Immunomagnetic capture of lens membrane fractions containing steroid binding protein

Downregulation of the small GTPase SAR1A: a key event underlying alcohol-induced Golgi fragmentation in hepatocytes

The hepatic asialoglycoprotein receptor (ASGP-R) is posttranslationally modified in the Golgi en route to the plasma membrane, where it mediates clearance of desialylated serum glycoproteins. It is known that content of plasma membrane-associated ASGP-R is decreased after ethanol exposure, although the mechanisms remain elusive. Previously, we found that formation of compact Golgi requires dimerization of the largest Golgi matrix protein giantin. We hypothesize that ethanol-impaired giantin function may be related to altered trafficking of ASGP-R. Here we report that in HepG2 cells expressing alcohol dehydrogenase and hepatocytes of ethanol-fed rats, ethanol metabolism results in Golgi disorganization. This process is initiated by dysfunction of SAR1A GTPase followed by altered COPII vesicle formation and impaired Golgi delivery of the protein disulfide isomerase A3 (PDIA3), an enzyme that catalyzes giantin dimerization. Additionally, we show that SAR1A gene silencing in hepatocytes mimics the effect of ethanol: dedimerization of giantin, arresting PDIA3 in the endoplasmic reticulum (ER) and large-scale alterations in Golgi architecture. Ethanol-induced Golgi fission has no effect on ER-to-Golgi transportation of ASGP-R, however, it results in its deposition in cis-medial-, but not trans-Golgi. Thus, alcohol-induced deficiency in COPII vesicle formation predetermines Golgi fragmentation which, in turn, compromises the Golgi-to-plasma membrane transportation of ASGP-R.

DEK in the synovium of patients with juvenile idiopathic arthritis: characterization of DEK antibodies and posttranslational modification of the DEK autoantigen

OBJECTIVE

DEK is a nuclear phosphoprotein and autoantigen in a subset of children with juvenile idiopathic arthritis (JIA). Autoantibodies to DEK are also found in a broad spectrum of disorders associated with abnormal immune activation. We previously demonstrated that DEK is secreted by macrophages, is released by apoptotic T cells, and attracts leukocytes. Since DEK has been identified in the synovial fluid (SF) of patients with JIA, this study was undertaken to investigate how DEK protein and/or autoantibodies may contribute to the pathogenesis of JIA.

METHODS

DEK autoantibodies, immune complexes (ICs), and synovial macrophages were purified from the SF of patients with JIA. DEK autoantibodies and ICs were purified by affinity-column chromatography and analyzed by 2-dimensional gel electrophoresis, immunoblotting, and enzyme-linked immunosorbent assay. DEK in supernatants and exosomes was purified by serial centrifugation and immunoprecipitation with magnetic beads, and posttranslational modifications of DEK were identified by nano-liquid chromatography tandem mass spectrometry (nano-LC-MS/MS).

RESULTS

DEK autoantibodies and protein were found in the SF of patients with JIA. Secretion of DEK by synovial macrophages was observed both in a free form and via exosomes. DEK autoantibodies (IgG2) may activate the complement cascade, primarily recognize the C-terminal portion of DEK protein, and exhibit higher affinity for acetylated DEK. Consistent with these observations, DEK underwent acetylation on an unprecedented number of lysine residues, as demonstrated by nano-LC-MS/MS.

CONCLUSION

These results indicate that DEK can contribute directly to joint inflammation in JIA by generating ICs through high-affinity interaction between DEK and DEK autoantibodies, a process enhanced by acetylation of DEK in the inflamed joint.

A protein-coated magnetic beads as a tool for the rapid drug-protein binding study

A simple and fast method for the determination of the association constant (K(a)) of ligand to human serum albumin (HSA) has been developed by using human serum albumin-coated magnetic beads (HSA-MB). To date, magnetic beads (MB) have been increasingly used as a bioseparation tool, especially for DNA, RNA, protein, enzyme and cell isolation or purification. In this study, HSA-MB were used as a new tool to determine the affinity of known ligands to HSA. The K(a) for l-tryptofan, fenoprofen, ketoprofen, tolbutamide and warfarin obtained from Schathard analysis are consistent with previously reported values. The different K(a) values for ketoprofen after the acetylation of HSA-MB by preincubation with acetylosalicylic acid indicate that these beads can be successfully adapted in combined experiment. In addition, the HSA-MB experiment with phenytoin and valproic acid proved to be a simple method to examine drug displacement effect.

Analysis of single, purified inclusions as a novel approach to understand methamphetamine neurotoxicity

A variety of neurodegenerative diseases leading to movement disorders such as Parkinson's disease (PD) are characterized by neuronal inclusions. Despite evidence of the presence of these intrusions, these intracellular bodies have been poorly investigated because of the technical limits of reproducing them in experimental models and the difficulties in isolating these ultrastuctures. Here, we describe a simple method for the isolation of single, purified inclusion bodies using immunomagnetic separation. We profited from the high number and maturation stage of inclusions produced in vitro by methamphetamine (METH) in cultured PC12 cells; in fact, this experimental condition is highly reproducible and has a limited number of experimental variables, while it is predictive of what is described in vivo in dopamine neurons.

Membrane-initiated effects of progesterone on calcium dependent signaling and activation of VEGF gene expression in retinal glial cells

Neurosteroids, such as progesterone, influence central nervous system development and function by regulating a broad spectrum of physiological processes. Here, we investigated membrane-initiated actions of progesterone in the retina and identified the membrane-associated progesterone receptor component 1 (PGRMC1). We found PGRMC1 expressed mainly in retinal Muller glia (RMG) and retinal pigment epithelium, and localized uniquely to microsomal and plasma membrane fractions. In RMG, membrane-impermeable progesterone conjugate induced calcium influx and subsequent phosphatidylinositol 3-kinase-mediated phosphorylation of PKC and ERK-1/2. Induction by progesterone also led to PKC-dependent activation of VEGF gene expression and protein synthesis, suggesting a contribution of membrane-initiated hormone effects to VEGF induced neovascularization within retina.

Enhanced immunoresponse of antibody/mixed-PEG co-immobilized surface construction of high-performance immunomagnetic ELISA system

Poly(ethylene glycol) possessing pentaethylenehexamine at one end (N6-PEG) was prepared via a reductive amination reaction of aldehyde-ended PEG with pentaethylenehexamine. Using N6-PEG, an antibody/PEG co-immobilized surface was constructed on magnetic particles via an active ester reaction method. After immobilization of the antibody on the active ester surface, N6-PEG was reacted on the magnetic beads. A sandwich enzyme-linked immunosorbent assay (ELISA) system was newly constructed using PEG/antibody co-immobilized magnetic beads combined with an alkaline phosphatase (ALP)-assisted fluorescent detection system using alpha-fetoprotein (AFP) as a model antigen. The co-immobilization of both antibody and PEG on the magnetic bead surfaces reduced the nonspecific adsorption of proteins from cell lysates. Especially, when the magnetic particle surface was modified by N6-PEG mixtures with different molecular weights of 6000 and 2500 (6 kDa:2.5 kDa=9:1 w/w), the nonspecific adsorption of proteins was strongly suppressed. It is rather surprising for us that the sensitivity of the antibody on the surface was enhanced significantly when the PEG tethered chain was constructed in between the surface antibodies. Consequently, the mixed N6-PEG treatment showed a much higher S/N ratio than for the corresponding beads treated with bovine serum albumin (BSA), a conventional blocking reagent. Actually, when alpha-fetoprotein was analyzed by the magnetic bead-assisted ELISA thus constructed, the S/N ratio was about 20-fold higher for the mixed coating with PEG (6 kDa):PEG (2.5 kDa)=9:1, compared to the conventional BSA.

Purification of caveolae by affinity two-phase partitioning using biotinylated antibodies and NeutrAvidin–dextran

A new concept for affinity two-phase partitioning was tested. The partitioning was based on the interaction of target membranes with a primary antibody which, in turn, interacted with a biotinylated secondary antibody and NeutrAvidin-dextran in a poly(ethylene glycol)/dextran two-phase system. Caveolae selectively redistributed from the top phase to the NeutrAvidin-dextran-containing bottom phase by employing anti-caveolin as the primary antibody. This immunoaffinity approach was more selective than the established sucrose gradient centrifugation method and resulted in highly purified caveolae from Triton X-100-treated liver and lung plasma membranes. The same approach, employing other selective primary antibodies, should facilitate the purification also of other membrane fractions.