Search PubMed⌕ Search

Biomedical subjects

M R Kanost

Publications and source records attributed to M R Kanost.

At least 37 records · Page 2Linked to original sources
PubMed1999

A novel serpin expressed by blood-borne microfilariae of the parasitic nematode Brugia malayi inhibits human neutrophil serine proteinases.

Serine proteinase inhibitors (serpins) play a vital regulatory role in a wide range of biological processes, and serpins from viruses have been implicated in pathogen evasion of the host defence system. For the first time, we report a functional serpin gene from nematodes that may function in this manner. This gene, named Bm-spn-2, has been isolated from the filarial nematode Brugia malayi, a causative agent of human lymphatic filariasis. Polymerase chain reaction (PCR) and Western blot experiments indicate that Bm-spn-2 is expressed only by microfilariae (Mf), which are the long-lived blood-dwelling larval stage. A survey of the greater than 14,000 expressed sequence tags (ESTs) from B malayi deposited in dbEST shows that greater than 2% of the ESTs sequenced from Mf cDNA libraries correspond to Bm-spn-2. Despite its abundance in the microfilarial stage, Bm-spn-2 has not been found in any other point in the life cycle. The predicted protein encoded by Bm-spn-2 contains 428 amino acids with a putative signal peptide. Antibodies to recombinant Bm-SPN-2 protein react specifically with a 47.5-kD native protein in Mf extract. Bm-SPN-2 is one of the largest of the 93 known serpins, due to a 22 amino acid carboxy-terminal extension, and contains the conserved serpin signature sequence. Outside these regions, levels of homology are low, and only a distant relationship can been seen to a Caenorhabditis elegans serpin. The Bm-spn-2 gene contains 6 introns, 2 of which appear to be shared by both nematode species. The B malayi introns have an extended and conserved 3' splice site and are relatively large compared with C elegans. A panel of mammalian serine proteinases were screened and Bm-SPN-2 protein was found to specifically inhibit enzymatic activity of human neutrophil cathepsin G and human neutrophil elastase, but not a range of other serine proteinases. It is possible that Bm-SPN-2 could function as a stage-specific serpin in the blood environment of the microfilarial parasite in protection from human immunity and thus may be a good candidate for protective vaccine.

Amino Acid Sequence↗
PubMed1999

Developmental expression of Manduca sexta hemolin.

Hemolin is hemolymph protein that is a member of the immunoglobulin superfamily. Its induced expression after bacterial infection suggests that it functions in the immune response. In this paper, we describe the expression of the Manduca sexta hemolin gene at certain developmental stages in the absence of microbial challenge. Hemolin was present at a very low level in hemolymph of naive larvae until the beginning of the wandering stage prior to pupation, when its concentration in hemolymph increased dramatically. At the same time, hemolin could be found in the fluid contained in the midgut lumen. The appearance of hemolin mRNA in fat body and midgut at the beginning of the wandering stage correlated with the presence of hemolin in the hemolymph and midgut lumen. Hemolin was present in hemolymph through the pupal and adult stages. Hemolin was also present in newly deposited eggs, and persisted in eggs throughout embryonic development. A hemolin cDNA isolated from an adult fat body library had the same sequence as those previously obtained from larval libraries. Hemolin purified from hemolymph of bacteria-injected larvae, from hemolymph of naive wandering stage larvae and adult moths, and from midgut fluid of wandering stage larvae had the same apparent mass, which was consistent with the mass predicted from the hemolin cDNA sequence. Hemolin from hemolymph of wandering stage larvae did not contain any detectable carbohydrate, but hemolin from the hemolymph of bacteria-injected larvae and from naive adult moths was associated with carbohydrate, although of different amounts and composition. These results suggest that a single hemolin gene is developmentally regulated and is also induced when insects are exposed to microbial infection. M. sexta hemolin apparently lacks post-translational covalent glycosylation, but instead is associated under some conditions with non-covalently bound carbohydrates. Arch.

Animals↗
PubMed1999

Immulectin, an inducible C-type lectin from an insect, Manduca sexta, stimulates activation of plasma prophenol oxidase.

Immulectin, a C-type lectin from the tobacco hornworm, Manduca sexta, was cloned from a larval fat body cDNA library. The immulectin cDNA encodes a 309 residue polypeptide. Immulectin synthesis was induced by injection of killed gram-positive or gram-negative bacteria or yeast. After injection of bacteria, immulectin mRNA appeared in fat body and immulectin protein was detected in hemolymph. Immulectin contains two carbohydrate recognition domains. The carboxyl-terminal carbohydrate recognition domain is most similar (36% identity) to a lipopolysaccharide-binding protein from the American cockroach, Periplaneta americana. It also shares 26-35% identity to carbohydrate recognition domains of various mammalian C-type lectins. Two immulectin isoforms were identified in the hemolymph of bacteria-injected larvae. Recombinant immulectin agglutinated gram-positive and gram-negative bacteria and yeast. Addition of recombinant immulectin to M. sexta plasma stimulated activation of phenol oxidase. A combination of immulectin with lipopolysaccharide from E. coli activated phenol oxidase more rapidly and to a higher level than immulectin alone, whereas lipopolysaccharide by itself had little effect on phenol oxidase activation. Immulectin synthesized in response to bacterial or fungal infection may help to trigger protective responses in M. sexta in a manner similar to mannose-binding protein, a C-type lectin that functions in the mammalian innate immune system.

Adipose Tissue↗
PubMed1999

Biological activity of Manduca sexta paralytic and plasmatocyte spreading peptide and primary structure of its hemolymph precursor.

A family of hemolymph peptides was previously identified in several lepidopteran insects, which exhibited multiple biological activities including rapid paralysis, blockage of growth and development, or stimulation of plasmatocyte spreading and aggregation. We synthesized Manduca sexta paralytic peptide 1 (PP1) and found that after it was injected into larvae, bleeding from wounds was dramatically reduced. PP1 also stimulated spreading and aggregation behavior of M. sexta plasmatocytes in vitro. Stimulation of plasmatocyte aggregation and adherence to the body wall may explain a decrease observed in the number of circulating plasmatocytes after injection of PP1. Such aggregates might rapidly form plugs in wounds to prevent bleeding. We cloned a cDNA for a Manduca paralytic peptide precursor, using polymerase chain reactions and cDNA library screening. The active 23-residue PP2 peptide encoded by this clone is at the carboxyl-terminal end of a precursor protein predicted to be 107 amino acid residues long after cleavage of a secretion signal peptide. Active PP2 was produced by processing of recombinant proPP2 by bovine factor Xa. A single proPP2 mRNA was present in fat body but not in hemocytes. The level of this mRNA was not affected by injection of bacteria into larvae. We produced recombinant proPP2 in Escherichia coli and used this protein to produce an antiserum. The antiserum detected proPP2 in plasma and was used to observe rapid proteolytic processing of proPP2 after hemolymph collection.

Amino Acid Sequence↗
PubMed1999

Structure of a paralytic peptide from an insect, Manduca sexta.

Paralytic peptide 1 (PP1) from a moth, Manduca sexta, is a 23-residue peptide (Glu-Asn-Phe-Ala-Gly-Gly-Cys-Ala-Thr-Gly-Tyr-Leu-Arg-Thr-Ala-Asp-Gly-Arg -Cys-Lys-Pro-Thr-Phe) that was first found to have paralytic activity when injected into M. sexta larvae. Recent studies demonstrated that PP1 also stimulated the spreading and aggregation of a blood cell type called plasmatocytes and inhibited bleeding from wounds. We determined the solution structure of PP1 by two-dimensional 1H NMR spectroscopy to begin to understand structural-functional relationships of this peptide. PP1 has an ordered structure, which is composed of a short antiparallel beta-sheet at residues Tyr11-Thr14 and Arg18-Pro21, three beta turns at residues Phe3-Gly6, Ala8-Tyr11 and Thr14-Gly17, and a half turn at the carboxyl-terminus (residues Lys20-Phe23). The well-defined secondary and tertiary structure was stabilized by hydrogen bonding and side-chain hydrophobic interactions. In comparison with two related insect peptides, whose structures have been solved recently, the amino-terminal region of PP1 is substantially more ordered. The short antiparallel beta-sheet of PP1 has a folding pattern similar to the carboxyl-terminal subdomain of epidermal growth factor (EGF). Therefore, PP1 may interact with EGF receptor-like molecules to trigger its different biological activities.

Amino Acid Sequence↗
PubMed1999

Four serine proteinases expressed in Manduca sexta haemocytes.

Several putative serine proteinases were detected in Manduca sexta larval plasma by labelling with radioactive diisopropyl fluorophosphate. To begin to identify and characterize such enzymes, a polymerase chain reaction was carried out using haemocyte cDNA as template and primers designed to amplify conserved sequences from serine proteinases. Four serine proteinase cDNA fragments were cloned. These were used as probes to screen an M. sexta larval haemocyte cDNA library to obtain full-length clones encoding haemocyte proteinases 1-4 (HP1, HP2, HP3 and HP4). HP1 and HP2 contain an aminoterminal 'clip' domain similar to those found in horseshoe crab clotting enzyme and clotting factor B and also in the Drosophila melanogaster proteinases snake and easter. HP3 and HP4 are most similar to proteinases from mammalian leucocytes. HP1 and HP2 are both present in plasma. HP1 is expressed in haemocytes (granular cells and oenocytoids) and not in fat body. HP2 is expressed in fat body and in granular haemocytes, plasmatocytes and oenocytoids. After injection of larvae with bacteria, the level of HP2 mRNA decreased in haemocytes and increased in fat body.

Amino Acid Sequence↗
PubMed1998

Pro-phenol oxidase activating proteinase from an insect, Manduca sexta: a bacteria-inducible protein similar to Drosophila easter.

Activation of pro-phenol oxidase (proPO) in insects and crustaceans is important in defense against wounding and infection. The proPO zymogen is activated by a specific proteolytic cleavage. PO oxidizes phenolic compounds to produce quinones, which may help to kill pathogens and can also be used for synthesis of melanin to seal wounds and encapsulate parasites. We have isolated from the tobacco hornworm, Manduca sexta, a serine proteinase that activates proPO, and have cloned its cDNA. The isolated proPO activating proteinase (PAP) hydrolyzed artificial substrates but required other protein factors for proPO activation, suggesting that proPO-activating enzyme may exist as a protein complex, one component of which is PAP. PAP (44 kDa) is composed of two disulfide-linked polypeptide chains (31 kDa and 13 kDa). A cDNA for PAP was isolated from a hemocyte library, by using a PCR-generated probe based on the amino-terminal amino acid sequence of the 31-kDa catalytic domain. PAP belongs to a family of arthropod serine proteinases containing a carboxyl-terminal proteinase domain and an amino-terminal "clip" domain. The member of this family most similar in sequence to PAP is the product of the easter gene from Drosophila melanogaster. PAP mRNA was present at a low level in larval hemocytes and fat body, but became much more abundant in fat body after insects were injected with Escherichia coli. Sequence data and 3H-diisopropyl fluorphosphate labeling results suggest that the same PAP exists in hemolymph and cuticle.

Amino Acid Sequence↗
PubMed1997

Characterization and functional analysis of 12 naturally occurring reactive site variants of serpin-1 from Manduca sexta.

Serpin gene-1 from the tobacco hornworm, Manduca sexta, encodes, through alternative exon usage, 12 reactive site variants (Jiang, H., Wang, Y. and Kanost, M. R., (1994) J. Biol. Chem. 269, 55-58; Jiang, H., Wang, Y., Huang, Y., Mulnix, A. B., Kadel, J., Cole, K., and Kanost, M. R. (1996) J. Biol. Chem. 271, 28017-28023). These 43-kDa proteins differ from each other only in their COOH-terminal 39-46 residues, which include the reactive site. To test the hypothesis that these proteins are proteinase inhibitors of diverse selectivities and to begin to elucidate their physiological functions, we expressed the 12 serpin-1 variants in Escherichia coli. Seven of the variants inhibited mammalian serine proteinases, with association rate constants comparable with those of human serpins. Serpin-1A, with a P1 Arg residue, inhibited both trypsin and plasmin. Serpin-1B (P1 Ala) and serpin-1F (P1 Val) inhibited porcine pancreatic elastase and human neutrophil elastase. Serpin-1H, -1K, and -1Z, all with a Tyr residue at the P1 position, inhibited chymotrypsin and cathepsin G. Serpin-1I (P1 Leu) inhibited both elastase and chymotrypsin. Nine of the serpin variants were active as inhibitors of microbial serine proteinases, including subtilisin Carlsberg, proteinase K, and two proteinases secreted by an entomopathogenic fungus, Metarhizium anisopliae. In addition, one of the serpin variants, serpin-1J, strongly inhibited activation of M. sexta hemolymph phenoloxidase, a pathway involving a serine proteinase cascade. This pathway is a component of the defensive response of insects to microbial infection. These results suggest that the products of M. sexta serpin gene-1 may be important in regulating both exogenous and endogenous serine proteinases in hemolymph.

Animals↗
PubMed1997

Molecular cloning of cDNAs for two pro-phenol oxidase subunits from the malaria vector, Anopheles gambiae.

Phenol oxidase exists in insect hemolymph as a zymogen, pro-phenol oxidase (pro-PO), which is activated by specific proteolysis in response to infection or wounding. Phenol oxidase catalyses the synthesis of quinones that polymerize to form melanin deposits, which encapsulate parasites and help to seal wounds. Antibodies to pro-PO from Manduca sexta bound to 76, 72, and 71 kDa polypeptide bands from hemolymph of Anopheles gambiae larvae. This antiserum was used to screen a cDNA library from A. gambiae fourth-instar larvae. Full-length clones were isolated for two different pro-POs, designated A. gambiae proPO-p1 and proPO-p2, which are 67% identical in nucleotide sequence and 66% identical in deduced amino acid sequence. The A. gambiae pro-PO sequences are more similar to pro-PO from Drosophila melanogaster than to lepidopteran or crustacean pro-PO sequences in the GenBank database. Like the other arthropod pro-POs, the A. gambiae pro-PO sequences lack a signal peptide and have two conserved regions predicted to bind two copper atoms in the active site of the enzyme. The availability of these pro-PO cDNAs should be useful in examining the biochemical differences between A. gambiae strains that are refractory or susceptible to Plasmodium infection, and differ in their ability to encapsulate the parasites.

Amino Acid Sequence↗
PubMed1997

Subunit composition of pro-phenol oxidase from Manduca sexta: molecular cloning of subunit ProPO-P1.

Phenol oxidase (PO) is known to play an important role in defense mechanisms in insect immunity. It is present as a zymogen in insect hemolymph, and can be activated by a specific proteolytic reaction that is stimulated by microbial cell wall components. The pro-phenol oxidase (pro-PO) purified from the larval hemolymph of Manduca sexta contains two polypeptides in equal amounts as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A cDNA for one of the polypeptides, now designated proPO-p2, has been isolated (Hall et al. (1995) Proc. Natl. Acad. Sci. USA, 92, 7764-7768). We purified pro-PO from plasma of M. sexta and characterized its subunit composition. A cDNA for M. sexta proPO-p1 was isolated from a larval hemocyte cDNA library. M. sexta proPO-p1 is 78% identical in amino acid sequence to Bombyx mori proPO-p1, but only 50% to M. sexta or B. mori proPO-p2. Immunofluorescence labelling and in situ hybridization showed that the pro-PO is synthesized in a single hemocyte type, the oenocytoids. Analysis of pro-PO by size exclusion high-pressure liquid chromatography (HPLC) revealed that pro-PO exists as monomeric, dimeric, trimeric or multimeric structures depending on the ionic strength. All of these isoforms of the protein have phenol oxidase activity upon activation with a detergent, cetylpyridinium chloride. In analysis by non-denaturing PAGE, the majority of the purified pro-PO was present as two dimers of distinct mobility (fast and slow forms). Both forms contain proPO-p1 and proPO-p2, suggesting that they are heterodimers. Individual larvae can contain the slow form, the fast form, or both, which suggests that the slow and fast forms of proPO are allelic variants. These results indicate that there are two pro-PO genes in M. sexta, which are coordinately expressed in oenocytoids, and whose products form predominantly heterodimers in plasma.

Amino Acid Sequence↗
PubMed1997

Biological mediators of insect immunity.

Infection in insects stimulates a complex defensive response. Recognition of pathogens may be accomplished by plasma or hemocyte b1p4eins that bind specifically to bacterial or fungal polysaccharides. Several morphologically distinct hemocyte cell types cooperate in the immune response. Hemocytes attach to invading organisms and then isolate them by phagocytosis, by trapping them in hemocyte aggregates called nodules, or by forming an organized multicellular capsule around large parasites. These responses are often accompanied by proteolytic activation of the phenoloxidase zymogen that is present in the hemolymph. A component of insect immune responses to bacteria is the synthesis by fat body and hemocytes of a variety of antibacterial proteins and peptides, which are secreted into the hemolymph. These molecules attack bacteria by several mechanisms. Inducible antifungal proteins have also been recently discovered in insect hemolymph. The promoters for several antibacterial protein genes in insects are regulated by transcription factors similar to those involved in mammalian acute phase responses.

Animals↗
PubMed1996

Organization of serpin gene-1 from Manduca sexta. Evolution of a family of alternate exons encoding the reactive site loop.

Manduca sexta serpin gene-1 encodes a family of serpins whose amino acid sequences are identical in their amino-terminal 336 residues but variable in their carboxyl-terminal 39-46 residues, which includes the reactive site loop (Jiang, H., Wang, Y., and Kanost, M. R. (1994) J. Biol. Chem. 269, 55-58). Here, we report the gene's complete nucleotide sequence and exon-intron structure. A unique characteristic of this gene is its exon 9, which is present in 12 alternate forms between exons 8 and 10. Isolation and characterization of cDNA clones containing exons 9C, 9H, and 9I, which were not found previously, indicate that all 12 alternate forms of exon 9 can be utilized to generate 12 different serpins. The splicing pathway apparently allows inclusion of only one exon 9 per molecule of mature serpin-1 mRNA. Analysis of exon-intron border sequences reveals unique features that may be involved in regulation of RNA splicing. The exon 9 region has apparently evolved through rounds of exon duplication and sequence divergence. The exons near the center of the region may have evolved recently, whereas the outermost exons are the most ancient. Exons 9G and 9H were duplicated as a pair from exons 9E and 9F, an event that may have occurred more than once in the history of this gene.

Animals↗
PubMed1996

Primary structure of ribosomal proteins S3 and S7 from Manduca sexta.

We have isolated from Manduca sexta full-length cDNAs encoding proteins homologous to human ribosomal proteins S3 and S7. These are the first ribosomal protein sequences obtained from non-Dipteran insects. M. sexta ribosomal protein S3 has a molecular mass of 26,715 Da. Ribosomal protein S7 has a mass 21,870 Da. Both are basic proteins, with abundant Lys and Arg residues that may interact with ribosomal RNA in the ribosome. Southern blot hybridization suggests the presence of single genes for both ribosomal proteins in the M. sexta genome. Alignments with other S3 and S7 sequences available In the database indicate regions of the ribosomal proteins that have been the most highly conserved in evolution and may point to important functional regions in the proteins. Ribosomal protein S3 appears to be more highly conserved then ribosomal protein S7. This may be due to greater constraints on the structure of S3 because of its dual functions in translation as a ribosomal protein and in DNA repair in the nucleus.

Amino Acid Sequence↗
PubMed1995

Isolation and characterization of apolipophorin-III from the giant water bug (Lethocerus medius).

Upon injection of synthetic adipokinetic hormone, lipophorin from Lethocerus medius decreased in density and became associated with apolipophorin-III (apoLp-III). ApoLp-III isolated from hemolymph of Lethocerus medius had a M(r) = 19,000 and an amino acid composition high in methionine, in comparison with other apoLp-IIIs. Its circular dichroism spectrum was consistent with a protein with secondary structure of predominantly alpha-helix. NH2-terminal sequence alignment with apoLp-III sequences from other species showed a conservation of the hydrophobic or hydrophilic properties of residues at each position rather than of specific amino acids. ApoLp-III from Lethocerus medius has the potential to form amphipathic alpha-helices, similar to those found in the three-dimensional structure of Locusta migratoria apoLp-III. A portion of the apoLp-III molecules that are not associated with lipophorin contained the blue chromophore, biliverdin.

Amino Acid Sequence↗
PubMed1995

Regulation of serpin gene-1 in Manduca sexta.

Hemolymph of Manduca sexta contains proteins from the serpin superfamily, which are inhibitors of serine proteinases. We have used probes specific for M. sexta serpin gene-1 mRNA and protein to study the expression and hormonal regulation of this gene. Serpin gene-1 is expressed at a high level in larval fat body and at a lower abundance in hemocytes, where serpin protein is localized in the granules of granular cells. Serpin gene-1 mRNA is abundant in the fat body of feeding fourth and fifth instar larvae, but disappears abruptly at molts and at the wandering stage. The concentration of serpin proteins in hemolymph during development is correlated with the abundance of serpin mRNA in fat body. Results of in vivo and in vitro experiments indicate that 20-hydroxyecdysone has a role in negative regulation of serpin gene-1.

Animals↗
PubMed1995

Expression and characterization of recombinant Manduca sexta serpin-1B and site-directed mutants that change its inhibitory selectivity.

Hemolymph of Manduca sexta contains a number of serine proteinase inhibitors from the serpin superfamily. During formation of a stable complex between a serpin and a serine proteinase, the enzyme cleaves a specific peptide bond in an exposed loop (the reactive-site region) at the surface of the serpin. The amino acid residue on the amino-terminal side of this scissile bond, the P1 residue, is important in defining the selectivity of a serpin for inhibiting different types of serine proteinases. M. sexta serpin-1B, with alanine at the position predicted from sequence alignments to be the P1 residue, was previously named alaserpin. This alanyl residue was changed by site-directed mutagenesis to lysine (A343K) and phenylalanine (A343F). The serpin-1B cDNA and its mutants were inserted into an expression vector, H6pQE-60, and the serpin proteins were expressed in Escherichia coli. Affinity-purified recombinant serpins selectively inhibited mammalian serine proteinases: serpin-1B inhibited elastase; serpin-1B(A343K) inhibited trypsin, plasmin, and thrombin; serpin-1B(A343F) inhibited chymotrypsin as well as trypsin. All three serpins inhibited human cathepsin G. This insect serpin and its site-directed mutants associated with mammalian serine proteinases at rates similar to those reported for mammalian serpins. Serpin-1B and its mutants formed SDS-stable complexes with the enzymes they inhibited. The scissile bond was determined to be between residues 343 and 344 in wild-type serpin-1B and in serpin-1B with mutations at residue 343. These results demonstrate that the P1 alanine residue defines the primary selectivity of serpin-1B for elastase-like enzymes, and that this selectivity can be altered by mutations at this position.

Amino Acid Sequence↗
PubMed1995

Organization and expression of the hemolin gene, a member of the immunoglobulin superfamily in an insect, Manduca sexta.

Hemolin is a protein from the immunoglobulin (Ig) superfamily found so far in the haemolymph of two lepidopteran insect species, Hyalophora cecropia and Manduca sexta. Injection of bacterial into these insects induces the expression of hemolin. We have isolated the hemolin gene from M. sexta and determined its DNA sequence and transcription start site. The hemolin gene is 3127 bp long and contains six exons. The only correspondence between exons and the four Ig domains of hemolin is in domain 4, which is encoded by exon 6. Southern blot analysis indicates that there is one copy of the hemolin gene in the M. sexta genome. Analysis of the 5'-flanking sequence of the hemolin gene resulted in identification of potential regulatory sequences. Hemolin mRNA accumulated in haemocytes, as well as fat body, in response to injection of larvae with bacteria. Hemolin was detected by immunocytochemistry in only one of the five morphological haemocyte types in M. sexta, the granular cells.

Amino Acid Sequence↗