The immunoglobulin family protein Hemolin mediates cellular immune responses to bacteria in the insect Manduca sexta. 2007

Ioannis Eleftherianos, and Firat Gökçen, and Gabriella Felföldi, and Peter J Millichap, and Tina E Trenczek, and Richard H ffrench-Constant, and Stuart E Reynolds
Department of Biology and Biochemistry, University of Bath, Claverton Down, UK.

Bacterial recognition in the lepidopteran insect, Manduca sexta, is mediated by pattern recognition proteins including Hemolin, Peptidoglycan recognition protein (PGRP) and Immulectin-2. These proteins bind to molecular patterns present on the surface of bacteria and trigger a protective response involving humoral and cellular reactions. Cellular mechanisms mediated by haemocytes include phagocytosis, encapsulation, and the formation of melanotic nodules. Here, we show that a non-pathogenic strain of Escherichia coli induces mRNA transcription and protein expression of Hemolin and PGRP but not Immulectin-2 in Manduca haemocytes. This upregulation can be effectively prevented (knocked-down) using RNA interference (RNAi) following injection of double-stranded (ds) RNA. Knock-down of Hemolin significantly decreased the ability of insects to clear E. coli from the haemolymph and caused a reduction in the number of free haemocytes. RNAi of Hemolin reduced the ability of haemocytes to engulf bacteria through phagocytosis and to form melanotic nodules in vivo. Importantly, washed haemocytes taken from RNAi-treated insects showed reduced ability to form microaggregates around bacteria in vitro. This shows that the immune function affected by RNAi knock-down of Hemolin is intrinsic to the haemocytes. In contrast, RNAi of PGRP had no effect on any of these cellular immune functions. These results demonstrate the vital role of Hemolin in Manduca cellular immune responses.

UI MeSH Term Description Entries
D007136 Immunoglobulins Multi-subunit proteins which function in IMMUNITY. They are produced by B LYMPHOCYTES from the IMMUNOGLOBULIN GENES. They are comprised of two heavy (IMMUNOGLOBULIN HEAVY CHAINS) and two light chains (IMMUNOGLOBULIN LIGHT CHAINS) with additional ancillary polypeptide chains depending on their isoforms. The variety of isoforms include monomeric or polymeric forms, and transmembrane forms (B-CELL ANTIGEN RECEPTORS) or secreted forms (ANTIBODIES). They are divided by the amino acid sequence of their heavy chains into five classes (IMMUNOGLOBULIN A; IMMUNOGLOBULIN D; IMMUNOGLOBULIN E; IMMUNOGLOBULIN G; IMMUNOGLOBULIN M) and various subclasses. Globulins, Immune,Immune Globulin,Immune Globulins,Immunoglobulin,Globulin, Immune
D007814 Larva Wormlike or grublike stage, following the egg in the life cycle of insects, worms, and other metamorphosing animals. Maggots,Tadpoles,Larvae,Maggot,Tadpole
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D010587 Phagocytosis The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES). Phagocytoses
D002352 Carrier Proteins Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes. Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D006434 Hemocytes Any blood or formed element especially in invertebrates. Hemocyte
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012330 RNA, Double-Stranded RNA consisting of two strands as opposed to the more prevalent single-stranded RNA. Most of the double-stranded segments are formed from transcription of DNA by intramolecular base-pairing of inverted complementary sequences separated by a single-stranded loop. Some double-stranded segments of RNA are normal in all organisms. Double-Stranded RNA,Double Stranded RNA,RNA, Double Stranded
D015153 Blotting, Western Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes. Immunoblotting, Western,Western Blotting,Western Immunoblotting,Blot, Western,Immunoblot, Western,Western Blot,Western Immunoblot,Blots, Western,Blottings, Western,Immunoblots, Western,Immunoblottings, Western,Western Blots,Western Blottings,Western Immunoblots,Western Immunoblottings

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