Dendritic arborization and spine formation are critical for the functioning of neurons. Although many proteins have been identified recently as regulators of dendritic morphogenesis, the intracellular signaling pathways that control these processes are not well understood. Here we report that the Ras-phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) signaling pathway plays pivotal roles in the regulation of many aspects of dendrite formation. Whereas the PI3K-Akt-mTOR pathway alone controlled soma and dendrite size, a coordinated activation together with the Ras-mitogen-activated protein kinase signaling pathway was required for increasing dendritic complexity. Chronic inhibition of PI3K or mTOR reduced soma and dendrite size and dendritic complexity, as well as density of dendritic filopodia and spines, whereas a short-term inhibition promoted the formation of mushroom-shaped spines on cells expressing constitutively active mutants of Ras, PI3K, or Akt, or treated with the upstream activator BDNF. Together, our data underscore the central role of a spatiotemporally regulated key cell survival and growth pathway on trophic regulation of the coordinated development of dendrite size and shape.

PurposeFerroptosis is a new mode of regulated cell death, which is completely distinct from other cell death modes based on morphological, biochemical, and genetic criteria. This study evaluated the therapeutic role of ferroptosis in classic chemotherapy drugs, including the underlying mechanism.Materials and MethodsCell viabilitywas detected by using the methylthiazoltetrazlium dye uptake method. RNAiwas used to knockout iron-responsive element binding protein 2, and polymerase chain reaction, western blot was used to evaluate the efficiency. Intracellular reduced glutathione level and glutathione peroxidases activitywere determined by related assay kit. Intracellularreactive oxygen species levelswere determined by flowcytometry. Electron microscopywas used to observe ultrastructure changes in cell.ResultsAmong five chemotherapeutic drugs screened in this study, cisplatin was found to be an inducer for both ferroptosis and apoptosis in A549 and HCT116 cells. The depletion of reduced glutathione caused by cisplatin and the inactivation of glutathione peroxidase played the vital role in the underlying mechanism. Besides, combination therapy of cisplatin and erastin showed significant synergistic effect on their anti-tumor activity.ConclusionFerroptosis had great potential to become a new approach in anti-tumor therapies and make up for some classic drugs, which open up a new way for their utility in clinic.

Memory storage in mammalian neurons probably depends on both biochemical events and morphological alterations in dendrites. Here we report an activity-dependent stabilization of the MAP kinase (MAPK) pathway, prominent in hippocampal dendrites. The longevity of the signal in these dendrites was increased to hours when multiple spaced stimuli were used. Likewise, spaced stimuli and MAPK activation were critical for protrusion of new dendritic filopodia that also remained stable for hours. Our experiments define a new role for stimulus-specific responses of MAPK signaling in activity-dependent neuronal plasticity. The local biochemical signaling in dendrites complements MAPK signaling in gene expression. Together, these processes may support long-lasting behavioral changes.

The cAMP-responsive element binding protein (CREB), a key regulator of gene expression, is activated by phosphorylation on Ser-133. Several different protein kinases possess the capability of driving this phosphorylation, making it a point of potential convergence for multiple intracellular signaling cascades. Previous work in neurons has indicated that physiologic synaptic stimulation recruits a fast calmodulin kinase IV (CaMKIV)-dependent pathway that dominates early signaling to CREB. Here we show in hippocampal neurons that the fast, CaMK-dependent pathway can be followed by a slower pathway that depends on Ras͞mitogen-activated protein kinase (MAPK), along with CaMK. This pathway was blocked by dominant-negative Ras and was specifically recruited by depolarizations that produced strong intracellular Ca 2؉ transients. When both pathways were recruited, phosphorylated CREB (pCREB) formation was overwhelmingly dominated by the CaMK pathway between 0 and 10 min, and by the MAPK pathway at 60 min, whereas the two pathways acted in concert at 30 min. The Ca 2؉ signals that produced only rapid CaMK signaling to pCREB or both rapid CaMK and slow MAPK signaling deviated significantly for only Ϸ1 min, yet their differential impact on pCREB extended over a much longer period, between 20 and 60 min and beyond, which is of likely significance for gene expression. The CaMK-dependent MAPK pathway may inform the nucleus about stimulus amplitude. In contrast, the CaMKIV pathway may be well suited to conveying information on the precise timing of localized synaptic stimuli, befitting its greater speed and sensitivity, whereas the previously described calcineurin pathway may carry information about stimulus duration.

Calcium-calmodulin-dependent protein kinase II (CaMKII) promotes the maturation of retinotectal glutamatergic synapses in Xenopus. Whether CaMKII activity also controls morphological maturation of optic tectal neurons was tested using in vivo time-lapse imaging of single neurons over periods of up to 5 days. Dendritic arbor elaboration slows with maturation, in correlation with the onset of CaMKII expression. Elevating CaMKII activity in young neurons by viral expression of constitutively active CaMKII slowed dendritic growth to a rate comparable to that of mature neurons. CaMKII overexpression stabilized dendritic structure in more mature neurons, whereas CaMKII inhibition increased their dendritic growth. Thus, endogenous CaMKII activity limits dendritic growth and stabilizes dendrites, and it may act as an activity-dependent mediator of neuronal maturation.

Summary We have recently demonstrated that reactive glial cells can be directly reprogrammed into functional neurons by single neural transcription factor NeuroD1. Here we report that a combination of small molecules can also reprogram human astrocytes in culture into fully functional neurons. We demonstrate that sequential exposure of human astrocytes to a cocktail of 9 small molecules that inhibit glial but activate neuronal signaling pathways can successfully reprogram astrocytes into neurons in 8-10 days. This chemical reprogramming is mediated through epigenetic regulation and involves transcriptional activation of NEUROD1 and NEUROGENIN2. The human astrocyte-converted neurons can survive for >5 months in culture and form functional synaptic networks with synchronous burst activities. The chemical reprogrammed human neurons can also survive for >1 month in the mouse brain in vivo and integrate into local circuits. Our study opens a new avenue using chemical compounds to reprogram reactive glial cells into functional neurons.

Purpose: The prognostic value of circulating tumor cells (CTC) detected in breast cancer patients is currently under debate. Different time points of blood collections and various CTC assays have been used in the past decades. Here, we conducted the first comprehensive meta-analysis of published literature on the prognostic relevance of CTC, including patients with early and advanced disease.Experimental Design: A comprehensive search for articles published between January 1990 and January 2012 was conducted; reviews of each study were conducted and data were extracted. The main outcomes analyzed were overall survival (OS) and disease-free survival (DFS) in early-stage breast cancer patients, as well as progression-free survival (PFS) and OS in metastatic breast cancer patients. Pooled hazard ratio (HR) and 95% confidence intervals (CIs) were calculated using the random and the fixed-effects models. Subgroup and sensitivity analyses were also conducted.Results: Forty-nine eligible studies enrolling 6,825 patients were identified. The presence of CTC was significantly associated with shorter survival in the total population. The prognostic value of CTC was significant in both early (DFS: HR, 2.86; 95% CI, 2.19-3.75; OS: HR, 2.78; 95% CI, 2.22-3.48) and metastatic breast cancer (PFS: HR, 1.78; 95% CI, 1.52-2.09; OS: HR, 2.33; 95% CI, 2.09-2.60). Further subgroup analyses showed that our results were stable irrespective of the CTC detection method and time point of blood withdrawal.Conclusion: Our present meta-analysis indicates that the detection of CTC is a stable prognosticator in patients with early-stage and metastatic breast cancer. Further studies are required to explore the clinical utility of CTC in breast cancer.

Activity-independent and activity-dependent mechanisms work in concert to regulate neuronal growth, ensuring the formation of accurate synaptic connections. CPG15, a protein regulated by synaptic activity, functions as a cell-surface growth-promoting molecule in vivo. In Xenopus laevis, CPG15 enhanced dendritic arbor growth in projection neurons, with no effect on interneurons. CPG15 controlled growth of neighboring neurons through an intercellular signaling mechanism that requires its glycosylphosphatidylinositol link. CPG15 may represent a new class of activity-regulated, membrane-bound, growth-promoting proteins that permit exquisite spatial and temporal control of neuronal structure.The cpg15 gene was identified in a forward genetic approach designed to isolate activityregulated genes that mediate synaptic plasticity (1). In the adult rat, cpg15 is induced in the brain by kainate (KA) and in visual cortex by light (2). During development, cpg15 expression is correlated with times of afferent in-growth, dendritic elaboration, and synaptogenesis (2). Sequence analysis predicts a small, secreted protein (2) that is membrane-bound by a glycosylphosphatidylinositol (GPI) linkage (3).Antiserum generated against bacterially expressed rat CPG15 recognizes a protein from rat brain dentate gyrus extracts (Fig. 1A) (4) of the size predicted by sequence analysis. A protein of similar size is induced in Xenopus laevis after KA injections into the brain ventricle ( Fig. 1A) (5). In situ hybridizations using a partial clone of Xenopus cpg15 indicate that the CPG15 mRNA is expressed in retinal ganglion cells and in differentiated neurons throughout the central nervous system (CNS) of stage-47 tadpoles (6). Xenopus CPG15 protein is present in neurons and axons throughout the CNS (7,8). In the optic tectum, differentiated neurons label in a honeycomb pattern similar to N-CAM (neural cell adhesion molecule) and other cell-surface antigens, while cells in the proliferative zone have undetectable levels of CPG15 (Fig. 1C).To investigate the cellular function of CPG15, we used a recombinant vaccinia virus (VV) to express CPG15 in optic tectal cells of albino Xenopus tadpoles (9, 10). Tadpoles were infected by ventricular injection with VV carrying rat cpg15 and β-galactosidase (β-gal) cDNAs in a dual promoter vector, or with a control virus containing only the β-gal cDNA (11). Two days after viral infection and approximately 24 hours after the beginning of expression of foreign protein (9), single tectal cells were labeled with DiI (10, 12). Confocal images through the entire structure of each neuron were collected at 24-hour intervals over a period of 3 days, and three-dimensional (3D) images were reconstructed from this (13). The most prominent effect of CPG15 on the morphology of tectal projection neurons was that the dendritic arbors of neurons from CPG15VV-infected animals increased their total dendritic branch length (TDBL) and became more complex than arbors of neurons from β-gal-infected or uninfected animals ( Fi...