Unraveling the Intricacies of Cold-Inducible RNA-Binding Protein: A Comprehensive Review.

Cold-inducible RNA-binding protein (CIRP) is a versatile RNA-binding protein, pivotal in modulating cellular responses to diverse stress stimuli including cold shock, ultraviolet radiation, hypoxia, and infections, with a principal emphasis on cold stress. The temperature range of 32-34°C is most suitable for CIRP expression. The human CIRP is an 18-21kDa polypeptide containing 172 amino acids coded by gene located on chromosome 19p13.3. CIRP has an RNA-recognition motif (RRM) and an arginine-rich motif (RGG), both of which have roles in coordinating numerous cellular activities. CIRP itself also undergoes conformational changes in response to diverse environmental stress. Transcription factors such as hypoxia-inducible factor 1 alpha (HIF-1α) and nuclear factor-kappa B (NF-κB) have been implicated in coordinating CIRP transcription in response to specific stimuli. The potential of CIRP to relocate from the nucleus to the cytoplasm upon exposure to different stimuli enhances its varied functional roles across different cellular compartments. The different functions include decreasing nutritional demand, apoptosis suppression, modulation of translation, and preservation of cytoskeletal integrity at lower temperatures. This review explores the diverse functions and regulatory mechanisms of CIRP, shedding light on its involvement in various cellular processes and its implications in human health and disease.

HNRNP I promotes IRAK1 degradation to reduce podocyte apoptosis and inflammatory response alleviating renal injury in diabetic nephropathy.

Podocytes maintain renal filtration integrity when the glomerular filtration barrier (GFB) is integrated. Impairment or attrition of podocytes, leading to compromised GFB permeability, constitutes the primary etiology of proteinuria and is a hallmark pathological feature of diabetic nephropathy (DN). This study centers on Heterogeneous Nuclear Ribonucleoprotein I (HNRNP I), an RNA-binding protein, delineating its role in facilitating DN-induced renal damage by modulating podocyte health. Comparative analyses in renal biopsy specimens from DN patients and high-glucose-challenged podocyte models in vitro revealed a marked downregulation of HNRNP I expression relative to normal renal tissues and podocytes. In vitro assays demonstrated that high-glucose conditions precipitated a significant reduction in podocyte viability and an escalation in markers indicative of apoptosis. Conversely, HNRNP I overexpression was found to restore podocyte viability and attenuate apoptotic indices. IRAK1, a gene encoding a protein integral to inflammatory signaling, was shown to interact with HNRNP I, which promotes IRAK1 degradation. This interaction culminates in suppressing the PI3K/AKT/mTOR signaling pathway, thereby diminishing podocyte apoptosis and mitigating renal damage in DN. This investigation unveils the mechanistic role of HNRNP I in DN for the first time, potentially informing novel therapeutic strategies for DN renal impairment.

m6A-dependent mature miR-151-5p accelerates the malignant process of HNSCC by targeting LYPD3.

miRNA has emerged as a crucial regulator in various of pathological and physiological processes, yet its precise mechanism of action the detailed mechanism of their action in Head and neck squamous cell carcinoma (HNSCC) remains incompletely understood. This study sheds light on the role of mi-151-5p, revealing its significantly elevated expression in tumor cells, which notably enhances the invasion and migration of HNSCC cells. This effect is achieved through directly targeting LY6/PLAUR Domain Containing 3 (LYPD3) by miR-151-5p, involving complementary binding to the 3'-untranslated regions (3'-UTR) in the mRNA of LYPD3. Consequently, this interaction accelerates the metastasis of HNSCC. Notably, clinical observations indicate a correlation between high expression of miR-151-5p and low levels of LYPD3 in clinical settings are correlated with poor prognosis of HNSCC patients. Furthermore, our investigation demonstrates that glycosylation of LYPD3 modulates its subcellular localization and reinforces its role in suppressing HNSCC metastasis. Additionally, we uncover a potential regulatory mechanism involving the facilitation of miR-151-5p maturation and accumulation through N6-methyladenosine (m6A) modification. This process is orchestrated by methyltransferase-like 3 (METTL3) and mediated by a newly identified reader, heterogeneous nuclear ribonucleoprotein U (hnRNP U). These findings collectively underscore the significance of the METTL3/miR-151-5p/LYPD3 axis serves as a prominent driver in the malignant progression of HNSCC.

The RNA-binding selectivity of the RGG/RG motifs of hnRNP U is abolished by elements within the C-terminal intrinsically disordered region.

The abundant nuclear protein hnRNP U interacts with a broad array of RNAs along with DNA and protein to regulate nuclear chromatin architecture. The RNA-binding activity is achieved via a disordered ∼100 residue C-terminal RNA-binding domain (RBD) containing two distinct RGG/RG motifs. Although the RNA-binding capabilities of RGG/RG motifs have been widely reported, less is known about hnRNP U's RNA-binding selectivity. Furthermore, while it is well established that hnRNP U binds numerous nuclear RNAs, it remains unknown whether it selectively recognizes sequence or structural motifs in target RNAs. To address this question, we performed equilibrium binding assays using fluorescence anisotropy (FA) and electrophoretic mobility shift assays (EMSAs) to quantitatively assess the ability of human hnRNP U RBD to interact with segments of cellular RNAs identified from eCLIP data. These RNAs often, but not exclusively, contain poly-uridine or 5'-AGGGAG sequence motifs. Detailed binding analysis of several target RNAs reveal that the hnRNP U RBD binds RNA in a promiscuous manner with high affinity for a broad range of structured RNAs, but with little preference for any distinct sequence motif. In contrast, the isolated RGG/RG of hnRNP U motif exhibits a strong preference for G-quadruplexes, similar to that observed for other RGG motif bearing peptides. These data reveal that the hnRNP U RBD attenuates the RNA binding selectivity of its core RGG motifs to achieve an extensive RNA interactome. We propose that a critical role of RGG/RG motifs in RNA biology is to alter binding affinity or selectivity of adjacent RNA-binding domains.

Interferon-Regulated Expression of Cellular Splicing Factors Modulates Multiple Levels of HIV-1 Gene Expression and Replication.

Type I interferons (IFN-Is) are pivotal in innate immunity against human immunodeficiency virus I (HIV-1) by eliciting the expression of IFN-stimulated genes (ISGs), which encompass potent host restriction factors. While ISGs restrict the viral replication within the host cell by targeting various stages of the viral life cycle, the lesser-known IFN-repressed genes (IRepGs), including RNA-binding proteins (RBPs), affect the viral replication by altering the expression of the host dependency factors that are essential for efficient HIV-1 gene expression. Both the host restriction and dependency factors determine the viral replication efficiency; however, the understanding of the IRepGs implicated in HIV-1 infection remains greatly limited at present. This review provides a comprehensive overview of the current understanding regarding the impact of the RNA-binding protein families, specifically the two families of splicing-associated proteins SRSF and hnRNP, on HIV-1 gene expression and viral replication. Since the recent findings show specifically that SRSF1 and hnRNP A0 are regulated by IFN-I in various cell lines and primary cells, including intestinal lamina propria mononuclear cells (LPMCs) and peripheral blood mononuclear cells (PBMCs), we particularly discuss their role in the context of the innate immunity affecting HIV-1 replication.

Targeting Ser78 phosphorylation of Hsp27 achieves potent antiviral effects against enterovirus A71 infection.

A positive-sense (+) single-stranded RNA (ssRNA) virus (e.g. enterovirus A71, EV-A71) depends on viral polypeptide translation for initiation of virus replication after entry. We reported that EV-A71 hijacks Hsp27 to induce hnRNP A1 cytosol redistribution to initiate viral protein translation, but the underlying mechanism is still elusive. Here, we show that phosphorylation-deficient Hsp27-3A (Hsp27S15/78/82A) and Hsp27S78A fail to translocate into the nucleus and induce hnRNP A1 cytosol redistribution, while Hsp27S15A and Hsp27S82A display similar effects to the wild type Hsp27. Furthermore, we demonstrate that the viral 2A protease (2Apro) activity is a key factor in regulating Hsp27/hnRNP A1 relocalization. Hsp27S78A dramatically decreases the IRES activity and viral replication, which are partially reduced by Hsp27S82A. However, Hsp27S15A displays the same activity as the wild-type Hsp27. Peptide S78 potently suppresses EV-A71 protein translation and reproduction through blockage of EV-A71-induced Hsp27 phosphorylation and Hsp27/hnRNP A1 relocalization. A point mutation (S78A) on S78 impairs its inhibitory functions on Hsp27/hnRNP A1 relocalization and viral replication. Taken together, we demonstrate the importance of Ser78 phosphorylation of Hsp27 regulated by virus infection in nuclear translocation, hnRNP A1 cytosol relocation, and viral replication, suggesting a new path (such as peptide S78) for target-based antiviral strategy.

Heterogeneous nuclear ribonucleoprotein A3 binds to the internal ribosomal entry site of enterovirus A71 and affects virus replication in neural cells.

Enterovirus A71 (EV-A71) belongs to the genus Enterovirus of the Picornaviridae family and often causes outbreaks in Asia. EV-A71 infection usually causes hand, foot, and mouth disease and can even affect the central nervous system, causing neurological complications or death. The 5'-untranslated region (5'-UTR) of EV-A71 contains an internal ribosome entry site (IRES) that is responsible for the translation of viral proteins. IRES-transacting factors can interact with the EV-A71 5'-UTR to regulate IRES activity. Heterogeneous nuclear ribonucleoprotein (hnRNP) A3 is a member of the hnRNP A/B protein family of RNA-binding proteins and is involved in RNA transport and modification. We found that hnRNP A3 knockdown promoted the replication of EV-A71 in neural calls. Conversely, increasing the expression of hnRNP A3 within cells inhibits the growth of EV-A71. HnRNP A3 can bind to the EV-A71 5'-UTR, and knockdown of hnRNP A3 enhances the luciferase activity of the EV-A71 5'-UTR IRES. The localization of hnRNP A3 shifts from the nucleus to the cytoplasm of infected cells during viral infection. Additionally, EV-A71 infection can increase the protein expression of hnRNP A3, and the protein level is correlated with efficient viral growth. Based on these findings, we concluded that hnRNP A3 plays a negative regulatory role in EV-A71 replication within neural cells.

Conserved role of hnRNPL in alternative splicing of epigenetic modifiers enables B cell activation.

The multifunctional RNA-binding protein hnRNPL is implicated in antibody class switching but its broader function in B cells is unknown. Here, we show that hnRNPL is essential for B cell activation, germinal center formation, and antibody responses. Upon activation, hnRNPL-deficient B cells show proliferation defects and increased apoptosis. Comparative analysis of RNA-seq data from activated B cells and another eight hnRNPL-depleted cell types reveals common effects on MYC and E2F transcriptional programs required for proliferation. Notably, while individual gene expression changes are cell type specific, several alternative splicing events affecting histone modifiers like KDM6A and SIRT1, are conserved across cell types. Moreover, hnRNPL-deficient B cells show global changes in H3K27me3 and H3K9ac. Epigenetic dysregulation after hnRNPL loss could underlie differential gene expression and upregulation of lncRNAs, and explain common and cell type-specific phenotypes, such as dysfunctional mitochondria and ROS overproduction in mouse B cells. Thus, hnRNPL is essential for the resting-to-activated B cell transition by regulating transcriptional programs and metabolism, at least in part through the alternative splicing of several histone modifiers.

HnRNPA2B1 ISGylation Regulates m6A-Tagged mRNA Selective Export via ALYREF/NXF1 Complex to Foster Breast Cancer Development.

Regulating nuclear export precisely is essential for maintaining mRNA homeostasis and impacts tumor progression. However, the mechanisms governing nuclear mRNA export remain poorly elucidated. Herein, it is revealed that the enhanced hypoxic long no-ncoding RNA (lncRNA prostate cancer associated transcript 6 (PCAT6) in breast cancer (BC) promotes the nuclear export of m6A-modified mRNAs, bolstering breast cancer stem cells (BCSCs) stemness and doxorubicin resistance. Clinically, hypoxic PCAT6 correlates with malignant BC features and poor prognosis. Mechanically, PCAT6 functions as a scaffold between interferon-stimulated gene 15 (ISG15) and heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1), leading to ISGylation of hnRNPA2B1, thus protecting hnRNPA2B1 from ubiquitination-mediated proteasomal degradation. Interestingly, as an m6A reader, hnRNPA2B1 selectively mediates m6A-tagged mRNAs nuclear export via the Aly/REF export factor (ALYREF)/ nuclear RNA export factor 1 (NXF1) complex, which promotes stemness-related genes expression. HnRNPA2B1 knockdown or mRNA export inhibition can result in the retention of nuclear m6A-tagged mRNA associated with stemness maintenance, which suppresses BCSCs self-renewal and effectively improves the efficacy of doxorubicin therapy. These findings demonstrate the pivotal role of m6A-modified mRNA nuclear export in BC progression, highlighting that the inhibition of m6A-tagged mRNA and its nuclear export is a potential therapeutic strategy for the amelioration of cancer chemotherapy.

Autophagy mediated degradation of MITA/TBK1/IRF3 by a hnRNP family member attenuates interferon production in fish.

HnRNP A/B belongs to the heterogeneous nuclear ribonucleoprotein (hnRNP) family and plays an important role in regulating viral protein translation and genome replication. Here, we found that overexpression of hnRNP A/B promoted spring viremia of carp virus (SVCV) and cyprinid herpesvirus 3 (CyHV3) replication. Further, hnRNP A/B was shown to act as a negative regulator of type I interferon (IFN) response. Mechanistically, hnRNP A/B interacted with MITA, TBK1 and IRF3 to initiate their degradation. In addition, hnRNP A/B bound to the kinase domain of TBK1, the C terminal domain of MITA and IAD domain of IRF3, and the RRM1 domain of hnRNP A/B bound to TBK1, RRM2 domain bound to IRF3 and MITA. Our study provides novel insights into the functions of hnRNP A/B in regulating host antiviral response.

hnRNP R regulates mitochondrial movement and membrane potential in axons of motoneurons.

Axonal mitochondria defects are early events in the pathogenesis of motoneuron disorders such as spinal muscular atrophy and amyotrophic lateral sclerosis. The RNA-binding protein hnRNP R interacts with different motoneuron disease-related proteins such as SMN and TDP-43 and has important roles in axons of motoneurons, including axonal mRNA transport. However, whether hnRNP R also modulates axonal mitochondria is currently unknown. Here, we show that axonal mitochondria exhibit altered function and motility in hnRNP R-deficient motoneurons. Motoneurons lacking hnRNP R show decreased anterograde and increased retrograde transport of mitochondria in axons. Furthermore, hnRNP R-deficiency leads to mitochondrial hyperpolarization, caused by decreased complex I and reversed complex V activity within the respiratory chain. Taken together, our data indicate a role for hnRNP R in regulating transport and maintaining functionality of axonal mitochondria in motoneurons.

Heterogeneous nuclear ribonucleoprotein F deficiency in mouse podocyte promotes podocytopathy mediated by methyltransferase-like 14 nuclear translocation resulting in Sirtuin 1 gene inhibition.

Heterogeneous nuclear ribonucleoprotein F (HnRNP F) is a key regulator for nucleic acid metabolism; however, whether HnRNP F expression is important in maintaining podocyte integrity is unclear. Nephroseq analysis from a registry of human kidney biopsies was performed. Age- and sex-matched podocyte-specific HnRNP F knockout (HnRNP FPOD KO) mice and control (HnRNP Ffl/fl) were studied. Podocytopathy was induced in male mice (more susceptible) either by adriamycin (ADR)- or low-dose streptozotocin treatment for 2 or 8 weeks. The mouse podocyte cell line (mPODs) was used in vitro. Nephroseq data in three human cohorts were varied greatly. Both sexes of HnRNP FPOD KO mice were fertile and appeared grossly normal. However, male 20-week-old HnRNP FPOD KO than HnRNP Ffl/fl mice had increased urinary albumin/creatinine ratio, and lower expression of podocyte markers. ADR- or diabetic- HnRNP FPOD KO (vs. HnRNP Ffl/fl) mice had more severe podocytopathy. Moreover, methyltransferase-like 14 (Mettl14) gene expression was increased in podocytes from HnRNP FPOD KO mice, further enhanced in ADR- or diabetic-treated HnRNP FPOD KO mice. Consequently, this elevated Mettl14 expression led to sirtuin1 (Sirt1) inhibition, associated with podocyte loss. In mPODs, knock-down of HnRNP F promoted Mettl14 nuclear translocation, which was associated with podocyte dysmorphology and Sirt1 inhibition-mediated podocyte loss. This process was more severe in ADR- or high glucose- treated mPODs. Conclusion: HnRNP F deficiency in podocytes promotes podocytopathy through activation of Mettl14 expression and its nuclear translocation to inhibit Sirt1 expression, underscoring the protective role of HnRNP F against podocyte injury.

Alternative splicing patterns of hnrnp genes in gill tissues of rainbow trout (Oncorhynchus mykiss) during salinity changes.

Alternative splicing (AS) plays an important role in various physiological processes in eukaryotes, such as the stress response. However, patterns of AS events remain largely unexplored during salinity acclimation in fishes. In this study, we conducted AS analysis using RNA-seq datasets to explore splicing patterns in the gill tissues of rainbow trout exposed to altered salinity environments, ranging from 0 ‰ (T0) to 30 ‰ (T30). The results revealed 1441, 351, 483, 1051 and 1049 differentially alternatively spliced (DAS) events in 5 pairwise comparisons, including T6 vs. T0, T12 vs. T0, T18 vs. T0, T24 vs. T0, and T30 vs. T0, respectively. These DAS events were derived from 1290, 328, 444, 963 and 948 genes. Enrichment analysis indicated that these DAS genes were related to RNA splicing and processing. Among these, 14 DAS genes were identified as members of the large heterogeneous nuclear RNP (hnRNP) gene family. Alternative 3' splice site (A3SS), exon skipping (SE) and intron retention (RI) events resulted in the fragmentation or even loss of the functional RNA recognition motif (RRM) domains in hnrnpa0, hnrnp1a, hnrnp1b and hnrnpc genes. The incomplete RRM domains would hinder the interactions between hnRNP genes and pre-mRNAs. It would in turn influence the splicing patterns and mRNA stability of downstream target genes in response to salinity changes. The study provides insights into salinity acclimation in gill tissues of rainbow trout and serves as a significant reference on the osmoregulation mechanisms at post-transcription regulation levels in fish.

Switchable tetraplex elements in the heterogeneous nuclear ribonucleoprotein K promoter: micro-environment dictated structural transitions of G/C rich elements.

We have elucidated the hnRNP K promoter as a hotspot for tetraplex-based molecular switches receptive to micro-environmental stimuli. We have characterised the structural features of four tetraplex-forming loci and identified them as binding sites of transcription factors. These segments form either G-quadruplex or i-motif structures, the structural dynamicity of which has been studied in depth via several biophysical techniques. The tetraplexes display high dynamicity and are influenced by both pH and KCl concentrations in vitro. The loci complementary to these sequences form additional non-canonical secondary structures. In the cellular context, the most eminent observation of this study is the binding of hnRNP K to the i-motif forming sequences in its own promoter. We are the first to report a probable transcriptional autoregulatory function of hnRNP K in coordination with higher-order DNA structures. Herein, we also report the positive interaction of the endogenous tetraplexes with Sp1, a well-known transcriptional regulator. Treatment with tetraplex-specific small molecule ligands further uncovered G-quadruplexes' functioning as repressors and i-motifs as activators in this context. Together, our findings strongly indicate the critical regulatory role of the identified tetraplex elements in the hnRNP K promoter.Communicated by Ramaswamy H. Sarma.

Interference of gut-brain-gonad axis originating from triclocarban exposure to parent zebrafish induces offspring embryonic development abnormality by up-regulation of maternal circSGOL1.

Triclocarban (TCC) is a widely used antibacterial ingredient possessing acute toxicity effects; however, its chronic toxicity and underlying molecular mechanisms remain uncertain. Herein, we demonstrated that chronic TCC exposure affects the growth and development of adult zebrafish through inducing an intestinal flora disorder in the gut. The imbalance of intestinal flora caused functional barriers within the intestinal-brain-gonadal axis. This resulted in a series of anomalous nerve and motor behaviors, and reproductive toxicity as reflected in pathological damage to parental gonads and F1-larval developmental malformations. Abnormal development of F1 larvae was attributed to apoptosis induced by the up-regulation of circSGOL1. This up-regulation affected the activity and localization of the hnRNP A1 protein, which then promoted overexpression of pro-apoptotic related genes that ultimately lead to apoptosis during early embryonic development. Overall, these novel findings systematically elucidated the TCC toxicity mechanism in parent-offspring dyads, and provide important theoretical guidance for early risk warning and control of chronic TCC toxicity.

Cryo-EM structures of functional and pathological amyloid ribonucleoprotein assemblies.

Amyloids are implicated in neurodegenerative and systemic diseases, yet they serve important functional roles in numerous organisms. Heterogeneous nuclear ribonucleoproteins (hnRNPs) represent a large family of RNA-binding proteins (RBPs) that control central events of RNA biogenesis in normal and diseased cellular conditions. Many of these proteins contain prion-like sequences of low complexity, which not only assemble into functional fibrils in response to cellular cues but can also lead to disease when missense mutations arise in their sequences. Recent advances in cryo-electron microscopy (cryo-EM) have provided unprecedented high-resolution structural insights into diverse amyloid assemblies formed by hnRNPs and structurally related RBPs, including TAR DNA-binding protein 43 (TDP-43), Fused in Sarcoma (FUS), Orb2, hnRNPA1, hnRNPA2, and hnRNPDL-2. This review provides a comprehensive overview of these structures and explores their functional and pathological implications.

A high-throughput screen identifies RNA binding proteins that affect fertility in Caenorhabditis elegans and reveals a functional relationship between ADR-2 and SQD-1.

RNA binding proteins play essential roles in coordinating germline gene expression and development in all organisms. Characterization of gross fertility defects, such as sterility, has identified RNA binding proteins that are critical regulators of germline gene expression; however, broader screens for RNA binding proteins involved in specific reproductive processes are lacking. Here, a reverse genetic screen was performed to identify RNA binding proteins that impact yolk and embryo production in Caenorhabditis elegans hermaphrodites. This screen makes use of animals expressing a vitellogenin (yolk protein) fusion with green fluorescent protein, in a genetic background that corrects for a previously identified fertility defect in this strain. From this screen, we identified 23 RNA binding proteins that regulate embryo production in Caenorhabditis elegans. This screen lays groundwork for future interrogations into the molecular roles of these proteins in yolk production and embryogenesis. Additionally, the screen uncovered a genetic interaction between ADR-2, a member of the Adenosine DeAminase Acting on RNA (ADAR) family, and SQD-1, a member of the heterogenous nuclear ribonucleoprotein (hnRNP) family. Transcriptome-wide assessment in animals depleted of sqd-1 revealed over 8000 misregulated transcripts, suggesting SQD-1 is a major regulator of gene expression. Consistent with this, microscopy and reproductive assays reveal that sqd-1 is essential for oogenesis. In the absence of adr-2, the effects of loss of sqd-1 on gene expression are attenuated, as well as the defects in oogenesis. Together, these data indicate that both ADR-2 and SQD-1 are important regulators of germline gene expression and oogenesis.

The microRNA-195-5p/hnRNP A1 axis contributes to the progression of hepatocellular carcinoma by regulating the migration of cancer cells.

Dysregulation of gene expression is critical for the progression of cancer. The augmented expression of hnRNP A1 in patients with hepatocellular carcinoma (HCC) has been related to its oncogenic functions. However, the underlying mechanisms responsible for upregulation of hnRNP A1 have not been fully elucidated. In the present study, we identified microRNA-195-5p (miR-195-5p), a miRNA downregulated in HCC, as a novel regulator governing hnRNP A1 expression. Notably, our investigations showed an inverse correlation between hnRNP A1 level, which was increased in HCC, and miR-195-5p level, which was decreased. Our findings demonstrated that hnRNP A1 significantly enhanced the migration and invasion of PLC/PRF/5 cells through its association with mRNAs regulating metastasis. MiR-195-5p also interfered with the hnRNP A1-mediated cell migration by targeting hnRNP A1. Our results underscore the significance of the miR-195-5p/hnRNP A1 axis in regulating the migratory potential of cancer cells and its role in promoting HCC by orchestrating cell migration processes.

The Roles of hnRNP Family in the Brain and Brain-Related Disorders.

Heterogeneous nuclear ribonucleoproteins (hnRNPs) belong to a complex family of RNA-binding proteins that are essential to control alternative splicing, mRNA trafficking, synaptic plasticity, stress granule formation, cell cycle regulation, and axonal transport. Over the past decade, hnRNPs have been associated with different brain disorders such as Alzheimer's disease, multiple sclerosis, and schizophrenia. Given their essential role in maintaining cell function and integrity, it is not surprising that dysregulated hnRNP levels lead to neurological implications. This review aims to explore the primary functions of hnRNPs in neurons, oligodendrocytes, microglia, and astrocytes, and their roles in brain disorders. We also discuss proteomics and other technologies and their potential for studying and evaluating hnRNPs in brain disorders, including the discovery of new therapeutic targets and possible pharmacological interventions.

ß-Arrestin2 promotes docetaxel resistance of castration-resistant prostate cancer via promoting hnRNP A1-mediated PKM2 alternative splicing.

PURPOSE: To investigate the influence of ß-arrestin2 on the docetaxel resistance in castration-resistant prostate cancer (CRPC) and elucidate the underlying molecular mechanisms. METHODS: PC3 and DU145 cells with stable ß-arrestin2 overexpression and C4-2 cells with stable ß-arrestin2 knockdown, were constructed via using lentivirus and puromycin selection. MTT and colony formation assays were carried out to investigate the effect of ß-arrestin2 expression on the docetaxel resistance of CRPC cells. Glycolysis analysis was used to assess the glycolytic capacity modulated by ß-arrestin2. GO enrichment analysis, gene set enrichment analysis and Spearman correlation test were carried out to explore the potential biological function and mechanism via using public data from GEO and TCGA. The expressions of PKM2, Phospho-PKM2, Phospho-ERK1/2 and hnRNP A1 were detected by western blot. Functional blocking experiments were carried out to confirm the roles of PKM2 and hnRNP A1 in the regulation of ß-arrestin2's biological functions via silencing PKM2 or hnRNP A1 expression in cells with stable ß-arrestin2 overexpression. Finally, nude mice xenograft models were established to confirm the experimental results of cell experiments. RESULTS: ß-Arrestin2 significantly decreased the sensitivity of CRPC cells to docetaxel stimulation, through enhancing the phosphorylation and expression of PKM2. Additionally, ß-arrestin2 increased PKM2 phosphorylation via the ERK1/2 signaling pathway and induced PKM2 expression in a post-transcriptional manner through an hnRNP A1-dependent PKM alternative splicing mechanism, rather than by inhibiting its ubiquitination degradation. CONCLUSION: Our findings indicate that the ß-arrestin2/hnRNP A1/PKM2 pathway could be a promising target for treating docetaxel-resistant CRPC.