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Nature Structural & Molecular Biology Feb 2024Autophagy is a lysosome-dependent degradation pathway essential for cellular homeostasis, which decreases with age. However, it is unclear how aging induces autophagy...
Autophagy is a lysosome-dependent degradation pathway essential for cellular homeostasis, which decreases with age. However, it is unclear how aging induces autophagy decline. Here we show the role of protein S-palmitoylation in autophagy. We identify the palmitoyl acyltransferase DHHC5 as a regulator of autophagy by mediating the palmitoylation of beclin 1, which in turn promotes the formation of ATG14L-containing class III phosphatidylinositol-3-kinase complex I and its lipid kinase activity by promoting the hydrophobic interactions between beclin 1 and adapter proteins ATG14L and VPS15. In aging brains of human and nonhuman primate, the levels of DHHC5 exhibit a marked decrease in expression. We show that DHHC5 deficiency in neurons leads to reduced cellular protein homeostasis in two established murine models of Alzheimer's disease, which exaggerates neurodegeneration in an autophagy-dependent manner. These findings identify reduction of DHHC5-mediated beclin 1 S-palmitoylation as an underlying mechanism by which aging induces autophagy decline.
Topics: Animals; Humans; Mice; Acyltransferases; Apoptosis Regulatory Proteins; Autophagy; Beclin-1; Lipoylation; Membrane Proteins; Phosphorylation
PubMed: 38177673
DOI: 10.1038/s41594-023-01163-9 -
Molecular & Cellular Proteomics : MCP Jan 2024A significant portion of mammalian proteomes is secreted to the extracellular space to fulfill crucial roles in cell-to-cell communication. To best recapitulate the... (Review)
Review
A significant portion of mammalian proteomes is secreted to the extracellular space to fulfill crucial roles in cell-to-cell communication. To best recapitulate the intricate and multi-faceted crosstalk between cells in a live organism, there is an ever-increasing need for methods to study protein secretion in model systems that include multiple cell types. In addition, posttranslational modifications further expand the complexity and versatility of cellular communication. This review aims to summarize recent strategies and model systems that employ cellular coculture, chemical biology tools, protein enrichment, and proteomic methods to characterize the composition and function of cellular secretomes. This is all geared towards gaining better understanding of organismal biology in vivo mediated by secretory signaling.
Topics: Animals; Cell Communication; Mammals; Proteome; Proteomics; Secretome
PubMed: 38081362
DOI: 10.1016/j.mcpro.2023.100692 -
BMC Microbiology Apr 2024Staphylococcus aureus secretes a variety of proteins including virulence factors that cause diseases. PrsA, encoded by many Gram-positive bacteria, is a...
BACKGROUND
Staphylococcus aureus secretes a variety of proteins including virulence factors that cause diseases. PrsA, encoded by many Gram-positive bacteria, is a membrane-anchored lipoprotein that functions as a foldase to assist in post-translocational folding and helps maintain the stability of secreted proteins. Our earlier proteomic studies found that PrsA is required for the secretion of protein A, an immunoglobulin-binding protein that contributes to host immune evasion. This study aims to investigate how PrsA influences protein A secretion.
RESULTS
We found that in comparison with the parental strain HG001, the prsA-deletion mutant HG001ΔprsA secreted less protein A. Deleting prsA also decreased the stability of exported protein A. Pulldown assays indicated that PrsA interacts with protein A in vivo. The domains in PrsA that interact with protein A are mapped to both the N- and C-terminal regions (NC domains). Additionally, the NC domains are essential for promoting PrsA dimerization. Furthermore, an immunoglobulin-binding assay revealed that, compared to the parental strain HG001, fewer immunoglobulins bound to the surface of the mutant strain HG001ΔprsA.
CONCLUSIONS
This study demonstrates that PrsA is critical for the folding and secretion of protein A. The information derived from this study provides a better understanding of virulent protein export pathways that are crucial to the pathogenicity of S. aureus.
Topics: Humans; Staphylococcus aureus; Bacterial Proteins; Staphylococcal Protein A; Protein Folding; Membrane Proteins; Proteomics; Staphylococcal Infections; Immunoglobulins
PubMed: 38566014
DOI: 10.1186/s12866-024-03268-7 -
Veterinary Parasitology Apr 2024Tick saliva has a pivotal function in parasitism. It has pharmacological and immunomodulatory properties, with several proteins reported in its composition....
Tick saliva has a pivotal function in parasitism. It has pharmacological and immunomodulatory properties, with several proteins reported in its composition. Thyroglobulin type-1 domain protease inhibitor (thyropin)-like proteins are found in tick saliva, but their function, properties and structures are poorly characterized. It has been reported that thyropins are capable of inhibiting cysteine peptidases present in antigen-presenting cells. To elucidate the role of thyropin-like proteins in ticks, we conducted in silico analysis and cloned an open reading frame from a thyropin-like protein found in Rhipicephalus microplus. The recombinant protein was successfully expressed, followed by immunological characterization and a vaccine trial against Rhipicephalus sanguineus in rabbits. Several differences are observed between thyropin-like proteins from hard and soft ticks, especially the number of thyroglobulin domains and predicted glycosylation pattern. Thyropin-like proteins also differ between postriata and metastriata ticks, the latter having a coil-domain at the C-terminal region and high number of predicted glycosylation sites. Overall, the data suggested divergence in thyropin-like proteins functions among ticks. The recombinant thyropin-like protein is immunogenic and the antibodies against it are able to recognize the native protein in tick saliva and tissues. While the recombinant protein does not elicit a protective response against R. sanguineus infestation, its characterization paves the way for further investigations aimed at determining the precise function of this protein in tick physiology.
Topics: Animals; Rabbits; Recombinant Proteins; Rhipicephalus; Rhipicephalus sanguineus; Saliva; Thyroglobulin; Tick Infestations; Clinical Trials, Veterinary as Topic
PubMed: 38290194
DOI: 10.1016/j.vetpar.2024.110136 -
Advances in Nutrition (Bethesda, Md.) Jan 2024Among exclusively breastfed infants, human milk (HM) provides complete nutrition in the first mo of life and remains an important energy source as long as breastfeeding...
Among exclusively breastfed infants, human milk (HM) provides complete nutrition in the first mo of life and remains an important energy source as long as breastfeeding continues. Consisting of digestible carbohydrates, proteins, and amino acids, as well as fats and fatty acids, macronutrients in human milk have been well studied; however, many aspects related to their relationship to growth in early life are still not well understood. We systematically searched Medline, EMBASE, the Cochrane Library, Scopus, and Web of Science to synthesize evidence published between 1980 and 2022 on HM components and anthropometry through 2 y of age among term-born healthy infants. From 9992 abstracts screened, 57 articles reporting observations from 5979 dyads were included and categorized based on their reporting of HM macronutrients and infant growth. There was substantial heterogeneity in anthropometric outcome measurement, milk collection timelines, and HM sampling strategies; thus, meta-analysis was not possible. In general, digestible carbohydrates were positively associated with infant weight outcomes. Protein was positively associated with infant length, but no associations were reported for infant weight. Finally, HM fat was not consistently associated with any infant growth metrics, though various associations were reported in single studies. Fatty acid intakes were generally positively associated with head circumference, except for docosahexaenoic acid. Our synthesis of the literature was limited by differences in milk collection strategies, heterogeneity in anthropometric outcomes and analytical methodologies, and by insufficient reporting of results. Moving forward, HM researchers should accurately record and account for breastfeeding exclusivity, use consistent sampling protocols that account for the temporal variation in HM macronutrients, and use reliable, sensitive, and accurate techniques for HM macronutrient analysis.
Topics: Child; Female; Humans; Infant; Body Composition; Breast Feeding; Carbohydrates; Fatty Acids; Milk, Human; Nutrients; Proteins
PubMed: 37981047
DOI: 10.1016/j.advnut.2023.100149 -
MBio Oct 2023is an opportunistic human pathogen associated with severe infections and antimicrobial resistance. strains utilize a type VII secretion system to secrete toxins...
is an opportunistic human pathogen associated with severe infections and antimicrobial resistance. strains utilize a type VII secretion system to secrete toxins targeting competitor bacteria, likely facilitating colonization. EsaD is a nuclease toxin secreted by the type VII secretion system in many strains of as well as other related bacterial species. Here, we identify three small proteins of previously unknown function as export factors, required for efficient secretion of EsaD. We show that these proteins bind to the transport domain of EsaD, forming a complex with a striking cane-like conformation.
Topics: Humans; Bacterial Proteins; Type VII Secretion Systems; Staphylococcus aureus; Gene Expression Regulation, Bacterial; Toxins, Biological
PubMed: 37815362
DOI: 10.1128/mbio.02100-23 -
Frontiers in Immunology 2024The end of gestation, ensuing parturition, and the neonatal period represent highly dynamic phases for immunological changes in both mother and offspring. The regulation...
INTRODUCTION
The end of gestation, ensuing parturition, and the neonatal period represent highly dynamic phases for immunological changes in both mother and offspring. The regulation of innate immune cells at the maternal-fetal interface during late term pregnancy, after birth, and during microbial colonization of the neonatal gut and other mucosal surfaces, is crucial for controlling inflammation and maintaining homeostasis. Innate immune cells and mucosal epithelial cells express antileukoproteinase (SLPI), which has anti-inflammatory and anti-protease activity that can regulate cellular activation.
METHODS
Here, we developed and validated new monoclonal antibodies (mAbs) to characterize SLPI for the first time in horses. Peripheral blood and mucosal samples were collected from healthy adults horses and a cohort of mares and their foals directly following parturition to assess this crucial stage.
RESULTS
First, we defined the cell types producing SLPI in peripheral blood by flow cytometry, highlighting the neutrophils and a subset of the CD14+ monocytes as SLPI secreting immune cells. A fluorescent bead-based assay was developed with the new SLPI mAbs and used to establish baseline concentrations for secreted SLPI in serum and secretion samples from mucosal surfaces, including saliva, nasal secretion, colostrum, and milk. This demonstrated constitutive secretion of SLPI in a variety of equine tissues, including high colostrum concentrations. Using immunofluorescence, we identified production of SLPI in mucosal tissue. Finally, longitudinal sampling of clinically healthy mares and foals allowed monitoring of serum SLPI concentrations. In neonates and postpartum mares, SLPI peaked on the day of parturition, with mares returning to the adult normal within a week and foals maintaining significantly higher SLPI secretion until three months of age.
CONCLUSION
This demonstrated a physiological systemic change in SLPI in both mares and their foals, particularly at the time around birth, likely contributing to the regulation of innate immune responses during this critical period.
Topics: Animals; Female; Pregnancy; Animals, Newborn; Antibodies, Monoclonal; Colostrum; Horses; Immunity, Innate; Secretory Leukocyte Peptidase Inhibitor; Up-Regulation
PubMed: 38736885
DOI: 10.3389/fimmu.2024.1395030 -
Nature Communications Jan 2024Centrioles are subcellular organelles found at the cilia base with an evolutionarily conserved structure and a shock absorber-like function. In sperm, centrioles are...
Centrioles are subcellular organelles found at the cilia base with an evolutionarily conserved structure and a shock absorber-like function. In sperm, centrioles are found at the flagellum base and are essential for embryo development in basal animals. Yet, sperm centrioles have evolved diverse forms, sometimes acting like a transmission system, as in cattle, and sometimes becoming dispensable, as in house mice. How the essential sperm centriole evolved to become dispensable in some organisms is unclear. Here, we test the hypothesis that this transition occurred through a cascade of evolutionary changes to the proteins, structure, and function of sperm centrioles and was possibly driven by sperm competition. We found that the final steps in this cascade are associated with a change in the primary structure of the centriolar inner scaffold protein FAM161A in rodents. This information provides the first insight into the molecular mechanisms and adaptive evolution underlying a major evolutionary transition within the internal structure of the mammalian sperm neck.
Topics: Male; Animals; Cattle; Mice; Centrioles; Semen; Spermatozoa; Proteins; Cilia; Mammals
PubMed: 38168044
DOI: 10.1038/s41467-023-44411-8 -
Yi Chuan = Hereditas Dec 2023Mycobacterium infection can affect the host's immune function by secreting extracellular effector proteins. ESX (or type VII) system plays an important role in the... (Review)
Review
Mycobacterium infection can affect the host's immune function by secreting extracellular effector proteins. ESX (or type VII) system plays an important role in the secretion of effector proteins. ESX system is the protein export system in mycobacteria and many actinomycetes. However, how ESX system secretes and underlying mechanism of action remain unclear. In this review, we introduce the components, function, classification of ESX system and the process of substrates transfer to the peripheral space via this system, and discuss the roles of ESX system in antibiotics resistance, persistence, host-phage interaction, new drug targets. We hope to provide insights into the discovery of new drugs and vaccine antigens for tuberculosis.
Topics: Bacterial Proteins; Mycobacterium; Humans; Type VII Secretion Systems; Tuberculosis
PubMed: 38764274
DOI: 10.16288/j.yczz.23-188 -
Diabetologia Jun 2024Beta cells within the pancreatic islet represent a heterogenous population wherein individual sub-groups of cells make distinct contributions to the overall control of...
AIMS/HYPOTHESIS
Beta cells within the pancreatic islet represent a heterogenous population wherein individual sub-groups of cells make distinct contributions to the overall control of insulin secretion. These include a subpopulation of highly connected 'hub' cells, important for the propagation of intercellular Ca waves. Functional subpopulations have also been demonstrated in human beta cells, with an altered subtype distribution apparent in type 2 diabetes. At present, the molecular mechanisms through which beta cell hierarchy is established are poorly understood. Changes at the level of the epigenome provide one such possibility, which we explore here by focusing on the imprinted gene Nnat (encoding neuronatin [NNAT]), which is required for normal insulin synthesis and secretion.
METHODS
Single-cell RNA-seq datasets were examined using Seurat 4.0 and ClusterProfiler running under R. Transgenic mice expressing enhanced GFP under the control of the Nnat enhancer/promoter regions were generated for FACS of beta cells and downstream analysis of CpG methylation by bisulphite sequencing and RNA-seq, respectively. Animals deleted for the de novo methyltransferase DNA methyltransferase 3 alpha (DNMT3A) from the pancreatic progenitor stage were used to explore control of promoter methylation. Proteomics was performed using affinity purification mass spectrometry and Ca dynamics explored by rapid confocal imaging of Cal-520 AM and Cal-590 AM. Insulin secretion was measured using homogeneous time-resolved fluorescence imaging.
RESULTS
Nnat mRNA was differentially expressed in a discrete beta cell population in a developmental stage- and DNA methylation (DNMT3A)-dependent manner. Thus, pseudo-time analysis of embryonic datasets demonstrated the early establishment of Nnat-positive and -negative subpopulations during embryogenesis. NNAT expression is also restricted to a subset of beta cells across the human islet that is maintained throughout adult life. NNAT beta cells also displayed a discrete transcriptome at adult stages, representing a subpopulation specialised for insulin production, and were diminished in db/db mice. 'Hub' cells were less abundant in the NNAT population, consistent with epigenetic control of this functional specialisation.
CONCLUSIONS/INTERPRETATION
These findings demonstrate that differential DNA methylation at Nnat represents a novel means through which beta cell heterogeneity is established during development. We therefore hypothesise that changes in methylation at this locus may contribute to a loss of beta cell hierarchy and connectivity, potentially contributing to defective insulin secretion in some forms of diabetes.
DATA AVAILABILITY
The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD048465.
Topics: Insulin-Secreting Cells; Animals; DNA Methylation; Mice; CpG Islands; Nerve Tissue Proteins; Membrane Proteins; Mice, Transgenic; DNA Methyltransferase 3A; Humans; Insulin; Insulin Secretion
PubMed: 38512414
DOI: 10.1007/s00125-024-06123-6