The Akt kinase has been widely assumed for years as a key downstream effector of the PI3K signaling pathway in promoting neuronal survival. This notion was however challenged by the finding that neuronal survival responses were still preserved in mice with reduced Akt activity. Moreover, here we show that the Akt signaling is elevated in the aged brain of two different mice models of Alzheimer Disease. We manipulate the rate of Akt stimulation by employing knock-in mice expressing a mutant form of PDK1 (phosphoinositide-dependent protein kinase 1) with reduced, but not abolished, ability to activate Akt. We found increased membrane localization and activity of the TACE/ADAM17 α-secretase in the brain of the PDK1 mutant mice with concomitant TNFR1 processing, which provided neurons with resistance against TNFα-induced neurotoxicity. Opposite to the Alzheimer Disease transgenic mice, the PDK1 knock-in mice exhibited an age-dependent attenuation of the unfolding protein response, which protected the mutant neurons against endoplasmic reticulum stressors. Moreover, these two mechanisms cooperatively provide the mutant neurons with resistance against amyloid-beta oligomers, and might singularly also contribute to protect these mice against amyloid-beta pathology.

The phosphoinositide (PI) 3-kinase/Akt signaling pathway plays essential roles during neuronal development. 3-Phosphoinositide-dependent protein kinase 1 (PDK1) coordinates the PI 3-kinase signals by activating 23 kinases of the AGC family, including Akt. Phosphorylation of a conserved docking site in the substrate is a requisite for PDK1 to recognize, phosphorylate, and activate most of these kinases, with the exception of Akt. We exploited this differential mechanism of regulation by generating neuron-specific conditional knock-in mice expressing a mutant form of PDK1, L155E, in which the substrate-docking site binding motif, termed the PIF pocket, was disrupted. As a consequence, activation of all the PDK1 substrates tested except Akt was abolished. The mice exhibited microcephaly, altered cortical layering, and reduced circuitry, leading to cognitive deficits and exacerbated disruptive behavior combined with diminished motivation. The abnormal patterning of the adult brain arises from the reduced ability of the embryonic neurons to polarize and extend their axons, highlighting the essential roles that the PDK1 signaling beyond Akt plays in mediating the neuronal responses that regulate brain development. The phosphoinositide 3-kinase (PI3K) signaling pathway regulates cell survival, proliferation, growth, and motility, as well as metabolism, in response to extracellular signals. Class I PI3Ks phosphorylate the membrane phospholipid phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P 2 ] to generate the phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P 3 ] second messenger (1, 2). In neurons, stimulation of PI3K by neurotrophic factors, neurotransmitters, or guidance cues results in the activation of protein kinase B (PKB) (also termed Akt), the most studied downstream effector of this signaling pathway. Akt phosphorylates and inactivates a number of cellular substrates controlling different aspects of neuronal development. They include PRAS40 and TSC2, leading to mammalian TORC1 (mTORC1) activation, which in turn promotes the synthesis of selected sets of proteins involved in the differentiation program (3); glycogen synthase kinase 3 (GSK3), which regulates cytoskeleton dynamics and participates in the establishment and maintenance of neuronal polarity (4, 5); and FOXO, which promotes the expression of genes inhibiting apoptosis (6). Genetic analysis in mice has uncovered the functional significance of PI3K for brain morphology and physiology (7-10), whereas deregulation of this signaling pathway has pathophysiological consequences in human neurodevelopmental disorders, such as schizophrenia (11-13) and autism (14, 15).3-Phosphoinositide-dependent protein kinase 1 (PDK1) transduces many agonist-induced cellular responses by activating an entire set of AGC kinase family members, in addition to Akt (16). They include S6K, SGK, RSK, and protein kinase C (PKC) isoforms. Upon cell stimulation, PDK1 is enabled to phosphorylate the T loops of all these AGC kinases, resulting in their activation (17, 18).Sin...

Our data highlight the low expression levels of DFF40/CAD and the absence of DNA laddering as common molecular traits in GBM. These findings could be of major importance for understanding the malignant behavior of remaining tumor cells after radiochemotherapy.

Background: Caspase activation triggers apoptotic cell death. Results: Chelerythrine triggers necrotic-like cell death by an early and pronounced activation of caspases. Conclusion:The rate and level of caspase activation dictate whether cells die displaying apoptotic or necrotic features. Significance: Most antitumor drugs prompt concomitant apoptotic and necrotic morphological deaths; therefore understanding how the apoptosis-necrosis continuum occurs should shed light on anticancer treatment efficacy.

Thymic stromal lymphopoietin (TSLP) is a cytokine released by human lung epithelium in response to external insult. Considered as a master switch in T helper 2 lymphocyte (Th2) mediated responses, TSLP is believed to play a key role in allergic diseases including asthma. The aim of this study was to use a phenotypic approach to identify new biological and chemical starting points for inhibition of TSLP production in human bronchial epithelial cells (NHBE), with the objective of reducing Th2-mediated airway inflammation. To this end, a phenotypic screen was performed using poly I:C / IL-4 stimulated NHBE cells interrogated with a 44,974 compound library. As a result, 85 hits which downregulated TSLP protein and mRNA levels were identified and a representative subset of 7 hits was selected for further characterization. These molecules inhibited the activity of several members of the MAPK, PI3K and tyrosine kinase families and some of them have been reported as modulators of cellular phenotypic endpoints like cell-cell contacts, microtubule polymerization and caspase activation. Characterization of the biological profile of the hits suggested that mTOR could be a key activity involved in the regulation of TSLP production in NHBE cells. Among other targeted kinases, inhibition of p38 MAPK and JAK kinases showed different degrees of correlation with TSLP downregulation, while Syk kinase did not seem to be related. Overall, inhibition of TSLP production by the selected hits, rather than resulting from inhibition of single isolated targets, appeared to be due to a combination of activities with different levels of relevance. Finally, a hit expansion exercise yielded additional active compounds that could be amenable to further optimization, providing an opportunity to dissociate TSLP inhibition from other non-desired activities. This study illustrates the potential of phenotypic drug discovery to complement target based approaches by providing new chemistry and biology leads.