Phenoloxidases in Insect Immunity

Kanost, Michael R.; Gorman, Maureen J.

doi:10.1016/b978-012373976-6.50006-9

Cited by 186 publications

(232 citation statements)

References 199 publications

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“…Although proPO activation in insect immunity has been investigated for many years (9), understanding of the proPO activation cascade is still incomplete. To investigate proPO activation and other immune pathways in M. sexta, we have isolated more than 20 serine proteinase cDNAs from fat body and hemocytes (15).…”

Section: Discussionmentioning

confidence: 99%

Functions of Manduca sexta Hemolymph Proteinases HP6 and HP8 in Two Innate Immune Pathways

Ishibashi

Ragan

et al. 2009

Journal of Biological Chemistry

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156

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Serine proteinases in insect plasma have been implicated in two types of immune responses; that is, activation of prophenoloxidase (proPO) and activation of cytokine-like proteins. We have identified more than 20 serine proteinases in hemolymph of the tobacco hornworm, Manduca sexta, but functions are known for only a few of them. We report here functions of two additional M. sexta proteinases, hemolymph proteinases 6 and 8 (HP6 and HP8). HP6 and HP8 are each composed of an amino-terminal clip domain and a carboxyl-terminal proteinase domain. HP6 is an apparent ortholog of Drosophila Persephone, whereas HP8 is most similar to Drosophila and Tenebrio spätzle-activating enzymes, all of which activate the Toll pathway. proHP6 and proHP8 are expressed constitutively in fat body and hemocytes and secreted into plasma, where they are activated by proteolytic cleavage in response to infection. To investigate activation and biological activity of HP6 and HP8, we purified recombinant proHP8, proHP6, and mutants of proHP6 in which the catalytic serine was replaced with alanine, and/or the activation site was changed to permit activation by bovine factor Xa. HP6 was found to activate proPO-activating proteinase (proPAP1) in vitro and induce proPO activation in plasma. HP6 was also determined to activate proHP8. Active HP6 or HP8 injected into larvae induced expression of antimicrobial peptides and proteins, including attacin, cecropin, gloverin, moricin, and lysozyme. Our results suggest that proHP6 becomes activated in response to microbial infection and participates in two immune pathways; activation of PAP1, which leads to proPO activation and melanin synthesis, and activation of HP8, which stimulates a Toll-like pathway.Innate immune systems of mammals and arthropods include extracellular serine proteinase cascade pathways, which rapidly amplify responses to infection and stimulate killing of pathogens. These proteinase-driven processes include the complement system of vertebrates (1, 2) and pathways in arthropods involving proteinases containing amino-terminal clip domains (3). Clip domain proteinases function in blood coagulation (4, 5), activation of prophenoloxidase (proPO) that leads to melanin synthesis (6 -9), and stimulation of the Toll pathway to promote synthesis of antimicrobial peptides/proteins (AMPs) 2 secreted into the hemolymph (10, 11).The serine proteinase systems best characterized in arthropods are the horseshoe crab hemolymph coagulation pathway and the cascade leading to activation of the Toll pathway in dorsal-ventral development in Drosophila (12-14). Recent research also has led to better characterization of the proPO activation pathway in Manduca sexta (7,15,16) and the Tollsignaling pathway in the Drosophila immune response (17, 18) and to both the proPO and Toll pathways in the beetle Tenebrio molitor (11,19).In the proPO activation pathway, soluble pattern recognition proteins initially recognize pathogen-associated molecular patterns such as bacterial peptidoglycan or fungal ␤-1,3-glucan (...

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Section: Discussionmentioning

confidence: 99%

Functions of Manduca sexta Hemolymph Proteinases HP6 and HP8 in Two Innate Immune Pathways

Ishibashi

Ragan

et al. 2009

Journal of Biological Chemistry

Self Cite

156

178

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“…(iii) Phenoloxidase (PO) activity was quantified as PO becomes activated upon cuticular wounding and infection, and is an important precursor instigating repair and encapsulation following infection or parasitism [88]. To determine simultaneously the longitudinal effects of melatonin supplementation, we collected haemolymph at four time periods: 2 days post the final moult and prior to placing crickets on their allocated melatonin treatment (week 0, baseline measure-see §3); 9 days post final moult (week 1); 16 days post final moult (week 2) and finally at 30 days post adult moult (week 4).…”

Section: (A) Supplementation With Dietary Melatoninmentioning

confidence: 99%

Melatonin: a possible link between the presence of artificial light at night and reductions in biological fitness

Jones

Durrant

Michaelides

et al. 2015

Phil. Trans. R. Soc. B

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The mechanisms underpinning the ecological impacts of the presence of artificial night lighting remain elusive. One suspected underlying cause is that the presence of light at night (LAN) supresses nocturnal production of melatonin, a key driver of biological rhythm and a potent antioxidant with a proposed role in immune function. Here, we briefly review the evidence for melatonin as the link between LAN and changes in behaviour and physiology. We then present preliminary data supporting the potential for melatonin to act as a recovery agent mitigating the negative effects of LAN in an invertebrate. Adult crickets ( Teleogryllus commodus ), exposed to constant illumination, were provided with dietary melatonin (concentrations: 0, 10 or 100 µg ml −1 ) in their drinking water. We then compared survival, lifetime fecundity and, over a 4-week period, immune function (haemocyte concentration, lysozyme-like and phenoloxidase (PO) activity). Melatonin supplementation was able only partially to mitigate the detrimental effects of LAN: it did not improve survival or fecundity or PO activity, but it had a largely dose-dependent positive effect on haemocyte concentration and lysozyme-like activity. We discuss the implications of these relationships, as well as the usefulness of invertebrates as model species for future studies that explore the effects of LAN.

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“…Melanization of hemolymph is a conserved immune response in insects and other arthropods (1,2). Melanin can seal off foreign organisms in the hemocoel and starve them of nutrients (3).…”

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confidence: 99%

“…Melanin can seal off foreign organisms in the hemocoel and starve them of nutrients (3). Melanin synthesis also results in production of reactive oxygen and nitrogen intermediates that are toxic to some microbes and multicellular parasites (1)(2)(3). PO 3 is thought to be the key enzyme required for hemolymph melanization.…”

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confidence: 99%

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Hemolymph Melanization in the Silkmoth Bombyx mori Involves Formation of a High Molecular Mass Complex That Metabolizes Tyrosine

Clark

Strand

2013

Journal of Biological Chemistry

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Background:The phenoloxidase (PO) cascade regulates the melanization of blood in insects and other arthropods. Results: Hemolymph from Bombyx mori rapidly melanizes after wounding and forms a complex that uses tyrosine as the substrate. Conclusion: Tyrosine usage requires formation of a phenoloxidase-containing complex. Significance: Processing of prophenoloxidase is an intermediate step in the phenoloxidase cascade.

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Phenoloxidases in Insect Immunity

Cited by 186 publications

References 199 publications

Functions of Manduca sexta Hemolymph Proteinases HP6 and HP8 in Two Innate Immune Pathways

Functions of Manduca sexta Hemolymph Proteinases HP6 and HP8 in Two Innate Immune Pathways

Melatonin: a possible link between the presence of artificial light at night and reductions in biological fitness

Hemolymph Melanization in the Silkmoth Bombyx mori Involves Formation of a High Molecular Mass Complex That Metabolizes Tyrosine

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