A new procedure is described for the isolation of synaptosomes from various parts of mammalian brain. This method utilizes an isoosmotic Percoll/sucrose discontinuous gradient and has some advantages over the traditionally used synaptosomal isolation techniques: (1) it is possible to prepare suitable gradients while retaining isoosmolarity; (2) the time of the preparation is remarkably short (approximately 1 h); (3) if necessary, the gradient material can be easily removed from the samples. Intact synaptosomes were recovered from the 10%/16% (vol/vol) Percoll interphase. The fractions were identified and characterized by electron microscopy and by several biochemical markers for synaptosomes and other subcellular organelles. The homogeneity of the preparations is comparable to or better than that of synaptosomes prepared by the conventional methods. This procedure has been successfully used for the isolation of synaptosomes from very small tissue samples of various experimental animals and human brain.
An ecto-ATP diphosphohydrolase (ATPDase) was purified to homogeneity from vesiculosomes shed from chicken oviduct. First, the ecto-ATPDase-enriched vesiculosomes were concentrated by filtration, differential centrifugation, and exclusion chromatography. Next, the nonionic detergent, Nonidet P-40, was used to extract the ecto-ATPDase from vesiculosomal membranes, and the solubilized enzyme was further purified by ion exchange (DEAE-Bio-Gel) and lentil-lectin-Sepharose 4B chromatography. In the final stage, immunoaffinity chromatography was utilized to obtain purified ecto-ATPDase. More than 25,000-fold purification was achieved. Specific activity of the purified enzyme was greater than 800 mol/min/mg of protein with MgATP as the substrate, the highest ever reported for an ATPDase. The enzyme also hydrolyzed other nucleoside triphosphates in the presence of magnesium at similar rates and CaATP and MgADP at lower rates. The molecular mass of the purified glycoprotein was 80 kDa as determined by SDS-polyacrylamide gel electrophoresis and Western blot analysis. Based on its enzymatic properties, the relationship of the chicken oviduct ecto-ATPDase with other reported ATPDases and ecto-ATPases is discussed.The chicken oviduct has been used as a model system for studying secretion (1). Enzymes which are postulated to be involved in the egg formation process, such as an ecto-protein kinase (2), various phosphatases (3), and an ATPase have been investigated by Rosenberg et al. (4). The ATPase, first described by Haaland and Rosenberg (5), showed extensive kinetic similarities to the Mg 2ϩ
Purpose
Endometrial cancer (EC) is the most common gynecologic malignancy. One promising biomarker is epithelial membrane protein-2 (EMP2), and its expression is an independent prognostic indicator for tumors with poor clinical outcome expression. The present study assesses the suitability of EMP2 as a therapeutic target.
Experimental Design
Human monovalent anti-EMP2 antibody fragments were isolated from a human phage display library, and engineered as bivalent antibody fragments (diabodies) with specificity and avidity to both EMP2 peptides and native cell-surface EMP2 protein. Diabodies were assessed using cell death and apoptosis assays. In addition, the efficacy of EMP2 diabodies on EC tumors was determined using mouse xenograft models.
Results
Treatment of human endometrial adenocarcinoma cell lines with anti-EMP2 diabodies induced significant cell death and caspase 3 cleavage in vitro. These responses correlated with cellular EMP2 expression, and were augmented by progesterone (which physiologically induces EMP2 expression). In vivo, treatment of subcutaneous human xenografts of HEC-1A cell lines with anti-EMP2 diabodies suppressed tumor growth, and induced striking xenograft cell death.
Conclusions
These findings suggest that EMP2 may be a potential pharmacological target for human EC.
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