Neuron-specific expression of p48 Ebp1 during murine brain development and its contribution to CNS axon regeneration

ErbB3 binding protein 1 contributes to adult hippocampal neurogenesis by modulating Bmp4 and Ascl1 signaling

Neural stem cells (NSCs) in the adult hippocampus divide infrequently; the endogenous molecules modulating adult hippocampal neurogenesis (AHN) remain largely unknown. Here, we show that ErbB3 binding protein 1 (Ebp1), which plays important roles in embryonic neurodevelopment, acts as an essential modulator of adult neurogenic factors. In vivo analysis of Ebp1 neuron depletion mice showed impaired AHN with a low number of hippocampal NSCs and neuroblasts. Ebp1 leads to transcriptional repression of Bmp4 and suppression of Ascl1 promoter methylation in the dentate gyrus of the adult hippocampus reflecting an unusually high level of Bmp4 and low Ascl1 level in neurons of Ebp1-deficient mice. Therefore, our findings suggests that Ebp1 could act as an endogenous modulator of the interplay between Bmp4 and Ascl1/Notch signaling, contributing to AHN. [BMB Reports 2024; 57(4): 182-187].

PA2G4/EBP1 ubiquitination by PRKN/PARKIN promotes mitophagy protecting neuron death in cerebral ischemia

Cerebral ischemia induces massive mitochondrial damage, leading to neuronal death. The elimination of damaged mitochondria via mitophagy is critical for neuroprotection. Here we show that the level of PA2G4/EBP1 (proliferation-associated 2G4) was notably increased early during transient middle cerebral artery occlusion and prevented neuronal death by eliciting cerebral ischemia-reperfusion (IR)-induced mitophagy. Neuron-specific knockout of Pa2g4 increased infarct volume and aggravated neuron loss with impaired mitophagy and was rescued by introduction of adeno-associated virus serotype 2 expressing PA2G4/EBP1. We determined that PA2G4/EBP1 is ubiquitinated on lysine 376 by PRKN/PARKIN on the damaged mitochondria and interacts with receptor protein SQSTM1/p62 for mitophagy induction. Thus, our study suggests that PA2G4/EBP1 ubiquitination following cerebral IR-injury promotes mitophagy induction, which may be implicated in neuroprotection.Abbreviations: AAV: adeno-associated virus; ACTB: actin beta; BNIP3L/NIX: BCL2 interacting protein 3 like; CA1: Cornu Ammonis 1; CASP3: caspase 3; CCCP: carbonyl cyanide m-chlorophenyl hydrazone; DMSO: dimethyl sulfoxide; PA2G4/EBP1: proliferation-associated 2G4; FUNDC1: FUN14 domain containing 1; IB: immunoblotting; ICC: immunocytochemistry; IHC: immunohistochemistry; IP: immunoprecipitation; MCAO: middle cerebral artery occlusion; MEF: mouse embryonic fibroblast; OGD: oxygen-glucose deprivation; PRKN/PARKIN: parkin RBR E3 ubiquitin protein ligase; PINK1: PTEN induced kinase 1; RBFOX3/NeuN: RNA binding fox-1 homolog 3; SQSTM1/p62: sequestosome 1; TIMM23: translocase of inner mitochondrial membrane 23; TOMM20: translocase of outer mitochondrial membrane 20; TUBB: tubulin beta class I; WT: wild-type.

Cerebellar dysfunction and schizophrenia-like behavior in Ebp1-deficient mice

Cerebellar deficits with Purkinje cell (PCs) loss are observed in several neurologic disorders. However, the underlying mechanisms as to how the cerebellum is affected during development remain unclear. Here we demonstrated that specific inactivation of murine Ebp1 in the central nervous system causes a profound neuropathology characterized by reduced cerebellar volume and PCs loss with abnormal dendritic development, leading to phenotypes including motor defects and schizophrenia (SZ)-like behaviors. Loss of Ebp1 leads to untimely gene expression of Fbxw7, an E3 ubiquitin ligase, resulting in aberrant protein degradation of PTF1A, thereby eliciting cerebellar defects. Reinstatement of Ebp1, but not the Ebp1-E183Ter mutant found in SZ patients, reconstituted cerebellar architecture with increased PCs numbers and improved behavioral phenotypes. Thus, our findings indicate a crucial role for EBP1 in cerebellar development, and define a molecular basis for the cerebellar contribution to neurologic disorders such as SZ.

ERBB3 binding protein 1 promotes the progression of malignant melanoma through activation of the Wnt/ β-catenin signaling pathway

Background

Malignant melanoma (MM) is highly metastatic and has the highest mortality rate in patients with skin cancer. The ERBB3 binding protein 1 (Ebp1) has been linked to the onset and progression of a number of malignancies. However, the role of Ebp1 in MM has not yet been reported.

Methods

Multiple databases were analyzed for comparing the expression of Ebp1 in normal skin and MM. Ebp1 expression was knocked down in A375 and B16 cells, and the impact of Ebp1 on the cell growth was tested by CCK-8, plate clone colony, and cell cycle assays. Scratch, transwell, and in vivo caudal vein lung metastasis tests were also used to confirm the effects of Ebp1 on melanoma cells migration, invasion, and metastasis. Furthermore, the possible molecular mechanism of Ebp1 was predicted by set enrichment analysis and verified by western blotting.

Results

Ebp1 expression was substantially higher in MM than it was in normal skin, and Ebp1 was linked to the clinical stage and lymph node metastases of patients with MM. Knockdown of Ebp1 inhibited cell proliferation, migration, and invasion. In vivo experiments further verified that the knockdown of Ebp1 had an obvious inhibitory effect on lung metastasis in nude mice. Knockdown of Ebp1 reduced vimentin, N-cadherin, slug, and snail expression while increasing E-cadherin expression. Furthermore, knockdown of Ebp1 reduced the expression of β-catenin, as well as its downstream targets CyclinD1 and p-GSK3β; however, a Wnt/β-catenin agonist could reverse this effect.

Conclusion

Ebp1 may promote the proliferation and metastasis of melanoma cells through activation of the Wnt/β-catenin pathway.

Graphical Abstract

EBP1 regulates Suv39H1 stability via the ubiquitin-proteasome system in neural development

ErbB3-binding protein 1 (EBP1) is a multifunctional protein associated with neural development. Loss of Ebp1 leads to upregulation of the gene silencing unit suppressor of variegation 3-9 homolog 1 (Suv39H1)/DNA (cytosine 5)-methyltransferase (DNMT1). EBP1 directly binds to the promoter region of DNMT1, repressing DNA methylation, and hence, promoting neural development. In the current study, we showed that EBP1 suppresses histone methyltransferase activity of Suv39H1 by promoting ubiquitin-proteasome system (UPS)-dependent degradation of Suv39H1. In addition, we showed that EBP1 directly interacts with Suv39H1, and this interaction is required for recruiting the E3 ligase MDM2 for Suv39H1 degradation. Thus, our findings suggest that EBP1 regulates UPS-dependent degradation of Suv39H1 to govern proper heterochromatin assembly during neural development.

Protein Synthesis in the Developing Neocortex at Near-Atomic Resolution Reveals Ebp1-Mediated Neuronal Proteostasis at the 60S Tunnel Exit

Protein synthesis must be finely tuned in the developing nervous system as the final essential step of gene expression. This study investigates the architecture of ribosomes from the neocortex during neurogenesis, revealing Ebp1 as a high-occupancy 60S peptide tunnel exit (TE) factor during protein synthesis at near-atomic resolution by cryoelectron microscopy (cryo-EM). Ribosome profiling demonstrated Ebp1-60S binding is highest during start codon initiation and N-terminal peptide elongation, regulating ribosome occupancy of these codons. Membrane-targeting domains emerging from the 60S tunnel, which recruit SRP/Sec61 to the shared binding site, displace Ebp1. Ebp1 is particularly abundant in the early-born neural stem cell (NSC) lineage and regulates neuronal morphology. Ebp1 especially impacts the synthesis of membrane-targeted cell adhesion molecules (CAMs), measured by pulsed stable isotope labeling by amino acids in cell culture (pSILAC)/bioorthogonal noncanonical amino acid tagging (BONCAT) mass spectrometry (MS). Therefore, Ebp1 is a central component of protein synthesis, and the ribosome TE is a focal point of gene expression control in the molecular specification of neuronal morphology during development.

The roles of multifunctional protein ErbB3 binding protein 1 (EBP1) isoforms from development to disease

The roles of the two isoforms of ErbB3-binding protein 1 (Ebp1) in cellular function and its regulation in disease and development is a stimulating area in current fields of biology, such as neuroscience, cancer biology, and structural biology. Over the last two decades, a growing body of studies suggests have suggested different functions for the EBP1 isoforms in various cancers, along with their specific binding partners in the ubiquitin-proteasome system. Owing to the specific cellular context or spatial/temporal expression of the EBP1 isoforms, either transcriptional repression or the activation function of EBP1 has been proposed, and epigenetic regulation by p48 EBP1 has also been observed during in the embryo development, including in brain development and neurologic disorders, such as schizophrenia, in using an Ebp1 knockout mouse model. Here, we review recent findings that have shaped our current understanding of the emerging function of EBP1 isoforms in cellular events and gene expression, from development to disease.

A pair of proteins that originate from a common gene exert strikingly different effects on embryonic development as well as tumor growth and progression. RNA transcripts generated from the PA2G4 gene can undergo enzymatic processing to yield two different protein products, p42 EB1 and p48 EB1. These proteins differ by the presence or absence of 54 amino acids at one end, and Jee-Yin Ahn at the Sungkyunkwan University School of Medicine, Suwon, South Korea, and colleagues have reviewed current insights into the functional consequences of this difference. The two proteins bind to distinct sets of molecular partners. The p48 form appears to regulate a host of genes involved in brain development, but also appears to drive cancerous growth in various tumors. In contrast, p42 is scarcer during development, and appears to inhibit tumor formation.

Dysregulation of Epigenetic Control Contributes to Schizophrenia-Like Behavior in Ebp1+/- Mice

Dysregulation of epigenetic machinery can cause a variety of neurological disorders associated with cognitive abnormalities. In the hippocampus of postmortem Schizophrenia (SZ) patients, the most notable finding is the deregulation of GAD67 along with differential regulation of epigenetic factors associated with glutamate decarboxylase 67 (GAD67) expression. As we previously reported, ErbB3-binding protein 1 (EBP1) is a potent epigenetic regulator. EBP1 can induce repression of Dnmt1, a well-studied transcriptional repressor of GAD67. In this study, we investigated whether EBP1 contributes to the regulation of GAD67 expression in the hippocampus, controlling epigenetic machinery. In accordance with SZ-like behaviors in Ebp1^(+/−) mice, heterozygous deletion of EBP1 led to a dramatic reduction of GAD67 expression, reflecting an abnormally high level of Dnmt1. Moreover, we found that EBP1 binds to the promoter region of HDAC1, which leads to histone deacetylation of GAD67, and suppresses histone deacetylase 1 (HDAC1) expression, inversely mirroring an unusually high level of HDAC1 in Ebp1^(+/−) mice. However, EBP1 mutant (p.Glu 183 Ter) found in SZ patients did not elevate the expression of GAD67, failing to suppress Dnmt1 and/or HDAC1 expression. Therefore, this data supports the hypothesis that a reduced amount of EBP1 may contribute to an etiology of SZ due to a loss of transcriptional inhibition of epigenetic repressors, leading to a decreased expression of GAD67.

Roles of ErbB3-binding protein 1 (EBP1) in embryonic development and gene-silencing control

ErbB3-binding protein 1 (EBP1) is implicated in diverse cellular functions, including apoptosis, cell proliferation, and differentiation. Here, by generating genetic inactivation of Ebp1 mice, we identified the physiological roles of EBP1 in vivo. Loss of Ebp1 in mice caused aberrant organogenesis, including brain malformation, and death between E13.5 and 15.5 owing to severe hemorrhages, with massive apoptosis and cessation of cell proliferation. Specific ablation of Ebp1 in neurons caused structural abnormalities of brain with neuron loss in [Nestin-Cre; Ebp1 ^flox/flox ] mice. Notably, global methylation increased with high levels of the gene-silencing unit Suv39H1/DNMT1 in Ebp1-deficient mice. EBP1 repressed the transcription of Dnmt1 by binding to its promoter region and interrupted DNMT1-mediated methylation at its target gene, Survivin promoter region. Reinstatement of EBP1 into embryo brain relived gene repression and rescued neuron death. Our findings uncover an essential role for EBP1 in embryonic development and implicate its function in transcriptional regulation.

Ebp1 regulates myogenic differentiation of myoblast cells via SMAD2/3 signaling pathway

Regulation of skeletal muscle development requires many of the regulatory networks that are fundamental to developmental myogenesis. ErbB3 binding protein-1 (Ebp1) is involved in the control of myoblasts development in chicken. However, the expression and biological functions of Ebp1 in the progress of myogenesis are unclear. This study focused on determining the effect of Ebp1 on myogenic proliferation and differentiation using a primary myoblasts culture model. Ebp1 was found to upregulate in proliferating myoblasts and decrease at the early stage of myogenic differentiation. The level of endogenous Ebp1 increased from E9 to E20 chicken leg muscles. Knockdown of Ebp1 had no effect on myoblasts proliferation. However, myogenic differentiation into multinucleated myotubes was significantly reduced. The mRNA and protein expression of MRFs was decreased when Ebp1 was knocked down. Downregulation of Ebp1, accompanied by elevated levels of pSMAD2/3, suggests that Ebp1 is involved in regulating myogenic differentiation via SMAD2/3 inhibition. The phosphorylation of SMAD2/3 was activated and the expression of MYOD and MYOG was reduced in Ebp1 knockdown myoblasts, but addition of LY2109761 (an inhibitor specified to SMAD2/3) blocked these effects. Collectively, these results indicate that Ebp1 promotes myoblast differentiation by inhibition of SMAD2/3 signaling pathway during chicken myogenesis. These data provide new insights into the biological role of Ebp1 in embryonic chicken skeletal muscle development.