Increase in the number of atrial natriuretic hormone receptors in regenerating rat liver

Forty-eight hours after partial (approximately 67%) hepatectomy the activity of the particulate guanylate cyclase was increased by 2-fold in the regenerating rat liver. This increase was not an artifact of membrane isolation procedures, and as determined by 125I-labeled Tyr-28 atrial natriuretic hormone-(1-28) ANF binding, was accompanied by a 2-fold increase in the number of ANF receptors. The Kd of the receptors in membranes of regenerating livers was not significantly different from the Kd of the receptors in livers of sham-operated rats. The linear synthetic descysteine analog of ANF, analog I, which binds only to the 66-kDa receptors, displaced approximately 40% of the specifically bound 125I-ANF in liver membranes from both hepatectomized and sham-operated (control) animals. Affinity cross-linking studies with 125I-ANF confirmed the increase in the 116-kDa ANF receptor in membranes of regenerating livers. In perfused livers derived from control and hepatectomized animals, the basal rates of cGMP production were not significantly different. However, atriopeptin II-stimulated cGMP production was twice as great in regenerating livers as compared with controls. These data demonstrate that the increase in particulate guanylate cyclase activity observed during liver regeneration is due to an increase in the 116-kDa ANF receptor-associated activity. Additionally, our data demonstrate that the regenerating rat liver may be a valuable model with which to study the role of the hepatic ANF receptor/particulate guanylate cyclase.

Localization of protective epitopes within the pilin subunit of the Vibrio cholerae toxin-coregulated pilus

From a collection of monoclonal antibodies (MAbs) that recognize the native structure of the toxin-coregulated pilus of Vibrio cholerae, two protective MAbs (16.1 and 169.1) were used to localize the corresponding epitopes on the pilus. These MAbs were shown to specifically recognize the carboxyl half of the TcpA pilin subunit, as determined by their recognition of proteolytic fragments and hybrid pilin proteins. The positions of the epitopes were precisely determined through the use of overlapping synthetic peptides corresponding to this region of the pilin. The MAbs were found to recognize adjacent peptides, delineating a region between residues 157 and 199. Since the protective nature is specific for these two antibodies, the findings suggest that this region defines a domain that participates in toxin-coregulated pilus-mediated colonization and therefore represents a target for studies of its potential as an immunogen for incorporation into a component cholera vaccine.

Stimulation of fibroblast chemotaxis by human recombinant tumor necrosis factor alpha (TNF-alpha) and a synthetic TNF-alpha 31-68 peptide

Macrophages are a major source of fibrogenic factors that promote healing of injured tissue. The recruitment of fibroblasts to sites of tissue injury is a prerequisite for optimal repair of tissue damage. In the present study, human recombinant tumor necrosis factor alpha (hrTNF-alpha), a major macrophage-derived cytokine, was demonstrated to be a potent fibroblast chemoattractant, inducing migration at picomolar concentrations. Anti-hrTNF-alpha monoclonal antibody neutralized most of the fibroblast chemotactic activity generated during short-term culture of human peripheral blood monocytes stimulated with bacterial lipopolysaccharide, suggesting that TNF-alpha is a major monocyte-derived fibroblast chemoattractant. The portion of the human TNF-alpha molecule responsible for its chemotactic stimulation of fibroblasts appears to reside in residues 31-68. This region is highly conserved between TNF-alpha and lymphotoxin. This peptide is not only itself chemotactic but is also able to block the chemotactic response of fibroblasts to hrTNF-alpha and vice versa, suggesting that they each mediate fibroblast migration through similar mechanisms. These data further underscore the potential importance of TNF-alpha in modulating a variety of fibroblast functions, including chemotaxis and synthesis of collagen, glycosaminoglycans, interleukin 1 alpha (IL-1 alpha) and -beta, human histocompatibility leukocyte antigen A and B antigens, collagenase, prostaglandin E2, and IL-6.

The amino-terminal 29- and 72-Kd fragments of fibronectin mediate selective monocyte recruitment

Proteolytic fragments of fibronectin (Fn) can possess properties not inherent to intact Fn. Previously, only mixtures of low molecular weight Fn fragments, and the 120-Kd fibroblastic cell-binding segment, but not intact Fn, were shown to be selectively chemotactic for human monocytes (MOs). In order to determine if other structural domains of Fn were responsible, we tested six Fn fragments. The amino-terminal 72-Kd fragment at 1.5 microns was about 75% as potent as zymosan-activated serum (ZAS). Its amino-terminal 29-Kd degradation product at 1.0 micron was about one third as potent as ZAS. Checkerboard analysis confirmed chemotaxis. Complexing gelatin to 72-Kd fragments reduced MO chemotaxis by 28% to 30%. Reducing disulfide bonds in 29- and 72-Kd segments had no effect. A synthetic peptide containing the thrombin cleavage site between the 29- and 50-Kd segments of the 72-Kd fragment was chemotactic. The 50-, 190/170-, 35-, and 160/150/120-Kd fragments, and intact Fn were not chemotactic for MOs. The data suggest that the 72-Kd fragment and its 29-Kd subfragment are additional Fn fragments that mediate selective MO chemotaxis. We speculate that proteinases present at inflammatory sites can liberate such fragments that selectively recruit MOs.

Interleukin 1 alpha and an interleukin 1 beta fragment are somnogenic

The somnogenic activity of interleukin 1 beta (IL-1 beta) has previously been established. Interleukin 1 alpha (IL-1 alpha) is a distinct gene product that possesses similar biological activities. We report here that IL-1 alpha, like IL-1 beta, has the capacity in rabbits to enhance non-rapid-eye-movement sleep, electroencephalographic slow-wave (0.5-3.5 Hz) voltages, and body temperatures and to inhibit rapid-eye-movement sleep. After IL-1 alpha, sleep remained episodic, and at the doses used no abnormal behavior was observed. Several synthetic IL-1 alpha and IL-1 beta peptides were also tested in vivo for somnogenic and pyrogenic activity and in vitro for their ability to stimulate prostaglandin E2 (PGE2) production by fibroblasts and proliferation of T-cells. Only IL-1 beta-(208-240) enhanced non-rapid-eye-movement sleep and body temperature, although both IL-1 beta-(208-240) and IL-1 alpha-(223-250) stimulated PGE2 production; both of these peptides failed to stimulate T-cell production. In contrast, four other IL-1 peptides were nonpyrogenic and somnogenically inactive yet stimulated T-cell proliferation. We conclude that the components of IL-1 required for sleep and temperature activities are different from those required for T-cell proliferation.

A factor from damaged rat kidney stimulates collagen biosynthesis by mesangial cells

Rats were administered CCl4, a well-defined nephrotoxin, for 20 weeks to produce glomerular sclerosis. Tubular degeneration and necrosis with interstitial fibrosis was clearly evident by histological examination. Kidneys were homogenized in phosphate-buffered saline and a collagen synthesis-stimulating factor was isolated by Sephadex G-50 gel filtration. The 5 kDa component stimulated both type I and type IV procollagen synthesis by mesangial cells and type I procollagen synthesis by rat skin fibroblasts. In each cell type, 2-6-fold increases in procollagen protein production or cell proliferation was noted. The steady-state levels of mRNA encoding for procollagen alpha 1(I) and procollagen alpha 1(IV) chains in mesangial cells were determined by by hybridization to their corresponding cDNA clones. The type I procollagen mRNA was elevated 1.4-fold compared to a 1.6-fold increase in mRNA encoding for type IV procollagen. The similar properties and chemical characteristics of this fibrogenic factor with a factor from fibrotic liver suggests they are the same and that a common endogenous collagen synthesis stimulator may be present in fibrosing organs, thus providing a driving force for collagen over-production.

Comparison and accuracy of methodologies employed for analysis of hydropathy, flexibility and secondary structure of proteins

Various methods have been developed recently for predicting antigenic determinants in a protein by analyzing its hydropathicity, flexibility or secondary structure. The predicted results by these methods were compared directly to the observed structure of the proteins to determine how accurate they were. Regression and correlation of the predicted hydropathicity versus the observed solvent accessibility and the predicted chain flexibility versus actual mobility were determined. Three separate methods of hydropathic analysis had correlation coefficients of 0.52, 0.63 and 0.57 respectively, while a published method for chain flexibility analysis had a 0.19 correlation coefficient. Similarly, agreement between the observed and the predicted secondary structures by two methods was also determined. The limitations of these techniques were clearly defined.

Regulation of TGF beta gene expression in rat liver intoxicated with carbon tetrachloride

Transforming growth factor beta (TGF beta) has been implicated as having a central role in the postinflammatory tissue regeneration and fibrosis. To test its potential involvement in events that follow hepatotoxin-mediated liver regeneration and fibrosis, we quantitated changes in the steady-state levels of TGF beta mRNA in parenchymal and nonparenchymal cells at various times after an acute treatment with CCl4, and also compared TGF beta gene expression in these two cell types from livers subjected to chronic CCl4 treatment. The parenchymal and nonparenchymal cells from normal liver contained undetectable amounts of TGF beta mRNA. In contrast, we could readily detect TGF beta specific transcripts in both the parenchymal and nonparenchymal cells after acute injury. Nonparenchymal cells from acutely injured liver contained fivefold greater amounts of TGF beta mRNA, which peaked at 48 h and declined thereafter. In chronically treated rat livers (1, 2, 3, and 7 wk after the initiation of CCl4 treatment), increased expression of TGF beta mRNA was found only in nonparenchymal cells obtained after 2-3 wk of treatment. Strikingly large elevations in the steady-state levels of beta-actin mRNA in CCl4-treated liver were also observed, which may be related to the known regenerative processes associated with acute liver toxicity. Changing dynamics of TGF beta gene expression, therefore, appear to be an important attribute of regenerating liver after acute or chronic CCl4 toxicity.

Identification of insulin intermediates and sites of cleavage of native insulin by insulin protease from human fibroblasts

We have studied the time sequence degradation of native insulin by insulin protease from human fibroblast using multiple steps involving purification of the products by high performance liquid chromatography, determination of peak composition by amino acid sequence analysis, and confirmation of structure by mass spectrometry and thus elucidated the sites of cleavage of insulin by human insulin protease. We observed that as early as 0.5 min of incubation, three major new peptide peaks, intact insulin, and four smaller peptide peaks can be detected. The major peptides are portions of the insulin molecule, with the amino ends of the A and B chains or the carboxyl ends of the A and B chains still connected by disulfide bonds. Peptide peak I is A1-13-B1-9. Peptide peak II is A1-14-B1-9. Peptide peak III is A14-21-B14-30. The smaller peptide peaks are A14-21-B17-30, A15-21-B14-30, A15-21-B10-30, and A14-21-B10-30. The major peptide bond cleavage sites therefore consist of A13-14, A14-15, B9-10, B13-14, and B10-17. With longer incubation times, peptide peak II appears to lose the A14 tyrosine to form peptide peak I. This peptide I, which is the amino end of the A and B chains, is not further degraded even after 1.5 h of incubation. With longer incubation times, the peptides containing the carboxyl ends of the A and B chains are further degraded to form products from cleavage at the A18-19, B14-15, B25-26, and a small amount of A19-20, B10-11, and B24-25 cleavage and the emergence of 2-5-amino acid peptide chains, tyrosine, alanine, histidine, and leucine-tyrosine. We conclude, based on the three-dimensional structure of insulin, that human insulin protease recognizes the alpha-helical regions around leucine-tyrosine bonds and that final degradation steps to small peptides do not require lysosomal involvement.

Identification of an immunosuppressive epitope of type II collagen that confers protection against collagen-induced arthritis

We have previously reported that collagen-induced arthritis can be suppressed by intravenous injection of native type II (CII) but not type I collagen. We have now identified denatured fragments of CII capable of suppressing collagen-induced arthritis and inducing tolerance. Purified CII was cleaved with cyanogen bromide (CB), and the major resulting peptides were isolated. Female DBA/1 mice were administered OVA, native CII, or one of the CB peptides, intravenously, before immunization with native CII, 6 wk after immunization, mice tolerized with CII and CB11 had a markedly lower incidence of arthritis compared with controls. There was a correlation between the overall antibody response and the incidence of arthritis. In addition, animals tolerized with either CII or CB11 had a decreased antibody response not only to CII, but also to each of the other CB peptides tested. To identify the epitope involved in suppression of arthritis, five synthetic peptides, 21-26 amino acids in length, corresponding to selected regions of CB11, were generated. Each of the peptides was injected intravenously into mice before immunization. Only one of these, CB11 122-147, was capable of suppressing arthritis. In addition, mice given the synthetic peptide CB11 122-147 neonatally were suppressed for arthritis and antibody responsiveness when immunized with CII at 8 wk of age. Thus, we have identified CB11 122-147 as an epitope of CII important in induction of tolerance and suppression of disease. Further experiments narrowing down the pivotal amino acids for the immunogenicity of this epitope and the role this epitope plays in induction and regulation of disease will enhance our understanding of how the immune response to collagen affects autoimmune arthritis.

Vimentin-cross-reactive epitope of type 12 streptococcal M protein

The NH2-terminal amino acid sequence of type 12 M protein was determined by automated Edman degradation of a 38-kilodalton polypeptide fragment purified from a limited pepsin digest of intact type 12 streptococci. The sequence of the first 13 amino acid residues of the polypeptide confirmed that predicted by the nucleotide sequence of the mature type 12 M protein. A chemically synthesized peptide copying the NH2-terminal 25 residues, SM12(1-25)C, evoked opsonic antibodies against type 12 streptococci as well as renal glomerular cross-reactive antibodies. The serum from one of six rabbits reacted in immunofluorescence tests with human glomeruli in a mesangial staining pattern. The cross-reactive antibodies were completely inhibited by the immunizing peptide and absorption with type 12 streptococci. Subpeptides of the 25-residue synthetic peptide were without inhibitory effect, suggesting that the cross-reactive antibodies are directed against a conformational epitope of SM12(1-25)C. Anti-SM12(1-25)C antisera reacted specifically with the intermediate filament protein vimentin extracted from mesangial cells. None of the cross-reactions of anti-SM12(1-25)C were inhibited by a synthetic peptide SM1(1-26)C of type 1 M protein, which was previously shown to share a cross-reactive epitope with vimentin. These results indicate that type 12 M protein contains at least one vimentin cross-reactive epitope that is clearly distinct from the tetrapeptide epitope shared with vimentin by type 1 M protein.

Covalent structure of collagen: amino acid sequence of three cyanogen bromide-derived peptides from human alpha 1(V) collagen chain

Type V collagen was prepared from human amnionic/chorionic membranes and separated into alpha 1(V) and alpha 2(V) polypeptide chains. The alpha 1(V) chain was digested with cyanogen bromide and nine peptides were obtained and purified. Three of the peptides, alpha 1(V)CB1, CB4, and CB7 having molecular weights of 5000, 8000, and 6000, respectively, were further analyzed by amino acid sequence analysis and thermolytic or tryptic digestions. CB1 contained 54 amino acids and identification of its complete sequence was aided by thermolysin digestion and isolation of two peptides, Th1 and Th2. CB4 contained 81 amino acids and sequence analysis of intact CB4 and five tryptic peptides provided us with its complete amino acid sequence. The peptide CB7 contained 67 amino acids and was cleaved into four tryptic peptides that were used for complete sequence analysis. The above results represent the first available covalent structure information on the alpha 1(V) collagen chain. These data enabled us to establish the location of these peptides within the helical structure of other collagen chains. CB4 was homologous to residues 66-145 in the collagen chain while CB1 represented residues 146-200 and CB7 was homologous with residues 201-269. This alignment was facilitated by identification of a helical collagen crossing site consisting of Hyl-Gly-His-Arg located at positions 87-90 in all collagen chains of this size thus far identified. Seventy-one percent homology (excluding Gly residues) was found between amino acids in this region of the alpha 1(XI) and of alpha 1(V) collagen chains while only 21 and 19% identity was calculated for the same region of alpha 2(V) and alpha 1(I) collagen chains, respectively.

Covalent structure of collagen. Amino acid sequence of an arthritogenic cyanogen bromide peptide from type II collagen of bovine cartilage

Bovine articular type II collagen was prepared by limited pepsin digestion, differential salt fractionation and carboxymethylcellulose chromatography. Cyanogen bromide digestion of purified type II collagen alpha chains yielded twelve distinct peptides designated CB1-12. The peptide alpha 1(II)-CB11 was isolated by carboxymethylcellulose chromatography and Sephadex G-75S gel filtration. Automated Edman degradation together with chymotrypsin, thermolysin and trypsin digestion enabled identification of its complete amino acid sequence. Compared with type I and type III collagen, the data show similarity with alpha 1(I)-CB8 and alpha 1(III)-CB6-1-8-10-2 peptides, respectively. The peptide is located within residues 124-402 of the alpha 1(II) collagen chain and with its identification, now extends the known amino acid sequence of bovine type II cartilage collagen to 660 amino acid residues including alpha 1(II)-CB1-2-6-12-11-8-10 (partial). This corresponds to alpha 1(I)-CB0-1-2-4-5-8-3-7 (partial; 1-660) and alpha 1(III)-CB3A-3B-3C-7-6-1-8-10-2-4-5 (partial; 1-660) of bovine alpha 1(I) and alpha 1(III) collagen chains.

Stimulation of glycosaminoglycan synthesis in cultured human dermal fibroblasts by interleukin 1. Induction of hyaluronic acid synthesis by natural and recombinant interleukin 1s and synthetic interleukin 1 beta peptide 163-171

Hyaluronic acid (HA) is believed to play a critical role in wound healing and in morphogenesis. Factors controlling the production of HA by fibroblasts in normal and pathological states are not completely understood. In this report we have observed that natural human interleukin (IL-1)1 beta and human recombinant (hrIL)-1 alpha and beta are potent stimulators of HA production by fibroblasts in vitro. Hyaluronic acid is the major species of glycosaminoglycan (GAG) stimulated by IL-1 in fibroblasts. PGE2 does not appear to be involved directly in this IL-1 effect on fibroblasts, but stimulation of HA production by IL-1 is dependent on protein synthesis. The synthetic human IL-1 beta peptide 163-171 (Val-Gln-Gly-Glu-Glu-Ser-Asn-Asp-Lys), which has been previously shown to stimulate thymocyte proliferation but not fibroblast PGE2 production, is also able to stimulate fibroblast HA production. The synthesis and secretion of IL-1 by mononuclear phagocytes at sites of inflammation and immune reactions in vivo could potentially serve as a signal for fibroblasts to synthesize HA, which in turn could serve to facilitate and modulate reparative and immune processes by virtue of its ability to alter cell-cell, cell matrix, and cell-membrane receptor interactions.

Cysteine 288: an essential hyperreactive thiol of cytosolic phosphoenolpyruvate carboxykinase (GTP)

Phosphoenolpyruvate carboxykinase from the cytosol of rat liver has 13 cysteines, at least one of which is known to be very reactive and essential for catalytic activity (Carlson, G. M., Colombo, G., and Lardy, H. A. (1978) Biochemistry 17, 5329-5338). In order to identify the essential cysteine, this enzyme was modified with the fluorescent sulfhydryl reagent N-(7-dimethylamino-4-methyl-3-coumarinyl)maleimide. Incubation of phosphoenolpyruvate carboxykinase with a 10% molar excess of this maleimide at 0 degrees C results in the rapid and nearly complete loss of catalytic activity. Under these conditions, 1 mol of the maleimide is incorporated per mol inactivated enzyme. The substrate GDP provides almost complete protection against inactivation and modification, while phosphoenolpyruvate protects against the rate, but not the extent, of modification. The pH dependence of the rate of enzyme inactivation suggests that the modified residue has a pK alpha of approximately 7.0. Purification and sequencing of the labeled peptide identifies the hyperreactive essential cysteine as Cys-288. This cysteine lies between two putative phosphoryl-binding domains and within a hydrophobic sequence.

Collagens of normal and cirrhotic human liver

The collagens of normal and end-stage alcoholic cirrhotic human liver were investigated. Mild conditions of pepsin digestion were employed to preserved the more pepsin sensitive type IV collagen molecules while increasingly more harsh conditions were used which solubilized the type I and type III hepatic collagens. The total hepatic collagen content was elevated from 1.8-2.1 in normal liver to 7.3-8.2 percent in the end-stage alcoholic liver. The graded pepsin digestion resulted in solubilization of 76-90 percent of the total hepatic collagen. The genetically distinct types of collagen were fractionated into types I, III, IV and V preparations using judicious salt precipitation from dilute acid and neutral pH solutions. The average distribution of collagen was 42.5, 39.5, 6.9 and 10.6 percent types I, III, IV and V collagen respectively in normal liver compared to 56.6, 28.0, 5.5 and 9.6 percent respectively in the end-stage alcoholic livers. An additional 0.6 and 0.5 percent in normal and end-stage cirrhotic liver respectively were located in a fraction separating out of the salt concentration required for type VI collagen. The type IV collagen of basement membrane was separated into the constituent 95Kda alpha 1(IV) and alpha 2(IV) polypeptide chains by Agarose A 5m gel filtration with subsequent (carboxymethyl) CM-cellulose chromatography. These chains were indistinguishable from similar chains of type IV collagen isolated previously from human placenta. The type V collagen alpha chains, alpha 1(V) and alpha 2(V) were purified by a combination of Diethylaminoethyl (DEAE) and CM-cellulose chromatography. The individual chains were fragmented with cyanogen bromide to yield 9 peptides from the alpha 1(V) chain and 10 peptides from the alpha 2(V) collagen chain. These were purified and analyzed for amino acid content and molecular weight. The study suggests that all collagen types were elevated in the end-stage alcoholic liver, but type I collagen was disproportionately increased over all other collagens. These results are consistent with previous studies which demonstrated an elevated type I collagen in other fibrotic conditions such as lung fibrosis and hypertrophic scar. They do not, however, agree with the suggested disproportionate elevation of type V collagen in human alcoholic liver. The reasons for this discrepancy are discussed.

Modulation of fibroblast functions by interleukin 1: increased steady-state accumulation of type I procollagen messenger RNAs and stimulation of other functions but not chemotaxis by human recombinant interleukin 1 alpha and beta

Interleukin-1 (IL-1) is synthesized by and released from macrophages in response to a variety of stimuli and appears to play an essential role in virtually all inflammatory conditions. In tissues of mesenchymal origin (e.g., cartilage, muscle, bone, and soft connective tissue) IL-1 induces changes characteristic of both destructive as well as reparative phenomena. Previous studies with natural IL-1 of varying degrees of purity have suggested that it is capable of modulating a number of biological activities of fibroblasts. We have compared the effects of purified human recombinant (hr) IL-1 alpha and beta on several fibroblast functions. The parameters studied include cell proliferation, chemotaxis, and production of collagen, collagenase, tissue inhibitor of metalloproteinase (TIMP), and prostaglandin (PG) E2. We observed that hrIL-1s stimulate the synthesis and accumulation of type I procollagen chains. Intracellular degradation of collagen is not altered by the hrIL-1s. Both IL-1s were observed to increase the steady-state levels of pro alpha 1(I) and pro alpha 2(I) mRNAs, indicating that they exert control of type I procollagen gene expression at the pretranslational level. We found that both hrIL-1 alpha and beta stimulate synthesis of TIMP, collagenase, PGE2, and growth of fibroblasts in vitro but are not chemotactic for fibroblasts. Although hrIl-1 alpha and beta both are able to stimulate production of PGE2 by fibroblasts, inhibition of prostaglandin synthesis by indomethacin has no measurable effect on the ability of the IL-1s to stimulate cell growth or production of collagen and collagenase. Each of the IL-1s stimulated proliferation and collagen production by fibroblasts to a similar degree, however hrIL-1 beta was found to be less potent than hrIL-1 alpha in stimulating PGE2 production. These observations support the notion that IL-1 alpha and beta may both modulate the degradation of collagen at sites of tissue injury by virtue of their ability to stimulate collagenase and PGE2 production by fibroblasts. Furthermore, IL-1 alpha and beta might also direct reparative functions of fibroblasts by stimulating their proliferation and synthesis of collagen and TIMP.

Isolation of cDNA clones and genomic DNA clones of beta-subunit of chicken prolyl 4-hydroxylase

Prolyl 4-hydroxylase (EC 1.14.11.2) is a key enzyme in collagen biosynthesis. The active enzyme is a tetramer composed of two pairs of non-identical subunits, alpha and beta. Sheep antiserum directed against chicken proly 4-hydroxylase was initially used to screen two cDNA expression libraries. The cDNA was prepared from chicken smooth muscle mRNA and cloned into the plasmids pUC8- and pUC9. Antibodies identified twenty-five clones among the approximately 2 x 10(5) clones in the libraries. Ten clones were isolated pure and used in the subsequent analysis. Monospecific antibodies directed against beta subunit of the enzyme were used in Western-blot analyses of extracts of bacteria carrying the cDNA clones. The results indicated that the clone CPH 9-10B encodes a portion of beta-subunit. The cDNA from CPH 9-10B was used to screen another cDNA library prepared from mRNA from chicken skeletal muscle. Several overlapping clones were isolated. Together the cDNAs correspond to 2.4 kb which is the same as the corresponding mRNA. Three regions of the amino acid sequence deduced from the cDNA sequence matched with that of the NH2-terminus of beta-subunit and two CNBr peptides derived from beta-subunit. The cDNA of CPH 9-10B was also used to screen a genomic DNA library constructed with lambda EMBL-3. Two overlapping genomic clones lambda gCPH beta-22 and beta-50 were isolated and characterized by restriction enzyme analysis. The results indicate that lambda gCPH beta-22 contains the portion of the beta-subunit gene that is transcribed into the 5' portion of beta-subunit mRNA, whereas lambda gCPH beta-50 contains the 3' portion.

Sequence and type-specific immunogenicity of the amino-terminal region of type 1 streptococcal M protein

The NH2-terminal sequence of type 1 M protein was determined by automated Edman degradation of purified polypeptide fragments extracted from whole streptococci by limited digestion with pepsin. Three polypeptide fragments were purified by slab gel electrophoresis on sodium dodecyl sulfate (SDS) polyacrylamide followed by electroelution. The purified fragments migrated as 28-, 25-, and 23.5-kDa fragments, respectively. Each of the fragments inhibited opsonization of a diluted antiserum prepared in rabbits by immunization with whole type 1 streptococci. The amino-terminal sequences of the peptide fragments were confirmed by comparison with the primary structure predicted from the nucleotide sequence of the type 1 M protein structural gene. The 28-kDa fragment contained the NH2-terminal asparagine residue of the processed type 1 M protein, whereas the NH2-terminal sequences of the 25- and 23.5-kDa peptides began at residues 27 and 36, respectively. A seven-residue periodicity with respect to polar and nonpolar residues was observed beginning at residue 22 and, therefore, the secondary structural potential of type 1 M protein is similar to that reported for other M proteins. In contrast to the other M proteins, however, identical repeats were rare, the longest sequence identity consisting of a three-amino acid acid sequence Lys-Asp-Leu at positions 30-32 repeated once at positions 65-67. A 23-residue synthetic peptide of the amino-terminus of the type 1 M protein evoked opsonic antibodies against type 1 streptococci. These results indicate that the NH2-terminal region of type 1 M protein retains the secondary structural characteristics of other M serotypes. Moreover, it contains epitopes that evoke protective immune responses. Our studies may have bearing in the development of safe and effective vaccines against group A streptococcal infections.

Sequence and type-specific immunogenicity of the amino-terminal region of type 1 streptococcal M protein

The NH2-terminal sequence of type 1 M protein was determined by automated Edman degradation of purified polypeptide fragments extracted from whole streptococci by limited digestion with pepsin. Three polypeptide fragments were purified by slab gel electrophoresis on sodium dodecyl sulfate (SDS) polyacrylamide followed by electroelution. The purified fragments migrated as 28-, 25-, and 23.5-kDa fragments, respectively. Each of the fragments inhibited opsonization of a diluted antiserum prepared in rabbits by immunization with whole type 1 streptococci. The amino-terminal sequences of the peptide fragments were confirmed by comparison with the primary structure predicted from the nucleotide sequence of the type 1 M protein structural gene. The 28-kDa fragment contained the NH2-terminal asparagine residue of the processed type 1 M protein, whereas the NH2-terminal sequences of the 25- and 23.5-kDa peptides began at residues 27 and 36, respectively. A seven-residue periodicity with respect to polar and nonpolar residues was observed beginning at residue 22 and, therefore, the secondary structural potential of type 1 M protein is similar to that reported for other M proteins. In contrast to the other M proteins, however, identical repeats were rare, the longest sequence identity consisting of a three-amino acid acid sequence Lys-Asp-Leu at positions 30-32 repeated once at positions 65-67. A 23-residue synthetic peptide of the amino-terminus of the type 1 M protein evoked opsonic antibodies against type 1 streptococci. These results indicate that the NH2-terminal region of type 1 M protein retains the secondary structural characteristics of other M serotypes. Moreover, it contains epitopes that evoke protective immune responses. Our studies may have bearing in the development of safe and effective vaccines against group A streptococcal infections.

Protective immunogenicity and T lymphocyte specificity of a trivalent hybrid peptide containing NH2-terminal sequences of types 5, 6, and 24 M proteins synthesized in tandem

The protective immunogenicity of a hybrid peptide containing tandem copies of types 5, 6, and 24 M protein epitopes was investigated. An NH2-terminal peptide of type 24 M protein was chemically synthesized and then extended to include NH2-terminal peptides of types 6 and 5 M proteins yielding a 34-residue hybrid peptide containing a cysteine residue at its COOH-terminus. When conjugated via the cysteine residue to keyhole limpet hemocyanin (KLH), emulsified in CFA, and injected into rabbits, the synthetic hybrid evoked opsonic antibodies against types 5, 6, and 24 streptococci without stimulating tissue crossreactive immunity. The trivalent hybrid also was capable of priming T lymphocytes in vivo that responded to each of the native serotypes of M protein as well as to the synthetic hybrid peptide in vitro. The primed T cells failed to respond to the individual component peptides contained in the hybrid peptide, suggesting that the hybrid peptide confers conformations resembling the presentations of each of the subpeptides in the respective serotypes of M protein. The brisk immune responses to the type 6 peptide contained in the middle of the tandem hybrid indicates that with judicious placement between proline residues, potentially hidden peptides are readily accessible to the immune system. These results suggest that synthetic tandem peptides can be tailored in a fashion in which each of the component sets of protective epitopes can be made optimally immunoaccessible and immunogenic.

A hepatic fibrogenic factor stimulates the synthesis of types I, III, and V procollagens in cultured cells

A hepatic fibrogenic factor (HFF) isolated from fibrotic rat livers has previously been shown to stimulate the transcription of type I procollagen genes in cultured fibroblasts (Raghow, R., Gossage, D., Seyer, J. M., and Kang, A.H. (1984) J. Biol. Chem. 259, 12718-12723). To test if the expression of other collagen genes was similarly affected by the fibrogenic factor, we measured the rates of types I, III, and V procollagen synthesis in two different cell lines after treatment with HFF. The effect of fibrogenic factor on types I and III procollagens was tested in rat fibroblasts, while a human rhabdomyosarcoma cell line was used to evaluate the effect of HFF on type V procollagen synthesis. Incubation with rat fibroblasts resulted in a 3-4-fold stimulation of the synthesis of both types I and III procollagens in a time-dependent manner. The stimulated rates of types I and III procollagen synthesis accompanied an increase in the steady-state levels of their corresponding mRNAs. When A204 cells, which are derived from a rhabdomyosarcoma and exclusively synthesize type V procollagen, were incubated with the fibrogenic factor, a 3-4-fold stimulation of the synthesis of both pro-alpha 1(V) and pro-alpha 2(V) chains was seen. Using a cDNA probe for pro-alpha 2(V), we also observed that there was a 2-3-fold increase in the steady-state level of pro-alpha 2(V) mRNA in A204 cells after treatment with the fibrogenic factor. In both rat fibroblasts and A204 cells the steady-state levels of beta-actin mRNA were minimally affected by fibrogenic factor, suggesting that the procollagen genes were preferentially affected. Since types I, III, and V collagens are present in the normal liver and accumulate aberrantly in the fibrotic liver, we suggest that fibrogenic factor may play an important role in determining the altered collagen composition of the fibrotic liver. Based on these data, we also speculate that the regulation of the biosynthesis of a variety of procollagens in diverse cell types by HFF possibly occurs by a common mechanism.

Localization and characterization of Sendai virus nonstructural C and C' proteins by antibodies against synthetic peptides

Antibodies were raised in rabbits against two synthetic peptides, each 30 residues in length, one corresponding to the predicted common carboxyl termini of the nonstructural C and C' proteins of Sendai virus and the other to the unique amino terminus of the larger C protein. Each peptide was inoculated as a covalent complex with tetanus toxoid or in uncomplexed form. Only antibodies to the free carboxyl-terminal peptide precipitated both C and C' proteins made by in vitro translation of viral mRNA and reacted with the C protein from infected cells. These results confirm that the C and C' proteins are carboxyl-coterminal. Contrasting with the reported colocalization of intracellular measles virus C proteins with nucleocapsid inclusions, immunofluorescence studies revealed that Sendai virus C proteins were uniformly distributed in the cytoplasm whereas the viral P protein was present in inclusions that were mainly perinuclear. Since almost all P protein molecules are associated with viral nucleocapsids, these observations suggested that Sendai virus C protein molecules may be both nucleocapsid-associated and free in the cytoplasm. This interpretation was supported when the C and C' proteins were found in both nucleocapsid and free protein fractions of cell lysates. Anti-C antibodies did not inhibit viral RNA synthesis when added to an extract of infected cells. This result was consistent with the conclusion that the C proteins have no direct role in viral transcription, since virions lack C proteins but are transcriptionally active. Therefore, the functions of the C proteins remain undefined.

Post-transcriptional inhibition of collagen and fibronectin synthesis by a synthetic homolog of a portion of the carboxyl-terminal propeptide of human type I collagen

We evaluated the effects of a synthetic copy of a highly conserved portion (residues 225-246) of the COOH-propeptide of human pro-alpha 2(I) procollagen on collagen, fibronectin, and total protein synthesis by human fibroblasts. Incubation of COOH-propeptide 225-246 with fibroblasts resulted in a concentration-dependent inhibition of both type I procollagen and fibronectin when compared with controls; a 50% inhibition of both fibronectin and type I collagen was observed at a concentration of 45 microM. Since the overall cellular protein synthesis was only minimally affected, COOH-propeptide appeared to specifically inhibit collagen and fibronectin synthesis. The peptide was nontoxic to cells and the inhibition was completely reversible upon removal of the peptide. We measured the steady-state levels of mRNAs coding for procollagen, fibronectin, and beta-actin by hybridization to specific recombinant cDNA probes; there was no significant change in the steady-state level of mRNAs of the three proteins. These results strongly suggest that the biosynthesis of procollagen and fibronectin in COOH-propeptide-treated cells is inhibited at a post-transcriptional level. These data establish a link between collagen and fibronectin synthesis and further define the important interaction of these molecules in the formation of the extracellular matrix.