Mutual Regulation of Bcl-2 Proteins Independent of the BH3 Domain as Shown by the BH3-Lacking Protein Bcl-xAK

The BH3 domain of Bcl-2 proteins was regarded as indispensable for apoptosis induction and for mutual regulation of family members. We recently described Bcl-xAK, a proapoptotic splice product of the bcl-x gene, which lacks BH3 but encloses BH2, BH4 and a transmembrane domain. It remained however unclear, how Bcl-xAK may trigger apoptosis

Pneumocystis cell wall β-glucan stimulates calcium-dependent signaling of IL-8 secretion by human airway epithelial cells

<p>Abstract</p> <p>Background</p> <p>Respiratory failure secondary to alveolar inflammation during <it>Pneumocystis </it>pneumonia is a major cause of death in immunocompromised patients. Neutrophil infiltration in the lung of patients with <it>Pneumocystis </it>infection predicts severity of the infection and death. Several previous studies indicate that airway epithelial cells release the neutrophil chemoattractant proteins, MIP-2 (rodents) and IL-8 (humans), in response to <it>Pneumocystis </it>and purified <it>Pneumocystis </it>cell wall β-glucans (PCBG) through the NF-κB-dependent pathway. However, little is known about the molecular mechanisms that are involved in the activation of airway epithelium cells by PCBG resulting in the secretion of IL-8.</p> <p>Method</p> <p>To address this, we have studied the activation of different calcium-dependent mitogen-activated protein kinases (MAPKs) in 1HAEo^-cells, a human airway epithelial cell line.</p> <p>Results</p> <p>Our data provide evidence that PCBG induces phosphorylation of the MAPKs, ERK, and p38, the activation of NF-κB and the subsequently secretion of IL-8 in a calcium-dependent manner. Further, we evaluated the role of glycosphingolipids as possible receptors for β-glucans in human airway epithelial cells. Preincubation of the cells with D-<it>threo</it>-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) a potent inhibitor of the glycosphingolipids synthesis, prior to PCBG stimulation, significantly decreased IL-8 production.</p> <p>Conclusion</p> <p>These data indicate that PCBG activates calcium dependent MAPK signaling resulting in the release of IL-8 in a process that requires glycosphingolipid for optimal signaling.</p

Cholinergic receptor pathways involved in apoptosis, cell proliferation and neuronal differentiation

Acetylcholine (ACh) has been shown to modulate neuronal differentiation during early development. Both muscarinic and nicotinic acetylcholine receptors (AChRs) regulate a wide variety of physiological responses, including apoptosis, cellular proliferation and neuronal differentiation. However, the intracellular mechanisms underlying these effects of AChR signaling are not fully understood. It is known that activation of AChRs increase cellular proliferation and neurogenesis and that regulation of intracellular calcium through AChRs may underlie the many functions of ACh. Intriguingly, activation of diverse signaling molecules such as Ras-mitogen-activated protein kinase, phosphatidylinositol 3-kinase-Akt, protein kinase C and c-Src is modulated by AChRs. Here we discuss the roles of ACh in neuronal differentiation, cell proliferation and apoptosis. We also discuss the pathways involved in these processes, as well as the effects of novel endogenous AChRs agonists and strategies to enhance neuronal-differentiation of stem and neural progenitor cells. Further understanding of the intracellular mechanisms underlying AChR signaling may provide insights for novel therapeutic strategies, as abnormal AChR activity is present in many diseases

Apoptotic stress induces Bax-dependent, caspase-independent redistribution of LINC complex nesprins

The canonical function of Bcl-2 family proteins is to regulate mitochondrial membrane integrity. In response to apoptotic signals the multi-domain pro-apoptotic proteins Bax and Bak are activated and perforate the mitochondrial outer membrane by a mechanism which is inhibited by their interaction with pro-survival members of the family. However, other studies have shown that Bax and Bak may have additional, non-canonical functions, which include stress-induced nuclear envelope rupture and discharge of nuclear proteins into the cytosol. We show here that the apoptotic stimuli cisplatin and staurosporine induce a Bax/Bak-dependent degradation and subcellular redistribution of nesprin-1 and nesprin-2 but not nesprin-3, of the linker of nucleoskeleton and cytoskeleton (LINC) complex. The degradation and redistribution were caspase-independent and did not occur in Bax/Bak double knockout (DKO) mouse embryo fibroblasts (MEFs). Re-expression of Bax in Bax/Bak DKO MEFs restored stress-induced redistribution of nesprin-2 by a mechanism which requires Bax membrane localization and integrity of the alpha helices 5/6, and the Bcl-2 homology 3 (BH3) domain. We found that nesprin-2 interacts with Bax in close proximity to perinuclear mitochondria in mouse and human cells. This interaction requires the mitochondrial targeting and N-terminal region but not the BH3 domain of Bax. Our results identify nesprin-2 as a Bax binding partner and also a new function of Bax in impairing the integrity of the LINC complex

Crescimento e inflação na Argentina nos governos Kirchner

Desde 2003, a taxa de crescimento do PIB foi mais elevada na Argentina do que no Brasil, e a distribuição da renda, menos desigual. Diminuiu a pobreza. Aumentou o emprego - incluindo o setor industrial - e os empregos informais, assalariados ou não, perdem sua importância relativa. A balança comercial é fortemente superavitária, a taxa de endividamento não excessivamente elevada. A inflação real tem nível elevado, muito mais forte do que aquela anunciada pelo governo e reduz o poder aquisitivo entre as categorias mais pobres. O apreciamento recente da taxa de câmbio efetiva, o peso crescente das commodities nas exportações, das quais depende o financiamento das subvenções concedidas particularmente aos setores com forte consumo de energia, os subsídios insuficientes destinados às indústrias intensivas envolvidas com pesquisa podem transformar o círculo virtuoso de hoje num círculo vicioso amanhã.<br>Since 2003, the growth rate of the GDP has been higher in Argentina than in Brazil. Income distribution is less unequal. Poverty has decreased. Employment is growing - including in the industrial sector -; informal jobs, whether salaried or not, are loosing ground; while the balance of trade shows a trade surplus and the debt ratio is not overly right. Real inflation is hight, far higher than announced by the government, and it curtails any rise in buying power, particularly among the poorest. The recent rise ineffective exchange rates, the rise in the share of raw materials in exports, the fact that these are needed for subsidies paid mainly to energy consuming sectors, the shortage of subsidies to research intensives industries could to morrow turn what is currently a virtuous circle into a vicious circle

Disruption of the VDAC2–Bak interaction by Bcl-xS mediates efficient induction of apoptosis in melanoma cells

The proapoptotic B-cell lymphoma (Bcl)-2 protein Bcl-x(S) encloses the Bcl-2 homology (BH) domains BH3 and BH4 and triggers apoptosis via the multidomain protein Bak, however, the mechanism remained elusive. For investigating Bcl-x(S) efficacy and pathways, an adenoviral vector was constructed with its cDNA under tetracycline-off control. Bcl-x(S) overexpression resulted in efficient apoptosis induction and caspase activation in melanoma cells. Indicative of mitochondrial apoptosis pathways, Bcl-x(S) translocated to the mitochondria, disrupted the mitochondrial membrane potential and induced release of cytochrome c, apoptosis-inducing factor and second mitochondria-derived activator of caspases. In melanoma cells, Bcl-x(S) resulted in significant Bak activation, and Bak knockdown as well as Bcl-x(L) overexpression abrogated Bcl-x(S)-induced apoptosis, whereas Mcl-1 (myeloid cell leukemia-1) knockdown resulted in a sensitization. With regard to the particular role of voltage-dependent anion channel 2 (VDAC2) for inhibition of Bak, we identified here a notable interaction between Bcl-x(S) and VDAC2 in melanoma cells, which was proven in reciprocal coimmunoprecipitation analyses. On the other hand, Bcl-x(S) showed no direct interaction with Bak, and its binding to VDAC2 appeared as also independent of Bak expression. Suggesting a new proapoptotic mechanism, Bcl-x(S) overexpression resulted in disruption of the VDAC2–Bak interaction leading to release of Bak. Further supporting this pathway, overexpression of VDAC2 strongly decreased apoptosis by Bcl-x(S). New proapoptotic pathways are of principle interest for overcoming apoptosis deficiency of melanoma cells