The Journal of biological chemistry
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Most patients with cystic fibrosis (CF) suffer from acute and chronic pulmonary infections with bacterial pathogens, which often determine their life quality and expectancy. Previous studies have demonstrated a downregulation of the acid ceramidase in CF epithelial cells resulting in an increase of ceramide and a decrease of sphingosine. Sphingosine kills many bacterial pathogens, and the downregulation of sphingosine seems to determine the infection susceptibility of cystic fibrosis mice and patients. ⋯ We report that genetic deficiency or functional inhibition of CFTR/Cftr results in an upregulation of interferon regulatory factor 8 (IRF8) and a concomitant downregulation of acid ceramidase expression with CF and an increase of ceramide and a reduction of sphingosine levels in tracheal and bronchial epithelial cells from both human individuals or mice. CRISPR/Cas9- or siRNA-mediated downregulation of IRF8 prevented changes of acid ceramidase, ceramide, and sphingosine in CF epithelial cells and restored resistance to Pseudomonas aeruginosa infections, which is one of the most important and common pathogens in lung infection of patients with CF. These studies indicate that CFTR deficiency causes a downregulation of acid ceramidase via upregulation of IRF8, which is a central pathway to control infection susceptibility of CF cells.
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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the COVID-19 global pandemic, utilizes the host receptor angiotensin-converting enzyme 2 (ACE2) for viral entry. However, other host factors might also play important roles in SARS-CoV-2 infection, providing new directions for antiviral treatments. GRP78 is a stress-inducible chaperone important for entry and infectivity for many viruses. ⋯ Loss of GRP78 markedly reduced cell surface ACE2 expression and led to activation of markers of the unfolded protein response. Treatment of lung epithelial cells with a humanized monoclonal antibody (hMAb159) selected for its safe clinical profile in preclinical models depleted cell surface GRP78 and reduced cell surface ACE2 expression, as well as SARS-2-S-driven viral entry and SARS-CoV-2 infection in vitro. Our data suggest that GRP78 is an important host auxiliary factor for SARS-CoV-2 entry and infection and a potential target to combat this novel pathogen and other viruses that utilize GRP78 in combination therapy.
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The novel severe acute respiratory syndrome coronavirus (SARS-CoV-2) has emerged to a pandemic and caused global public health crisis. Human angiotensin-converting enzyme 2(ACE2) was identified as the entry receptor for SARS-CoV-2. As a carboxypeptidase, ACE2 cleaves many biological substrates besides angiotensin II to control vasodilatation and vascular permeability. ⋯ Surprisingly, SARS-CoV-2 trimeric spike protein increased ACE2 proteolytic activity ∼3-10 fold against model peptide substrates, such as caspase-1 substrate and Bradykinin-analog. The enhancement in ACE2 enzymatic function was mediated by the binding of SARS-CoV-2 spike RBD domain. These results highlighted the potential for SARS-CoV-2 infection to enhance ACE2 activity, which may be relevant to the cardiovascular symptoms associated with COVID-19.
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Progress in the study of circulating, cell-free nuclear DNA (ccf-nDNA) in cancer detection has led to the development of noninvasive clinical diagnostic tests and has accelerated the evaluation of ccf-nDNA abundance as a disease biomarker. Likewise, circulating, cell-free mitochondrial DNA (ccf-mtDNA) is under similar investigation. However, optimal ccf-mtDNA isolation parameters have not been established, and inconsistent protocols for ccf-nDNA collection, storage, and analysis have hindered its clinical utility. ⋯ Overall, we calculate an improved efficiency of recovery of ∼95-fold for ccf-mtDNA and 20-fold for ccf-nDNA when compared with the initial procedure. Digestion conditions, liquid-handling characteristics, and magnetic particle processor programming all contributed to increased recovery without detectable positional effects. To our knowledge, this is the first high-throughput approach optimized for ccf-mtDNA and ccf-nDNA recovery and serves as an important starting point for clinical studies.
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Adipocyte browning appears to be a potential therapeutic strategy to combat obesity and related metabolic disorders. Recent studies have shown that apelin, an adipokine, stimulates adipocyte browning and has negative cross-talk with angiotensin II receptor type 1 (AT1 receptor) signaling. Here, we report that losartan, a selective AT1 receptor antagonist, induces browning, as evidenced by an increase in browning marker expression, mitochondrial biogenesis, and oxygen consumption in murine adipocytes. ⋯ Furthermore, in vivo apelin knockdown by adeno-associated virus carrying-apelin shRNA significantly inhibited losartan-induced adipocyte browning. In summary, these data suggested that AT1 receptor antagonism by losartan promotes the browning of white adipocytes via the induction of apelin expression. Therefore, apelin modulation may be an effective strategy for the treatment of obesity and its related metabolic disorders.