SRSF1 regulates exosome microRNA enrichment in human cancer cells

hnRNPA2B1 facilitates ovarian carcinoma metastasis by sorting cargoes into small extracellular vesicles driving myofibroblasts activation

BACKGROUND

Ovarian carcinoma (OvCa) metastasis is initiated and boosted by tumor-stroma interactions mediated by small extracellular vesicles (sEVs) containing microRNAs (miRNAs). However, the mechanisms of sorting relevant miRNAs into tumoral sEVs remain elusive.

RESULTS

In this study, among the RNA-binding proteins, hnRNPA2B1 was identified as the most significant factor associated with survival in OvCa patients, and its expression was higher in omental metastases compared to paired ovarian lesions. Based on the CRISPR-Cas9 technique, orthotopic xenograft mice revealed a remarkable metastasis-inhibiting effect of hnRNPA2B1-knockdown, accompanied by diminished myofibroblast signals in the omentum. Meanwhile, after hnRNPA2B1-knockdown, OvCa-sEVs largely lost the ability to promote omental metastasis and myofibroblast activation in vivo and in vitro. High-throughput miRNA sequencing of sEV cargoes revealed that UAG motif-containing miRNAs were significantly affected by hnRNPA2B1, and RNA immunoprecipitation (RIP) verified their direct binding to hnRNPA2B1. In pull down assays, the miRNAs with mutated UAG motif exhibited decreased binding capacity to hnRNPA2B1. The myofibroblasts activated by OvCa-sEVs could promote tumor metastasis, and this effect was notably impacted by manipulating hnRNPA2B1, related sEV-miRNAs, and PI3K/AKT signaling.

CONCLUSIONS

These findings highlight the miRNA sorting to sEVs mediated by hnRNPA2B1 as an important mechanism involved in OvCa metastasis, which may illuminate new therapeutic strategies.

Arginine demethylation of Serine/Arginine-rich splicing factor 1 enhances miRNA enrichment in small extracellular vesicles derived from pancreatic ductal adenocarcinoma cells

Small extracellular vesicles (sEVs) are enriched in certain miRNAs, impacting the progression of pancreatic ductal adenocarcinoma (PDAC). The mechanisms involved in the selective sEV miRNA enrichment remain to be elucidated. We recently reported that Serine/Arginine-rich splicing factor 1 (SRSF1) regulates selective sEV miRNA enrichment in PDAC cells. SRSF1 is an onco-protein that is overexpressed in PDAC, and its function is dictated by posttranslational modifications such as phosphorylation and arginine methylation. The objective of this study was to examine the role of phosphorylation and arginine methylation in SRSF1-mediated sEV miRNA enrichment in PDAC cells. Treatment of PDAC cells with the protein arginine methyltransferase inhibitors AMI-5 and EPZ015666, but not with the phosphorylation inhibitor SRPIN340, selectively enhanced the level of sEV miR-1246, a miRNA known to be highly enriched in PDAC sEVs. Consistently, overexpression of the mutant SRSF1 with the three arginine residues R93, R97, and R109 being replaced with lysinaugmented sEV miR-1246 levels in both wild-type and SRSF1-knockdown PANC-1 cells. Interestingly, the binding of SRSF1 to miR-1246 was significantly reduced in PDAC cells overexpressing the mutant SRSF1, which was further confirmed using purified wild-type and the mutant SRSF1 proteins. We demonstrate that arginine demethylation of SRSF1 reduces SRSF1-miRNA binding in PDAC cells and enhances selective sEV miRNA enrichment, providing novel insight into SRSF1-mediated sEV miRNA enrichment in PDAC cells and opening up new avenues of investigation on the biology and function of extracellular vesicles in PDAC.

Exploring the roles and molecular mechanisms of RNA binding proteins in the sorting of noncoding RNAs into exosomes during tumor progression

BACKGROUND

RNA binding proteins (RBPs) play a role in sorting non-coding RNAs (ncRNAs) into exosomes. These ncRNAs, carried by exosomes, are involved in regulating various aspects of tumor progression, including metastasis, angiogenesis, control of the tumor microenvironment, and drug resistance. Recent studies have emphasized the importance of the RBP-ncRNA-exosome mechanism in tumor regulation.

AIM OF REVIEW

This comprehensive review aims to explore the RBP-ncRNA-exosome mechanism and its influence on tumor development. By understanding this intricate mechanism provides novel insights into tumor regulation and may lead to innovative treatment strategies in the future.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The review discusses the formation of exosomes and the complex relationships among RBPs, ncRNAs, and exosomes. The RBP-ncRNA-exosome mechanism is shown to affect various aspects of tumor biology, including metastasis, multidrug resistance, angiogenesis, the immunosuppressive microenvironment, and tumor progression. Tumor development relies on the transmission of information between cells, with RBPs selectively mediating sorting of ncRNAs into exosomes through various mechanisms, which in turn carry ncRNAs to regulate RBPs. The review also provides an overview of potential therapeutic strategies, such as targeted drug discovery and genetic engineering for modifying therapeutic exosomes, which hold great promise for improving cancer treatment.

Exosome-Mediated Paracrine Signaling Unveils miR-1246 as a Driver of Aggressiveness in Fusion-Negative Rhabdomyosarcoma

Rhabdomyosarcoma is a pediatric cancer associated with aggressiveness and a tendency to develop metastases. Fusion-negative rhabdomyosarcoma (FN-RMS) is the most commonly occurring subtype of RMS, where metastatic disease can hinder treatment success and decrease survival rates. RMS-derived exosomes were previously demonstrated to be enriched with miRNAs, including miR-1246, possibly contributing to disease aggressiveness. We aimed to decipher the functional impact of exosomal miR-1246 on recipient cells and its role in promoting aggressiveness. Treatment of normal fibroblasts with FN-RMS-derived exosomes resulted in a significant uptake of miR-1246 paired with an increase in cell proliferation, migration, and invasion. In turn, delivery of miR-1246-mimic lipoplexes promoted fibroblast proliferation, migration, and invasion in a similar manner. Conversely, when silencing miR-1246 in FN-RMS cells, the resulting derived exosomes demonstrated reversed effects on recipient cells' phenotype. Delivery of exosomal miR-1246 targets GSK3β and promotes β-catenin nuclear accumulation, suggesting a deregulation of the Wnt pathway, known to be important in tumor progression. Finally, a pilot clinical study highlighted, for the first time, the presence of high exosomal miR-1246 levels in RMS patients' sera. Altogether, our results demonstrate that exosomal miR-1246 has the potential to alter the tumor microenvironment of FN-RMS cells, suggesting its potential role in promoting oncogenesis.

Protein Arginine Methylation Patterns in Plasma Small Extracellular Vesicles Are Altered in Patients with Early-Stage Pancreatic Ductal Adenocarcinoma

Small extracellular vesicles (sEVs) contain lipids, proteins and nucleic acids, which often resemble their cells of origin. Therefore, plasma sEVs are considered valuable resources for cancer biomarker development. However, previous efforts have been largely focused on the level of proteins and miRNAs in plasma sEVs, and the post-translational modifications of sEV proteins, such as arginine methylation, have not been explored. Protein arginine methylation, a relatively stable post-translational modification, is a newly described molecular feature of PDAC. The present study examined arginine methylation patterns in plasma sEVs derived from patients with early-stage PDAC (n = 23) and matched controls. By utilizing the arginine methylation-specific antibodies for western blotting, we found that protein arginine methylation patterns in plasma sEVs are altered in patients with early-stage PDAC. Specifically, we observed a reduction in the level of symmetric dimethyl arginine (SDMA) in plasma sEV proteins derived from patients with early- and late-stage PDAC. Importantly, immunoprecipitation followed by proteomics analysis identified a number of arginine-methylated proteins exclusively present in plasma sEVs derived from patients with early-stage PDAC. These results indicate that arginine methylation patterns in plasma sEVs are potential indicators of PDAC, a new concept meriting further investigation.

The Regulation of Exosome Generation and Function in Physiological and Pathological Processes

Exosomes, a type of extracellular vesicle with a diameter of approximately 100 nm that is secreted by all cells, regulate the phenotype and function of recipient cells by carrying molecules such as proteins, nucleic acids, and lipids and are important mediators of intercellular communication. Exosomes are involved in various physiological and pathological processes such as immunomodulation, angiogenesis, tumorigenesis, metastasis, and chemoresistance. Due to their excellent properties, exosomes have shown their potential application in the clinical diagnosis and treatment of disease. The functions of exosomes depend on their biogenesis, uptake, and composition. Thus, a deeper understanding of these processes and regulatory mechanisms can help to find new targets for disease diagnosis and therapy. Therefore, this review summarizes and integrates the recent advances in the regulatory mechanisms of the entire biological process of exosomes, starting from the formation of early-sorting endosomes (ESCs) by plasma membrane invagination to the release of exosomes by fusion of multivesicular bodies (MVBs) with the plasma membrane, as well as the regulatory process of the interactions between exosomes and recipient cells. We also describe and discuss the regulatory mechanisms of exosome production in tumor cells and the potential of exosomes used in cancer diagnosis and therapy.

Extracellular Vesicle MicroRNAs in Heart Failure: Pathophysiological Mediators and Therapeutic Targets

Extracellular vesicles (EVs) are emerging mediators of intracellular and inter-organ communications in cardiovascular diseases (CVDs), especially in the pathogenesis of heart failure through the transference of EV-containing bioactive substances. microRNAs (miRNAs) are contained in EV cargo and are involved in the progression of heart failure. Over the past several years, a growing body of evidence has suggested that the biogenesis of miRNAs and EVs is tightly regulated, and the sorting of miRNAs into EVs is highly selective and tightly controlled. Extracellular miRNAs, particularly circulating EV-miRNAs, have shown promising potential as prognostic and diagnostic biomarkers for heart failure and as therapeutic targets. In this review, we summarize the latest progress concerning the role of EV-miRNAs in HF and their application in a therapeutic strategy development for heart failure.

Structural Modifications and Novel Protein-Binding Sites in Pre-miR-675-Explaining Its Regulatory Mechanism in Carcinogenesis

Pre-miR-675 is a microRNA expressed from the exon 1 of H19 long noncoding RNA, and the atypical expression of pre-miR-675 has been linked with several diseases and disorders including cancer. To execute its function inside the cell, pre-miR-675 is folded into a particular conformation, which aids in its interaction with several other biological molecules. However, the exact folding dynamics of pre-miR-675 and its protein-binding motifs are currently unknown. Moreover, how H19 lncRNA and pre-miR-675 crosstalk and modulate each other's activities is also unclear. The detailed structural analysis of pre-miR-675 in this study determines its earlier unknown conformation and identifies novel protein-binding sites on pre-miR-675, thus making it an excellent therapeutic target against cancer. Co-folding analysis between H19 lncRNA and pre-miR-675 determine structural transformations in pre-miR-675, thus describing the earlier unknown mechanism of interaction between these two molecules. Comprehensively, this study details the conformation of pre-miR-675 and its protein-binding sites and explains its relationship with H19 lncRNA, which can be interpreted to understand the role of pre-miR-675 in the development and progression of tumorigenesis and designing new therapeutics against cancers.

Serine and arginine rich splicing factor 1: a potential target for neuroprotection and other diseases

Alternative splicing is the process of producing variably spliced mRNAs by choosing distinct combinations of splice sites within a messenger RNA precursor. This splicing enables mRNA from a single gene to synthesize different proteins, which have different cellular properties and functions and yet arise from the same single gene. A family of splicing factors, Serine-arginine rich proteins, are needed to initiate the assembly and activation of the spliceosome. Serine and arginine rich splicing factor 1, part of the arginine/serine-rich splicing factor protein family, can either activate or inhibit the splicing of mRNAs, depending on the phosphorylation status of the protein and its interaction partners. Considering that serine and arginine rich splicing factor 1 is either an activator or an inhibitor, this protein has been studied widely to identify its various roles in different diseases. Research has found that serine and arginine rich splicing factor 1 is a key target for neuroprotection, showing its promising potential use in therapeutics for neurodegenerative disorders. Furthermore, serine and arginine rich splicing factor 1 might be used to regulate cancer development and autoimmune diseases. In this review, we highlight how serine and arginine rich splicing factor 1 has been studied concerning neuroprotection. In addition, we draw attention to how serine and arginine rich splicing factor 1 is being studied in cancer and immunological disorders, as well as how serine and arginine rich splicing factor 1 acts outside the central or peripheral nervous system.

miR-18a and miR-106a Signatures in Plasma Small EVs Are Promising Biomarkers for Early Detection of Pancreatic Ductal Adenocarcinoma

Pancreatic cancer is the third leading cause of cancer-related death in the United States. Pancreatic ductal adenocarcinoma (PDAC) is the major form of pancreatic cancer with the worst outcomes. Early detection is key to improving the overall survival rate of PDAC patients. Recent studies have demonstrated that microRNA (miRNA) signatures in plasma small extracellular vesicles (EVs) are potential biomarkers for the early detection of PDAC. However, published results are inconsistent due to the heterogeneity of plasma small EVs and the methods used for small EV isolation. We have recently refined the process of plasma small EV isolation using double filtration and ultracentrifugation. In the present study, we applied this protocol and analyzed plasma small EV miRNA signatures by small RNA sequencing and quantitative RT-PCR in a pilot cohort, consisting of patients with early-stage PDAC, and age- and gender-matched healthy subjects (n = 20). We found, via small RNA sequencing, that there are several miRNAs enriched in plasma small EVs of PDAC patients, and the levels of miR-18a and miR-106a were confirmed by quantitative RT-PCR to be significantly elevated in patients with early-stage PDAC compared with age- and gender-matched healthy subjects. Furthermore, using an immunoaffinity-based plasma small EV isolation approach, we confirmed that the levels of miR-18a and miR-106a in plasma small EVs were significantly higher in PDAC patients versus the healthy subjects. We thus conclude that the levels of miR-18a and miR-106a in plasma small EVs are promising biomarkers for the early detection of PDAC.

Exosomal miRNAs in the Tumor Microenvironment of Multiple Myeloma

Multiple myeloma (MM) is a malignancy of plasma cells in the bone marrow and is characterized by the clonal proliferation of B-cells producing defective monoclonal immunoglobulins. Despite the latest developments in treatment, drug resistance remains one of the major challenges in the therapy of MM. The crosstalk between MM cells and other components within the bone marrow microenvironment (BME) is the major determinant of disease phenotypes. Exosomes have emerged as the critical drivers of this crosstalk by allowing the delivery of informational cargo comprising multiple components from miniature peptides to nucleic acids. Such material transfers have now been shown to perpetuate drug-resistance development and disease progression in MM. MicroRNAs(miRNAs) specifically play a crucial role in this communication considering their small size that allows them to be readily packed within the exosomes and widespread potency that impacts the developmental trajectory of the disease inside the tumor microenvironment (TME). In this review, we aim to provide an overview of the current understanding of the role of exosomal miRNAs in the epigenetic modifications inside the TME and its pathogenic influence on the developmental phenotypes and prognosis of MM.

Small extracellular vesicle-associated miR-6068 promotes aggressive phenotypes of prostate cancer through miR-6068/HIC2/SIRT1 axis

Early diagnosis and treatment of patients with aggressive prostate cancer (PCa) remains a clinically unmet need. We aimed to determine the levels of small extracellular vesicle (sEV)-associated microRNAs (miRs); miR-4737, miR-6068, and miR-6076 in a large panel of PCa cells and delineate the biological significance of miR-6068 in promoting PCa cells. sEVs were isolated from the conditioned medium of PCa cells, followed by RNA extraction and quantitative Real-Time PCR analysis. Functional assays were performed, and the protein expression of hypermethylated in cancer 2 (HIC2), as a potential miR-6068 target gene, was evaluated in PCa tissues by immunohistochemistry. sEV-associated miR-6068, miR-4737, and miR-6076 levels displayed large and significant differences compared to normal cells. miR-6068 was explicitly upregulated in sEV of PC-3 and CWR-R1ca cells (P<0.010). Suppression of miR-6068 in CWR-R1ca cells decreased cell proliferation, colony formation, and cell migration. In contrast, upregulation of miR-6068 in RC77T/E cells decreased HIC2 levels and increased cell aggressive phenotypes. The overexpression of HIC2 in PCa tissues was primarily observed in the cytoplasm compared to benign prostatic hyperplasia (BPH) and normal tissues (P<0.0001). This study confirms the differential packaging of miR-4737, miR-6068, and miR-6076 in sEVs of PCa cells. MiR-6068 promotes PCa cells to acquire aggressive phenotypes by inhibiting the HIC2/Sirtuin 1 (SIRT1) axis.

Multi-omics analysis revealed the role of extracellular vesicles in hepatobiliary & pancreatic tumor

Liquid biopsy is rapidly growing into a hot research field due to its unique advantages of minimal invasiveness, and extracellular vesicle (EVs) are also expected to become an important pillar in the diagnostic technology system as a newly discovered active substance carrier. More and more research has highlighted the important contribution of EVs in the progress of tumor. Molecular changes during disease progression could be detected in EVs. However, the diagnostic applications of EVs are not generally understood. Combined with the characteristics of hepatobiliary and pancreatic tumor, we summarized the recent developments in various omics analysis of EVs. Furtherly, we explored the role of EVs in the early diagnosis of hepatobiliary and pancreatic tumors by multi-omics analysis.

Cancer-Associated Fibroblast-Derived Exosomal miRNA-320a Promotes Macrophage M2 Polarization In Vitro by Regulating PTEN/PI3Kγ Signaling in Pancreatic Cancer

Our previous study has indicated that cancer-associated fibroblasts (CAFs) play a crucial role in regulating gemcitabine resistance through transferring exosomal miRNA-106b to cancer cells. Tumor-associated macrophages (TAMs) are recently verified to facilitate gemcitabine resistance. However, the effect of CAFs in regulating TAMs function in pancreatic cancer (PCa) remains unclear. Here, primary CAFs were extracted from tumor tissues of PCa patients, and CAFs-derived exosomes (CAFs-Exo) were acquired and authenticated by transmission electron microscopy, qNano, and western blot analysis. The role of exosomal miRNA-320a in facilitating macrophage M2 polarization was investigated in vitro. We found that CAFs-derived conditioned medium (CM) possessed a higher potential to promote macrophage M2 polarization compared with normal fibroblasts (NFs) or PCa cell-derived CM. Furthermore, CAFs-Exo treatment polarized macrophage to M2 phenotype. miRNA-320a levels were remarkably increased in CAFs-Exo versus NFs-Exo. More important, miRNA-320a could be transferred from CAFs to macrophages through exosomes, and miRNA-320a overexpression in macrophages facilitated its M2 polarization. Functionally, miRNA-320a-overexpressed macrophages facilitated PCa cell proliferation and invasion. CAFs pretreated with miRNA-320a inhibitor reduced miRNA-320a expression in CAFs-Exo and led to decreased M2 macrophage polarization. Finally, we verified that miRNA-320a polarized macrophage to M2 phenotype by regulating PTEN/PI3Kγ signaling. Taken together, the current data demonstrated that CAFs-derived exosomal miRNA-320a facilitated macrophage M2 polarization to accelerate malignant behavior of PCa cells.

Current Knowledge on Exosome Biogenesis, Cargo-Sorting Mechanism and Therapeutic Implications

Extracellular vesicles (EVs) are nanoscale membrane vesicles released by donor cells that can be taken up by recipient cells. The study of EVs has the potential to identify unknown cellular and molecular mechanisms in intercellular communication and disease. Exosomes, with an average diameter of ≈100 nanometers, are a subset of EVs. Different molecular families have been shown to be involved in the formation of exosomes and subsequent secretion of exosomes, which largely leads to the complexity of the form, structure and function of exosomes. In addition, because of their low immunogenicity and ability to transfer a variety of bioactive components to recipient cells, exosomes are regarded as effective drug delivery systems. This review summarizes the known mechanisms of exosomes biogenesis, cargo loading, exosomes release and bioengineering, which is of great importance for further exploration into the clinical applications of EVs.

Pancreatic Ductal Cell-Derived Extracellular Vesicles Are Effective Drug Carriers to Enhance Paclitaxel's Efficacy in Pancreatic Cancer Cells through Clathrin-Mediated Endocytosis

Chemo-resistance challenges the clinical management of pancreatic ductal adenocarcinoma (PDAC). A limited admittance of chemotherapeutics to PDAC tissues is a key obstacle in chemotherapy of the malignancy. An enhanced uptake of drugs into PDAC cells is required for a more effective treatment. Extracellular vesicles (EVs), especially small EVs (sEVs), have emerged as drug carriers for delivering chemotherapeutics due to their low immunogenicity and propensity for homing toward tumor cells. The present study evaluated sEVs derived from six different human cell lines as carriers for paclitaxel (PTX). The encapsulation of the chemotherapeutics was achieved using incubation, sonication and electroporation. The cytotoxicity of the EV drugs was evaluated by MTS assay. While sonication led to a higher efficiency of drug loading than incubation and electroporation, PTX loaded through incubation with HPNE-derived sEVs (HI-PTX) was the most efficacious in killing PDAC cells. Furthermore, HI-PTX was taken up by PDAC cells more efficiently than other EV drugs, implying that the efficacy of HI-PTX is associated with its efficient uptake. This was supported by the observation that the cytotoxicity and uptake of HI-PTX is mediated via the clathrin-dependent endocytosis. Our results indicate that the hTERT-HPNE cell-derived EVs are effective drug carriers to enhance paclitaxel's efficacy in PDAC cells.

Exosomes: the key of sophisticated cell-cell communication and targeted metastasis in pancreatic cancer

Pancreatic cancer is one of the most common malignancies. Unfortunately, the lack of effective methods of treatment and diagnosis has led to poor prognosis coupled with a very high mortality rate. So far, the pathogenesis and progression mechanisms of pancreatic cancer have been poorly characterized. Exosomes are small vesicles secreted by most cells, contain lipids, proteins, and nucleic acids, and are involved in diverse functions such as intercellular communications, biological processes, and cell signaling. In pancreatic cancer, exosomes are enriched with multiple signaling molecules that mediate intercellular communication with control of immune suppression, mutual promotion between pancreas stellate cells and pancreatic cancer cells, and reprogramming of normal cells. In addition, exosomes can regulate the pancreatic cancer microenvironment and promote the growth and survival of pancreatic cancer. Exosomes can also build pre-metastatic micro-ecological niches and facilitate the targeting of pancreatic cancer. The ability of exosomes to load cargo and target allows them to be of great clinical value as a biomarker mediator for targeted drugs in pancreatic cancer. Video Abstract.

Prognostic prediction and gene regulation network of EIF2S2 in hepatocellular carcinoma based on data mining

BACKGROUND

Hepatocellular carcinoma (HCC) is a malignant tumor with a high fatality rate, predicting poor prognosis and therapeutic effect. Screening potential prognostic genes in HCC could be a creative way to advance clinical treatment. Eukaryotic translation initiation factor 2 subunit beta (EIF2S2) has reportedly been linked to several tumors, including liver cancer, but the prognostic predictions remain unknown. Therefore, we aimed to clarify the prognostic role and interaction network of EIF2S2 in HCC using bioinformatics data.

METHODS

We screened EIF2S2 using the Oncomine, Ualcan, and TCGA databases. R software was used to analyze the mRNA level and clinicopathological characteristics of hepatocellular carcinoma. Evaluation of the correlations between EIF2S2 and patients' survival was made using the Kaplan-Meier curves and Cox proportional hazards regression model. Then, the influence of EIF2S2 gene mutations on the prognosis of patients was explored by cBioPortal. The protein-protein interaction network of 50 similar genes related to EIF2S2 was implemented by GEPIA2 and Metascape. The LinkedOmics database allowed us to carry out Gene Set Enrichment Analysis. Finally, we constructed the EIF2S2 kinase, miRNA, and transcription factor target networks using GeneMANIA.

RESULTS

EIF2S2 mRNA was overexpressed in HCC and was closely associated with clinicopathological features, including gender, age, race, tumor grade, and stage. There was no correlation between EIF2S2 genetic mutations and prognostic survival. Combining Cox proportional hazards regression model analyses, high-expressed EIF2S2 predicted poor prognosis in HCC patients. Additionally, we screened the top three EIF2S2-related genes (PFDN4, HM13, and SNRPD1), the 50 similar genes, and then constructed a 50-similar-gene protein-protein interaction network identified by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways using Metascape. EIF2S2 target networks in HCC were identified in kinase, miRNA, and transcription factor networks, including the mitogen-activated protein kinase 1 (MAPK1), miRNAs (Mir-144), and transcription factors (GGAANCGGAANY_UNKNOWN) using GeneMANIA.

CONCLUSIONS

EIF2S2 plays a crucial role in the gene-regulating network of HCC and may be a potential prognostic marker or therapeutic target for HCC patients.

Distinct small non-coding RNA landscape in the axons and released extracellular vesicles of developing primary cortical neurons and the axoplasm of adult nerves

Neurons have highlighted the needs for decentralized gene expression and specific RNA function in somato-dendritic and axonal compartments, as well as in intercellular communication via extracellular vesicles (EVs). Despite advances in miRNA biology, the identity and regulatory capacity of other small non-coding RNAs (sncRNAs) in neuronal models and local subdomains has been largely unexplored.We identified a highly complex and differentially localized content of sncRNAs in axons and EVs during early neuronal development of cortical primary neurons and in adult axons in vivo. This content goes far beyond miRNAs and includes most known sncRNAs and precisely processed fragments from tRNAs, sno/snRNAs, Y RNAs and vtRNAs. Although miRNAs are the major sncRNA biotype in whole-cell samples, their relative abundance is significantly decreased in axons and neuronal EVs, where specific tRNA fragments (tRFs and tRHs/tiRNAs) mainly derived from tRNAs Gly-GCC, Val-CAC and Val-AAC predominate. Notably, although 5'-tRHs compose the great majority of tRNA-derived fragments observed in vitro, a shift to 3'-tRNAs is observed in mature axons in vivo.The existence of these complex sncRNA populations that are specific to distinct neuronal subdomains and selectively incorporated into EVs, equip neurons with key molecular tools for spatiotemporal functional control and cell-to-cell communication.

Nuclear mRNA Quality Control and Cytoplasmic NMD Are Linked by the Guard Proteins Gbp2 and Hrb1

Pre-mRNA splicing is critical for cells, as defects in this process can lead to altered open reading frames and defective proteins, potentially causing neurodegenerative diseases and cancer. Introns are removed in the nucleus and splicing is documented by the addition of exon-junction-complexes (EJCs) at exon-exon boundaries. This “memory” of splicing events is important for the ribosome, which translates the RNAs in the cytoplasm. In case a stop codon was detected before an EJC, translation is blocked and the RNA is eliminated by the nonsense-mediated decay (NMD). In the model organism Saccharomyces cerevisiae, two guard proteins, Gbp2 and Hrb1, have been identified as nuclear quality control factors for splicing. In their absence, intron-containing mRNAs leak into the cytoplasm. Their presence retains transcripts until the process is completed and they release the mRNAs by recruitment of the export factor Mex67. On transcripts that experience splicing problems, these guard proteins recruit the nuclear RNA degradation machinery. Interestingly, they continue their quality control function on exported transcripts. They support NMD by inhibiting translation and recruiting the cytoplasmic degradation factors. In this way, they link the nuclear and cytoplasmic quality control systems. These discoveries are also intriguing for humans, as homologues of these guard proteins are present also in multicellular organisms. Here, we provide an overview of the quality control mechanisms of pre-mRNA splicing, and present Gbp2 and Hrb1, as well as their human counterparts, as important players in these pathways.

Communication is key: Extracellular vesicles as mediators of infection and defence during host-microbe interactions in animals and plants

Extracellular vesicles (EVs) are now understood to be ubiquitous mediators of cellular communication. In this review, we suggest that EVs have evolved into a highly regulated system of communication with complex functions including export of wastes, toxins and nutrients, targeted delivery of immune effectors and vectors of RNA silencing. Eukaryotic EVs come in different shapes and sizes and have been classified according to their biogenesis and size distributions. Small EVs (or exosomes) are released through fusion of endosome-derived multivesicular bodies with the plasma membrane. Medium EVs (or microvesicles) bud off the plasma membrane as a form of exocytosis. Finally, large EVs (or apoptotic bodies) are produced as a result of the apoptotic process. This review considers EV secretion and uptake in four eukaryotic kingdoms, three of which produce cell walls. The impacts cell walls have on EVs in plants and fungi are discussed, as are roles of fungal EVs in virulence. Contributions of plant EVs to development and innate immunity are presented. Compelling cases are sporophytic self-incompatibility and cellular invasion by haustorium-forming filamentous pathogens. The involvement of EVs in all of these eukaryotic processes is reconciled considering their evolutionary history.

Heterogeneous Nuclear Ribonucleoprotein A1 Loads Batched Tumor-Promoting MicroRNAs Into Small Extracellular Vesicles With the Assist of Caveolin-1 in A549 Cells

MicroRNAs in small extracellular vesicle (sEV-miRNAs) have been widely investigated as crucial regulated molecules secreted by tumor cells to communicate with surroundings. It is of great significance to explore the loading mechanism of sEV-miRNAs by tumor cells. Here, we comprehensively illustrated a reasoned loading pathway of batched tumor-promoting sEV-miRNAs in non-small cell lung cancer (NSCLC) cell line A549 with the application of a multi-omics method. The protein heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) was strictly selected as a powerful sEV-miRNA loading protein from miRNA-binding proteome and further verified through small RNA sequencing after hnRNPA1 silence. In terms of the mechanism, SUMOylated hnRNPA1 in sEVs was verified to control sEV-miRNA loading. Subsequently, as a scaffolding component of caveolae, caveolin-1 (CAV1) was detailedly demonstrated to assist the loading of SUMOylated hnRNPA1 and its binding miRNAs into sEVs. Inhibition of CAV1 significantly prevented SUMOylated hnRNPA1 from encapsulating into sEVs, resulting in less enrichment of sEV-miRNAs it loaded. Finally, we confirmed that hnRNPA1-loaded sEV-miRNAs could facilitate tumor proliferation and migration based on database analysis and cytological experiments. Our findings reveal a loading mechanism of batched tumor-promoting sEV-miRNAs, which may contribute to the selection of therapeutic targets for lung cancer.

Insights Into Exosomal Non-Coding RNAs Sorting Mechanism and Clinical Application

Exosomes are natural nanoscale bilayer phospholipid vesicles that can be secreted by almost all types of cells and are detected in almost all types of body fluids. Exosomes are effective mediators of cell–cell signaling communication because of their ability to carry and transfer a variety of bioactive molecules, including non-coding RNAs. Non-coding RNAs have also been found to exert strong effects on a variety of biological processes, including tumorigenesis. Many researchers have established that exosomes encapsulate bioactive non-coding RNAs that alter the biological phenotype of specific target cells in an autocrine or a paracrine manner. However, the mechanism by which the producer cells package non-coding RNAs into exosomes is not well understood. This review focuses on the current research on exosomal non-coding RNAs, including the biogenesis of exosomes, the possible mechanism of sorting non-coding RNAs, their biological functions, and their potential for clinical application in the future.

Adipocytes-Derived Extracellular Vesicle-miR-26b Promotes Apoptosis of Cumulus Cells and Induces Polycystic Ovary Syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a refractory reproductive disease and also a kind of endocrine and metabolic disease. Adipocyte cells can produce a mass of extracellular vesicles and orchestrate the status of other types cells. The objective of this study was to determine the effects of adipocyte-derived extracellular vesicles-miR-26b on cumulus cells (CCs) and development of PCOS.

METHODS

The crosstalk mediated by extracellular vesicle-miR-26b between adipocytes and CCs was determined in CC cells co-cultured with mature adipocytes or incubated with extracellular vesicle isolated from mature adipocytes. CCK-8 assay and flow cytometry were conducted in CCs treated with or without extracellular vesicles; microRNA (miRNA) sequencing was conducted for clarifying the key molecular. Hormone levels and ovary ovulation ability were conducted with animal experiment.

RESULTS

The results revealed that miR-26b was upregulated in extracellular vesicles derived from mature adipocytes. Adipocyte-derived extracellular vesicles inhibited viability and promoted apoptosis in CCs via targeting JAG1. Furthermore, extracellular vesicles derived from mature adipocyte disrupted the ovary ovulation and impaired the hormone levels.

CONCLUSIONS

These results identify a novel signaling pathway that adipocytes-derived extracellular vesicles-miR-26b promotes cell apoptosis in CCs and disrupted the ovary ovulation in the development of PCOS. The study indicates that adipose tissue-derived extracellular vesicles-miR-26b may play a key role in the PCOS and also provides insight into developing new therapeutic strategies for PCOS.