Differential autophagic cell death under stress with ectopic cytoplasmic and mitochondrial-specific PPP2R2B in human neuroblastoma cells

Intellectual disability: dendritic anomalies and emerging genetic perspectives

Intellectual disability (ID) corresponds to several neurodevelopmental disorders of heterogeneous origin in which cognitive deficits are commonly associated with abnormalities of dendrites and dendritic spines. These histological changes in the brain serve as a proxy for underlying deficits in neuronal network connectivity, mostly a result of genetic factors. Historically, chromosomal abnormalities have been reported by conventional karyotyping, targeted fluorescence in situ hybridization (FISH), and chromosomal microarray analysis. More recently, cytogenomic mapping, whole-exome sequencing, and bioinformatic mining have led to the identification of novel candidate genes, including genes involved in neuritogenesis, dendrite maintenance, and synaptic plasticity. Greater understanding of the roles of these putative ID genes and their functional interactions might boost investigations into determining the plausible link between cellular and behavioral alterations as well as the mechanisms contributing to the cognitive impairment observed in ID. Genetic data combined with histological abnormalities, clinical presentation, and transgenic animal models provide support for the primacy of dysregulation in dendrite structure and function as the basis for the cognitive deficits observed in ID. In this review, we highlight the importance of dendrite pathophysiology in the etiologies of four prototypical ID syndromes, namely Down Syndrome (DS), Rett Syndrome (RTT), Digeorge Syndrome (DGS) and Fragile X Syndrome (FXS). Clinical characteristics of ID have also been reported in individuals with deletions in the long arm of chromosome 10 (the q26.2/q26.3), a region containing the gene for the collapsin response mediator protein 3 (CRMP3), also known as dihydropyrimidinase-related protein-4 (DRP-4, DPYSL4), which is involved in dendritogenesis. Following a discussion of clinical and genetic findings in these syndromes and their preclinical animal models, we lionize CRMP3/DPYSL4 as a novel candidate gene for ID that may be ripe for therapeutic intervention.

Systematic Analysis of Human Protein Phosphatase Interactions and Dynamics

Coordinated activities of protein kinases and phosphatases ensure phosphorylation homeostasis, which, when perturbed, can instigate diseases, including cancer. Yet, in contrast to kinases, much less is known about protein phosphatase functions and their interactions and complexes. Here, we used quantitative affinity proteomics to assay protein-protein interactions for 54 phosphatases distributed across the three major protein phosphatase families, with additional analysis of their 12 co-factors. We identified 838 high-confidence interactions, of which 631, to our knowledge, have not been reported before. We show that inhibiting the activity of phosphatases PP1 and PP2A by okadaic acid disrupts their specific interactions, supporting the potential of therapeutics that target these proteins. Additional analyses revealed candidate physical and functional interaction links to phosphatase-based regulation of several signaling pathways and to human cancer. Our study provides an initial glimpse of the protein interaction landscape of phosphatases and their functions in cellular regulation.

Synergistic anti-tumour effects of tetrandrine and chloroquine combination therapy in human cancer: a potential antagonistic role for p21

BACKGROUND AND PURPOSE

Tetrandrine, a bisbenzylisoquinoline alkaloid isolated from the Chinese medicinal herb Stephaniae tetrandrae, has a long history in Chinese clinical applications to treat diverse diseases. Tetrandrine induced apoptosis or, at low concentrations, autophagy of human hepatocellular carcinoma cells. Here we have tested the effects of inhibitors of autophagy such as chloroquine, on the response to low concentrations of tetrandrine in cancer cells.

EXPERIMENTAL APPROACH

Cultures of several cancer cell lines, including Huh7, U251, HCT116 and A549 cells, were exposed to tetrandrine, chloroquine or a combination of these compounds. Cell viability and content of reactive oxygen species (ROS) were measured and synergy assessed by calculation of the combination index. Western blot and RT-PCR assays were also used along with fluorescence microscopy and histochemical techniques.

KEY RESULTS

Combinations of tetrandrine and chloroquine were more cytotoxic than the same concentrations used separately and these effects showed synergy. Such effects involved increased ROS generation and were dependent on caspase-3 but independent of Akt activity. Blockade of tetrandrine-induced autophagy with 3-methyladenine or bafilomycin-A1 induced apoptosis in cancer cells. Lack of p21 protein (p21(-/-) HCT116 cells) increased sensitivity to the apoptotic effects of the combination of tetrandrine and chloroquine. In a tumour xenograft model in mice, combined treatment with tetrandrine and chloroquine induced ROS accumulation and cell apoptosis, and decreased tumour growth.

CONCLUSIONS AND IMPLICATIONS

The combinations of tetrandrine and chloroquine exhibited synergistic anti-tumour activity, in vitro and in vivo. Our results suggest a novel therapeutic strategy for tumour treatment.

Energy crisis: the role of oxidative phosphorylation in acute inflammation and sepsis

Mitochondrial dysfunction is increasingly recognized as an accomplice in most of the common human diseases including cancer, neurodegeneration, diabetes, ischemia/reperfusion injury as seen in myocardial infarction and stroke, and sepsis. Inflammatory conditions, both acute and chronic, have recently been shown to affect mitochondrial function. We here discuss the role of oxidative phosphorylation (OxPhos), focusing on acute inflammatory conditions, in particular sepsis and experimental sepsis models. We discuss mitochondrial alterations, specifically the suppression of oxidative metabolism and the role of mitochondrial reactive oxygen species in disease pathology. Several signaling pathways including metabolic, proliferative, and cytokine signaling affect mitochondrial function and appear to be important in inflammatory disease conditions. Cytochrome c oxidase (COX) and cytochrome c, the latter of which plays a central role in apoptosis in addition to mitochondrial respiration, serve as examples for the entire OxPhos system since they have been studied in more detail with respect to cell signaling. We propose a model in which inflammatory signaling leads to changes in the phosphorylation state of mitochondrial proteins, including Tyr304 phosphorylation of COX catalytic subunit I. This results in an inhibition of OxPhos, a reduction of the mitochondrial membrane potential, and consequently a lack of energy, which can cause organ failure and death as seen in septic patients.