To date, no vaccines or effective drugs have been approved to prevent or treat COVID-19 and the current standard care relies on supportive treatments. Therefore, based on the fast and global spread of the virus, urgent investigations are warranted in order to develop preventive and therapeutic drugs. In this regard, treatments addressing the immunopathology of SARS-CoV-2 infection have become a major focus. Notably, while a rapid and well-coordinated immune response represents the first line of defense against viral infection, excessive inflammatory innate response and impaired adaptive host immune defense may lead to tissue damage both at the site of virus entry and at systemic level. Several studies highlight relevant changes occurring both in innate and adaptive immune system in COVID-19 patients. In particular, the massive cytokine and chemokine release, the so-called “cytokine storm”, clearly reflects a widespread uncontrolled dysregulation of the host immune defense. Although the prospective of counteracting cytokine storm is compelling, a major limitation relies on the limited understanding of the immune signaling pathways triggered by SARS-CoV-2 infection. The identification of signaling pathways altered during viral infections may help to unravel the most relevant molecular cascades implicated in biological processes mediating viral infections and to unveil key molecular players that may be targeted. Thus, given the key role of the immune system in COVID-19, a deeper understanding of the mechanism behind the immune dysregulation might give us clues for the clinical management of the severe cases and for preventing the transition from mild to severe stages.

The microbiota is a complex ecosystem of microorganisms consisting of bacteria, viruses, protozoa, and fungi, living in different districts of the human body, such as the gastro-enteric tube, skin, mouth, respiratory system, and the vagina. Over 70% of the microbiota lives in the gastrointestinal tract in a mutually beneficial relationship with its host. The microbiota plays a major role in many metabolic functions, including modulation of glucose and lipid homeostasis, regulation of satiety, production of energy and vitamins. It exerts a role in the regulation of several biochemical and physiological mechanisms through the production of metabolites and substances. In addition, the microbiota has important anti-carcinogenetic and anti-inflammatory actions. There is growing evidence that any modification in the microbiota composition can lead to several diseases, including metabolic diseases, such as obesity and diabetes, and cardiovascular diseases. This is because alterations in the microbiota composition can cause insulin resistance, inflammation, vascular, and metabolic disorders. The causes of the microbiota alterations and the mechanisms by which microbiota modifications can act on the development of metabolic and cardiovascular diseases have been reported. Current and future preventive and therapeutic strategies to prevent these diseases by an adequate modulation of the microbiota have been also discussed.

Expansion of a polyglutamine sequence in the N terminus of huntingtin is the gain-of-function event that causes Huntington's disease. This mutation affects primarily the medium-size spiny neurons of the striatum. Huntingtin is expressed in many neuronal and non-neuronal cell types, implying a more general function for the wild-type protein. Here we report that wild-type huntingtin acts by protecting CNS cells from a variety of apoptotic stimuli, including serum withdrawal, death receptors, and pro-apoptotic Bcl-2 homologs. This protection may take place at the level of caspase-9 activation. The full-length protein also modulates the toxicity of the poly-Q expansion. Cells expressing full-length mutant protein are susceptible to fewer death stimuli than cells expressing truncated mutant huntingtin.

Age-related macular degeneration (AMD) is the most common reason of visual impairment in the elderly in the Western countries. The degeneration of retinal pigment epithelial cells (RPE) causes secondarily adverse effects on neural retina leading to visual loss. The aging characteristics of the RPE involve lysosomal accumulation of lipofuscin and extracellular protein aggregates called “drusen”. Molecular mechanisms behind protein aggregations are weakly understood. There is intriguing evidence suggesting that protein SQSTM1/p62, together with autophagy, has a role in the pathology of different degenerative diseases. It appears that SQSTM1/p62 is a connecting link between autophagy and proteasome mediated proteolysis, and expressed strongly under the exposure to various oxidative stimuli and proteasomal inhibition. ELAVL1/HuR protein is a post-transcriptional factor, which acts mainly as a positive regulator of gene expression by binding to specific mRNAs whose corresponding proteins are fundamental for key cellular functions. We here show that, under proteasomal inhibitor MG-132, ELAVL1/HuR is up-regulated at both mRNA and protein levels, and that this protein binds and post-transcriptionally regulates SQSTM1/p62 mRNA in ARPE-19 cell line. Furthermore, we observed that proteasomal inhibition caused accumulation of SQSTM1/p62 bound irreversibly to perinuclear protein aggregates. The addition of the AMPK activator AICAR was pro-survival and promoted cleansing by autophagy of the former complex, but not of the ELAVL1/HuR accumulation, indeed suggesting that SQSTM1/p62 is decreased through autophagy-mediated degradation, while ELAVL1/HuR through the proteasomal pathway. Interestingly, when compared to human controls, AMD donor samples show strong SQSTM1/p62 rather than ELAVL1/HuR accumulation in the drusen rich macular area suggesting impaired autophagy in the pathology of AMD.

Neuronal ELAV-like proteins (HuB, HuC, and HuD) are highly conserved RNA-binding proteins able to selectively associate with the 3 UTR of a subset of target mRNAs and increase their cytoplasmic stability and rate of translation. We previously demonstrated the involvement of these proteins in learning, reporting that they undergo a sustained up-regulation in the hippocampus of mice trained in a spatial discrimination task. Here, we extend this finding, showing that a similar up-regulation occurs in the hippocampus of rats trained in another spatial learning paradigm, the Morris water maze. HuD, a strictly neuron-specific ELAV-like protein, is shown to increase after learning, with a preferential binding to the cytoskeletal fraction. HuD up-regulation is associated with an enhancement of GAP-43 mRNA and protein levels, with an apparently increased HuD colocalization with the GAP-43 mRNA and an increased association of neuronal ELAV-like proteins with the GAP-43 mRNA. These learning-dependent biochemical events appear to be spatiotemporally controlled, because they do not occur in another brain region involved in learning, the retrosplenial cortex, and at the level of protein expression they show extinction 1 month after training despite memory retention. By contrast, HuD mRNA levels still remain increased after 1 month in the CA1 region. This persistence may have implications for long-term memory recall.

No abstract

Long-lasting changes in cellular functions require reprogramming of protein synthesis as a result of cell signaling events that influence nuclear transcription and͞or the fate of the transcribed mRNAs, ultimately leading to changed mRNA availability to the ribosome. Posttranscriptional mechanisms are emerging as key controllers of gene expression (reviewed in refs. 1 and 2) and are postulated to be critical for the localized changes in protein levels involved in cell differentiation and in the maintenance of the differentiated phenotype, especially in polarized cells such as neurons (3). Modulation of mRNA decay appears to be an efficient posttranscriptional way of controlling expression, because small changes in mRNA half-life can radically alter the abundance of a given mRNA and the amount of the relevant protein (4). Indeed, the decay rates of many mRNAs are governed by defined sequence determinants and by RNA-binding proteins (RBPs) acting on these determinants. The best-characterized regulative cis motifs in mammalian mRNAs are the AREs (adenine-and uridine-rich elements), which are found in the 3Ј UTRs of mRNAs endowed with a rapid response to cell environmental stimuli, as in many cytokines and oncogenes (reviewed in ref. 5).In the human genome, a general ARE consensus is present in 5-8% of expressed genes (6), and it represents a docking site for RBPs controlling mRNA stability, probably by modulation of exosome activity (7). ARE-dependent mRNA decay has been shown to be a target of at least two signaling cascades. The first is the p38 mitogen-activated protein kinase (MAPK)-MAPKAPK2 pathway, which, when activated, stabilizes ARE-bearing interleukin mRNAs (8-10), possibly through inactivation of the ARE-binding, mRNA-destabilizing RBP tristetraprolin (11, 12). The second pathway, which has been less investigated, is triggered by phorbol esters (phorbol 12-myristate 13-acetate, PMA) and calcium ionophore administration to culture cells, leading again to stabilization of ARE-bearing mRNAs (13-19). For its features, this pathway could involve the calcium-and diacylglycerol-regulated PKC isozymes, possibly resulting in the activation of a downstream function able to induce stabilization of ARE-bearing mRNAs. Fifteen years ago, Malter and coworkers (20, 21) identified a factor of Ϸ32 kDa, which they called AUBF for AU-rich binding factor, that was induced to bind ARE sequences after brief PMA treatment or calcium influx and was inactivated by dephosphorylation in peripheral blood mononuclear cells. AUBF was shown to be almost entirely located on polysomes when stimulated (22).ELAV (embryonic lethal abnormal vision) proteins, or Hu antigens, represent the best-studied ARE-binding RBPs and are known from a substantial body of evidence to stabilize target mRNAs in the cytoplasm (reviewed in refs. 23 and 24). In vertebrates, HuB, HuC, and HuD are neuron-specific members of the ELAV family (nELAV proteins), whereas HuR is ubiquitously expressed; all four proteins are highly homologous in sequence, are Ϸ40 kDa in s...

Several lines of biochemical evidence correlate the presence of energy metabolic defects with the functional alterations associated with brain aging and with the pathogenesis of neurodegenerative disorders such as Alzheimer's disease. Within this context we tested the ability of insulin to regulate the amyloid precursor protein (APP) processing in SH-SY5Y neuroblastoma cells. Our findings show that insulin promotes APP metabolism by a glucose-independent mechanism. We demonstrate a novel intracellular pathway that increases the rate of secretion of soluble APP through the activity of phosphatidyl-inositol 3 kinase (PI3-K). This pathway, downstream of insulin receptor tyrosine kinase activity, does not involve either the activation of protein kinase C or the mitogen-activated protein kinase (MAP-K) pathway. Because of the physiological role of PI3-K in the translocation of glucose transporter-containing vesicles, we speculate that PI3-K involvement in APP metabolism may act at the level of vesicular trafficking.