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Plasma Membrane Expression (plasma + membrane_expression)
Selected AbstractsIdentification of plasma membrane autoantigens in autoimmune hepatitis type 1 using a proteomics tool,,HEPATOLOGY, Issue 3 2008Fatima Tahiri Autoimmune hepatitis (AIH) is a liver disease with circulating autoantibodies predominantly directed against widely held cellular components. Because AIH is a liver-specific disease, autoantibodies against plasma membrane antigens may be involved in its pathogenesis and have been reported; however, no definite identification has been described. We thus investigated the fine specificity of anti-hepatocyte plasma membrane autoantibodies in type 1 AIH (AIH-1) using a proteomic tool. A plasma membrane,enriched fraction was validated using enzymatic activity and western blot analysis experiments. Sera from AIH-1 patients (n = 65) and from 90 controls, that is, healthy blood donors (n = 40) and patients with systemic diseases (n = 20) or other liver diseases (n = 30), were studied by immunoblot performed with plasma membrane proteins resolved by either sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or 2-dimensional (2D) electrophoresis. Proteins contained in the immunoreactive spots were identified by sequences provided by ion-trap mass spectrometry. Hepatocytes probed with sera were also studied using confocal immunofluorescence and immunoelectron microscopy. The more prominent bands stained by patient sera were located at 38 kDa, 48, 50, 52 kDa, 62 kDa, 70 kDa, and a 95-kDa double band. Six proteins with known potential plasma membrane expression were identified: liver arginase (38 kDa), cytokeratins (CK) 8 and 18 (48-52 kDa), heat shock proteins (HSP) of 60, 70, 90 kDa, and valosin-containing protein (VCP) of 92 kDa. The presence of anti-membrane antibodies was confirmed by immunofluorescence and immunoelectron microscopy. Conclusion: Overall, our data demonstrate that liver arginase, CK 8/18, HSP 60, HSP 70, HSP 90, and VCP represent potential candidate targets on liver membrane for autoantibodies in AIH-1. (HEPATOLOGY 2008;47:937,948.) [source] Post-translational regulation of EAAT2 function by co-expressed ubiquitin ligase Nedd4-2 is impacted by SGK kinasesJOURNAL OF NEUROCHEMISTRY, Issue 4 2006Christoph Boehmer Abstract The human excitatory amino acid transporter (EAAT)2 is the major glutamate carrier in the mammalian CNS. Defective expression of the transporter results in neuroexcitotoxicity that may contribute to neuronal disorders such as amyotrophic lateral sclerosis (ALS). The serum and glucocorticoid inducible kinase (SGK) 1 is expressed in the brain and is known to interact with the ubiquitin ligase Nedd4-2 to modulate membrane transporters and ion channels. The present study aimed to investigate whether SGK isoforms and the related kinase, protein kinase B (PKB), regulate EAAT2. Expression studies in Xenopus oocytes demonstrated that glutamate-induced inward current (IGLU) was stimulated by co-expression of SGK1, SGK2, SGK3 or PKB. IGLU is virtually abolished by Nedd4-2, an effect abrogated by additional co-expression of either kinase. The kinases diminish the effect through Nedd4-2 phosphorylation without altering Nedd4-2 protein abundance. SGKs increase the transporter maximal velocity without significantly affecting substrate affinity. Similar to glutamate-induced currents, [3H] glutamate uptake and cell surface abundance of the transporter were increased by the SGK isoforms and down-regulated by the ubiquitin ligase Nedd4-2. In conclusion, all three SGK isoforms and PKB increase EAAT2 activity and plasma membrane expression and thus, may participate in the regulation of neuroexcitability. [source] Regulated trafficking of neurotransmitter transporters: common notes but different melodiesJOURNAL OF NEUROCHEMISTRY, Issue 1 2002Michael B. Robinson Abstract The activity of biogenic amine and amino acid neurotransmitters is limited by presynaptic and astrocytic Na+ -dependent transport systems. Their functional importance is underscored by the observation that these transporters are the targets of broad classes of psychotherapeutic agents, including antidepressants and stimulants. Early studies suggested that the activity of these transporters can be fine tuned by a number of different signaling pathways. In the past five years, several groups have provided compelling evidence that changing the cell surface availability of these transporters contributes to this fine tuning. This regulated trafficking can result in rapid (within minutes) increases or decreases in the plasma membrane expression of these transporters and is independent of transcriptional or translational control mechanisms. Many of the same signaling molecules, including protein kinase C (PKC), tyrosine kinase, phosphatidylinositol 3-kinase (P13-K), and protein phosphatase, regulate the transporters for different neurotransmitters. In addition to these classical receptor activated pathways, transporter substrates also regulate activity and cell surface expression of these transporters. In fact, some of the transporters form complexes with signaling molecules. Given the functional and genetic similarities of these transporters, it is not surprising that the same signaling molecules regulate their trafficking, but except for the molecules, the actual effects on individual transporters are remarkably different. It,is as if the same musical notes have been rearranged into several different melodies. [source] Sub-lethal heat shock induces plasma membrane translocation of 70-kDa heat shock protein in viable, but not in apoptotic, U-937 leukaemia cellsAPMIS, Issue 3 2010ELENA B. LASUNSKAIA Lasunskaia EB, Fridlianskaia I, Arnholdt AV, Kanashiro M, Guzhova I, Margulis B. Sub-lethal heat shock induces plasma membrane translocation of 70-kDa heat shock protein in viable, but not in apoptotic, U-937 leukaemia cells. APMIS 2010; 118: 179,87. Heat shock protein 70 kDa, Hsp70, is an important intracellular factor that protects cells from stress. Unusual plasma membrane expression of Hsp70, observed in some cancer cells, contributes to the cell's recognition and elimination by the immune system. Induction of apoptosis in cancer cells was demonstrated to increase Hsp70 translocation to the surface membrane, enhancing immunogenic effects through the stimulation of dendritic cells. As hyperthermia is proposed as a method of choice for anti-cancer therapy, we examined whether apoptosis induction by heat shock enhances Hsp70 membrane translocation in U-937 leukaemia cells. Cells were exposed to sub-lethal heat shock, and intracellular and membrane-bound Hsp70 expression was evaluated in apoptotic and viable cell sub-populations, employing flow cytometry and immunofluorescence. Heat shock induced Hsp70 membrane translocation in the viable cells that were able to enhance Hsp70 production upon heating, but not in the cells undergoing apoptosis that continued to express low basal levels of the intracellular protein. Data suggest that the protein translocation was associated with the increasing Hsp70 content rather than the apoptotic process. Apoptosis does not contribute to externalization of Hsp70, at least in the cells with low levels of this protein. [source] | ||||||||||