ABSTRACT
Neuroglobin (NGB), an antiapoptotic protein upregulated by 17ß-estradiol (E2), is part of E2/estrogen receptor α (ERα) pathway pointed to preserve cancer cell survival in presence of microenvironmental stressors including chemotherapeutic drugs. Here, the possibility that resveratrol (Res), an anticancer plant polyphenol, could increase the susceptibility of breast cancer cells to paclitaxel (Pacl) by affecting E2/ERα/NGB pathway has been evaluated. In MCF-7 and T47D (ERα-positive), but not in MDA-MB 231 (ERα-negative) nor in SK-N-BE (ERα and ERß positive), Res decreases NGB levels interfering with E2/ERα-induced NGB upregulation and with E2-induced ERα and protein kinase B phosphorylation. Although Res treatment does not reduce cell viability by itself, this compound potentiates Pacl proapoptotic effects. Notably, the increase of NGB levels by NGB expression vector transfection prevents Pacl or Res/Pacl effects. Taken together, these findings indicate a new Res-based mechanism that acts on tumor cells impairing the E2/ERα/NGB signaling pathways and increasing cancer cell susceptibility to chemotherapeutic agent.
Subject(s)
Antineoplastic Combined Chemotherapy Protocols/pharmacology , Breast Neoplasms/drug therapy , Estradiol/pharmacology , Estrogen Receptor alpha/metabolism , Neuroglobin/metabolism , Paclitaxel/pharmacology , Resveratrol/pharmacology , Apoptosis/drug effects , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Drug Synergism , Estrogen Receptor alpha/genetics , Female , Gene Expression Regulation, Neoplastic , Humans , MCF-7 Cells , Neuroglobin/genetics , Phosphorylation , Proto-Oncogene Proteins c-akt/metabolism , Signal TransductionABSTRACT
Among several mechanisms underlying the well-known trophic and protective effects of 17ß-estradiol (E2) in the brain, we recently reported that E2 induces the up-regulation of two anti-apoptotic and neuroprotectant proteins: huntingtin (HTT) and neuroglobin (NGB). Here, we investigate the role of this up-regulation. The obtained results indicate that E2 promotes NGB-HTT association, induces the localization of the complex at the mitochondria, and protects SK-N-BE neuroblastoma cells and murine striatal cells, which express wild-type HTT (i.e., polyQ7), against H2O2-induced apoptosis. All E2 effects were completely abolished in HTT-knocked out SK-N-BE cells and in striatal neurons expressing the mutated form of HTT (mHTT; i.e., polyQ111) typical of Huntington's disease (HD). As a whole, these data provide a new function of wild-type HTT which drives E2-induced NGB in mitochondria modulating NGB anti-apoptotic activity. This new function is lost by HTT polyQ pathological expansion. These data evidence the existence of a novel E2/HTT/NGB neuroprotective axis that may play a relevant role in the development of HD therapeutics.
Subject(s)
Cell Survival/genetics , Estradiol/pharmacology , Globins/metabolism , Huntingtin Protein/genetics , Mutation , Nerve Tissue Proteins/metabolism , Neurons/metabolism , Peptides/genetics , Signal Transduction/genetics , Animals , Cell Line, Tumor , Cell Survival/drug effects , Corpus Striatum/cytology , Corpus Striatum/drug effects , Corpus Striatum/metabolism , Hippocampus/cytology , Hippocampus/drug effects , Hippocampus/metabolism , Mice , Mice, Transgenic , Neuroglobin , Neurons/cytology , Neurons/drug effects , Neuroprotection/drug effects , Neuroprotection/genetics , Signal Transduction/drug effects , Up-Regulation/drug effectsABSTRACT
In 2000, the third member of the globin family was discovered in human and mouse brain and named neuroglobin (Ngb). Ngb is a monomeric 3/3 globin structurally similar to myoglobin and to the α- and ß-chains of hemoglobin, however it displays a bis-histidyl six-coordinate heme-Fe atom. Therefore, ligand binding to the Ngb metal center is limited from the dissociation of the distal His(E7)64-Fe bond. From its discovery, more than 500 papers on Ngb structure, expression, reactivity, and localization have been published to highlight its biochemical properties and its role(s) in health and disease. In vivo experiments have shown that increased levels of Ngb significantly protect both heart and brain from hypoxic/ischemic and oxidative stress-related insults, whereas decreased Ngb levels lead to an exacerbation of tissue injuries. Although some contradictory data emerged, human Ngb overexpression has been hypothesized to protect neurons from mitochondrial dysfunctions and neurodegenerative disorders such as Alzheimer's disease, and to play a shielding role in cancer cells. Recently, the recognition of Ngb interactors and inducers enlarges the functions of this stress-inducible globin, opening new therapeutic approaches to prevent neuronal cell death. Here, structural and functional aspects of human Ngb are examined critically to highlight its roles in health and disease.
Subject(s)
Disease Susceptibility , Globins/chemistry , Globins/physiology , Nerve Tissue Proteins/chemistry , Nerve Tissue Proteins/physiology , Structure-Activity Relationship , Amino Acid Sequence , Animals , Brain/metabolism , Evolution, Molecular , Gene Expression Regulation , Humans , Ligands , Neuroglobin , Oxidation-Reduction , Polymorphism, Genetic , Protein Binding , Protein Conformation , Protein Interaction Domains and Motifs , Protein Transport , Signal Transduction , ThermodynamicsABSTRACT
17ß-Estradiol (E2) exerts neurotrophic and neuroprotective functions in the brain. Here, E2-induced increased levels of huntingtin (HTT), a protein involved in several crucial neuronal functions is reported. E2 physiological concentrations up-regulate HTT in hippocampus and striatum of rats as well as in human neuroblastoma cells. This effect requires both nuclear and extra-nuclear estrogen receptor (ER)α activities. Intriguingly, HTT silencing completely prevents E2 protective effects against oxidative stress injury. In conclusion, these data indicate for the first time that HTT is an E2-inducible protein involved in the first steps of E2-induced signaling pathways committed to neuronal protection against oxidative stress.