C-terminus of HSC70-interacting protein (CHIP, ) is a ubiquitously expressed cytosolic E3-ubiquitin ligase. CHIP-deficient mice exhibit cardiovascular stress and motor dysfunction prior to premature death. This phenotype is more consistent with animal models in which master regulators of autophagy are affected rather than with the mild phenotype of classic E3-ubiquitin ligase mutants. The cellular and biochemical events that contribute to neurodegeneration and premature aging in CHIP KO models remain poorly understood. Electron and fluorescent microscopy demonstrates that CHIP deficiency is associated with greater numbers of mitochondria, but these organelles are swollen and misshapen. Acute bioenergetic stress triggers CHIP induction and re-localization to mitochondria where it plays a role in the removal of damaged organelles. This mitochondrial clearance is required for protection following low-level bioenergetic stress in neurons. CHIP expression overlaps with stabilization of the redox stress sensor PTEN-inducible kinase 1 (PINK1) and is associated with increased LC3-mediated mitophagy. Introducing human promoter-driven vectors with mutations in either the E3 ligase or TPR domains of CHIP in primary neurons derived from CHIP-null animals enhances CHIP accumulation at mitochondria. Exposure to autophagy inhibitors suggests the increase in mitochondrial CHIP is likely due to diminished clearance of these CHIP-tagged organelles. Proteomic analysis of WT and CHIP KO mouse brains (4 male, 4 female per genotype) reveals proteins essential for maintaining energetic, redox and mitochondrial homeostasis undergo significant genotype-dependent expression changes. Together these data support the use of CHIP deficient animals as a predictive model of age-related degeneration with selective neuronal proteotoxicity and mitochondrial failure. Mitochondria are recognized as central determinants of neuronal function and survival. We demonstrate that C-terminus of HSC70-Interacting Protein (CHIP) is critical for neuronal responses to stress. CHIP upregulation and localization to mitochondria is required for mitochondrial autophagy (mitophagy). Unlike other disease-associated E3 ligases such as Parkin and Mahogunin, CHIP controls homeostatic and stress-induced removal of mitochondria. While CHIP deletion results in greater numbers of mitochondria, these organelles have distorted inner membranes without clear cristae. Neuronal cultures derived from animals lacking CHIP are more vulnerable to acute injuries, and transient loss of CHIP renders neurons incapable of mounting a protective response following low-level stress. Together these data suggest that CHIP is an essential regulator of mitochondrial number, cell signaling and survival.

Synaptic inhibition plays a crucial role in regulating neuronal excitability, which is the foundation of nervous system function. This inhibition is largely mediated by the neurotransmitters GABA and glycine that activate Cl--permeable ion channels, which means that the strength of inhibition depends on the Cl- gradient across the membrane. In neurons, the Cl- gradient is primarily determined by two secondarily-active cation-chloride cotransporters (CCCs), NKCC1 and KCC2. CCC-mediated regulation of the neuronal Cl- gradient is critical for healthy brain function, as dysregulation of CCCs has emerged as a key mechanism underlying neurological disorders including epilepsy, neuropathic pain, and autism spectrum disorder. This Review begins with an overview of neuronal chloride transporters before explaining the dependent relationship between these CCCs, Cl- regulation, and inhibitory synaptic transmission. We then discuss the evidence for how CCCs can be regulated, including by activity and their protein interactions, which underlie inhibitory synaptic plasticity. For readers who may be interested in conducting experiments on CCCs and neuronal excitability, we have included a section on techniques for estimating and recording intracellular Cl-, including their advantages and limitations. While the focus of this Review is on neurons, we also examine how Cl- is regulated in glial cells, which in turn regulate neuronal excitability through the tight relationship between this non-neuronal cell type and synapses. Lastly, we discuss the relatively extensive and growing literature on how CCC-mediated neuronal excitability contributes to neurological disorders.

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Coronaviruses have emerged as alarming pathogens owing to their inherent ability of genetic variation and cross-species transmission. Coronavirus infection burdens the endoplasmic reticulum (ER.), causes reactive oxygen species production and induces host stress responses, including unfolded protein response (UPR) and antioxidant system. In this study, we have employed a neurotropic murine β-coronavirus (M-CoV) infection in the Central Nervous System (CNS) of experimental mice model to study the role of host stress responses mediated by an interplay of DJ-1 and XBP1. DJ-1 is an antioxidant molecule with established functions in neurodegeneration. However, its regulation in virus-induced cellular stress response is less explored. Our study showed that M-CoV infection activated the glial cells and induced antioxidant and UPR genes during the acute stage when the viral titer peaks. As the virus particles decreased and acute neuroinflammation diminished at day ten p.i., a significant upregulation in UPR responsive XBP1, antioxidant DJ-1, and downstream signaling molecules, including Nrf2, was recorded in the brain tissues. Additionally, preliminary in silico analysis of the binding between the DJ-1 promoter and a positively charged groove of XBP1 is also investigated, thus hinting at a mechanism behind the upregulation of DJ-1 during MHV-infection. The current study thus attempts to elucidate a novel interplay between the antioxidant system and UPR in the outcome of coronavirus infection.

Astrocyte and microglial activation are two hallmarks associated with oxidative stress induction in neural cells. Generation of reactive oxygen species (ROS) is one of the molecular outcomes of neurotropic Mouse Hepatitis Virus A59 (MHV‐A59) infection in the Central Nervous System in an experimental animal model for human demyelinating disease Multiple Sclerosis. MHV‐A59 infection has been found to cause encephalitis, meningitis, and hepatitis in acute stage (Day 5–7 post‐infection) and progressive demyelination in chronic stage (Day 30 post‐infection). The virus has shown glial cell tropism leading to its activation, although the role of oxidative stress in this aspect is not well understood. Therefore, our work focuses on the regulation and function of important anti‐oxidative markers like DJ‐1, Nrf2, and HMOX‐1, upon viral infection in animal CNS tissue, isolated cells from tissues, primary culture and cell culture‐based studies. All three genes were found to be upregulated in vivo in mice brain at acute stage (Day 3 and 5) and chronic stage (Day 30) post‐infection. Similar upregulation was also observed in isolated microglia from mice brain, primary astrocytes, and microglia cultured from neonatal mice brain. In vitro studies with DBT astrocytoma cell line and N9 microglia cell line showed oxidative stress generation and upregulation in all three genes at initial time points of viral infection; however all the genes were found to be downregulated at higher time points. DBT cells exhibited decrease in cell viability and oxidative stress generation upon viral infection, and such changes had been observed to be ameliorated when DJ‐1 was stably transfected into DBT cells. Literature studies indicate that XBP1, an ER stress marker, upregulates DJ‐1 expression upon oxidative stress induction. In silico and in vitro studies showed that XBP1 was differentially activated in both DBT and N9 cells and was associated with DJ‐1 promoter upon viral infection in N9 cells. MHV‐A59 has shown tropism for glial cells resulting in their activation, and oxidative stress‐related cellular mechanisms involving these genes can contribute to the activation process of these glial cells. Support or Funding Information This study was supported by the Department of Biotechnology (DBT) and Indian Institute of Science Education and Research Kolkata (IISER Kolkata). Soumya Kundu was supported by University Grant Commission (UGC). Gisha Rose Anthony, Vineeth A. Raveendran, and Rahul Kumar were supported by DST‐INSPIRE fellowship under the banner of IISER Kolkata.