Dietary tannins and salivary proline-rich proteins: interactions, induction, and defense mechanisms.
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Biomedical subjects
Publications and source records attributed to D M Carlson.
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One gene of the mouse proline-rich protein multigene family was cloned on a 3.6-kilobase pair EcoRI/BglII DNA fragment from a (partial) Sau3A bacteriophage library of CD-1 mouse chromosomal DNA. Phage harboring the gene were identified by plaque hybridization using 32P-labeled proline-rich protein cDNA inserts from clones pRP33 and pMP1 obtained from rat and mouse, respectively. The transcriptional unit includes three exonic sequences separated by 1434 base pairs (intron I) and 450 base pairs (intron II). The complete primary structure of the gene and the 5' and 3' flanking regions (3595 base pairs) were determined by the Maxam and Gilbert (Maxam, A.M., and Gilbert, W. (1980) Methods Enzymol. 65, 499-560) sequencing method. The DNA on the 5' side of exon I contains several sequences that may be involved in the induction and expression of this mouse gene. These sequences include putative regulatory sites such as those considered to be inducible by cAMP and steroids, Z-DNA and enhancer sequences and the expected TATAA and CAAT boxes. The mature protein coding region, exon II, is not interrupted with intron sequences. Exon III is located in the nontranslated region and contains the poly(A) addition site. The deduced amino acid sequence showed that the protein encoded by this gene contains 13 tandemly repeat regions, each 14 amino acids in length, with the prototype sequence PPPPGGPQPRPPQG. Each amino acid within the repeat has a favored codon. The consensus DNA sequence for each repeat is CCA CCA CCA CCA GGA GGC CCA CAG CCG AGA CCC CCT CAA GGC. The high degree of conservation of both nucleotide and amino acid sequences within the repeat region suggests that proline-rich protein genes likely evolved by gene duplication of a 42-base pair internal repeat.
Multigene families encode the proline-rich proteins that are so prominent in human saliva and are dramatically induced in mouse and rat salivary glands by isoproterenol treatment and by feeding tannins. A cDNA encoding an acidic proline-rich protein of rat has been sequenced (Ziemer, M. A., Swain, W. F., Rutter, W. J., Clements, S., Ann, D. K., and Carlson D. M. (1984) J. Biol. Chem. 259, 10475-10480). This study presents the nucleotide sequences of five additional proline-rich protein cDNAs complementary to both mouse and rat parotid and submandibular gland mRNAs. Amino acid compositions deduced from the nucleotide sequences are typical for proline-rich proteins: 25-45% proline, 18-22% glycine, and 18-22% glutamine and generally an absence of sulfur-containing amino acids except for the initiator methionine. These proline-rich proteins display unusual repeating peptide sequences of 14-19 amino acids. The derived amino acid sequence of the cDNA insert of plasmid pMP1 from mouse has a 19-amino acid sequence which is repeated four times. The inserts of plasmids pUMP40 and pUMP4 also from mouse encode for 12 and 11 repeats of a 14-amino acid peptide, respectively. These repetitive sequences, and others from rat and mouse cDNAs and from human genomic clones, all show very high homologies and likely evolved from duplication of internal portions of an ancestral gene. Gene conversion could account for the high degree of conservation of nucleotide sequences of the repeat regions. Protein derived from the nucleotide sequences are all characterized by four general regions: a putative signal peptide, a transition region, the repetitive region, and a carboxyl-terminal region. The 5'-flanking sequences and sequences encoding the putative signal peptides are highly conserved (greater than 94%) in all six cDNAs. This sequence conservation may be important in the regulation of the biosynthesis of these unusual proteins.
Glycoproteins which contain about 45 mol% proline were dramatically induced in mouse parotid and submandibular glands by isoproterenol treatment, but these unusual proteins were not detected in control animals. These acid-soluble substances were obtained by extracting tissues with 10% trichloroacetic acid, as reported previously for isolating proline-rich proteins from rat submandibular glands (Mehansho, H., and Carlson, D.M. (1983) J. Biol. Chem. 258, 6616-6620). Three major proline-rich glycoproteins were induced in parotid glands with apparent molecular weights of 66,000 (GP-66p), 45,000 (GP-45p), and 27,000 (GP-27p), whereas only one such protein was expressed by the submandibular glands (66,000 (GP-66sm]. Both GP-66p and GP-66sm contained about 19% carbohydrate with the following molar ratios, respectively; GalNAc, 1.0, 1.0; Gal, 1.6, 2.3; GlcNAc, 0.8, 1.1; sialic acid, 0.9, 1.9. The peptide chains of GP-66p and GP-66sm appear to be identical by amino acid compositions, glycopeptide analysis, and preliminary amino acid sequencing data. Northern blot analysis of RNAs from parotid glands of normal and isoproterenol-treated rats, probed with a 32P-labeled proline-rich protein cDNA, confirmed that control animals were devoid of mRNAs encoding these proteins and that isoproterenol treatment dramatically induced expression of these genes. Feeding sorghum high in tannins caused changes in the parotid glands similar to those observed upon isoproterenol treatment, as noted earlier with rats (Mehansho, H., Hagerman, A., Clements, S., Butler, L., Rogler, J., and Carlson, D.M. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 3948-3952). These glycoproteins have high affinities for tannins as demonstrated by competitive binding curves.
Endonuclease restriction (Hind III) fragments of DNA from Chinese hamster X mouse somatic cell hybrids hybridized with proline-rich protein complementary DNA clones only when the DNA was isolated from cells containing mouse chromosome 8, or a fragment of chromosome 8. The evidence suggests that proline-rich protein genes are located at the proximal portion of chromosome 8 toward the centromere.
Plasmids containing cDNAs for proline-rich proteins have been isolated from a cDNA library prepared from parotid glands of isoproterenol-treated rats. The nucleotide sequence of one of these cDNAs (pRP33) has been determined, and it encodes an acidic proline-rich protein. The N-terminal 13 amino acids are highly hydrophobic and may be part of a signal peptide. The next 66 amino acids constitute an acidic domain which is interrupted by a short (8 residue) basic region. The sequence beginning at proline 80 contains six tandemly repeated regions of 18 to 19 amino acids in length with the prototype sequence PPPQGGPQXPPQPGXPQG. Two pairs of these repeats (amino acid residues 116 to 152 and 153 to 189) are 93% homologous in nucleotide sequence. The high homology in both nucleotide and amino acid sequences in the repeat region suggests that this protein may have evolved by duplication of internal portions of a progenitor gene.
In previous studies on glycosyltransferase activities in porcine trachea, we demonstrated the presence of two galactosyltransferases which transfer galactose from UDP-galactose to N-acetylglucosamine (Sheares, B.T. and Carlson, D.M. (1983) J. Biol. Chem. 258, 9893-9898). One enzyme, UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase, synthesized galactosyl-beta 1,3-N-acetylglucosamine while the other, UDP-galactose:N-acetylglucosamine 4 beta-galactosyltransferase, synthesized galactosyl-beta 1,4-N-acetylglucosamine. A third galactosyltransferase has now been demonstrated utilizing a solubilized membrane preparation from pig trachea, which also synthesizes galactosyl-beta 1,4-N-acetylglucosamine as determined by gas-liquid chromatography and Diplococcus pneumoniae beta-galactosidase treatment. This new UDP-galactose:N-acetylglucosamine 4 beta-galactosyltransferase is distinct from the lactose synthetase A protein in that it does not bind to alpha-lactalbumin-agarose or to N-acetylglucosamine-agarose. The enzyme is separable from the UDP-galactose:N-acetylgalactosaminyl-mucin 3 beta-galactosyltransferase by affinity chromatography on asialo ovine submaxillary mucin adsorbed to DEAE-Sephacel. This newly discovered 4 beta-galactosyltransferase binds to UDP-hexanolamine-Sepharose and is partially separated from UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase by Sephacryl S-200 gel filtration chromatography. Neither high concentrations of N-acetylglucosamine (200 mM) nor alpha-lactalbumin inhibits the incorporation of galactose into galactosyl-beta 1,4-N-acetylglucosamine by this enzyme.
During 1981, 946 patients with advanced renal failure who were maintained by dialysis were studied to assess the frequency and the duration of hospitalizations and to identify complications that prompted hospitalization. Five hundred fifty-eight patients (59%) were hospitalized for a total of 1,207 times (mean of 1.8 stays/yr and 15 days/yr at risk for the entire group). The major reasons for hospitalization were dialysis access problems (25%), gastrointestinal complications (13%), and cardiac complications (13%). Both the rate of stays/yr and the rate of days/yr increased with advancing age and were highest in patients who died during the year of study. Both the rate and the duration of hospitalization were higher for patients maintained by peritoneal dialysis than for those on hemodialysis (P less than 0.001). In patients younger than 45 years of age, diabetics had more frequent and more prolonged hospitalizations than nondiabetics, whereas in those 46 to 60 years of age, complications other than diabetes predisposed to hospitalization. In those 61 years of age or older, in whom hospitalization rates were the highest, no single risk factor could be identified as predisposing to hospitalization other than age and peritoneal dialysis. Although the interactions of these factors were not assessed, considerable agreement existed with previous studies that had been analyzed in a more sophisticated manner.
The salivary protein gene complex consists of a series of loci coding for related but distinct proline-rich proteins (PRPs) found chiefly in saliva. We have screened a library of human genomic DNA fragments in bacteriophage lambda Charon 4A with a PRP cDNA synthesized and cloned from rat parotid gland mRNA. Two phages (PRP1 and PRP2) hybridizing to the rat probe under moderately stringent conditions contain related but not identical DNAs. Preliminary nucleotide sequence data indicate that both DNAs include regions comprised of nearly identical tandemly repeated sequences, each able to code for about 21 amino acids. The decoded consensus repeat sequence is homologous to the repeating amino acid units found by others in human PRPs. This and other features demonstrate that these two clones are members of the PRP gene family. Polymorphic differences between the DNAs of different individuals were observed after probing digests of human genomic DNA with a HinfI fragment from PRP1. These DNA polymorphisms reflect size differences, possibly caused by frequent unequal crossing-over between the repeated units in the PRP genes.
We have previously reported the enzymatic synthesis of galactosyl-beta 1,3-N-acetylglucosamine using membrane preparations from pig trachea (Sheares, B. T., Lau, J. T. Y., and Carlson, D. M. (1982) J. Biol. Chem. 257, 599-602). The enzyme catalyzing the synthesis of this disaccharide, UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase, has been solubilized and contaminating galactosyltransferases, including the UDP-galactose:N-acetylglucosamine 4 beta-galactosyltransferase and the UDP-galactose:N-acetylgalactosamine-mucin 3 beta-galactosyltransferase, were removed by affinity chromatography on alpha-lactalbumin-agarose, N-acetylglucosamine-agarose, and asialo-ovine submaxillary mucin bound to DEAE-Sephacel. UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase and a yet unidentified UDP-galactose:N-acetylglucosamine 4 beta-galactosyltransferase, both not retained by the alpha-lactalbumin-agarose, were further purified by adsorption to a UDP-hexanolamine-Sepharose column and these two galactosyltransferase activities were finally resolved by gel filtration on Sephacryl S-200. The purified UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase displays an absolute requirement for a divalent cation (Mn2+ or Co2+) and is most active at pH 6.0. Unlike the UDP-galactose:N-acetylglucosamine 4 beta-galactosyltransferase, UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase is not inhibited by high concentrations of N-acetylglucosamine. Apparent Km values are UDP-galactose, 0.23 mM, and N-acetylglucosamine, 385 mM. The apparent Km for a synthetic acceptor, N-acetylglucosaminyl-beta 1, 3-N-acetylgalactosamine-O-benzyl, was 2.4 mM. Acceptor specificity suggests that this 3 beta-galactosyltransferase is responsible for elongation of oligosaccharide chains in mucin glycoproteins and in glycolipids.
A family of proline-rich proteins which contain over 40% proline and a glycoprotein were isolated from submandibular glands of isoproterenol-treated rats by extraction with 10% trichloroacetic acid and fractionation of the acid-soluble portion on Bio-Gel A-1.5m. The proline-rich proteins were subsequently separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Proteins were detected by formaldehyde fixation and Coomassie staining. After elution from the gels, amino acid compositions were determined. The family of proline-rich proteins (about six) appears to be qualitatively identical with a family of proteins from parotid glands of isoproterenol-treated rats (Muenzer J., Bildstein, C., Gleason, M., and Carlson, D. M. (1979) J. Biol. Chem. 254, 5623-5628, 5629-5634), except for a substantial change in the relative amount of each protein. An acid-soluble glycoprotein (GP-158) was not detected in extracts of submandibular glands of normal rats, but GP-158 was highly induced by isoproterenol treatment. This glycoprotein has an apparent Mr = 158,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The major amino acids were Asx, 13%; Glx, 18%; Pro, 29% and Gly, 11%. GP-158 contained about 37% carbohydrate, and its sugar composition on a molar basis was mannose, 3.0; galactose, 2.1; N-acetylglucosamine, 3.5; fucose, 1.2; and sialic acid (N-glycolyl(4-O-acetyl)neuraminic acid), 0.9. N-Acetylgalactosamine was not detected. A glycopeptide isolated from GP-158 had the same sugar composition as GP-158. The amino acid sequence of the glycopeptide was shown to be Asp-Gly-(Asn)-Gln-Thr-Gln-Pro-Arg-Pro-(Gly-Pro). Only the parotid and submandibular glands of rats responded in this dramatic fashion to isoproterenol. The isoproterenol-treated rat is considered an appropriate model system for studying the overall effects of catecholamine beta-agonists on gene expression in these secretory tissues.
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Feeding of sorghum with a high level of tannin (high-tannin sorghum) to rats caused changes in gene expression in parotid glands similar to isoproterenol treatment. Within 3 days the parotid glands were enlarged about 3-fold and a series of proline-rich proteins were increased about 12-fold. Unlike isoproterenol treatment, no changes were observed in the submandibular glands, and a Mr 220,000 glycoprotein in parotid glands was not induced. Amino acid analyses, electrophoretic patterns, and cell-free translations of mRNAs all confirmed that the proline-rich proteins induced by feeding high-tannin sorghum were identical to those induced by isoproterenol treatment. Binding curves for proline-rich proteins to tannins showed affinities 10-fold greater than bovine serum albumin and tannins.
Treatment of rats with the beta-agonist isoproterenol causes a dramatic increase in a series of proteins rich in proline (proline-rich proteins) in the parotid glands (Muenzer, J., Bildstein, C., Gleason, M., and Carlson, D. M. (1979) J. Biol. Chem. 254, 5623, 5629). These proteins which contain about 43% proline, comprise more than 50% of the total soluble protein of glands of rats treated with isoproterenol for 10 days. Further studies by in vitro translation analysis using the reticulocyte lysate system and labeling with [3H]proline or [35S]methionine show definitive changes in patterns of protein synthesis and proline-rich protein mRNAs are highly elevated in treated animals. Analysis of translation products by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed (1) very little synthesis of proline-rich proteins from poly(A+) RNA of glands of normal rats, (2) poly(A+) RNA from glands of treated animals synthesize mainly proline-rich proteins, (3) translations with [3H]proline and [35S]methionine give identical labeling patterns from cell-free translations are all precipitated by antibodies to proline-rich proteins. At least six different proline-rich proteins are translated with poly(A+) mRNA from glands of treated animals. Each of these proteins is likely a translation product of a separate, specific mRNA. The dramatic changes in protein synthesis of rat parotid glands in response to isoproterenol treatment suggest to us that the parotid gland of the isoproterenol-treated rat is an excellent model system to study the overall responsiveness of gene expression to catecholamines.
Analysis of the soluble protein fractions from the rat parotid, submandibular and sublingual glands by polyacrylamide-gel electrophoresis reveals similarities in overall patterns of protein synthesis at birth. Tissue-specific changes in protein and glycoprotein synthesis occur shortly after birth and again at the time of weaning, 21--28 days later. Incorporation of [3H]thymidine into DNA was at its highest after birth and gradually decreased in both the parotid and submandibular gland, whereas [3H]thymidine incorporation in the sublingual gland was low throughout the time of neonatal development. [14C]Leucine incorporation into total protein increased in all glands with age after birth, showing an accelerated rate 21--28 days later. Trichloroacetic acid/phosphotungstic acid-precipitable [3H]fucose in glycoproteins declined over the time of neonatal development in the parotid and submandibular gland, but its incorporation remained higher in the sublingual gland. alpha-Amylase (EC 3.2.1.1) in the salivary glands increased at the time of weaning, as judged by detectability in sodium dodecyl sulphate/polyacrylamide gels and by immune precipitation. Two membrane-bound enzymes, UDP-galactose:2-acetamido-2-deoxy-D-glucosamine 4 beta-galactosyltransferase (EC 2.4.1.22) and UDP-galactose:2-acetamido-2-deoxy-D-galactosaminyl-protein 3 beta-galactosyltransferase (no EC number), undergo tissue-specific change rather than changes induced by physiological stimulation of the salivary glands.
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The biosynthesis of galactosyl-beta 1,3-N-acetylglucosamine has been demonstrated using membrane preparations from pig trachea. Unlike the UDP-galactose:2-acetamido-2-deoxy-D-glucose 4 beta-galactosyltransferase, which is inhibited by high levels of N-acetylglucosamine, the UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase shows no inhibition at 200 mM N-acetylglucosamine. About 80% of the total disaccharide synthesized at 200 mM N-acetylglucosamine was base-labile suggesting the 1,3-linkage, alpha-Lactalbumin inhibits galactose incorporation into galactosyl-beta 1,4-N-acetylglucosamine but has little or no effect on the activity of the 1,3-galactosyltransferase. Escherichia coli beta-galactosidase readily hydrolyzed the base-stable product, but not the base-labile component. The apparent 1,3-linked disaccharide was reduced with NaBH4 and was isolated by Bio-Gel P-2 column chromatography. Methylation analysis by gas chromatography/mass spectrometry showed tetramethyl galactose and a 3-substituted N-acetylglucosaminitol. Neither the beta 1,4 nor the beta 1,3 disaccharide was hydrolyzed by green coffee bean alpha-galactosidase. Both disaccharides were readily hydrolyzed by bovine testes beta-galactosidase. This is the first report on the galactosyltransferase which catalyzes the synthesis of the galactosyl-beta 1,3-N-acetylglucosamine linkage such as found in the Type I chain of human blood group substances. A tissue survey in rats showed only rat intestine to have readily detectable UDP-galactose: N-acetylglucosamine 3 beta-galactosyltransferase activity. The intestinal membrane fraction like the tracheal enzyme catalyzes the synthesis of two disaccharides as judged by base treatment, and these appear to be the beta 1,3 and beta 1,4 isomers of galactosyl-N-acetylglucosamine.