Induced Translocation (induced + translocation)

Distribution by Scientific Domains

Selected Abstracts

p38, MAP kinase protects rat mesangial cells from TNF-,-induced apoptosis

Yan-Lin Guo
Abstract p38 MAP kinases (p38) and c-Jun N-terminal protein kinases (JNK) have been associated with TNF-,-induced apoptosis. However, recent studies indicate that an early but brief activation of JNK and/or p38 may actually protect some cells from TNF-,-induced apoptosis. Whether the activation of JNK and p38 provides a pro- or anti-apoptotic signal for TNF-, has been controversial. In this study, we investigated the role of p38 in the regulation of TNF-, cytotoxicity in rat mesangial cells. Treatment of the cells with TNF-, alone had little effect on their viability, but they became very sensitive to apoptosis when treated with TNF-, in the presence of the p38 inhibitor SB 203580. These results suggested that the p38 pathway is critical for mesangial cells to survive the toxic effect of TNF-,. Using adenovirus-mediated gene transfer technique, we further demonstrated that p38,, but not p38,, is essential to protect the cells from TNF-, toxicity. It has been speculated that there is a synergetic interaction between the p38 and the nuclear factor-,B (NF-,B) pathways in protecting certain cells from apoptosis. However, expression of neither p38, nor its dominant negative mutant in mesangial cells interfered with TNF-,-induced translocation of NF-,B, the initial step of NF-,B activation. While it is unclear whether p38, regulates NF-,B transcription activity at other steps, it is apparent that p38, does not affect TNF-,-induced NF-,B activation at the stage of nuclear translocation. J. Cell. Biochem. 82: 556,565, 2001. 2001 Wiley-Liss, Inc. [source]

Diazoxide acts more as a PKC- , activator, and indirectly activates the mitochondrial KATP channel conferring cardioprotection against hypoxic injury

M-Y Kim
Background and purpose: Diazoxide, a well-known opener of the mitochondrial ATP-sensitive potassium (mitoKATP) channel, has been demonstrated to exert cardioprotective effect against ischemic injury through the mitoKATP channel and protein kinase C (PKC). We aimed to clarify the role of PKC isoforms and the relationship between the PKC isoforms and the mitoKATP channel in diazoxide-induced cardioprotection. Experimental approach: In H9c2 cells and neonatal rat cardiomyocytes, PKC-, activation was examined by Western blotting and kinase assay. Flavoprotein fluorescence, mitochondrial Ca2+ and mitochondrial membrane potential were measured by confocal microscopy. Cell death was determined by TUNEL assay. Key results: Diazoxide (100 ,M) induced translocation of PKC-, from the cytosolic to the mitochondrial fraction. Specific blockade of PKC-, by either ,V1-2 or dominant negative mutant PKC-, (PKC-, KR) abolished the anti-apoptotic effect of diazoxide. Diazoxide-induced flavoprotein oxidation was inhibited by either ,V1-2 or PKC-, KR transfection. Treatment with 5-hydroxydecanoate (5-HD) did not affect translocation and activation of PKC-, induced by diazoxide. Transfection with wild type PKC-, mimicked the flavoprotein-oxidizing effect of diazoxide, and this effect was completely blocked by ,V1-2 or 5-HD. Diazoxide prevented the increase in mitochondrial Ca2+, mitochondrial depolarization and cytochrome c release induced by hypoxia and all these effects of diazoxide were blocked by ,V1-2 or 5-HD. Conclusions and Implications: Diazoxide induced isoform-specific translocation of PKC-, as an upstream signaling molecule for the mitoKATP channel, rendering cardiomyocytes resistant to hypoxic injury through inhibition of the mitochondrial death pathway. British Journal of Pharmacology (2006) 149, 1059,1070. doi:10.1038/sj.bjp.0706922 [source]

Fibroblast apoptosis induced by Porphyromonas gingivalis is stimulated by a gingipain and caspase-independent pathway that involves apoptosis-inducing factor

Tesfahun Desta
Summary Porphyromonas gingivalis is an oral bacterium that causes pathology in a number of dental infections that are associated with increased fibroblast cell death. Studies presented here demonstrated that P. gingivalis stimulates cell death by apoptosis rather than necrosis. Unlike previous studies apoptosis was induced independent of proteolytic activity and was also independent of caspase activity because a pancaspase inhibitor, Z-VAD-fmk, had little effect. Moreover, P. gingivalis downregulated caspase-3 mRNA levels and caspase-3 activity. The consequence of this downregulation was a significant reduction in tumour necrosis factor-,-induced apoptosis, which is caspase-3-dependent. Immunofluorescence and immunoblot analysis revealed P. gingivalis -induced translocation of apoptosis-inducing factor (AIF) from the cytoplasm to the nucleus. siRNA studies were undertaken and demonstrated that P. gingivalis stimulated cell death was significantly reduced when AIF was silenced (P < 0.05). Treatment of human gingival fibroblasts with H-89, a protein kinase A inhibitor that blocks AIF activation also reduced P. gingivalis -induced apoptosis (P < 0.05). These results indicate that P. gingivalis causes fibroblast apoptosis through a pathway that involves protein kinase A and AIF, is not dependent upon bacterial proteolytic activity and is also independent of the classic apoptotic pathways involving caspase-3. [source]

Rituxan (anti-CD20 antibody)-induced translocation of CD20 into lipid rafts is crucial for calcium influx and apoptosis

E. Janas
Summary Rituxan, a chimeric anti-CD20 antibody, is the first antibody approved for immunotherapy in non-Hodgkin's B-cell lymphoma and other B-cell lymphoproliferative disorders. Additionally, efficacy of Rituxan treatment has been reported in nonmalignant autoimmune diseases such as rheumatoid arthritis. Crosslinking of CD20 molecules by Rituxan induces therapeutic B-cell depletion. CD20 is a B-lymphocyte specific integral membrane protein, proposed to function as a store-operated calcium channel, which is activated upon receptor-stimulated calcium depletion of intracellular stores. Crosslinking of CD20 by antibodies has been reported to induce a redistribution of CD20 molecules to specialized microdomains at the plasma membrane known as lipid rafts. Here, we report that in the absence of Rituxan, CD20 exhibits a low affinity to lipid rafts. However, binding of Rituxan significantly increases the affinity of CD20 for lipid rafts resulting in its redistribution to a fraction resistant to Triton X-100 solubilization. Furthermore, we demonstrate that disturbing the raft integrity by cholesterol extraction results in dissociation of CD20 from a Triton X-100 resistant fraction followed by complete inhibition of Rituxan-induced calcium entry and apoptosis. The integrity of lipid rafts seems to play a crucial role for CD20-induced caspase activation. These data show, for the first time, that Rituxan-induced translocation of CD20 to lipid rafts is important for increased intracellular Ca2+ levels and downstream apoptotic signalling. [source]