplasmic reticulum proteins stromal interaction molecule 1 (STIM1) and Sec22b, and was more salient in dendritic cells. The data suggest these novel probes can be used to analyze sphingolipid dynamics and function in living cells.
Topics: Ceramides; Fluorescent Dyes; Signal Transduction; Phagocytosis; Protein Kinases
PubMed: 38474242
DOI: 10.3390/ijms25052996 -
International Journal of Molecular... Feb 2024infects human monocytes or macrophages and causes human monocytic ehrlichiosis (HME), an emerging life-threatening zoonosis. After internalization, resides in...
infects human monocytes or macrophages and causes human monocytic ehrlichiosis (HME), an emerging life-threatening zoonosis. After internalization, resides in membrane-bound inclusions, -containing vesicles (ECVs), which have early endosome-like characteristics and fuse with early autophagosomes but not lysosomes, to evade host innate immune microbicidal mechanisms and obtain nutrients for bacterial intracellular growth. The mechanisms exploited by to modulate intracellular vesicle trafficking in host cells have not been comprehensively studied. Here, we demonstrate that type IV secretion system (T4SS) effector Etf-3 induces upregulation in host cells and that RAB15, which is localized on ECVs, inhibits ECV fusion with lysosomes and induces autophagy. We found that infection upregulated expression using qRT-PCR, and RAB15 was colocalized with using confocal microscopy. Silence of RAB15 using siRNA enhanced ECV maturation to late endosomes and fusion with lysosomes, as well as inhibited host cell autophagy. Overexpression of Etf-3 in host cells specifically induced upregulation and autophagy. Our findings deepen the understanding of pathogenesis and adaptation in hosts as well as the function of RAB15 and facilitate the development of new therapeutics for HME.
Topics: Humans; Ehrlichia chaffeensis; Up-Regulation; Autophagosomes; Autophagy; Defense Mechanisms
PubMed: 38473798
DOI: 10.3390/ijms25052551 -
Biochemical Pharmacology Apr 2024Bladder cancer (BC) is the most common cancer of the urinary tract, with poor survival, high recurrence rates, and lacking of targeted drugs. In this study, we...
Bladder cancer (BC) is the most common cancer of the urinary tract, with poor survival, high recurrence rates, and lacking of targeted drugs. In this study, we constructed a library to screen compounds inhibiting bladder cancer cells growth. Among them, SRT1720 was identified to inhibit bladder cancer cell proliferation in vitro and in vivo. SRT1720 treatment also suppressed bladder cancer cells migration, invasion and induced apoptosis. Mechanism studies shown that SRT1720 promoted autophagosomes accumulation by inducing early-stage autophagy but disturbed the late-stage of autophagy by blocking fusion of autophagosomes and lysosomes. SRT1720 appears to induce autophagy related proteins expression and alter autophagy-related proteins acetylation to impede the autophagy flux. LAMP2, an important lysosomal associated membrane protein, may mediate SRT1720-inhibited autophagy flux as SRT1720 treatment significantly deacetylated LAMP2 which may influence its activity. Taken together, our results demonstrated that SRT1720 mediated apoptosis and autophagy flux inhibition may be a novel therapeutic strategy for bladder cancer treatment.
Topics: Humans; Autophagy; Autophagosomes; Heterocyclic Compounds, 4 or More Rings; Urinary Bladder Neoplasms; Apoptosis; Lysosomes
PubMed: 38458329
DOI: 10.1016/j.bcp.2024.116111