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Blood Advances Jun 2023Selinexor (KPT-330) is a small molecule inhibitor of XPO1, which mediates the transport of tumor suppressor proteins, oncogene messenger RNAs, and other proteins...
Selinexor (KPT-330) is a small molecule inhibitor of XPO1, which mediates the transport of tumor suppressor proteins, oncogene messenger RNAs, and other proteins involved in governing cell growthfrom the cell nucleus to the cytoplasm. It is overexpressed in many cancer types. Because eukaryotic translation initiator factor 4E (eIF4E) plays a critical role in protein translation in cancer cells in multiple myeloma (MM), we evaluated the effectiveness of combined inhibition of protein translation and nuclear export in MM. Selinexor, an inhibitor of nuclear protein export, dose-dependently decreased eIF4E, IKZF1, and c-MYC protein levels. Using a doxycycline-inducible-pLKO-Tet-On vector, knockdown of eIF4E significantly enhanced the antiproliferative effects of selinexor, sensitized resistant MM cells to selinexor, and increased apoptosis in MM cells. Immunofluorescent analysis of MM cells showed that the combined treatment increased the localization of residual eIF4E to the nucleus compared with selinexor-only treatment. The overexpression of eIF4E at least partially rescued the effects of selinexor in MM cells by reducing G1 cell cycle arrest and increasing the selinexor-IC50 10-fold. Moreover, the combination of selinexor with pharmacologic inhibitors of protein translation showed synergistic anti-MM effects. These results suggest a synergistic anti-MM effect of selinexor combined with eIF4E inhibitors in vitro. Our work provides a better understanding of the potential mechanism of resistance to selinexor and a rationale for combining selinexor with eIF4E inhibitors for the treatment of MM.
Topics: Humans; Active Transport, Cell Nucleus; Karyopherins; Eukaryotic Initiation Factor-4E; Apoptosis; Multiple Myeloma; Protein Biosynthesis
PubMed: 36827679
DOI: 10.1182/bloodadvances.2021006638 -
Cell Death & Disease Sep 2023Development of colorectal cancer (CRC) involves activation of Kirsten rat sarcoma viral oncogene homolog (KRAS) signaling. However, the post-transcriptional regulation...
Development of colorectal cancer (CRC) involves activation of Kirsten rat sarcoma viral oncogene homolog (KRAS) signaling. However, the post-transcriptional regulation of KRAS has yet to be fully characterized. Here, we found that the colorectal neoplasia differentially expressed (CRNDE)/heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1) axis was notably elevated in CRC and was strongly associated with poor prognosis of patients, while also significantly promoting CRC cell proliferation and metastasis both in vitro and in vivo. Furthermore, CRNDE maintained the stability of hnRNPA2B1 protein by inhibiting E3 ubiquitin ligase TRIM21 mediated K63 ubiquitination-dependent protein degradation. CRNDE/hnRNPA2B1 axis facilitated the nuclear export and translation of KRAS mRNA, which specifically activated the MAPK signaling pathway, eventually accelerating the malignant progression of CRC. Our findings provided insight into the regulatory network for stable hnRNPA2B1 protein expression, and the molecular mechanisms by which the CRNDE/hnRNPA2B1 axis mediated KRAS nucleocytoplasmic transport and translation, deeply underscoring the bright future of hnRNPA2B1 as a promising biomarker and therapeutic target for CRC. By hindering hnRNPA2B1 from binding to the E3 ubiquitin ligase TRIM21, whose mediated ubiquitin-dependent degradation was thereby inhibited, CRNDE protected the stability of hnRNPA2B1's high protein expression in CRC. Supported by the high level of the oncogenic molecule CRNDE, hnRNPA2B1 bound to KRAS mRNA and promoted KRAS mRNA nucleus export to enter the ribosomal translation program, subsequently activating the MAPK signaling pathway and ultimately accelerating the malignant progression of CRC.
Topics: Humans; Active Transport, Cell Nucleus; Proto-Oncogene Proteins p21(ras); Cell Proliferation; MAP Kinase Signaling System; Colorectal Neoplasms
PubMed: 37716979
DOI: 10.1038/s41419-023-06137-9 -
ELife May 2024Advanced cryo-EM approaches reveal surprising insights into the molecular structure that allows nascent proteins to be inserted into the membrane of the endoplasmic...
Advanced cryo-EM approaches reveal surprising insights into the molecular structure that allows nascent proteins to be inserted into the membrane of the endoplasmic reticulum.
Topics: Endoplasmic Reticulum; Cryoelectron Microscopy; Protein Transport; Membrane Proteins
PubMed: 38787756
DOI: 10.7554/eLife.98548 -
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 -
Nature Communications Aug 2023Extracellular vesicles (EVs) are gaining ground as next-generation drug delivery modalities. Genetic fusion of the protein of interest to a scaffold protein with high...
Extracellular vesicles (EVs) are gaining ground as next-generation drug delivery modalities. Genetic fusion of the protein of interest to a scaffold protein with high EV-sorting ability represents a robust cargo loading strategy. To address the paucity of such scaffold proteins, we leverage a simple and reliable assay that can distinguish intravesicular cargo proteins from surface- as well as non-vesicular proteins and compare the EV-sorting potential of 244 candidate proteins. We identify 24 proteins with conserved EV-sorting abilities across five types of producer cells. TSPAN2 and TSPAN3 emerge as lead candidates and outperform the well-studied CD63 scaffold. Importantly, these engineered EVs show promise as delivery vehicles in cell cultures and mice as demonstrated by efficient transfer of luminal cargo proteins as well as surface display of different functional entities. The discovery of these scaffolds provides a platform for EV-based engineering.
Topics: Mice; Animals; Extracellular Vesicles; Proteins; Drug Delivery Systems; Protein Transport; Cell Communication
PubMed: 37550290
DOI: 10.1038/s41467-023-40453-0 -
Traffic (Copenhagen, Denmark) Sep 2023Endosomal cargo recycling lies at the heart of subcellular trafficking processes under the management of several Ras-related GTP-binding proteins (Rabs) which are... (Review)
Review
Endosomal cargo recycling lies at the heart of subcellular trafficking processes under the management of several Ras-related GTP-binding proteins (Rabs) which are coordinated by their upstream regulators and require their downstream effectors to display their functions. In this regard, several Rabs have been well-reviewed except Rab22a. Rab22a is a crucial regulator of vesicle trafficking, early endosome and recycling endosome formation. Notably, recent studies demonstrated the immunological roles of Rab22a, which are closely associated with cancers, infection and autoimmune disorders. This review provides an overview of the regulators and effectors of Rab22a. Also, we highlight the current knowledge of the role of Rab22a in endosomal cargo recycling, including the biogenesis of recycling tubules with the help of a complex with Rab22a at its core, and how different internalized cargo chooses different recycling routes thanks to the cooperation of Rab22a, its effectors and its regulators. Of note, contradictions and speculation related to endosomal cargo recycling that Rab22a brings impacts on are also discussed. Finally, this review endeavors to briefly introduce the various events impacted by Rab22a, particularly focusing on the commandeered Rab22a-associated endosomal maturation and endosomal cargo recycling, in addition to the extensively investigated oncogenic role of Rab22a.
Topics: Protein Transport; rab GTP-Binding Proteins; Endosomes; Cell Communication
PubMed: 37340959
DOI: 10.1111/tra.12907 -
Cells Dec 2023Cellular nucleocytoplasmic trafficking is mediated by the importin family of nuclear transport proteins. The well-characterized importin alpha (IMPA) and importin beta... (Review)
Review
Cellular nucleocytoplasmic trafficking is mediated by the importin family of nuclear transport proteins. The well-characterized importin alpha (IMPA) and importin beta (IMPB) nuclear import pathway plays a crucial role in the innate immune response to viral infection by mediating the nuclear import of transcription factors such as IRF3, NFκB, and STAT1. The nuclear transport of these transcription factors ultimately leads to the upregulation of a wide range of antiviral genes, including IFN and IFN-stimulated genes (ISGs). To replicate efficiently in cells, viruses have developed mechanisms to block these signaling pathways. One strategy to evade host innate immune responses involves blocking the nuclear import of host antiviral transcription factors. By binding IMPA proteins, these viral proteins prevent the nuclear transport of key transcription factors and suppress the induction of antiviral gene expression. In this review, we describe examples of proteins encoded by viruses from several different families that utilize such a competitive inhibition strategy to suppress the induction of antiviral gene expression.
Topics: Active Transport, Cell Nucleus; alpha Karyopherins; Immunity, Innate; Antiviral Agents; Organophosphorus Compounds
PubMed: 38201275
DOI: 10.3390/cells13010071 -
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 -
Trends in Biochemical Sciences Feb 2024Ribosomes interact with a variety of different protein biogenesis factors that guide newly synthesized proteins to their native 3D shapes and cellular localization.... (Review)
Review
Ribosomes interact with a variety of different protein biogenesis factors that guide newly synthesized proteins to their native 3D shapes and cellular localization. Depending on the type of translated substrate, a distinct set of cotranslational factors must interact with the ribosome in a timely and coordinated manner to ensure proper protein biogenesis. While cytonuclear proteins require cotranslational maturation and folding factors, secretory proteins must be maintained in an unfolded state and processed cotranslationally by transport and membrane translocation factors. Here we explore the specific cotranslational processing steps for cytonuclear, secretory, and membrane proteins in eukaryotes and then discuss how the nascent polypeptide-associated complex (NAC) cotranslationally sorts these proteins into the correct protein biogenesis pathway.
Topics: Ribosomes; Protein Biosynthesis; Protein Transport; Membrane Proteins; Saccharomyces cerevisiae
PubMed: 37919225
DOI: 10.1016/j.tibs.2023.10.003 -
Nature Communications Oct 2023Cytosolic metalloenzymes acquire metals from buffered intracellular pools. How exported metalloenzymes are appropriately metalated is less clear. We provide evidence...
Cytosolic metalloenzymes acquire metals from buffered intracellular pools. How exported metalloenzymes are appropriately metalated is less clear. We provide evidence that TerC family proteins function in metalation of enzymes during export through the general secretion (Sec-dependent) pathway. Bacillus subtilis strains lacking MeeF(YceF) and MeeY(YkoY) have a reduced capacity for protein export and a greatly reduced level of manganese (Mn) in the secreted proteome. MeeF and MeeY copurify with proteins of the general secretory pathway, and in their absence the FtsH membrane protease is essential for viability. MeeF and MeeY are also required for efficient function of the Mn-dependent lipoteichoic acid synthase (LtaS), a membrane-localized enzyme with an extracytoplasmic active site. Thus, MeeF and MeeY, representative of the widely conserved TerC family of membrane transporters, function in the co-translocational metalation of Mn-dependent membrane and extracellular enzymes.
Topics: Bacterial Proteins; Protein Transport; Bacillus subtilis; Secretory Pathway; Metalloproteins
PubMed: 37794032
DOI: 10.1038/s41467-023-41896-1