Tissue-specific expression of mouse-alpha-amylase genes: nucleotide sequence of isoenzyme mRNAs from pancreas and salivary gland

Purification and characterization of amylases from three freshwater fish species providing new insight application as enzyme molecular markers for zymography

Purification of amylases from digestive tracts of three freshwater fish species with Q-Sepharose Fast Flow and Sephacryl S-200 columns displayed two isoforms of amylases from Osteochilus hasselti (O1, O2) and three isoforms of those from both Hampala dispar (UB, H1, H2) and Puntioplites proctozystron (P1, P2, P3). The optimum pH values displayed at 7.0 and 8.0, while the optimum temperatures revealed at 40 and 50 °C. Almost isoenzyme activities were activated by NaCl and CaCl2, whereas EDTA and SDS strongly inhibited all enzymatic activities. Verification with an atomic absorption spectrophotometry exhibited the presence of Ca2+ ions in the range of 0.02-13.53 ppm per mg protein indicating that amylases are Ca2+ dependent. Molecular weight analysis revealed 12 to 147 kDa. The UB, O1, and H2 amylases with appropriate molecular masses of 64, 49, and 25 kDa validated with LC-MS/MS were selected. Three certain enzymes revealed high stability in a sample buffer after five cycles of freeze-thawing process upon storage at - 20 °C for 12 weeks. No protein degradation was observed on polyacrylamide gel, and the enzymes still displayed sharp and clear bands on zymograms. The result suggested that the purified fish amylases, which expressed high activities and stabilities, were potentially used as enzyme molecular weight markers for zymography.

Murine Salivary Amylase Protects Against Streptococcus mutans-Induced Caries

Saliva protects dental surfaces against cavities (i. e., dental caries), a highly prevalent infectious disease frequently associated with acidogenic Streptococcus mutans. Substantial in vitro evidence supports amylase, a major constituent of saliva, as either protective against caries or supporting caries. We therefore produced mice with targeted deletion of salivary amylase (Amy1) and determined the impact on caries in mice challenged with S. mutans and fed a diet rich in sucrose to promote caries. Total smooth surface and sulcal caries were 2.35-fold and 1.79-fold greater in knockout mice, respectively, plus caries severities were twofold or greater on sulcal and smooth surfaces. In in vitro experiments with samples of whole stimulated saliva, amylase expression did not affect the adherence of S. mutans to saliva-coated hydroxyapatite and slightly increased its aggregation in solution (i.e., oral clearance). Conversely, S. mutans in biofilms formed in saliva with 1% glucose displayed no differences when cultured on polystyrene, but on hydroxyapatite was 40% less with amylase expression, suggesting that recognition by S. mutans of amylase bound to hydroxyapatite suppresses growth. However, this effect was overshadowed in vivo, as the recoveries of S. mutans from dental plaque were similar between both groups of mice, suggesting that amylase expression helps decrease plaque acids from S. mutans that dissolve dental enamel. With amylase deletion, commensal streptococcal species increased from ~75 to 90% of the total oral microbiota, suggesting that amylase may promote higher plaque pH by supporting colonization by base-producing oral commensals. Importantly, collective results indicate that amylase may serve as a biomarker of caries risk.

Cloning, expression, homology modelling and molecular dynamics simulation of four domain-containing α-amylase from Streptomyces griseus

In the present study, α-amylase from Streptomyces griseus TBG19NRA1 was amplified, cloned and successfully expressed in E. coli BL21/DE3. Sequence analysis of S. griseus α-amylase (SGAmy) revealed the presence of four domains (A, B, C and E). Alpha-amylases with E domain (also known as carbohydrate binding module 20 (CBM20)) are capable of degrading raw starch and this property holds great potential for application in starch processing industries. Though α-amylase is a well-studied and characterized enzyme, there is no experimental structure available for this four domain-containing α-amylases. To gain more insight about SGAmy structure and function, homology modelling was performed using a multi-template method. The template α-amylase from Pseudoalteromonas haloplanktis (PDB ID 1AQH) and E domain of Cyclodextrin glucanotransferase from Bacillus circulans (PDB ID 1CGY) was found to have significant similarity with the complete target sequence of SGAmy. Therefore, homology model for SGAmy was generated from the crystal structure of 1AQH and 1CGY and the resulting structure was subjected to 10 ns molecular dynamics (MD) simulation. Remarkably, CBM20 domain of SGAmy showed greater flexibility in MD simulation than other three domains. This observation is highly rational as this part of SGAmy is strongly implicated in substrate (raw starch) binding. Thus, conformational plasticity at CBM20 is functionally beneficial.Communicated by Ramaswamy H. Sarma.

An Evolutionary Perspective on the Impact of Genomic Copy Number Variation on Human Health

Copy number variants (CNVs), deletions and duplications of segments of DNA, account for at least five times more variable base pairs in humans than single-nucleotide variants. Several common CNVs were shown to change coding and regulatory sequences and thus dramatically affect adaptive phenotypes involving immunity, perception, metabolism, skin structure, among others. Some of these CNVs were also associated with susceptibility to cancer, infection, and metabolic disorders. These observations raise the possibility that CNVs are a primary contributor to human phenotypic variation and consequently evolve under selective pressures. Indeed, locus-specific haplotype-level analyses revealed signatures of natural selection on several CNVs. However, more traditional tests of selection which are often applied to single-nucleotide variation often have diminished statistical power when applied to CNVs because they often do not show strong linkage disequilibrium with nearby variants. Recombination-based formation mechanisms of CNVs lead to frequent recurrence and gene conversion events, breaking the linkage disequilibrium involving CNVs. Similar methodological challenges also prevent routine genome-wide association studies to adequately investigate the impact of CNVs on heritable human disease. Thus, we argue that the full relevance of CNVs to human health and evolution is yet to be elucidated. We further argue that a holistic investigation of formation mechanisms within an evolutionary framework would provide a powerful framework to understand the functional and biomedical impact of CNVs. In this paper, we review several cases where studies reveal diverse evolutionary histories and unexpected functional consequences of CNVs. We hope that this review will encourage further work on CNVs by both evolutionary and medical geneticists.

Expression and Localization of α-amylase in the Submandibular and Sublingual Glands of Mice

In the major salivary glands of mice, acinar cells in the parotid gland (PG) are known to be the main site for the production of the digestive enzyme α-amylase, whereas α-amylase production in the submandibular gland (SMG) and sublingual gland (SLG), as well as the cell types responsible for α-amylase production, has been less firmly established. To clarify this issue, we examined the expression and localization of both the mRNA and protein of α-amylase in the major salivary glands of male and female mice by quantitative and histochemical methods. α-amylase mRNA levels were higher in the order of PG, SMG, and SLG. No sexual difference was observed in α-amylase mRNA levels in the PG and SLG, whereas α-amylase mRNA levels in the female SMG were approximately 30% those in the male SMG. Using in situ hybridization and immunohistochemistry, signals for α-amylase mRNA and protein were found to be strongly positive in acinar cells of the PG, serous demilune cells of the SLG, and granular convoluted tubule (GCT) cells of the male SMG, weakly positive in seromucous acinar cells of the male and female SMG, and negative in mucous acinar cells of the SLG. These results clarified that α-amylase is produced mainly by GCT cells and partly by acinar cells in the SMG, whereas it is produced exclusively by serous demilune cells in the SLG of mice.

Proteomic analysis of pancreas in miniature pigs according to developmental stages using two-dimensional electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry

Organ transplantation is limited by the shortage of human organs. Many studies have sought to overcome this hurdle by using animal organs. Porcine organs, especially from miniature pigs, have been used for organ xenotransplantation rather than nonhuman primates. While the molecular profiling for transplantation is well known in humans and rodents, the situation for pigs is almost completely unknown. The present study examined protein regulation of the developing stages of the pancreatic proteome (4 day-old miniature neonate, 19 day-old miniature piglet, and 14 month-old miniature adult pigs) using two-dimensional gel electrophoresis and matrix assisted laser desorption/ionization-time of flight mass spectrometry. Thirteen different expressed spots were observed and nine were identified. The data presented within this study provides critical direction relating to the development of pancreas of miniature pigs, which will assist future proteome analysis of the pancreas, and advance our understanding of the hurdles facing xenotransplantation.

Tissue specific and non-specific changes in gene expression by aging and by early stage CR

Aging alters the expression of a variety of genes. Calorie restriction (CR), which extends life span in laboratory rodents, also changes gene expression. This study investigated changes in gene expression across three different tissues from the same mouse to examine how aging and early stage CR influence gene expression in different tissues of an organism. Expression profiling of heart, liver, and hypothalamus tissues was done in young (4-6 months) ad libitum fed (AL), young CR (2.5-4.5 months of CR), and old (26-28 months) AL male C57BL/6 mice. Aging significantly altered the expressions of 309, 1819, and 1085 genes in heart, liver, and hypothalamus tissues, respectively. In nine genes, aging altered expression across all three tissues although the regulation directions did not agree across all three tissues for some genes. Early stage CR in young mice significantly changed the expressions of 192, 839, and 100 genes in heart, liver, and hypothalamus tissues, respectively, and seven genes altered expression across all three tissues; three were up regulated and four were down regulated. The results of Gene Ontology (GO) Biological Process analysis indicated up regulation of antigen processing/presentation genes by aging and down regulation of stress response genes by early stage CR in all three tissues. The comparison of the results of aging and short term CR studies showed there were 389 genes, 18 GO biological processes, and 20 GO molecular functions in common.

An amylase/Cre transgene marks the whole endoderm but the primordia of liver and ventral pancreas

Mice bearing a Cre-encoding transgene driven by a compound [SV40 small t antigen/mousealpha-amylase-2] promoter expressed the recombinase at early developmental stages broadly in the embryonic endoderm before the pancreas and lungs begin to outgrow, but not in other germ layers, as determined indirectly by beta-galactosidase and YFP reporter activity, indicating that the transgene is in fact an endodermic marker. Interestingly, the liver and ventral pancreas were excluded from this expression pattern, denoting that the chimerical alpha-amylase-2 promoter was not active in the anterior leading edge of the endoderm (the presumptive region from which liver and ventral pancreas form). These transgenics thus confirm, among other findings, that dorsal and ventral pancreatic primordia have different intrinsic transcriptional capabilities. In conclusion, we have generated a new transgenic mouse that should be useful to target endoderm at early stages, without affecting the liver or ventral pancreas before embryonic day E12.5.

An experimental model of autoimmune pancreatitis in the rat

Autoimmune pancreatitis (AIP), a recently defined disease of unknown etiology, is characterized by inflammatory infiltrates in the pancreas with conspicuous involvement of the ducts. The disease clinically manifests in humans as epigastric pain, weight loss, and jaundice. This report describes the development of a novel animal model of this disease in the rat, which we have termed experimental autoimmune pancreatitis. Adoptive transfer of amylase-specific CD4(+) T cells was able to confer pancreatitis to naive syngeneic recipient animals. No treatments before the adoptive transfer of T cells were necessary for disease to ensue, and the severity of disease was proportional to the number of T cells administered. The pancreatic lesions of rats with experimental autoimmune pancreatitis were characterized histologically as overwhelmingly lymphocytic with occasional plasma cells, neutrophils, and mast cells. Acinar tissue destruction and ductular inflammation were common features, with less frequent involvement of larger ducts. Immunohistochemical analysis revealed the presence of CD4(+) T cells in large numbers as well as CD8(+) T cells, macrophages, and dendritic cells. Expression of MHC I and MHC II also increased at the site of the lesion. Clinically, the disease manifested as either failure to gain weight at a rate concomitant with control animals or as outright weight loss. Thus, administration of activated CD4(+) T cells specific for the pancreatic enzyme amylase can induce pancreatitis in the rat in a manner that is reminiscent of human AIP.

cDNA cloning, genomic structure, chromosomal mapping, and expression analysis of parotid secretory protein in pig

A novel cDNA has been isolated from pig parotid glands by 3' and 5' rapid amplification of cDNA ends and designated parotid secretory protein (PSP). The open reading frame of this cDNA covers 714 bases, encoding 238 amino acids, which show 56% identity with human PSP at the level of the primary protein structure. The PSP genomic sequence comprises eight exons and seven introns, is approximately 22 kb in size, determined by sequencing, and maps to pig chromosome 17q21-q23. RT-PCR, dot blot, and Northern blot analyses demonstrated that PSP is strongly expressed in parotid glands, but is not present in heart, liver, lung, kidney, muscle, or stomach. A search for functionally significant protein motifs revealed consensus sequences for casein kinase II phosphorylation and N-myristoylation. We observed a unique amino acid sequence pattern consisting of the residues Leu-X(6)-Leu-X(6)-Leu-X(7)-Leu-X(6)-Leu-X(6)-Leu near the amino-terminal portion of the protein, which is similar to the leucine zipper.

Expression of alpha-amylase isozymes in rat tissues

Gene expressions of alpha-amylase isozymes in rat tissues were analyzed by a reverse transcription-polymerase chain reaction (RT-PCR), followed by EcoRI digestion. This procedure is based on evidence that an RT-PCR product from mouse pancreas RNA is sensitive to EcoRI, but not the product from the salivary gland or liver RNAs. The method was applied to the analysis of alpha-amylase expression in rat liver after partial hepatectomy, in which a potent expression of pancreas type isozyme was observed. However, no expression of the pancreatic isozyme in the regenerating liver was found. We also analyzed the expression of alpha-amylase gene in several additional rat tissues. In intestine, stomach, testis and skeletal muscle, the corresponding PCR products were amplified, but few were detected in heart or spleen. Intestine and stomach expressed a pancreatic isozyme of alpha-amylase. Analyses of the alpha-amylase activity and protein indicated the presence of the enzyme in those tissues. Immunohistochemical analysis also indicated that the amylase proteins were specifically present in epithelial cells of rat intestinal mucosa. This is a convenient method for identification of alpha-amylase isozyme mRNA in rodent tissues.

Comparison of amylase mRNAs from rat parotid gland, pancreas and liver using reverse transcriptase-polymerase chain reaction

The expression of mRNA for amylase was examined using the reverse transcriptase-polymerase chain reaction (RT-PCR). An amylase product was strongly detected in parotid and pancreas, but less strongly in liver. The degree of identity between the PCR products was assessed by restriction-enzyme mapping using two restriction enzymes, EcoRI and ScaI, and DNA sequencing. The PCR product from pancreas was cut by both EcoRI and ScaI, while the products from parotid and liver were cut by EcoRI but not by ScaI. The sequence of the parotid product was 90.4% homologous to that of the pancreas, and 100% homologous to that of the liver. These results indicate that the same amylase mRNA may be expressed in parotid and liver. In addition, the expression of amylase mRNAs in other rat tissues was investigated using RT-PCR, and the sensitivity of each PCR product to ScaI was tested. A weak single band was detected in submandibular gland, sublingual gland and stomach. ScaI digestion cut the stomach product into two fragments, but had no effect on the submandibular and sublingual products. Thus, it may be possible to classify amylase isoenzymes into pancreatic and parotid types based on the sensitivity of their PCR products to ScaI.

Effect of C-domain N-glycosylation and deletion on rat pancreatic alpha-amylase secretion and activity

Even though all animal alpha-amylases include glycosylation sequons (Asn-Xaa-Thr/Ser) in their sequences, amylases purified from natural sources are not quantitatively glycosylated. When wild-type rat pancreatic alpha-amylase, which contains two glycosylation sequons, was expressed in animal cell lines the protein displayed a very low rate of glycosylation (approx. 2%), even after Brefeldin A treatment to increase the contact with the glycosylation machinery. Site-directed mutagenesis of the first glycosylation sequon (Asn(410)-->Gln) resulted in 90% of the protein being glycosylated at the second glycosylation sequon (Asn(459)). Mutation of the second sequon completely inhibited glycosylation. In order to ascertain if the interference in the glycosylation of Asn(459) that was eliminated by the Asn(410)-->Gln mutation could be due to the position of the asparagine residue in the Cys(448)-Cys(460) disulphide bridge, these cysteine residues were mutated to serine residues. The resulting mutant was found to be 100% glycosylated. All mutants with mutations in the C-domain had specific activities identical to that of the wild-type enzyme, indicating that enzymic activity is independent of the structure and modification of the C-terminal domain. To further test the independence of the C-domain with respect to the two N-terminal domains of the protein, which harbour the catalytic site, the last seven of the ten beta\beta-strands that make up the beta-sandwich configuration of the domain were deleted. The truncated protein was not secreted from cells and all enzyme activity was destroyed. These observations show that Asn(459) is the only site that can be glycosylated in wild-type amylase, and confirm the relative independence of the C-terminal domain of alpha-amylase with respect to enzyme activity. In addition, they also establish that the C-terminal domain is absolutely essential for the correct post-translational folding of the enzyme that is responsible for its activity and allows for its secretion.

Dietary carbohydrate source and energy intake influence the expression of pancreatic alpha-amylase in lambs

In ruminants, pancreatic alpha-amylase is the primary enzyme responsible for the initial hydrolysis of alpha-linked glucose in the small intestinal lumen. The objective of this experiment was to examine the effects of altered dietary starch and energy supply on the expression of pancreatic alpha-amylase mRNA, protein and activity in lambs. Wether lambs (n = 24; 28 +/- 0.5 kg body weight) were fed low or high starch diets at 1.2 or 1.8 x net energy of maintenance for at least 28 d before tissue collection. Lambs fed the high energy/high starch diet tended to have more pancreatic alpha-amylase protein (54.5 kDa; P: = 0.08) and had greater activity (P: = 0.03), but alpha-amylase mRNA (1.6 kb) tended to be lower (P: = 0.17). Additionally, rumen fluid total short-chain fatty acid concentration was greater (P: = 0.04) and plasma glucose concentration tended to be greater (P: = 0.07) in lambs fed the high energy/high starch diet. However, pancreatic trypsinogen protein (25. 5 kDa) and jejunal maltase activity were not influenced by dietary treatment, suggesting that different regulatory systems are involved in regulating the tissue protein or activity levels of these two enzymes compared with alpha-amylase. These data suggest that dietary regulation of pancreatic alpha-amylase expression in ruminants is complex and probably regulated by transcriptional and post-transcriptional events.

The alpha-amylase gene amyH of the moderate halophile Halomonas meridiana: cloning and molecular characterization

Two types of Tn1732-induced mutants defective in extracellular amylase activity were isolated from the moderate halophile Halomonas meridiana DSM 5425. Type I mutants displayed amylase activity in the periplasm, and were unable to use any of the carbon sources tested, including starch and its hydrolysis product maltose. The type II mutant was affected in the gene responsible for the synthesis of the extracellular alpha-amylase. This gene (amyH) was isolated by functional complementation of mutant II and sequenced. The deduced protein (AmyH) showed a high degree of homology to a proposed family of alpha-amylases consisting of enzymes from Alteromonas (Pseudoalteromonas) haloplanktis, Thermomonospora curvata, streptomycetes, insects and mammals. AmyH contained the four highly conserved regions in amylases, as well as a high content of acidic amino acids. The amyH gene was functional in the moderate halophile Halomonas elongata and, when cloned in a multicopy vector, in Escherichia coli. AmyH is believed to be the first extracellular-amylase-encoding gene isolated from a moderate halophile, a group of extremophiles of great biotechnological potential. In addition, H. meridiana and H. elongata were able to secrete the thermostable alpha-amylase from Bacillus licheniformis, indicating that members of the genus Halomonas are good candidates for use as cell factories to produce heterologous extracellular enzymes.

Cloning and expression of a chicken alpha-amylase gene

We have isolated and sequenced a genomic clone for a pancreatic alpha-amylase gene (amy) of the chicken (Gallus gallus). The gene is interrupted by nine introns, spans over 4 kb, and encodes a protein (AMY) of 512 aa that is 83% identical to the human pancreatic alpha-amylase enzyme. Southern blot analysis of chicken DNA revealed two distinct pancreatic amy loci. In addition, we have generated a cDNA from chicken pancreatic RNA corresponding to the coding sequence of the genomic clone. The cDNA was inserted into a yeast expression vector, and the resulting construct used to transform Saccharomyces cerevisiae cells. Transformed yeast cells synthesized and secreted active AMY enzyme, and the gel migration pattern of the alpha-amylase produced by the yeast cells was identical to that of the native chicken enzyme.

Characterization of four outer membrane proteins that play a role in utilization of starch by Bacteroides thetaiotaomicron

Results of earlier work had suggested that utilization of polysaccharides by Bacteroides spp. did not proceed via breakdown by extracellular polysaccharide-degrading enzymes. Rather, it appeared that the polysaccharide was first bound to a putative outer membrane receptor complex and then translocated into the periplasm, where the degradative enzymes were located. In a recent article, we reported the cloning and sequencing of susC, a gene from Bacteroides thetaiotaomicron that encoded a 115-kDa outer membrane protein. SusC protein proved to be essential for utilization not only of starch but also of intermediate-sized maltooligosaccharides (maltose to maltoheptaose). In this paper, we report the sequencing of a 7-kbp region of the B. thetaiotaomicron chromosome that lies immediately downstream of susC. We found four genes in this region (susD, susE, susF, and susG). Transcription of these genes was maltose inducible, and the genes appeared to be part of the same operon as susC. Western blot (immunoblot) analysis using antisera raised against proteins encoded by each of the four genes showed that all four were outer membrane proteins. Protein database searches revealed that SusE had limited similarity to a glucanohydrolase from Clostridium acetobutylicum and SusG had high similarity to amylases from a variety of sources. SusD and SusF had no significant similarity to any proteins in the databases. Results of 14C-starch binding assays suggested that SusD makes a major contribution to binding. SusE and SusF also appear to contribute to binding but not to the same extent as SusD. SusG is essential for growth on starch but appears to contribute little to starch binding. Our results demonstrate that the binding of starch to the B. thetaiotaomicron surface involves at least four outer membrane proteins (SusC, SusD, SusE, and SusF), which may form a surface receptor complex. The role of SusG in binding is still unclear.

Cloning and sequencing analysis of three amylase cDNAs in the shrimp Penaeus vannamei (Crustacea decapoda): evolutionary aspects

In Penaeus vannamei, alpha-amylase is the most important glucosidase and is present as at least two major isoenzymes which have been purified. In order to obtain information on their structure, a hepatopancreas cDNA library constructed in phage lambda-Zap II (Strategene) was screened using a synthetic oligonucleotide based on the amino acid sequence of a V8 staphylococcal protease peptide of P. vannamei alpha-amylase. Three clones were selected: AMY SK 37 (EMBL sequence accession number: X 77318) is the most complete of the analyzed clones and was completely sequenced. It contains the complete cDNA sequence coding for one of the major isoenzymes of shrimp amylase. The deduced amino acid sequence shows the existence of a 511-residue-long pre-enzyme containing a highly hydrophobic signal peptide of 16 amino acids. Northern hybridization of total RNA with the amylase cDNA confirms the size of the messenger at around 1,600 bases. AMY SK 28, which contains the complete mature sequence of amylase, belonged to the same family characterized by a common 3' terminus and presented four amino acid changes. Some other variants of this family were also partially sequenced. AMY SK 20 was found to encode a minor variant of the protein with a different 3' terminus and 57 amino acid changes. Phylogenetic analysis established with the conserved amino acid regions of the (beta/alpha) eight-barrel domain and with the total sequence of P. vannamei showed close evolutionary relationships with mammals (59-63% identity) and with insect alpha-amylase (52-62% identity). The use of conserved sequences increased the level of similarity but it did not alter the ordering of the groupings. Location of the secondary structure elements confirmed the high level of sequence similarity of shrimp alpha-amylase with pig alpha-amylase.

A single element of the elastase I enhancer is sufficient to direct transcription selectively to the pancreas and gut

The elastase I (EI) gene is expressed at high levels in the exocrine pancreas and at lower levels in other regions of the gut. The transcriptional enhancer of the EI gene, from nucleotides -205 to -72, recapitulates the expression of the endogenous gene in transgenic mice; it directs not only pancreatic acinar cell expression of a human growth hormone (hGH) transgene but also expression to the stomach, duodenum, and colon. This pattern of selective expression limited to the gastroenteropancreatic organ system is specified by the A element, one of three functional elements in the EI enhancer. When multimerized, the A element directed expression of a hGH reporter gene selectively to the pancreas, stomach, and intestine in transgenic mice. Immunofluorescent localization of hGH indicated that the A element multimer transgenes were expressed in the acinar cells of the pancreas as well as in Brunner's gland cells of the duodenum. The A element binds a pancreatic acinar cell-specific factor, PTF1. Our results show that while the A element is responsible for directing tissue and cell type specificity, other elements of the enhancer must be involved in the regulation of the level of gene expression.

A single element of the elastase I enhancer is sufficient to direct transcription selectively to the pancreas and gut

The elastase I (EI) gene is expressed at high levels in the exocrine pancreas and at lower levels in other regions of the gut. The transcriptional enhancer of the EI gene, from nucleotides -205 to -72, recapitulates the expression of the endogenous gene in transgenic mice; it directs not only pancreatic acinar cell expression of a human growth hormone (hGH) transgene but also expression to the stomach, duodenum, and colon. This pattern of selective expression limited to the gastroenteropancreatic organ system is specified by the A element, one of three functional elements in the EI enhancer. When multimerized, the A element directed expression of a hGH reporter gene selectively to the pancreas, stomach, and intestine in transgenic mice. Immunofluorescent localization of hGH indicated that the A element multimer transgenes were expressed in the acinar cells of the pancreas as well as in Brunner's gland cells of the duodenum. The A element binds a pancreatic acinar cell-specific factor, PTF1. Our results show that while the A element is responsible for directing tissue and cell type specificity, other elements of the enhancer must be involved in the regulation of the level of gene expression.

Cloning and characterization of an alpha-amylase gene from Streptomyces lividans

The alpha-amylase gene (amy) of Streptomyces lividans TK24 was cloned in an amylase deficient mutant strain S. lividans M2. The cloned gene contained an open reading frame (ORF) of 2757 nucleotides (919 amino acids) coding for a protein of 100 kDa. Sequencing of the amino terminus of the extracellular alpha-amylase protein revealed the presence of a signal peptide of 33 amino acid residues. The transcriptional initiation site was mapped by the primer extension method with T4 DNA polymerase and was found to be transcribed from an unique promoter. The alpha-amylase protein produced by S. lividans was larger than those derived from other origins. It also contained the four common conserved regions characteristic of other alpha-amylase proteins.

The salivary glands of the vector mosquito, Aedes aegypti, express a novel member of the amylase gene family

Several cDNA clones with similarity to alpha-amylases have been characterized from a library made from adult female salivary gland RNA isolated from the vector mosquito, Aedes aegypti. The corresponding gene, designated Amylase I (Amy I), is expressed specifically in the proximal-lateral lobes of the adult female salivary gland, a pattern overlapping that of another gene, Mal I, involved in carbohydrate metabolism. The deduced amino acid sequence of Amy I indicates that this gene encodes a protein, approximate M(r) = 81,500, that appears to be a novel member of the amylase gene family. The mosquito protein contains a putative signal peptide for secretion and several consensus sites for asparagine-linked glycosylation. The Amy I protein shows significant similarity to invertebrate and vertebrate amylases including the conservation of four reactive and substrate binding sites. However, the amino-terminal region of the Amy-I protein is unique to the mosquito. Similarity with the Drosophila melanogaster protein is evident only after the first 260 amino acids in the mosquito sequence. The identification of this gene and its expression pattern adds to the observed relationship between spatial-specific gene expression in the female salivary glands and the specific feeding mode of the adult mosquito.

Antibodies directed against a yeast carboxyl-terminal peroxisomal targeting signal specifically recognize peroxisomal proteins from various yeasts

The carboxyl-terminal tripeptide Ala-Lys-Ile is essential for targeting Candida tropicalis trifunctional enzyme (hydratase-dehydrogenase-epimerase) to peroxisomes of both Candida albicans and Saccharomyces cerevisiae (Aitchison,J.D., Murray, W.W. and Rachubinski, R. A. (1991).J. Biol. Chem. 266, 23197-23203). We investigated the possibility that this tripeptide may act as a general peroxisomal targeting signal (PTS) for other proteins in the yeasts C. tropicalis, C. albicans, Yarrowia lipolytica and S. cerevisiae, and in rat liver. Anti-AKI antibodies raised against the carboxyl-terminal 12 amino acids of trifunctional enzyme were used to search for this PTS in proteins of these yeasts and of rat liver. The anti-AKI antibodies reacted exclusively with multiple peroxisomal proteins from the yeasts C. tropicalis, C. albicans and Y. lipolytica. There was a weak reaction of the antibodies with one peroxisomal protein from S. cerevisiae and no reaction with peroxisomal proteins from rat liver. Antibodies directed against a synthetic peptide containing a carboxyl-terminal Ser-Lys-Leu PTS (Gould, S. J., Krisans, S., Keller, G.-A. and Subramani, S. (1990). J. Cell Biol. 110,27-34) reacted with multiple peroxisomal proteins of rat liver and with peroxisomal proteins of yeast distinct from those identified with anti-AKI antibodies. These results provide evidence that several peroxisomal proteins of different yeasts contain a PTS antigenically similar to that of C. tropicalis trifunctional enzyme and that this signal is absent from peroxisomal proteins from at least one mammalian system, rat liver.

Primary structure of locust flight muscle fatty acid binding protein

The amino acid sequence of the fatty acid binding protein (FABP) from flight muscle of the locust, Schistocerca gregaria, has been determined. The sequence of the N-terminal 39 amino acid residues, determined by automated Edman degradation, was used to prepare a degenerate oligonucleotide that corresponded to amino acid residues 16-23. cDNA coding for FABP was constructed from flight muscle mRNA and amplified by the polymerase chain reaction using the degenerate oligonucleotide and an oligo dT-NotI primer adapter as primers. The amplification product was cloned and sequenced. Additionally, a cDNA library of flight muscle mRNA was prepared and screened with a 414-bp probe prepared from the clone. The primary structure of locust FABP was compared with the proteins in the Swiss protein databank and found to have significant homology with mammalian FABPs over the entire 133-residue sequence. The best match was versus human heart FABP (41% identity), attesting to the highly conserved nature of this protein. The results suggest that locust muscle FABP is a member of the lipid binding protein superfamily and may provide valuable insight into the evolution of this abundant protein class.

Identification of the gene for the developmentally expressed 70 kDa heat-shock protein (P70) of mouse spermatogenic cells

Mouse spermatogenic cells synthesize a 70-kDa protein (P70) closely related to the major heat-shock protein (hsp70) of mammalian cells (R. L. Allen, D. A. O'Brien, and E. M. Eddy, Mol. Cell. Biol. 8, 828-832, 1988). Expression of P70 is developmentally regulated while hsp70 is induced in response to stress, suggesting that P70 is the product of a unique member of the Hsp70 multigene family transcribed in spermatogenic cells. A strong candidate for this gene was the Hsp70.2 gene (Z. F. Zakeri, D. J. Wolgemuth, and C. R. Hunt, Mol. Cell. Biol. 8, 2925-2932, 1988). A DNA segment from the 5' region of Hsp70.2 hybridized to a 2.7-kb transcript with a temporal pattern of expression in mouse spermatogenic cells similar to the P70 protein. We used a polyclonal antiserum generated against a synthetic peptide predicted from the Hsp70.2 sequence to characterize its protein product and to isolate cDNA clones from a pachytene spermatocyte expression library. The antiserum reacted specifically with meiotic and postmeiotic spermatogenic cells on sections of mouse testis. It recognized the P70 protein on Western blots of two-dimensional gels and did not bind to other heat-shock proteins of spermatogenic or somatic cells. The cDNAs hybridized to a 2.7-kb mRNA that was abundant in unstressed pachytene spermatocytes and round spermatids but was not detected in other cell types. Two cDNAs were sequenced and found to be 99% homologous to the 3' end of the Hsp70.2 gene. These data strongly supported the hypothesis that P70 is the expressed product of the Hsp70.2 gene in mouse spermatogenic cells.

Evolution of the transposable element Uhu in five species of Hawaiian Drosophila

The complete DNA sequence of three independent isolates of Uhu, a member of the Tc1-like class of transposable elements from D. heteroneura (Uhu-1, Uhu-3, and Uhu-4), has been determined. These isolates have between 95 and 96.4% nucleotide sequence identity indicating that Uhu is well conserved within this species. A comparison of the DNA sequences of Uhu and the D. melanogaster Hb1 transposable element shows that the nucleotide substitution rate for Uhu is comparable to the synonymous rate for the Adh gene in these species. Uhu has been identified in four other species of endemic Hawaiian Drosophila, D. silvestris, D. differens, D. planitibia and D. picticornis, and nine Uhu elements were isolated from genomic libraries of these four species. A 444 base pair region from within the coding region of the Uhu element, with well conserved ends, was amplified by the polymerase chain reaction and used for sequence comparison of elements from different species. The analysis of the sequence similarities between the elements within and between the species shows a grouping of the two pairs of most closely related species (D. heteroneura and D. silvestris, and D. differens and D. planitibia), but shows a much larger variation within the most recently diverged species (D. heteroneura and D. silvestris) than expected. There are extensive nucleotide substitutions and deletions in the Uhu elements from D. picticornis showing that they are degenerating and being lost in this species. These observations indicate that the Uhu element has been transmitted vertically and that transposition may have been activated at the time of formation of each species as it colonized the newly formed islands of the Hawaiian archipelago.

Effects of diabetes and insulin on alpha-amylase messenger RNA levels in rat parotid glands

Previous studies have shown that amylase levels are reduced significantly in the pancreas and parotid gland of diabetic rats and that insulin reverses this effect and increases the secretory protein levels. In the pancreas, these changes in amylase protein levels are accompanied by parallel changes in amylase mRNA levels. In the present study, the effects of diabetes and subsequent insulin treatments on contents (per cell) of amylase protein and its mRNA in parotid glands were compared in rats rendered diabetic with an injection of a beta-cell toxin, streptozotocin (STZ). Both amylase protein and its mRNA contents were reduced significantly in diabetic rats, compared with control rats, and this reduction was reversed following insulin injections of diabetic rats. In insulin-injected diabetic rats, amylase protein contents increased before a detectable increase in amylase mRNA levels was seen. The mRNA contents of a non-secretory protein, actin, did not change during diabetogenesis or subsequent insulin treatments. The reductions in parotid contents of amylase and its mRNA in diabetic rats and the reversal of these changes by insulin are similar to those changes that occur in the pancreas under the same conditions. However, the magnitude of these changes in parotid glands was much smaller than in the pancreas, and the effect of insulin on amylase mRNA synthesis was not as immediate as in the latter gland.

Salivary gland amylase polymorphism in pigs and cattle detected by affinity electrophoresis

New allelic variants of salivary gland alpha-amylase in pigs (AMY-1C, AMY-1D) have been detected using affinity electrophoresis. In yak, zebu and in hybrids (yak x cattle, zebu x cattle) a new AMY-1 allelic variant (AMY-1D) has been found using the same method.

The DNA-binding activity of transcription factor PTF1 parallels the synthesis of pancreas-specific mRNAs during mouse development

We have studied the expression of the alpha-amylase, trypsin, and elastase II genes in the acinar pancreas during mouse development. Transcriptional control is the major mechanism by which the differential accumulation of alpha-amylase, trypsin, and elastase II mRNAs is determined during late embryogenesis. The synthesis of pancreatic mRNAs is detected around day 15 of gestation and involves most if not all acinar cells. The DNA-binding activity of the pancreas-specific transcription factor PTF1, which binds to enhancers of genes expressed in this tissue, is detected for the first time at day 15 of gestation. The appearance of the factor at this early stage of development suggests that it plays an important role during pancreas differentiation.

The DNA-binding activity of transcription factor PTF1 parallels the synthesis of pancreas-specific mRNAs during mouse development

We have studied the expression of the alpha-amylase, trypsin, and elastase II genes in the acinar pancreas during mouse development. Transcriptional control is the major mechanism by which the differential accumulation of alpha-amylase, trypsin, and elastase II mRNAs is determined during late embryogenesis. The synthesis of pancreatic mRNAs is detected around day 15 of gestation and involves most if not all acinar cells. The DNA-binding activity of the pancreas-specific transcription factor PTF1, which binds to enhancers of genes expressed in this tissue, is detected for the first time at day 15 of gestation. The appearance of the factor at this early stage of development suggests that it plays an important role during pancreas differentiation.

Genomic organization of the region encoding guinea pig lipoprotein lipase; evidence for exon fusion and unconventional splicing

The coding sequence of guinea pig lipoprotein lipase (LPL) is organized into nine exons and spans a region of approximately 14 kb of the guinea pig genome. A non-conforming 5'-splice site is located on the first intron, which exhibits a 12-nucleotide perfect match with the 5'-end of the second exon. A previously described tryptic cleavage site is located on exon V, close to the 3' end of this exon. A similarity to vitellogenin resides on exons IV and V, and a putative active site is found on exon IV. A novel similarity to a fatty-acid-binding protein is noted on exon VI, adjacent to the postulated heparin-binding region. We suggest that free fatty acids (FFA) and heparin to some extent share the same site of interaction on the LPL molecule; and that a high local concentration of FFA can displace LPL from its site of action--the vascular endothelium--by competing for binding to heparan sulfate.

Hydrophobic cluster analysis of the primary sequences of alpha-amylases

The amino acid sequences of 18 alpha-amylases have been compared by hydrophobic cluster analysis. The method was first calibrated with two alpha-amylases (Aspergillus oryzae and pig pancreas) whose three-dimensional structures are known. It was then applied to the other alpha-amylases resulting in straightforward sequence alignments which could be used for structure prediction. It was found that all alpha-amylases which were investigated display the same basic super-secondary structure with a (beta alpha)8 barrel. Most of the secondary structure elements of the protein cores could be assigned to segments of the amino acid sequences. In addition, six sub-families could be identified, based upon specific similarities occurring in the variable regions of alpha-amylases.

Novel structures CTLA-2 alpha and CTLA-2 beta expressed in mouse activated T cells and mast cells and homologous to cysteine proteinase proregions

Differential screening of a subtracted cDNA library led to the detection of two distinct but homologous mouse cDNA, called CTLA-2 alpha and CTLA-2 beta. The corresponding transcripts have a tissue distribution restricted to T lymphocytes, where they are inducible upon activation, and to mast cells. The open-frame regions of both cDNA encode proteins homologous to cysteine proteinase precursors, remarkably, however, only to the proregion of these. The ctla-2 alpha and ctla-2 beta genes both map to the C1 band of mouse chromosome 13. Sequence comparisons suggest that the proregion of an ancestor proteinase gene evolved to the ctla-2 genes by successive duplications, first to autonomy, then to amplification. These results raise the question of the possible role of cysteine proteinase proregions, of cysteine proteinases themselves and of inhibitors thereof in activated T lymphocytes; from a different point of view, they also show that some protease proregions may have evolved as autonomous modules.

Glucocorticoid and developmental regulation of amylase mRNAs in mouse liver cells

We characterized alpha-amylase expression in the hepatoma cell line Hepa 1-6 and in normal mouse liver. Both Amy-1 and Amy-2 were expressed in Hepa 1-6 and were regulated by glucocorticoids. Transcription in the hepatoma cells was initiated at the same start sites as in mouse tissues. Glucocorticoid treatment increased the abundance of Amy-1 and Amy-2 transcripts by 10 to 20-fold. This increase was detected within 4 h and was maximal by 24 h. The pattern of amylase expression in this hepatoma cell line accurately reflects amylase expression in the liver in vivo. During liver development, we observed a large increase in the abundance of Amy-1 transcripts just before birth, at a time when circulating glucocorticoids are also elevated. Adult mouse liver expressed Amy-1 and Amy-2 at levels comparable to those of fully induced hepatoma cells. Liver is thus a likely source of both amylase isozymes in mouse serum. These studies demonstrate that Amy-2 expression is not limited to the pancreas but also occurs at a low level in liver cells.

Purification of lingual amylase from serous glands of rat tongue and characterization of rat lingual amylase and lingual lipase

Lingual amylase and lingual lipase, two digestive enzymes that are secreted from lingual serous glands (von Ebner's), were simultaneously purified from rat lingual serous glands with hydrophobic chromatography used as the final step. This method, previously developed for the purification of lingual lipase, includes homogenization of rat lingual serous glands, 100,000 g centrifugation, ammonium sulfate precipitation of proteins, and extraction of lipids with acetone at -20 degrees C, followed by hydrophobic chromatography on ethyl agarose or Agethane. Amylase was eluted after the elution of proteins that did not interact with the hydrophobic gel at pH 6.3. Lingual lipase was eluted with a solution containing micelles of taurodeoxycholate, monoolein, and oleic acid. Analysis of each of the purified enzymes by SDS-polyacrylamide gel electrophoresis revealed one band at Mr = 59,000 for amylase and one band at Mr = 51,000 for lingual lipase. Isoelectric focusing of amylase indicated a strong band at pI = 5.0 and two very faint bands at pI = 4.9 and 4.8, possibly isozymes or deamidated protein. Amino acid and hexosamine analyses were performed on the enzymes after electroelution from SDS-polyacrylamide gels. Both lingual lipase and lingual amylase had a high content of dicarboxylic (free and amide) amino acids. For lingual lipase and lingual amylase, the % molar ratios of aspartic acid/asparagine were 15.35 and 15.10, and the % molar ratios of glutamic acid/glutamine were 7.07 and 7.20, respectively. Lingual amylase was very similar to rat parotid, pancreatic, and mouse salivary amylases, except that it contained more proline (11.03% molar ratio).(ABSTRACT TRUNCATED AT 250 WORDS)

Primary sequence domains required for the retention of rotavirus VP7 in the endoplasmic reticulum

Rotavirus VP7 is a membrane-associated protein of the endoplasmic reticulum (ER). It is the product of rotavirus gene 9 which potentially encodes a protein of 326 amino acids that contains two amino terminal hydrophobic domains, h1 and h2, each preceded by an initiation codon. Comparison of the size of products derived from altered genes containing coding sequences for both h1 and h2 with those lacking the h1 sequence ('dhl' mutants), indicates that initiation takes place at M30 immediately preceding h2 (residues F32 to L48) and that h2 is cleaved, confirming the studies of others (Stirzaker, S.C., P.L. Whitfeld, D.L. Christie, A.R. Bellamy, and G.W. Both. 1987. J. Cell Biol. 105:2897-2903). Our previous work had shown that deletions in the carboxy end of h2, extending to amino acid 61 in the open reading frame, resulted in secretion of VP7. The region from amino acid number 51-61, present in wild-type VP7 but missing in the secreted mutant delta 47-61, was thus implicated to have a role in ER retention. To test this, a series of chimeric genes were constructed by fusing the first 63 codons of wild-type VP7, delta 1-14 or delta 51-61/dhl, to the mouse salivary alpha-amylase gene, a secretory protein, such that the fusion junction was located at the exact mature terminus of amylase. The chimeric proteins VP7(63)/amylase, delta 1-14(63)/amylase and delta 51-61(63)/dhl/amylase were secreted when expressed in cells and the h2 domain was cleaved when mRNA was translated in vitro. These results imply that the sequence 51-61 is necessary but not sufficient for ER retention. When a second series of VP7/amylase chimera were constructed extending the VP7 contribution to amino acid 111, the product expressed by delta 1-14(111)/amylase was not secreted whereas that of delta 47-61(111)/amylase was. Significantly, the intracellular delta 1-14(111)/amylase product exhibited an amylase enzymatic specific activity that was similar to that of the wild-type amylase product. We conclude that two regions of VP7 mediate its retention in the ER, the first lies within the sequence 51-61 and the second within the sequence 62-111, which contains the glycosylation site for VP7. Both regions are necessary for retention, though neither is sufficient alone.

Analysis of the Escherichia coli glycogen gene cluster suggests that catabolic enzymes are encoded among the biosynthetic genes

The nucleotide sequences of the Escherichia coli genome between the glycogen biosynthetic genes glgB and glgC, and 1170 bp of DNA which follows glgA have been determined. The region between glgB and glgC contains an open reading frame (ORF) of 1521 bp which we call glgX. This ORF is capable of coding for an Mr 56,684 protein. The deduced amino acid (aa) sequence for the putative product shows significant similarity to the E. coli glycogen branching enzyme, and to several different glucan hydrolases and transferases. The regions of sequence similarity include residues which have been reported to be involved in substrate binding and catalysis by taka-amylase. This suggests that the proposed product may catalyze hydrolysis or glycosyl-transferase reactions. The cloned region which follows glgA contains an incomplete ORF (1149 bp), glgY, which appears to encode 383 aa of the N terminus of glycogen phosphorylase, based upon sequence similarity with the enzyme from rabbit muscle (47% identical aa residues) and with maltodextrin phosphorylase from E. coli (37% identical aa residues). Results suggest that neither ORF is required for glycogen biosynthesis. The localization of glycogen biosynthetic and degradative genes together in a cluster may facilitate the regulation of these systems in vivo.

Glucocorticoid and developmental regulation of amylase mRNAs in mouse liver cells

We characterized alpha-amylase expression in the hepatoma cell line Hepa 1-6 and in normal mouse liver. Both Amy-1 and Amy-2 were expressed in Hepa 1-6 and were regulated by glucocorticoids. Transcription in the hepatoma cells was initiated at the same start sites as in mouse tissues. Glucocorticoid treatment increased the abundance of Amy-1 and Amy-2 transcripts by 10 to 20-fold. This increase was detected within 4 h and was maximal by 24 h. The pattern of amylase expression in this hepatoma cell line accurately reflects amylase expression in the liver in vivo. During liver development, we observed a large increase in the abundance of Amy-1 transcripts just before birth, at a time when circulating glucocorticoids are also elevated. Adult mouse liver expressed Amy-1 and Amy-2 at levels comparable to those of fully induced hepatoma cells. Liver is thus a likely source of both amylase isozymes in mouse serum. These studies demonstrate that Amy-2 expression is not limited to the pancreas but also occurs at a low level in liver cells.