Polypyrimidine Tract-binding Protein 1 Expression Research Articles

EXPRESS: PTBP1 is a potential indicator of disease progression in acute myeloid leukaemia.

This study aimed to verify a novel potential indicator of disease progression in acute myeloid leukaemia (AML) patients. Bone marrow samples were collected from 27 AML patients and 27 controls without haematological malignancies. Polypyrimidine tract binding protein 1 (PTBP1) expression in bone marrow samples was measured, and the association of PTBP1 with the French-American-British (FAB) classification, cytogenetics, risk stratification, and complete remission (CR) rate was analysed. The correlation between PTBP1 and Ki-67/p53 expression in AML patients was ultimately evaluated. The results showed that PTBP1 mRNA and protein levels were greater in AML patients than in controls. PTBP1 expression was able to distinguish between AML patients and controls (area under the curve, 0.8601; 95% CI, 0.7632-0.9570). Furthermore, PTBP1 expression was associated with an increased frequency of internal tandem duplication mutations within FMS-like tyrosine kinase-3 (FLT3-ITD) and a complex karyotype (CK), while PTBP1 expression was not correlated with FAB classification, monosomal karyotype, isolated biallelic CCAAT/enhancer-binding protein α (CEBPA) mutation, or nucleophosmin 1 (NPM1) mutation in patients with AML. Moreover, PTBP1 expression was associated with a poorer prognosis according to risk stratification and a lower CR rate in AML patients. In addition, PTBP1 expression was positively correlated with the expression of the proliferation marker Ki-67 and negatively correlated with the expression of the apoptosis marker p53 in AML patients. Overall, PTBP1 is a viable biomarker that contributes to the risk prediction and the determination of potential drug targets for AML.

N6-Methyladenosine Demethylase ALKBH5 Promotes Pyroptosis by Modulating PTBP1 mRNA Stability in LPS-Induced Myocardial Dysfunction.

This study aims to investigate the mechanism by which alkB homolog 5 (ALKBH5) regulates polypyrimidine tract-binding protein 1 (PTBP1) to mediate cardiomyocyte pyroptosis in sepsis-induced myocardial injury. Lipopolysaccharide (LPS)-exposed H9C2 cell and rat models were established to mimic septic myocardial injury both in vitro and in vivo. The mRNA and protein levels of ALKBH5 and PTBP1 in the LPS-induced cell and septic rat models were detected. CCK-8 and flow cytometry were applied to detect cell viability and pyroptosis. H&E staining was used to observe myocardial tissue damage in rats, and immunohistochemistry to analyze the expression of pyroptosis and inflammation-related proteins in rat tissues. Elevated expressions of both ALKBH5 and PTBP1 were found in the myocardial tissues of LPS-induced septic rats. ALKBH5 knockdown could restore the cell viability and cell pyroptosis inhibited by LPS, while ALKBH5 promoted PTBP1 mRNA stability by affecting its N6-methyladenosine (m6A) modification. In vivo experiments showed that PTBP1 knockdown could largely reverse the antiproliferative and pro-pyroptosis effects of ALKBH5 in LPS-exposed H9C2 cells. ALKBH5 knockdown in in vivo experiments was found to suppress the expressions of pyroptosis biomarkers and attenuate myocardial injury in septic rats. ALKBH5 promoted mRNA stability and the expression of PTBP1 through m6A modification to induce pyroptosis in cardiomyocytes and ultimately aggravate sepsis-induced myocardial dysfunction.

Inhibition of IGF2BP1 attenuates the progression of endometriosis through PTBP1.

Endometriosis (EMs), manifested by pain and infertility, is a chronic inflammatory disease. The precise pathophysiology of this disease remains uncertain. Insulin-like growth factor-2 mRNA-binding protein 1 (IGF2BP1) and polypyrimidine tract-binding protein 1 (PTBP1) have both been found to regulate proliferation, apoptosis, and invasion. This study aimed to investigate the effects of IGF2BP1/PTBP1 in treating EMs. qRT-PCR and western blotting were employed to quantify IGF2BP1 and PTBP1 expression in six patients with EMs (mean age 33.83 years). The correlation analysis, STRING database prediction, and RNA immunoprecipitation were utilized to identify the relationship between IGF2BP1 and PTBP1. Ectopic endometrial volume, weight, HE staining, and IGF2BP1 silencing were utilized to estimate the effects of IGF2BP1 in EMs model rats. qRT-PCR, CCK-8, 5-ethynyl-2'-deoxyuridine (EDU) labeling, Transwell assay, and flow cytometry were utilized to assess the effects of IGF2BP1/PTBP1 on the proliferation, migration, invasion, and apoptosis of ectopic endometrial stromal cells (eESCs). Furthermore, western blotting was employed to evaluate expressions of PCNA, VEGF, and E-cadherin in EMs rats and eESCs. The mRNA and protein levels of IGF2BP1 and PTBP1 in the ectopic and eutopic endometrium of EMs patients were significantly increased. RNA immunoprecipitation revealed a close interaction of IGF2BP1 with PTBP1. Additionally, the endometrial volume, weight, and histopathologic scores in rats were significantly reduced after IGF2BP1 silencing. IGF2BP1 silencing also decreased the expression of PCNA and VEGF, and increased E-cadherin expression in endometrial tissues of EMs rats. Moreover, IGF2BP1 silencing inhibited proliferation, migration, and invasion and promoted apoptosis through PTBP1 in eESCs. IGF2BP1 exhibits potential beneficial properties in the management of EMs by interacting with PTBP1, thereby highlighting IGF2BP1 as a promising therapeutic target for EMs.

Reducing polypyrimidine tract‑binding protein 1 fails to promote neuronal transdifferentiation on HT22 and mouse astrocyte cells under physiological conditions.

In contrast to prior findings that have illustrated the conversion of non-neuronal cells into functional neurons through the specific targeting of polypyrimidine tract-binding protein 1 (PTBP1), accumulated evidence suggests the impracticality of inducing neuronal transdifferentiation through suppressing PTBP1 expression in pathological circumstances. Therefore, the present study explored the effect of knocking down PTBP1 under physiological conditions on the transdifferentiation of mouse hippocampal neuron HT22 cells and mouse astrocyte (MA) cells. A total of 20 µM negative control small interfering (si)RNA and siRNA targeting PTBP1 were transfected into HT22 and MA cells using Lipo8000™ for 3 and 5 days, respectively. The expression of early neuronal marker βIII-Tubulin and mature neuronal markers NeuN and microtubule-associated protein 2 (MAP2) were detected using western blotting. In addition, βIII-tubulin, NeuN and MAP2 were labeled with immunofluorescence staining to evaluate neuronal cell differentiation in response to PTBP1 downregulation. Under physiological conditions, no significant changes in the expression of βIII-Tubulin, NeuN and MAP2 were found after 3 and 5 days of knockdown of PTBP1 protein in both HT22 and MA cells. In addition, the immunofluorescence staining results showed no apparent transdifferentiation in maker levels and morphology. The results suggested that the knockdown of PTBP1 failed to induce neuronal differentiation under physiological conditions.

A Novel Interaction between RUNX1 and the Splicing Factor PTBP1 Is Enriched in Leukemia Cells

RUNX1 and CBFβ form a critical hematopoietic transcription factor complex. RUNX1 is important not only for normal blood development, but also in leukemia. In the context of Inversion 16 acute myeloid leukemia (AML), RUNX1 is required for the activity of CBFβ-SMMHC (CM), the fusion oncoprotein generated by a chromosomal rearrangement and driver of this subtype of AML. The respective roles RUNX1 and CBFβ play in transcriptional regulation are well characterized but the role of other interacting partners is less well understood. To identify novel RUNX1 binding partners, we immunoprecipitated the transcription factor in mouse leukemia cells expressing CBFβ-SMMHC (CM+) and analyzed precipitated proteins by mass spectrometry. One of the proteins identified was the splicing factor Polypyrimidine Tract Binding Protein 1 (PTBP1). PTBP1 is an RNA binding protein that regulates alternative splicing of mRNAs. PTBP1 is required for normal hematopoiesis, including roles in stem cell maintenance, erythroid differentiation, and B-cell selection. However, a role for PTBP1 in leukemia has yet to be described. We confirmed the association of PTBP1 with RUNX1 via immunoprecipitation/western blot in mouse CM+ leukemia cells and the human Inv(16) cell line, ME-1. Next, we asked if this interaction is unique to inv(16) AML. We found that antibodies against RUNX1, but not isotype control antibodies, immunoprecipitated PTBP1 in a variety of myeloid (Molm-13, MV411, Kasumi-1) and lymphoid (Jurkat, MOLT-4, REH, SEM) human leukemia cell lines, indicating that this interaction occurs in multiple leukemia subtypes. To identify the region of RUNX1 required for the interaction with PTBP1, we used two deletion mutants found in patients with RUNX1-Familial Platelet Disorder ( RUNX1-FPD), RUNX1-R232 and RUNX1-Y287. We observed strong binding of PTBP1 with full length RUNX1, but not with either truncation mutant indicating that the RUNX1 C-terminus is required for interaction with PTBP1. To determine location of this novel interaction, we used proximity ligation assay (PLA). We found that the RUNX1:PTBP1 association occurred exclusively in the nucleus in both mouse and human leukemia cells. Next, we asked if this association is observed in healthy hematopoietic cells. By PLA, we found that the RUNX1:PTBP1 interaction is significantly increased in mouse leukemic cells compared to wild type lineage depleted (lin-) mouse bone marrow cells. To determine if the decrease of PLA signal in healthy bone marrow cells was due to spatial separation of PTBP1 and RUNX1, we performed immunofluorescence staining. We observed diffuse nuclear staining of both proteins in the majority of both healthy and leukemic cells. These results indicate that the interaction between RUNX1 and PTBP1 is significantly increased in leukemia cells, despite both proteins being expressed in similar patterns in both healthy and leukemic cells. During our experiments, we noticed large variations in PTBP1 expression levels in different mouse CM+ leukemia samples. To test whether PTBP1 levels correlate with a difference in leukemia stem cell activity, we performed colony assays using equal numbers of leukemia cells from samples with differing PTBP1 expression. We found that samples expressing high levels of PTBP1 resulted in a statistically significant increase in colony number. In addition, the colonies that formed from PTBP1 high samples were notably larger than those formed from PTBP1 low cells, implying a relationship between PTBP1 and leukemia stem cell self-renewal and proliferation. To determine if human AML samples show the same variability in PTBP1 levels, we performed western blot analysis using a panel of nine de novo and relapsed AML samples. Like our findings in mouse leukemia, human samples showed high variability in PTBP1 levels. We are currently addressing whether increased PTBP1 directly promotes leukemia progression. Collectively, our results demonstrate that PTBP1, a splicing regulator, is a novel RUNX1 interacting partner whose association with RUNX1 is significantly increased in leukemia cells. In addition, our data imply a potential role in leukemia stem cell proliferation, self-renewal and a role for PTBP1 in the splicing of RUNX1 target genes, perhaps generating leukemia specific splicing variants. This work has the potential to identify a new component of the RUNX1 transcriptional complex important for leukemogenesis.

Experimental Study of Warburg Effect in Keloid Nodules: Implication for Downregulation of miR-133b.

A keloid is composed of several nodules, which are divided into two zones: the central zone (CZ; a hypoxic region) and the marginal zone (MZ; a normoxic region). Keloid nodules play a key role in energy metabolic activity for continuous growth by increasing in number and total area. In this study, we aimed to investigate the roles of the zones in the execution of the Warburg effect and identify which microRNAs regulate this phenomenon in keloid tissue. Eleven keloids from patients were used. Using immunohistochemical analysis, 179 nodules were randomly chosen from these keloids to identify glycolytic enzymes, autophagic markers, pyruvate kinase M (PKM) 1/2, and polypyrimidine tract binding protein 1 (PTBP1). Western blot and qRT-PCR tests were also performed for PKM, PTBP1, and microRNAs (miR-133b and miR-200b, c). Immunohistochemical analysis showed that the expression of the autophagic (LC3, p62) and glycolytic (GLUT1, HK2) were significantly higher in the CZ than in the MZ. PKM2 expression was significantly higher than PKM1 expression in keloid nodules. Furthermore, PKM2 expression was higher in the CZ than in the MZ. However, PKM1 and PTBP1 expression levels were higher in the MZ than in the CZ. The qRT-PCR analysis showed that miR-133b-3p was moderately downregulated in the keloids compared with its expression in the normal skin tissue. The Warburg effect occurred individually in nodules. The MZ presented PKM2-positive fibroblasts produced by activated PTBP1. In the CZ, PKM2-positive fibroblasts produced lactate. MiR-133b-3p was predicted to control the Warburg effect in keloids.

PTBP1 promotes hepatocellular carcinoma progression by regulating the skipping of exon 9 in NUMB pre-mRNA

Aberrant alternative splicing is one of the important causes of cancer. Polypyrimidine tract binding protein 1 (PTBP1) has been found to be involved in splicing regulation in a variety of tumors. Here, we observed significant up-regulation of PTBP1 in primary hepatocellular carcinoma (HCC) tissues. High levels of PTBP1 expression were associated with poor prognosis and increased metastatic potential in HCC. In vitro studies demonstrated that elevated PTBP1 promoted both migration and invasion by HCC cells. In contrast, knockdown of PTBP1 significantly inhibited the migration and invasion of HCC cells in vitro. Further, up-regulation of PTBP1 markedly accumulated the expression of oncogenic isoform of NUMB, NUMB-PRRL. We observed two isoforms of NUMB, NUMB-PRRL and NUMB-PRRS exhibit opposite function in HCC cells, which partially explain PTBP1 plays the tumor promoting roles in a NUMB splicing-dependent manner. In summary, our study indicates that PTBP1 may serve as an oncogene in HCC patients by regulating the alternative splicing of NUMB exon 9 and could potentially serve as a prognostic indicator.

PTBP1 enforces ATR-CHK1 signaling determining the potency of CDC7 inhibitors

CDC7 kinase is crucial for DNA replication initiation and fork processing. CDC7 inhibition mildly activates the ATR pathway, which further limits origin firing; however, to date the relationship between CDC7 and ATR remains controversial. We show that CDC7 and ATR inhibitors are either synergistic or antagonistic depending on the degree of inhibition of each individual kinase. We find that Polypyrimidine Tract Binding Protein 1 (PTBP1) is important for ATR activity in response to CDC7 inhibition and genotoxic agents. Compromised PTBP1 expression makes cells defective in RPA recruitment, genomically unstable, and resistant to CDC7 inhibitors. PTBP1 deficiency affects the expression and splicing of many genes indicating a multifactorial impact on drug response. We find that an exon skipping event in RAD51AP1 contributes to checkpoint deficiency in PTBP1-deficient cells. These results identify PTBP1 as a key factor in replication stress response and define how ATR activity modulates the activity of CDC7 inhibitors.

MiR-506 targets polypyrimidine tract-binding protein 1 to inhibit airway inflammatory response and remodeling via mediating Wnt/β-catenin signaling pathway.

Airway remodeling, which contributes to the clinical course of childhood asthma, occurs due to airway inflammation and is featured by anomalous biological behaviors of airway smooth muscle cells (ASMCs). microRNA (miRNA) plays an essential role in the etiopathogenesis of asthma. This research was aimed to characterize miR-506 in asthma and uncover potential regulatory machinery. The asthmatic cell model was established by treating ASMCs with transforming growth factor-beta1 (TGF-β1) and assessed by the levels of interleukin (IL)-1β and interferon gamma (IFN-γ). Using real-time quantitative polymerase chain reaction, mRNA expression of miR-506 and polypyrimidine tract-binding protein 1 (PTBP1) was measured. Cell counting kit-8 and Transwell migration tests were used for estimating the capacity of ASMCs to proliferate and migrate. Luciferase reporter assay was used to corroborate whether miR-506 was directly bound to PTBP1. Expression of PTBP1, collagen I and III, and essential proteins of the wingless-related integration (Wnt)/β-catenin pathway (β-catenin, c-MYC and cyclin D1) was accomplished by Western blot analysis. The involvement of Wnt/β-catenin signaling in asthma was confirmed by Wnt signaling pathway inhibitor (IWR-1). miR-506 was poorly expressed in asthmatic tissues and cell model. Functionally, overexpression of miR-506 reduced aberrant proliferation, migration, inflammation and collagen deposition of ASMCs triggered by TGF-β1. Mechanically, miR-506 directly targeted the 3' untranslated region (3-UTR) of PTBP1 and had a negative regulation on PTBP1 expression. Moreover, overexpression of miR-506 suppressed the induction of Wnt/β-catenin pathway. The administration of IWR-1 further validated negative correlation between miR-506 and the Wnt/β-catenin pathway in asthma. Our data indicated that targeting miR-506/PTBP1/Wnt/β-catenin axis might point in a helpful direction for treating asthma in children.

Neural Isoforms of Agrin Are Generated by Reduced PTBP1-RNA Interaction Network Spanning the Neuron-Specific Splicing Regions in AGRN.

Agrin is a heparan sulfate proteoglycan essential for the clustering of acetylcholine receptors at the neuromuscular junction. Neuron-specific isoforms of agrin are generated by alternative inclusion of three exons, called Y, Z8, and Z11 exons, although their processing mechanisms remain elusive. We found, by inspection of splicing cis-elements into the human AGRN gene, that binding sites for polypyrimidine tract binding protein 1 (PTBP1) were extensively enriched around Y and Z exons. PTBP1-silencing enhanced the coordinated inclusion of Y and Z exons in human SH-SY5Y neuronal cells, even though three constitutive exons are flanked by these alternative exons. Deletion analysis using minigenes identified five PTBP1-binding sites with remarkable splicing repression activities around Y and Z exons. Furthermore, artificial tethering experiments indicated that binding of a single PTBP1 molecule to any of these sites represses nearby Y or Z exons as well as the other distal exons. The RRM4 domain of PTBP1, which is required for looping out a target RNA segment, was likely to play a crucial role in the repression. Neuronal differentiation downregulates PTBP1 expression and promotes the coordinated inclusion of Y and Z exons. We propose that the reduction in the PTPB1-RNA network spanning these alternative exons is essential for the generation of the neuron-specific agrin isoforms.

Polypyrimidine tract binding protein 1 exacerbates cardiac fibrosis by regulating fatty acid-binding protein 5.

The activation of cardiac fibroblasts (CFs) leads to overproduction of collagens and subsequently cardiac fibrosis. However, the regulatory mechanism of CF function in the process of cardiac fibrosis remains unclear. This work investigated the function of polypyrimidine tract binding protein 1 (PTBP1)/nuclear receptor NR4A1 (Nur77)/fatty acid-binding protein 5 (FABP5) axis in myocardial fibrosis. Cardiac fibrosis was induced in mice suffered left anterior descending ligation. In parallel, neonatal mouse CFs were isolated and stimulated with transforming growth factor-β1 (TGF-β1). Cardiac fibrosis was evaluated by Masson's trichrome staining. Expression of PTBP1, Nur77, FABP5, collagen I, and collagen III was measured by quantitative real-time PCR and western blotting. Proliferation of CFs was assessed by 5-ethynyl-2'-deoxyuridine assay. Molecular interaction was validated by RNA-binding protein immunoprecipitation, chromatin immunoprecipitation, and dual luciferase reporter assay. PTBP1 was up-regulated (P<0.05), whereas Nur77 (P<0.05) and FABP5 (P<0.05) were down-regulated in the fibrotic hearts of mice and TGF-β1-exposed CFs. PTBP1 overexpression facilitated proliferation (P<0.05) and collagen I (P<0.05) and collagen III (P<0.05) expression of CFs after stimulation with TGF-β1. PTBP1 reduced Nur77 stability (P<0.05) to inhibit Nur77 expression (P<0.05) in CFs. Nur77 bound to FABP5 promoter to promote the transcription (P<0.05) and expression (P<0.05) of FABP5. Silencing of Nur77 or FABP5 abolished the inhibitory effect of PTBP1 knockdown on proliferation (P<0.05) and collagen I (P<0.05) and collagen III (P<0.05) expression of CFs in vitro. PTBP1 depletion ameliorated cardiac fibrosis (P<0.05), α-smooth muscle actin (P<0.05), and collagen I (P<0.05) expression in myocardial infarction mice through regulating Nur77/FABP5 pathway (P<0.05) in vivo. PTBP1 contributed to cardiac fibrosis via promoting CF proliferation and collagen deposition through Nur77 mRNA decay and subsequent transcription inhibition of FABP5. Our findings suggest that PTBP1/Nur77/FABP5 axis may be potential targets for cardiac fibrosis therapy.

A pan-cancer analysis of the oncogenic role of polypyrimidine tract binding protein 1 (PTBP1) in human tumors

Polypyrimidine tract-binding protein 1 (PTBP1) is an RNA-binding protein that regulates several posttranscriptional events and is closely related to the development of multiple tumors. However, little is known about PTBP1. Thus, we carried out a systematic pan-cancer analysis to explore the relationship between PTBP1 and cancer. We used The Cancer Genome Atlas, Gene Expression Omnibus, and Human Protein Atlas datasets, as well as several bioinformatics tools, to explore the role of PTBP1 in 33 tumor types. The expression of PTBP1 in most tumor tissues was higher than that in normal tissues. Survival analysis indicated that overexpression of PTBP1 generally predicted poor overall survival in patients with tumors such as adrenocortical carcinoma, liver hepatocellular carcinoma, lung adenocarcinoma, and skin cutaneous melanoma. In addition, we compared the phosphorylation and immune infiltration of PTBP1 in cancer-associated fibroblasts between normal and primary tumor tissues and explored the putative functional mechanism of tumorigenesis mediated by PTBP1. These results provide clues to better understand PTBP1 from the perspective of bioinformatics and highlight its importance in various human cancers.

Clinicopathological significance and prognostic value of polypyrimidine tract binding protein 1 (PTBP1) in gastric cancer.

BackgroundPolypyrimidine tract binding protein 1 (PTBP1) is a member of heterogeneous nuclear ribonucleoprotein (hnRNP) family and has recently been reported to contribute to development and progression of various tumors. However, the clinicopathological significance and prognostic value of PTBP1 in gastric cancer have not been sufficiently elucidated.MethodsBioinformatic analysis of The Cancer Genome Atlas (TCGA) data were employed to analyze the expression of PTBP1 mRNA and its prognostic value in gastric cancer. The expression type of PTBP1 in gastric cancer cells was further confirmed through reverse transcription polymerase chain reaction (RT-PCR) and western blot assay. Then, the association between PTBP1 protein expression and clinicopathological features was analyzed based on immunohistochemical staining results in gastric cancer tissue microarray including 311 cases. The prognostic value of PTBP1 protein was explored through univariate and multivariate analyses. Additionally, cell count and transwell assay were performed to detect the biological role of PTBP1 in gastric cancer cells in vitro.ResultsPTBP1 was highly expressed in gastric cancer cells and tissues at mRNA and protein level. High expression of PTBP1 was closely related to several clinicopathological features, including gender, age at surgery, histological type, TNM stage and lymph node metastasis. Moreover, high expression PTBP1 predicts poor prognosis, and may be an independent prognostic factor for overall survival in gastric cancer patients. Knockdown of PTBP1 substantially suppressed the proliferation, migration and invasion of gastric cancer cells in vitro.ConclusionsPTBP1 is up-regulated and predicts poor prognosis in gastric cancer. PTBP1 may serve as a biomarker of poor prognosis and a novel target in treating gastric cancer.

Bone Marrow Mesenchymal Stem Cells (BMSCs) Promote the Metastasis of Thyroid Papillary Cancer by Inhibiting Poly-Pyrimidine Tract Binding Protein 1 (PTBP1)

We aimed to explore the mechanism underlying the role of bone marrow mesenchymal stem cells (BMSCs) in the invasion of papillary thyroid cancer (PTC) cells. BMSCs were co-cultured with PTC cells WRO or normal thyroid follicular epithelial cells T3TD followed by analysis of cell migration and proliferation by Transwell assay and MTT assay. Cells were transfected with shRNA or overexpression of PTBP1, followed by measuring cell proliferation and invasion and PTBP1 expression by RT-qPCR and Western blot. Co-cultivation with MSC promoted the malignant transformation of WRO, inhibited the RNA-binding protein PTBP1 and activation of GS3Kβ/Akt. In addition, silencing of PTBP1 accelerated cell invason and induced overexpression of EMT proteins, while overexpression of PTBP1 inhibited cell proliferation and migration. In conclusion, BMSCs might promote PTC invasion and metastasis by inhibiting PTBP1 expression, providing a novel insight into the treatment of PTC.

N6-Methyladenosine-modified lncRNA LINREP promotes Glioblastoma progression by recruiting the PTBP1/HuR complex.

Glioblastoma multiforme (GBM) is acknowledged as the most aggressive primary brain tumor in adults. It is typically characterized by the high heterogeneity which corresponds to extensive genetic mutations and complex alternative splicing (AS) profiles. Known as a major repressive splicing factor in AS, polypyrimidine tract-binding protein 1 (PTBP1) is involved in the exon skipping events of multiple precursor mRNAs (pre-mRNAs) in GBM. However, precise mechanisms that modulate the expression and activity of PTBP1 remain to be elucidated. In present study, we provided evidences for the role of a long intergenic noncoding RNA (LINREP) implicated in the regulation of PTBP1-induced AS. LINREP interacted with PTBP1 and human antigen R (HuR, ELAVL1) protein complex and protected PTBP1 from the ubiquitin-proteasome degradation. Consequently, a broad spectrum of PTBP1-induced spliced variants was generated by exon skipping, especially for the skipping of reticulon 4 (RTN4) exon 3. Interestingly, LINREP also promoted the dissociation of nuclear UPF1 from PTBP1, which increased the binding of PTBP1 to RTN4 transcripts, thus enhancing the skipping of RTN4 exon 3 to some extent. Besides, HuR recruitment was essential for the stabilization of LINREP via a manner dependent on N6-methyladenosine (m6A) formation and identification. Taken together, our results demonstrated the functional significance of LINREP in human GBM for its dual regulation of PTBP1-induced AS and its m6A modification modality, implicating that HuR/LINREP/PTBP1 axis might serve as a potential therapeutic target for GBM.

PTBP1 is a Novel Poor Prognostic Factor for Glioma.

Objective Polypyrimidine tract-binding protein 1 (PTBP1) is an RNA-binding protein, which plays a role in pre-mRNA splicing and in the regulation of alternative splicing events. However, little was known about the correlation between PTBP1 and glioma and its prognostic significance in glioma patients. Our aim was to investigate the expression, functional role, and prognostic value of PTBP1 in glioma. Methods We explored the expression of PTBP1 protein using immunohistochemistry in 150 adult malignant glioma tissues and 20 normal brain tissues and evaluated its association with clinicopathological parameters by chi-square test. Kaplan-Meier method was used to evaluate the prognostic effect of PTBP1 in glioma. Univariate/multivariate Cox analyses were used to identify independent prognostic factors. Transcriptional regulation network was constructed based on differentially expressed genes (DEGs) of PTBP1 from TCGA/CGGA database. GO and KEGG enrichment analyses were used to explore the function and pathways of DEGs. Results Out of the 150 malignant glioma tissues (60 LGG and 90 GBMs) and 20 normal brain tissues in our cohort, PTBP1 protein was high expressed in glioma tissues (79/150, 52.7%), but no expression was detected in normal brain tissues (0/20, 0%). The expression of PTBP1 was significantly higher in GBMs (P < 0.001). More than half of GBMs (62/90, 68.9%) were PTBP1 high expression. Chi-square test showed that the expression of PTBP1 was correlated with patient age, WHO grade, Ki-67 index, and IDH status. High expression of PTBP1 was significantly associated with poor prognosis in glioma, and it was an independent risk factor in glioma patients. Furthermore, we shed light on the underlying mechanism of PTBP1 by constructing a miR-218-TCF3-PTBP1 transcriptional network in glioma. Conclusion PTBP1 was high expressed in glioma, and it significantly correlated with poor prognosis, suggesting a potential therapeutic target for glioma, particularly for GBM.

Human umbilical cord-derived mesenchymal stem cells promote repair of neonatal brain injury caused by hypoxia/ischemia in rats.

Administration of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) is believed to be an effective method for treating neurodevelopmental disorders. In this study, we investigated the possibility of hUC-MSCs treatment of neonatal hypoxic/ischemic brain injury associated with maternal immune activation and the underlying mechanism. We established neonatal rat models of hypoxic/ischemic brain injury by exposing pregnant rats to lipopolysaccharide on day 16 or 17 of pregnancy. Rat offspring were intranasally administered hUC-MSCs on postnatal day 14. We found that polypyrimidine tract-binding protein-1 (PTBP-1) participated in the regulation of lipopolysaccharide-induced maternal immune activation, which led to neonatal hypoxic/ischemic brain injury. Intranasal delivery of hUC-MSCs inhibited PTBP-1 expression, alleviated neonatal brain injury-related inflammation, and regulated the number and function of glial fibrillary acidic protein-positive astrocytes, thereby promoting plastic regeneration of neurons and improving brain function. These findings suggest that hUC-MSCs can effectively promote the repair of neonatal hypoxic/ischemic brain injury related to maternal immune activation through inhibition of PTBP-1 expression and astrocyte activation.

Alternative splicing analysis showed the splicing factor polypyrimidine tract-binding protein 1 as a potential target in acute myeloid leukemia therapy.

Alternative splicing (AS) is a universal post-transcriptional regulation process in cells, and increasing evidences have validated its crucial role in tumors. We collected AS event, gene expression, and clinical data of 178 AML patients from The Cancer Genome Atlas (TCGA) project. More than 1,000 AS events were found associated with overall survival (OS), and alternate promoter (AP) events were the most significant. The expression of the KIAA0930 transcript was the most significantly different AS event selected from AP events and significantly correlated with the expression of the splicing factor (SF) polypyrimidine tract-binding protein 1 (PTBP1). Then, the roles of PTBP1 on AS of the KIAA0930 and the proliferation of AML cells were confirmed. KIAA0930 variant 1 (KIAA0930-1) was upregulated and variant 2 (KIAA0930-2) downregulated with knockdown PTBP1 expression of AML cells by specific shRNA. A low level of PTBP1 can decrease the proliferation ability of AML cells. In conclusion, the results showed that PTBP1 might be a potential target for AML therapy.

Tobacco Smoking Increases Methylation of Polypyrimidine Tract Binding Protein 1 Promoter in Intracranial Aneurysms.

DNA methylation at the gene promoter region is reportedly involved in the development of intracranial aneurysm (IA). This study aims to investigate the methylation levels of polypyrimidine tract-binding protein 1 (PTBP1) in IA, as well as its potential to predict IA. Forty-eight patients with IA and 48 age- and sex-matched healthy controls were recruited into this study. Methylation levels of CpG sites were determined via bisulfite pyrosequencing. The PTBP1 levels in the blood were determined using a real-time quantitative reverse transcription-polymerase chain reaction test. Significant differences were found between IAs and controls in CpG1 (p = 0.001), CpG2 (p < 0.001), CpG3 (p = 0.037), CpG4 (p = 0.003), CpG5 (p = 0.006), CpG6 (p = 0.02), and mean methylation (p < 0.001). The mRNA level of PTBP1 in the blood was much lower in IAs compared with controls (p = 0.002), and the PTBP1 expression was significantly associated with DNA methylation promoter levels in individuals (r = −0.73, p < 0.0001). In addition, stratification analysis comparing smokers and non-smokers revealed that tobacco smokers had significantly higher levels of DNA methylation in PTBP1 than non-smokers (p = 0.002). However, no statistical difference in PTBP1 methylation was found between ruptured and unruptured IA groups (p > 0.05). The ROC analyses of curves revealed that PTBP1 methylation may be a predictor of IA regardless of sex (both sexes, area under curve (AUC) = 0.78, p < 0.0001; male, AUC = 0.76, p = 0.002; female, AUC = 0.79, p < 0.0001). These findings suggest that long-term tobacco smoke exposure led to DNA methylation in the promoter region of the PTBP1 gene, which further decreased PTBP1 gene expression and participated in the pathogenesis of IA. The methylation of PTBP1 may be a potential predictive marker for the occurrence of IA.

Polypyrimidine tract-binding protein 1 regulates the Sertoli cell blood-testis barrier by promoting the expression of tight junction proteins.

Sertoli cells (SCs) are an important component of spermatogenic tubules. The blood-testis barrier (BTB) is composed of SCs and is necessary for the development and maturity of spermatogenic cells. When the tight connection between SCs is destroyed, the BTB loses its integrity, leading to impaired spermatogenesis. Polypyrimidine tract-binding protein 1 (PTBP1) is a key protein involved in precursor mRNA splicing and selective splicing events, which directly affects tumor cell proliferation and influences the formation of the blood-tumor barrier by regulating the expression levels of tight junction-associated proteins. The present study revealed that the expression of PTBP1 was downregulated following a decrease in spermatogenic activity at the phase of senescence. TM4 cells were transfected with lentivirus-short hairpinRNA-PTBP1 to evaluate the effect of silencing PTBP1 on the expression levels of tight junction proteins and the integrity of tight junctions between adjacent SCs. Western blot analysis indicated that the expression levels of Zonula occludens 1, occludin and claudin-5 decreased significantly due to silencing of PTBP1 in SCs. Through detecting trans-epithelial electrical resistance, it was revealed that silencing of PTBP1 broke the integrity of tight junctions between adjacent SCs. The results suggested that PTBP1 maintained the integrity of the BTB by promoting the expression levels of tight junction-associated proteins and revealed the possible mechanism of PTBP1 in regulating spermatogenesis.