Double staining of immunoblot using enzyme histochemistry and India ink

Short-term, high dose enzyme replacement therapy in sialidosis mice

Given the success of enzyme replacement therapy (ERT) in treating the systemic manifestations in a number of lysosomal storage disorders (LSDs), we evaluated the effect of ERT on the mouse model of sialidosis. This glycoproteinosis, which affects primarily the reticuloendothelial (RE) system, is caused by deficiency of lysosomal neuraminidase (NEU1) and consequent accumulation of sialylated glycoconjugates. NEU1 lacks a functional mannose-6-phosphate recognition marker and is not endocytosed by mammalian cells. However, the enzyme produced in insect cells has features that allow its effective uptake by RE cells and macrophages via the mannose receptor, and therefore represent an alternative method of therapy. In this study we tested the therapeutic efficacy of baculovirus (BV) expressed mouse neuraminidase (Neu1) in sialidosis mice. Four-week-old Neu1-/- mice were first injected intravenously with a single dose of the recombinant enzyme for assessment of the half-life of mannosylated Neu1 in vivo. Afterwards, a short-term ERT with a total of five enzyme injections over a 2-week period was performed for evaluation of phenotype correction. Neu1 infused alone or co-administered with its associated protein, protective protein/cathepsin A (PPCA) was effectively taken up by resident macrophages in many tissues. Restored Neu1 activity persisted for up to 4 days, depending on the tissue, and resulted in a significant reduction of lysosomal storage. However, beyond 2 weeks of treatment, ERT mice developed a severe immune response towards the exogenous Neu1 enzyme. These results may have important implications for ERT in sialidosis patients.

Targeting macrophages with baculovirus-produced lysosomal enzymes: implications for enzyme replacement therapy of the glycoprotein storage disorder galactosialidosis

Lysosomal storage diseases (LSDs) are monogenic disorders of metabolism caused by deficiency of hydrolytic enzymes. In several LSDs, cells of the reticuloendothelial (RE) system are the primary targets of the disease. Exogenous administration of recombinant enzymes overproduced in mammalian cells has proved effective for treating the systemic phenotype in nonneuropathic patients with LSDs. However, for the treatment of diseases with primary involvement of the RE system, the production of the therapeutic enzyme in insect cells could be an alternative and advantageous method because glycoproteins expressed in insect cells carry carbohydrates of the pauci-mannose or core-type. These recombinant enzymes are in principle already poised to be internalized by cells that express mannose receptors, including macrophages. Here, we demonstrate that three baculovirus-expressed enzymes, protective protein/cathepsin A (PPCA), neuraminidase (Neu1), and beta-glucosidase, were readily taken up and restored lysosomal function in enzyme-deficient mouse macrophages. The capacity of recombinant PPCA and Neu1 to clear the lysosomal storage in target cells was assessed in PPCA-/- mice, a model of galactosialidosis. Intravenously injected PPCA-/- mice efficiently internalized the corrective enzymes in resident macrophages of many organs. In addition, treated mice showed overall clearance of lysosomal storage in the most affected systemic organs, kidney, liver, and spleen. Our results suggest that ERT with baculovirus-expressed enzymes might be an effective treatment for nonneuropathic patients with galactosialidosis and possibly for others with LSDs that primarily involve the RE system.

The combination of Indian ink staining with immunochemiluminescence detection allows precise identification of antigens on blots: application to the study of glycosylated barley storage proteins

The localization after blotting of specific spots in two-dimensional electrophoretic protein pattern was achieved using, in that order, Indian ink protein staining and immunodetection with chemiluminescence on the same membrane. Indian ink did not inhibit significantly the antibody reactions even after overnight staining. It produces permanent staining that did not quench the chemiluminescent signal, recorded on a film. This allowed perfect matching between the specific and the total protein patterns. The procedure was applied to the identification of glycoproteins present in barley storage protein preparations.

Role of retinoic acid in regulation of mRNA expression of CaBP-D28k in the cerebellum of the chicken

In contrast to vitamin D3-dependent gene expression of calbindin (CaBP-D28k) in intestine and kidney, the cerebellar mRNA expression seems independent of vitamin D3. The present study was conducted to elucidate correlation of mRNA expression of CaBP-D28k and vitamin D3 receptor (VDR) in the kidney and cerebellum of the developing chick by Northern blot analysis, localization of CaBP-D28k mRNA within the cerebellum by in situ hybridization, and effect of retinoic acid in ovo on CaBP-D28k mRNA levels. CaBP-D28k mRNA levels were low in the cerebellum until embryonic day 16 (E16) but markedly increased on E18 and reached plateau levels on E20. VDR mRNA levels were low until E16 and significantly increased on E18 but decreased on E20 and remained low on 1 and 7 days after hatching. In the mesonephros, CaBP-D28k mRNA levels were high until E16 but abruptly decreased on E18, while VDR mRNA levels remained relatively constant throughout the examined period between E10 and 20. In situ hybridization analysis clearly demonstrated CaBP-D28k mRNA signals within the Purkinje cells of the cerebellum in the embryo on E12-E18. Although 1.25 dihydroxyvitamin D3 [1.25(OH)2D3, 3 x 10(-10) M injected in ovo on E15 increased CaBP-D28k mRNA levels in the mesonephros on E16 but had no effect on those in the cerebellum. On the contrary, in ovo injection of retinoic acid (10(-10) and 10(-8) M) caused no effect on CaBP-D28k mRNA levels in the mesonephros but significantly increased those in the cerebellum. The results indicate a regulatory role of retinoic acid on mRNA expression of CaBP-D28k in the cerebellar Purkinje cells of the chicken embryo.

Staining methods in gel electrophoresis, including the use of multiple detection methods

Polyacrylamide gel electrophoresis is a reliable and widely used technique for the separation, identification and characterization of proteins and protein mixtures. With the introduction of high resolution two-dimensional polyacrylamide gel electrophoresis in 1975 upward to 2000 individual polypeptides spots are easily separated on a single electrophoretic gel thereby necessitating the availability of highly sensitive protein detection methods. Although a plethora of protein-staining and -visualization protocols have been described utilizing both radioactive and non-radioactive reagents, many times the use of mono-dimensional detection procedures is insufficient to address the experimental questions asked. The present review highlights the utilization of combined protein-labeling and -staining methodologies in gel electrophoresis including selected applications in polyacrylamide gels and solid membrane matrixes.

Tissue-specific expression of calbindin-D28K gene during ontogeny of the chicken

The vitamin D3-dependent calcium binding protein, calbindin-D28K (CaBP-D28K), plays an important role in transepithelial calcium translocation. To evaluate its role in chick embryonic calcium metabolism, steady-state levels of CaBP-D28K mRNA in various tissues of the chick embryo were determined by Northern blot and slot blot analyses, and CaBP-D28K concentrations in the examined tissues and plasma were estimated by RIA. High levels of CaBP-D28K mRNA were found in the embryonic kidney (mesonephros) on embryonic day (E) 10 and E12 and thereafter gradually decreased until hatching. CaBP-D28K mRNA levels were low in the yolk sac until E16 but increased on E18 and reached a maximum on E20. A steady increase in CaBP-D28K mRNA levels was observed in the cerebellum during the development from E10 to post-hatching. CaBP-D28K mRNA levels in the intestine were very low during the incubation period but significantly increased on days 1 and 7 after hatching. By Northern blot analysis, CaBP-D28K mRNA was barely detectable in liver, heart, and chorioallantoic membrane of the embryonic chick. Changes in immunoreactive CaBP-D28K of each tissue paralleled observed changes in mRNA levels. In plasma, measurable levels of CaBP-D28K were found as early as E8 and were stable until E18, when 6.5-fold increase was observed compared to E16. The highest level of CaBP-D28K in plasma was found on E20 and decreased after hatching. These temporal profiles of CaBP-D28K suggest that it may play an important role in the regulation of chick embryonic calcium homeostasis.

Protein (western) blotting

The different steps involved in protein (Western) blotting and subsequent analysis of the proteins are reviewed. Electrophoretic separation of proteins, procedures of transfer to membranes, immunological and nonimmunological protein detection systems, and characterization of protein-nucleic acid and protein-protein interactions are described. Emphasis is on the sensitivity of the methods described and on possible variations that allow the individual steps of Western blotting to be adapted to specific questions.

Separation of proteins using cetyltrimethylammonium bromide discontinuous gel electrophoresis

The gel electrophoresis system presented here allows the separation of proteins with the concomitant retention of detectable native activities. The system, referred to as CAT gel electrophoresis, uses the detergent cetyltrimethylammonium bromide in combination with a discontinuous gel matrix to resolve protein mixtures into discrete bands. Many proteins retain detectable levels of native activity after CAT electrophoresis, and gel bands can be easily identified using assays based on specific enzymatic activities or binding characteristics. The ability to identify protein bands based on Both M(r) and activity in a single gel makes the CAT system a powerful adjunct to existing biochemical techniques.

Demonstration of feline and canine platelet glycoproteins by immuno- and lectin histochemistry

Canine and feline platelet cytocentrifuge preparations (CCPs), cryostat and paraffin-embedded bone marrow sections were used in this study. We evaluated whether platelets, megakaryocytes and megakaryocyte precursor cells could be labelled by monoclonal antibodies (Y2/51, CLB-thromb/1, HPL1) against human platelet membrane glycoprotein GP IIIa and the GP IIb/IIIa complex or by the following 10 biotinylated lectins: concanavalin A (Con A), Lens culinaris agglutinin (LCA), Pisum sativum agglutinin (PsA), wheat germ agglutinin (WGA), peanut agglutinin (PNA), Phaseolus vulgaris lectin (PHA-L), Ricinus communis agglutinin 120 (RCA120), Ulex europaeus agglutinin-I(UEA-1), soybean agglutinin (SBA) and Dolichos biflorus agglutinin (DBA). Monoclonal antibodies Y2/51 and HPL1 cross reacted with platelets and megakaryocytic cells from both species, whereas CLB-thromb/1 was unreactive with canine preparations. Only Y2/51 labelled megakaryocytic cells in paraffin-embedded samples. LCA, PSA, WGA and PHA-L labelled feline and canine platelets and different numbers of morphologically identifiable megakaryocytes and numerous other, mostly myeloid, cells. Immunoblots of dog and cat platelet lysates using Y2/51 visualized a single protein of 95 kDa (unreduced), a mol.wt value within the range of those reported for GP IIIa. Some of the platelet (but not necessarily megakaryocyte) glycoproteins reacting with LCA, PSA and WGA could be identified in lectin blots following one- or two (nonreduced/reduced)-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Thus in dogs and cats, the immunohistochemical detection of GP IIIa (and eventually GP IIb/IIIa) rather than lectin binding patterns could be important for the diagnosis of megakaryoblastic leukaemias.

Immunochemical identification of LMW subunits of glutenin associated with bread-making quality of wheat flours

A murine monoclonal antibody (IFRN 0067), one of a library developed against prolamin fractions fromTriticum aestivum, has been characterised using a combination of immunoassay and immunoblotting techniques. The antibody was specific for two glutenin polypeptides which appeared by 2-dimensional electrophoresis to belong to the B group of LMW subunits. From results of antibody-binding studies with material extracted from genetic stocks, it was deduced that the target polypeptides were encoded on the short arm of chromosome 1D. The antibody was used in an immunoassay of bread wheats with a range of anticipated baking scores and for flours of known baking performance. Significant correlations were found between immunoassay and test-bake results. Indeed, correlation of IFRN 0067 binding with loaf volume was equal or better than that provided by alveograph parameters. The results provide evidence that LMW subunits contribute to the bread-making properties of wheat glutenin, as identified by the use of immunological techniques. The use of particular monoclonal antibodies, such as IFRN 0067, in the further development of simple, rapid diagnostic tests for flour quality predictions is discussed.

Two-dimensional electrophoresis of cat sera: protein identification by cross reacting antibodies against human serum proteins

After two-dimensional electrophoresis of cat serum, individual proteins were identified by means of cross reacting antibodies against the human protein homologues. Testing by cross reactivities seemed the method of choice because immunoreagents for cat proteins are not easily available.

Vitamin D and chick embryonic yolk calcium mobilization: identification and regulation of expression of vitamin D-dependent Ca2(+)-binding protein, calbindin-D28K, in the yolk sac

The developing chick embryo acquires calcium from two sources. Until about Day 10 of incubation, the yolk is the only source; thereafter, calcium is also mobilized from the eggshell. We have previously shown that during normal chick embryonic development, vitamin D is involved in regulating yolk calcium mobilization, whereas vitamin K is required for eggshell calcium translocation by the chorioallantoic membrane. We have studied here the biochemical action of 1,25-dihydroxy vitamin D3 in the yolk sac by examining the expression and regulation of the cytosolic vitamin D-dependent calcium-binding protein, calbindin-D28K. Two types of embryos are used for this study, normal embryos developing in ovo and embryos maintained in long-term shell-less culture ex ovo, the latter being dependent solely on the yolk as their calcium source. Our findings are (1) calbindin-D28K is expressed in the embryonic yolk sac, detectable at incubation Days 9 and 14; (2) the embryonic yolk sac calbindin-D28K resembles that of the adult duodenum in both molecular weight (Mr 28,000) and isoelectric point, as well as the presence of E-F hand Ca2(+)-binding structural domains; (3) systemic calcium deficiency caused by shell-less culture of chick embryos results in enhanced expression of calbindin-D28K in the yolk sac during late development; (4) yolk sac calbindin-D28K expression is inducible by 1,25-dihydroxy vitamin D3 treatment in vivo and in vitro; and (5) immunohistochemistry revealed that yolk sac calbindin-D28K is localized exclusively to the cytoplasm of the yolk sac endoderm. These findings indicate that the chick embryonic yolk sac is a genuine target tissue of 1,25-dihydroxy vitamin D3.