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Microbiology (Reading, England) Oct 2023The pathogenicity island 2 (SPI-2)-encoded type III secretion system (injectisome) is assembled following uptake of bacteria into vacuoles in mammalian cells. The...
The pathogenicity island 2 (SPI-2)-encoded type III secretion system (injectisome) is assembled following uptake of bacteria into vacuoles in mammalian cells. The injectisome translocates virulence proteins (effectors) into infected cells. Numerous studies have established the requirement for a functional SPI-2 injectisome for growth of Typhimurium in mouse macrophages, but the results of similar studies involving Typhi and human-derived macrophages are not consistent. It is important to clarify the functions of the . Typhi SPI-2 injectisome, not least because an inactivated SPI-2 injectisome forms the basis for live attenuated . Typhi vaccines that have undergone extensive trials in humans. Intracellular expression of injectisome genes and effector delivery take longer in the . Typhi/human macrophage model than for . Typhimurium and we propose that this could explain the conflicting results. Furthermore, strains of both . Typhimurium and . Typhi contain intact genes for several 'core' effectors. In . Typhimurium these cooperate to regulate the vacuole membrane and contribute to intracellular bacterial replication; similar functions are therefore likely in . Typhi.
Topics: Mice; Animals; Humans; Salmonella typhi; Genomic Islands; Bacterial Proteins; Salmonella typhimurium; Macrophages; Mammals
PubMed: 37862087
DOI: 10.1099/mic.0.001405 -
The New Phytologist Aug 2023Secretion is a fundamental process that plant pathogens utilize to deliver effectors into the host to downregulate immunity and promote infection. Here, we uncover a...
Secretion is a fundamental process that plant pathogens utilize to deliver effectors into the host to downregulate immunity and promote infection. Here, we uncover a fascinating membrane trafficking and delivery route that originates from vacuolar membranes in Magnaporthe oryzae and conduits to the host interface and plasma membrane. To perform such secretory/trafficking function, MoRab7 first recruits the retromer complex to the vacuolar membrane, enabling recognition of a family of SNARE proteins, including MoSnc1. Live-cell imaging confirmed a highly dynamic vesicular trafficking of the retromer complex component(s) and MoSnc1 toward and across the host interface or plasma membrane, and subsequent fusion with target membranes. Interestingly, disruption of the MoRab7/Retromer/MoSnc1-based endolysosomal cascade affects effector secretion and fungal pathogenicity. Taken together, we discovered an unconventional protein and membrane trafficking route starting from the fungal endolysosomes to the M. oryzae-rice interaction interface and dissect the role of MoRab7/Retromer/MoSnc1 sorting machinery in effector secretion during biotrophy and invasive growth in rice blast fungus.
Topics: Endosomes; Protein Transport; Vacuoles; Biological Transport; Cell Membrane; Magnaporthe; Oryza; Fungal Proteins; Plant Diseases
PubMed: 37291895
DOI: 10.1111/nph.19050 -
Cell Reports Dec 2023Atg15 (autophagy-related 15) is a vacuolar phospholipase essential for the degradation of cytoplasm-to-vacuole targeting (Cvt) bodies and autophagic bodies, hereinafter...
Atg15 (autophagy-related 15) is a vacuolar phospholipase essential for the degradation of cytoplasm-to-vacuole targeting (Cvt) bodies and autophagic bodies, hereinafter referred to as intravacuolar/intralysosomal autophagic compartments (IACs), but it remains unknown if Atg15 directly disrupts IAC membranes. Here, we show that the recombinant Chaetomium thermophilum Atg15 lipase domain (CtAtg15(73-475)) possesses phospholipase activity. The activity of CtAtg15(73-475) was markedly elevated by limited digestion. We inserted the human rhinovirus 3C protease recognition sequence and found that cleavage between S159 and V160 was important to activate CtAtg15(73-475). Our molecular dynamics simulation suggested that the cleavage facilitated conformational change around the active center of CtAtg15, resulting in an exposed state. We confirmed that CtAtg15 could disintegrate S. cerevisiae IAC in vivo. Further, both mitochondria and IAC of S. cerevisiae were disintegrated by CtAtg15. This study suggests Atg15 plays a role in disrupting any organelle membranes delivered to vacuoles by autophagy.
Topics: Chaetomium; Fungal Proteins; Phospholipases; Recombinant Proteins; Protein Domains; Molecular Dynamics Simulation; Mitochondria; Intracellular Membranes; Saccharomyces cerevisiae; Protein Structure, Tertiary; Models, Molecular; Enzyme Activation
PubMed: 38118441
DOI: 10.1016/j.celrep.2023.113567 -
Frontiers in Plant Science 2024Plant proteases are essential enzymes that play key roles during crucial phases of plant life. Some proteases are mainly involved in general protein turnover and recycle... (Review)
Review
Plant proteases are essential enzymes that play key roles during crucial phases of plant life. Some proteases are mainly involved in general protein turnover and recycle amino acids for protein synthesis. Other proteases are involved in cell signalling, cleave specific substrates and are key players during important genetically controlled molecular processes. Cathepsin B is a cysteine protease that can do both because of its exopeptidase and endopeptidase activities. Animal cathepsin B has been investigated for many years, and much is known about its mode of action and substrate preferences, but much remains to be discovered about this potent protease in plants. Cathepsin B is involved in plant development, germination, senescence, microspore embryogenesis, pathogen defence and responses to abiotic stress, including programmed cell death. This review discusses the structural features, the activity of the enzyme and the differences between the plant and animal forms. We discuss its maturation and subcellular localisation and provide a detailed overview of the involvement of cathepsin B in important plant life processes. A greater understanding of the cell signalling processes involving cathepsin B is needed for applied discoveries in plant biotechnology.
PubMed: 38463572
DOI: 10.3389/fpls.2024.1305855 -
Cell Reports Aug 2023The nucleolus is the most prominent membraneless organelle within the nucleus. How the nucleolar structure is regulated is poorly understood. Here, we identified two...
The nucleolus is the most prominent membraneless organelle within the nucleus. How the nucleolar structure is regulated is poorly understood. Here, we identified two types of nucleoli in C. elegans. Type I nucleoli are spherical and do not have visible nucleolar vacuoles (NoVs), and rRNA transcription and processing factors are evenly distributed throughout the nucleolus. Type II nucleoli contain vacuoles, and rRNA transcription and processing factors exclusively accumulate in the periphery rim. The NoV contains nucleoplasmic proteins and is capable of exchanging contents with the nucleoplasm. The high-order structure of the nucleolus is dynamically regulated in C. elegans. Faithful rRNA processing is important to prohibit NoVs. The depletion of 27SA rRNA processing factors resulted in NoV formation. The inhibition of RNA polymerase I (RNAPI) transcription and depletion of two conserved nucleolar factors, nucleolin and fibrillarin, prohibits the formation of NoVs. This finding provides a mechanism to coordinate structure maintenance and gene expression.
Topics: Animals; Caenorhabditis elegans; Nuclear Proteins; Vacuoles; Cell Nucleolus; Cell Nucleus; RNA, Ribosomal
PubMed: 37537842
DOI: 10.1016/j.celrep.2023.112915 -
Microorganisms Dec 2023With the prevalence of systemic fungal infections caused by and non- species and their resistance to classical antifungals, there is an urgent need to explore...
With the prevalence of systemic fungal infections caused by and non- species and their resistance to classical antifungals, there is an urgent need to explore alternatives. Herein, we evaluate the impact of the monoterpene carvacrol, a major component of oregano and thyme oils, on clinical and laboratory strains of and . Carvacrol induces a wide range of antifungal effects, including the inhibition of growth and hyphal and biofilm formation. Using biochemical and microscopic approaches, we elucidate carvacrol-induced hyphal inhibition. The significantly reduced survival rates following exposure to carvacrol were accompanied by dose-dependent vacuolar acidification, disrupted membrane integrity, and aberrant morphology. Germ tube assays, used to elucidate the relationship between vacuolar dysfunction and hyphal inhibition, showed that carvacrol significantly reduced hyphal formation, which was accompanied by a defective morphology. Thus, we show a link between vacuolar acidification/disrupted vacuole membrane integrity and compromised candidal morphology/morphogenesis, demonstrating that carvacrol exerts its anti-hyphal activity by altering vacuole integrity.
PubMed: 38138059
DOI: 10.3390/microorganisms11122915 -
Proceedings of the National Academy of... Jul 2023To ensure their survival in the human bloodstream, malaria parasites degrade up to 80% of the host erythrocyte hemoglobin in an acidified digestive vacuole. Here, we...
To ensure their survival in the human bloodstream, malaria parasites degrade up to 80% of the host erythrocyte hemoglobin in an acidified digestive vacuole. Here, we combine conditional reverse genetics and quantitative imaging approaches to demonstrate that the human malaria pathogen employs a heteromultimeric V-ATPase complex to acidify the digestive vacuole matrix, which is essential for intravacuolar hemoglobin release, heme detoxification, and parasite survival. We reveal an additional function of the membrane-embedded V-ATPase subunits in regulating morphogenesis of the digestive vacuole independent of proton translocation. We further show that intravacuolar accumulation of antimalarial chemotherapeutics is surprisingly resilient to severe deacidification of the vacuole and that modulation of V-ATPase activity does not affect parasite sensitivity toward these drugs.
Topics: Animals; Humans; Antimalarials; Adenosine Triphosphatases; Vacuoles; Malaria, Falciparum; Plasmodium falciparum; Parasites
PubMed: 37463201
DOI: 10.1073/pnas.2306420120 -
American Journal of Clinical Pathology Mar 2024To discuss VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome, including the clinical and pathologic features, diagnostic challenges, and...
OBJECTIVES
To discuss VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome, including the clinical and pathologic features, diagnostic challenges, and treatment options.
METHODS
A case-based approach and pertinent literature review were used to highlight the features of VEXAS syndrome, describe how to make the diagnosis, and discuss available therapies.
RESULTS
VEXAS syndrome is an adult-onset, progressive systemic inflammatory disorder with overlapping rheumatologic and hematologic manifestations, including an increased risk of myelodysplastic neoplasms and plasma cell neoplasms. The disorder is associated with a somatic mutation of the X-linked UBA1 gene involved in ubiquitylation, typically involving p.Met41; however, rare variations have been identified outside this region. Patients often present with complex histories and see physicians from multiple specialties before receiving the diagnosis, which is often delayed. Symptoms are related to inflammation as well as cytopenias, particularly macrocytic anemia. Characteristic cytoplasmic vacuoles are present in myeloid (granulocytic, monocytic) and erythroid precursors in the vast majority of cases.
CONCLUSIONS
Either clinicians or pathologists may suspect a diagnosis of VEXAS syndrome depending on the clinical presentation and bone marrow findings. More studies are needed to determine the best therapeutic options, which are currently limited.
PubMed: 38511841
DOI: 10.1093/ajcp/aqae017 -
The EMBO Journal May 2024While the molecular mechanism of autophagy is well studied, the cargoes delivered by autophagy remain incompletely characterized. To examine the selectivity of autophagy...
While the molecular mechanism of autophagy is well studied, the cargoes delivered by autophagy remain incompletely characterized. To examine the selectivity of autophagy cargo, we conducted proteomics on isolated yeast autophagic bodies, which are intermediate structures in the autophagy process. We identify a protein, Hab1, that is highly preferentially delivered to vacuoles. The N-terminal 42 amino acid region of Hab1 contains an amphipathic helix and an Atg8-family interacting motif, both of which are necessary and sufficient for the preferential delivery of Hab1 by autophagy. We find that fusion of this region with a cytosolic protein results in preferential delivery of this protein to the vacuole. Furthermore, attachment of this region to an organelle allows for autophagic delivery in a manner independent of canonical autophagy receptor or scaffold proteins. We propose a novel mode of selective autophagy in which a receptor, in this case Hab1, binds directly to forming isolation membranes during bulk autophagy.
PubMed: 38755257
DOI: 10.1038/s44318-024-00091-8 -
Current Opinion in Microbiology Apr 2024Members of the genus Brucella are the causative agents of brucellosis, a worldwide zoonosis affecting wild and domestic animals and humans. These facultative... (Review)
Review
Members of the genus Brucella are the causative agents of brucellosis, a worldwide zoonosis affecting wild and domestic animals and humans. These facultative intracellular pathogens cause long-lasting chronic infections by evolving sophisticated strategies to counteract, evade, or subvert host bactericidal mechanisms in order to establish a secure replicative niche necessary for their survival. In this review, we present recent findings on selected Brucella effectors to illustrate how this pathogen modulates host cell signaling pathways to gain control of the vacuole, promote the formation of a safe intracellular replication niche, alter host cell metabolism to its advantage, and exploit various cellular pathways to ensure egress from the infected cell.
Topics: Animals; Humans; Brucella; Host-Pathogen Interactions; Brucellosis; Vacuoles
PubMed: 38309247
DOI: 10.1016/j.mib.2024.102427