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Toxins Apr 2024Pathogenic bacteria produce diverse protein toxins to disturb the host's defenses. This includes the opening of epithelial barriers to establish bacterial growth in... (Review)
Review
Pathogenic bacteria produce diverse protein toxins to disturb the host's defenses. This includes the opening of epithelial barriers to establish bacterial growth in deeper tissues of the host and to modulate immune cell functions. To achieve this, many toxins share the ability to enter mammalian cells, where they catalyze the modification of cellular proteins. The enzymatic activity is diverse and ranges from ribosyl- or glycosyl-transferase activity, the deamidation of proteins, and adenylate-cyclase activity to proteolytic cleavage. Protein toxins are highly active enzymes often with tight specificity for an intracellular protein or a protein family coupled with the intrinsic capability of entering mammalian cells. A broad understanding of their molecular mechanisms established bacterial toxins as powerful tools for cell biology. Both the enzymatic part and the pore-forming/protein transport capacity are currently used as tools engineered to study signaling pathways or to transport cargo like labeled compounds, nucleic acids, peptides, or proteins directly into the cytosol. Using several representative examples, this review is intended to provide a short overview of the state of the art in the use of bacterial toxins or parts thereof as tools.
Topics: Bacterial Toxins; Humans; Animals; Protein Transport; Bacteria
PubMed: 38787054
DOI: 10.3390/toxins16050202 -
ELife Sep 2023The ATPase p97 (also known as VCP, Cdc48) has crucial functions in a variety of important cellular processes such as protein quality control, organellar homeostasis, and...
The ATPase p97 (also known as VCP, Cdc48) has crucial functions in a variety of important cellular processes such as protein quality control, organellar homeostasis, and DNA damage repair, and its de-regulation is linked to neuromuscular diseases and cancer. p97 is tightly controlled by numerous regulatory cofactors, but the full range and function of the p97-cofactor network is unknown. Here, we identify the hitherto uncharacterized FAM104 proteins as a conserved family of p97 interactors. The two human family members CP nuclear ofactor amily member 1 and 2 (VCF1/2) bind p97 directly via a novel, alpha-helical motif and associate with p97-UFD1-NPL4 and p97-UBXN2B complexes in cells. VCF1/2 localize to the nucleus and promote the nuclear import of p97. Loss of VCF1/2 results in reduced nuclear p97 levels, slow growth, and hypersensitivity to chemical inhibition of p97 in the absence and presence of DNA damage, suggesting that FAM104 proteins are critical regulators of nuclear p97 functions.
Topics: Humans; Valosin Containing Protein; Nuclear Proteins; Active Transport, Cell Nucleus
PubMed: 37713320
DOI: 10.7554/eLife.92409 -
The Journal of Biological Chemistry Mar 2024The emerging roles of O-GlcNAcylation, a distinctive post-translational modification, are increasingly recognized for their involvement in the intricate processes of... (Review)
Review
The emerging roles of O-GlcNAcylation, a distinctive post-translational modification, are increasingly recognized for their involvement in the intricate processes of protein trafficking and secretion. This modification exerts its influence on both conventional and unconventional secretory pathways. Under healthy and stress conditions, such as during diseases, it orchestrates the transport of proteins within cells, ensuring timely delivery to their intended destinations. O-GlcNAcylation occurs on key factors, like coat protein complexes (COPI and COPII), clathrin, SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors), and GRASP55 (Golgi reassembly stacking protein of 55 kDa) that control vesicle budding and fusion in anterograde and retrograde trafficking and unconventional secretion. The understanding of O-GlcNAcylation offers valuable insights into its critical functions in cellular physiology and the progression of diseases, including neurodegeneration, cancer, and metabolic disorders. In this review, we summarize and discuss the latest findings elucidating the involvement of O-GlcNAc in protein trafficking and its significance in various human disorders.
Topics: Humans; Acetylglucosamine; Clathrin; Protein Processing, Post-Translational; Protein Transport; SNARE Proteins; Animals; Acetylation; Glucose
PubMed: 38272225
DOI: 10.1016/j.jbc.2024.105677 -
Trends in Cell Biology Sep 2023Regulated cell death occurs in many forms, including apoptosis, pyroptosis, necroptosis, and NETosis. Most obviously, the purpose of these pathways is to kill the cell.... (Review)
Review
Regulated cell death occurs in many forms, including apoptosis, pyroptosis, necroptosis, and NETosis. Most obviously, the purpose of these pathways is to kill the cell. However, many cells need to complete a set of effector programs before they die, which we define as a cellular 'bucket list'. These effector programs are specific to the cell type, and mode and circumstances of death. For example, intestinal epithelial cells need to complete the process of extrusion before they die. Cells use regulatory mechanisms to temporarily prolong their life, including endosomal sorting complex required for transport (ESCRT)- and acid sphingomyelinase (ASM)-driven membrane repair. These allow cells to complete their bucket lists before they die.
Topics: Humans; Cell Death; Apoptosis; Pyroptosis; Biological Transport; Protein Transport
PubMed: 36958996
DOI: 10.1016/j.tcb.2023.02.008 -
Biochemical Society Transactions Dec 2023Mitochondria are vital to the functions of eukaryotic cells. Most mitochondrial proteins are transported into the organelle following their synthesis by cytoplasmic... (Review)
Review
Mitochondria are vital to the functions of eukaryotic cells. Most mitochondrial proteins are transported into the organelle following their synthesis by cytoplasmic ribosomes. However, precise protein targeting is complex because the two diverse lipid membranes encase mitochondria. Efficient protein translocation across membranes and accurate sorting to specific sub-compartments require the cooperation of multiple factors. Any failure in mitochondrial protein import can disrupt organelle fitness. Proteins intended for mitochondria make up a significant portion of all proteins produced in the cytosol. Therefore, import defects causing their mislocalization can significantly stress cellular protein homeostasis. Recognition of this phenomenon has increased interest in molecular mechanisms that respond to import-related stress and restore proteostasis, which is the focus of this review. Significantly, disruptions in protein homeostasis link strongly to the pathology of several degenerative disorders highly relevant in ageing societies. A comprehensive understanding of protein import quality control will allow harnessing this machinery in therapeutic approaches.
Topics: Mitochondria; Protein Transport; Mitochondrial Proteins; Biological Transport; Cytosol
PubMed: 37987513
DOI: 10.1042/BST20230377 -
Developmental Cell Jun 2024Endoplasmic reticulum exit sites (ERESs) are tubular outgrowths of endoplasmic reticulum that serve as the earliest station for protein sorting and export into the...
Endoplasmic reticulum exit sites (ERESs) are tubular outgrowths of endoplasmic reticulum that serve as the earliest station for protein sorting and export into the secretory pathway. How these structures respond to different cellular conditions remains unclear. Here, we report that ERESs undergo lysosome-dependent microautophagy when Ca is released by lysosomes in response to nutrient stressors such as mTOR inhibition or amino acid starvation in mammalian cells. Targeting and uptake of ERESs into lysosomes were observed by super-resolution live-cell imaging and focus ion beam scanning electron microscopy (FIB-SEM). The mechanism was ESCRT dependent and required ubiquitinated SEC31, ALG2, and ALIX, with a knockout of ALG2 or function-blocking mutations of ALIX preventing engulfment of ERESs by lysosomes. In vitro, reconstitution of the pathway was possible using lysosomal lipid-mimicking giant unilamellar vesicles and purified recombinant components. Together, these findings demonstrate a pathway of lysosome-dependent ERES microautophagy mediated by COPII, ALG2, and ESCRTS induced by nutrient stress.
Topics: Lysosomes; Endoplasmic Reticulum; Humans; Endosomal Sorting Complexes Required for Transport; Calcium-Binding Proteins; COP-Coated Vesicles; Microautophagy; Vesicular Transport Proteins; Cell Cycle Proteins; Protein Transport; HeLa Cells; Apoptosis Regulatory Proteins; Autophagy; TOR Serine-Threonine Kinases; Calcium
PubMed: 38593803
DOI: 10.1016/j.devcel.2024.03.027 -
Biochimica Et Biophysica Acta. Gene... Jun 2024RNA polymerase II (Pol II) is the multi-protein complex responsible for transcribing all protein-coding messenger RNA (mRNA). Most research on gene regulation is focused... (Review)
Review
RNA polymerase II (Pol II) is the multi-protein complex responsible for transcribing all protein-coding messenger RNA (mRNA). Most research on gene regulation is focused on the mechanisms controlling which genes are transcribed when, or on the mechanics of transcription. How global Pol II activity is determined receives comparatively less attention. Here, we follow the life of a Pol II molecule from 'assembly of the complex' to nuclear import, enzymatic activity, and degradation. We focus on how Pol II spends its time in the nucleus, and on the two-way relationship between Pol II abundance and activity in the context of homeostasis and global transcriptional changes.
Topics: RNA Polymerase II; Transcription, Genetic; Humans; Gene Expression Regulation; Cell Nucleus; RNA, Messenger; Active Transport, Cell Nucleus; Animals
PubMed: 38552781
DOI: 10.1016/j.bbagrm.2024.195024 -
The Journal of Cell Biology Jul 2024How nucleocytoplasmic transport (NCT) rates change due to cellular physiology-mediated fluctuations in GTP availability remains unclear. In this issue, Scott et al....
How nucleocytoplasmic transport (NCT) rates change due to cellular physiology-mediated fluctuations in GTP availability remains unclear. In this issue, Scott et al. (https://doi.org/10.1083/jcb.202308152) demonstrate that cell migration, spreading, and nucleocytoskeletal coupling impact GTP levels, thereby regulating NCT, RNA export, and protein synthesis.
Topics: Humans; Active Transport, Cell Nucleus; Cell Movement; Cell Nucleus; Energy Metabolism; Guanosine Triphosphate; Protein Biosynthesis
PubMed: 38847483
DOI: 10.1083/jcb.202405121 -
The Journal of Clinical Investigation Nov 2023Dual-specificity phosphatase 8 (DUSP8) is a MAPK phosphatase that dephosphorylates and inactivates the kinase JNK. DUSP8 is highly expressed in T cells; however, the in...
Dual-specificity phosphatase 8 (DUSP8) is a MAPK phosphatase that dephosphorylates and inactivates the kinase JNK. DUSP8 is highly expressed in T cells; however, the in vivo role of DUSP8 in T cells remains unclear. Using T cell-specific Dusp8 conditional KO (T-Dusp8 cKO) mice, mass spectrometry analysis, ChIP-Seq, and immune analysis, we found that DUSP8 interacted with Pur-α, stimulated interleukin-9 (IL-9) gene expression, and promoted Th9 differentiation. Mechanistically, DUSP8 dephosphorylated the transcriptional repressor Pur-α upon TGF-β signaling, leading to the nuclear export of Pur-α and subsequent IL-9 transcriptional activation. Furthermore, Il-9 mRNA levels were induced in Pur-α-deficient T cells. In addition, T-Dusp8-cKO mice displayed reduction of IL-9 and Th9-mediated immune responses in the allergic asthma model. Reduction of Il-9 mRNA levels in T cells and allergic responses of T-Dusp8-cKO mice was reversed by Pur-α knockout. Remarkably, DUSP8 protein levels and the DUSP8-Pur-α interaction were indeed increased in the cytoplasm of T cells from people with asthma and patients with atopic dermatitis. Collectively, DUSP8 induces TGF-β-stimulated IL-9 transcription and Th9-induced allergic responses by inhibiting the nuclear translocation of the transcriptional repressor Pur-α. DUSP8 may be a T-cell biomarker and therapeutic target for asthma and atopic dermatitis.
Topics: Animals; Humans; Mice; Active Transport, Cell Nucleus; Asthma; Dermatitis, Atopic; Dual-Specificity Phosphatases; Hypersensitivity; Inflammation; Interleukin-9; RNA, Messenger; Transcription Factors; Transforming Growth Factor beta
PubMed: 37909329
DOI: 10.1172/JCI166269 -
Bioorganic Chemistry Feb 2024Protein trafficking is a fundamental process with profound implications for both intracellular and intercellular functions. Proximity labeling (PL) technology has... (Review)
Review
Protein trafficking is a fundamental process with profound implications for both intracellular and intercellular functions. Proximity labeling (PL) technology has emerged as a powerful tool for capturing precise snapshots of subcellular proteomes by directing promiscuous enzymes to specific cellular locations. These enzymes generate reactive species that tag endogenous proteins, enabling their identification through mass spectrometry-based proteomics. In this comprehensive review, we delve into recent advancements in PL-based methodologies, placing particular emphasis on the label-and-fractionation approach and TransitID, for mapping proteome trafficking. These methodologies not only facilitate the exploration of dynamic intracellular protein trafficking between organelles but also illuminate the intricate web of intercellular and inter-organ protein communications.
Topics: Proteomics; Organelles; Mass Spectrometry; Proteome; Protein Transport
PubMed: 38134520
DOI: 10.1016/j.bioorg.2023.107041