title: Immulectin-2, a lipopolysaccharide-specific lectin from an insect, Manduca sexta, is induced in response to gram-negative bacteria.
abstract: A lipopolysaccharide-specific lectin, immulectin-2, was isolated from plasma of the tobacco hornworm, Manduca sexta. Immulectin-2 has specificity for xylose, glucose, lipopolysaccharide, and mannan. A cDNA clone encoding immulectin-2 was isolated from an Escherichia coli-induced M. sexta larval fat body cDNA library. The cDNA is 1253 base pairs long, with an open reading frame of 981 base pairs, encoding a 327-residue polypeptide. Immulectin-2 is a member of the C-type lectin superfamily. It consists of two carbohydrate recognition domains, which is similar to the organization of M. sexta immulectin-1. Immulectin-2 was present at a constitutively low level in plasma of control larvae and increased 3-4-fold after injection of Gram-negative bacteria or lipopolysaccharide. Immulectin-2 mRNA was detected in fat body of control larvae, and its level increased dramatically after injection of E. coli. The concentration of immulectin-2 in plasma did not change significantly after injection of Gram-positive bacteria or yeast, even though its mRNA level was increased by these treatments. Compared with immulectin-1, immulectin-2 has a more restricted specificity for binding to Gram-negative bacteria. Immulectin-2 at low physiological concentrations agglutinated E. coli in a calcium-dependent manner. It also bound to immobilized lipopolysaccharide from E. coli. Binding of immulectin-2 to lipopolysaccharide stimulated phenol oxidase activation in plasma. The properties of immulectin-2 are consistent with its function as a pattern recognition receptor for detection and defense against Gram-negative bacterial infection in M. sexta.
authors.affiliation: Department of Biochemistry, Kansas State University, Manhattan, Kansas 66506, USA.
authors.forename: X Q
authors.initials: XQ
authors.lastname: Yu
authors.forename: M R
authors.initials: MR
authors.lastname: Kanost
mesh_terms: D000372:Agglutination Tests; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000502:physiology*; D019476:Insect Proteins; D037102:Lectins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D037181:Lectins, C-Type; D008024:Ligands; D008070:Lipopolysaccharides / Q000494:pharmacology*; D018402:Manduca / Q000378:metabolism* / Q000382:microbiology; D008969:Molecular Sequence Data; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D018076:DNA, Complementary; D019476:Insect Proteins; D037102:Lectins; D037181:Lectins, C-Type; D008024:Ligands; D008070:Lipopolysaccharides; C417733:immulectin-2 protein, Manduca sexta