Affinity purification of cellular retinoic acid-binding protein on 14-carboxy-13-cis-retinamide-sepharose 4B.
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ABSTRACT: A biologically active bifunctional retinoid, ethyl 14-carboxyretinoate, has been synthesized and shown to bind cellular retinoic acid (RA)-binding protein (CRABP) via its free carboxy group. We describe herein the synthesis of 14-carboxy-13-cis-retinamide-Sepharose 4B, which is an affinity matrix bearing an all-trans-RA moiety, and thus was used to purify and characterize CRABP from chick-embryo skin. An amide bond was first formed between the free carboxy group of the retinoid and a primary amino group of aminohexyl-Sepharose 4B, by reaction with carbodi-imide, and the ester group of the resin-bound retinoid was then hydrolysed in an alkaline medium. Polyacrylamide-gel electrophoresis and f.p.l.c. Superose column-chromatographic analysis demonstrated that the affinity-purified CRABP (Mr 15,000) was close to electrophoretic homogeneity (greater than 90%) and specifically interacts with RA. By using affinity gel chromatography, conversion of holo-CRABP into apo-CRABP by treatment with p-hydroxymercuribenzoate and a possible involvement of a thiol group in RA binding to CRABP were established. This affinity procedure provides several advantages: (i) 14-carboxy-13-cis-retinamide-Sepharose exhibited high efficiency and selectivity for RA-binding protein (i.e. retinol- or fatty-acid-binding proteins did not bind); (ii) the presence of the amide linkage between the ligand and the matrix makes this affinity resin relatively stable to cytosolic enzymes; and (iii) other RA-binding proteins, e.g. nuclear receptor(s), may be purified.
Project description:Background and purposeIsotretinoin (13-cis-retinoic acid; 13-cRA) is a differentiation inducer used to treat minimal residual disease after myeloablative therapy for high-risk neuroblastoma. However, more than 40% of children develop recurrent disease during or after 13-cRA treatment. The plasma concentrations of 13-cRA in earlier studies were considered subtherapeutic while 4-oxo-13-cis-RA (4-oxo-13-cRA), a metabolite of 13-cRA considered by some investigators as inactive, were greater than threefold higher than 13-cRA. We sought to define the metabolic pathways of 13-cRA and investigated the anti-tumour activity of its major metabolite, 4-oxo-13-cRA.Experimental approachEffects of 13-cRA and 4-oxo-13-cRA on human neuroblastoma cell lines were assessed by DIMSCAN and flow cytometry for cell proliferation, MYCN down-regulation by reverse transcription PCR and immunoblotting, and neurite outgrowth by confocal microscopy. 13-cRA metabolism was determined using tandem MS in human liver microsomes and in patient samples.Key resultsSix major metabolites of 13-cRA were identified in patient samples. Of these, 4-oxo-13-cRA was the most abundant, and 4-oxo-13-cRA glucuronide was also detected at a higher level in patients. CYP3A4 was shown to play a major role in catalysing 13-cRA to 4-oxo-13-cRA. In human neuroblastoma cell lines, 4-oxo-13-cRA and 13-cRA were equi-effective at inducing neurite outgrowth, inhibiting proliferation, decreasing MYCN mRNA and protein, and increasing the expression of retinoic acid receptor-? mRNA and protein levels.Conclusions and implicationsWe showed that 4-oxo-13-cRA is as active as 13-cRA against neuroblastoma cell lines. Plasma levels of both 13-cRA and 4-oxo-13-cRA should be evaluated in pharmacokinetic studies of isotretinoin in neuroblastoma.
Project description:We performed pulldown assays followed by mass-spectrometry analysis using biotin-tagged 13-cis retinoic acid to identify its binding targets in HeLa cells
Project description:Pyridoxal 5'-phosphate (PLP) is a ubiquitous and versatile cofactor utilized by numerous enzymes involved in amino acid biosynthetic pathways. Immobilized PLP is a valuable tool to isolate unknown PLP-dependent enzymes in nature or to perform in vitro selection or directed evolution on existing or de novo PLP-dependent enzymes. The C-6 position is preferred for covalent immobilization of PLP because it maintains all important functional groups in their native, unmodified form. Previously reported diazonium derivatization methods for C-6 immobilization utilized an azide linker compound that is hazardous and not readily available. Here we report a safer and more accessible method to synthesize p-diazobenzoyl-derivatized Sepharose 4B using the N-hydroxysuccinimide (NHS) ester chemistry. The derivative was used to immobilize PLP, and the resulting C-6 immobilized PLP had a loading of ~2.6 μmol PLP per mL of resin, comparable to commercially available products of other immobilized cofactors.
Project description:Chronic allograft nephropathy is characterized by chronic inflammation and fibrosis. Because retinoids exhibit anti-proliferative, anti-inflammatory, and anti-fibrotic functions, the effects of low and high doses of 13-cis-retinoic acid (13cRA) were studied in a chronic Fisher344-->Lewis transplantation model. In 13cRA animals, independent of dose (2 or 20 mg/kg body weight/day) and start (0 or 14 days after transplantation) of 13cRA administration, serum creatinine was significantly lower and chronic rejection damage was dramatically reduced, including subendothelial fibrosis of preglomerular vessels and chronic tubulointerstitial damage. The number of infiltrating mononuclear cells and their proliferative activity were significantly diminished. The mRNA expression of chemokines (MCP-1/CCL2, MIP-1alpha/CCL3, IP-10/CXCL10, RANTES/CCL5) and proteins associated with fibrosis (plasminogen activator inhibitor-1, transforming growth factor-beta1, and collagens I and III) were strikingly lower in treated allografts. In vitro, activated peritoneal macrophages of 13cRA-treated rats showed a pronounced decrease in protein secretion of inflammatory cytokines (eg, tumor necrosis factor-alpha, interleukin-6). The suppression of the proinflammatory chemokine RANTES/CCL5 x 13cRA in fibroblasts could be mapped to a promoter module comprising IRF-1 and nuclear factor-kappaB binding elements, but direct binding of retinoid receptors to promoter elements could be excluded. In summary, 13cRA acted as a potent immunosuppressive and anti-fibrotic agent able to prevent and inhibit progression of chronic allograft nephropathy.
Project description:PurposeMeibomian gland dysfunction (MGD) is a primary cause of dry eye disease. One of the risk factors for MGD is exposure to 13-cis retinoic acid (13-cis RA), a metabolite of vitamin A. However, the mechanism is not well understood. We hypothesize that 13-cis RA inhibits cell proliferation, promotes cell death, alters gene and protein expressions, and attenuates cell survival pathways in human meibomian gland epithelial cells.MethodsTo test our hypotheses, immortalized human meibomian gland epithelial cells were cultured with or without 13-cis RA for varying doses and time. Cell proliferation, cell death, gene expression, and proteins involved in proliferation/survival and inflammation were evaluated.ResultsWe found that 13-cis RA inhibited cell proliferation, induced cell death, and significantly altered the expression of 6726 genes, including those involved in cell proliferation, cell death, differentiation, keratinization, and inflammation, in human meibomian gland epithelial cells. Further, 13-cis RA also reduced the phosphorylation of Akt and increased the generation of interleukin-1β and matrix metallopeptidase 9.ConclusionsExposure to 13-cis RA inhibits cell proliferation, increases cell death, alters gene expression, changes signaling pathways, and promotes inflammatory mediator and protease expression in meibomian gland epithelial cells. These effects may be responsible, at least in part, for the 13-cis RA-related induction of MGD.
Project description:The 14-3-3 family of proteins interacts with various cellular phosphoproteins and regulates multiple cell signaling cascades. Identification of 14-3-3 interactors is important to define 14-3-3 functions in various biological pathways. The binding partners of protein 14-3-3 in testis are not known. The main goal of this study was to identify the 14-3-3 interactome in testis to determine the 14-3-3 regulated cellular processes in testis. We used transgenic mice expressing tandem affinity tagged 14-3-3ζ (TAP-14-3-3ζ) driven by the ubiquitin promoter to isolate 14-3-3 binding proteins. The 14-3-3 complexes in testis were isolated using a two-step tandem affinity purification (TAP) followed by identification with liquid chromatography/tandem mass spectrometry (LC-MS/MS). A total of 135 proteins were found to be associated with 14-3-3 in vivo in testis. Comparison of the testis 14-3-3 proteome with known 14-3-3 binding proteins showed that 71 of the proteins identified in this study are novel 14-3-3 interactors. Eight of these novel 14-3-3 interacting proteins are predominantly expressed in testis. The 14-3-3 interactors predominant in testis are: protein phosphatase1γ2 (PP1γ2), spermatogenesis associated 18 (SPATA18), phosphoglycerate kinase-2 (PGK2), testis specific gene A-2 (TSGA-2), dead box polypeptide 4 (DDX4), piwi homolog 1, protein kinase NYD-SP25 and EAN57. The fact that some of these proteins are indispensable for spermatogenesis suggests that their binding to 14-3-3 may be important for their function in germ cell division and maturation. These findings are discussed in context of the putative functions of 14-3-3 in spermatogenesis.
Project description:G-protein-coupled receptors (GPCRs) and other structurally and functionally related membrane proteins represent particularly attractive targets for drug discovery. Integral membrane proteins are often difficult to purify from native contexts, and lack of sufficient quantities hampers subsequent structural and functional proteomic studies. We describe here an optimized enrichment strategy involving a membrane protein-compatible 1D4 affinity tag that is derived from the carboxy-terminal nine amino residues of bovine rhodopsin, and its corresponding tag-specific, high-affinity monoclonal antibody. When two GPCRs as well as two related ATP binding cassette (ABC) transporters are expressed in their functional forms in human cell lines, we have shown that a single detergent and wash condition can be employed for the purification of all said membrane proteins. Subsequent in-gel digestion with trypsin and mass spectrometric peptide analysis resulted in high sequence coverage for the ABC transporters ABCA1-1D4 and ABCA4-1D4. In contrast, digestion by various enzymatic combinations was necessary to obtain the best sequence coverage for affinity-enriched GPCRs CXCR4-1D4 and CCR5-1D4 as compared against other entries in an annotated spectrum library. Furthermore, specific enzyme combinations were necessary to produce suitable peptides for deducing N-glycosylation sites on CXCR4. Our results demonstrate that the 1D4-tag enrichment strategy is a versatile tool for the characterization of integral membrane proteins that can be employed for functional proteomic studies.
Project description:1. Heparin, heparan sulphate, chondroitin sulphate and dermatan sulphate were covalently attached to beads of agarose activated by cyanogen bromide. The bond is probably mediated by the amino group of a serine or peptide residue at the reducing end of the polysaccharide chain. 2. The uptake of glycosaminoglycan during the coupling procedure is about 0.9mg/ml of wet gel. However, direct analysis of washed and freeze-dried gels reveals that only about one-third of this amount is firmly attached to the gel. 3. The use of the gels for polysaccharidase analyses is exemplified by a hyaluronidase assay. Further applications, e.g. interaction studies and preparative purposes, are discussed.
Project description:Ribosomes were separated by zonal ultracentrifugation from the fraction of reticulocyte postmitochondrial supernatants retained on heparin bound to Sepharose 4B at 4 degrees C. No ribosomes were retained at 22 degrees C. Ribosomes were also adsorbed on Sepharose 4B and 6B at low temperatures and could be eluted after increasing the column temperature.
Project description:The pathogenesis of acne has been linked to multiple factors such as increased sebum production, inflammation, follicular hyperkeratinization, and the action of Propionibacterium acnes within the follicle. 13-cis Retinoic Acid (13-cis RA, isotretinoin) is the most potent agent in acne treatment. Surprisingly, its mechanism of action in acne is still unknown. Gene expression profiling of cultured human immortalized sebocytes (SEB-1) treated with 13-cis RA was performed to gain insights into its sebocyte-specific mechanism of action. SEB-1 sebocytes were cultured with 0.1 uM 13-cis RA for 72 hours or vehicle control. Gene array expression profiling was conducted using Affymetrix HG-U95Av2 arrays in order to examine changes in gene expression as a result of treatment. A total of 85 genes (78 different genes) were significantly influenced by 13-cis RA: 58 were upregulated and 27 were down-regulated. There were changes in several genes involved in apoptosis and innate immunity. These studies are the first describing the sebocyte- specific response in gene expression associated with isotretinoin therapy and are valuable in identifying potential therapeutic targets in acne. Keywords: effects of 72 hour 13-cis RA treatment on cultured human sebocyte cells (SEB-1)