Project description:Neuregulin-1 (NRG1) is a paracrine growth factor, secreted by cardiac endothelial cells (Ecs) in conditions of cardiac overload/injury. The current concept is that the cardiac effects of NRG1 are mediated by activation of ERBB4/ERBB2 receptors on cardiomyocytes. However, recent studies have shown that paracrine effects of NRG1 on fibroblasts and macrophages are equally important. Here, we hypothesize that NRG1 autocrine signaling plays a role in cardiac remodeling. We generated EC–specific Erbb4 knockout mice to eliminate endothelial autocrine ERBB4 signaling without affecting paracrine NRG1/ERBB4 signaling in the heart. We first observed no basal cardiac phenotype in these mice up to 32 weeks. We next studied these mice following transverse aortic constriction (TAC), exposure to angiotensin II (Ang II) or myocardial infarction in terms of cardiac performance, myocardial hypertrophy, myocardial fibrosis and capillary density. In general, no major differences between EC–specific Erbb4 knockout mice and control littermates were observed. However, 8 weeks following TAC both myocardial hypertrophy and fibrosis were attenuated by EC–specific Erbb4 deletion, albeit these responses were normalized after 20 weeks. Similarly, 4 weeks after Ang II treatment myocardial fibrosis was less pronounced compared to control littermates. These observations were supported by RNA-sequencing experiments on cultured endothelial cells showing that NRG1 controls the expression of various hypertrophic and fibrotic pathways. Overall, this study shows a role of endothelial autocrine NRG1/ERBB4 signaling in the modulation of hypertrophic and fibrotic responses during early cardiac remodeling. This study contributes to understanding the spatio-temporal heterogeneity of myocardial autocrine and paracrine responses following cardiac injury.
Project description:The ketogenic diet (KD) has been used as an effective therapy to treat epilepsy. Previous studies indicate an elevated level of GABA in the brain by KD treatment. However, the underlying mechanisms remain to be elucidated. Here we report that KD treatment suppresses seizures in both acute and chronic seizure models and enhances presynaptic GABA release probability in the hippocampus. By screening molecular targets that potentially linked to GABAergic activity with transcriptome analysis, we identify that KD treatment dramatically increased the Nrg1 gene expression in the hippocampus. Disruption of Nrg1 signaling by genetically deleting its receptor-ErbB4 or blocking ErbB4 kinase activity abolishes KD’s effects on GABAergic activity and seizures. Mechanistically, KD treatment increases Nrg1 expression via up-regulating histone acetylation. Our findings suggest a critical role of Nrg1/ErbB4 signaling in mediating KD’s effects on GABAergic activity and seizures, which sheds light on the development of new therapeutic interventions to seizure control.
Project description:The four members of the epidermal growth factor receptor (EGFR/ERBB) family form homo- and heterodimers which mediate ligand-specific regulation of many key cellular processes in normal and cancer tissues. While signaling through the EGFR has been extensively studied on the molecular level, signal transduction through ERBB3/ERBB4 heterodimers is less well understood. Here, we generated isogenic mouse Ba/F3 cells that express full-length and functional membrane-integrated ERBB3 and ERBB4 or ERBB4 alone, to serve as a defined cellular model for biological and phosphoproteomics analysis of ERBB3/ERBB4 signaling. ERBB3 co-expression significantly enhanced Ba/F3 cell proliferation upon neuregulin-1 (NRG1) treatment. For comprehensive signaling studies we performed quantitative mass spectrometry (MS) experiments to compare the basal ERBB3/ERBB4 cell phosphoproteome to NRG1 treatment of ERBB3/ERBB4 and ERBB4 cells. We employed a workflow comprising differential isotope labeling with mTRAQ reagents followed by chromatographic peptide separation and final phosphopeptide enrichment prior to MS analysis. Overall, we identified 9686 phosphorylation sites which could be confidently localized to specific residues. Statistical analysis of three replicate experiments revealed 492 phosphorylation sites which were significantly changed in NRG1-treated ERBB3/ERBB4 cells. Bioinformatics data analysis recapitulated regulation of mitogen-activated protein kinase and Akt pathways, but also indicated signaling links to cytoskeletal functions and nuclear biology. Comparative assessment of NRG1-stimulated ERBB4 Ba/F3 cells indicated that ERBB3 did not trigger defined signaling pathways but more broadly enhanced phosphoproteome regulation in cells expressing both receptors. In conclusion, our data provide the first global picture of ERBB3/ERBB4 signaling and provide numerous potential starting points for further mechanistic studies
Project description:Convergent and divergent effects of two FL ERBB4 isoforms on gene expression in normal-like MCF10A mammary epithelial cells lacking endogeneous ERBB4 expression. Control vector (VEC) and ERBB4 expression MCF10A cells(CYT1 or CYT2) were serum starved for 48 hours and incubated with or without ERBB4 ligand NRG1 for 2h. RNA samples were collected and analyzed.
Project description:Hyperglycemia is a risk factor for breast cancer-related morbidity and mortality. Hyperglycemia induces Neuregulin 1 (Nrg1) overexpression in breast cancer, which subsequently promotes tumor progression. However, molecular mechanisms underlying hyperglycemia-induced Nrg1 overexpression remain poorly understood. Here, We used DNA-protein pull-down using Nrg1 enhancer sequence as bait followed by LC/MS and identified RBPJ as a key component of the Nrg1 enhanceosome. We show that hyperglycemia causes active histone modifications at the Nrg1 enhancer, forming enhanceosome complexes where RBPJ, P300, and SETD1A are recruited to upregulate Nrg1 expression.
Project description:ERBB4 is a member of the epidermal growth factor receptor (EGFR)/ERBB subfamily of receptor tyrosine kinases that regulates cellular processes including proliferation, migration and survival. ERBB4 signaling is involved in embryogenesis and homeostasis of adult tissues, but also in human pathologies such as cancer, neurological disorders and cardiovascular diseases. A mass spectrometry screen revealed guanine nucleotide exchange factor (GEF) VAV3, an activator of Rho family GTPases, as a novel ERBB4-interacting protein in breast cancer cells. The ERBB4-VAV3-interaction was confirmed by targeted mass-spectrometry, coimmunoprecipitation experiments, and further defined by demonstrating that kinase activity and tyrosine residues 1022 and 1162 of ERBB4, as well as the intact phosphotyrosine-interacting SH2 domain of VAV3 were necessary for the interaction. ERBB4 was also shown to stimulate tyrosine phosphorylation of the VAV3 activation domain, which is required for GEF activity of VAV proteins. In addition to VAV3, also the other members of the VAV family, VAV1 and VAV2 were shown to coprecipitate with ERBB4. Analyses of the effects of overexpression of dominant-negative VAV3 constructs or downregulation of VAV3 expression by shRNAs in breast cancer cells demonstrated that active VAV3 was involved in ERBB4-stimulated migration. These findings define the VAV GTPases as novel effectors of ERBB4 activity in a signaling pathway relevant for cancer cell migration.
Project description:The Cryptococcus neoformans NRG1 gene was identified using gene microarrays to define putative transcription factor genes regulated by the cyclic AMP (cAMP) signal transduction pathway. Disruption of NRG1 results in delayed capsule formation and mating, two phenotypes that are directly controlled by cAMP signaling. Putative targets of the Nrg1 transcription factor were identified using a second genome microarray to define differences in the transcriptomes of the wild-type and nrg1 mutant strains. These experiments implicate Nrg1 in the transcriptional control of multiple genes involved in carbohydrate metabolism and substrate oxidation, as well as the UGD1 gene encoding a UDP-glucose dehydrogenase required for polysaccharide capsule production and cell wall integrity. In addition to being under transcriptional control of the cAMP pathway, Nrg1 contains a putative protein kinase A phosphorylation site; mutation of this motif results in reduced Nrg1 activity. Consistent with prior studies in hypocapsular mutants, the nrg1 mutant strain is attenuated in an animal model of disseminated cryptococcal disease.