PCBP2 Modulates Neural Apoptosis and Astrocyte Proliferation After Spinal Cord Injury

Burden re-analysis of neurodevelopmental disorder cohorts for prioritization of candidate genes

This study aimed to uncover novel genes associated with neurodevelopmental disorders (NDD) by leveraging recent large-scale de novo burden analysis studies to enhance a virtual gene panel used in a diagnostic setting. We re-analyzed historical trio-exome sequencing data from 745 individuals with NDD according to the most recent diagnostic standards, resulting in a cohort of 567 unsolved individuals. Next, we designed a virtual gene panel containing candidate genes from three large de novo burden analysis studies in NDD and prioritized candidate genes by stringent filtering for ultra-rare de novo variants with high pathogenicity scores. Our analysis revealed an increased burden of de novo variants in our selected candidate genes within the unsolved NDD cohort and identified qualifying de novo variants in seven candidate genes: RIF1, CAMK2D, RAB11FIP4, AGO3, PCBP2, LEO1, and VCP. Clinical data were collected from six new individuals with de novo or inherited LEO1 variants and three new individuals with de novo PCBP2 variants. Our findings add additional evidence for LEO1 as a risk gene for autism and intellectual disability. Furthermore, we prioritize PCBP2 as a candidate gene for NDD associated with motor and language delay. In summary, by leveraging de novo burden analysis studies, employing a stringent variant filtering pipeline, and engaging in targeted patient recruitment, our study contributes to the identification of novel genes implicated in NDDs.

Runx2 Suppresses Astrocyte Activation and Astroglial Scar Formation After Spinal Cord Injury in Mice

After spinal cord injury, astrocytes undergo a reactive process and form an astroglial scar, which impedes the regeneration of axons. The role of Runx2 in promoting the transformation of astrocytes in the central nervous system is well-established. However, it remains unclear whether Runx2 also plays a role in the development of astroglial scar, and the precise underlying mechanism has yet to be identified. Recently, our study using cell culture and animal models has demonstrated that Runx2 actually suppresses astrocyte activation and the formation of astroglial scar following injury. The initial results demonstrated an increase in the expression of Runx2 in astrocytes following in vivo injury. Subsequently, the overexpression of Runx2 resulted in the inhibition of astrocyte activation, reduction in the total area of astroglial scar, and restoration of neural function after 14 days of injury. However, these effects were reversed by CADD522. These findings indicate that Runx2 could potentially serve as a therapeutic intervention for spinal cord injury (SCI). Furthermore, our findings suggest that the Nuclear-matrix-targeting signal (NMTS) of Runx2 is associated with its effect. In summary, the study's results propose that targeting Runx2 may be a promising treatment approach for reactive astrocytes and astroglial scar in the recovery of SCI.

Targeting Pro-Oxidant Iron with Exogenously Administered Apotransferrin Provides Benefits Associated with Changes in Crucial Cellular Iron Gate Protein TfR in a Model of Intracerebral Hemorrhagic Stroke in Mice

We have previously demonstrated that the post-stroke administration of iron-free transferrin (apotransferrin, ATf) is beneficial in different models of ischemic stroke (IS) through the inhibition of the neuronal uptake of pro-oxidant iron. In the present study, we asked whether ATf is safe and also beneficial when given after the induction of intracerebral hemorrhage (ICH) in mice, and investigated the underlying mechanisms. We first compared the main iron actors in the brain of IS- or collagenase-induced ICH mice and then obtained insight into these iron-related proteins in ICH 72 h after the administration of ATf. The infarct size of the IS mice was double that of hemorrhage in ICH mice, but both groups showed similar body weight loss, edema, and increased ferritin and transferrin levels in the ipsilateral brain hemisphere. Although the administration of human ATf (hATf) to ICH mice did not alter the hemorrhage volume or levels of the classical ferroptosis GPX4/system xc- pathways, hATf induced better neurobehavioral performance, decreased 4-hydroxynonenal levels and those of the second-generation ferroptosis marker transferrin receptor (TfR), and restored the mRNA levels of the recently recognized cytosolic iron chaperone poly(RC) binding protein 2. In addition, hATf treatment lowered the ICH-induced increase in both endogenous mouse transferrin mRNA levels and the activation of caspase-2. In conclusion, hATf treatment provides neurobehavioral benefits post-ICH associated with the modulation of iron/oxidative players.

Upregulation of TRPC6 inhibits astrocyte activation and proliferation after spinal cord injury in rats by suppressing AQP4 expression

AIMS

This work investigates the effects and mechanisms of inhibiting TRPC6 (a non-selective cation channel) downregulation on rat astrocyte activation and proliferation following spinal cord injury (SCI) by suppressing AQP4 expression. We used HYP9 (TRPC6-specific agonist) and TGN-020 (AQP4-specific inhibitor) to explore the relationship between TRPC6 and AQP4 and their probable protective effects on SCI.

METHODS

In a rat SCI model, we randomly assigned female Sprague-Dawley rats into the following four groups: Sham, SCI, SCI+HYP9, and SCI+TGN-020. Western blotting and immunofluorescence staining were used to determine protein expression among groups following SCI. TUNEL and immunofluorescence staining were used to identify changes in the rate of apoptosis and the fraction of surviving neurons after SCI. The Basso-Beattie-Bresnahan open-field locomotor scale was used to identify changes in motor function after SCI. In vitro astrocyte scratch model, we first used the CCK8 assay to test the effects of varying doses of HYP9 or TGN-020 on astrocytes and then split the astrocytes into four groups: Con, Scratch, Scratch+HYP9, and Scratch+TGN-020. Western blotting and immunofluorescence were used to identify changes in the expression of target proteins.

RESULTS

In vivo and in vitro models, SCI dramatically decreased TRPC6 while considerably upregulating AQP4, glial fibrillary acidic protein (GFAP), and proliferating cell nuclear antigen (PCNA) expression. However, HYP9 or TGN-020 significantly suppressed activation of astrocytes, promoted neurons survival in the anterior horn of the spinal cords, and benefited the recovery of motor function in the hind limbs of rats following SCI. Interestingly, TRPC6 agonists dramatically suppressed AQP4 overexpression, indicating that the probable mechanism of HYP9 benefiting alleviation of SCI may be connected to AQP4 inhibition and astrocyte activation and proliferation reduction.

CONCLUSION

we discovered for the first time that HYP9 inhibits astrocyte activation and proliferation by inhibiting AQP4 in SCI rats in vivo and in vitro models and that it preserves neuronal survival and functional recovery after SCI.

Poly(C)-binding Protein 2 Regulates the p53 Expression via Interactions with the 5'-Terminal Region of p53 mRNA

The p53 protein is one of the major transcriptional factors which guards cell homeostasis. Here, we showed that poly(C)-binding protein 2 (PCBP2) can bind directly to the 5′ terminus of p53 mRNA by means of electrophoretic mobility shift assay. Binding sites of PCBP2 within this region of p53 mRNA were mapped using Pb2+-induced cleavage and SAXS methods. Strikingly, the downregulation of PCBP2 in HCT116 cells resulted in a lower level of p53 protein under normal and stress conditions. Quantitative analysis of p53 mRNA in PCBP2-downregulated cells revealed a lower level of p53 mRNA under normal conditions suggesting the involvement of PCBP2 in p53 mRNA stabilisation. However, no significant change in p53 mRNA level was observed upon PCBP2 depletion under genotoxic stress. Moreover, a higher level of p53 protein in the presence of rapamycin or doxorubicin and the combination of both antibiotics was noticed in PCBP2-overexpressed cells compared to control cells. These observations indicate the potential involvement of PCBP2 in cap-independent translation of p53 mRNA especially occurring under stress conditions. It has been postulated that the PCBP2 protein is engaged in the enhancement of p53 mRNA stability, probably via interacting with its 3′ end. Our data show that under stress conditions PCBP2 also modulates p53 translation through binding to the 5′ terminus of p53 mRNA. Thus PCBP2 emerges as a double-function factor in the p53 expression.

Advances in poly(rC)-binding protein 2: Structure, molecular function, and roles in cancer

Poly(rC)-binding protein 2 (PCBP2) is an RNA-binding protein that is characterized by its ability to interact with poly(C) with high affinity in a sequence-specific manner. PCBP2 contains three K homology domains, which are consensus RNA-binding domains that play a role in recognizing and combining with RNA and DNA. The specific structure and localization of PCBP2 lay the foundation for its multiple roles in transcriptional, posttranscriptional, and translational processes, even in iron metabolism. Numerous studies have indicated that PCBP2 expression is increased in many cancer types. PCBP2 is considered as an oncogene that promotes tumorigenesis, development of cancer cells, and metastasis. Here, we summarized the current evidence regarding PCBP2 in the proliferation, migration, invasion of cancer cells, and drug resistance, aiming to clarify the molecular mechanisms of PCBP2 in cancer. Results from this review suggest that an in-depth study of PCBP2 in cancer may provide novel biomarkers for prognostic or therapeutic purposes.

Nutlin-Induced Apoptosis Is Specified by a Translation Program Regulated by PCBP2 and DHX30

Activation of p53 by the small molecule Nutlin can result in a combination of cell cycle arrest and apoptosis. The relative strength of these events is difficult to predict by classical gene expression analysis, leaving uncertainty as to the therapeutic benefits. In this study, we report a translational control mechanism shaping p53-dependent apoptosis. Using polysome profiling, we establish Nutlin-induced apoptosis to associate with the enhanced translation of mRNAs carrying multiple copies of an identified 3' UTR CG-rich motif mediating p53-dependent death (CGPD-motif). We identify PCBP2 and DHX30 as CGPD-motif interactors. We find that in cells undergoing persistent cell cycle arrest in response to Nutlin, CGPD-motif mRNAs are repressed by the PCBP2-dependent binding of DHX30 to the motif. Upon DHX30 depletion in these cells, the translation of CGPD-motif mRNAs increases, and the response to Nutlin shifts toward apoptosis. Instead, DHX30 inducible overexpression in SJSA1 cells leads to decreased translation of CGPD-motif mRNAs.

Inhibition of ERK1/2 phosphorylation attenuates spinal cord injury induced astrocyte activation and inflammation through negatively regulating aquaporin-4 in rats

The extracellular signal-regulated kinase (ERK) pathway has been reported to play a pivotal role in mediating spinal cord injury (SCI) progression. The present study aimed to investigate the effects of phosphorylated ERK1/2 (p-ERK1/2) inhibition on SCI-induced astrocyte activation and inflammation and its possible mechanism in rats. Here, female Sprague-Dawley rats were randomly assigned to four groups: (1) Sham group, (2) SCI group, (3) TGN-020 group (aquaporin-4, AQP4, blocking agent), (4) PD98059 group (ERK blocking agent). A well SCI model was established by compressing the thoracic vertebra 10 level (weight 35 g, time 5 min) in rats. Western blotting and immunofluorescence staining were used to measure the expression of associated proteins after SCI. HE staining and Nissl staining were performed to detect the morphological changes of spinal cords and the number of surviving neurons following SCI, respectively. The Basso-Beattie-Bresnahan open-field rating scale was used to evaluate functional locomotor recovery following SCI in rats. Our results demonstrated that SCI significantly induced the upregulation of aquaporin-4, p-ERK1/2, glial fibrillary acidic protein, proliferating cell nuclear antigen, and proinflammatory cytokines (tumor necrosis factor-α, interleukin-6 and interleukin-1β). However, treatment with TGN-020 or PD98059 could effectively inhibit astrocyte proliferation and proinflammatory cytokine release, preserve the number of surviving ventral horn neurons, and subsequently improve the locomotor function of rats after SCI. Interestingly, the SCI-induced elevation of AQP4 expression was downregulated by p-ERK1/2 inhibition, suggesting that blocking ERK1/2 phosphorylation could attenuate astrocyte activation and inflammatory processes through negative regulation of AQP4. Therefore, p-ERK1/2 blockade may be employed as a therapeutic target for SCI.

PCBP1 and PCBP2 both bind heavily oxidized RNA but cause opposing outcomes, suppressing or increasing apoptosis under oxidative conditions

PCBP1, a member of the poly(C)-binding protein (PCBP) family, has the capability of binding heavily oxidized RNA and therefore participates in the cellular response to oxidative conditions, helping to induce apoptosis. There are four other members of this family, PCBP2, PCBP3, PCBP4, and hnRNPK, but it is not known whether they play similar roles. To learn more, we first tested their affinity for an RNA strand carrying two 8-oxoguanine (8-oxoG) residues at sites located in close proximity to each other, representative of a heavily oxidized strand or RNA with one 8-oxoG or none. Among them, only PCBP2 exhibited highly selective binding to RNA carrying two 8-oxoG residues similar to that observed with PCBP1. In contrast, PCBP3, PCBP4, and hnRNPK bound RNA with or without 8-oxoG modifications and exhibited slightly increased binding to the former. Mutations in conserved RNA-binding domains of PCBP2 disrupted the specific interaction with heavily oxidized RNA. We next tested PCBP2 activity in cells. Compared with WT HeLa S3 cells, PCBP2-KO cells established by gene editing exhibited increased apoptosis with increased caspase-3 activity and PARP1 cleavage under oxidative conditions, which were suppressed by the expression of WT PCBP2 but not one of the mutants lacking binding activity. In contrast, PCBP1-KO cells exhibited reduced apoptosis with much less caspase-3 activity and PARP cleavage than WT cells. Our results indicate that PCBP2 as well as PCBP1 bind heavily oxidized RNA; however, the former may counteract PCBP1 to suppress apoptosis under oxidative conditions.

Achieving Life through Death: Redox Biology of Lipid Peroxidation in Ferroptosis

Redox balance is essential for normal brain, hence dis-coordinated oxidative reactions leading to neuronal death, including programs of regulated death, are commonly viewed as an inevitable pathogenic penalty for acute neuro-injury and neurodegenerative diseases. Ferroptosis is one of these programs triggered by dyshomeostasis of three metabolic pillars: iron, thiols, and polyunsaturated phospholipids. This review focuses on: (1) lipid peroxidation (LPO) as the major instrument of cell demise, (2) iron as its catalytic mechanism, and (3) thiols as regulators of pro-ferroptotic signals, hydroperoxy lipids. Given the central role of LPO, we discuss the engagement of selective and specific enzymatic pathways versus random free radical chemical reactions in the context of the phospholipid substrates, their biosynthesis, intracellular location, and related oxygenating machinery as participants in ferroptotic cascades. These concepts are discussed in the light of emerging neuro-therapeutic approaches controlling intracellular production of pro-ferroptotic phospholipid signals and their non-cell-autonomous spreading, leading to ferroptosis-associated necroinflammation.

PCBP2 promotes the development of glioma by regulating FHL3/TGF-β/Smad signaling pathway

The purpose of this study was to investigate the role of Poly (C)-binding protein 2 (PCBP2) and the related signaling pathway in glioma progression. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC) were performed to measure PCBP2 messenger RNA and protein expression in glioma tissues or cells. Cell transfection was completed using Lipofectamine 2000. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, Transwell assay and flow cytometry assay were used to explore the effects of PCBP2 expression on biological behaviors of glioma cells. Western blot assay was used for the detection of pathway related proteins. Expression of PCBP2 in glioma tissues and cells were higher than that in paracancerous tissues and normal cells (both p < .01). Moreover, the elevated expression of PCBP2 was significantly correlated with tumor size (p = .001) and WHO stage (p = .010). Knockdown of PCBP2 could suppress proliferation, migration and invasion of glioma cells and promote apoptosis. Besides, the expression of transforming growth factor-β (TGF-β) pathway related proteins TGF-β1, p-Smad2 and p-Smad7 were decreased following the downregulation of PCBP2. PCBP2 also inhibited FHL3 expression by binding to FHL3-3'UTR. The inhibition of FHL3 could reverse the antitumor action caused by PCBP2 silencing. In vivo assay, PCBP2 was also found to inhibit the tumor growth of glioma. PCBP2 activates TGF-β/Smad signaling pathway by inhibiting FHL3 expression, thus promoting the development and progression of glioma.

Heterogeneous Nuclear Ribonucleoprotein E2 (hnRNP E2) Is a Component of TDP-43 Aggregates Specifically in the A and C Pathological Subtypes of Frontotemporal Lobar Degeneration

TAR DNA-binding protein 43 (TDP-43) is the major component of the ubiquitin-positive protein aggregates seen in the majority of frontotemporal lobar degeneration and amyotrophic lateral sclerosis cases. TDP-43 belongs to the heterogeneous nuclear ribonucleoprotein (hnRNP) family that is involved in the regulation of RNA transcription, splicing, transport and translation. There are a great many hnRNPs, which often have overlapping functions and act cooperatively in RNA processing. Here we demonstrate that another hnRNP family member, hnRNP E2, shows a striking accumulation within dystrophic neurites and cytoplasmic inclusions in the frontal cortex and hippocampus of a subset of FTLD-TDP cases belonging to pathological subtypes A and C, where hnRNP E2 was found to co-localize with 87% of TDP-43 immunopositive inclusions. hnRNP E2-positive inclusions were not seen in FTLD-TDP cases with the C9orf72 expansion or in any other neurodegenerative disorders examined. This interaction with TDP-43 in specific FTLD subtypes suggests different underlying neurodegenerative pathways.

Multiphosphorylation and cellular localization of poly(rC) binding protein 1 during mitosis in hela cell

OBJECTIVE

To monitor the phosphorylation modifications and cellular localization of poly(rC)-binding protein-1 (PCBP1) during the cell cycle progression of Hela cells.

RESULT

Hela cells highly synchronized at five different phases from interphase to mitosis were obtained. Using mitotic phosphoprotein-specific monoclonal antibody MPM-2, the exclusive occurrences of multiphosphorylation statuses of PCBP1 in mitosis were confirmed by a series of spots with increasing acidic pI (isoelectric point) in two rounds of 2D western blotting on the same membrane, and a visible molecular mass shift that can be eliminated by the treatment with λ phosphatase in 1D western blotting. Immnuofluorescence revealed the localization shift of PCBP1 during cell cycle, with accumulations in nucleus as a patch pattern in interphase, and a dispersive distribution without the area of the condensed chromosomes during mitosis.

CONCLUSIONS

These observations of mitosis-specific multiphosphorylations and localization shifts of PCBP1 suggest that the versatile PCBP1 was regulatable in a phosphorylation modification- and temporospatial-dependent manner in mitotic regulatory networks.

HAX1 is associated with neuronal apoptosis and astrocyte proliferation after spinal cord injury

HS1-associated protein X-1 (HAX1) is a class of multifunctional protein, participated in various physiological processes such as cell apoptosis, proliferation and motility. However, the HAX1 expression and function in the spinal cord injury (SCI) pathological process have not been investigated. In our current research, the rat model of SCI was established, and then we explored the possible role of HAX1 after SCI. The results of western blot indicated that HAX1 was present in sham operated control group and significantly elevated at 3 days post SCI, then declined gradually. Immunohistochemical studies indicated HAX1 expression was enhanced significantly in white and gray matter at 3 days post SCI compared with sham operated group. Double immunofluorescence staining showed the proportion of cells, double-labeled HAX1 and neurons, astrocytes, increased significantly at 3 days post SCI. In addition, co-localization of HAX1/active caspase-3 and HAX1/PCNA was tested in cells. Furthermore, over-expression of HAX1 inhibited neuronal apoptosis in vitro, and in astrocytes HAX1 silencing could down-regulate PCNA expression post LPS treatment. Meanwhile, CCK8 assay showed that knockdown of HAX1 could inhibit the astrocyte proliferation. In summary, our data indicated that HAX1 might play significant roles in pathological process of neuronal apoptosis and astrocyte proliferation during SCI.

Silencing of α-complex protein-2 reverses alcohol- and cytokine-induced fibrogenesis in hepatic stellate cells

BACKGROUND AND AIM

α-complex protein-2 (αCP2) encoded by the poly (rC) binding protein 2(PCBP2) gene is responsible for the accumulation of type I collagen in fibrotic livers. In this study, we silenced the PCBP2 gene using a small interfering RNA (siRNA) to reverse alcohol-and cytokine-induced profibrogenic effects on hepatic stellate cells (HSCs).

METHODS

Primary rat HSCs and the HSC-T6 cell line were used as fibrogenic models to mimic the initiation and perpetuation stages of fibrogenesis, respectively. We previously found that a PCBP2 siRNA, which efficiently silences expression of αCP2, reduces the stability of type I collagen mRNA. We investigated the effects of the PCBP2 siRNA on cell proliferation and migration. Expression of type I collagen in HSCs was analyzed by quantitative real-time PCR and western blotting. In addition, we evaluated the effects of the PCBP2 siRNA on apoptosis and the cell cycle.

RESULTS

PCBP2 siRNA reversed multiple alcohol- and cytokine-induced profibrogenic effects on primary rat HSCs and HSC-T6 cells. The PCBP2 siRNA also reversed alcohol- and cytokine-induced accumulation of type I collagen as well as cell proliferation and migration. Moreover, the combination of LY2109761, a transforming growth factor-β1 inhibitor, and the PCBP2 siRNA exerted a synergistic inhibitive effect on the accumulation of type I collagen in HSCs.

CONCLUSIONS

Silencing of PCBP2 using siRNA could be a potential therapeutic strategy for alcoholic liver fibrosis.