eEF-2 Phosphorylation Down-Regulates P-Glycoprotein Over-Expression in Rat Brain Microvessel Endothelial Cells

ObjectiveWe investigated whether glutamate, NMDA receptors, and eukaryote elongation factor-2 kinase (eEF-2K)/eEF-2 regulate P-glycoprotein expression, and the effects of the eEF-2K inhibitor NH125 on the expression of P-glycoprotein in rat brain microvessel endothelial cells (RBMECs).MethodsCortex was obtained from newborn Wistar rat brains. After surface vessels and meninges were removed, the pellet containing microvessels was resuspended and incubated at 37°C in culture medium. Cell viability was assessed by the MTT assay. RBMECs were identified by immunohistochemistry with anti-vWF. P-glycoprotein, phospho-eEF-2, and eEF-2 expression were determined by western blot analysis. Mdr1a gene expression was analyzed by RT-PCR.ResultsMdr1a mRNA, P-glycoprotein and phospho-eEF-2 expression increased in L-glutamate stimulated RBMECs. P-glycoprotein and phospho-eEF-2 expression were down-regulated after NH125 treatment in L-glutamate stimulated RBMECs.ConclusionseEF-2K/eEF-2 should have played an important role in the regulation of P-glycoprotein expression in RBMECs. eEF-2K inhibitor NH125 could serve as an efficacious anti-multidrug resistant agent.     

Tensin: A potential link between the cytoskeleton and signal transduction

Cytoskeletal proteins provide the structural foundation that allows cells to exist in a highly organized manner. Recent evidence suggests that certain cytoskeletal proteins not only maintain structural integrity, but might also be associated with signal transduction and suppression of tumorigenesis. Since the time of the discovery of tensin, a fair amount of data has been gathered which supports the notion that tensin is one such protein possessing these characteristics. In this review, we discuss recent studies that: (1) elucidate a role for tensin in maintenance of cellular structure and signal transduction; (2) implicate tensin as the anchor for actin filaments at the focal adhesion; (3) describe the phosphorylation of tensin; (4) describe potential targets for its Src homology region 2 domain; (5) describe the association between tensin and the nuclear protein p130; and (6) demonstrate that increased tensin expression in a cell line appears to reduce its transformation potential.     

Microplastics in soil-plant system: effects of nano/microplastics on plant photosynthesis,rhizosphere microbes and soil properties in soil with different residues

Plant and Soil - To investigate the effects of polystyrene microplastics (PS-beads) on the soil properties, photosynthesis of Flowering Chinese cabbage, the rhizosphere microbial community and...     

Cytokine-induced cell death in immortalized Schwann cells: roles of nitric oxide and cyclic AMP

Tumor necrosis factor-alpha and interferon-gamma are pleiotropic cytokines that regulate Schwann cell responses during injury and inflammatory demyelination. We have previously shown that cyclic AMP (cAMP)-elevating agents decrease the demyelination and Wallerian degeneration in experimental allergic neuritis. In this study, we examined the role of cAMP in cytokine-mediated signaling in a spontaneously immortal Schwann cell clone (iSC). We found that tumor necrosis factor-alpha and interferon-gamma exert synergistic inhibitory action on Schwann cell viability via the production of nitric oxide (NO) and ceramide (cer). Furthermore, we found that: (i) NO synthase inhibitors attenuate the cytokine-induced cer accumulation and cell death indicating that NO acts upstream of cer; and (ii) cytokine-induced cell death is decreased in iSCs pretreated continuously for 48-72 h with forskolin, an activator of adenylate cyclase. Although forskolin modulates the phosphorylation of ERKs and Akt, it decreases the susceptibility of iSC to cytokines via a separate mechanism operating after NO induction and before cer accumulation. We propose that the protective effect of cAMP-elevating agents in experimental allergic neuritis may be mediated in part via modulation of Schwann cell responses to cytokines.     

Activity staining for glutamate and alanine dehydrogenases in polyacrylamide gels of varying porosity. A study of bovine placental enzyme forms.

A procedure has been developed for characterizing the various molecular forms of placental and liver glutamate dehydrogenases through a combination of activity staining and varying gel pore size in electrophoresis. At a concentration of 2 mg/ml, the bovine liver GDH remained associated in a very high molecular weight form, while the placental enzyme was substantially dissociated to a molecular species of near 240,000 molecular weight and several charge isomeric species of near 160,000 molecular weight. The general approach outlined here provides a means of definitely correlating the electrophoretic behavior of various dehydrogenase isozymes with both glutamate and alanine dehydrogenase activities and molecular size and should be applicable, even in crude extracts to other dehydrogenase enzymes which exhibit multiple forms or states of association.