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The alternative splicing of intersectin 1 regulated by PTBP1 promotes human glioma progression.

ABSTRACT: Intersectin 1 (ITSN1) contains two isoforms: ITSN1-S and ITSN1-L, which are highly regulated by alternative splicing. Our previous results showed that the two isoforms of ITSN1 displayed opposite functions: ITSN1-S promoted glioma development, while ITSN1-L exerted an inhibitory role in glioma progression. In this study, our transcriptome analysis using a large glioma cohort indicated that the ratio of ITSN1-S/ITSN1-L was positively correlated with glioma grading and poor prognosis. We identified the RNA-binding protein polypyrimidine tract-binding protein 1 (PTBP1) as an ITSN1 pre-mRNA interaction protein through RNA pull-down assay and RNA immunoprecipitation assay. Knockdown of PTBP1 decreased the ratio of ITSN1-S/ITSN1-L. Minigene reporter assay and mutation analyses further confirmed PTBP1 targeted polypyrimidine sequences on ITSN1 exon 30 (TTGCACTTCAGTATTTT) and promoted the inclusion of ITSN1 exon 30. Subsequently, silencing PTBP1 inhibited glioma cell proliferation, migration, and invasion by down-regulating the ratio of ITSN1-S/ITSN1-L. Taken together, our study provides a novel mechanism that PTBP1 modulates the alternative splicing of ITSN1 and promotes glioma proliferation and motility by up-regulating the ratio of ITSN1-S/ITSN1-L, thereby highlighting that PTBP1 may be an attractive therapeutic target for gliomas.

SUBMITTER: Lan C

PROVIDER: S-EPMC9519902 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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The alternative splicing of intersectin 1 regulated by PTBP1 promotes human glioma progression.

Lan Chungen C Zhang Huikun H Wang Kezhen K Liu Xiaoli X Zhao Yawen Y Guo Zhifang Z Zhang Ning N Zhou Yongxia Y Gao Manzhi M Gu Feng F Ma Yongjie Y

Cell death & disease 20220928 9

Intersectin 1 (ITSN1) contains two isoforms: ITSN1-S and ITSN1-L, which are highly regulated by alternative splicing. Our previous results showed that the two isoforms of ITSN1 displayed opposite functions: ITSN1-S promoted glioma development, while ITSN1-L exerted an inhibitory role in glioma progression. In this study, our transcriptome analysis using a large glioma cohort indicated that the ratio of ITSN1-S/ITSN1-L was positively correlated with glioma grading and poor prognosis. We identifie ...[more]

PMID: 36171198

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Project description:BackgroundAerobic glycolysis is a tumor cell phenotype and a hallmark in cancer research. The alternative splicing of the pyruvate kinase M (PKM) gene regulates the expressions of PKM1/2 isoforms and the aerobic glycolysis of tumors. Polypyrimidine tract binding protein (PTBP1) is critical in this process; however, its impact and underlying mechanisms in colorectal cancer (CRC) remain unclear. This study aimed to investigate the role of PTBP1 crotonylation in CRC progression.MethodsThe crotonylation levels of PTBP1 in human CRC tissues and cell lines were analyzed using crotonylation proteomics and immunoprecipitation. The main crotonylation sites were identified by immunoprecipitation and immunofluorescent staining. The glycolytic capacities of CRC cells were evaluated by measuring the glucose uptake, lactate production, extracellular acidification rate, and glycolytic proton efflux rate. The role and mechanism of PTBP1 crotonylation in PKM alternative splicing were determined by Western blot, quantitative real-time PCR (RT-qPCR), RNA immunoprecipitation, and immunoprecipitation. The effects of PTBP1 crotonylation on the behaviors of CRC cells and CRC progression were assessed using CCK-8, colony formation, cell invasion, wound healing assays, xenograft model construction, and immunohistochemistry.ResultsThe crotonylation level of PTBP1 was elevated in human CRC tissues compared to peritumor tissues. In CRC tissues and cells, PTBP1 was mainly crotonylated at K266 (PTBP1 K266-Cr), and lysine acetyltransferase 2B (KAT2B) acted as the crotonyltranferase. PTBP1 K266-Cr promoted glycolysis and lactic acid production, increasing the PKM2/PKM1 ratio in CRC tissues and cells. Mechanistically, PTBP1 K266-Cr enhanced the interaction of PTBP1 with heterogeneous nuclear ribonucleoprotein A1 and A2 (hnRNPA1/2), thus affecting the PKM alternative splicing. PTBP1 K266-Cr facilitated CRC cell proliferation, migration, and metastasis in vitro and in vivo. Pathologically, a high level of PTBP1 K266-Cr was associated with poor prognosis in CRC patients.ConclusionsCrotonylation of PTBP1 coordinates tumor cell glycolysis and promotes CRC progression by regulating PKM alternative splicing and increasing PKM2 expression.

Project description:BackgroundGolgi Membrane Protein 1 (GOLM1), a protein involved in the trafficking of proteins through the Golgi apparatus, has been shown to be oncogenic in a variety of human cancers. Here, we examined the role of GOLM1 in the development of human glioma.MethodsqRT-PCR, immunohistochemistry, and western blot analysis were performed to evaluate GOLM1 levels in cell lines and a cohort of primary human glioma and non-neoplastic brain tissue samples. Glioma cell lines were modified with lentiviral constructs expressing short hairpin RNAs targeting GOLM1 or overexpressing the protein to assess function in proliferation, viability, and migration and invasion in vitro using EdU, CCK8, clone-forming, Transwell assays, 3D tumor spheroid invasion assay and in vivo in orthotopic implantations. Protein lysates were used to screen a membrane-based antibody array to identify kinases mediated by GOLM1. Specific inhibitors of PDGFRα (AG1296) and AKT (MK-2206) were used to examine the regulation of PDGFA/PDGFRα on GOLM1 and the underlying pathway respectively.ResultsqRT-PCR, immunohistochemistry and western blot analysis revealed GOLM1 expression to be elevated in glioma tissues and cell lines. Silencing of GOLM1 attenuated proliferation, migration, and invasion of U251, A172 and P3#GBM (primary glioma) cells, while overexpression of GOLM1 enhanced malignant behavior of U87MG cells. We further demonstrated that activation of AKT is the driving force of GOLM1-promoted glioma progression. The last finding of this research belongs to the regulation of PDGFA/PDGFRα on GOLM1, while GOLM1 was also a key element of PDGFA/PDGFRα-mediated activation of AKT, as well as the progression of glioma cells.ConclusionsPDGFA/PDGFRα-regulated GOLM1 promotes glioma progression possibly through activation of a key signaling kinase, AKT. GOLM1 interference may therefore provide a novel therapeutic target and improve the efficacy of glioma treatment, particularly in the case of the proneural molecular subtype of human glioma.

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The alternative splicing of intersectin 1 regulated by PTBP1 promotes human glioma progression.

Publications

The alternative splicing of intersectin 1 regulated by PTBP1 promotes human glioma progression.

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