Erbin: an important therapeutic target for blocking tumor metastasis.

Erbin is an adapter protein that interacts with the v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2 (ERBB2) in epithelial cells. Erbin plays an important role in various signaling pathways, including cell proliferation, apoptosis, and autophagy. Additionally, Erbin is implicated in the pathogenesis and progression of sepsis and various cancers, including breast cancer, acute myeloid leukemia (AML), hepatocellular carcinoma (HCC), and colorectal cancer (CRC). A recent study shows that loss of Erbin increases the release of acyl-carnitine (Acar) through abolishing interaction with prothrombotic protein endothelial cell-specific adhesion molecule (ESAM), promotes mitochondrial oxidative phosphorylation in B cells, and ultimately suppresses lung metastasis of CRC. Accordingly, Erbin provides us with a new potential treatment for tumor metastasis.

Erbin alleviates sepsis-induced cardiomyopathy by inhibiting RIPK1-dependent necroptosis through activating PKA/CREB pathway.

Sepsis is a systemic inflammatory disease that can cause multiple organ damage. Septic patients with cardiac dysfunction have a significantly higher mortality. Based on the results of bioinformatics analysis, weighted gene co-expression network analysis (WGCNA), we found that Erbin is vital in cardiomyocyte. However, the function of Erbin in sepsis-induced cardiomyopathy (SIC) has not been explicitly studied. We discussed the role of Erbin in SIC by employing the Erbin-/- mice and HL-1 cardiomyocyte. An in vitro model of inflammation in HL-1 was used to confirm stimulation with lipopolysaccharide (LPS) and a mouse model of cecal ligation and puncture (CLP) to study the molecular mechanisms under SIC. Transmission electron microscopy (TEM) was used to characterize the morphological characteristics at the ultrastructural level. The expressions of Erbin, p-RIPK1, RIPK1, p-RIPK3, RIPK3, p-MLKL, MLKL, p-PKA, PKA, p-CREB and CREB were detected by western blot. qPCR analysis was applied to detect TNF-α, IL-1ß, IL-6, RIPK1 and MLKL mRNA expression. Cell survival was detected by CCK-8 assay and the levels of c TnI concentration were detected by ELISA kit. Our study revealed that necroptosis and inflammation were activated in cardiomyocytes during sepsis and deficiency of Erbin aggravated them. Furthermore, deficiency of Erbin exacerbated systolic dysfunction including the decline of LVEF and LVFS induced by CLP. Overexpression of Erbin alleviated necroptosis and inflammation by activating PKA/CREB pathway. Our research elucidates a noval mechanism whereby Erbin participates in SIC, providing a promising therapeutic target for myocardial dysfunction during sepsis.

CRISPR-Cas9 library screening combined with an exosome-targeted delivery system addresses tumorigenesis/TMZ resistance in the mesenchymal subtype of glioblastoma.

Rationale: The large-scale genomic analysis classifies glioblastoma (GBM) into three major subtypes, including classical (CL), proneural (PN), and mesenchymal (MES) subtypes. Each of these subtypes exhibits a varying degree of sensitivity to the temozolomide (TMZ) treatment, while the prognosis corresponds to the molecular and genetic characteristics of the tumor cell type. Tumors with MES features are predominantly characterized by the NF1 deletion/alteration, leading to sustained activation of the RAS and PI3K-AKT signaling pathways in GBM and tend to acquire drug resistance, resulting in the worst prognosis compared to other subtypes (PN and CL). Here, we used the CRISPR/Cas9 library screening technique to detect TMZ-related gene targets that might play roles in acquiring drug resistance, using overexpressed KRAS-G12C mutant GBM cell lines. The study identified a key therapeutic strategy to address the chemoresistance against the MES subtype of GBM. Methods: The CRISPR-Cas9 library screening was used to discover genes associated with TMZ resistance in the U87-KRAS (U87-MG which is overexpressed KRAS-G12C mutant) cells. The patient-derived GBM primary cell line TBD0220 was used for experimental validations in vivo and in vitro. Chromatin isolation by RNA purification (ChIRP) and chromatin immunoprecipitation (ChIP) assays were used to elucidate the silencing mechanism of tumor suppressor genes in the MES-GBM subtype. The small-molecule inhibitor EPIC-0412 was obtained through high-throughput screening. Transmission electron microscopy (TEM) was used to characterize the exosomes (Exos) secreted by GBM cells after TMZ treatment. Blood-derived Exos-based targeted delivery of siRNA, TMZ, and EPIC-0412 was optimized to tailor personalized therapy in vivo. Results: Using the genome-wide CRISPR-Cas9 library screening, we found that the ERBIN gene could be epigenetically regulated in the U87-KRAS cells. ERBIN overexpression inhibited the RAS signaling and downstream proliferation and invasion effects of GBM tumor cells. EPIC-0412 treatment inhibited tumor proliferation and EMT progression by upregulating the ERBIN expression both in vitro and in vivo. Genome-wide CRISPR-Cas9 screening also identified RASGRP1(Ras guanine nucleotide-releasing protein 1) and VPS28(Vacuolar protein sorting-associated protein 28) genes as synthetically lethal in response to TMZ treatment in the U87-KRAS cells. We found that RASGRP1 activated the RAS-mediated DDR pathway by promoting the RAS-GTP transformation. VPS28 promoted the Exos secretion and decreased intracellular TMZ concentration in GBM cells. The targeted Exos delivery system encapsulating drugs and siRNAs together showed a powerful therapeutic effect against GBM in vivo. Conclusions: We demonstrate a new mechanism by which ERBIN is epigenetically silenced by the RAS signaling in the MES subtype of GBM. Restoration of the ERBIN expression with EPIC-0412 significantly inhibits the RAS signaling downstream. RASGRP1 and VPS28 genes are associated with the promotion of TMZ resistance through RAS-GDP to RAS-GTP transformation and TMZ efflux, as well. A quadruple combination therapy based on a targeted Exos delivery system demonstrated significantly reduced tumor burden in vivo. Therefore, our study provides new insights and therapeutic approaches for regulating tumor progression and TMZ resistance in the MES-GBM subtype.

Role of Erbin in liver tissues in blood coagulation of septic mice / 中华麻醉学杂志

Objective:To evaluate the role of ERBB2 interacting protein (Erbin)in liver tissues in blood coagulation of septic mice.Methods:Thirty SPF healthy male C57BL/6 mice and 30 Erbin knockout mice, aged 8-10 weeks, weighing 20-30 g, were divided into wild-type+ sham operation group (WT+ Sham group), wild-type+ sepsis group (WT+ SEP group), Erbin gene knockout+ sham operation group (EKO+ Sham group) and Erbin gene knockout+ sepsis group (EKO+ SEP group) by a random number table method, with 15 animals in each group. The mouse sepsis model was prepared by the cecal ligation and perforation method in anesthetized animals. Eye blood samples were collected at 24 h after surgery and liver tissues were obtained for microscopic examination of histopathological changes (by HE staining) which were scored and for determination of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities (by colorimetry), expression of Erbin and tissue factor (TF) (by Western blot), expression of tissue plasminogen activator (t-PA) and fibrinogen (Fib)mRNA (by quantitative polymerase chain reaction), concentrations of PT, APTT, thrombin time (TT) and Fib (by automatic coagulation analyzer), and plasma TF and interleukin-6 (IL-6) concentrations (by enzyme-linked immunosorbent assay).Results:Compared with WT+ Sham group, the lung injury score was significantly increased, the expression of TF, t-PA mRNA and FGA mRNA was up-regulated, PT, APTT and TT were prolonged, the plasma Fib concentration was increased, and the activities of ALT and AST and concentrations of TF and IL-6 in plasma were increased in WT+ SEP group ( P<0.05). Compared with WT+ SEP group, the lung injury score was significantly increased, the expression of TF, t-PA mRNA and FGA mRNA was up-regulated, PT, APTT and TT were prolonged, the plasma Fib concentration was increased, and the activities of ALT and AST and concentrations of TF and IL-6 in plasma were increased in EKO+ SEP group ( P<0.05). Conclusions:Erbin in liver tissues exerts an endogenous protective effect on blood coagulation by inhibiting the up-regulation of TF expression in septic mice.

Erbin accelerates TFEB-mediated lysosome biogenesis and autophagy and alleviates sepsis-induced inflammatory responses and organ injuries.

Mounting attention has been focused on defects of the autophagy-lysosomal pathway in sepsis, however, the precise mechanisms governing the autophagy-lysosomal process in sepsis are poorly known. We have previously reported that Erbin deficiency aggravated the inflammatory response and organ injuries caused by sepsis. In the present study, we found that Erbin knockout impaired the autophagy process in both muramyl dipeptide (MDP)-induced bone marrow-derived macrophages (BMDMs) and sepsis mouse liver and lung, as detected by the accumulation of LC3-II and SQSTM1/p62, and autophagosomes. Pretreatment with autophagy inhibitor chloroquine (CQ) further aggravated inflammatory response and organ injuries in vivo and in vitro sepsis model. We also observed that the impaired lysosomal function mediated autophagic blockade, as detected by the decreased expression of ATP6V, cathepsin B (CTSB) and LAMP2 protein. Immunoprecipitation revealed that the C-terminal of Erbin (aa 391-964) interacts with the N-terminal of transcription factor EB (TFEB) (aa 1-247), and affects the stability of TFEB-14-3-3 and TFEB-PPP3CB complexes and the phosphorylation status of TFEB, thereby promote the nucleus translocation of TFEB and the TFEB target genes transcription. Thus, our study suggested that Erbin alleviated sepsis-induced inflammatory responses and organ injuries by rescuing dysfunction of the autophagy-lysosomal pathway through TFEB-14-3-3 and TFEB-PPP3CB pathway.

Knockout of Erbin promotes pyroptosis via regulating NLRP3/caspase-1/Gasdermin D pathway in sepsis-induced acute kidney injury.

BACKGROUND: This study aims to investigate the correlation between Erbin and sepsis, and the role of Erbin on the pyroptosis pathway in acute kidney injury caused by sepsis and NLRP3/caspase-1/Gasdermin D pathway. METHODS: In the study, lipopolysaccharide (LPS) treatment or cecal ligation and puncture (CLP) surgery on mice were used to stimulate the in vitro and in vivo sepsis-induced renal injury model. The male C57BL/6 of wild-type mice (WT) and Erbin-knockout mice (Erbin-/-, EKO) were randomly divided into four groups (WT + Sham, WT + CLP, EKO + Sham, EKO + CLP). Inflammatory cytokine, renal function, pyroptotic cell numbers and the levels of protein and mRNA expression of pyroptosis, including the NLRP3 (all P < 0.05), were analyzed and found increase in Erbin-/- mice with CLP and LPS-induced HK-2 cells. RESULTS: The inhibited of Erbin shows a renal damaged effect by promoting NLRP3 inflammasome-mediated pyroptosis in SI-AKI. CONCLUSION: This study demonstrated a novel mechanism by which Erbin regulates NLRP3 inflammasome-mediated pyroptosis in SI-AKI.

Erbin protects against sepsis-associated encephalopathy by attenuating microglia pyroptosis via IRE1α/Xbp1s-Ca2+ axis.

BACKGROUND: Microglia pyroptosis-mediated neuroinflammation is thought to be the crucial pathogenesis of sepsis-associated encephalopathy (SAE). Erbin has been reported to be associated with various inflammatory diseases. However, the role of Erbin in SAE and the relationship between Erbin and microglia pyroptosis are unknown. In this study, we investigated the promising role and underlying molecular mechanism of Erbin in the regulation of microglia pyroptosis. METHODS: WT and Erbin knockout mice underwent cecum ligation perforation (CLP) to induce SAE. Primary mouse microglia and BV2 cells were treated with LPS/nigericin in vitro. Behavioral tests were performed to evaluate cognitive function. Nissl staining and transmission electron microscopy were used to assess histological and structural lesions. ELISA and qPCR were carried out to detect neuroinflammation. Western blot and immunofluorescence were used to analyze protein expression. Flow cytometry and confocal microscopy were utilized to observe the Ca2+ changes in the cytoplasm and endoplasmic reticulum (ER). To further explore the underlying mechanism, STF083010 was administered to block the IRE1α/Xbp1s pathway. RESULTS: Erbin deletion resulted in more pronounced neuronal damage and cognitive impairment in mice that underwent CLP. Erbin knockout promoted microglial pyroptosis and inflammatory cytokines secretion in vivo and in vitro, which was mediated by activation of the IRE1α/Xbp1s. Treatment with the selective inhibitor STF083010 significantly inhibited IRE1α/Xbp1s pathway activity, decreased intracytoplasmic Ca2+, attenuated microglial pyroptosis, reduced pro-inflammatory cytokine secretion, lessened neuronal damage, and improved cognitive function. CONCLUSIONS: In SAE, Erbin inhibits IRE1/Xbp1s pathway activity and reduces the ER Ca2+ influx to the cytoplasm, reducing microglial pyroptosis.

Relationship between Erbin and Bax/Bcl-xL-mediated cell apoptosis during sepsis-induced acute kidney injury in mice / 中华麻醉学杂志

Objective:To evaluate the relationship between Erbin and Bax/Bcl-xL-mediated cell apoptosis during sepsis-induced acute kidney injury in mice.Methods:Thirty-two SPF male wild type C57BL/6 mice, 32 SPF male Erbin (-/-) C57BL/6 mice, aged 6-8 weeks, weighing 20-30 g, were divided into 2 groups ( n=16 each) using the random number table method: wild type sham operation group (WT+ Sham group), wild type sepsis group (WT+ S group), Erbin(-/-) sham operation group (EKO+ Sham group), and Erbin(-/-) sepsis group (EKO+ S group). The sepsis model was established using the moderate cecal ligation and puncture (CLP) in anesthetized animals.The survival rates within 7 days after CLP were recorded.The serum concentrations of tumor necrosis factor-alpha (TNF-α), interleukin-10 (IL-10), IL-1β, creatinine (Cr), blood urea nitrogen (BUN) and lactic dehydrogenase (LDH) were determined at 24 h after CLP.Then the renal tissues were taken for assessment of renal injury which was scored and for determination of the apoptosis rate (by TUNEL) and expression of cleaved-caspase-3, Bcl-xL and Bax (by Western blot). Results:Compared with sham operation groups, the survival rates were significantly decreased, the serum concentrations of IL-1β, IL-10, TNF-α, Cr, BUN and LDH, renal injury score and apoptosis rate were increased, the expression of Bax and cleaved-caspase-3 was up-regulated, and the expression of Bcl-xL was down-regulated in sepsis groups ( P<0.05). Compared with WT+ S group, the survival rates were significantly decreased, the serum concentrations of IL-1β, LDH, TNF-α, Cr and BUN and renal injury score were increased, the serum concentration of IL-10 was decreased, the apoptosis rate of renal tissues was increased, the expression of Bax and cleaved-caspase-3 was up-regulated, and the expression of Bcl-xL was down-regulated in EKO+ S group ( P<0.05). Conclusions:Erbin can inhibit Bax/Bcl-xL-mediated cell apoptosis and is involved in endogenous protective mechanism against sepsis-induced acute kidney injury in mice.

Effect of PDZD2 protein regulated by ERBIN expression on proliferation， invasion and apoptosis of colorectal cancer cells / 安徽医科大学学报

Objective @#To investigate the expression and clinical significance of erbb2 interacting protein (ERBIN) and PDZ domain containing 2 protein (PDZD2) in colorectal cancer tissues，as well as the effects of ERBIN and PDZD2 on the progression of colorectal cancer and the corresponding mechanisms．@*Methods @#Western blot was used to detect the expression of ERBIN and PDZD2 proteins in tumor tissues and corresponding adjacent tissues from 86 colorectal cancer patients，as well as normal human colon fibroblasts ( CCD-18Co) and human colorectal cancer cell lines ( SW480 ，HCT116 ，SW620 and HT29 ) ; SW620 and HCT116 cells were transfected with ERBIN or PDZD2 overexpression vector，and then cell proliferation，cell invasion and apoptosis were detected．The expres- sion of ERBIN or PDZD2 protein in SW620 cell was observed by immunofluorescence chemistry．Co-immunoprecip- itation assay was used to detect the interaction between ERBIN and PDZD2 proteins.@*Results @#The expression levels of ERBIN and PDZD2 proteins in colorectal cancer tissues were lower than those in adjacent tissues (P＜0．01) ， and the expression levels of ERBIN and PDZD2 in colorectal cancer cells were lower than those in CCD-18Co cells (P＜0. 01) ．The expression levels of ERBIN and PDZD2 proteins were correlated with the depth of invasion，dif- ferentiation，TNM staging and lymph node metastasis of colorectal cancer (P＜0. 001) ; ERBIN or PDZD2 overex- pression reduced the proliferation and invasion of SW620 and HCT116 cells (P＜0. 01) ，increased cell apoptosis (P ＜0. 01 ) ; ERBIN directly bound to PDZD2 ，and overexpression of ERBIN increased the expression level of PDZD2 protein．@*Conclusion @#ERBIN can inhibit the proliferation and invasion of colorectal cancer cells and pro- mote apoptosis by promoting the expression of PDZD2 protein.

RASGRF2 gene fusions identified in a variety of melanocytic lesions with distinct morphological features.

The WHO classification identifies nine classes of melanocytic proliferations according to location, UV exposure, histological, and genetic features. Only a minority of lesions remain unclassified. We describe five cases that harbored either an ERBIN-RASGRF2 or an ATP2B4-RASGRF2 in-frame fusion transcript. These lesions were collected from different studies, unified only by the lack of identifiable known mutations, with a highly variable phenotype. One case was a large abdominal congenital nevus, three were slowly growing pigmented nodules, and the last was an ulcerated nodule arising on the site of a preexisting small nevus, known since childhood. The latter was diagnosed as a 4 mm thick melanoma with loss of BAP1 expression. The four other cases were compound, melanocytic proliferations with an unusual deep pattern of small dense nests of bland melanocytes encased in a fibrous background. The RASGRF2 fusion was confirmed by a break-apart FISH technique. Array CGH performed in three cases found non-recurrent secondary copy number alterations. Follow-up was uneventful. In silico analysis identified a single RASGRF2 fusion in the TCGA pan-cancer database, whereas RASGRF2 variants were stochastically distributed in all cancer subtypes.

The leucine-rich repeat signaling scaffolds Shoc2 and Erbin: cellular mechanism and role in disease.

Leucine-rich repeat-containing proteins (LRR proteins) are involved in supporting a large number of cellular functions. In this review, we summarize recent advancements in understanding functions of the LRR proteins as signaling scaffolds. In particular, we explore what we have learned about the mechanisms of action of the LRR scaffolds Shoc2 and Erbin and their roles in normal development and disease. We discuss Shoc2 and Erbin in the context of their multiple known interacting partners in various cellular processes and summarize often unexpected functions of these proteins through analysis of their roles in human pathologies. We also review these LRR scaffold proteins as promising therapeutic targets and biomarkers with potential application across various pathologies.

Erbin in Amygdala Parvalbumin-Positive Neurons Modulates Anxiety-like Behaviors.

BACKGROUND: Anxiety disorders are the most common psychiatric diseases, affecting 28% of people worldwide within their lifetime. The excitation-inhibition imbalance in the amygdala is thought to be an underlying pathological mechanism; however, the cellular and molecular control of amygdala excitation-inhibition balance is largely unknown. METHODS: By using mice expressing chemogenetic activator or inhibitor channel in amygdala parvalbumin (PV) neurons, Erbin mutant mice, and mice with Erbin specifically knocked down in amygdala PV neurons, we systematically investigated the role of amygdala PV neurons and Erbin expressed therein in the pathogenesis of anxiety disorders using the combined approaches of immunohistochemistry, electrophysiology, and behavior. RESULTS: In naïve mice, chemogenetic inhibition of PV neurons produced anxiogenic effects, suggesting an essential role in the regulation of anxiety. In stressed mice with anxiety, excitatory postsynaptic responses on amygdala PV neurons were selectively diminished, accompanied by a decreased expression of Erbin specifically in amygdala PV neurons. Remarkably, both Erbin mutant mice and amygdala PV-specific Erbin knockdown mice exhibited impaired excitatory postsynaptic responses on amygdala PV neurons and increased anxiety-like behaviors. Furthermore, chemogenetic activation of amygdala PV neurons normalized anxiety behaviors in amygdala PV-specific Erbin knockdown mice and stressed mice. CONCLUSIONS: Together, these results demonstrate that Erbin in PV neurons is critical for maintaining the excitation-inhibition balance in the amygdala and reveal a novel pathophysiological mechanism for anxiety disorders.

Therapeutic effects of Erbin inhibitor on spinal cord contusion in mice.

Erbin has been shown to maintain the integrity of cell structure, regulate the proliferation and differentiation of cell and transconduct signals in the pathways. This study was conducted to assess the therapeutic effects of an Erbin inhibitor on spinal cord contusion in mice. Spinal contusion models of mouse were constructed and treated with an Erbin inhibitor. The experimental animals were divided into control (normal animal without any treatment), models with spinal cord injury (SIM), and models receiving Erbin inhibitor (Inhibitor). The contents of 5-hydroxytryptamine (5-HT) and reactive oxygen species (ROS) in the brain and spinal cord tissues were measured using ELISA. The expression of ERK1/2, MAPK, NF-kB and NRG1 was quantified using qRT-PCR, Western blot analysis and immunohistochemistry. Flow cytometry was used to determine the formation of macrophages. Erbin interference vector was constructed and its interference effect on the expression of these genes was characterized in cultured bone marrow cells. Spinal contusion models were successfully constructed. Administering Erbin inhibitor inhibited the expression of ERK1/2, MAPK and NF-kB and up-regulated the expression of NRG1. Flow cytometry showed that Erbin inhibitor induced the formation of a large number of macrophages, which are beneficial to the recovery of spinal cord injury. Experiments with Erbin interference vector showed similar impacts on the expression of genes at cellular level as the inhibitor did. Our work has demonstrated that the Erbin inhibitor is very effective to treat spinal cord contusion in mice. The possible mechanism of therapeutic effect is that the inhibitor suppresses the ERK1/2/MAPK and/or NF-kB/MAPK signal pathways and enhances the NRG1-ErbB signaling pathway by reducing the expression of Erbin, leading to the inhibition of apoptosis, promotion of proliferation and differentiation, and subsequent repair of the damaged spinal cord.

miR-183-5p Inhibits Occurrence and Progression of Acute Myeloid Leukemia via Targeting Erbin.

Erbin has been shown to have significant effects on the development of solid tumors. However, little is known about its function and regulatory mechanism in hematological malignancies. The biological function of Erbin on cell proliferation was measured in vitro and in vivo. The predicted target of Erbin was validated by dual-luciferase reporter assay and rescue experiment. We found that overexpression of Erbin could inhibit the cell proliferation and promote the cell differentiation of acute myeloid leukemia (AML) cells, whereas depletion of Erbin could enhance the cell proliferation and block the cell differentiation in AML cells in vitro and in vivo. Besides, miR-183-5p was identified as the upstream regulator that negatively regulated the Erbin expression. The results were confirmed by dual-luciferase reporter and RNA pull-down assay. Furthermore, we found that miR-183-5p negatively regulated Erbin, resulting in enhanced cell proliferation of AML cells via activation of RAS/RAF/MEK/ERK and PI3K/AKT/FoxO3a pathways. The activation of RAS/RAF/MEK/ERK and PI3K/AKT/FoxO3a pathways was mediated by Erbin interacting with Grb2. These results were also validated by rescue experiments in vitro and in vivo. All above-mentioned findings indicated that the miR-183-5p/Erbin signaling pathway might represent a novel prognostic biomarker or therapeutic target for treatment of AML.

Erbin plays a critical role in human umbilical vein endothelial cell migration and tubular structure formation via the Smad1/5 pathway.

Angiogenesis is an important process in atherosclerosis. ErbB2 was proved to have an important role in vascular development, but it is still unclear whether Erbin expresses in vessels as well as its location and function in the vessels. In the current study, we investigated the location and function of Erbin in human umbilical veins. The human umbilical veins were prepared, and immunofluorescent analysis was performed to determine the expression of Erbin. Human umbilical vein endothelial cells (HUVECs) were cultured and the lentivirus (LV) containing Erbin RNAi was also prepared. After transfection with the lentivirus, CCK-8 assay and Annexin V-PI assay were used for cell proliferation and apoptosis, respectively. Cell migration was studied using the scratch wound healing assay and the transwell assay. The capillary-like tube formation assay was performed to illustrate the effect of Erbin on HUVEC tube formation. Expression of signaling pathway molecules was assessed with Western blot. The immunofluorescent analysis suggested that Erbin expressed in human umbilical veins and the majority of the Erbin is strongly colocalized in endothelial cells. Although knockdown of Erbin did not affect HUVEC proliferation and apoptosis, it significantly suppressed HUVEC migration and tubular structure formation. Erbin knockdown showed no effect on the ERK1/2 and Smad2/3 signaling pathways but significantly promoted Smad1/5 phosphorylation and nuclear translocation. Ablation of the Smad1/5 pathway decreased the effects of Erbin on endothelial cells. Erbin is mainly localized in endothelial cells in human umbilical veins and plays a critical role in endothelial cell migration and tubular formation via the Smad1/5 pathway.

Expression of Erbin in esophageal squamous cell carcinoma and its relationship with patient prognosis / 中国肿瘤临床

To explore the significance of Erbin expression in esophageal squamous cell carcinoma (ESCC) and its relation-ship with patient prognosis. Methods: Erbin expression in a tissue chip containing samples from 299 cases were examined using immu-nohistochemistry; in addition, the relationship between Erbin expression and clinical-pathological parameters and patient survival time were also analyzed. Cox regression was used to predict the risk of clinical-pathological parameters. The mRNA and protein expres-sion of Erbin was also determined in 25 cases with paired ESCC and normal tissues through polymerase chain reaction (PCR) and West-ern blot. Results: The expression of Erbin protein and mRNA in ESCC were significantly higher than those of normal esophageal epithe-lium adjacent to cancer (55.2% vs. 0, P<0.05). The high expression of Erbin in ESCC was closely related to TNM stage (64.9% vs. 47.3%, P=0.002) and lymph node metastasis (65.5% vs. 45.0%, P<0.001). Moreover, the high expression of Erbin in ESCC was closely related to poor prognosis (P<0.05). Conclusions: Erbin expression was increased in ESCC and was closely related to poor patient prognosis, which suggested that Erbin may be an important biomarker for the prognosis of cancer patients.

Erbin exerts a protective effect against inflammatory bowel disease by suppressing autophagic cell death.

The pathogenesis and key functional molecules involved in inflammatory bowel disease (IBD) including Crohn's disease (CD) and ulcerative colitis (UC) remain unclear. Here, we reported that Erbin, a protein required for the polarity of epithelial cells, is conserved across species and highly expressed in the intestinal mucosa in mice and zebrafish. Pathologically, Erbin expression in the intestinal mucosa was significantly decreased in DSS induced acute colitis mice, IL-10 deficient mice and clinical biopsy specimens from patients with ulcerative colitis. Moreover, Erbin deficient mice are more susceptible to experimental colitis, exhibiting more severe intestinal barrier disruption, with increased histological scores and excessive production of proinflammatory cytokines. Mechanistically, Erbin deficiency or knockdown significantly exacerbated activation of autophagic program and autophagic cell death in vivo and in vitro. And, inhibition of autophagy by Chloroquine attenuates excessive inflammatory response in the DSS-induced colitis mouse model of Erbin deletion. Generally, our study uncovers a crucial role of Erbin in autophagic cell death and IBD, giving rise to a new strategy for IBD therapy by inhibiting excessive activation of autophagy and autophagic cell death.

LAP proteins are localized at the post-synaptic membrane of neuromuscular junctions and appear to modulate synaptic morphology and transmission.

Erbin, Lano, Scribble, and Densin-180 belong to LAP (leucine-rich repeats and PDZ domain) adaptor proteins involved in cell signaling pathways. Previously, we identified Erbin, Lano, and Scribble, but not Densin-180, in muscle cells, where they are involved in regulating the aggregation of nicotinic acetylcholine receptors in vitro. Here, we analyzed their cellular localization at the neuromuscular junction (NMJ) in skeletal muscles of mice. Erbin, Lano, and Scribble were significantly accumulated at NMJs and localized in different synaptic cells. Moreover, we used mouse mutants to analyze the role of Erbin at the NMJ. We used two Erbin mutant mouse strains that either completely lack Erbin protein (Erbinnull/null ) or express a truncated Erbin mutant where the carboxy-terminal PDZ domain is replaced by ß-galactosidase (ErbinΔC/ΔC ) thereby abolishing its interaction with ErbB receptor tyrosine kinases. Neither the lack of the PDZ domain of Erbin, nor its complete absence interfered with the general localization of LAP proteins at NMJs, but Lano and Scribble transcript levels were up-regulated in homozygous Erbin-null muscles. Furthermore, grip strength was reduced and neural transmission impaired in homozygous aged Erbin-null but not Erbin-ΔC mice. Erbin-null skeletal muscles did not reveal any conspicuous impairment of the muscle fiber. Localization of other NMJ marker proteins was not affected either. Quantitative 3D morphometry showed that NMJs of Erbin-null muscles were significantly smaller and fragmented in the soleus. We speculate that Erbin, Lano, and Scribble act at the post-synaptic membrane of NMJs in a concerted fashion to regulate nicotinic acetylcholine receptors cluster morphology and neural transmission. Cover Image for this issue: doi: 10.1111/jnc.13340.

Erbin loss promotes cancer cell proliferation through feedback activation of Akt-Skp2-p27 signaling.

Erbin localizes at the basolateral membrane to regulate cell junctions and polarity in epithelial cells. Dysregulation of Erbin has been implicated in tumorigenesis, and yet it is still unclear if and how disrupted Erbin regulates the biological behavior of cancer cells. We report here that depletion of Erbin leads to cancer cell excessive proliferation in vitro and in vivo. Erbin deficiency accelerates S-phase entry by down-regulating CDK inhibitors p21 and p27 via two independent mechanisms. Mechanistically, Erbin loss promotes p27 degradation by enhancing E3 ligase Skp2 activity though augmenting Akt signaling. Interestingly, we also show that Erbin is an unstable protein when the Akt-Skp2 signaling is aberrantly activated, which can be specifically destructed by SCF-Skp2 ligase. Erbin loss facilitates cell proliferation and migration in Skp2-dependent manner. Thus, our finding illustrates a novel negative feedback loop between Erbin and Akt-Skp2 signaling. It suggests disrupted Erbin links polarity loss, hyperproliferation and tumorigenesis.

FHL2 switches MITF from activator to repressor of Erbin expression during cardiac hypertrophy.

BACKGROUND: Congestive heart failure (CHF) is a significant health care burden in developed countries. However, the molecular events leading from cardiac hypertrophy to CHF are unclear and preventive therapeutic approaches are limited. We have previously described that microphthalmia-associated transcription factor (MITF) is a key regulator of cardiac hypertrophy, but its cardiac targets are still uncharacterized. METHODS AND RESULTS: Gene array analysis of hearts from MITF-mutated mice indicated that ErbB2 interacting protein (Erbin) is a candidate target gene for MITF. We have recently demonstrated that Erbin is decreased in human heart failure and plays a role as a negative modulator of pathological cardiac hypertrophy. Here we show that Erbin expression is regulated by MITF. Under basal conditions MITF activates Erbin expression by direct binding to its promoter. However, under ß-adrenergic stimulation Erbin expression is decreased only in wild type mice, but not in MITF-mutated mice. Yeast two-hybrid screening, using MITF as bait, identified an interaction with the cardiac-predominant four-and-a-half LIM domain protein 2 (FHL2), which was confirmed by co-immunoprecipitation in both mouse and human hearts. Upon ß-adrenergic stimulation, FHL2 and MITF bind Erbin promoter as a complex and repress MITF-directed Erbin expression. Overexpression of FHL2 alone had no effect on Erbin expression, but in the presence of MITF, Erbin expression was decreased. FHL2-MITF association was also increased in biopsies of heart failure patients. CONCLUSION: MITF unexpectedly regulates both the activation and the repression of Erbin expression. This ligand mediated fine tuning of its gene expression could be an important mechanism in the process of cardiac hypertrophy and heart failure.