Methylamine Treatment Research Articles

Identification of C3 acceptors responsible for complement activation in Crithidia fasciculata.

Crithidia fasciculata, an insect trypanosomatid is readily lysed by normal human serum at concentrations as low as 3%. Lysis occurs in the presence of Mg+2-EGTA and is antibody independent, indicating that the alternative pathway of complement activation is involved. Analysis of [131I]C3 deposition on C. fasciculata cells using C8-deficient serum, revealed that about 4 x 10(5) C3 molecules bound to each cell. Most of the C3 was bound to cells as C3b, part of it forming high molecular weight complexes, which could be dissociated by methylamine treatment at alkaline pH. To characterize the C3 acceptors on C. fasciculata, surface-iodinated cells were incubated with C8D or heat-inactivated serum, extracted and immunoprecipitated with anti-C3 or anti-arabinogalactan antisera. Analysis of the immunoprecipitated material on SDS gels showed high-molecular weight components, which disappeared after methylamine treatment, giving rise to a component of 200 kDa molecular size. This 200-kDa component corresponded to a purified arabinogalactan complex, which was immunoprecipitated from labeled cell extracts, without incubation with C8D, using anti-arabinogalactan antibodies. These results suggest that the arabinogalactan glycoconjugate is a C3 acceptor in C. fasciculata during complement activation. Purified arabinogalactan complexes were able to inactivate C3 in vitro. Solubilization in KOH to cleave the peptide moiety rendered it unable to inactivate C3. Apparently, the aggregated state of the purified arabinogalactan component at the cell surface is important for C3 deposition and activation.

Purification and characterization of an α2-macroglobulin-like proteinase inhibitor from plasma of the crayfish Pacifastacus leniusculus

An alpha 2-macroglobulin (alpha 2M)-like proteinase inhibitor from plasma of the crayfish Pacifastacus leniusculus was purified to apparent homogeneity by acid precipitation, hydrophobic interaction chromatography, affinity chromatography on concanavalin A-Sepharose and anion-exchange chromatography. The subunit Mr is about 190,000. Pore-size-limit electrophoresis proved the native protein to be a dimer. The purified protein resembled vertebrate alpha 2 Ms in that it protected trypsin from inhibition by soyabean trypsin inhibitor, and in its sensitivity to methylamine treatment. Methylamine also prevented the protein from being autolytically cleaved into Mr 60,000 and 140,000 fragments when subjected to heat treatment. The amino acid composition showed similarities with both human alpha 2 M and an alpha 2 M-like protein from the arthropod Limulus polyphemus. These data indicate that this Pacifastacus alpha 2M-like protein (P alpha 2M) may be a distantly related homologue of vertebrate alpha 2Ms.

Conformational Changes of Alpha-Macroglobulin and Ovomacro-globulin from the Green Turtle (Chelonia mydas japonica)1

Green turtle plasma alpha-macroglobulin and ovomacroglobulin underwent conformational changes when they were treated with proteinases or methylamine. Their conformational changes were studied by HPLC gel chromatography, circular dichroism, and electron microscopy. The Stokes radii of native green turtle alpha-macroglobulin and ovomacroglobulin were estimated to be 84.3 +/- 0.5 A, and 93.0 +/- 0.5 A, respectively, by means of an HPLC experiment. After reaction with methylamine or proteinases, the Stokes radius of alpha-macroglobulin changed to 83.0 +/- 0.5 A or 85.4 +/- 0.5 A, respectively, and that of ovomacroglobulin to 93.0 +/- 0.5 A or 87.1 +/- 0.5 A. The circular dichroic spectra of native alpha-macroglobulin and ovomacroglobulin exhibited a negative band at around 215 nm, indicating the presence of beta-structure. Reaction of the two macroglobulins with methylamine resulted in a slight decrease in the ellipticity and reaction with proteinases led to a slight increase. The electron micrographic images of native alpha-macroglobulin and ovomacroglobulin can be described as deformed rings for the former and rugby balls for the latter. A common characteristic feature of the two molecules was that the central parts of the molecules were only thinly occupied by subunit. After reaction of macroglobulins with proteinases, the void spaces became partially filled and their overall shape more rectangular. Methylamine treatment caused a structural change only in alpha-macroglobulin but not in ovomacroglobulin. The difference in the susceptibility of the macroglobulins to methylamine was taken as an indication of evolutional divergence of the two homologous proteins within the last 300 million years.

Reduced gap junctional communication is associated with the lethal condition characteristic of DDK mouse eggs fertilized by foreign sperm.

Communication through gap junctions was examined in 8-cell zygotes generated by fertilization of eggs of the DDK inbred strain of mice with spermatozoa of the C3H strain. These zygotes spontaneously begin to extrude cells at the late 16-cell stage and 95% die by the blastocyst stage. The transfer of Lucifer Yellow between cells of DDK/C3H zygotes that had not yet begun to express the defect was significantly slower than in DDK/DDK controls or in controls from other strains. Treatment with the weak base methylamine, to raise intracellular pH, speeded the transfer of Lucifer in all strains; transfer between cells of DDK/C3H zygotes became as fast as that between cells of control zygotes. DDK/C3H zygotes cultured in methylamine either from the 4- to 8-cell stage to the early 16-cell stage (19h) or from the early to the late 16-cell stage (6 h) showed significant rescue to the blastocyst stage. Once spontaneous decompaction of cells from DDK/C3H zygotes had begun (the late 16-cell stage onwards) methylamine treatment was no longer able to bring about rescue. We conclude that zygotes developed from eggs of the DDK strain fertilized by foreign spermatozoa are characterized physiologically by defective gap junctional communication. Improving gap junctional communication is sufficient to allow many zygotes to maintain the compacted state, suggesting a link between compaction and communication through gap junctions.

Disruption of intracellular processing of epidermal growth factor by methylamine inhibits epidermal growth factor-induced DNA synthesis but not early morphological or transcriptional events.

Upon internalization, epidermal growth factor (EGF) is proteolytically processed from its COOH terminus as it traverses intracellular vesicles and lysosomes. This report describes experiments which were conducted to determine whether lysosomotropic amines such as methylamine, which are known to inhibit degradation of EGF, are able to significantly inhibit the COOH-terminal processing of EGF, and whether disruption of EGF processing would negatively affect EGF-stimulated events such as DNA synthesis and induction of specific mRNA species. The results of these experiments indicated that, whereas methylamine treatment had no effect on EGF binding or internalization, vesicular translocation from endocytic vesicles to lysosomes was halted and processing of EGF was severely inhibited. The stimulation of DNA synthesis beginning 12 h after EGF exposure was also markedly inhibited by methylamine treatment. However, addition of methylamine alone produced a non-specific inhibition of DNA synthesis. The ability of EGF to induce specific transcription of the rat transin gene within 6 h of treatment was also not inhibited by methylamine treatment, but was actually increased in the presence of methylamine. These results suggest that at least some early transcriptionally regulated events induced by EGF do not require vesicular processing of EGF (or its receptor) and that the signal transduced by the binding of EGF to its receptor occurs in, or proximal to, the endocytic vesicles.

Antigens of Complement Factor C3 Involved in the Interactions with Factors I and H

This study explores the relationship between defined antigens of the C3 molecule and those surface structures that are involved in interaction with factors I and H. Methylamine treatment at pH 11 followed by neutralization converts C3 into a modified state in which the molecule is optimally susceptible to cleavage by factor I in the presence of factor H. The modified C3 is characterized by an antigenic profile with expression of antigens of the C3(N), C3(S), and C3(D) subsets. These antigenic properties closely mirror those of physiologically bound C3b, suggesting that modification of antigenic expression upon denaturation of C3 reflects a regulatory mechanism for I and H function. Immunochemical studies of the alkaline-denatured C3 suggested that factor H interacts with surfaces of C3 that are situated within the C3c fragment and that are defined by C3(SN) antigens, while factor I predominantly interacts with C3(SN) antigens associated with the C3d fragment and with C3(D) antigens hidden in native C3. Therefore the continuing immunochemical study of this and related problems will require polyclonal and monoclonal antibody reagents reactive not only with the C3(S) and C3(N) but also the C3(D) antigenic subsets.

Unusual properties of crocodilian ovomacroglobulin shown in its methylamine treatment and sulfhydryl titration

The inhibitory activity of chicken and crocodilian ovomacroglobulins against trypsin was measured before and after their incubation with methylamine. The result for crocodilian ovomacroglobulin showed that methylamine treatment destroyed half of its activity, in unique contrast to human α 2-macroglobulin and chicken ovomacroglobulin for which methylamine either destroys the inhibitory activity of the former completely or does not affect that of the latter at all. Free sulfhydryl groups of chicken and crocodilian ovomacroglobulins were titrated with 5,5′-dithiobis(2-nitrobenzoic acid) before and after incubation with trypsin. Prior to the incubation with trypsin the chicken and crocodilian proteins respectively had 0 and 1 titratable sulfhydryl per molecule of M r 720,000. After treatment with trypsin the crocodilian protein had 3.5-4 titratable sulfhydryls, whereas there were no titratable sulfhydryls in the chicken protein. After denaturation of the crocodilian protein in sodium dodecyl sulfate at 100 °C the number of titratable sulfhydryls was 4. Chicken ovomacroglobulin again did not have an appreciable number of titratable sulfhydryls under similar denaturing conditions. Incubation of crocodilian protein with [ 14C]methylamine showed an incorporation of at least 2 mol of methylamine per molecule. The result indicated the presence of three intra-molecular thiol ester bonds in crocodilian ovomacroglobulin with differential stability against external perturbations.

A homologue of alpha 2-macroglobulin purified from the hemolymph of the horseshoe crab Limulus polyphemus.

A high molecular weight protease inhibitor has been purified from the cell-free plasma of the horseshoe crab Limulus polyphemus using high speed centrifugation, polyethylene glycol precipitation, and gel filtration. The inhibitor is sensitive to mild acidification, methylamine treatment, and inhibits the proteolytic activity of a variety of endopeptidases. The molecule does not inhibit trypsin-mediated hydrolysis of low molecular weight substrates and protects the active site of trypsin from inactivation by soybean trypsin inhibitor. These properties are diagnostic of the alpha 2-macroglobulin (alpha 2M) class of protease inhibitors found in vertebrates. Like vertebrate alpha 2M the Limulus alpha 2M molecule is composed of subunits of molecular weight 180,000-185,000 as determined by polyacrylamide gel electrophoresis under reducing conditions. The apparent native molecular weight for the Limulus molecule as determined by both gel filtration and gel electrophoresis under nonreducing conditions is 500,000-550,000, compared to a native molecular weight of 700,000-750,000 for human alpha 2M, determined in parallel under identical conditions. These results suggest that alpha 2M appeared in evolution at least 550 million years ago before the divergence of the lineages that gave rise to present-day arthropods and mammals.

Structural changes in alpha-2- and ovomacroglobulins studied by gel chromatography and electron microscopy

The structural change that occurs in alpha-2-macroglobulin upon its interaction with methylamine or chymotrypsin was studied by high-performance gel chromatography and electron microscopy. The result enabled us to estimate the Stokes radius of the protein as 8.8 nm and 7.9 nm before and after binding with the proteinase, respectively. The methylamine-treated protein also had the Stokes radius of 7.9 nm. Similar studies on the chicken and crocodilian ovomacroglobulins showed that these homologues of α 2-macroglobulin had Stokes radii of 9.2–9.3 nm and 8.5–8.7 nm before and after bidning with chymotrypsin. Their Stokes radii did not change as a result of the methylamine treatment. Electron micrographs of the native and altered forms of the three proteins are presented. This study introduces a simple and quantitative method to study the structural change of α 2-macroglobulin and its homologues.

Effect of amino acids and cycloheximide on changes caused by vinblastine, leupeptin and methylamine in the autophagic/lysosomal system of mouse hepatocytes in vivo

The number of autophagic vacuoles in hepatocytes of 24 h fasted mice in vivo increased manyfold following the administration of vinblastine, leupeptin and methylamine. The effect of each chemical is characterized by the predominance of a certain kind of vacuole. Vinblastine treatment is accompanied by a large proportion of vacuoles containing morphologically unaltered organelles, leupeptin causes preferential accumulation of dense and complex vacuoles, methylamine administration produces mostly large, electron-lucent, swollen vacuoles. The amounts of segregated and accumulated cytoplasmic material, expressed as percentage cytoplasm per hour, were 0.84%, 2.08% and 0.74% following vinblastine, leupeptin and methylamine treatment respectively. The actual rate of segregation was probably higher than this. Inhibition of degradation of the sequestered cytoplasmic material is proposed to be a main factor in the increase in the size of the autophagic/lysosomal compartment. Treatment with cycloheximide or exogenously added mixture of amino acids cut down the size of the autophagic/lysosomal system in control cells and strongly inhibited the accumulation caused by vinblastine, leupeptin and methylamine.

α 2-macroglobulin-like activity in plasma of the crayfish Pacifastacus leniusculus

1. 1. A protease inhibitor was present in the plasma of the crayfish Pacifastacus leniusculus. 2. 2. This inhibitor decreased the activity of several proteases when casein was used as a substrate, whereas chromogenic synthetic peptides were hydrolyzed by these proteases in the presence of crayfish plasma. 3. 3. Crayfish plasma protected trypsin from being inhibited by soybean trypsin inhibitor and methylamine treatment abolished this effect. 4. 4. The presented data give evidence that this protease inhibitor in crayfish plasma is an α 2-macroglobulin-like substance.

Purification of a lamprey complement protein homologous to the third component of the mammalian complement system.

A lamprey protein homologous to the third component of mammalian complement was isolated from lamprey plasma and was tentatively designated lamprey C3. Lamprey C3 is a major protein in lamprey serum with electrophoretic mobility of beta-globulin and with m.w. of 190,000. It consists of three polypeptide chains (84,000-alpha, 74,000-beta, and 32,000-gamma chains) linked by disulfide bonds. The protein retains a unique internal thiolester bond on the alpha-chain that is cleaved on methylamine treatment or on limited proteolysis with trypsin. Lamprey C3 by itself could not bind to zymosan or rabbit red cells, but it could covalently bind to these substances when activated by other factors present in lamprey serum. The binding of lamprey C3 to activating surfaces is mediated by covalent bonds and is accompanied by limited proteolysis of the alpha-chain. A fragment with an m.w. of 35,000 containing the internal thiolester site was isolated from methylamine-treated lamprey C3 bound to activated thiol-Sepharose by extensive tryptic digestion followed by dithiothreitol treatment. Lamprey C3 functions as the essential factor in phagocytosis of rabbit red cells by lamprey phagocytes. However, it is not involved in naturally occurring hemolytic activity in lamprey serum.

Kinetics of the conformational alterations associated with nucleophilic modification of alpha 2-macroglobulin.

The effect of nucleophilic modification of alpha 2-macroglobulin (alpha 2M) with methylamine on the kinetics of sulfhydryl exposure was investigated. The generated sulfhydryl groups were detected with 4,4'-dithiodipyridine. The bimolecular rate constant for sulfhydryl exposure was determined to be 11.6 +/- 0.8 M-1 s-1 at 30 degrees C and pH 8.0. Treatment of alpha 2-macroglobulin with methylamine or proteases, such as plasmin and trypsin, results in a substantial increase in the fluorescence of 6-(p-toluidino)-2-naphthalenesulfonic acid. This probe was used to monitor the kinetics of the conformational change occurring in alpha 2-macroglobulin upon treatment with methylamine. It was found that the conformational change did not occur simultaneously with the cleavage of the thiol ester bonds by the nucleophile but, rather, the conformational alterations occurred following a lag phase. The data are consistent with a mechanism requiring the random cleavage of two thiol ester bonds of a dimeric unit in the molecule prior to the unimolecular process representing the conformational change. According to this model, the two dimeric units present in alpha 2M act as independent entities. On the basis of the best fit with the model, the bimolecular rate constant, for hydrolysis of the thiol ester bonds, was determined to be 11.9 +/- 0.7 M-1 s-1, while the rate constant for the conformational change was (9.7 +/- 2.0) X 10(-3) s-1. The measured rate of conformational change is rate limited by thiol ester cleavage at lower methylamine concentrations. The conformational change, measured with this fluorescence probe, approximately parallels the loss of trypsin binding activity of alpha 2-macroglobulin, measured by resistance of the bound trypsin to soybean trypsin inhibitor. A much slower loss of plasmin binding activity was observed than was found for trypsin, suggesting that the structural requirements on alpha 2M for the interaction with plasmin are disrupted much more slowly than the structural requirements for trypsin binding upon methylamine treatment of the molecule.

An endopeptidase inhibitor, similar to mammalian alpha 2-macroglobulin, detected in the hemolymph of an invertebrate, Limulus polyphemus.

A protease inhibitory activity has been detected in the hemolymph of the horseshoe crab, Limulus polyphemus. The inhibitor possesses many of the characteristics of vertebrate alpha 2-macroglobulin. The inhibitor, found in the high speed supernatant of Limulus plasma, is sensitive to mild acidification, inhibits a variety of prokaryotic and eukaryotic endopeptidases, and is sensitive to methylamine treatment. Although the inhibitor completely prevents the trypsin-mediated hydrolysis of protein substrates, the hydrolysis of a low molecular substrate by trypsin is unaffected by the inhibitor, a property characteristic of alpha 2-macroglobulin. The striking similarity of the inhibitor to vertebrate alpha 2-macroglobulin, coupled with the fossil record of Limulus, suggests that such protease inhibitors are ancient molecules.

Functional modifications of alpha 2-macroglobulin by primary amines. Kinetics of inactivation of alpha 2-macroglobulin by methylamine, and formation of anomalous complexes with trypsin.

The unique steric inhibition of endopeptidases by human alpha(2)M (alpha(2)-macroglobulin) and the inactivation of the latter by methylamine were examined in relation to each other. Progressive binding of trypsin by alpha(2)M was closely correlated with the loss of the methylamine-reactive sites in alpha(2)M: for each trypsin molecule bound, two such sites were inactivated. The results further showed that, even at low proteinase/alpha(2)M ratios, no unaccounted loss of trypsin-binding capacity occurred. As alpha(2)M is bivalent for trypsin binding and no trypsin bound to electrophoretic slow-form alpha(2)M was observed, this indicates that the two sites must react (bind trypsin) in rapid succession. Reaction of [(14)C]methylamine with alpha(2)M was biphasic in time; in the initial rapid phase complex-formation with trypsin caused a largely increased incorporation of methylamine. In the subsequent slow phase trypsin had no such effect. These results prompted further studies on the kinetics of methylamine inactivation of alpha(2)M with time of methylamine treatment. It was found that conformational change of alpha(2)M and decrease in trypsin binding (activity resistant to soya-bean trypsin inhibitor) showed different kinetics. The latter decreased rapidly, following pseudo-first-order kinetics. Conformational change was much slower and followed complex kinetics. On the other hand, binding of (125)I-labelled trypsin to alpha(2)M did follow the same kinetics as the conformational change. This discrepancy between total binding ((125)I radioactivity) and trypsin-inhibitor-resistant binding of trypsin indicated formation of anomalous complexes, in which trypsin could still be inhibited by soya-bean trypsin inhibitor. Further examination confirmed that these complexes were proteolytically active towards haemoglobin and bound (125)I-labelled soya-bean trypsin inhibitor to the active site of trypsin. The inhibition by soya-bean trypsin inhibitor was slowed down as compared with reaction with free trypsin. The results are discussed in relation to the subunit structure of alpha(2)M and to the mechanism of formation of the complex.

Use of periodate and methylamine for the quantitation of intracellular 5-fluro-2′-deoxyuridine-5′-monophosphate by high-performance liquid chromatography

High-performance liquid chromatography was used for the quantitation of [ 3H]fluorouracil and metabolites in L1210 cells with or without pre-treatment with methotrexate. Ribonucleotide pools were evaluated on a chemically bonded anion-exchange column. Deoxynucleotide pools were determined following periodate and methylamine treatment which eliminated the ribonucleotides (>99.9% complete) and allowed for a rapid quantitation of the acid-soluble 5-fluoro-2′-deoxyuridine-5′-monophosphate (FdUMP) pools. FdUMP levels as low as 10 fmol/10 6 cells were detectable by polystyrene anion-exchange chromatography. Confirmation of these FdUMP values was performed by rechromatography on a reversed-phase ion-pair column. The use of periodate and methylamine as a means for the reliable elimination of the ribonucleotides will allow accurate isolation of deoxynucleotides by high-performance liquid chromatography.