IUBMB Life
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Patho/physiological platelet aggregate (thrombus) formation is initiated by engagement of platelet surface receptors, glycoprotein (GP)Ib‐IX‐V and GPVI that bind von Willebrand factor or collagen. Although beneficial in response to vascular injury by preventing blood loss (haemostasis), platelet aggregation in a sclerotic coronary artery or other diseased blood vessel (thrombosis) can cause thrombotic diseases like heart attack and stroke. At the molecular level, ligand interactions with GPIb‐IX‐V or GPVI trigger signalling responses, including elevation of cytosolic Ca2 +, dissociation of calmodulin from their cytoplasmic domains, cytoskeletal actin‐filament rearrangements, activation of src‐family kinases or PI 3‐kinase, and 'inside‐out' activation of the integrin, αIIbβ3 (GPIIb‐IIIa), that binds von Willebrand factor or fibrinogen and mediates platelet aggregation. Furthermore, emerging evidence supports a topographical co‐association of these receptors of the leucine‐rich repeat family (GPIb‐IX‐V) and immunoglobulin superfamily (GPVI) in an adhesive cluster or 'adhesosome'. This arrangement may underlie common mechanisms of initiating thrombus formation in haemostasis or thrombotic disease. IUBMB Life, 56: 13‐18, 2004
The mitochondrial K + cycle consists of influx and efflux pathways for K + and anions. Net movement of K + salts across the inner membrane causes changes of matrix volume, so regulation of the cycle is vital for maintaining the structural integrity of the organelle. The mitochondrial K + cycle also appears to play important roles in cellular pathophysiology in vivo. Opening the mitochondrial ATP‐sensitive K + channel (mitoK ATP ) prior to ischemia protects the heart from ischemia‐reperfusion injury. MitoK ATP is an important player in the cell signaling pathways for ischemic protection and also for gene transcription, roles that appear to depend on the ability of mitoK ATP opening to trigger increased mitochondrial production of reactive oxygen species. MitoK ATP opening during both ischemia and reperfusion and during the high work state is found to preserve the structure of the intermembrane space and thereby maintains the normally low outer membrane permeability to adenine nucleotides. This review discusses the properties of the mitochondrial K + cycle that help to understand the basis of these effects.
We investigated a signaling pathway leading to activation of extracellular signal‐regulated protein kinase (Erk) 1 and 2 in Rat‐2 cells stimulated with sphingosine 1‐phosphate (S1P). S1P treatment transiently activated Erk‐1/‐2 in a dose‐dependent manner, and its activation was blocked by pertussis toxin, expression of RasN17, or inhibition of Raf or MEK‐1/‐2. S1P‐induced activation of Erk‐1/‐2 was also suppressed by the inhibition of epidermal growth factor (EGF) receptor tyrosine kinase with the specific inhibitor AG1478, suggesting that activation of EGF receptor tyrosine kinase was involved in the signaling pathway. S1P‐induced Erk‐1/‐2 activation was enhanced up to 2‐fold by inhibiting protein kinase C (PKC) with GF109203X, and PKC inhibition in the absence of S1P treatment also activated Erk‐1/‐2. The stimulatory effects of Erk‐1/‐2 activation by PKC inhibition was blocked by treating cells with AG1478, suggesting the involvement of PKC in the regulation of EGF receptor tyrosine kinase activation that leads to Erk‐1/‐2 activation. Together, these results suggest that S1P activates the EGF receptor through a PKC‐dependent pathway that links Ras signaling to the activation of Erk‐1/‐2 in Rat‐2 cells.
The green fluorescent protein (GFP) from the jellyfish
Geldanamycin (GA), a benzoquinone ansamycin, is one of the specific inhibitors of 90‐kDa heat shock protein and induces growth inhibition and apoptosis in certain cancer cell lines. We have investigated the mechanism of GA‐induced growth inhibition in K562 erythroleukemic cells. DNA flow‐cytometric analysis indicated that GA‐induced growth arrest was associated with G2/M phase arrest of the cell cycle. GA treatment down‐regulated the expression of cyclin B1 and inhibited phosphorylation of Cdc2 protein, both key regulatory proteins at the G2/M boundary. GA also markedly inhibited the Cdc2 kinase activity, which may be in part a result of up‐regulation of p27KIP1 by GA. The present results suggest a novel mechanism that p27KIP1 could be involved in the regulation of G2 to M phase transition.
HSP90 is one of the most abundant heat shock proteins (HSPs) in eukaryotic cells and is found in complex with several regulatory proteins such as kinases and transcription factors. Geldanamycin (GA), a benzoquinone ansamycin, specifically binds to HSP90 and disrupts the interaction of HSP90 and target proteins. Thus, GA has been used as a specific inhibitor of HSP90. In this study, we examined whether GA could affect protein synthesis and gene expression in the human erythroleukemic cell line K562. Treatment with GA, but not herbimycin A (another benzoquinone ansamycin), highly induced a 70‐kDa protein, which was revealed to be HSP70 by immunoblotting and immunoprecipitation with anti‐HSP70 antibody. The expression of HSP28 was also enhanced by GA. Furthermore, GA induced the activation of heat shock factor 1 (HSF1), but not HSF2, as determined by electromobility shift and electromobility supershift assay. In addition, similar to heat shock treatment, GA induced the phosphorylation of HSF1. Heat shock element‐binding activity and phosphorylation of HSF1 were attenuated 3 h after GA treatment. These results indicate that the functional inactivation of HSP90 by GA potentially stimulates the expression of heat shock proteins through activation of HSF1.
Các glycerophospholipid phosphatidylcholine (PC) và phosphatidylethanolamine (PE) chiếm hơn 50% tổng số loài phospholipid trong màng eukaryote và do đó đóng vai trò quan trọng trong cấu trúc và chức năng của các màng này. Trong hầu hết các tế bào eukaryote, PC và PE được tổng hợp thông qua phản ứng aminocoholphosphotransferase, sử dụng
The related disorders of obesity and diabetes are increasing to epidemic proportions. The role of neutral lipid storage and hydrolysis, and hence the adipocyte, is central to understanding this phenomenon. The adipocyte holds the major source of stored energy in the body in the form of triacylglycerols (TAG). It has been known for over 35 years that the breakdown of TAG and release of free (unesterified) fatty acids and glycerol from fat tissue can be regulated by a cAMP‐mediated process. However, beyond the initial signaling cascade, the mechanistic details of this lipolytic reaction have remained unclear. Work in recent years has revealed that both hormone‐sensitive lipase (HSL), generally thought to be the rate‐limiting enzyme, and perilipin, a lipid droplet surface protein, are required for optimal lipid storage and fatty acid release. There are multiple perilipin proteins encoded by mRNA splice variants of a single perilipin gene. The perilipin proteins are polyphosphorylated by protein kinase A and phosphorylation is necessary for translocation of HSL to the lipid droplet and enhanced lipolysis. Hence, the surface of the lipid storage droplet has emerged as a central site of regulation of lipolysis. This review will focus on adipocyte lipolysis with emphasis on hormone signal transduction, lipolytic enzymes, the lipid storage droplet, and fatty acid release from the adipocyte. IUBMB Life, 56: 379‐385, 2004
Nonalcoholic fatty liver disease (NAFLD) represents the most common chronic liver disease in western countries, being considered the hepatic manifestation of metabolic syndrome. Cumulative lines of evidence suggest that olive oil, used as primary source of fat by Mediterranean populations, may play a key role in the observed health benefits on NAFLD. In this review, we summarize the state of the art of the knowledge on the protective role of both major and minor components of olive oil on lipid metabolism during NAFLD. In particular, the biochemical mechanisms responsible for the increase or decrease in hepatic lipid content are critically analyzed, taking into account that several studies have often provided different and/or conflicting results in animal models fed on olive oil‐enriched diet. In addition, new findings that highlight the hypolipidemic and the antisteatotic actions of olive oil phenols are presented. As mitochondrial dysfunction plays a key role in the pathogenesis of NAFLD, the targeting of these organelles with olive oil phenols as a powerful therapeutic approach is also discussed. © 2015 IUBMB Life, 67(1):9–17, 2015
Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease of unknown etiology characterized by degradation of cartilage and bone, accompanied by unimpeded proliferation of synoviocytes of altered phenotype. In the present study, we investigated the involvement of the glucagon‐like peptide 1 (GLP‐1) receptor on human fibroblast‐like synoviocytes (FLS) in the pathogenesis of RA using the selective GLP‐1 agonist exenatide, a licensed drug used for the treatment of type 2 diabetes. Our results indicate that exenatide may play a role in regulating tumor necrosis factor‐α‐induced mitochondrial dysfunction by increasing mitochondrial membrane potential, oxidative stress by reducing the production of reactive oxygen species, the expression of NADPH oxidase 4, expression of matrix metalloproteinase (MMP)‐3 and MMP‐13, release of proinflammatory cytokines including interleukin‐1β (IL‐1β), IL‐6, monocyte chemoattractant protein‐1, and high‐mobility group protein 1, as well as activation of the p38/nuclear factor of κ light polypeptide gene enhancer in B‐cells inhibitor, α/nuclear factor κB signaling pathway in primary human RA FLS. These positive results indicate that exenatide may have potential as a therapeutic agent for the treatment and prevention of RA. © 2019 IUBMB Life, 9999(9999):1–9, 2019
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